Tiêu đề 21. Neonatal Jaundice.pdf ✅

THE PEDIATRICS COURSE c 2020 Prints and More. All rights reserved. PRINTS & MORE ACADEMIC TEAM 21. Neonatal Jaundice
1 Neonatal Jaundice Introduction Neonatal jaundice is a common physiologic variant, as up to 60% of term healthy new-borns exhibit some degree of jaundice in the first week of life. Jaundice is a physical examination finding and refers to the yellow discolouration of the skin and sclera caused by bilirubin deposition. In contrast, hyperbilirubinemia refers to a total serum bilirubin measurement of greater than the 95th percentile for age and requires treatment. Clinically, the progression to hyperbilirubinemia can be thought of as a spectrum; on one side of the spectrum is simple jaundice there is yellowing of the skin and sclera without other symptoms. As the bilirubin continues to increase, other symptoms start to occur, such as sleepiness and feeding difficulty. Rarely, hyperbilirubinemia becomes severe (total bilirubin >25mg/dl), which puts neonates at risk for bilirubin induced neurologic dysfunction (BIND) that happens when the bilirubin crosses the blood brain barrier and binds to brain tissue, especially the basal ganglia. Kernicterus, which is also called bilirubin encephalopathy, refers to the neurological syndrome resulting from the neurotoxic effects of unconjugated bilirubin when it crosses the BBB. It causes choreoathetoid cerebral palsy (the dr said he will ask about this, which is a movement disorder caused by damage to the developing brain. This type of cerebral palsy is characterized by abnormal, involuntary movement), sensorineural hearing loss, upward gaze palsy, and intellectual delay. Although infrequent, it has at least 10% mortality and 70% morbidity. Risk factors for kernicterus include rapid rise in bilirubin, prematurity, hypoalbuminemia, sepsis, asphyxia, and acidosis. There are 3 phases a baby who is suffering from kernicterus goes through (illustrated in the figure below):
2 Bilirubin Metabolism Bilirubin is a product of red blood cells breakdown. As red blood cells near their lifespan (which is about 120 days) are phagocytized by macrophages, and hemoglobin is broken up into heme and globin; the globin is further broken down into amino acid, and the heme part is further split into iron and protoporphyrin. Protoporphyrin is then converted into unconjugated bilirubin. Unconjugated bilirubin is lipid soluble, meaning that albumin in the blood binds to it transporting it to the liver where it is taken up by hepatocytes to be converted into conjugated bilirubin by the enzyme uridine glucuronyl transferase, which makes the conjugated bilirubin now water soluble. The conjugated bilirubin is then excreted by the hepatocytes into the gallbladder and duodenum, and once it’s in the intestinal tract, most conjugated bilirubin is excreted in the feces. However, some is recycled back to the unconjugated form by the enzyme beta glucuronidase, and gets reabsorbed into the bloodstream, repeating the cycle all over again (this is called enterohepatic circulation). Prevalence of Neonatal Jaundice ● 75% of term new-borns develop clinical jaundice in the first week of life. ● 80% of preterm infants develop jaundice in the first 2 weeks. ● It is clinically apparent when the total serum bilirubin (TSB) is greater than 5mg/dL. Types of Neonatal Jaundice Bilirubin exists in two main forms in serum: unconjugated bilirubin, which is lipid soluble (able to cross BBB) as mentioned above, and is reversibly bound to albumin, and conjugated bilirubin, which is water soluble and readily excreted via the renal and biliary systems. Iit is nontoxic but reflects hepatobiliary pathology. Jaundice can be classified by age of onset and duration of jaundice into: 1. Early: within 24 hours of life and it always indicates pathology. In cases of early jaundice, always think hemolysis whether it is immune mediated disorders: (ABO incompatibility, and Rh isoimmunisation) or non-immune mediated such as G6PD deficiency. 2. Intermediate: 2 days to 2 weeks, it is the typical most common pattern of presentation and it’s benign and physiologic. However, that doesn't mean you shouldn’t follow up the baby and further investigate. 3. Late: also called prolonged jaundice. It is when the jaundice persists for more than 2 weeks (jaundice persisting after 14 days in term babies or 21 days in preterm babies). In cases of prolonged jaundice, always think of infection, sepsis, hypothyroidism, CF, trisomy 21, breast milk jaundice, and Crigler-Najjar syndrome.