What are the ASA (American Society of Anesthesiologists) fasting guidelines for patients undergoing surgery?

ASA Preoperative Fasting Guidelines

Core Recommendations

For healthy patients undergoing elective procedures, the American Society of Anesthesiologists recommends fasting from clear liquids for at least 2 hours, light meals for at least 6 hours, and fatty/fried foods for at least 8 hours before anesthesia. 1

Clear Liquids: 2-Hour Fast

• Clear liquids may be consumed up to 2 hours before elective procedures requiring general anesthesia, regional anesthesia, or procedural sedation 1, 2
• Acceptable clear liquids include water, fruit juices without pulp, carbonated beverages, clear tea, black coffee, and sports drinks 3, 2
• This applies to all age groups: infants (younger than 2 years), children (2-16 years), and adults 1
• Meta-analysis demonstrates that 2-4 hour fasting for clear liquids results in smaller gastric volumes and higher gastric pH compared to prolonged fasting 2
• Recent evidence confirms that clear liquid intake up to 2 hours before surgery does not increase gastric content volume or acidity and significantly reduces thirst and hunger without respiratory complications 4

Breast Milk: 4-Hour Fast

• Breast milk may be consumed up to 4 hours before elective procedures in neonates and infants 2

Infant Formula: 6-Hour Fast

• Infant formula requires a minimum 6-hour fast before elective procedures for neonates, infants, children, and adults 1, 2

Light Meals: 6-Hour Fast

• A light meal (such as toast and clear liquid) requires fasting for at least 6 hours before elective procedures 1, 2
• This applies to all patients undergoing general anesthesia, regional anesthesia, or procedural sedation 1

Fatty/Fried Foods: 8-Hour Fast

• Meals containing fried or fatty foods require a minimum 8-hour fast before elective procedures 1, 2
• This extended fasting period is necessary due to prolonged gastric emptying 3

High-Risk Populations Requiring Modified Approach

Patients with the following conditions warrant case-by-case restrictions beyond standard guidelines: 3, 2

• Morbid obesity
• Diabetes mellitus (at high risk of severe hypoglycemia during extended fasting) 2
• Difficult airway
• Gastroesophageal reflux disease or known delayed gastric emptying (require longer fasting periods) 2
• Nonreassuring fetal heart rate patterns (in obstetric cases) 3

These patients should be managed more conservatively and may need to avoid all oral intake except clear liquids. 3

Emergency Procedures

• For emergency surgery patients, compliance with predetermined fasting periods is often not possible 3
• Administer intravenous H2-receptor antagonist if not already given 3
• Give sodium citrate immediately before induction if general anesthesia is planned 3

Common Pitfalls to Avoid

• Despite these evidence-based guidelines, most practitioners still order "NPO after midnight," resulting in patients fasting 12-14 hours from liquids and 14+ hours from solids—significantly longer than recommended 5
• Studies show that 99% of oral and maxillofacial surgeons have not adopted the ASA guidelines, continuing to recommend unnecessarily prolonged fasting 6
• Prolonged fasting causes unnecessary thirst, hunger, hemodynamic instability, and patient dissatisfaction without any safety benefit 7, 5
• The actual risk of pulmonary aspiration in general surgical patients is extremely low with modern anesthesia techniques 1

Medication Management During Fasting

• Non-nourishing medications via parenteral routes, suppositories, and inhalers are allowed during fasting periods 2
• Oral medications should be rescheduled to non-fasting periods when possible 2