It is necessary to have an empty stomach before receiving general anesthesia. In most cases, patients are required to abstain from eating and drinking after midnight on the night before their scheduled surgery to reduce the chances of vomiting while under anesthesia. When a person is under general anesthesia, the body does not work normally. Certain reflexes are relaxed, and if vomiting occurs, it may enter the lungs, leading to serious complications. Every precaution is taken to avoid this occurrence. Adhering to the "no food after midnight" rule is essential for patient safety.
The requirement may differ for those receiving regional or local anesthesia. Some physicians request that patients receiving regional anesthesia abstain from ingesting any food or liquid, just in case general anesthesia has to be used. Some sedatives also can induce nausea in sensitive individuals. A patient receiving local anesthesia without sedation for a minor procedure generally does not have any dietary restrictions, but this should always be discussed with the surgeon prior to surgery.
Before surgery, the anesthesiologist visits the patient to do a brief physical examination and to obtain a medical history. He or she will want to know about any other medical conditions; if the patient is taking any medication (prescription or over-the-counter); if any dietary supplements or herbal products are being used; if there has been recent illicit drug use; if the patient smokes cigarettes or drinks alcohol; if the patient has a history of allergies, especially to medications, has had a previous reaction to anesthesia, or has a family history of problems with anesthesia.
The answers to these questions allow the anesthesiologist to choose the most appropriate anesthetic agents and dosages and to determine what, if any, precautions should be taken. For example, anesthesia can interact with other types of medications, including illegal substances, so it is important to know if these are being used. Nicotine and alcohol can affect the way medications work in the body and affect heart and lung function. Exposure to second-hand smoke also has been shown to increase the risk for anesthesia complications.