“A STUDY OF BRAINSTEM EVOKED RESPONSE AUDIOMETRY CHANGES IN NEONATES WITH UNCONJUGATED HYPERBILIRUBINEMIA BEFORE AND AFTER THERAPY” BY Dr. NAYANA NAYAK, M.B.B.S. Dissertation submitted to the Rajiv Gandhi University of Health Sciences, Karnataka, Bangalore In partial fulfillment of the requirements for the degree of DOCTOR OF MEDICINE IN PAEDIATRICS Under the Guidance of Dr. D. NARAYANAPPA M.D. Professor and Head, Department of Paediatrics JAGADGURU SRI SHIVARATHREESHWARA MEDICAL COLLEGE, SHIVARATHREESHWARA NAGAR, MYSORE- 570 015 APRIL - 2010 i ii iii iv v vi ACKNOWLEDGEMENT It gives me great pleasure in preparing this dissertation and I take this opportunity to thank everyone who has made this possible. First, I would like to extend my sincere thanks and appreciation towards all our patients for their willingness to cooperate with this study. My inexpressible gratitude to my mentor, Dr. D. Narayanappa, M.D., Professor and Head, Department of Paediatrics, J.S.S. Medical College, Mysore., for his constant encouragement and skillful guidance at each step of the preparation of this work. His enthusiasm, zeal for perfection and eagerness for exploring the depth of learning, helped me a lot to understand various aspects of the subject. It was only due to his constant inspiration, efforts and guidance that this study was made possible. My sincere regards to Dr. M. D. Ravi, M.D., DCH, Professor of Paediatrics, for his timely advice and guidance. I thank Dr. Jagadish Kumar, M.D., Professor, Department of Paediatrics, J.S.S.Medical College, who whole heartedly supported and helped me in the completion of this study. I thank Dr. N.P Nataraj, Director JSS institute of Speech and Hearing and his team members Ms.Shruti and Ms.Meryl, for their unconditional support. I wish to express my sincere thanks to Dr. Lancy D’ Souza for helping with Statistics. vii My sincere thanks to all my colleagues in the department for their understanding and extension of help. I also thank all the nursing, and technical staff of the institute who have helped with this study. I am grateful to Dr.Sandesh Prabhu, my husband, for having shown moral support throughout the study. I am grateful to my parents who are always a constant source of affection, moral support and encouragement. I am grateful to the Management, Principal, Medical Superintendent and all the office staff for permitting me to do this study and to use the facilities at the institute for the study. Place: Mysore Dr. Nayana Nayak Date: viii LIST OF ABBREVIATIONS AAP : American Academy of Paediatrics ABR : Auditory Brainstem Response BBB : Blood Brain Barrier BERA : Brainstem Evoked Response Audiometry BH2 : Bilirubin acid BIND : Bilirubin induced Neurological Dysfunction CB : Conjugated Bilirubin CBFV : Cerebral Blood Flow Velocity CHD : Congenital Heart Disease CNS : Central Nervous System CO : Carbon Monoxide CPD : Citrate Phosphate dextrose DCT : Direct Coomb’s test EDD : Expected date of Delivery ET : Exchange Transfusion ETCOc : End Tidal Carbon Monoxide Corrected for ambient-Co FFA : Free Fatty Acids G-6-PD : Glucose-6-Phosphate Dehydrogenase GVHD : Graft versus Host Disease HBABA : 2-4’ hydroxybenzene azo benzoic acid HDN : Hemolytic Disease of the Newborn IVH : Intra Ventricular Haemorrhage ix LFT : Liver Function Test LSCS : Lower Segment Caeserean Section MRI : Magnetic Resonance Imaging NEC : Necrotising Enterocolitis NICU : Neonatal Intensive Care Unit PBS : Peripheral Blood Smear PT : Phototherapy RBC : Red Blood Cell RES : Reticuloendothelial system TSB : Total Serum Bilirubin UCB : Unconjugated Bilirubin UDPG-T : Uridine Diphosphate Glucuronyl Transferase x ABSTRACT Neonatal hyperbilirubinemia is a common problem in the neonates which can cause significant morbidity and mortality. Auditory neuropathy is noted in one third to one half of infants with significant hyperbilirubinemia. Brainstem Evoked Response Audiometry (BERA) is an effective and non-invasive means of assessing the functional status of the auditory nerve and brainstem auditory sensory pathway. OBJECTIVES OF THE STUDY 1. To study the BERA changes in neonates with unconjugated hyperbilirubinemia. 2. To compare the BERA changes in the neonates with unconjugated hyperbilirubinemia before and after therapy. METHODOLOGY This study was conducted in the Department of Pediatrics of JSS Medical College, Mysore. The study period was between November 2007- May 2009. Thirty consecutive term AGA (Appropriate For Gestational Age) neonates presenting to the NICU of J.S.S. Hospital, with total serum bilirubin requiring intervention (using the American Academy of Pediatrics guidelines3) were included in the study as cases and thirty normal term AGA neonates with uneventful peri-natal period and a maximum measured serum bilirubin <12 mg/dl were included as controls after obtaining informed consent. Initial BERA was done within 3-24 hours of hospitalization. xi Repeat BERA was done in all cases after therapy , at the time of discharge and after a follow-up period of 3 months. RESULTS There were 34 cases and 30 controls in the study. Of the 34 cases, 28 cases came for follow up after a period of 3 months, whereas 6 were lost for follow up. In our study out of the 34 cases 12 (35.3 %) cases were found to have BERA changes. Raised threshold was the most common BERA change observed in majority of the patient 12(35.3%) cases, absent wave forms at 90 dBnHL was seen in 6(17.6%) cases. Prolonged latency I, III, V, prolonged inter peak latency I-III and I-V were seen in 8.8%, 14.7%, 14.7%, 17.6% and 11.8% of cases respectively. Prolonged inter peak III-V was not observed in any of the cases. Out of the 12 (35.3%) cases which had BERA changes at peak level of bilirubin, 9 (26.4%) cases had persistent changes at the time of discharge. Of these 9 cases, on follow up at 3 months 3 (8.8%) cases had persistent changes and 2 were lost for follow up. All these 3 cases had bilirubin > 25mg/dl before therapy. CONCLUSION BERA can be used as an effective and non invasive means of assessing the functional status of the auditory pathway in neonates with hyperbilirubinemia. Neonates with BERA changes need to be followed up over a period, an essential aim being the early identification of infants with impaired hearing so that rehabilitation can be initiated at a time when brain is still sensitive to the development of speech and language. Keywords: Hyperbilirubinemia, auditory neuropathy, BERA. xii xiii TABLE OF CONTENTS Chapters Page No. 1. INTRODUCTION 1 2. OBJECTIVES OF THE STUDY 3 3. REVIEW OF LITERATURE 4 4. METHODOLOGY 49 6. RESULTS 55 7. DISCUSSION 70 8. SUMMARY 75 9. CONCLUSION 77 10. BIBLIOGRAPHY 78 11. ANNEXURES i. PROFORMA ii. KEY TO 84 MASTER 89 CHART iii. MASTER CHART xiv 90 LIST OF TABLES Sl. No. 1 Title Page No. Management of hyperbilirubinemia in the healthy term new 27 born 2 Normal BERA parameter at 90dBnHL 55 3 Mean age (in days) of cases and controls 56 4 Sex wise distribuition of cases and controls 57 5 Average birth weight in kgs of cases and controls 58 6 Distribution of cases in different bilirubin range 59 7 Number of cases with BERA changes 60 8 Number of cases with different BERA changes at peak level 61 of bilirubin 9 Comparison of latencies of I,III,V of cases at peak level of 63 bilirubin, at discharge and follow-up at 90 dBnHL 10 Comparison of inter peak latencies of cases at peak level of 63 bilirubin, at discharge and follow-up at 90 dBnHL 11 Comparison of BERA changes at peak level of bilirubin, at 64 discharge and follow-up at 90 dBnHL 12 Correlation of bilirubin level with BERA changes 65 13 Type of treatment given to cases 66 14 Comparison of various BERA changes in different studies 71 15 Comparison of BERA changes at peak level at discharge and 72 follow-up with other studies xv LIST OF GRAPHS Sl.No. Title Page No. 1 Mean age (in days) of cases and controls 56 2 Sex wise distribuition of cases and controls 57 3 Average birth weight in kgs of cases and controls 58 4 Distribution of cases in different bilirubin range 59 5 Percentage of cases with BERA changes 60 6 Number of cases with different BERA changes at peak 62 level of bilirubin 7 Types of treatment given to cases xvi 66 LIST OF FIGURES Sl.No. Title Page No. 1 A Jaundiced baby under phototherapy 52 2 A Jaundiced baby undergoing BERA 52 3 A BERA report of a control showing normal BERA 67 waveforms 4 A BERA report showing absent waveforms at 90 dBnHL 67 5 A BERA report showing raised threshold i.e absent 68 waveform at 30dBnHL,but presence at 50dBnHL 6 A BERA report showing prolonged latency of 7.2 ms. 68 7 A BERA report showing prolonged interpeak interval I-V 69 of 5.4 ms xvii INTRODUCTION Neonatal jaundice is a common problem seen in the newborn. It is observed during the first week of life in approximately 60% of term and 80% of preterm2-6. Although most jaundiced newborns are otherwise healthy, they make the neonatologist anxious because bilirubin is potentially toxic to the central nervous system5. The terms bilirubin encephalopathy and kernicterus represent clinical and pathological abnormalities resulting from bilirubin toxicity in the central nervous system5. Besides other sequelae, unconjugated hyperbilirubinemia is found to be particularly toxic to the auditory pathway resulting in sensorineural hearing loss. Auditory neuropathy is noted in one third to one half of infants with significant hyperbilirubinemia5. Unbound bilirubin, because of its lipophilic nature can cross the blood brain barrier and exert toxicity at cellular level. Interruption of normal neurotransmission has been proposed to be one of the mechanisms of toxicity5. There is no level of bilirubin that definitely predicts kernicterus and also, the bilirubin levels that are toxic to one infant may not be toxic to another or even to the same infant in different clinical circumstances34, 35. The duration of exposure needed to produce toxic effects is also unknown. The imprecise relationship between total serum bilirubin and adverse neurological outcome has encouraged research, seeking more accurate markers of bilirubin toxicity. 1 Brainstem Evoked Response Audiometry (BERA) is an effective and noninvasive means of assessing the functional status of the auditory nerve and brainstem auditory sensory pathway51. It is not significantly altered by the state of consciousness, drugs and variety of environmental factors. The BERA changes in response to hyperbilirubinemia include loss of one or more peaks of waves I to V, raised threshold, increase in latency of waves I, III or V or increased inter peak interval51. BERA can detect subclinical bilirubin encephalopathy even before the appearance of any signs or symptoms of kernicterus. The present study was undertaken to evaluate the effect of hyperbilirubinemia in term newborns on Brainstem evoked response audiometry (BERA) and change, if any, in BERA after therapy. 2 OBJECTIVES OF THE STUDY 1. To study the BERA changes in neonates with unconjugated hyperbilirubinemia. 2. To compare the BERA changes in the neonates with unconjugated hyperbilirubinemia before and after therapy. 3 REVIEW OF LITERATURE • Neonatal hyperbilirubinemia is a common problem in the neonates which can cause significant morbidity and mortality. • The normal adult serum bilirubin level is less than 1mg/dL. Adults appear jaundiced when the serum bilirubin level is greater than 2mg/dL, and newborns appear jaundiced when it is greater than 7mg/dL and by adult standards, almost all newborn babies are jaundiced during early days of life2, 3. What constitutes significant hyperbilirubinemia is the subject of continuing controversy, as only limited information exists regarding the association between specific levels of TSB during non hemolytic hyperbilirubinemia in term newborns and subsequent adverse neurologic and cognitive outcome8-10. BILIRUBIN METABOLISM2, 3, 7, 12, 13 Source Bilirubin is derived from the breakdown of heme-containing proteins in the reticuloendothelial system. The normal newborn produces 6 to 10 mg of bilirubin per kg per day as opposed to the production of 3-4 mg per kg per day in the adult. 1. The major heme-containing protein is hemoglobin. Hemoglobin released from senescent RBCs in the reticuloendothelial system (RES) is the source of 75% of all bilirubin production. One gram of hemoglobin produces 34 mg of bilirubin. 