Practical Issues in blood transfusion in pediatrics

1. Amount of transfusion to be given: It has been seen that transfusion with PRBC at a dose of 20 mL/kg is well tolerated and results in an overall decrease in number of transfusions compared to transfusions done at 10 mL/kg. There is also a higher rise in hemoglobin with a higher dose of PRBCs.

 2. Properties of RBC products used in neonatal transfusion: a. RBCs should be freshly prepared and should not be more than 7 days old.  This translates into a high 2, 3-DPG concentration and higher tissue extraction of oxygen. 

3.Blood should be of newborn's ABO and Rh group. It should be compatible with any ABO or atypical red cell antibody present in the maternal serum.

4.   Volume and rate of transfusion: 

a. Volume of packed RBC = Blood volume (mL/kg) x (desired minus actual hematocrit)/ hematocrit of transfused RBC 

b. Rate of infusion should be less than 10 mL/kg/hour in the absence of cardiac failure. 

c. Rate should not be more than 2 mL/kg/hour in the presence of cardiac failure. 

d. If more volume is to be transfused, it should be done in smaller aliquots.

▶️ THE FETAL TRAP 🤖

🔹The placenta forms a barrier to the transfer of drugs between the mother and the fetus, but increasing lipid-solubility, decreasing maternal protein binding, decreasing molecular weight, increased materno-fetal concentration gradient and placental blood flow etc will increase the placental transfer of drugs

🔹The relative distribution of the drug across the placenta is represented by Feto-Maternal (F/ M) concentration ratio

🔹Pethidine and diamorphine are both metabolised in the fetus to less lipid-soluble products like norpethidine and morphine respectively, which remain on the fetal side of the placenta. The elimination half-lives of these drugs are also longer in the fetus because of immature hepatic metabolism. This again prolongs its existence in the fetal side.

🔹Lipid solubility of drugs like thiopentone sodium are high; so they cross the placenta easily, and can accumulate as the pH is lower in the fetus

🔹Diazepam is metabolised to less lipid-soluble products. So it can have an F/ M ratio of 2 even one hour after maternal administration.

🔹Local anaesthetic agents are weak bases which are largely UN-IONISED  at physiological pH, and cross the placenta readily. But fetal 'trapping' occurs in severe acidosis, when the molecules become IONIZED in the fetal side.

#pharmacology , #DrugMetabolism ,#PlacentalTransfer , #anesthesia