Aspects of jaundice in neonatal babies

This essay will explore the pathophysiology, management and psychosocial aspects of jaundice in the paediatric patient, specifically in neonatal babies. Information has been gathered through the use of history taking, examination, and analysing the patient’s medical records to form a case study in which the topics aforementioned will be considered in relation to the case study.

Section A – Case History

TH is a 2 day old male Caucasian baby who was admitted to the neonatal intensive care unit (NICU) presenting with neonatal jaundice. TH’s mother had a premature rupture of her membranes (PROM) consequently causing TH to be born prematurely at 33 weeks, and weighing in at 1779g. This was her first pregnancy (primigravida). He was born in good condition and was instantly crying on delivery. At birth, TH had a heart rate of 150bpm, a respiratory rate of 42 breaths per minute, temperature at 37.2°C, and SATs of 100% in air. He was slightly grunting so facial oxygen was given, however shortly on admission to AMU, he was self ventilating. The mother was fine, but was moved to the post natal ward to be put under surveillance in case she developed chorioamnionitis or sepsis. She would come down to the neonatal unit to bond with TH once to twice a day for a couple of hours.

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TH was then nursed in an incubator where intravenous fluids were commenced (10% dextrose through a cannula running at 4.4ml/hour). He was given cefotaxime in the morning to prevent him from getting an infection, and then again at midnight. He was also routinely given intramuscular konakion (vitamin K) in his thigh. The mother wanted to breastfeed, and although skin to skin contact was made, feeding could not be established. He was therefore fed 5ml of SMA prem 1 2×12 hourly via a nasogastric tube (NG tube). A small amount of urine and meconium was passed, and there was no vomiting or colic.

On examination TH had a head circumference of 30.1cm, with his fontanelles being normal when palpated. His eyes were fine, palate intact and his respiratory system was clear bilaterally. Heart sounds that were heard were normal, femoral pulses were felt, the abdomen was soft when palpated and the spine was not deformed. His anus was patent, genitalia were normal and there was no deformity of any of his limbs with normal tone. When tested, the moro reflex was positive and normal and he demonstrated a good grasping reflex.

The next day (24 hours after birth), TH was now tolerating 2×12 hourly feeds of expressed breast milk (EBM) from his mother and SMA prem 1 at 90ml/kg/day via an NG tube. The cefotaxime was continued.

48 hours after TH’s birth, he was now on 120ml/kg/day of 2×12 hourly feeds of EBM and SMA prem 1via his NG tube. He had passed urine and opened his bowels twice that day. A yellowing of TH’s skin was observed so his serum bilirubin levels (SBR) were checked; a result of 234µmol/l was obtained, which is above the normal treatment line. As it was confirmed that TH was jaundiced he was immediately transferred to the neonatal special care unit, where double phototherapy was commenced. That same day in the evening, TH’s SBR had been reduced to 202µmol/L after receiving phototherapy.

Section B – Pathophysiology

Introduction

Jaundice, or icterus, is characterised by the yellowing discolouration of the skin, the deep tissues and the sclera of the eyes. 1 It is usually clinically detected when the serum bilirubin levels are greater than 40-50µmol/L (when the jaundice is observable). 2 3 In TH’s case, he is most likely suffering from neonatal physiological jaundice which is relatively common, particularly in premature infants, however a differential diagnosis of pathological and physiological causes must be made so that serious concerns may be noted and ruled out. 3 Although the jaundice does fade in time as the liver of the premature infant matures, it can be dangerous if the SBR are at high levels (hyperbilirubinaemia). 2 3

Hyperbilirubinaemia

Hyperbilirubinaemia is when the levels of bilirubin in the blood are higher than the normal values (TH’s being 234µol/L); bilirubin is a product of the lysis of red blood cells in the body. 5 Breakdown from red blood cells produces unconjugated (or indirect) bilirubin, which is insoluble in water, so it must be metabolised in the liver so that it becomes conjugated and can pass through the gut and be excreted in the stool and urine. 2 5 In neonates, high levels of unconjugated bilirubin can cross the blood-brain barrier; this is potentially harmful to the neural tissue of the brain and may result in causing bilirubin encephalopathy or kernicterus. 2 5 TH’s hyperbilirubinaemia and jaundice only become present 2 days post partum. Although not serious at the moment, one must come up with a differential diagnosis for TH to make sure that potential pathological, life threatening causes such as kernicterus, are dealt with immediately.