4 2. The other 25% of bilirubin is called early labeled bilirubin. It is derived from hemoglobin released by ineffective erythropoiesis in the bone marrow, from other heme-containing proteins in tissues (eg. Myoglobin, cytochromes, catalase and peroxidase) and from free heme. Metabolism The heme ring from heme containing proteins is oxidised in reticuloendothelial cells to biliverdin by the microsomal enzyme heme oxygenase. This reaction releases carbon monoxide (CO) (excreted from the lung) and iron (reutilized). Biliverdin is then reduced to bilirubin by the enzyme bilirubin reductase. Catabolism of 1 mole of Hb produces 1 mole each of CO and bilirubin. Increased bilirubin production as measured by CO excretion rates, accounts for the higher bilirubin levels seen in Asian, Native American and Greek infants3. Transport Bilirubin is non polar and insoluble in water and is transported to liver cells bound reversibly but tightly to serum albumin. It is believed that the neurotoxicity associated with hyperbilirubinemia is primarily the result of unbound bilirubin, so the amount of bilirubin available for binding is important. Uptake Uptake of bilirubin from bilirubin-albumin complex occurs on the surface of liver parenchymal cells. Albumin bound bilirubin reaches the liver cell membrane where bilirubin is released from albumin. Bilirubin and not albumin is transferred across the cell membrane into the hepatocyte. The exact mechanism is not clear still. Several cytoplasmic proteins such as ligandin, lipoprotein, and fatty acid binding 5 protein may be involved. Bilirubin is primarily bound to ligandin within the cell and this binding prevents back flow into circulation. This bound intracellular bilirubin is transferred to smooth endoplasmic reticulum for conjugation. Conjugation Unconjugated/indirect bilirubin is converted to water soluble conjugated/direct bilirubin in the smooth endoplasmic reticulum by Uridine Diphosphate Glucuronyl Transferase (UDPG-T). In the first 48 hours of life, only bilirubin monoglucuronide is produced. After that, bilirubin diglucuronide is the main product. Both these products are water soluble and are secreted into biliary canaliculi and excreted into intestines as bile. This is an active energy dependent process as the conjugated bilirubin is excreted against a large concentration gradient. Excretion Conjugated bilirubin (CB) in the biliary tree enters GIT and is then eliminated from the body in stool, which contains large amounts of bilirubin. CB is not normally re absorbed from the bowel unless it is converted back to UCB by the intestinal enzyme beta-glucuronidase. The sterile intestine in the newborn is rich in βglucuronidase enzyme which splits bilirubin glucuronide into bilirubin and glucuronic acid. Then unconjugated bilirubin (UCB) is reabsorbed and returned to circulation. It has to be exported once again to liver for conjugation and excretion. This re absorption of bilirubin from the gastrointestinal tract and delivery back to the liver for reconjugation is called “entero hepatic circulation”. Conjugated bilirubin is converted into urobilinogen / urobilinoids by bacterial action of the gut and this prevents enterohepatic circulation as urobilinoids are not 6 substrates for β-glucuronidase. A part of urobilinogen is absorbed into portal circulation and is mostly re-excreted by liver as bilirubin. A part of it reaches systemic circulation and is excreted through kidneys. Fetal bilirubin metabolism3 The UCB formed by the fetus is cleared by the placenta into the maternal circulation. Formation of CB is limited in the fetus because of decreased hepatic blood flow, hepatic ligandin and UDPG-T activity. The small amount of CB excreted into the fetal gut is usually hydrolysed by beta glucuronidase and re absorbed. Bilirubin is normally found in amniotic fluid by 12 weeks and is gone by 37 weeks gestation. Increased amniotic fluid bilirubin is found in hemolytic disease of newborn and in fetal intestinal obstruction below the bile ducts. BILIRUBIN TURNOVER IN NEWBORN2, 3, 12 Several biophysiological handicaps lead to increase in frequency and severity of jaundice among newborn babies. • Physiologic polycythemia and shorter life span of fetal red blood cells result in release of 0.15 gm/Kg of hemoglobin every day because 1.0 ml/kg (≅1%) of blood hemolyse everyday. 1gram of hemoglobin yields about 34 mg of bilirubin, so that in a 3kg infant, about 15 mg of bilirubin is produced daily from hemoglobin sources i.e., 5mg/kg of bilirubin is generated. Additional 1mg/kg bilirubin is produced from non-hemoglobin sources, thus resulting in net daily load of 18mg of bilirubin to the liver in a healthy term infant. 7 • Hepatic uptake, conjugation and excretion of bilirubin are limited due to transient deficiency of Y and Z acceptor proteins and UDPG-T enzyme in newborn babies. Because of relative lack of hepatic conjugatory enzymes, hyperbilirubinemia is mostly limited to unconjugated fraction of bilirubin during early days of life. On an average, 100-200 mg of bilirubin is present in the gut in a concentration of 1.0 mg of bilirubin per gram of meconium. • Due to paucity of bacterial flora in the gut of a newborn baby and over activity of intestinal β-glucuronidase enzyme, the conjugated bilirubin entering the duodenum is rapidly deconjugated and recirculated in the blood and delivered to the liver for reconjugation through enterohepatic circulation. Thus, increased production of bilirubin, reduced hepatic clearance, enhanced enterohepatic circulation contribute to increased prevalence of jaundice among newborn babies. The rate of bilirubin production (6-8 mg/kg/24 hrs) is at least twice in magnitude in the normal newborn population as compared to older children. CAUSES OF JAUNDICE ON THE BASIS OF AGE OF ONSET1, 2, 3, 13 A. Within 24 hours of birth 1. Hemolytic disease of the newborn due to feto-maternal blood group incompatibility in the rhesus, ABO and minor blood group systems, 2. Intrauterine infections such as, toxoplasmosis, cytomegalic inclusion disease, syphilis, rubella, herpes simplex, bacterial infections, 8 3. Deficiency of red cell enzymes such as G-6-PD, pyruvate kinase, hexokinase, phosphoglucose isomerase, and unstable Hb, 4. Administration of large amount of certain drugs such as vitamin-K, salicylates, sulfisoxazole etc. to the mother, 5. Hereditary spherocytosis, 6. Crigler-Najjar syndrome, 7. Lucey-Driscoll syndrome, 8. Homozygous alpha-thalassemia. B. Between 24-72 hours of age Physiological jaundice appears during this period but can be aggravated and prolonged by immaturity, birth asphyxia, acidosis, hypothermia, hypoglycemia, drugs, cephalhematoma, concealed hemorrhage and bruising, polycythemia, high altitude, cretinism, infections and mild hemolytic states due to fetomaternal blood group incompatability, spherocytosis and deficiency of red cell enzymes. C. After 72 hours of age (and within first 2 weeks) 1. Septicemia 2. Neonatal hepatitis including other causes of intrauterine infections. 3. Extrahepatic biliary atresia. 4. Breast milk jaundice 5. Metabolic disease such as galactosemia, tyrosinemia, hereditary fructosemia, organic acidemia, cystic fibrosis, α-1-antitrypsin deficiency. 6. Hypertrophic pyloric stenosis and intestinal obstruction. 9 Intrauterine infections should be considered in the differential diagnosis of jaundice having onset any time during the neonatal period. The age of onset of jaundice gives an important clue to the possible etiology. The common causes of jaundice in our country in order of their frequency include2: • Physiological jaundice • Immaturity • Blood group incompatibility between mother and fetus • Intrauterine and postnatal infections. • G-6-PD deficiency • Subcutaneous bruising and cephalohematoma • Drugs • Breast milk jaundice Even after detailed investigations, the cause of neonatal hyperbilirubinemia remains uncertain in over 1/3rd of cases2, 6. CLINICAL ASSESSMENT OF SEVERITY OF JAUNDICE 2 Clinical judgment utilizes the principle that clinical jaundice first becomes obvious in the face followed by a downward progression as it increases in intensity (cephalo pedal progression) 2. Assessment of jaundice is done in natural light and there should be no yellow clothes or curtains in the background which can lead to an error of over estimation. Yellow discoloration is first evident on the skin of face, naso labial folds and tip of the nose. It is masked by physiological plethora of newborn. The pulp of finger or 10 thumb is pressed on the baby’s skin, preferably over a bony part, till it blanches. The underlying skin is noted for yellow colour2. 11 Extent of jaundice thus detected gives a rough estimate of serum bilirubin1, 7, 13. Area of body Range of bilirubin (mg/100ml) Face 4-8 Upper trunk 5-12 Lower trunk and thighs 8-16 Arms and lower legs 11-18 Palms and soles >15 Criteria to estimate clinical jaundice The yellow staining of sclera is difficult to evaluate because of physiological photophobia. Eyes and sclera are best examined by holding the infant against diffuse light and without trying to forcibly open the eyelids. The cephalo pedal progression is apparently related to the relative thickness of skin at various parts, skin being thinnest in the face and extremely thick over the palms and soles. Cephalo pedal color difference may be related to differences in blood flow or lipid content of skin and due to conformational changes in the newly formed bilirubin albumin complexes2. There is no difficulty in clinically recognizing jaundice among Indian babies because increased skin pigmentation generally appears after 2 weeks of age2. It is essential that all newborn babies must be clinically screened twice a day in good day light to detect the onset and severity of jaundice. 12 PHYSIOLOGICAL JAUNDICE 60% of term and 70% of preterm babies develop visible jaundice due to elevation of unconjugated bilirubin during their first week. This common condition is called ‘Physiological Jaundice’2, 3, 12, 13. It may provide useful protection to the baby against oxygen free radical triggered neonatal disorders, because bilirubin is an antioxidant2, 6, 14, 15. The pattern of hyperbilirubinemia has been classified into two functionally distinct periods13: Phase one: Lasts for 5 days in term infants and about 7 days in preterm infants, when there is a rapid rise in serum bilirubin levels to 12 to 15 mg/dL respectively. Phase two: There is decline in Total Serum Bilirubin (TSB) level to about 2mg/dL, which lasts for 2 weeks after which adult values are attained. Levels under 2mg/dL may not be seen until 1 month or more than a month in preterm infants and full term infants on exclusive breast feeding. Term babies: Jaundice appears between 30-72 hours of age. Maximum intensity is seen on 4th day. (Serum bilirubin does not exceed 15mg/dL) and disappears by 10 days of life13. Preterm babies: Jaundice appears earlier but not before 24 hours of age. Maximum intensity is seen on 5th or 6th day (serum bilirubin may go up to 15 mg/dL) and may persist upto 14 days13. 13 Etiology of physiological jaundice appears to be multifactorial. Possible mechanisms involved in physiological jaundice1,2,3,13 1. Increased bilirubin load on liver cells ¾ Increased erythrocyte volume / kg body weight (polycythemia) ¾ Increased early labeled bilirubin, increased ineffective erythropoiesis and increased turnover of non Hb heme proteins. ¾ Increased enterohepatic circulation of bilirubin. Caused by : a. High levels of intestinal β-glucuronidase. b. Decreased intestinal bacteria. c. Decreased gut motility with poor evacuation of bilirubin laden meconium. ¾ Decreased erythrocyte survival / shorter life span (90 days Vs. 120 days in adults). 2. Defective hepatic uptake of bilirubin from plasma ¾ Decreased ligandin (Y protein) in hepatocytes. ¾ Increased binding of Y protein by other anions. 3. Defective bilirubin conjugation ¾ Decreased UDPG activity. 4. Defective hepatic bilirubin excretion PATHOLOGICAL JAUNDICE2, 3, 13 Definition Presence of any of the following features characterizes pathological jaundice: 1. Onset of jaundice before 24 hours of age 2. Increase in level of total bilirubin by more than 0.5 mg/dL/hr or 5mg/dL /24hrs. 14 3. Total bilirubin >12mg/dL in full term and > 10-14 mg/dL in preterm. 4. Direct bilirubin >2.0 mg/dL 5. Signs of underlying illness in any infant (vomiting, lethargy, poor feeding, excessive weight loss, apnea, tachypnea, temperature instability). 