Classically it has been taught that patients who are at a higher risk of aspiration include those who have a “full stomach,” diabetic patients, patients with hiatal hernia or GERD, patients with cirrhosis, patients with significant ESRD, and pregnant patients. Warner’s landmark study noted that emergency surgery and higher ASA score were independent predictors, whereas age, pregnancy, and a meal within 3 hours were not. Warner’s study was also notable for pointing out that pulmonary sequelae usually manifest within 2 hours. Obesity is commonly noted as a risk factor for aspiration; however, healthy (i.e., those without diabetes, etc.) obese patients have similar gastric emptying to lean patients. It is important to note that in diabetic patients with symptomatic gastroparesis, the gastric emptying time for clear fluids is unchanged whereas the gastric clearing of solid food is significantly slower. In adults, it is believed that aspiration of more than 25ml of gastric contents with a pH of less than 2.5 will cause pulmonary sequeale. One study of healthy volunteers given 240ml of clear liquids found less than 25 ml of gastric contents in all volunteers 2 hours later. For healthy patients of all ages without an increased risk of aspiration, the fasting recommendations are as follows:
- Clear liquids – 2 hours
- Breast milk – 4 hours
- Infant formula – 6 hours
- Nonhuman milk – 6 hours
- Light meal – 6 hours
References
- M A Warner, M E Warner, J G Weber Clinical significance of pulmonary aspiration during the perioperative period. Anesthesiology: 1993, 78(1);56-62 Link
Copyright Information
This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.
