Fasting Ahead of Anesthesia and Surgery

Preoperative fasting remains a foundational safety practice in anesthesia, designed to mitigate the risk of pulmonary aspiration of gastric contents during sedation or general anesthesia.¹ Yet the traditional approach of prolonged overnight fasting—colloquially known as “NPO (nil per os) after midnight”—has been increasingly scrutinized. Evidence reveals that excessive fasting causes measurable patient harm without offering a proportional safety benefit. Consequently, the clinical paradigm has shifted toward more liberal, patient-centered fasting protocols ahead of anesthesia and surgery.²

Fasting prior to surgery is vital because general anesthesia suppresses the protective airway reflexes (gagging, coughing, and swallowing). Without these defenses, regurgitated gastric contents can enter the lungs, causing aspiration pneumonitis, pneumonia, or airway obstruction. Although aspiration occurs in only approximately 1 in 10,000 elective procedures among healthy patients, its consequences are severe: closed malpractice claims analyses show that 57% of aspiration events result in death and another 15% in permanent injury.¹

However, prolonged fasting presents its own clinical consequences. At the symptomatic level, it induces dehydration, hunger, thirst, anxiety, headache, nausea, and hemodynamic instability. At the metabolic level, it intensifies the surgical stress response, increases postoperative insulin resistance, promotes protein catabolism, and depletes glycogen stores—all of which can delay recovery and increase complication rates.⁴ Conversely, modern quality improvement data supports shorter fasting windows. A large Dutch study assessing over 76,000 adult patients after liberalizing fasting policies found that shorter fasting times significantly improved patient well-being regarding thirst and postoperative nausea, with no significant impact on aspiration risk.⁵

Enhanced Recovery After Surgery (ERAS) protocols challenge traditional dogma by championing preoperative carbohydrate loading to attenuate insulin resistance and optimize metabolic readiness.^3,6 Preoperative oral carbohydrate-rich fluids (typically 12.5% carbohydrate solutions, providing approximately 50 kcal/100 mL) effectively shift the patient from a fasted to a fed metabolic state. This intervention reduces postoperative discomfort and can shorten hospital stays after major abdominal surgery. Furthermore, a prospective cohort study of 11,500 surgical patients demonstrated that shorter fasting times better maintain euvolemia (normal blood fluid volume) and diminish postoperative nausea and vomiting.³

According to the 2023 American Society of Anesthesiologists (ASA) guidelines and a 2026 international multidisciplinary consensus statement, healthy patients undergoing elective procedures should follow specific minimum fasting intervals based on what they consume. Patients may drink clear liquids like water, black coffee, or pulp-free juice up until 2 hours before their procedure.^1,2 Solid foods demand longer intervals: patients must fast for at least 6 hours after a light meal and for 8 or more hours after consuming heavy, fatty, or fried foods.¹

When fasting status is uncertain—such as in emergency surgery, patients with language barriers, or those with conditions that delay gastric emptying—point-of-care gastric ultrasound offers a valuable bedside tool ahead of anesthesia and surgery.⁷ The 2026 international consensus statement endorses preprocedural gastric ultrasound performed by a trained provider to guide clinical decisions when additional information is required.

With the rapidly expanding use of GLP-1 receptor agonists for diabetes and obesity management, perioperative management of these patients has become a pressing priority. Because GLP-1 receptor agonists significantly delay gastric emptying, studies show that up to 35.8% of adults taking these medications present with high residual gastric content despite adhering to standard preoperative fasting timelines.⁸

Current guidance from the American Diabetes Association and multiple international societies recommends a personalized approach. Anesthesiologists must consider dose, duration of therapy, active gastrointestinal symptoms, the type of surgery, and procedure urgency, using preoperative gastric ultrasound to objectively evaluate gastric contents when necessary.^9,10

The trajectory of modern perioperative medicine is clear: minimize unnecessary fasting while maintaining rigorous safety. Developed through a Delphi process involving 68 global stakeholders across five continents, the 2026 international consensus statement calls for institutional protocols that liberalize clear liquid intake beyond the traditional 2-hour threshold and emphasizes the early resumption of oral intake postoperatively.² As evidence accumulates that liberal clear fluid policies do not increase aspiration risk, institutions are encouraged to develop local protocols that shorten fasting times, improve patient comfort, and optimize metabolic readiness for anesthesia and surgery.^2,3