Preoperative fasting

Br J Surg. 2003 Apr;90(4):400-6. doi: 10.1002/bjs.4066.


Background and methods: To avoid pulmonary aspiration, fasting after midnight has become standard in elective surgery, but recent studies have found no scientific support for this practice. Several anaesthesia societies now recommend a 2-h preoperative fast for clear fluids and a 6-h fast for solids in most elective patients. The literature supporting such fasting recommendations was reviewed.

Results: The recommendations are safe and improve well-being before operation, mainly by reducing thirst. A carbohydrate-rich beverage given before anaesthesia and surgery alters metabolism from the overnight fasted to the fed state. This reduces the catabolic response (insulin resistance) after operation, which may have implications for postoperative recovery.

Conclusion: Most patients having elective operations can be allowed a free intake of clear fluids up to 2 h before anaesthesia. Preoperative carbohydrates reduce postoperative insulin resistance.

Publication types

  • Review

MeSH terms

  • Dietary Carbohydrates / administration & dosage
  • Eating
  • Fasting*
  • Gastric Emptying
  • Glucose / administration & dosage
  • Humans
  • Insulin / administration & dosage
  • Intraoperative Complications / prevention & control*
  • Pneumonia, Aspiration / prevention & control*
  • Practice Guidelines as Topic
  • Preoperative Care / methods*


  • Dietary Carbohydrates
  • Insulin
  • Glucose