Plasma total and free concentrations of bupivacaine and lignocaine in mother and fetus following epidural administration, singly or together.
Forty six women undergoing elective caesarean section under epidural blockade were given 20 ml of either bupivacaine 0.5% plain (B) or with adrenaline 5 microg/ml (B + A), lignocaine 2% with adrenaline 5 microg/ml (L + A) or a mixture of equal parts of L + A and B + A (BLA). Further doses of the same solution were given at 20 min if necessary. Free and total plasma concentrations of the local anaesthetics were measured in maternal venous plasma 10, 20, 40, 60 and 120 min after the main dose and in umbilical venous plasma at delivery. Protein binding of both drugs was significantly higher in mother than baby. Lignocaine did not affect bupivacaine binding but lignocaine binding was higher in group BLA than L + A. Otherwise the presence of one drug had little effect on the disposition of the other drug in mother or baby. No plasma concentrations were considered toxic. Adrenaline did not reduce maternal C(max) of free bupivacaine and appeared to be associated with increased fetal uptake of bupivacaine.
Fletcher
S
S
Anaesthetic Department, St Thomas' Hospital, London SE1 7EH, UK.
Carson
R
R
Reynolds
F
F
Howell
P
P
Morgan
B
B