EFFECT OF ADRENALINE ON EXTRADURAL ANAESTHESIA AND PLASMA BUPIVACAINE CONCENTRATIONS DURING CAESAREAN SECTION

The effect of adrenaline on the efficacy of extradural blockand plasma bupivacaine concentrations was investigated in womenundergoing elective (n = 40) and emergency (n = 40) Caesareansection. Patients were randomly allocated within these two groupsto receive 0.5% bupivacaine 20 ml either plain or with adrenaline1 in 200000, as a single fractionated extradural injection.The elective plain group needed significantly more supplementaryanalgesia compared with the other three groups (P <0.05).In the elective group, plasma bupivacaine concentrations weresignificantly lower in the subgroup receiving extradural adrenalinethan in the plain subgroup. This effect was not observed whencomparing only those who received bupivacaine 100 mg. In theemergency group, there were no significant differences in plasmabupivacaine concentrations between the plain and adrenalinesubgroups. Maximum plasma concentrations correlated significantly(P < 0.0001) with dose of bupivacaine (mg kg^–1). Itis concluded that extradural adrenaline does not usefully reducesystemic absorption of 0.5% bupivacaine, but may improve itsefficacy in extradural anaesthesia for elective Caesarean section.