Comparison of the treatment effects of methoxamine and combining methoxamine with atropine infusion to maintain blood pressure during spinal anesthesia for cesarean delivery: a double blind randomized trial.

Hypotension is a common complication of spinal anesthesia for cesarean delivery. Atropine is a vagus nerve blocker that can antagonize vagus excitation to mitigate the reflex bradycardia. We aimed to assess the effect of methoxamine-atropine therapy in treating spinal anesthesia hypotension for cesarean section.This is a double-blind randomized controlled study. Women under spinal anesthesia for elective caesarean delivery received boluses of methoxamine 2 mg alone (Group M, n = 40), or with addition of atropine 0.1 mg (Group MA1, n = 40), atropine 0.2 mg (Group MA2, n = 40) or atropine 0.3 mg (Group MA3, n = 40) upon a maternal systolic pressure ≤ 80% of baseline. The primary endpoint was systolic blood pressure and the secondary endpoints were maternal heart rates, instant neonatal heart rates, umbilical artery pH and umbilical artery base excess.Changes in systolic blood pressure were similar among the four groups. The incidences of bradycardia in groups M and MA1 were significantly higher than those in group MA2 and MA3. The fetal heart rates after delivery in groups MA2 and MA3 were higher than those in group M and MA1 but within the normal range. The acid-base status had no difference in the four groups.Methoxamine-atropine combination has a similar efficacy to methoxamine alone but has an increased hemodynamic stability and a less adverse effect occurrence.