Cerebral oxygen saturation monitoring: a comparative study between bolus doses of ephedrine and phenylephrine in elective cesarean section

Background Maternal hypotension is suspected to occur during cesarean section, especially under spinal anesthesia. Ephedrine and phenylephrine are the most common drugs used to treat this phenomenon. Phenylephrine has been claimed to decrease cerebral oxygen saturation (ScO2) under general anesthesia but it is unclear whether it has the same effect in spinal anesthesia. Patients and methods A randomized double-blinded study was conducted that included 42 pregnant women for elective cesarean section under spinal anesthesia. A bolus dose of ephedrine (10 mg) or phenylephrine (0.1 mg) was given for treatment of hypotension. Frontal lobe oxygenation (ScO2), mean arterial blood pressure (MAP), and heart rate (HR) were recorded, besides standard monitoring of other vitals. Results There was a significant decrease in left ScO2 in the phenylephrine group after bolus treatment in response to hypotension when compared with the ephedrine group (rate of change –6 ± 2 vs. +2 ± 1; P 0.001), as well as in right ScO2 (–8.65 ± 0.81 vs. +2.38 ± 0.9; P 0.001). HR was signifi cantly lower in the phenylephrine group than in the ephedrine group after the bolus dose (60 ± 7.3 vs. 71.1 ± 4.8; P 0.001). There was no significant difference between the two groups as rega rds fetal outcome. Conclusion Bolus dose of phenylephrine for treatment of spinal anesthesia-induced hypotension in elective cesarean section causes more decrease in ScO2 and maternal HR in comparison with a bolus dose of ephedrine, but both are effective in maintaining mean arterial blood pressure, with satisfactory fetal outcome.