The evidence base behind modern fasting guidelines.

Fasting before general anaesthesia aims to reduce the volume and acidity of stomach contents, thus decreasing the risk of regurgitation/aspiration. The objectives of the Cochrane report which are summarised in this paper, were to systematically review the effect of different preoperative fasting regimes (duration, type and volume of intake) on perioperative complications and patient wellbeing. Few trials reported the incidence of aspiration/regurgitation or related morbidity but relied on indirect measures of patient safety ie. intraoperative gastric volume and pH. There was no evidence to suggest intake of fluids up to 2 hr preoperatively has an impact on patients gastric volumes or pH. Intake of fluids up to 90 min preoperatively had no impact on gastric contents but this was based on small numbers. In addition, permitting patients to drink water preoperatively resulted in significantly lower gastric volumes. Clinicians should evaluate this evidence for themselves and when necessary, adjust existing fasting policies.