The recommendation of not allowing patients to eat or drink after midnight the night before surgery dates back to the 1950’s. This guideline has been used by anesthesiologists to reduce the risk of aspiration during surgery. When undergoing general anesthesia, patients are unable to safely protect or clear their airway. As a result, patients are at risk for aspiration. Aspiration occurs when food, liquid, or stomach contents are inhaled into the lungs. This can result in significant complications, such as airway obstruction or the development of aspiration related pneumonia. The most effective strategy to prevent aspiration is to ensure there are no contents in the stomach prior to surgery. Hence, the rationale behind holding any type of food or liquid 8-12 hours before surgery.
This practice is commonly referred to as “NPO after midnight.” Some institutions are beginning to allow patients to have clear liquids up to 2-4 hours prior to surgery. Clear liquids have been demonstrated to clear the stomach within 2-4 hours and thus reduce the risk of aspiration. Clear liquids are fluids such as black coffee, tea without milk or cream, clear juices like apple juice, or electrolyte drinks. Most hospitals have however been resistant to accepting these newer recommendations to avoid patient confusion and unnecessary cancellations the day of surgery.
The above are general recommendations that may be affected by institutional policy, type of surgery, and patient risk factors. You should be provided this information, at the latest, when the hospital calls to confirm your arrival time the day of surgery. If you’re unclear, don’t hesitate to ask questions and talk to your doctor.