Jaundice occurs when bilirubin accumulates in the extravascular fatty tissues (skin and brain). Jaundice in the newborn is common, occurring in over two-thirds of term infants and even more frequently in the preterm infant. In order to provide informed care for a jaundiced baby and parents it is important to have an understanding of bilirubin metabolism. There are four stages involved in bilirubin metabolism. Alterations at any of these stages can result in jaundice (Table 64.1).
Jaundice is classified as physiological or pathological. Physiological jaundice is normal. It does not present on day 1. Serum bilirubin (SBR) levels will peak by day 4 and reduces by day 14. Pathological jaundice, on the other hand, should raise concern and always requires further investigation. Pathological jaundice can present on day 1 or it can be prolonged, persistent after day 14 in the term infant or day 21 in the preterm infant. Causes of physiological and pathological jaundice can be linked to each stages of metabolism (Table 64.2).
There is controversy in the literature as to how to classify breast milk jaundice. It is important not to imply that breast milk jaundice is harmful, thereby influencing a mother’s choice not to breastfeed. The use of early versus late onset is preferred by many over using the terms physiological or pathological jaundice.
The impact of feeding frequency can be a contributing cause of jaundice in the breastfed baby. Feeding stimulates the gastrocolonic reflex and increases intestinal motility, clearance of meconium and conjugated bilirubin from the gut. Mothers do not initially produce sufficient quantities of milk for the demand-fed infant unlike bottle-fed infants who are given calculated amounts at regular intervals. Small-volume feeds result in less frequent and smaller stools, increasing enterohepatic shunting, and a caloric deficiency, increasing circulating free fatty acids which can displace unconjugated bilirubin from albumin.
Breast milk inhibits the development of bacterial gut flora and the making of urobilinogen. Breast milk contains high levels of β-glucuronidase, increasing the cleaving of conjugated bilirubin/urobilinogen back to unconjugated bilirubin. As the breast-fed baby is more efficient at absorption, the overall result is an increase in enterohepatic shunting.
High levels of unconjugated bilirubin can result in damage to the basal ganglia in the brain causing kernicterus and damage to the 8th cranial nerve, resulting in sensorineural hearing loss. Assessment and management is essential to prevent these complications. National guidelines are available and include treatment thresholds/graphs and algorithms on investigations, management of jaundice, including phototherapy and exchange transfusions.
Jaundice can be assessed by examining the skin and eyes. The sclera or ‘white’ of the eye and skin when pressed will be yellow. Jaundice develops in a ‘head to tail’ direction – first the head, then body and finally the limbs. Jaundice should be quantified and this can be done by transcutaneous devices and blood sampling.
If the underlying cause of jaundice is treatable then this should be treated. It is also important to ensure that the infant’s stages of metabolism are supported by ensuring the baby is given adequate food (glucose is needed for conjugation) and drink (to ensure excretion and minimise enterohepatic shunting). Careful plotting of SBR levels on treatment threshold graphs for the infant’s gestation will indicate the when the baby requires phototherapy or an exchange transfusion. Babies with rapidly increasing SBRs or potentially in need of an exchange transfusion should be cared for on the neonatal unit.
Phototherapy is the usual treatment for neonatal jaundice and it is used to curtail the rise of unconjugated bilirubin therefore preventing kernicterus. Phototherapy simply converts unconjugated bilirubin into photoisomers of bilirubin, which are water soluble and excretable via the liver into the small bowel. The effects of phototherapy are reversible, so when the light is turned off, the bilirubin transforms back to a fat-soluble molecule.
Two types of phototherapy devices are available. They are conventional or fibre optic. The type of light used is determined by the type and levels of jaundice. Multiple lights or devices can be used to manage high SBR levels. Phototherapy must be delivered effectively and safely. Therapeutic phototherapy is dependent upon the colour or wavelength/spectrum used. Blue-green light is most effective. The irradiance or measurement of the light beams used is determined by the quality of lights used and the distance of the light from the baby. Irradiance decreases as the distance2 increases, therefore follow manufacturer’s advice. Maximum skin exposure to the light is important. The baby ideally should just wear eye pads and a ‘bikini’ nappy. Unless a baby is at risk of an exchange transfusion, phototherapy can be interrupted for care and feeding.
Babies under phototherapy are at risk of a number of potential problems. Eye pads worn to prevent retinal damage can slip and obstruct the baby’s airway causing apnoea. Eyes should be closed prior to applying the eye pads to prevent corneal abrasions and changed daily and if soiled to prevent conjunctivitis. Depending on whether the baby is nursed in an incubator or cot, the baby can develop hypo- or hyperthermia. Conventional phototherapy increases gut transit time and with the increase in radiant heat generated by the light, can increase transepidermal water loss resulting in dehydration, decreased nutrition and weight loss. Phototherapy also causes local histamine release from skin mast cells resulting in a skin rash. Babies under phototherapy tend to be less interested in feeding, providing challenges for the breastfeeding mother. Unlike fibre optic phototherapy, conventional phototherapy creates a barrier and can temporarily increase parent–baby separation.