6. Jaundice persisting after 10 days in a term infant or after 14 days in a preterm infant. DANGERS OF HYPERBILIRUBINEMIA KERNICTERUS OR BILIRUBIN ENCEPHALOPATHY It is a neurologic syndrome resulting from the deposition of unconjugated bilirubin in the basal ganglia and brainstem nuclei3. The word kernicterus originated as a description of yellow nuclear staining of the brain, but has become synonymous with the acute and chronic bilirubin encephalopathy1, 2. The pathogenesis of kernicterus is multifactorial and involves an interaction between1, 2, 3 1. Unconjugated bilirubin levels and factors that affect its level. 2. Albumin binding and unbound bilirubin levels. 3. Passage across the blood brain barrier and 4. Neuronal susceptibility to injury. Factors that influence bilirubin toxicity to the brain cells of newborn are complex and incompletely understood1, 2, 12. 15 PATHOGENESIS Uncertainty remains regarding the exact mechanism of neurotoxicity observed in association with hyperbilirubinemia1, 2. For bilirubin to exert its toxic effect on the central nervous system (CNS), it has to get into the brain. Albumin bound bilirubin is unable to cross intact blood brain barrier (BBB). Once bilirubin sites on albumin are saturated, free bilirubin appears in the serum and it is this free bilirubin that crosses the blood brain barrier and produce brain damage1, 2, 7. In cases of existing insult to BBB, even albumin bound bilirubin can get access to CNS. The ‘FREE BILIRUBIN THEORY’1 states that the risk of bilirubin neurotoxicity increases with increasing non-albumin-bound bilirubin concentration, which is a function of both albumin concentration and total bilirubin concentration, increasing as the bilirubin to albumin ratio increases. Albumin has 2 binding sites for bilirubin.1, 2 a) Primary/firm binding site/high affinity site which binds bilirubin in the molar ratio of 1:1. b) Secondary/loose binding site/low affinity sites, probably 2 on each albumin molecule, bringing bilirubin to albumin molar ratio to 3:1. One gram of albumin binds to 8.5mg of bilirubin2, 7. Free fatty acids (FFA), hematin, low pH and drugs that compete for the binding sites in albumin can easily displace bilirubin from these sites1. 16 The saturation of albumin with unbound bilirubin can be measured by bilirubin binding capacity and it helps to predict neurotoxicity in susceptible neonates1. Anoxia, hypercarbia and hyperosmolarity increase the permeability of BBB and increase deposition of bilirubin in the brain. Respiratory acidosis also increase bilirubin brain deposition1, 2, 16. Because of low solubility, bilirubin aggregates in the tissues and binds opportunistically to membranes or membrane components on the cells1. Once in contact with neurons, further damage to neurons depends on availability of Hydrogen ion. Bilirubin normally exists as a bi-anion and combines with H+ ion to form bilirubin acid (BH2) which precipitates on to neurons producing damage. Other theory states that bilirubin combines with one H+ ion and this molecule positions itself between lipid bilayer of the membranes. This moiety has surfactant like property and changes membrane function of ion channel producing early manifestation of encephalopathy7, 17. BILIRUBIN TOXICITY AT CELLULAR LEVEL Four possible mechanism have been proposed 1. Interruption of neurotransmission By binding to the nerve terminals, it causes a reversible lowering of membrane potential and a decrease in nerve conduction12, thus explaining the reversibility of early bilirubin encephalopathy1. At higher concentration, the nerve terminals are severely injured and bilirubin penetrates the axons with retrograde uptake into the cell 17 body and also, if acidosis persists, then BH2 is formed resulting in permanent neuronal damage6. 18 2. Mitochondrial dysfunction Some researchers have hypothesized that bilirubin acid precipitates in phospolipid membranes resulting in mitochondrial dysfunction 3. Cellular or intracellular membrane impairment This is due to bilirubin forming reversible complexes with various cellular membranes. 4. Interference with enzyme activity This theory holds that bilirubin acid is capable of binding receptor sites on specific enzymes, rendering them inoperative or at least severely diminishing their activities. The precise blood level above which indirect-reacting bilirubin or free bilirubin will be toxic for an individual infant is unpredictable. The duration of exposure needed to produce toxic effects is also unknown. 19 PATHOLOGY Kernicterus is a pathological diagnosis and refers to yellow staining of the brain by bilirubin together with the evidence of neuronal injury. Grossly, bilirubin staining is most commonly seen in basal ganglia, various cranial nerve nuclei, other brainstem nuclei - inferior olivary nuclei, dentate nucleus subthalamic nuclei, nuclei of the floor of 4th ventricle, cerebellar nuclei, hippocampus and anterior horn cells of spinal cord1, 2, 3. The classical neurological signs are not seen among preterm infants, as bilirubin staining among them is limited to nuclei of cranial nerves subthalamus and thalamus2. Microscopically there is necrosis, neuronal loss and gliosis. Loss of neurons, reactive gliosis, and atrophy of involved fiber systems are found in late disease2. CLINICAL BILIRUBIN ENCEPHALOPATHY OR CLINICAL FEATURES1-4, 20 Signs and symptoms of kernicterus usually appear 2-5 days after birth in term infants and as late as 7th day in premature ones, but hyperbilirubinemia may lead to the syndrome at any time during the neonatal period. The early signs may be subtle and indistinguishable from those of sepsis, asphyxia, hypoglycemia, intracranial hemorrhage and other acute systemic illnesses in a neonatal infant. 20 Acute form Three clinical phases have been identified in acute bilirubin encephalopathy, classically seen in term infants1-4, 20. Phase 1: (1st 1-2 days): Poor sucking, stupor, lethargy, vomiting high pitched cry, decreased tone, and poor Moro’s reflex. Phase 2: (middle of 1st week): Hypertonia of extensor muscles → rigidity, opisthotonus, retrocollis, oculogyric crisis, fever, seizures, and paralysis of upward gaze. Most infants die in this phase. Those infants, who survive, develop chronic bilirubin encephalopathy. Phase 3: (after the 1st week): Infant demonstrates hypertonia with marked retrocollis and opisthotonos , stupor or coma and a shrill cry. Many infants who progress to phase 2 die; the survivors are usually seriously damaged but may appear to recover and for 2-3mo show few abnormalities. Later in the 1st year of life, opisthotonus, muscle rigidity, irregular movements and convulsions tend to recur. In the 2nd year, the opisthotonus and seizures abate, but irregular, involuntary movements, muscle rigidity or in some infants, hypotonia increase steadily. By 3rd year of age, the complete neurologic syndrome is often apparent and consists of bilateral choreoathetosis with involuntary muscle spasms, extrapyramidal 21 signs, seizures, mental deficiency, dysarthric speech, high-frequency hearing loss, squinting and defective upward movement of eyes. Pyramidal signs, hypotonia and ataxia occur in a few infants1, 2, 19. In mildly affected infants, the syndrome may be characterized only by mild to moderate neuromuscular incoordination, partial deafness, or “minimal brain dysfunction”, occurring singly or in combination; these problems may not be apparent until the child enters school1, 2. PREDICTORS OF BILIRUBIN TOXICITY 1, 2, 21 The imprecise relationship between total serum bilirubin and adverse neurological outcome has encouraged research seeking more accurate markers of bilirubin toxicity. Assessment of free bilirubin, bilirubin-binding capacity, bilirubin to albumin ratio, brainstem auditory evoked responses, magnetic resonance imaging of brain and computer analysis of abnormality of jaundiced infant’s cry have been proposed: Total Serum Bilirubin The precise blood level above which indirect reacting or free bilirubin will be toxic for an individual infant is unpredictable1, 2, 3, 34. As of now, there is no level of bilirubin that definitely predicts kernicterus and also, the bilirubin levels that are toxic to one infant may not be toxic to another or even to the same infant in different clinical circumstances34, 35. Bilirubin levels refer to total bilirubin. Direct bilirubin is not subtracted from the total unless it constitutes more than 50% of total bilirubin. Currently major debate 22 surrounds the toxicity of bilirubin in otherwise healthy-term infants22-33. The AAP recommends, that in term babies with non-hemolytic jaundice, serum bilirubin level of 25-29mg/dL are safe and do not require exchange transfusion11. But Indian studies suggest that kernicterus could occur in babies even when the serum bilirubin is < 25mg/dL34, 35. Reserve Bilirubin Binding Capacity And Free Bilirubin2, 19 Î HBABA dye binding measures both reserve albumin binding capacity for bilirubin and non-bilirubin binding sites on albumin. HBABA dye binding capacity of <50% may be associated with bilirubin brain damage. Î SALICYLATE SATURATION INDEX – determines the extent to which albumin is saturated with bilirubin by assessing its displacement on addition of salicylate in vitro. Salicylate saturation index of 8 or more is associated with bilirubin encephalopathy. Î SEPHADEX G-25 measures both free and loosely bound bilirubin to albumin. Sephadex column consists of tiny beads of hydrated polymeric material packed into a tube and it actively absorbs both free and loosely bound bilirubin. The baby is not at risk to develop kernicterus if sephadex G-25 column is not yellow stained and level of free and loosely bound bilirubin is less than 0.1mg/dL. Î Red blood cell binding of bilirubin has also been utilized to assess the risk of kernicterus. 23 Whenever bilirubin bound to RBC, exceed 4mg/dL, it is considered as unsafe. Î A front face reflectance fluorometry or semi-automated technique for rapid determination of albumin bound bilirubin, total bilirubin and reserve binding capacity on a drop of blood has been evolved. Bilirubin Protein Ratio Adequate levels of serum protein are essential for effective binding of bilirubin to prevent leakage into the interstitial tissue and intracellular compartment. Bilirubin protein ratio of 3.5 or more may be associated with developmental sequelae of bilirubin encephalopathy2. The level of serum albumin may not provide a true estimate of the available bilirubin binding capacity because binding sites in the albumin may also be blocked by H+ ions and other organic anions such as salicylates, sulfonamides, FFA, hematin, furosemide, sodium benzoate, indomethacin and certain antibiotics. In presence of these anions, the bilirubin binding capacity is compromised and brain damage may develop at lower serum bilirubin levels even in the presence of normal serum protein concentration2. Brainstem Evoked Response Audiometry (BERA) The auditory pathway of the newborn is particularly vulnerable to insult from bilirubin. Increased bilirubin concentrations have been correlated with changes in amplitude and latency of BERA. BERA testing is accurate and non invasive and assesses the functional status of the auditory nerve in the brainstem auditory 24 pathway1. This test could be used to screen hearing loss due to hyperbilirubinemia and to predict need for exchange transfusion in jaundiced neonates. Infant Cry Analysis Analysis of characteristics of infant’s crying have shown that moderate elevation in TSB could alter the neural conduction and have impact on the vocal cords (increased tension or phonation) 1. Magnetic Resonance Imaging (MRI) MRI has been proposed as a rapid non invasive measurement of impending or actual brain cell injury during periods of hyperbilirubinemia. Diffusion weighted images may enable the diagnosis of reversible brain injury in sufficient time to intervene and to determine what is irreversible for timely prognostication1. After extreme hyperbilirubinemia, specific symmetric abnormalities are known to occur in patients that are seen in autopsied kernicterus babies32. MANAGEMENT OF HYPERBILIRUBINEMIA IN THE HEALTHY TERM NEWBORN2-4, 9 Under certain circumstances, bilirubin may be toxic to the CNS and may cause neurologic impairment even in healthy term newborns. Most studies, however, have failed to substantiate significant associations between a specific level of total serum bilirubin (TSB) during non hemolytic hyperbilirubinemia in term newborns and subsequent IQ or serious neurologic abnormality (including hearing impairment). Other studies have detected subtle differences in outcomes associated with TSB levels, particularly when used in conjunction with albumin binding test, and/or duration of exposure. 