INCREMENTAL SPINAL ANAESTHESIA FOR ELECTIVE CAESAREAN SECTION: MATERNAL AND FETAL HAEMODYNAMIC EFFECTS

We have performed serial haemodynamic investigations in 20 womenundergoing elective Caesarean section under continuous spinalanaesthesia with a 32-gauge catheter with 0.5% heavy bupivacaine.Cardiac output was measured by Doppler and cross-sectional echocardiographyat the aortic valve. Doppler flow velocity waveforms were recordedalso from the umbilical artery. A block to 74 or above was achievedin all patients. The median dose of 0.5% bupivacaine administeredwas 2.0 ml (range 1.5–4.5 ml). Mean cardiac output increasedfrom 7 to 8 litre min^-1 after preloading with Ringer lactatesolution 1.5 litre and then remained unchanged after injectionof bupivacaine. Two subjects developed hypotension, althoughmean values of arterial pressure and umbilical artery pulsatilityindex did not change. The median umbilical artery pH was 7.27(range 6.98–7.32) and there was a significant correlationbetween pH and the maximum percentage decrease in cardiac output.The results suggest that continuous spinal anaesthesia is associatedwith greater haemodynamic stability than single bolus spinalinjection. (Br. J. Anaesth. 1993; 70: 634–638)