Disposition of propofol at caesarean section and in the postpartum period.

We have compared the pharmacokinetics of a bolus dose of propofol 2 mg kg-1 in eight patients undergoing Caesarean section with those in eight postpartum patients undergoing sterilization by mini-laparotomy. The Caesarean section group had a total body clearance of (median) 31.5 (range 24.4-53.3) ml min-1 kg-1, apparent volume of distribution at steady state 5.10 (2.46-6.61) litre kg-1 and mean residence time 161 (52.3-251) min; values for the post-partum group were 33.8 (21.5-47.2) ml min-1 kg-1, 5.17 (3.47-8.09) litre kg-1 and 163 (92.3-238) min, respectively. The 95% confidence interval for the umbilical venous to maternal venous ratio of propofol at delivery was 0.62-0.86. Plasma protein binding studies showed there was less unbound propofol in maternal plasma (1.28-2.29%) compared with umbilical plasma (2.08-3.88%) (P less than 0.01). Neonatal concentrations of propofol were greater than maternal concentrations at 2 h and were in the range 0.05-0.11 micrograms ml-1 at 4 h.