Background: S-ketamine is the S-enantiomer of ketamine, which exerts anesthetic and analgesic effects through noncompetitive antagonism of N-methyl-D-aspartate (NMDA) receptors.
Objective: We aimed to define the relative risk of post-abdominal surgery pain in adults who were administered perioperative S-ketamine.
Study design: Systematic review and meta-analysis.
Methods: Two reviewers independently screened the articles from the titles and abstracts based on our eligibility criteria, evaluated the risk of bias by using the Cochrane Collaboration Risk of Bias tool in randomized controlled trials, and extracted the data from the included studies according to a prespecified protocol; any disagreements were solved by consultation. The level of certainty for the main results were evaluated according to the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) system.
Results: Of the 1,621 studies identified, 9 studies were included; they were published from 2004 through 2022. Only one study involved epidural anesthesia, whereas the other 8 studies included general anesthesia. The pain at rest scores at 4 and 24 hours post-abdominal surgery were significantly lower in the S-ketamine group, respectively. However, there was no significant difference between the 2 groups in the pain at rest scores at 48 hours post-abdominal surgery. S-ketamine infusion reduced pain during movement 24 hours post-abdominal surgery, but not at 48 hours, respectively. The incidence of postoperative nausea and vomiting, as well as psychotomimetic adverse effects post-abdominal surgery were similar between the 2 groups, respectively. A subgroup analysis revealed that the pain at rest score at 4 hours post-abdominal surgery in patients in the intraoperative use group was remarkably reduced, compared with the patients who received S-ketamine perioperatively. Otherwise, the pain at rest score at 24 hours post-abdominal surgery in the perioperative use group was significantly reduced versus intraoperative use group.
Limitation: The number of trials included was small. The remarkable heterogeneity found in the pooled results at each time point post-abdominal surgery might affect the credibility of the results.
Conclusions: S-ketamine is effective in reducing the early postoperative pain of patients who received abdominal surgery, and may not increase the incidence of postoperative complications.
Keywords: abdominal surgery; intravenous; meta-analysis; pain scores; postoperative pain; randomized controlled trial; systematic review; S-ketamine.