Summary of findings for the main comparison. Supplemental IV crystalloid compared to control IV crystalloid volume for postoperative nausea and vomiting.
| Supplemental IV crystalloid compared to comparator IV crystalloid volume for preventing postoperative nausea and vomiting. | |||||
| Patient or population: participants aged 6 months or older undergoing surgical procedures under general anaesthesia Setting: surgical centres in North America, South America, Europe, Africa, and Asia Intervention: perioperative administration of IV crystalloid volume larger than that received by the comparator group Comparator: perioperative administration of an IV crystalloid volume smaller than that received by the intervention group | |||||
| Outcome | Illustrative comparative risks* (95% CI) | Relative effect (95% CI) | № of participants (studies) | Certainty of the evidence (GRADE) | |
| Assumed risk | Corresponding risk | ||||
| Risk with comparator IV crystalloid | Risk with supplemental IV crystalloid | ||||
| Risk of PON, defined as the presence of subjective nausea, reported dichotomously or based on a study‐defined dichotomous threshold on a continuous scale such as a VAS | Cumulative events, explicitly reported for the entire study period | RR 0.62 (0.51 to 0.75) | 1766 (18 RCTs) | ⊕⊕⊕⊝ moderate1 | |
| 482 per 1000 | 183 fewer per 1000 (120 to 236 fewer) |
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| Early events, occurring in the first 6 hours postoperatively | RR 0.67 (0.58 to 0.78) | 2310 (20 RCTs) |
⊕⊕⊕⊝ moderate1 | ||
| 307 per 1000 | 101 fewer per 1000 (68 to 129 fewer) | ||||
| Late events, occurring at the time point closest to or including 24 hours postoperatively | RR 0.47 (0.32 to 0.69) |
1682 (17 RCTs) |
⊕⊕⊕⊝ moderate1 | ||
| 187 per 1000 | 99 fewer per 1000 (58 to 127 fewer) |
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| Risk of POV, reported dichotomously by any discrete episodes of vomiting | Cumulative events, explicitly reported for the entire study period | RR 0.50 (0.40 to 0.63) | 1970 (20 RCTs) | ⊕⊕⊕⊝ moderate1 | |
| 295 per 1000 | 147 fewer per 1000 (109 to 177 fewer) |
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| Early events, occurring in the first 6 hours postoperatively | RR 0.56 (0.41 to 0.76) | 1998 (19 RCTs) |
⊕⊕⊕⊝ moderate1 | ||
| 106 per 1000 | 47 fewer per 1000 (25 to 63 fewer) |
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| Late events, occurring at the time point closest to or including 24 hours postoperatively | RR 0.48 (0.29 to 0.79) |
1403 (15 RCTs) |
⊕⊕⊕⊝ moderate1 | ||
| 68 per 1000 | 35 fewer per 1000 (14 to 48 fewer) |
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| Risk of requiring pharmacologic treatment for PONV, reported dichotomously as the use of any medication intended to treat nausea or vomiting during the postoperative period | Cumulative events, explicitly reported for the entire study period | RR 0.62 (0.51 to 0.76) | 2416 (23 RCTs) | ⊕⊕⊕⊝ moderate1 | |
| 284 per 1000 | 108 fewer per 1000 (68 to 139 fewer) |
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| Risk of unintended postoperative admission to hospital, reported dichotomously as admission to an inpatient unit of a participant after an intended ambulatory surgical procedure | Cumulative events, explicitly reported for the entire study period | RR 1.05 (0.77 to 1.43) | 235 (3 RCTs) | ⊕⊕⊝⊝ low2 | |
| 288 per 1000 | 14 more per 1000 (66 fewer to 124 more) |
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| Risk of suffering a serious adverse event, reported dichotomously as the occurrence of any of: admission to high‐dependency unit, postoperative cardiac or respiratory complication, or death | Cumulative events, explicitly reported for the entire study period | ‐ | This outcome was not reported for included trials | ‐ | |
| ‐ | ‐ | ||||
| * For all outcomes, the assumed and corresponding risks (and their 95% CI) are based on the proportion of events in the comparator and intervention groups, respectively. CI: confidence interval; PON: postoperative nausea;POV: postoperative vomiting; RR: risk ratio; VAS: visual analogue scale | |||||
| GRADE Working Group grades of evidence High‐certainty: we are very confident that the true effect lies close to that of the estimate of the effect Moderate‐certainty: we are moderately confident in the effect estimate: The true effect is likely to be close to the estimate of the effect, but there is a possibility that it is substantially different Low‐certainty: our confidence in the effect estimate is limited: The true effect may be substantially different from the estimate of the effect Very low‐certainty: we have very little confidence in the effect estimate: The true effect is likely to be substantially different from the estimate of effect | |||||
1Downgraded one level due to risk of publication bias, following inspection of funnel plot.
2Downgraded two levels due to imprecision and inconsistency.