Xiaoshan Li,1,2,* Shengchao Li,1,2,* Chanyan Xu,1 Huan He,1 Weidong Shao,1 Shuteng Zhan,1,2 Bo Xu1,2 

1Department of Anesthesiology, General Hospital of Southern Theater Command of PLA, Guangzhou, Guangdong, People’s Republic of China; 2The First School of Clinical Medicine, Southern Medical University, Guangzhou, Guangdong, People’s Republic of China

*These authors contributed equally to this work

Correspondence: Bo Xu, Department of Anesthesiology, General Hospital of Southern Theater command of PLA, 111 Liuhua Road, Guangzhou, Guangdong, People’s Republic of China, Email xubo333@hotmail.com

Objective: This research aimed to quantify the impact of low dose of esketamine on BIS and validate the feasibility of closed-loop TCI system based on the new BIS baseline with low dose of esketamine.
Methods: This study consisted of two phases. The first phase was to quantify the impact of a low dose of esketamine (0.2mg kg− 1 bolus, 5μg kg− 1 min− 1 infusion for 30min) on BIS and establish a new BIS baseline for propofol-remifentanil general anesthesia. The second phase was used to validate the feasibility of closed-loop TCI system based on the new BIS baseline. One hundred and eleven patients were randomly and equally assigned to three groups (group A: adjusted group, group N: non-adjusted group and group C: control group). After administering a low dose of esketamine, group A adjusted drug dosage based on new BIS baseline, while group N based on the original BIS baseline of 50, group C adjusted drug doses based on the original baseline of 50 without esketamine. Main outcome was controller performance (% time within± 10units of the BIS setpoint). Secondary outcomes were drug consumption, occurrence of adverse events such as intraoperative awareness, treatment of hemodynamic changes and postoperative recovery quality.
Results: In the first phase, after administering a low dose of esketamine, the BIS increased from 49.9± 4.5 to 59.6± 6.0, p< 0.01. In the second phase, the controller performance in group A and N were within the range of high-performance systems, and both were equivalent with control group. Group A showed lower consumption of propofol compared to control group (5.58± 1.12 vs 6.69± 1.36 (mg·kg− 1·h− 1), p< 0.05). There was no difference in adverse events such as intraoperative awareness, recovery assessment and postoperative VAS, PONV and shivering, QoR-15 assessment after adjusting the BIS baseline.
Conclusion: It is feasible to operate the closed-loop TCI system based on the adjusted BIS baseline in the presence of low dose of esketamine.

Keywords: esketamine, new BIS baseline, EEG, closed-loop controlled system, depth of anesthesia