Kernicterus

The term kernicterus literally means, “jaundice of the nucleus”. 3 This is due to deposition of high levels of unconjugated bilirubin, for example in maternal-foetal Rhesus disease. 3 Acute features of the latter would include abnormal muscle tone and posture, apnoea and convulsions, none of which were present in TH on examination. 5 In serious cases which would be fatal, the bilirubin would be deposited on the basal ganglia, brainstem and thalamus nuclei, which would show up as bright yellow in colour. 3

Pre-Hepatic Causes

Haemolysis of an infant’s red blood cells is one of the most common causes of “pre-hepatic jaundice”. 2 Pathological haemolytic jaundice can be subcategorised into two types: intrinsic, where the defect is in the cell itself, or extrinsic where the problem is outside of the cell. 6 An example of intrinsic haemolytic jaundice could be spherocytosis, where the red blood cells are sphere shaped rather than biconcave and can burst easily due to their less flexible configuration. 3 An extrinsic example could be Rhesus disease; this is where the antibodies from a mother can destroy her baby’s blood cells due to an incompatibility of blood types between the two. 7 When a pregnant woman who is Rh negative whose husband is Rh positive, carries a foetus who is also Rh positive, the blood of the foetus would cross over to the placenta and cause anti-Rh agglutinins to be created in the mother’s blood. 8 These would then pass back to the foetus and eliminate the Rh positive blood of the foetus, consequently causing haemolytic jaundice and anaemia. 8 It would usually take more than one pregnancy for the mother’s blood to build up enough anti-Rh antibodies to damage the foetus, so this would be unlikely in TH as this was his mother’s first pregnancy. 8 In TH, the most likely pre-hepatic cause would be physiological. This would probably be due to the immaturity of the baby’s liver not processing the bilirubin when foetal red blood cells are haemolysing to make way for the adult red blood cells. 1 As the bilirubin would be unconjugated, it cannot be excreted and so the baby would become jaundiced.

Hepatic Causes

Although some causes of hepatic jaundice are idiopathic, it is most commonly seen due to an acute infection, such as hepatitis B, or the immaturity of the baby’s liver being unable to cope with the conjugation of the bilirubin. 1 3 In Th’s case, it seems to be due to the immaturity of his hepatocytes failing to take up or conjugate the bilirubin. A possible reason for the lack of conjugation could be due to decreased levels of UDPG transferase activity. 2 This enzyme is responsible for the conjugation of bilirubin to glucaronic acid; reduced hepatic glucurodination results in an increased proportion of bilirubin mono-glucuronide in bile.2 As most of the bilirubin would predominantly be unconjugated, there would be minimal excretion of bilirubin and jaundice would be seen.

Post Hepatic Causes

Jaundice can also occur in infants due to structural congenital abnormalities. 3 Malformations of the biliary system and congenital obstructions, such as biliary atresia which is characterised by the failure of bile duct development during embryogenesis, can cause obstructive post hepatic jaundice with conjugated hyperbilirubinaemia. 3 5 There is also a genetic component to structural abnormalities such as Alagilles’s syndrome (or biliary hyperplasia), which is an autosomal dominant where the lack of bile ducts are also accompanied by mental retardation and skeletal abnormalities. 3 Problems like congenital obstruction would need immediate specialist investigation and early surgical treatment. 5 Infants with an obstruction or congenital abnormality would usually become jaundiced within the first 24 hours, so it is unlikely that TH would have this.

