Intraoperative low-dose ketamine for postoperative pain outcomes in opioid-naïve patients: A systematic review and meta-analysis.
Jiaojiao Sun, Xiuqing Qi, Peng Zhang
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In 30 seconds
This pre-registered systematic review and meta-analysis assessed intraoperative low-dose ketamine for postoperative pain in opioid-naïve patients, pooling 18 randomised controlled trials with 1339 participants. Compared with placebo, ketamine was associated with lower resting pain scores at 1, 6 and 24 hours, reduced opioid consumption at 24 hours but not 48 hours, and less need for rescue analgesia. The rescue-analgesia risk ratio was 0.31 (95% CI 0.23 to 0.41; moderate-certainty evidence). Overall, the authors describe potential benefit mainly in the early postoperative period, with caution warranted because of heterogeneity and low-certainty evidence.
Key findings
- Resting pain scores were lower with ketamine at 1 h (SMD = -1.51, 95% CI - 2.25 to -0.77), 6 h (SMD = -0.92, 95% CI - 1.51 to -0.23), and 24 h (SMD = -0.62, 95% CI - 0.92 to -0.31).
- Opioid consumption was lower at 24 h (SMD = -1.69, 95% CI - 3.22 to -0.15), but not at 48 h (SMD = -0.19, 95% CI - 0.46 to 0.07).
- The risk of requiring rescue analgesia was lower with ketamine (RR = 0.31, 95% CI 0.23 to 0.41; moderate certainty).
Why it matters
The findings suggest that intraoperative low-dose ketamine may improve early postoperative analgesia and reduce rescue analgesia use in opioid-naïve patients. However, the apparent opioid-sparing effect was not sustained at 48 hours, and the authors consider the clinical benefit at 24 hours limited. The evidence therefore informs expectations about timing and durability of benefit rather than establishing a definitive effect.
What to keep in mind
The review reports substantial heterogeneity, and certainty was low or very low for several outcomes. The pooled findings therefore require cautious interpretation.