Effects of intraoperative low-dose esketamine on postoperative pain after vestibular schwannoma resection: A prospective randomized, double-blind, placebo-controlled study

Aims Esketamine may reduce acute postoperative pain in several settings. However, the effects of low-dose esketamine on postoperative pain after vestibular schwannoma (VS) resection with propofol/remifentanil total intravenous anaesthesia (TIVA) are unclear. The aim of this study is to observe the effects of intraoperative low-dose esketamine on postoperative pain after vestibular schwannoma resection. Methods This single-centre, randomized, placebo-controlled, double-blind trial included 90 adults undergoing VS resection via the retrosigmoid approach with TIVA. The patients were randomly allocated to two groups: esketamine or control (n = 45 in each group). Patients received low-dose esketamine (0.2 mg/kg) or a similar volume of normal saline after dural closure. The primary outcome was the pain score during movement (gentle head movement) at 24 h postoperatively. Secondary outcomes included recovery time, bispectral index (BIS) values and haemodynamic profiles during the first 30 min after esketamine administration, and adverse effects. Results Low-dose esketamine did not reduce pain scores at rest (P > .05) or with movement (P > .05) within the first 24 h after surgery. Esketamine moderately increased BIS values for at least 30 min after administration (P < .0001) but did not affect heart rate (P = .992) or mean arterial blood pressure (P = .994). Esketamine prolonged extubation time (P = .042, 95% confidence interval: 0.08 to 4.42) and decreased the effect-site concentration of remifentanil at extubation (P = .001, 95% confidence interval: -0.53 to -0.15) but did not affect the time to resumption of spatial orientation. Postoperative nausea and vomiting rates did not differ between groups, and no hallucinations or excessive sedation was observed. Conclusion Intraoperative low-dose esketamine did not significantly reduce acute pain after VS resection with propofol/remifentanil TIVA. However, BIS values increased for at least 30 min after esketamine administration.