Physiological Causes of Jaundice

Neonatal physiological jaundice is when excess unconjugated bilirubin, which is not water soluble, is deposited in the skin instead of being delivered to the liver where it can be processed and converted into water soluble, conjugated bilirubin which can be excreted out of the body into the urine or faeces. 9 Physiological jaundice usually presents itself 48-72 hours after birth and disappears within a week; if it is physiological it is never present before 24 hours. 9 10 This is perfectly normal and affects approximately 50% of term babies and 80% of premature babies, just like TH who presented with jaundice after 48 hours. 10 The factors that are associated with physiological jaundice are multifactorial: firstly the levels of haemoglobin may be higher than required when foetal haemoglobin is being replaced with adult haemoglobin. Red blood cells may also have a shorter life span, meaning faster lysis and a quicker build up of unconjugated bilirubin. It could also be due to hepatic immaturity, especially in pre-term babies like TH. 10 This could be due to reduced glucuronyl transferase activity (which catalyses the deconjugation of bilirubin), reduced active uptake of unconjugated bilirubin, a reduced intracellular transport system, or a reduced active secretion of conjugated bilirubin into the bile ducts. 9 10

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It is argued that breastfeeding is the best choice in terms of infant nutrition; 11 however breastfeed babies’ SBR concentrations tend to be higher than formula fed infants within the first week of life. 5 12 Breast milk is plentiful in the enzyme β-glucoronidase, whereas standard infant formula feeds have negligible amounts of β-glucoronidase; consequently infants who are formula fed are less likely to be jaundiced compared to breast fed infants. 13-15 β-glucoronidase plays a big role in neonatal jaundice because it increases the effect of the enterohepatic circulation of bilirubin, possibly due to sluggish gut movements, 5 by deconjugating intestinal bilirubin conjugates, producing unconjugated bilirubin that can be absorbed better by the baby’s intestines. 13 This is normal in utero as the placenta can facilitate the clearance of bilirubin, however after birth the enterohepatic circulation of bilirubin delays clearance, thus causing the baby to look jaundiced. 16 Casein hydrosylate in some formula feeds can inhibit β-glucoronidase, therefore infants consuming these formulas are less likely to develop jaundice compared to infants on routine formula feeds. 14 15 A study showed that the main inhibitor to β-glucoronidase in casein hydrosylate feeds is L-aspartic acid. 17 Furthermore, another study showed that if prophylaxis (β-glucoronidase inhibitors) was given to newborn babies a week after birth, there was a significant reduction in transcutaneous bilirubin levels compared to control subjects. 18 The fact that TH was started on expressed breast milk (EBM) 24 hours after birth, and then presented with jaundice 24 hours after his first feed of EBM, makes it highly probable that his jaundice stems from physiological origins. This is also coupled with the fact that he did not present with jaundice before 24 hours, strongly pointing towards physiological jaundice.

Section C – Treatment and Management

As neonatal jaundice has the potential to cause both acute and chronic impairments in brain function due to kernicterus, it is this that promotes therapeutic intervention. 19 The most effective and commonly used form of treatment for neonatal jaundice is phototherapy. 19 20 This is done by placing the baby under a lamp in which light is emitted from it in the blue spectrum.5 Phototherapy is used to convert the structure of the bilirubin molecule into an isomer that is water soluble so that it can be excreted in the urine. 20 The stereoisomers that are left are more polar than the predominant IXα (4Z,15Z) isomer which needs to be conjugated in the liver to be excreted. 20 The isomer that is most rapidly formed is one in which one of the double bonds in the bilirubin molecule has undergone a cis-trans isomerisation from a Z (zusammen) configuration to an E (entgegen) configuration. 20 This therefore converts the normal 4Z,15Z isomeric form of bilirubin to the water soluble 4E,15E isomer, which occurs in femtoseconds (10-15 of a second) due to the photochemical reaction. 20 TH underwent double phototherapy. This is slightly different than to conventional single phototherapy (described above). Not only is TH exposed to lamps emitting blue light, he is also wrapped in a fibre optic Biliblanket. 21 This involves a light generator, which produces blue or white light of varying intensities and is connected to a light-permeable fabric via a fibre optic cable. The fabric is then placed close to, or is directly in contact with the baby’s skin so that the treatment can occur. 21

