2023 American Society of Anesthesiologists Practice Guidelines for Preoperative Fasting: Carbohydrate-containing Clear Liquids with or without Protein, Chewing Gum, and Pediatric Fasting Duration-A Modular Update of the 2017 American Society of Anesthesiologists Practice Guidelines for Preoperative Fasting

Full text: https://pubs.asahq.org/anesthesiology/article/138/2/132/137508/2023-American-Society-of-Anesthesiologists

This was an update of previous guidelines aimed at addressing the ingestion of carbohydrate-containing clear liquids with or without protein, chewing gum, and paediatric fasting duration.


Delineation of methods was clear and exhaustive. The presentation of supplemental digital content aids in a more comprehensive understanding of the data. The major shortcoming is the explicit exclusion of non-English literature.

Major findings

A strong recommendation (moderate evidence) is made for healthy adults to drink carbohydrate-containing (CHO-containing) clear liquids until 2 h before elective procedures requiring general anaesthesia. When comparing CHO-containing and clear fluids:

  • Patients reported less sensations of hunger
  • There were no differences in nausea, regurgitation, aspiration or patient satisfaction
  • There was no difference in residual gastric volume
  • There is insufficient evidence to recommend protein-containing clear liquids preferentially over other clear liquids
  • All protein-containing fluids studied also contained carbohydrates. Comparison studies between protein and carbohydrates containing fluids were insufficient to make a recommendation for one over the other
  • Chewing gum should not delay surgery. Data was low strength; there was no increase in gastric volume, change in gastric pH or increase in aspiration risk
  • Supports clear liquids in children at low risk of aspiration to 2 h before procedures. Data showed no difference between outcomes for 1 hr vs 2 hr fasting (very low strength of evidence)
  • No differences in patient-reported hunger or thirst, incidence of aspiration or regurgitation, and gastric pH or residual gastric volume.
  • They noted that recent European and Canadian guidelines have recommended reducing clear liquid fasting to 1h in children.

Perioperative fasting protocols revolve around optimisation of patient outcomes (i.e. less post op nausea, better patient satisfaction, contribution to ERAS pathways; and patient safety i.e. should this patient be cancelled due to their fasting status). These guidelines provide reassurance for continuing to minimise preoperative fasting in otherwise well adults and children. The continuing difficulty is delineating which patients are at a higher risk of aspiration, the degree of that risk and the risk of poor outcomes if aspiration occurs.

Reviewed by Don Hannah