No clear fluids after midnight,
does it really help with Prevention of regurgitation and pulmonary aspiration during anesthesia?
research showsThe grade is D. Two randomized trials in healthy elective-surgery patients found that water or clear fluids two to three hours before anesthesia did not worsen gastric volume or pH. Phillips found 22±21 mL versus 19±16 mL in 100 patients; Dalal found less volume with water, 5.5±3.7 mL versus 17.1±8.2 mL, in another 100. Neither was large enough to determine actual aspiration events, giving D with 28 points.
ads claim‘Nothing, including water, after midnight’ treats every elective patient identically. Evidence supports that a small amount of clear fluid two hours before anesthesia did not increase gastric volume in low-risk patients, but it does not authorize ignoring individualized anesthesia instructions.
Useful facts when choosing a product
- Clear water and solid food have different gastric-emptying times and should not be treated as one fasting category.
- The pivotal trials measured gastric volume and pH and were not powered for pulmonary aspiration.
- No duplicate verdict or matching PMID or DOI was found.
Chamgap Semantic Classification Code
Candidate index · review held
P.complete-abstinence-from-clear-fluids-after-midnight-before-elective-surgery.procedural.regurgitation-and-pulmonary-aspiration-during-anesthesia.prevent.UNKProcedures, devices and tests > Complete abstinence from clear fluids after midnight before elective surgery > Procedural > regurgitation and pulmonary aspiration during anesthesia > Occurrence-prevention claim > Unknown
An automated migration candidate, not an issued permanent code; exact claim scope remains under review. This machine-generated migration candidate helps retrieval but is not a permanent assignment. The original verdict ID and URL remain authoritative.
What the research actually shows
Phillips randomized 100 elective-surgery patients to clear fluids or a six-hour fast; the fluid group drank a mean 388 mL in the six hours before surgery and could drink until roughly two hours before anesthesia. Dalal assigned 100 ASA I-II patients to overnight fasting or 150 mL water two hours before surgery, 50 per group. Both sampled gastric volume and pH through a tube. Each trial was under 200 participants, lacked modern registration, and accessible reporting did not establish allocation concealment or a prespecified analysis plan.
Why this is classified as D (28)
Midnight fasting showed no benefit on a surrogate endpoint, while meaningful differences in actual aspiration were not excluded. Small trials and incomplete reporting leave no strength axis, giving D with 28 points.
Counterpoint. This verdict does not mean everyone may drink until surgery. Patient-specific instructions from the anesthesia team take priority.
Rejudgment record. Cross-check applied — We cross-checked randomized counts, gastric-volume and pH results, water dose, and the lack of power for aspiration events in both primary reports.
| Endpoint | S | Surrogate marker - laboratory or imaging measures |
| Replication | R1 | Single confirmatory trial |
| Independence | I1 | Mixed funding sources |
| Effect size | E0 | Null |
| Precision | C0 | The confidence interval leaves room for benefit |
Stored derived and displayed grades match; this is not a current recalculation or validity check (D).
Sub-claim grades by effect
This ingredient is marketed for several effects. A single overall grade blends strong and weak claims together, so each effect is graded separately here. The overall grade reflects the strongest disconfirming or core claim.
| Effect (sub-claim) | Grade | Basis |
|---|---|---|
| Stopping clear water at midnight reduces residual gastric volume. | D | Two randomized trials found no benefit, and one found less volume with water. |
| Stopping clear water at midnight reduces pulmonary aspiration. | D | No aspiration occurred in the trials, but the event was too rare to exclude a meaningful difference. |
Cross-check — AI research and Codex final gate
Evidence Table
| Study | Design | Sample | Funding | Endpoint | Result | Weight |
|---|---|---|---|---|---|---|
| Phillips et al., Br J Anaesth 1993 | Prospective randomized clinical trial | 100 randomized participants | Funding statement was not verified in the accessible source set | Residual gastric volume and pH after induction | Clear fluids 22±21 mL versus six-hour fast 19±16 mL; pH 2.64±1.57 versus 2.26±1.45; no significant difference | Pivotal adult surrogate-endpoint randomized trial |
| Dalal et al., Indian J Anaesth 2010 | Prospective randomized clinical trial | 100 randomized (50 overnight fasting, 50 given 150 mL water) | Source of Support: Nil | Residual gastric volume and pH after induction | Water 5.5±3.7 mL versus overnight fasting 17.1±8.2 mL, significantly lower; pH was similar | Small corroborating trial in the same direction |
Receipt — 2 References
All 2 cited sources were verified for existence at the original page (as of 2026-08-14).
Final verification and publication gate: Codex · Evidence date: 2026-08-14 · Corrections: none
Cite this verdict
[Chamgap] No clear fluids after midnight x aspiration prevention in elective surgery — Evidence Grade D·28. 2 cited sources checked. Source: https://chamgap.com/en/verdicts/general/clear-fluid-fasting-after-midnight-elective-surgery-aspiration/ · CC BY 4.0CC BY 4.0 — free to use with attribution; do not distort grades, numbers, or verdict meaning.
What this document does and does not do
Chamgap is an information source. It reports what research has and has not confirmed; it does not tell readers what to take or buy. That decision belongs to readers and, when needed, medical or legal professionals. This verdict reflects literature available up to the search date and may change as new research appears. Nothing here is medical advice.