25 Continuing uncertainties about the relationship between serum bilirubin levels and brain damage as well as differences in patient populations and practice settings contribute to variations in the management of hyperbilirubinemia. Early postpartum discharge from the hospital further complicates the management of jaundiced newborns, because it places additional responsibilities on parents or guardians to recognize and respond to developing jaundice or clinical symptoms. MANAGEMENT OF HYPERBILIRUBINEMIA – AAP RECOMMENDATIONS 2-4, 13 The following recommendations were developed by the AAP to aid in the evaluation and treatment of the healthy term infant with hyperbilirubinemia. Important in the development of these guidelines is the general belief that therapeutic interventions for hyperbilirubinemia in the healthy term infant may carry significant risk relative to the uncertain risk of hyperbilirubinemia in this population. Evaluation 1. Maternal prenatal testing should include ABO + Rh (D) typing and a serum for unusual iso immune antibodies. 2. A direct Coomb’s test, a blood type, and an Rh (D) type on the infant’s (Cord) blood are recommended when the mother has not had prenatal blood grouping or is Rh-negative. 3. Institutions are encouraged to save cord blood for future testing, particularly when the mother’s blood group is O. Appropriate testing may then be performed as needed. 4. When family history, ethnic or geographic origin, or the timing of the appearance of jaundice suggests the possibility of G-6-D deficiency or some other cause of 26 hemolytic disease, appropriate laboratory assessment of the infant should be performed. 5. A TSB level needs to be determined in infants noted to be jaundiced in the first 24 hours of life. 6. In newborn infants, jaundice can be detected by blanching the skin with digital pressure, revealing the underlying color of the skin and subcutaneous tissue. The clinical assessment of jaundice must be done in a well-lighted room. Dermal icterus is seen first in the face and progresses caudally to the trunk and extremities. As the TSB level rises, the extent of cephalocaudal progression may be helpful in quantifying the degree of jaundice. Use of an icterometer or transcutaneous bilirubinometer may also be helpful. 7. Evaluation of newborn infants who develop abnormal signs such as feeding difficulty, behaviour changes, and apnea or temperature instability is recommended – regardless of whether jaundice has been detected – to rule out underlying illness. Factors to be considered when assessing a jaundiced infant 1. Factors that suggest the possibility of hemolytic disease • Family history of significant hemolytic disease • Onset of jaundice before age 24 hours. • A rise in serum bilirubin levels of more than 0.5mg/dL/hr • Pallor, hepato splenomegaly • Rapid increase in the TSB level after 24-48 hours (consider G-6-PD deficiency) • Ethnicity suggestive of inherited disease (G-6-PD deficiency etc.) • Failure of phototherapy to lower the TSB level 27 2. Clinical signs suggesting the possibility of other diseases such as sepsis or galactosemia in which jaundice may be one manifestation of the disease. • Vomiting • Lethargy • Poor-feeding • Hepatosplenomegaly • Excessive weight loss • Apnea • Temperature instability • Tachypnea 3. Signs of cholestatic jaundice suggesting the need to rule out biliary atresia or other causes of cholestasis • Dark urine or urine positive for bilirubin • High colored stools • Persistent jaundice > 3 week 4. Follow up should be provided to all neonates discharged less than 48 hours after birth by a health care professional within 2 to 3 days of discharge. 5. Approximately 1/3rd of healthy breast-fed infants, have persistent jaundice after 2 weeks of age. A report of dark urine or light stools should prompt a measurement of direct serum bilirubin. If the history (particularly the appearance of urine and stool) and physical examination results are normal, continued observation is appropriate. If jaundice persists beyond 3 weeks, a urine sample should be tested for bilirubin and a measurement of total and direct serum bilirubin obtained. 28 TREATMENT Table 1. Management of hyperbilirubinemia in the healthy term new born3, 4, 7, 11 *TSB level, mg/dL (μmol / L) Exchange Age Exchange transfusion if Consider hours transfusion and Phototherapy intensive phototherapy phototherapy † intensive fails ‡ phototherapy ≤ 24§ - - - - 25-48 ≥ 12 (170) ≥15 (260) ≥20 (340) ≥25 (430) 49-72 ≥ 15(260) ≥ 18 (310) ≥ 25(43) ≥ 30 (510) > 72 ≥ 17 (290) ≥ 20 (340) ≥ 25 (430) ≥30 (510) *TSB indicates total serum bilirubin †Phototherapy at these TSB levels is a clinical option, meaning that the intervention is available and may be used on the basis of individual clinical judgment. ‡Intensive phototherapy should produce a decline of TSB of 1 to 2 mg/dL within 4 to 6 hours and the TSB level should continue to fall and remain below the threshold level for exchange transfusion. If this does not occur, it is considered a failure of phototherapy. §Term infants who are clinically jaundiced at ≤ 24 hours old are not considered healthy and require further evaluation. 29 PHOTOTHERAPY (PT) Phototherapy is by far the most widely used treatment for hyperbilirubinemia, and it is both safe and effective. Phototherapy has been found to be effective in treating hyperbilirubinemia in hemolytic as well as in non-hemolytic settings. It has dramatically reduced the need for exchange transfusion2, 3, 7, 12. Factors that determine dose of phototherapy 12 • Spectrum of light emitted • Irradiance of light source • Design of phototherapy unit • Surface area of infant exposed to the light • Distance of infant from light source Light Spectrum 2, 3, 12, 13 Unconjugated bilirubin in skin gets converted into water-soluble photoproducts on exposure to light of a particular wavelength (425-475 nm). These photoproducts are water soluble, nontoxic and excreted in intestine and urine. For phototherapy to be effective, bilirubin needs to be present in skin so there is no role for prophylactic phototherapy7. Although bilirubin absorbs visible light with wavelength, about 400 to 500 nm, the most effective lights for phototherapy are those with high-energy output near the maximum adsorption peak of bilirubin (450 to 460 nm). Special blue lamps with a peak output at 425 to 475 nm are the most efficient for phototherapy. 30 MECHANISM OF ACTION Photochemical reactions or mechanisms that lower serum bilirubin levels2, 3, 7, 12, 13 When bilirubin adsorbs light, 3 types of photochemical reactions occur: 1. Photoisomerisation / configurational isomerisation - Occurs in the extravascular space of the skin. - The natural isomers of unconjugated bilirubin (4Z, 15Z) are instantaneously converted to a less toxic more polar water soluble diazo-negative compounds – E isomers (4Z15E, 4E15E, 4E15Z), that diffuse into the blood and are excreted into the bile without conjugation. However, excretion is slow, and configurational isomers are not very stable and they revert back to Z-isomers, which is re absorbed from the gut if the baby is not passing stools. Therefore, it is not a major mechanism for decrease in TSB. After about 12 hours of phototherapy, the photo isomers make up for about 20% of total bilirubin which is nontoxic. Standard tests do not distinguish between naturally occuring bilirubin and the photoisomer, so bilirubin levels may not change much even though the phototherapy has made the bilirubin present less toxic. 2. Structural Isomerisation It is the intramolecular cyclization of bilirubin to stable water soluble isomer – LUMIRUBIN. Lumirubin makes upto 2-6% of serum concentration of bilirubin 31 during phototherapy and is rapidly excreted in the bile and urine, without conjugation. Unlike photoisomerisation, the conversion of bilirubin to lumirubin is irreversible and it cannot be reabsorbed. It is the most important pathway for phototherapy induced decline in serum bilirubin level and is strongly related to the dose of phototherapy used in the range of 6-12 μw/cm2/nm. 3. Photo-oxidation This slow process converts bilirubin to small polar water soluble colorless products that are excreted in urine. It is the least important reaction for reducing serum bilirubin. Phototherapy used for treating jaundice is like giving a drug. One is not justified in using substandard light sources for treatment of neonatal jaundice. So it is imperative that irradiance of phototherapy units must be checked periodically. The infant is exposed under a portable or fixed light source kept at a distance of about 45 cm from the skin2, 13. The distance between the baby and phototherapy unit can be reduced to 15-20 cm to provide more effective or intensive phototherapy2. Simple measures like lining the bassinet with white linen and putting a white curtain around the phototherapy unit and bassinet have found to increase the efficiency of phototherapy unit by several folds by reflecting light on to the baby’s skin 11, 38 . During exposure to light, the eyes must be effectively shielded to prevent retinal damage and a diaper may be kept on to cover the genitals. During phototherapy, infant’s position should be changed off and on (every 2 hours) so that maximal areas of skin are exposed to light2. 32 For effective phototherapy, it is desirable that minimum spectral irradiance or ‘flux’ of 4-6 μw/cm2/nm is available and maintained at the level of infant’s skin2. The flux must be checked after every 100-200 hours of use to ensure that phototherapy lamps are effective2. Double surface phototherapy is more effective than the single surface because the average irradiance of the former is greater. Double surface phototherapy can be provided either by double surface special blue lights or by conventional blue light and undersurface fiberoptic phototherapy. This is a convenient way of delivering double phototherapy when it is necessary to reduce the bilirubin level as rapidly as possible7. Intensive PT should produce a decline in TSB of 1-2 mg/dL within 4-6 hours1, 7. Intermittent versus continuous phototherapy11, 12 Clinical studies comparing these two methods have shown conflicting results. If bilirubin levels are very high, intensive phototherapy should be administered continuously until a satisfactory decline in the TSB level has occurred. On the other hand, in most circumstances, phototherapy does not need to be continuous and it should certainly be interrupted during feeding or parental visits. Hydration11, 12 Because some of the lumirubin produced during phototherapy is excreted in urine, maintaining adequate hydration and a good urine output does help to improve the efficacy of phototherapy. 33 When to stop phototherapy11 A recent study found that, in infants who do not have hemolytic disease, the average bilirubin rebound after phototherapy is less than 1mg/dL. Phototherapy may be discontinued when the TSB level falls below 14 to 15 mg/dL. Discharge from the hospital need not be delayed in order to observe the infant for rebound and, in most cases, no further measurement of bilirubin is necessary. Biological effects7, 10 Phototherapy is in use since last 50 years and has shown excellent track of safety. There are more than 50 published controlled trials confirming the efficacy of phototherapy7. Recently, the effect of phototherapy on cerebral blood flow velocity (CBFV) has been reported. Phototherapy increased mean CBFV in all preterm infants, which returned to pre-therapy values after discontinuation of phototherapy only in nonventilated babies. Even in term babies, phototherapy increased CBFV, which returned to pre-therapy level upon discontinuation of PT. PT has been shown to affect shortterm behavior of the term infant, which has been attributed to maternal separation39. So mother should be encouraged to breast-feed and interact with her baby regularly. In addition, phototherapy influences cytokine production by peripheral mononuclear blood cells. Phototherapy has also photo-oxidative effects on intravenous lipids, proteins and drugs like amphotericin B12. 