How long should nutrition be held before surgery?

Preoperative Fasting Guidelines

For most patients undergoing elective surgery, clear fluids should be allowed until 2 hours before anesthesia and solid foods until 6 hours before anesthesia—the traditional "NPO after midnight" practice is outdated and unnecessarily prolonged. 1

Standard Fasting Recommendations

Clear Fluids

• Allow clear fluids (water, black coffee, tea, clear juice) until 2 hours before anesthesia in patients without specific aspiration risk factors 1
• This applies to all patients undergoing elective surgery who have no delayed gastric emptying 1
• Clear fluids empty from the stomach within 60-90 minutes, making the 2-hour window safe 1

Solid Foods

• Allow solid foods until 6 hours before anesthesia for light meals (toast, tea) 1
• Heavier meals containing meat, fatty or fried foods require 8 hours of fasting 2
• The 6-hour guideline applies to most routine solid food intake 1

Carbohydrate Loading

• Administer oral carbohydrate drinks (800ml the night before, 400ml two hours before surgery) to reduce perioperative discomfort, anxiety, and potentially improve postoperative insulin resistance 1, 2
• This practice does not increase aspiration risk and is recommended for patients undergoing major surgery 1

Special Populations

Patients at High Nutritional Risk

Patients with severe nutritional risk require 7-14 days of preoperative nutritional therapy, even if surgery must be delayed. 1, 2

Severe nutritional risk is defined by at least one of the following 1, 2:

• Weight loss >10-15% within 6 months
• BMI <18.5 kg/m²
• Subjective Global Assessment Grade C or Nutritional Risk Screening (NRS) score >5
• Serum albumin <30 g/L (without hepatic or renal dysfunction)

For these high-risk patients:

• Provide nutritional support for 10-14 days preoperatively 1
• Use immunonutrition (arginine, omega-3 fatty acids, nucleotides) for 5-7 days before major cancer surgery 1
• Administer nutritional supplements before hospital admission to avoid unnecessary hospitalization 1

Patients with Aspiration Risk

Exceptions to liberal fasting guidelines include 1:

• Emergency surgery patients
• Patients with known delayed gastric emptying (severe gastroparesis, gastric outlet obstruction)
• Gastroesophageal reflux disease
• Patients with impaired consciousness

Common Pitfalls

Prolonged Unnecessary Fasting

• The traditional "NPO after midnight" order results in median fasting times of 12-14 hours for liquids and solids, which is excessive and harmful 3, 4
• Patients scheduled for afternoon surgery experience even longer fasting periods (median 16.7 hours for solids) compared to morning surgery patients 4
• Prolonged fasting causes unnecessary discomfort, thirst, anxiety, dehydration, and electrolyte imbalances 3, 5

Implementation Gaps

• Despite revised guidelines from the American Society of Anesthesiologists in 1999, many institutions continue outdated practices 3
• Studies show 75.5% of patients still fast from solid food for more than 12 hours, and 14.1% fast from clear fluids beyond 12 hours 4
• Better collaboration between nurses and physicians is needed to ensure consistent implementation of evidence-based fasting guidelines 3

Evidence Quality

The recommendations are based on Grade A evidence from ESPEN guidelines published in Clinical Nutrition (2021 and 2006) 1, with strong consensus (95-100% agreement) among expert panels. Long-term prospective studies demonstrate that clinical aspiration occurs in only 1.4-6.0 per 100,000 elective anesthetics 5, and no increase in aspiration has been reported since implementation of liberal fasting guidelines 1, 5.