Neonatal outcomes following phenylephrine or norepinephrine for treatment of spinal anaesthesia-induced hypotension at emergency caesarean section in women with fetal compromise: a randomised controlled study.

BACKGROUND: Norepinephrine is as effective as phenylephrine for management of spinal anaesthesia-induced hypotension. Most of the studies comparing these vasopressors have been conducted in healthy pregnant women undergoing elective caesarean section. In the current study, we tested the null hypothesis that there is no difference in neonatal outcome when phenylephrine or norepinephrine is used to treat spinal anaesthesia-induced hypotension in women undergoing emergency caesarean section for fetal compromise. METHODS: Patients undergoing caesarean section for fetal compromise who developed spinal anaesthesia-induced hypotension were randomised to receive phenylephrine 100 µg or norepinephrine 8 µg for treatment of each hypotensive episode, defined as systolic blood pressure <100 mmHg. Umbilical cord arterial and venous blood samples were obtained for blood gas analysis. The primary outcome measure was umbilical artery pH. RESULTS: One hundred patients (50 in each group) were studied. There was no significant difference in umbilical artery pH between the two groups (mean difference 0.001; 95% CI -0.032 to 0.034). The number of hypotensive episodes, vasopressor boluses required, the incidence of bradycardia, heart rate and blood pressure trends following vasopressor administration, and the incidence of nausea/vomiting were not significantly different between groups. CONCLUSION: Phenylephrine 100 µg and norepinephrine 8 µg were not significantly different in terms of neonatal outcome when administered as intravenous boluses for treatment of spinal anaesthesia-induced hypotension in parturients undergoing emergency caesarean sections for fetal compromise.

A randomised controlled trial of phenylephrine and noradrenaline boluses for treatment of postspinal hypotension during elective caesarean section.

Phenylephrine is currently the vasopressor of choice during elective caesarean section, but it can cause reflex bradycardia. Noradrenaline, a potent α-agonist and weak ß-agonist, may be associated with a lower incidence of bradycardia. However, comparative information is limited. This double-blind randomised controlled trial compared the effects of 100 µg phenylephrine and 5 µg noradrenaline administered as boluses for the treatment of postspinal hypotension during elective caesarean section in women with an uncomplicated singleton pregnancy. Hypotension was defined as a decrease of ≥ 20% from baseline systolic arterial pressure, or an absolute value < 100 mmHg. Ninety women were included in the study. The primary outcome was the incidence of maternal bradycardia < 60 beats.min-1 . There was no difference in the incidence of bradycardia (37.8% with phenylephrine vs. 22.2% with noradrenaline; p = 0.167), number of hypotensive episodes, number of boluses required to treat the first hypotensive episode or reactive hypertension. The total number of boluses used was higher in the phenylephrine group (p = 0.01). Maternal heart rate at 1 min after vasopressor administration was non-significantly lower using phenylephrine vs. noradrenaline (p = 0.034, considering p < 0.01 as statistically significant). The umbilical artery pH was higher using phenylephrine than with noradrenaline (p = 0.034). In conclusion, both vasopressors reversed postspinal hypotension without a statistically significant difference in maternal bradycardia. However, in view of the lower umbilical artery pH when using noradrenaline, further research is warranted to study its placental transfer and fetal metabolic effects.

Randomised double-blind comparison of bolus phenylephrine or ephedrine for treatment of hypotension in women with pre-eclampsia undergoing caesarean section.

Treatment of post-spinal hypotension during caesarean section assumes special concern in pre-eclamptic patients due to a compromised fetoplacental circulation and increased risk of placental hypoperfusion. Phenylephrine and ephedrine are the most commonly used vasopressors, although the best choice is still not clear. We studied 80 pre-eclamptic women with a singleton pregnancy who underwent caesarean section with spinal anaesthesia, and who developed hypotension defined as a decrease in systolic arterial pressure ≥ 20% from baseline or absolute value < 100 mmHg. Women were randomly allocated to receive phenylephrine 50 µg or ephedrine 4 mg boluses for treatment of hypotension. Blood pressure changes following vasopressor administration were similar in both groups, but heart rate remained higher after ephedrine at all time-points. The primary outcome measure of umbilical artery pH was 7.26 (0.11) in the phenylephrine group and 7.25 (0.09) in the ephedrine group (p = 0.86). The incidence of neonatal acidosis (umbilical artery pH < 7.20) was 9 (22.5%) in the phenylephrine group and 11 (27.5%) in the ephedrine group (p = 0.80). Other secondary outcome measures were comparable. In conclusion, phenylephrine 50 µg and ephedrine 4 mg, administered as intravenous boluses to treat post-spinal hypotension during caesarean section in pre-eclamptic patients, resulted in similar fetal acid-base values, were equally effective in treating hypotension and were associated with good maternal and neonatal outcome.