34 Side effects2, 3, 12, 13 1. Insensible water loss is increased in infants undergoing phototherapy – leads to hyperthermia, irritability and dehydration. 2. Passage of loose green stools and increased fecal water loss because of transient lactose intolerance and irritant effect of photo-catabolites, increased bile salts and unconjugated bilirubin in the bowel causes increased colonic secretory losses. 3. Increased risk of opening up of ductus arteriosus in preterm babies. 4. Hypocalcemia may occur due to secretion of melatonin from pineal gland – Melatonin inhibits the action of cortisol, which causes Ca2+ uptake by bone. 5. Retinal damage has been described in animals. The eyes should be shielded with eye patches. 6. Tanning of the skin of black infants. Erythema and increased skin blood flow may be seen. Some infants may develop flea bite rash on trunk or extremities. 7. Infants with parenchymal liver disease with biliary obstruction may develop peculiar bronze discoloration of skin – ‘BRONZE BABY’ SYNDROME – due to excessive accumulation of one of the photoisomers designated as lumirubin which is retained and polymerised to bilifuscin imparting brownish discolouration to the skin. Therefore phototherapy is usually contraindicated in infants with direct hyperbilirubinemia. If both direct and indirect bilirubin are high, exchange transfusion is probably safer than phototherapy because it is not known whether the bronze pigment is toxic. 35 8. Mutations, sister chromatid exchange and DNA strand breaks have been described in cell culture. Paradoxically, it has been shown that intermittent phototherapy causes more damage to intracellular DNA as compared to continuous exposure to light. 9. There is theoretical increased risk of developing malignancy of skin. 10. There is experimental evidence to suggest that exposure to light may disturb the circadian rhythm of the sex hormones thus having potential implications regarding onset of puberty and disturbances in future sex behaviour. 11. Photo-oxidant damage to RBCs may cause hemolysis. 12. Platelet turnover may be increased resulting in lower mean platelet counts but bleeding does not occur. • Body weight and serum osmolality should be monitored. • Infants under phototherapy should receive additional feeds and fluid (2040 ml/kg/24 hrs) to safeguard against dehydration and haemoconcentration. • Term babies should be breast fed every 2nd hourly. • During exposure to light, infant skin gets, bleached and clinical evaluation of severity of jaundice becomes unreliable in babies receiving phototherapy and thus serum bilirubin levels should be monitored every 68 hrs. 36 • Hct or Hb checked after every 48 hrs, because there is a greater need for “top-up” blood transfusion since antibodies continue to cause hemolysis. Sunlight is relatively ineffective because of low blue content of light. Besides, hyperpyrexia and skin burns can occur in prolonged sunlight exposure. More data is needed for recommendations for exposure to sunlight regarding duration of exposure, time of the day and potential hazards7. EXCHANGE BLOOD TRANSFUSION2, 21 It is the most effective and reliable method to reduce bilirubin levels. It removes much of the circulating bilirubin and sensitized red cells, replacing them with red cells compatible with mother’s antibody rich serum and providing fresh albumin with binding sites for bilirubin. Choice of blood2, 9, 21 Rh iso-immunisation : In emergency situation O Rh negative cells is used. Ideal is to use O Rh Negative blood suspended in AB plasma. Cross matched Baby’s blood group but Rh negative can also be used. ABO incompatibility: Blood group O types (Rh compatible) compatible with baby. Ideal is to use blood group O (Rh compatible) suspended in AB plasma. Other situations: Cross-matched baby’s blood group. Fresh citrate phosphate dextrose blood (not>3 days old) or heparinised blood can be used for the procedure. 37 An effective exchange is achieved by performing the procedure with double the blood volume of baby that is about 170 ml/kg. A double volume exchange transfusion removes about 85% of the infant’s RBCs, but because most of the infant’s bilirubin is in the extra-vascular compartment only 25% of the total body bilirubin is removed. Post-exchange levels are about 60% of pre-exchange levels, and the reequilibration that occurs between the vascular and extra-vascular bilirubin compartments produces a rapid rebound (within 30min) of serum bilirubin levels to 70% to 80% of pre-exchange levels12. Administration of albumin half to one hour before the exchange, is associated with more effective removal of bilirubin. Instead of albumin primed exchange transfusion, some workers prefer addition of albumin into exchange blood itself2. Before the procedure, blood sample should be collected for Hb, Hct, bilirubin, glucose, potassium, and pH. Post Exchange, blood should be sent for Hb, Hct, bilirubin, glucose, calcium, potassium, and pH. Umbilical swab for culture sensitivity should be sent at the beginning and blood culture sensitivity at the end2. The procedure is performed by passing a 5 or 6 F catheter in umbilical vein for a distance where free flow of blood is obtained and blood is withdrawn with gentle suction and donor’s blood is injected slowly in aliquots of 5-10 ml depending on the size of baby. Heart rate, respiratory rate, SaO2 should be monitored throughout the procedure. An assistant must maintain an accurate record of IN/OUT blood and condition of the baby2. After exchange transfusion, PT is continued. 38 Complications2, 21 1. a. ACD blood causes hypocalcemia, hyperkalemia, and acidosis b. Heparinised blood causes hypoglycemia, increase in FFA leading to displacement of bilirubin from albumin binding sites. c. CPD blood is relatively safe but binds ionic calcium and magnesium and leads to hypocalcemia and hypomagnesemia. 2. Cardiovascular complications: Perforation of vessels, embolization, vasospasm, thrombosis, infarction, arrhythmia, volume overload and cardiac arrest. 3. Bleeding due to thrombocytopenia and deficient clotting factors. 4. Infections: Bacteremia, hepatitis, CMV, HIV, Malaria. 5. Hemolysis causing hemoglobinuria, hemoglobinemia, hyperkalemia. 6. GVHD – can be prevented by using irradiated blood. 7. Hypothermia hyperthermia 8. NEC. PHARMACOLOGICAL TREATMENT Here, the objective is to accelerate normal metabolic pathways for bilirubin clearance by using drugs: Phenobarbitone1, 2, 7, 12 Has long been in use for prevention of jaundice. It induces glucuronyl transferase enzyme thus improving conjugation as well as uptake and excretion of bilirubin by liver cells. Because of concerns about toxicity, it is rarely used, but there is increasing evidence that it can be a useful preventive measure, especially in preterms, hemolytic 39 settings and in the event of extravasated blood. If used in doses of 5 to 10mg/kg/day, it can have beneficial effect without significant adverse effects. A recent study by Arya VB et al.,26 concluded that prophylactic phenobarbitone is not helpful in reducing the incidence of hyperbilirubinemia in “at risk” term neonates. Protoporphyrins2, 7, 12 Metalloporphyrins are competitive, inhibitors of heme oxygenase, a rate limiting enzyme in heme catabolism, thus reducing the bilirubin production. Clinical trials have demonstrated that tin mesoporphyrins (SnMP) suppress bilirubin production. The drug has been found to be devoid of major adverse effects, transient cutaneous rash being the only one. SnMP at a single dose of 6μmol/kg proved more effective than phototherapy in a group of term and near term infants without hemolytic disease. Recently, a similar study on term breastfed infants without hemolytic disease also showed the ability of SnMP to abolish the need for phototherapy. Till date, SnMP remains experimental but it appears to hold a promise a future41-44. High dose intravenous immunoglobulin Recent studies have demonstrated that high dose of intravenous immunoglobulin therapy is effective in modifying the hyperbilirubinemia in most cases of Coomb’s positive hemolytic anemia. Intravenous immunoglobulin is given in dose of 500-1000mg/kg as slow infusion over 2 hours2, 7, 12. 40 New approaches for prevention of bilirubin brain damage are on the horizon, but phototherapy and exchange blood transfusion are still the most commonly used effective modalities for lowering TSB levels. 41 BRAINSTEM EVOKED RESPONSE AUDIOMETRY (AUDITORY BRAINSTEM RESPONSE) DefinitionIt represents the bioelectrical responses from auditory nerve and various nuclei in the brainstem in response to acoustic stimuli. Auditory Brainstem Response Waveform55 It consists of 5-7 vertex positive peaks that normally occur within 10 milliseconds after the presentation of stimuli. Responses are usually displayed with positive peaks reflecting activity toward vertex positive and these peaks are labeled with Roman Numerals I through VII. The negative troughs following each positive peak are labeled with Roman numerals and a prime (´) symbol such as wave I´. The full complement of seven waves is not always present in the BERA waveform, the most prominent vertex positive peaks being I, III and V. Neural Generators of the BERA55 BERA is generated by the auditory nerve and subsequent structures within the auditory brainstem pathways. Information regarding the origin of individual wave components of BERA was provided by Moller and Janetta. Wave I: It is the representation from the compound action potential in the distal portion of cranial nerve VIII. The response is believed to originate from afferent 42 activity of cranial nerve VIII fibres as they leave cochlea and enter the internal auditory canal. Wave II: It is generated by the proximal VIII nerve as it enters the brainstem. Wave III: Generated mainly in the cochlear nucleus (second order neuron). Wave IV: It arises from pontine third order neuron. Mostly located in superior olivary nucleus, but additional contributions may come from cochlear nucleus and nucleus of lateral lemniscus. Wave V: Generation of wave V reflects activity of multiple anatomic auditory structures. Sharp positive peak of wave V arises mainly from the lateral lemniscus, following slow negative wave represents dendritic potential in the inferior colliculus. Wave V is the component analysed most often in the clinical application of the BERA. Wave VI and VII: These waves appear to be generated in the inferior colliculus, perhaps in the medial geniculate body. Characteristics of a normal BERA55 Several parameters can be examined to determine whether or not an BERA is normal: a. Absolute Latency – The time interval between the stimulus onset and the peak of a waveform is referred to as the latency of the response .The unit of measurement of latency is millisecond. 