A randomised comparison of the effects of low-dose spinal or general anaesthesia on umbilical cord blood gases during caesarean delivery of growth-restricted foetuses with impaired Doppler flow

Abstract

Hypotension following spinal anaesthesia for caesarean delivery may decrease uteroplacental perfusion and produce foetal acidosis. The optimal anaesthetic technique for mothers with foetal growth restriction and impaired Doppler flow is unclear. To compare the effects of low-dose spinal anaesthesia and general anaesthesia on neonatal outcome and maternal haemodynamics. Prospective, randomised clinical trial. Tertiary care hospital. Forty pregnant women with foetal growth restriction and impaired Doppler flow scheduled for elective caesarean delivery. The women were allocated randomly to receive a low-dose spinal anaesthetic (8-mg hyperbaric bupivacaine 0.5% with fentanyl 20 μg) or standard general anaesthesia for elective caesarean delivery. SBP was maintained between 80 and 100% of baseline using bolus doses of phenylephrine. The total duration of hypotension, dose of phenylephrine used and any incidence of hypotension, nausea or vomiting were recorded. The primary outcome variable was arterial and venous umbilical cord base deficit. Neonatal outcome and maternal haemodynamics were analysed as secondary endpoints. The mean umbilical artery pH was significantly lower in the low-dose spinal anaesthesia group than in the general anaesthesia group (7.23 ± 0.06 vs. 7.27 ± 0.04, P = 0.01). Cord base deficit was similar in the two groups. Higher partial pressures of oxygen occurred in the general anaesthesia group (20.9 ± 6.5 kPa) than in the low-dose spinal anaesthesia group (13.6 ± 6.1 kPa, P = 0.001). No difference was observed between groups in 1 and 5-min Apgar scores. There appeared to be a greater need for immediate resuscitation of neonates in the general anaesthesia group, but the difference was not statistically significant (P = 0.51). Low-dose spinal anaesthesia was associated with hypotension of short duration (0.7 ± 1.1 min). In this study, there was no difference in umbilical cord base deficit between the groups. Larger studies would be required to assess whether the mode of anaesthesia influences the incidence of clinically important neonatal acidosis in neonates with foetal growth restriction.