Pre-anesthesia fasting, often called NPO (Nil Per Os), is a prescribed period when patients must abstain from consuming liquids or solids before a medical procedure requiring anesthesia. This practice minimizes specific risks associated with anesthesia, ensuring patient well-being during and after the procedure.
Standard Fasting Times
General guidelines for fasting before anesthesia differentiate between various types of intake. Clear liquids, such as water, fruit juices without pulp, black coffee, and clear tea, can typically be consumed up to two hours before a procedure requiring anesthesia or sedation. These liquids should not contain alcohol.
For more substantial intake, a light meal or nonhuman milk may be ingested up to six hours before elective procedures. A light meal typically consists of toast and clear liquids. However, meals that include fried foods, fatty foods, or meat may require a longer fasting period, often eight hours or more, due to their slower gastric emptying times. Breast milk for infants may be consumed up to four hours before elective procedures.
Why Fasting Matters
Pre-anesthesia fasting is implemented to address the risk of pulmonary aspiration, where stomach contents enter the lungs. Anesthesia can cause muscles that normally prevent reflux to relax. If food or liquid remains in the stomach when these protective reflexes are impaired, there is a risk of regurgitation.
Regurgitated stomach contents can then be inhaled or “aspirated” into the lungs. This aspiration can lead to serious complications, including aspiration pneumonia, an infection or inflammation of the lungs. These complications can result in significant respiratory distress, lung damage, and in severe cases, be life-threatening.
Consequences of Not Fasting
Failing to adhere to pre-anesthesia fasting guidelines carries immediate repercussions. The most common outcome is delay or cancellation of the scheduled medical procedure. This delay is a preventive measure to avoid severe risks associated with anesthesia when the stomach is not empty.
If aspiration of gastric contents does occur, it can lead to acute respiratory distress and severe lung injury. Patients might experience prolonged hospitalization, require intensive care, and face a more complicated recovery.
Specific Situations and Exceptions
Fasting guidelines can vary based on specific patient populations and medical circumstances. For instance, infants and young children may have different recommendations for breast milk or formula consumption. Individuals with certain medical conditions may receive individualized instructions from their care team.
In emergency situations, strict adherence to fasting protocols may not be feasible. In such cases, different protocols are followed to manage the risk of aspiration. It is crucial to follow the specific, personalized instructions provided by the surgical or anesthesia team, as general guidelines may not apply to every situation.