Association between intraoperative phenylephrine administration and umbilical artery pH in women with hypertensive disorders of pregnancy: a retrospective cohort study

In healthy pregnant women undergoing Cesarean section, treatment of post-spinal hypotension (PSH) with phenylephrine is reportedly more efficacious than ephedrine in preventing a decline in umbilical artery pH (UApH), which is an indicator of fetal acidosis. However, phenylephrine has the potential to reduce placental blood flow and consequently decrease UApH in women who develop hypertensive disorders of pregnancy (HDP), due to decreased cardiac function and placental vascular abnormalities. We aimed to verify the association between decreased UApH and phenylephrine administered before delivery to treat PSH in women with HDP.

This single-center retrospective cohort study was conducted between April 2008 and October 2016 by assessing the records of pregnant women with confirmed or suspected HDP who underwent Cesarean section under spinal anesthesia. The association between phenylephrine and the primary endpoint of decreased UApH was investigated using logistic regression analysis and propensity score matching.

In the original cohort of 107 pregnant women with HDP, neither univariate nor multivariate analysis indicated a significant association between phenylephrine treatment and decreased UApH [crude odds ratio (OR) = 2.26; 95% confidence interval (CI) 0.75–6.77; P = 0.14], (adjusted OR = 1.80; 95% CI 0.55–5.93; P = 0.33). Thirty patients each who were not treated with phenylephrine (control group) and were treated with phenylephrine (phenylephrine group) were matched by propensity score analysis. UApH [median (interquartile range)] was not significantly different between control and phenylephrine groups [7.30 (7.25–7.35) vs. 7.27 (7.25–7.30); P = 0.14].

Intraoperative phenylephrine administration to treat PSH in women with HDP was not associated with decreased UApH.