Objective To explore the effects of esketamine and propofol on post-induction hypotension (PIH) for endotracheal intubation without muscle relaxants.

Methods We enrolled 188 adult patients undergoing thyroidectomy under intraoperative electromyographic monitoring in Zhongshan Hospital, Fudan University from November 8th, 2021 to February 18th, 2022. Patients were randomly allocated into esketamine group (n＝94, esketamine 1 mg/kg, remifentanil 4 μg/kg and propofol 0.5 mg/kg) and propofol group (n＝94, propofol 2.5 mg/kg and remifentanil 4 μg/kg). The primary outcome was the occurrence of PIH before intubation (T1, 30 s after all induction agents injection). Mean arterial pressure (MAP) was recorded before intubation (T1) and at 1-minute interval for 5 minutes (T2-T6) after endotracheal intubation.

Results Patients in both groups had comparable clinical characteristics. The incidence of PIH before intubation was 31.5% in esketamine group and 79.8% in propofol group (P < 0.001). MAP significantly decreased compared with the baseline in both groups (F＝256.78, P < 0.001). The decrease of MAP in propofol group was greater than that in esketamine group (F＝17.53, P < 0.001). Excellent intubation conditions were 31 (33.7%) in esketamine group and 88 (93.6%) in propofol group, while good intubation conditions were 61 (66.3%) in esketamine group and 6 (6.4%) in propofol group (P < 0.001).

Conclusions Induction with esketamine 1 mg/kg, remifentanil 4 μg/kg and propofol 0.5 mg/kg can reduce the incidence of PIH with clinically acceptable intubation condition for endotracheal intubation without muscle relaxants.