43 The latency of BERA waveforms is the most reliable and robust characteristic and provides the core of BERA interpretation 44 b. Inter wave latency interval – The time between peaks in the BERA is referred to as inter wave latency interval / inter peak latency. The inter wave intervals used for clinical interpretation are I-III, III-V, and I-V. Wave I-III interval represents synchronous activity in 8th nerve and lower brainstem. Wave III-V interval reflects activity primarily within brainstem. I-V interval is considered a representation of overall activity from VIII nerve and nuclei and tracts of the brainstem responsive to auditory stimuli. c. Inter aural latency differences Inter aural latency differences compare the absolute latencies of wave V obtained from stimulation of the right versus left ear at equal intensity level. When peripheral hearing sensitivity is similar in each ear, latency should not differ by more than 0.2 -0.4ms. d. Latency Intensity Functions As the intensity of a stimulus decreases, the latencies of the peaks of BERA increase and response amplitude decreases. Latency intensity functions differ depending on the nature of a hearing disorder and differ for conductive, cochlear and retro-cochlear lesions. Conductive hearing losses are characterized by longer than normal latencies with latencies at all intensities being prolonged. Cochlear hearing loss often show a steeper than normal latency intensity function with prolonged latencies at low intensities. In retro cochlear auditory nerve/ brainstem disorder 45 latency of wave V is prolonged at all intensities but earlier peaks will be within Normal limits. e. Rate Changes Increasing the rate at which stimuli are presented results in latency and amplitude changes in BERA. When the stimulus rate is increased from about 10 stimuli per sec to 100 stimuli per sec., Wave V latency increases by approximately 0.5ms in normal individual. Increase in wave V latencies of more than 0.6-0.8 ms from lower to higher rate is considered abnormal. f. Amplitude A normal BERA ranges in amplitude from 0.1-1 µV. As the stimulus intensity decreases, response amplitude decreases. The lower amplitude earlier peak may become obscure with wave V remaining visible at lowest intensities. Amplitude of BERA is usually measured as peak to peak amplitude such as amplitude of a positive peak to the following negative trough [eg. Wave V-V’]. A reduced Wave V/I amplitude ratio may be diagnostically significant. Recording Techniques55 • Evoked potential should be acquired in a quiet test environment. • A sound treated room with appropriate acoustic and electrical isolation is desirable • Recording of the early evoked potential are best obtained when the patient is quiet and relaxed, sedation is often used in children 46 Stimulus types55 a. Clicks – An ideal stimulus for eliciting an BERA is a click, which is a brief rectangular pulse of 50-200 µs duration with an instantaneous onset. The rapid onset of click provides good neural synchrony, thereby eliciting a clearly defined BERA b. Brief tone bursts – These stimuli are very brief tones with rise - fall times of only a few cycles and brief / no plateau duration, eg. 2-1-2 consists of 2 cycles of tone in rise-fall and 1 cycle in plateau. Electrodes55 BERA is recorded from electrodes attached to various positions on head; BERA is generally plotted in the vertex positive direction with vertex upward. 2 methods1. Two channel recording 2. One channel recording Two channels recording using a 4 electrode montage are recommended for neurological applications in order to obtain ipsilateral and contralateral responses. One channel recording is done using 3 electrodes with attachments at vertex and one on each ear. Recordings are obtained between electrodes at the vertex and the ear receiving the acoustic stimulus with other ear electrode as the ground. Electrode application55 47 • Skin must be thoroughly cleaned to remove excess oil, dead skin and dirt to obtain a good contact between skin and electrode • Electrodes are filled with a conducting cream and taped into place • Once the electrodes have been applied, adequacy of contact with skin is assessed by measuring electrical impedance between each electrode pair. For high quality recording, inter electrode impedance ≤ 5kΩ is acceptable. Processing of electrical activity55 Electrical activity picked up by the recording electrodes within the specified time window must be processed through several stages to visualize the BERA waveform. This is because the BERA peaks are of extremely small voltage (>1µV) and are buried in a background of interference (termed ‘noise’), which includes ongoing electroencephalogram (EEG) activity, muscle potentials caused by movement or tension, and 50 Hz power-line radiation. The stages of processing include amplification, filtering, and signal averaging. Amplification and Filtering55 Because of small size of the BERA peaks, amplification is necessary to increase the magnitude of the electrical activity picked up by the electrodes. An amplifier gain of 105 is typically used. The problem of interference obscuring the BERA can be diminished partially by filtering the electrical activity coming from the electrodes. Bandpass filters are used to accept energy only within the particular frequency band of interest and reject 48 energy in other frequency ranges. For BERA recording, A filter setting of 30-3000 Hz is recommended to enhance the BERA when testing infants. Filtering can only eliminate a portion of the interfering noise because of overlap between the frequency content of the BERA and the frequency of the interference. Therefore, another technique, called signal averaging, must be used to further reduce unwanted interference. Signal Averaging55 The BERA is very small, and even with filtering, it is buried with a background of noise. Signal averaging helps to reduce this noise so that the signal, in this case the BERA, can be detected. Signal averaging is possible because the BERA is time-locked to stimulus onset, whereas the noise interference occurs randomly. That is, the signal occurs at the same points in time following onset of the eliciting stimulus, but the noise has no regular pattern. In signal averaging, a large number of stimuli are presented, and the responses to each of the individual stimulus presentations (termed ‘sweeps’) are averaged together to obtain a final averaged waveform. By averaging, the random noise tends to cancel out, whereas the evoked potential is retained because it is basically the same in each sweep. The greater the number of stimulus presentations used, the greater the improvement in signal to noise ratio, and the more clearly the BERA can be visualized in the final averaged waveform. 49 ROLE OF BERA IN NEONATAL HYPERBILIRUBINEMIA BERA is an effective and noninvasive means for the evaluation of auditory functions in the neonate. It is not significantly altered by the state of consciousness, drugs and variety of environmental factors51. BERA changes in response to hyperbilirubinemia include loss of one or more peaks of waves I to V, increase in latency of wave I, III or V or increased inter peak interval or raised threshold51. The acute changes seen in BERA can be reversed by early bilirubin lowering interventions, thereby explaining the transient nature of bilirubin encephalopathy. But persistent elevation of bilirubin can cause neuronal degeneration and thereby persistent changes on BERA. Some studies have found correlation between the bilirubin level and BERA changes, whereas some have disproved it. In a study done by Agrawal et al, it was found that 17 out of 30 (56.7%) neonates with jaundice showed abnormalities in initial BERA. Commonest change seen was raised threshold of wave V in 22 neonates (40%), absence of all waves at 90dBnHL (23.3%), prolongation of latencies of various waves (26.7%) and prolongation of various interval (26.7%). After therapy, abnormalities reverted back to normal in 10 cases & persisted in 7(41.7%). Development screening at l year was abnormal in 3 infants, all of whom had persistent abnormalities in BERA51. 50 Abnormal BERA was recorded in 22 out of 30(73.3%) cases and the abnormality persisted in the follow up tracings in 5 (16.6%) cases of the study group in a study done by Sharma et al52. In a study done by Gupta et al53, it was found that 56% of hyperbilirubinemic neonates had some abnormalities in ABR (Auditory Brainstem Response) pattern. ABR abnormalities were found with greater frequency in hyperbilirubinemic neonates requiring a repeat exchange transfusion (mean serum bilirubin:30.8+/-2.4 mg %). On follow-up retesting at 3 months, however all infants were found to have normal ABR latencies and threshold, suggestive of transient toxic brainstem encephalopathy. In a study done by Bhandari et al50, it was found that out of the 30 cases, 4 cases had absent ABR responses at the initial examination. After treatment, 3 babies had persistent absent responses and 2 of these were clinically kernicteric. Total plasma bilirubin level at the time of ABR examination had no correlation with the incidence and degree of ABR abnormalities. 7 out of 18 neonates with hyperbilirubinemia that were studied by Deorari et al54, had abnormal ABR. The abnormalities reversed to normal in all the seven cases after exchange blood transfusion, indicating transient nature of bilirubin toxicity to brain. All of these seven cases had normal hearing, development quotient and were free of neurological sequelae on follow up for one year. Thus serial BERA can be used as a tool to detect neuro developmental delay secondary to neonatal hyperbilirubinemia. 51 52 METHODOLOGY This study was conducted in the Department of Pediatrics of JSS Medical College, Mysore. The study period was between November 2007- May 2009. Study Design: CASE CONTROL STUDY Inclusion Criteria: Thirty consecutive term AGA (Appropriate For Gestational Age) neonates presenting to the NICU of J.S.S. Hospital, with total serum bilirubin requiring intervention (using the American Academy of Pediatrics guidelines3,11) were included in the study as cases and thirty normal term AGA neonates with uneventful peri-natal period and a maximum measured serum bilirubin <12 mg/dl were included as controls after obtaining informed consent.` Exclusion criteria: • Neonates born with birth asphyxia • Intrauterine infections • Sepsis • Meningitis • Amino glycoside administration • Craniofacial malformation • Preterm • Conjugated hyperbilirubinemia • Kernicterus 53 Mode of collection of data: All neonates presenting with icterus to the NICU of JSS Hospital were subjected to total bilirubin estimation. Total and direct bilirubin estimation was done by Jendrassik and Grof method. Term neonates meeting the inclusion criteria were included as cases. Data regarding the antenatal, birth history and detailed examination of the newborn were collected in a predesigned proforma (Ref. Annexure i). Weight was recorded using digital weighing scale. Gestational age assessment was done by modified Ballard score. Initial BERA was done within 3-24 hours of hospitalization after obtaining informed consent from parents. Procedure: BERA was performed in a dark quiet room. If the neonate was awake, it was sedated by 20mg/kg of triclofos orally. Cup electrode was used and was applied according to single channel, horizontal montage system of electrode placement. The recordings were obtained through a computer based software, Intelligent hearing system, version 3.3. Click acoustic stimuli with a click rate of 11.1/sec, rarefaction in polarity was presented by insert ear phone to each ear at an intensity from 90-30 dBnHL. Time window was 15 milliseconds; with a filter setting of 30-3000Hz. The presence of wave V at the Intensity of 30 dBnHL was taken as the normal threshold. BERA measures considered for diagnosis were • Loss of one or more peaks of I-V at 90 dBnHL. • Raised threshold 54 • Absolute latencies of wave I, III, V peaks. • Inter peak intervals of I - III, III - V and I – V. Neonates were treated for hyperbilirubinemia according to the standard treatment protocol (using the American Academy of Paediatrics guidelines) 3,11. Repeat BERA was done in all cases after therapy ¾ At the time of discharge and ¾ After a follow-up period of 3 months 55 Fig 1- A jaundiced baby under phototherapy. Fig 2. A jaundiced baby undergoing BERA 56 STATISTICAL METHODS APPLIED Following statistical methods were employed in the present study ¾ Descriptive statistics ¾ Frequencies ¾ Cross tabs procedure ¾ Independent-Samples T Test ¾ Paired samples t test ¾ Chi-Square Test Descriptive statistics The Descriptive procedure displays univariate summary statistics for several variables in a single table and calculates standardized values (z scores). Variables can be ordered by the size of their means (in ascending or descending order), alphabetically, or by the order in which one selects the variables (the default). Frequencies The Frequencies procedure provides statistics and graphical displays that are useful for describing many types of variables. The Frequencies procedure is a good place to start looking at one’s data. Cross tabs procedure 57 The Crosstabs procedure forms two-way and multi-way tables and provides a variety of tests and measures of association for two-way tables. The structure of the table and whether categories are ordered determine what test or measure to use. Independent-Samples T Test The Independent-Samples T Test procedure compares means for two groups of cases. Ideally, for this test, the subjects should be randomly assigned to two groups, so that any difference in response is due to the treatment (or lack of treatment) and not due to other factors. Paired samples t test The Paired-Samples T Test procedure compares the means of two variables for a single group. It computes the differences between values of the two variables for each case and tests