Effect of Phenylephrine in Low Birth Weight (LBW) neonates following spinal anaesthesia
Abstract Number: 202
Abstract Type: Original Research
Introduction: The use of phenylephrine is well established to prevent hypotension during elective caesarean section under spinal anaesthesia 1. Although there is a theoretical risk of uterine artery vasoconstriction this does not seem to result in acidaemia in the healthy neonate 1. However the LBW fetus (2500g) is particularly susceptible to adverse changes in uteroplacental blood flow and we wished to investigate this.
Method: Retrospective case notes review of 50 parturients with neonatal birth weight <2500gm in grade 3 and 4 caesarean sections to identify effects of anaesthesia and vasopressor use on umbilical cord gases and apgar score.
Results: Vasopressor was not needed in 16% of cases.The lowest base deficit (-8.5) and pH (7.18) was noted in a neonate with congenital abnormalities complicated by preclampsia.
Discussion: A pH of ≥7.2 and a base deficit of -10-0mEql.-1 has been accepted as normal1.Our group of neonates had a mean arterial pH of 7.34 and a mean base deficit of -1.6. The use of Phenylephrine was not associated with abnormal blood gases at delivery of the LBW babies, probably due to the brief duration of vasopressor use prior to baby delivery 2 and may also be due to reduced aortacaval compression 2. This audit supports the use of phenylephrine during spinal anaesthesia in LBW babies.
References:1.Ngan Kee WD, Khaw K.S, Ng FF Comparison of phenylephrine infusion regimens for maintaining maternal blood pressure during spinal anaesthesia for caesarean section. BJA, 2004; 92: 469-74
2.F.Reynolds, P.T.Seed, Anaesthesia for Caesarian section and neonatal acid-base status:a meta analysis. Anaesthesia, 2005; 60: 636-53.