In terms of evidence based support showing that conventional phototherapy is effective in the treatment of jaundice, a randomised controlled trial (RCT) found that, “…in the 2000-2499g birth weight group (141 infants, serum bilirubin ≥ 171 µmol/L, average 212 µmol/L), phototherapy significantly reduced the proportion of infants with higher maximal serum bilirubin levels compared with no treatment (serum bilirubin ≥ 257 µmol/L: 18.6% with phototherapy v 42.3% with no treatment; P = 0.002)”. 22 Whether TH’s double phototherapy was necessary is another question as another RCT, “found no significant difference between double conventional and single conventional phototherapy”. 23

Although the risks of serious side effects are minimal whilst having phototherapy, babies usually can present with the following: frequent green loose bowels, skin rashes, dehydration if feeding is not regular (approximately every 2 hours, which TH was) and temperature fluctuations (hypothermia and hyperthermia). 24

Obviously double phototherapy will be more costly compared to single phototherapy due to the use of the fibre optic light cables. However, a study has shown that light intensity and the area of light-exposed skin can be increased due to white curtains being hung around the incubator during single phototherpay, via reflection. 20 These low costing curtains safely increased the efficacy of phototherapy, significantly more than single phototherapy and rivalling double phototherapy, and may prove to be useful to neonatal units when budgets are limited. 20

Section D – Psychological and Social Aspects

Epidemiology

A reason why newborn infants are subject to examination, testing and treatment could arguably be due to jaundice. Estimates of the incidence to jaundice are varied due to ethnicity and geography. 25 A study in Britain examined the trends in moderate neonatal hyperbilirubinaemia in Wirral hospital between 1991 and 2001. 26 They found that the incidence of moderate jaundice increased from 2.4/1000 births in 1991 to 5.5/1000 births in 2001 (p<0.0001). 26 It was also found that, "...readmissions for jaundice increased from seven in the first six years of study to 55 in the second five years (p < 0.0001)" showing that neonatal jaundice is on the rise, or that it is now more easily detected in infants. 26

Screening and Disease Prevention

The prevention of kernicterus requires a good screening test for hyperbilirubinaemia. Screening for this can include physical examination, or measuring the amount of bilirubin in the skin or in the serum. 27 A study in Denmark showed that one third of infants with extreme hyperbilirubinaemia were non-Caucasian. 26 Jaundice is not as easily recognised in infants with darker skin pigmentation by nurses or health care workers, so it is important that babies do not leave the hospital undetected to prevent any neurological damage from occurring. 26 Various transcutaneous instruments can be used to measure elevations in bilirubin levels if it is difficult to notice jaundice on examination. An example is the Minolta JM-103, which is easiest to use but has a tendency to be inaccurate when measuring in dark skinned infants as it overestimates bilirubin levels. 27

Psychosocial Aspects

Although common and usually harmless, jaundice in infants can cause stress for the whole family, particularly the mother in TH’s case. As bonding between TH and his mother was limited to approximately two hours a day, and the fact that breastfeeding could not be established after birth may cause TH’s mother some distress, especially with TH being her first child.

It was noted that children born between October and March (which TH was) were at a higher risk of infantile autism. 28 However this is contradicted as it also states that babies conceived by a primiparous woman were less likely to develop infantile autism. 28

Kernicterus must be avoided at all costs as studies have shown that the damage to the neural tissue can lead to an increased risk of disorders of psychological development. Although jaundice is relatively common in infants and the methods of treatment have a high efficacy and efficiency, kernicterus although rare, still presents itself in undetected children. A good screening programme and immediate treatment is a straightforward way to tackle neonatal jaundice and to make sure that a relatively harmless condition does not manifest itself in the baby.