whether the average differs from 0. Chi- Square Test It is a non-parametric test not based on any assumption or distribution of any variable. It is used in testing hypotheses about nominal scale data. It is basically a test of proportions. All the statistical methods were carried out through the SPSS for Windows (version 16.0) 58 RESULTS This study was done in the Department of Pediatrics, JSS Medical College, Mysore, over a period of 2 years from November 2007- May 2009. There were 34 cases and 30 controls in the study. BERA was done in both cases and controls. In the cases, BERA was done at peak level of bilirubin, at the time of discharge and at follow up after 3 months. Of the 34 cases, 28 cases came for follow up after a period of 3 months, whereas 6 were lost for follow up. BERA was done only once for controls. As there are no normative values of BERA parameter established for newborns, controls were taken. The mean and SD was computed for each parameter. The criterion for normality was considered to be within 2 SDs from the mean. The following values were established as normal range for our study. Table 2. Normal range of BERA parameter at 90 dBnHL PARAMETER NORMAL VALUE (Mean±2S.D.) LATENCY OF V WAVE 5.96-6.5 (6.24±0.27) LATENCY OF III WAVE 4-4.44 (4.22±0.22) LATENCY OF I WAVE 1.53-1.87 (1.69±0.16) LATENCY OF I-III 2.35-2.69 (2.52±0.17) 59 LATENCY OF III-V 1.67-2.03 (1.85±0.18) LATENCY OF I-V 4.22-4.54 (4.38±0.15) The following observation were made from the study and the study results were analysed using appropriate statistical analysis and compared with other studies. Table 3. Mean age (in days) of cases and controls Number Mean in days Case 34 5 Control 30 4.7 The mean age of babies among the cases was 5 days and among the controls was 4.7 days in our study. Graph 1. Mean age (in days) of cases and controls 60 61 Table 4. Sex wise distribution of cases and controls Case Control SEX n=34 n=30 Male 22 15 Female 12 15 In our study among the cases M: F ratio was 1.8:1 and among the controls it was 1:1 Graph 2. Sex distribution of cases and controls 62 Table 5. Average birth weight in kg of cases and control N Mean in kg Case 34 2.8621 Control 30 2.8370 In our study the average birth weight of the cases was 2.86kg and that of controls was 2.84kg Graph 3. Average birth weight in kg of cases and control 63 Table 6. Distribution of cases in different bilirubin range Maximum measured bilirubin in mg/dl Case (n=34) 15-20 22(64.7%) 20-25 7(20.6%) 25-30 5(14.7%) In our study it was found that majority of the cases 22 (64.7%) were having bilirubin in the range of 15-20mg/dl, 7 (20.6%) cases between 20-25mg/dl and 5 cases(14.7%) between 25-30mg/dl. Graph 4. Distribution of cases in different bilirubin range 64 65 Table 7. Number of cases with BERA changes BERA changes Cases (n=34) Present 12(35.3%) Absent 22(74.7%) In our study out of the 34 cases 12 (35.3 %) cases were found to have BERA changes in the form of absent wave forms, raised threshold, prolonged latencies or prolonged inter peak latencies. Graph 5. Percentage of cases with BERA changes 66 Table 8. Number of cases with different BERA changes at peak levels of bilirubin BERA Changes Cases* Absent wave forms 6(17.6%) Raised threshold 12(35.3%) Prolonged latencies I 3(8.8%) Prolonged latencies III 5(14.7%) Prolonged latencies V 5(14.7%) Prolonged Inter peak interval 6(17.6%) I-III Prolonged Inter peak interval 0 III-V Prolonged Inter peak Interval 4(11.8%) I-V * No. of cases as percentage of the total sample size is shown along with the no.s In our study, it was found that raised threshold was the most common BERA change observed in majority of the patient 12(35.3%) cases, absent wave forms at 90 dB was seen in 6(17.6%) cases of which 3 had bilateral absent responses. Prolonged latency I, III, V, prolonged inter peak latency I-III and I-V were seen in 8.8%, 14.7%, 67 14.7%, 17.6% and 11.8% of cases respectively. Prolonged inter peak III-V was not observed in any of the cases. Graph 6. Number of cases with different BERA changes at peak levels of bilirubin 68 Table 9. Comparison of latencies of I, III, V of cases at peak level of bilirubin, at the time of discharge and follow-up at 90 dBnHL At peak At discharge At followup p value p value p value level(A) In msc (B) In msc (C)In msc A Vs B B Vs C A Vs C I 2.1088 1.7707 1.5814 0.041 0.098 0.017 III 4.5600 4.4813 4.1750 0.342 0.284 0.112 V 6.8250 6.6643 6.3521 0.545 0.107 0.145 Waves p value was significant only for wave I when latency at peak level was compared with that at discharge and follow-up Table 10. Comparison of inter peak latencies of cases at peak level of bilirubin at the time of discharge and follow-up at 90 dBnHL At peak level At discharge At followup p value p value p value (A) In msc (B) In msc (C) In msc A Vs. B B Vs. C A Vs. C I –III 2.7592 2.5575 2.6067 0.201 0.816 0.475 III-V 2.0808 2.1133 2.2375 0.857 0.430 0.286 I-V 4.7567 4.6508 4.6567 0.679 0.685 0.801 Waves 69 p value was not significant for any of the inter peak intervals Table 11. Comparison of BERA changes at peak level of bilirubin at the time of discharge and follow-up BERA Changes Peak At Follow level discharge up Absent wave forms 6(17.6%) 3(8.8%) 1(2.9%) Raised threshold 12(35.3%) 8(23.5%) 1(2.9%) Prolonged latencies I 3(8.8%) 0 0 Prolonged latencies III 5(14.7%) 2(5.9%) 2(5.9%) Prolonged latencies V 5(14.7%) 2(5.9%) 2(5.9%) 6(17.6%) 1(2.9%) 0 0 0 0 4(11.8%) 0 0 Prolonged Interpeak Interval I-III Prolonged Interpeak Interval III-V Prolonged Interpeak Interval I-V In our study, it was found that out of the 12 (35.3%) cases which had BERA changes at peak level of bilirubin, 9 (26.4%) cases had persistent changes at the time of discharge. Of these 9 cases, on follow up at 3 months 3 (8.8%) cases had persistent 70 changes and 2 were lost for follow up. Among the cases which had absent responses 3 cases continued to have absent responses bilaterally at the time of discharge. When these cases were followed up, it was found that 1 case had persistent absent response, 1 was lost for follow up and in 1 case, wave forms appeared but with slightly prolonged latency of V peak. All these 3 cases had bilirubin > 25mg/dl before therapy. Among the 12 cases with raised threshold it was found that 8(23.5%) cases had raised threshold even at discharge but on follow up only 1(2.9%) case had persistently raised threshold. Of the 3 cases with prolonged latencies of wave I on follow up all were found to have improved latencies, Of the 5 cases with prolonged latencies III and V, 2 had persistent changes at discharge ,as well as at follow up whereas in 3 cases it was found that latencies improved. Similarly it was found that of the 6 cases with prolonged I-III and 4 cases with prolonged I-V when followed up all had normal latencies. Table 12. Correlation of Bilirubin level with BERA changes Maximum measured No. of Cases with % of cases showing bilirubin in mg/dl Cases BERA changes BERA changes 15-20 22 4 18% 20-25 7 3 43% 25-30 5 5 100% χ2=12.163 p value< .002 71 In our study, it was observed that there was statistically significant correlation between increasing bilirubin level and BERA changes. Table 13. Type of treatment given to cases Type of treatment Frequency Percentage Exchange transfusion + phototherapy 4 11.8 Phototherapy 29 85.3 Phototherapy + phenobarbitone 1 2.9 Total 34 100.0 In our study, majority of the cases 29 (85.3%) had received phototherapy, 4 underwent exchange transfusion and one child received phototherapy with phenobarbitone in view of inability to perform exchange transfusion due to non availability of a central or umbilical line. Graph 7. Types of treatment given to the cases 72 BERA REPORTS Fig 3. A BERA report of a control showing normal BERA waveforms. Fig 4. A BERA report showing absent waveforms at 90 dBnHL 73 Fig 5 A BERA report showing raised threshold i.e absent waveforms at 30 dBnHL but presence at 50 dBnHL Fig 6. A BERA report showing prolonged latency V of 7.2ms 74 Fig 7. A BERA report showing prolonged interpeak interval I-V of 5.4 ms 75 DISCUSSION Neonatal unconjugated hyperbilirubinemia is neurotoxic. Besides other sequelae, it is found to be particularly toxic to the auditory pathway and may result in sensorineural hearing loss. BERA provides an accurate and non invasive evaluation of the auditory pathway. The BERA changes in response to hyperbilirubinemia includes loss of one or more peaks of waves I-V, raised threshold, increase in latency of wave I, III or V or increased inter peak interval. Some of the earlier observations of BERA have demonstrated the reversible effects of bilirubin toxicity. This study was undertaken to evaluate the effect of hyperbilirubinemia in term newborns on BERA and change if any after therapy. In our study, it was observed that 12 out of 34 cases had BERA changes at peak level of bilirubin. Among the changes, most common abnormality was raised threshold seen in all the 12 cases (35.3%). 76 Table . 14 Comparison of various BERA changes in different studies Parameter Cases with BERA Our Agrawal Sharma Gupta et Study et al et al al et al et al n=34 n=30 n=30 n=25 n=18 n=30 12(48%) 7 (39%) 14 12(35.3%) 17(56.7%) 22(73.3%) Deorari Bhandari (46.6%) Changes Absent Wave form 6(17.6%) 7(23.3%) - 5(16.5%) 5 (28%) - Raised Threshold 12 (35%) 22(73.3%) - 12(48%) - - Prolonged latency I 3(8.8%) 3(10%) 22(73.3%) 10(40%) - - Prolonged latency III 5(14.7%) 7(23.3%) - - - Prolonged latency V 5(14.7%) 8(26.7%) - 4(22%) - Prolonged latency 6(17.6%) 2(6.7%) - - - - - - - - 4(11.7%) 6(20%) - 6(33.3%) - 22(73.3%) I-III Prolonged latency III-V Prolonged latency I-V The frequency of BERA abnormalities noted in our study was slightly less compared to other study. The commonest abnormality observed in our study was raised threshold seen in 12 (35.3%) cases which was comparable with other studies. 77 The other commonest abnormalities noted was prolonged latencies (14.7%) and absent wave forms (17.6%) which were also comparable with other studies. Prolonged latencies of waves and inter peak interval indicated prolongation of nerve conduction at auditory nerve and brain stem level. All cases were reviewed with a follow up BERA at the time of discharge and after a period of 3 months in our study and in other studies by Sharma et al, Gupta et al and Agrawal et al. Whereas Deorari et al followed up the cases till 1 year. Bhandari et al did not follow up the cases. Out of the 12 cases with significant BERA changes, it was found that 9 cases had persisted abnormalities at the time of discharge and 3 cases were found to have persistent abnormalities at the time of follow up after 3 months. Table 15. Comparison of the BERA changes at peak level at discharge and follow up with other studies Study n At peak level At discharge At follow up Our study 34 12 (35%) 9 (26%) 3(8.8%) Agrawal et al 30 17 (56.7%) 7 (23.3%) 3 (10%) Sharma et al 30 22(73.3%) 7 (23.3%) 5 (16.7%) Bhandari et al 30 5 (16.7%) 2 (6.6%) - Deorari et al 18 7 (39%) 0 0 Gupta et al 25 12 (48%) 0 0 78 In the study done by Agrawal et al, it was found that 7 out of 17 (41.7%) had persistent changes at discharge. Of these, 3 cases had persistent changes at follow up. It was found that latency of different waves and interval decreased significantly after therapy. Response remained absent in 2 of 7, raised threshold persisted in the rest 5. At follow up after 3 months, 3 had persistent abnormalities51. In the study by Sharma et al, it was found that 7 cases had persistent changes among which latencies had normalized, but prolonged inter wave intervals persisted. On follow up at 3 months, 5 cases continued to have changes52. But studies by Deorari et al and Gupta et al showed normalization of BERA changes at follow up, indicating transient nature of Bilirubin encephalopathy53,54. By binding to the nerve terminals, bilirubin causes a reversible lowering of membrane potential and a decrease in nerve conduction6, thus explaining the reversibility of early bilirubin encephalopathy1. Improved brain functions may be due to removal of bilirubin because of phototherapy or exchange transfusion. At higher concentration, the nerve terminals are severely injured and bilirubin penetrates the axons with retrograde uptake into the cell body and also, if acidosis persists, BH2 is formed resulting in permanent neuronal damage6. In our study, it was found that there was significant correlation between serum bilirubin more than 25mg and presence of significant BERA changes. The study by Bhandari et al found that mean maximum bilirubin level had no correlation with the incidence and degree of BERA abnormalities. In their study, in 5 babies who had BERA changes, mean level of bilirubin was 17.82 +/- 3.87. This was 79 not significantly different from the value of 16.95 +/- 2.76mg/dl average value of bilirubin of 30 babies50. Whereas studies by Sharma et al, Agrawal et al, Deorari et al, Gupta et al, also found statistically significant correlation of BERA changes with Serum Bilirubin >25mg. Indicating that higher the level of bilirubin there is increased risk of bilirubin toxicity but with active intervention, it is possible to reverse the changes. Correlation of the findings of this study with previous few studies indicates that BERA can be used as a useful non invasive tool to determine auditory functions in the neonate especially changes of early bilirubin toxicity. 