Analgesic impact of intra‐operative opioids vs. opioid‐free anaesthesia: a systematic review and meta‐analysis
Bibliographic record
Abstract
Summary Opioids are administered peri‐operatively for postoperative analgesia, and intra‐operatively to control the sympathetic response to surgical stimuli, frequently as a surrogate for presumed pain. However, opioid use during surgery is a matter of dispute in contemporary practice and carries the risk of side‐effects such as postoperative nausea and vomiting. This meta‐analysis investigated whether opioid‐inclusive, compared with opioid‐free anaesthesia, would reduce postoperative pain, without increasing the rate of postoperative nausea and vomiting. The electronic databases Medline and PubMed were searched until June 2018. We included trials investigating pain outcomes and comparing any type of intra‐operative opioid administration with placebo injection or no intra‐operative opioid. Most meta‐analyses were performed using a random effects model. We rated the quality of evidence for each outcome. The primary outcome was pain score at rest (analogue scale, 0–10) at two postoperative hours. Our secondary outcomes included the rate of postoperative nausea and vomiting within the first 24 postoperative hours and length of stay in the recovery area. Twenty‐three randomised controlled trials, including 1304 patients, were identified. Pain scores at rest at two postoperative hours were equivalent in the opioid‐inclusive and opioid‐free groups with a mean difference (95% CI ) of 0.2 (−0.2 to 0.5), I 2 = 83%, p = 0.38 and a high quality of evidence. Similarly, there was high‐quality evidence that the rate of postoperative nausea and vomiting was reduced in the opioid‐free group, with a risk ratio (95% CI ) of 0.77 (0.61–0.97), I 2 = 16%, p = 0.03 and high‐quality evidence for a similar length of stay in the recovery area, the mean difference (95% CI ) being 0.6 (−8.2 to 9.3), min, I 2 = 60%, p = 0.90. As there is strong evidence that opioid‐inclusive anaesthesia does not reduce postoperative pain, but is associated with more postoperative nausea and vomiting, when compared with opioid‐free anaesthesia, we suggest that anaesthetists should reconsider their intra‐operative opioid choices on a case‐by‐case basis.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.013 | 0.028 |
| Meta-epidemiology (narrow) | 0.003 | 0.002 |
| Meta-epidemiology (broad) | 0.022 | 0.040 |
| Bibliometrics | 0.006 | 0.006 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.004 | 0.002 |
| Open science | 0.002 | 0.002 |
| Research integrity | 0.003 | 0.002 |
| Insufficient payload (model declined to judge) | 0.004 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".