When preparing for surgery, patients receive an important instruction: to refrain from eating or drinking for a specific period beforehand. This practice, known as preoperative fasting or “nothing by mouth” (NPO), is a standard medical protocol designed to ensure patient safety and minimize potential complications during and after the procedure.
Primary Risk: Aspiration
The most significant concern behind fasting is the risk of pulmonary aspiration. Aspiration occurs when stomach contents, whether liquid or solid, enter the trachea and lungs instead of passing into the digestive tract. Under general anesthesia, the body’s natural protective reflexes, such as coughing and gagging, are suppressed. This relaxation of muscles, including the lower esophageal sphincter, makes it easier for stomach contents to regurgitate and be inhaled into the lungs.
If aspiration happens, it can lead to severe health issues. The inhaled material can cause inflammation of the lung tissue, known as aspiration pneumonitis, or a serious lung infection called aspiration pneumonia. These conditions can result in symptoms like shortness of breath, chest pain, and fever, and may progress to respiratory failure or even be life-threatening. The severity of lung injury depends on factors like the volume and acidity of the aspirated material, as well as the presence of particulate matter.
Other Potential Complications
Beyond aspiration, a full stomach before surgery can lead to additional complications. Patients who have recently consumed food or drink are at an increased risk of experiencing nausea and vomiting during or after the surgical procedure. Postoperative nausea and vomiting can, in severe cases, contribute to the risk of aspiration.
The presence of food in the digestive system can also interfere with the effectiveness and metabolism of certain anesthetic medications, slowing down the breakdown of agents and muscle relaxants. This can prolong the effects of anesthesia, potentially delaying recovery time and requiring a longer stay in the recovery unit. For abdominal surgeries, a full stomach can also reduce the working space available to the surgical team, making the procedure more challenging.
Standard Fasting Guidelines
General guidelines for preoperative fasting have been established. For clear liquids (e.g., water, clear fruit juices, black coffee, tea), fasting for at least two hours before anesthesia is recommended for adults and children. Breast milk requires a fasting period of four hours.
For infant formula or non-human milk, a six-hour fasting period is advised. Solid foods, including light meals, require a minimum fast of six hours, while fatty or fried foods may require an eight-hour or longer fast due to slower digestion. These are general recommendations, and specific instructions from the surgical team or anesthesiologist may vary based on the type of surgery, patient age, and individual medical conditions. Essential medications can often be taken with a small sip of water, even within the fasting window, if advised by a healthcare provider.
The Importance of Adherence
Following preoperative fasting instructions is important for patient safety. These guidelines are designed to minimize the risks associated with anesthesia and surgery. Failing to adhere to these instructions can lead to serious complications, including the potentially life-threatening event of pulmonary aspiration.
In many cases, if a patient has not followed the fasting rules, the surgery may need to be delayed or even canceled. This decision is made to prioritize patient safety. Adherence to these instructions plays an important role in reducing risks and facilitating a smooth surgical experience.