Background: Phenylephrine use has been recommended over ephedrine for the management of hypotension after spinal anesthesia for elective caesarean section. The evidence for this is rather limited because in previous trials, pH was significantly lower after ephedrine, but absolute values were still within normal range. We pooled the available data to define maternal and neonatal effects of the two vasopressors.
Methods: Literature was identified by a systematic search. Hypotension, hypertension, and bradycardia of the mothers, fetal acidosis defined as a pH < 7.20, and the continuous variables base excess (BE) and arterial pCO(2) of the neonates were recorded. Meta-analysis using the random effects model was performed, and the weighted mean difference (WMD) or risk ratio (RR), and 95% confidence interval (95% CI) were calculated.
Results: The criteria for eligibility were fulfilled by 20 trials including 1069 patients. The RR of true fetal acidosis was 5.29 (95%CI 1.62-17.25, ) for ephedrine vs. phenylephrine (P = 0.006). BE values after ephedrine use were significantly lower than after phenylephrine (WMD -1.17; 95% CI -2.01 - -0.33). Umbilical artery pCO(2) did not differ. Mothers treated with ephedrine had a lower risk for bradycardia (RR 0.17; 95%CI 0.07-0.43; P = 0.004). No differences between vasopressors were observed for hypotension and hypertension.
Conclusions: Our analysis could clearly demonstrate a decreased risk of fetal acidosis associated with phenylephrine use. In addition with our findings for BE, this suggests a favorable effect of phenylephrine on fetal outcome parameters. The mechanism of pH depression is not related to pCO(2) .
© 2012 The Authors. Acta Anaesthesiologica Scandinavica © 2012 The Acta Anaesthesiologica Scandinavica Foundation.