Experts including John L. Wang, MD, hip and knee surgeon at HSS Florida discuss the reasons for patients to fast before surgery, what to do if you forget to fast, and when most patients can resume eating.

The main reason for fasting before certain procedures is to protect your lungs from potential damage, explained Dr. Wang. “Normally, your body is able to prevent your stomach contents from entering your lungs,” he said. “When under anesthesia, your body is less effective at preventing that. When food, liquids, or stomach acid enter the lungs, doctors call it ‘aspiration.’ This is rare, but it can be very dangerous and lead to a serious infection and lung damage.”

Any procedure that requires anesthesia, including local anesthesia (e.g., wisdom teeth removal) and general anesthesia (for something like a knee replacement) this requires fasting. There are often pre-surgery tests which may also require fasting, cited Dr. Wang. Your doctor will advise you about all procedures and tests that require a certain window of avoiding food and most drinks. Beyond that, “it is best to just follow a balanced, nutritious diet prior to surgery and follow fasting instructions.”

If you’re told to fast, you shouldn’t eat solid foods during that window of time. But because water and clear liquids are quickly absorbed by the stomach in a relatively short amount of time, patients are often allowed to drink clear liquids up to two hours before surgery. “The line’s drawn when you cannot see through the liquid,” he said. “Milk products have protein in them and that increases the time that the liquid spends in your stomach. The goal is to have an empty stomach immediately before surgery,” said Dr. Wang.

Dr. Wang advised if you do break your fast before a surgery, let your surgeon and anesthesiologist know as soon as possible. “These fasting guidelines were designed with patient safety in mind,” he said. “Violation of the recommended fasting windows add risk of stomach contents entering the lung when a patient undergoes anesthesia. When these fasting guidelines are not followed, the anesthesiologist will compare the risks and benefits of proceeding, with consideration given to the amount and type of liquids or solids ingested.”

Dr. Wang shared most patients undergoing elective orthopedic surgery are able to tolerate light meals right after surgery. “When the anesthesia type is regional anesthesia or sedation, patients often resume eating and drinking normally in the recovery room.”

Read the full article at TheHealthy.com.