## Preoperative Fasting Guidelines for Aspiration Prevention **Key Point:** Modern preoperative fasting guidelines (ASA 2017, AAGBI) differentiate between types of oral intake to balance aspiration risk reduction with patient comfort and safety. ### ASA Preoperative Fasting Guidelines | Intake Type | Minimum Fasting Period | | --- | --- | | Clear liquids (water, apple juice, black coffee, tea) | 2 hours | | Breast milk | 4 hours | | Infant formula | 6 hours | | Nonhuman milk | 6 hours | | Light meal (toast, crackers) | 6 hours | | Solid food, fried/fatty food, meat | 6–8 hours | **High-Yield:** The critical concept is that **clear liquids empty rapidly from the stomach** (within 15–20 minutes in healthy individuals), so a 2-hour fasting period is sufficient. Solids and fatty foods delay gastric emptying, requiring 6–8 hours. ### Rationale for Differentiation 1. **Clear liquids:** Minimal residue, rapid gastric clearance → shorter fasting safe 2. **Breast milk:** Intermediate composition → 4 hours 3. **Formula & solids:** Slower gastric emptying → 6 hours minimum ### Clinical Implications **Clinical Pearl:** Strict NPO from midnight is outdated and causes unnecessary patient discomfort. Modern guidelines allow clear liquids up to 2 hours preoperatively, improving patient satisfaction and reducing anxiety. **Warning:** Factors that **delay gastric emptying** and may require extended fasting: - Obesity - Pregnancy - Gastroesophageal reflux disease (GERD) - Diabetes mellitus - Opioid use - Emergency surgery (assume full stomach) ### Aspiration Risk Reduction The goal is to reduce gastric volume to < 25 mL and pH > 2.5. Adherence to fasting guidelines plus: - Sodium citrate (30 mL, 0.3 M) given 15 minutes preoperatively - H₂-receptor antagonists (e.g., ranitidine) or proton pump inhibitors - Metoclopramide (10 mg IV) to enhance gastric motility in high-risk patients
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