80 SUMMARY In the present study, there were 34 cases and 30 controls. BERA was done in both cases and controls. In the cases, BERA was done at peak level of bilirubin, at the time of discharge and at follow up after 3 months. Of the 34 cases, 28 cases came for follow up after a period of 3 months, whereas 6 were lost for follow up. The mean age of the cases was 5 days and it was 4.7 days in controls. The male to female ratio was 1.8:1 among cases while it was 1:1 among controls. Average birth weight of cases in our study was 2.8621kg and that of controls was 2.8370kg. Majority of the cases, 22 cases (64.3%) had maximum measured bilirubin between 15-20 mg/dl, 7 cases (20.6%) between 20 to 25 mg/dl and 5 cases (14.7%) with bilirubin between 25 to 30 mg/dl. 12 (35.3%) out of 34 cases in our study had BERA changes. The most common BERA change noted in our study was raised threshold seen in 12 cases (35.3%), absent wave form seen in 6(17.6% )of cases. Prolonged latencies I was seen in 3(8.8% )of cases, prolonged latencies III and V were seen in5( 14.7%) cases, prolonged I-III interpeak interval and prolonged I-V in 6(17.6%) and 4(11.8% ) cases, respectively. Prolonged III-V was not noted in our study. 81 BERA changes persisted in 9 cases at the time of discharge of which in 3 cases, changes persisted at follow up after 3 months. 2 out of the 12 cases with BERA changes were lost for follow up. Absent wave forms persisted in 3 cases at the time of discharge, of which in one case, it persisted at follow up, in one case wave forms appeared with slightly prolonged latencies and other child was lost for follow up. Raised threshold persisted in 8 cases at discharge, of which in one case it persisted even at follow up. All the 3 cases with prolonged latency I when followed up had improved latencies. Prolonged latencies III and V persisted in 2 out of 5 cases at discharge, which persisted even at follow up. It was found that of the 6 cases with prolonged I-III and 4 cases with prolonged I-V latencies on follow up all had improved latencies. In our study, it was found that all the 5 cases with bilirubin >25mg/dl had BERA changes and out of these 5, 3 cases had persistent BERA changes at follow up thus there was significant correlation between BERA changes and maximum measured bilirubin indicating that higher the level of bilirubin, higher the risk of toxicity to auditory pathway. However, this study should be validated with further larger study. 82 CONCLUSION Hyperbilirubinemia is one of the common problems encountered in the neonatal period. Auditory neuropathy is noted in one third to half of infants with significant hyperbilirubinemia and may result in sensori-neural hearing loss. BERA can be used as an effective and non invasive means of assessing the functional status of the auditory pathway. 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Deorari AK, Singh M, et al: One year outcome of babies with severe neonatal hyperbilirubinemia and reversible abnormality in brainstem auditory evoked responses. Indian Pediatr 1994; 31:915-921. 55. Arnold SA: The Auditory Brainstem Response. In Roeser RJ, Valente M, Hosford H(editors) : Audiology Diagnosis, 2nd edition. New York, Thieme, 2007; 426-441. 89 PROFORMA (For Data Collection as part of the thesis being done by Dr.Nayana Nayak, J.S.S.Medical College, Mysore) 1. Name 4. I.P. No. 2. Age in Days 5. DOA 3. Gender 6. DOD 7. Mother’s Name 9. 8. Occupation 10. Occupation Father’s Name 11. Address 12. Phone No. (Residence) (Mobile) 13. Diagnosis 14. Day of life on which Bilirubin was in phototherapy range 90 15. Birth History A. Type of delivery B. APGAR C. Birth Weight 16. Mother’s History A. Age B. Married Life C. Consanguinity D. Gravida 17. Details of Present Pregnancy 91 18. Examination Vitals S/E 19. Investigations Hb% Mothers Blood group TC Maximum measured T.Bilirubin DC Bilirubin at the time of Discharge PBS Additional investigation if any Reticulocyte Count DCT Baby Blood Group 92 20. Treatment TypePhototherapy / Exchange If phototherapy, then, How many days? 21. BERA A. At Peak Level of Bilirubin i. Absolute Latencies RIGHT EAR (msec) INTENSITY/ LEFT EAR (msec) RATE I ii. III V I III V Interpeak Intervals/Latencies (msec) RIGHT EAR (msec) I-III III-V LEFT EAR (msec) I-V I-III 93 III-V I-V B. At the time of discharge i. Absolute Latencies RIGHT EAR (msec) INTENSITY/ LEFT EAR (msec) RATE I III V I III V ii. Interpeak Intervals/Latencies (msec) RIGHT EAR (msec) I-III III-V LEFT EAR (msec) I-V I-III III-V I-V C. After 3 Months iii. Absolute Latencies RIGHT EAR (msec) INTENSITY/ LEFT EAR (msec) RATE I III V I III V iv. Interpeak Intervals/Latencies (msec) RIGHT EAR (msec) I-III III-V LEFT EAR (msec) I-V I-III Signature Of the Guide 94 III-V I-V 95 KEY TO MASTER CHART AWF Absent wave forms RT Raised threshold PL I Prolonged latencies I 96 PL III Prolonged latencies III PL V Prolonged latencies V PIPI I-III Prolonged Inter peak Interval I-III PIPI III-V Prolonged Inter peak Interval III-V PIPI I-V Prolonged Inter peak Interval I-V Yes With BERA changes No With no BERA changes NS No show (lost for follow-up) ET Exchange transfusion 97 98 Sl. No. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 Name B/O Hemalatha B/O Rupa B/O Mahadevamma B/O Pushpa B/O Ashakiran B/O Rani B/O Bindu B/O Jyothi B/O Lakshmamma B/O Suma B/O Bhavya B/O Zobeda B/O Sudha B/O Geetha B/O Roopa B/O Leelavathi 1 B/O Leelavathi 2 B/O Sheena B/O Anitha B/O Shantala B/O Saritha B/O Umamaheshwari B/O Thayaba Sultana B/O Suma B/O Shini B/O Shamala B/O Poornima B/O Dharitri B/O Shweta B/O Sangitha B/O Satvi B/O Mahadevamma B/O Saraswati B/O Shilpa Age in Days 10 8 5 4 5 2 3 4 4 5 5 4 5 3 4 6 8 5 5 4 4 4 6 3 5 4 4 5 5 6 6 6 6 5 Gender Birth Weight in kg Type of Delivery Baby's Blood Group Male Male Male Male Male Male Female Male Male Female Female Male Male Male Male Female Female Female Female Female Male Male Male Male Male Male Female Male Male Female Female Female Male Male 2.5 2.75 3.3 3.5 2.5 3 2.6 3 2.6 2.5 2.6 3.25 2.8 2.6 2.5 2.6 2.5 3 2.9 2.75 3.5 2.75 2.6 2.8 2.75 3.4 3.4 2.75 2.9 2.9 3 2.6 2.6 3.25 LSCS Vaginal Vaginal Vaginal Vaginal Vaginal Vaginal Vaginal LSCS LSCS Vaginal LSCS Vaginal LSCS LSCS LSCS LSCS LSCS Vaginal Vaginal LSCS Vaginal LSCS Vaginal LSCS LSCS Vaginal Vaginal LSCS Vaginal LSCS LSCS Vaginal Vaginal A+ve O+ve A+ve A+ve O+ve O+ve A+ve O+ve A+ve O+ve O+ve B+ve O+ve O+ve O+ve O+ve O+ve O+ve O+ve O+ve O+ve O+ve O+ve B+ve B+ve A+ve O+ve O+ve O+ve A+ve O+ve O+ve AB+ve A+ve MASTER CHART- Patient Details Mother's Date of DCT Blood Admission Group A-ve O+ve O-ve O+ve B+ve O+ve A+ve B+ve A+ve O+ve O+ve AB-ve O+ve O+ve O+ve O+ve O+ve O+ve O+ve O+ve A-ve B+ve O+ve O+ve O+ve A+ve O+ve O+ve O+ve O+ve O+ve O+ve AB+ve O+ve Positive Negative Positive Negative Negative Negative Negative Negative Negative Negative Negative Negative Negative Negative Negative Negative Negative Negative Negative Negative Negative Negative Negative Negative Negative Negative Negative Negative Negative Negative Negative Negative Negative Negative 99 9-Feb-08 12-Jan-08 24-Jan-08 18-Jan-08 18-Jan-09 15-Nov-08 18-Feb-09 16-Jan-09 7-Jan-09 4-Nov-08 11-Feb-08 25-Oct-08 18-Jun-08 3-Feb-09 10-Oct-08 12-Oct-08 14-Oct-08 27-Nov-08 29-Jan-09 25-Feb-08 10-Oct-08 22-Aug-08 8-Dec-07 6-Dec-07 10-Oct-08 2-Nov-08 16-Nov-08 10-Nov-08 2-May-08 16-Apr-08 20-Jan-09 4-Feb-08 29-Apr-09 4-Dec-08 Date of Discharge Max level of Bilirubin in mg/dl Level of Bilirubin at discharge in mg/dl 15-Feb-08 22-Jan-08 30-Jan-08 24-Jan-08 21-Jan-09 20-Nov-08 22-Feb-09 19-Jan-09 16-Jan-09 8-Nov-08 14-Feb-08 4-Nov-08 22-Jun-08 9-Feb-09 21-Oct-08 22-Oct-08 23-Oct-08 2-Dec-08 3-Feb-09 1-Mar-08 14-Oct-08 27-Aug-08 12-Dec-07 10-Dec-07 17-Oct-08 11-Nov-08 21-Nov-08 15-Nov-08 8-May-08 22-Apr-08 25-Jan-09 6-Feb-08 3-May-09 10-Dec-08 30 19.9 28.19 25.46 26.55 15.42 15.6 23.8 20.02 16.01 24.8 26.9 18.4 18.22 15.08 20.7 19.84 15.26 24.96 23 19.26 17.6 16.28 17.46 17.61 17.01 17.62 17.32 19.24 18.26 19.22 17.96 20.2 18.26 14 8.74 14.02 13.25 11.2 14.96 12.38 10.55 12.3 11.12 13.96 11.15 11.2 12.38 11.76 10.12 9.62 13 12.36 12 7.98 11.5 12.91 13.48 11.76 9.19 11.48 10.26 13.2 12.48 12.24 10.4 15.6 11.24 Type of Treatment No.of days of therapy Phototherapy+ Phenobarbitone Phototherapy ET + Phototherapy Phototherapy Phototherapy Phototherapy Phototherapy Phototherapy Phototherapy Phototherapy Phototherapy ET+Phototherapy Phototherapy Phototherapy Phototherapy Phototherapy Phototherapy Phototherapy ET + Phototherapy ET + Phototherapy Phototherapy Phototherapy Phototherapy Phototherapy Phototherapy Phototherapy Phototherapy Phototherapy Phototherapy Phototherapy Phototherapy Phototherapy Phototherapy Phototherapy 4 6 6 5 3 2 3 2 2 3 2 5 3 2 4 3 3 5 4 5 3 3 3 3 2 2 2 4 3 4 3 2 4 4 MASTER CHART- Cases with different BERA changes at various levels AT PEAK LEVELS Sl. No. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 AWF Yes Yes No No No No Yes No Yes No Yes Yes No No No No No No No No No No No No No No No No No No No No No No RT Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No No No No No No No No No No No No No No No No No No No No No No PL I No No Yes No No No No Yes No No Yes No No No No No No No No No No No No No No No No No No No No No No No PL III No No Yes Yes yes No No Yes Yes No No No No No No No No No No No No No No No No No No No No No No No No No PL V No No Yes Yes Yes No No Yes Yes No No No No No No No No No No No No No No No No No No No No No No No No No PIPI I-III No No No Yes Yes Yes No Yes Yes Yes No No No No No No No No No No No No No No No No No No No No No No No No AT DISCHARGE PIPI IIIV No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No PIPI I-V No No No Yes Yes No No No Yes Yes No No No No No No No No No No No No No No No No No No No No No No No No AWF Yes Yes Yes No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No RT Yes Yes Yes No Yes No Yes No No Yes Yes Yes No No No No No No No No No No No No No No No No No No No No No No PL I No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No PL III No No Yes No Yes No No No No No No No No No No No No No No No No No No No No No No No No No No No No No 100 PL V No No Yes No Yes No No No No No No No No No No No No No No No No No No No No No No No No No No No No No AT FOLLOW UP PIPI I-III No No No No No Yes No No No No No No No No No No No No No No No No No No No No No No No No No No No No PIPI IIIV No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No PIPI I-V No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No AWF Yes No No No No No No No No No NS NS No No No No No No No No No No No No No No No No No No NS NS NS NS RT Yes No No No No No No No No No NS NS No No No No No No No No No No No No No No No No No No NS NS NS NS PL I No No No No No No No No No No NS NS No No No No No No No No No No No No No No No No No No NS NS NS NS PL III No No Yes No Yes No No No No No NS NS No No No No No No No No No No No No No No No No No No NS NS NS NS PL V No No Yes No Yes No No No No No NS NS No No No No No No No No No No No No No No No No No No NS NS NS NS PIPI I-III No No No No No No No No No No NS NS No No No No No No No No No No No No No No No No No No NS NS NS NS PIPI IIIV No No No No No No No No No No NS NS No No No No No No No No No No No No No No No No No No NS NS NS NS PIPI I-V No No No No No No No No No No NS NS No No No No No No No No No No No No No No No No No No NS NS NS NS 101 102
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