# Clear drinks until two hours before an operation, rather than nothing from midnight

Source: https://onco.cc/ideas/idea-pu-shorter-fasting-before-surgery/  
OnCo record `idea-pu-shorter-fasting-before-surgery` (Idea). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

Anaesthetic guidelines since at least 2011 say adults can drink clear fluids up to two hours before planned surgery and eat up to six hours before. In a study of 50 women having breast cancer surgery published in 2026, the average fast was 15 hours from food and 12 hours from fluids.

## Summary

The guideline. The European Society of Anaesthesiology's 2011 guideline recommends that adults and children "should be encouraged to drink clear fluids up to 2 h before elective surgery", that solid food be stopped six hours before, and that these recommendations also apply to people with obesity, reflux or diabetes. A carbohydrate drink in the hours before surgery is part of enhanced recovery pathways. A meta-analysis drawing on 44 randomised trial reports in major non-cardiac surgery found carbohydrate loading shortened hospital stay by about half a day (mean difference 0.56 days, 95 per cent confidence interval 0.02 to 1.10) compared with fasting or placebo; its authors note that the guideline recommendation rests on low-quality evidence. The evidence that short fasting is safe is stronger than the evidence that it changes outcomes, which is why the grade here is moderate.

The measured gap. In a prospective study of 50 women having elective breast cancer surgery, the mean fast was 15.1 hours for food and 12.1 hours for fluids, far beyond the recommended six and two; the study found no correlation between fasting length and discomfort or complications. An audit at the University of Gondar Hospital in Ethiopia found 92 per cent of patients fasted from food and 95 per cent from fluid for longer than recommended, with a mean fluid fast of 12.7 hours. Long fasts usually happen because a whole list is told to fast from midnight, whatever time each person's operation will be.

The upgrade is a rule that each patient is told a time to stop drinking based on their own expected start, and is given a drink if the list runs late.

## Fields

- Kind: Idea
- Last checked: 2026-10-20
- Tags: protocol-upgrade; upgrade:proven-unevenly-used; evidence:moderate
- Hypothesis: Replacing nil-by-mouth-from-midnight instructions with individually timed fasting, clear fluids allowed until two hours before the expected start and a carbohydrate drink where enhanced recovery applies, cuts median fluid fasting below four hours without increasing aspiration, and reduces thirst, nausea and length of stay.
- Rationale: A major guideline has allowed clear fluids to two hours for over a decade, randomised trials of carbohydrate loading show a modest reduction in hospital stay, and audits in very different settings measure fluid fasts of twelve hours.
- Proposed test: An audit of actual fasting times across cancer surgery lists, followed by a stepped-wedge implementation of individually timed instructions, measuring fluid fasting duration, patient-reported thirst and hunger, aspiration events and length of stay.
- Maturity: being-tested-at-scale
- Actor: clinic

## Sources

- Smith et al., Perioperative fasting in adults and children: guidelines from the European Society of Anaesthesiology (European Journal of Anaesthesiology 2011): https://doi.org/10.1097/EJA.0b013e3283495ba1
- Sebestyén et al., Preoperative carbohydrate loading reduces length of stay after major elective, non-cardiac surgery when compared to fasting: a systematic review and meta-analysis (Scientific Reports 2025): https://doi.org/10.1038/s41598-025-00767-z
- Aretorn et al., Clinical effects of prolonged preoperative fasting in breast cancer surgery: a prospective cohort study (BMC Surgery 2026): https://doi.org/10.1186/s12893-025-03449-9
- Gebremedhn and Nagaratnam, Audit on preoperative fasting of elective surgical patients in an African academic medical center (World Journal of Surgery 2014): https://doi.org/10.1007/s00268-014-2582-3
- ERAS Compliance Group, The impact of enhanced recovery protocol compliance on elective colorectal cancer resection: results from an international registry (Annals of Surgery 2015): https://doi.org/10.1097/SLA.0000000000001029

## Connected records

- ideas: [Enhanced recovery after cancer surgery, with each element's compliance measured and fed back](https://onco.cc/ideas/idea-pu-enhanced-recovery-with-measured-compliance/)
- cancers: [Breast cancer (all types)](https://onco.cc/cancers/breast-cancer/), [Colorectal cancer](https://onco.cc/cancers/colorectal/)
- fronts: [Surgery & Interventional](https://onco.cc/fronts/surgery/)
- technologies: [Enhanced recovery (ERAS) and perioperative nutrition](https://onco.cc/technologies/eras-perioperative-nutrition/), [Nutrition support and cachexia management](https://onco.cc/technologies/oncology-nutrition/)
- bottlenecks: [Knowledge reaches practice too slowly](https://onco.cc/bottlenecks/b-knowledge-diffusion/), [Toxicity and quality of life are undervalued](https://onco.cc/bottlenecks/b-toxicity-qol/)

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