Results
The CONSORT flow diagram of this trial is shown in Figure 1. Patients were recruited between December 10, 2021 and May 25, 2022. Of the 67 patients who underwent thyroid surgery and were screened for suitability, 7 were excluded, of whom 2 had uncontrolled hypertension and 5 declined to participate. Ultimately, 60 patients were enrolled and randomized, all of whom were followed up until the end of the study.
Table 1 shows patient and surgical characteristics. There were no significant differences between groups in age, sex distribution, BMI, ASA physical status, type of surgery, or duration of surgery (Table 1).
Compared with the Group CON, perioperative sufentanil consumption was significantly reduced in Group KET (33. 7 ± 5.1 μg vs. 24.6 ± 3.1 μg, mean difference, 9.1; 95% confidence interval, 6.9–11.3, P<0.001). There were no significant differences between the two groups in regards of intraoperative remifentanil consumption (1118.5 ± 294.9 μg vs. 1045.8 ± 302.0 mg, P = 0.349) or propofol consumption (513.50 ± 210.0 mg vs. 476.2 ± 170.1 μg, P = 0.453) (Table 2).
Postoperatively, five patients in Group CON and no patients in Group KET reported NRS scores >3; however, this did not reach significance. None of the patients received rescue analgesia in the PACU. In the ward, one patient in Group CON required analgesic therapy, and diclofenac lidocaine was administered by the attending surgeon. There were no significant differences between groups with regard to the time to extubation or RASS score 30 min postoperatively. The incidence of postoperative nausea was 3.3% in Group CON and 13.3% in Group KET, whereas the incidence of postoperative vomiting was 6.7% in Group CON and 10.0% in Group KET; however, these differences were not statistically significant. Psychotomimetic side effects were not significantly different between groups. The most common side effect was dizziness (CON: 30.0% vs. KET: 27%, P = 0.774). One patient in Group KET experienced transient diplopia, which resolved spontaneously over time. None of the patients experienced hallucinations or nightmares, and none reported intra-operative awareness after surgery (Table 3).
Patients in Group KET experienced lower NRS pain scores at rest and coughing than those in Group CON at all timepoints in the first 24 h postoperatively (Figure 2). . Pain scores in 3 months postoperatively were equally low and comparable between the two groups (Table 3).
Preoperative sleep quality scores were comparable between the two groups. During the night of surgery, patients in Group KET experienced higher sleep quality (2 [1, 2]) than those in Group CON (3 [1, 4]) (P = 0.043). When we compared the intragroup values using the Wilcoxon matched-pairs test, patients in Group CON reported significantly poorer sleep quality when compared with the preoperative value (preoperative value, 1 [1, 2] vs. postoperative value, 3 [1,4], P = 0.004); however, there was no significant difference between the preoperative and postoperative values in Group KET in terms of sleep quality (preoperative quality, 2 [1,4] vs. postoperative quality, 2 [1,2], P = 0.347, Table 3).
There were no significant differences in MAP between groups at any timepoints. Patients in Group KET exhibited a higher HR 10 min after injection of esketamine, while HR values were similar at other timepoints between groups (Figure 3). The incidences of hypotension and bradycardia in Group CON (13.3% and 10.0%, respectively) were both comparable with those in Group KET (13.3% and 0%, respectively), and none of the patients exhibited hypertension or tachycardia.