Preoperative fasting guidelines
- Marianna Crowley, MD
Marianna Crowley, MD
- Deputy Editor — Anesthesiology
- Assistant Professor of Anesthesiology
- Harvard Medical School
Pulmonary aspiration of gastric or oropharyngeal contents during anesthesia is a rare event, but one with significant morbidity and mortality . Fasting guidelines for patients having anesthesia attempt to reduce the risk of aspiration and the severity of the pulmonary effects should aspiration occur.
Fasting guidelines are based on gastric physiology and expert opinion, as there is limited evidence that these improve outcomes . Because worse outcomes may be associated with aspiration of particulate matter, of acidic contents, and of large volumes of gastric contents, guidelines aim to eliminate particulate matter and decrease the volume and acidity of gastric contents at the time of induction of anesthesia .
Preanesthesia fasting guidelines apply to patients having elective surgery and are intended for procedures performed under general anesthesia, regional anesthesia, and monitored anesthesia care. Aspiration may occur during all types of anesthesia in non-fasted patients, because anesthetic and sedative medications reduce or eliminate airway protective reflexes that normally prevent regurgitated gastric contents from entering the lungs .
The rationale and recommendations for preoperative fasting are reviewed here. Anesthetic strategies for avoidance of aspiration, the management of patients who have not fasted, and the fasting duration of patients having urgent or emergent procedures are discussed separately. (See "Rapid sequence induction and intubation (RSII) for anesthesia" and "General anesthesia: Induction".)
Recommendations that oral intake of liquids and solids be restricted for varying times prior to anesthesia aim to minimize gastric volume at the time of surgery. Various types of material empty from the stomach at different rates. While experts believe that restricting oral intake will decrease aspiration, gastric volume is a surrogate endpoint used in clinical studies because the incidence of aspiration is low.
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