Intravenous methadone for pain management in cardiac surgery: a randomised controlled trial with plasma concentration analysis*
Bibliographic record
Abstract
Summary Introduction Postoperative pain after cardiac surgery remains significant despite the administration of opioids. Methadone may improve pain control and decrease the need for postoperative opioids. Randomised controlled trials, however, are limited and the effects of cardiopulmonary bypass on methadone pharmacokinetics are unclear. The aims of this study were to compare methadone and morphine in cardiac surgery, measuring methadone concentrations and correlating them with pain control. Methods Patients undergoing cardiac surgery that required cardiopulmonary bypass were allocated randomly to receive either 0.2 mg.kg ‐1 methadone or 0.2 mg.kg ‐1 morphine (based on actual body weight, maximum 20 mg for both drugs). Postoperative pain was assessed at 15 min and 8 h, 12 h, 24 h, 48 h and 72 h after tracheal extubation, by analysis of morphine consumption and pain scores. Opioid‐related adverse events were evaluated. Postoperative blood samples were collected for 96 h to measure plasma methadone concentrations. Results In total, 80 patients were analysed (40 allocated to the methadone group, 40 allocated to the morphine group). Patients allocated to the methadone group had significantly reduced 24‐h and total postoperative morphine requirements compared to those allocated to the morphine group (median (IQR [range]) 9 (5–16 [0–40]) mg vs. 24 (17–43 [4–54]) mg (p < 0.001) at 24 h and 35 (23–52 [5–66]) mg vs. 11 (7–20 [0–44]) mg (p < 0.001) total). Patients allocated to the methadone group had lower pain scores at rest (β ‐2.24, standard error 0.49, p < 0.001) and on coughing (β ‐2.16, standard error 0.50, p < 0.001). There was no difference in the incidence of opioid‐related adverse effects between the two groups. Plasma methadone concentration decreased during cardiopulmonary bypass but remained above the minimum effective analgesic concentration for approximately 24 h after administration (mean (SD) 51 (24.7) ng.ml ‐1 at baseline to 30 (10.7) ng.ml ‐1 at 24 h). Discussion Intra‐operative methadone reduces postoperative analgesia requirements without increasing the incidence of opioid‐related adverse events.
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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 | 0.006 | 0.008 |
| Meta-epidemiology (narrow) | 0.002 | 0.001 |
| Meta-epidemiology (broad) | 0.006 | 0.004 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.002 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.003 | 0.002 |
| Insufficient payload (model declined to judge) | 0.007 | 0.001 |
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".