Vasopressor Regimens and Maternal Core Temperature During Cesarean Delivery: A Randomized, Double‑blind,...

Norepinephrine (NE), a vasopressor commonly used during cesarean section, avoids the phenylephrine (PE)-induced decreases in heart rate and cardiac output. Conversely, PE reduces the incidence and severity of maternal shivering and hypothermia during cesarean section. Therefore, before recommending NE as a complete replacement for PE, their effects on maternal core temperature must be compared. This study aimed to determine whether prophylactic infusion of NE is non-inferior to PE in maintaining maternal core temperature.

One hundred and forty eligible women scheduled for cesarean section under spinal or combined spinal-epidural anaesthesia were randomly assigned to either the NE or PE group. All participants, caregivers, and outcome assessors were blinded. NE (8 μg/mL) or PE (100 μg/mL) was administered intravenously at a fixed rate of 15 mL/h (equivalent to NE 2 μg/min or PE 25 μg/min), starting concurrently with the subarachnoid injection, and continuing until the end of surgery. The primary outcome was postoperative maternal core temperature, with a non-inferiority margin set at 0.2°C.

Postoperative maternal core temperature was non-inferior in the NE group (mean, 36.35°C; 95% confidence interval [CI], 36.28-36.42) compared to the PE group (mean, 36.41°C; 95% CI, 36.34-36.49). The mean difference between the two groups was -0.06°C (95% CI, - 0.16 to 0.04), meeting the criterion for non-inferiority (one-sided p = 0.008). The incidence of bradycardia was significantly lower in the NE group than in the PE group (7.4% vs. 33.8%; p < 0.001). No significant differences were found between the groups in the incidence or severity of shivering, the incidence of hypothermia, or the thermal comfort score.

NE was not inferior to PE regarding its effect on maternal core temperature, providing a rationale for its use during cesarean sections.