Whenever I study an interesting topic in Obstetrics and Gynaecology,I use this blog to share the information.
I checked the facts as much as I can.l will link to the relevant documents and give the references whenever possible.Please be kind enough to make comments.
I hope this blog is also useful for the MRCOG Exam(members of Royal college of Obstetricians & Gynaecologists).
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Why it is important to recognise and treat neonatal jaundice?
Bilirubin is toxic to the brain. Uncojugatedbilirubin is lipid soluble but conjugated bilirubin is water soluble.
Bilirubin is prevented from entering the brain by blood brain barrier under normal circumstances.However the blood brain barrier isn’t well developed in the newborn.Uncojugated bilirubin(lipid soluble) could cross to the newborn and would cause encephalopathy.(Kernicterus)
Fetal bilirubin is excreted via placenta and is cleared by maternal liver. Once delivered baby’s liver should take over.
Causes of neonatal jaundice could be broadly categorisedas
(i)prehepatic(excessibiliruvebinproduction
(ii)intrahepatic(interference with conjugation)
(iii)posthepatic(excrreductedion)
Examples :
(A) Prehepaticprehepatic:haemolyticanaemia-Rhesus incompatibility/ABO incompatibility
(B) Intrahepatic:prematurity-liver enzymes system is immature to handle the conjucation
(C) Post hepatic:Biliary atresia,Choledochal cyst
Pharmacokinetics
Phenytoin is poorly absorbed from the intestine.[1]
It is metabolised in the liver.[2]
The half life of phenytoin at low doses (giving subtheraputic concentrations) is 6-24 hours.[3]It increases to 20-60 hours at higher doses.
Phenytoin is administered orally or by intravenous injection.[4]
Phenytoin sodium may be given by slow intravenous injection, with ECG monitoring, followed by the maintenance dosage. Intramuscular use of phenytoin is not recommended (absorption is slow and erratic).[5] Fosphenytoin is a water soluble pro-drug of phenytoin which can be administered by intramuscular injection.
Magnesium sulphate is superior to phenytoin for the prevention of eclampsia in hypertensive pregnant women.[6]
Phenytoin can cause fetal hydantoin syndrome. The following are the features of fetal hydantoin syndrome[7]
(i) ocular hypertelorism (ii)broad nasal bridge
(iii) low set abnormal ears (iv)cleft lip and palate
(v) hypoplasia of distal phalanges (vi)micro - brachycephaly
Hirsutism is side effect of phenytoin. Phenytoin could also cause folate deficiency and this is why epileptic patients needs folic acid in a higher dose(5 mg).
