Fasting before surgery, known as “nothing by mouth” or NPO (nil per os), is a standard medical protocol rooted in patient safety. Understanding why this is necessary can help patients feel more prepared. The primary goal is to minimize risks associated with anesthesia and surgery.
The Primary Concern: Pulmonary Aspiration
The most significant risk of having food or liquid in the stomach during surgery is pulmonary aspiration. This occurs when stomach contents are inhaled into the lungs instead of moving into the digestive tract. Anesthesia impairs the body’s natural protective reflexes, like swallowing and the gag reflex, making the airway vulnerable.
If aspiration occurs, it can lead to severe complications. Acidic stomach contents can cause chemical pneumonitis, an inflammation of lung tissue, which can progress to acute respiratory distress syndrome (ARDS), a life-threatening condition. Aspirated material can also introduce bacteria, leading to aspiration pneumonia, a serious infection that may result in respiratory failure or death. While rare (about 1 in 2,000 to 3,000 cases), nearly half of those who aspirate develop a related lung injury.
Additional Safety Benefits of Fasting
Beyond preventing aspiration, fasting offers other safety advantages for a smoother surgical experience. An empty stomach significantly reduces post-operative nausea and vomiting (PONV). PONV is common, affecting up to 30% of general surgery patients and more in high-risk individuals.
Vomiting after surgery can be distressing, leading to complications like dehydration, electrolyte imbalances, and increased pressure on surgical incisions. An empty stomach also provides anesthesiologists with greater control over a patient’s physiological responses during the procedure.
Understanding Pre-Operative Fasting Guidelines
Pre-operative fasting guidelines specify minimum abstinence times from food and drink. Solid foods typically require fasting for at least 6 to 8 hours. For clear liquids like water, clear apple juice, black coffee, or plain tea without milk, the fasting period is generally shorter, often around 2 hours.
For infants, breast milk usually requires 4 hours of fasting, while formula or non-human milk requires 6 hours. These are general recommendations for healthy patients undergoing elective procedures. Specific instructions may vary based on the type of surgery, age, and individual health conditions like diabetes. Medical teams provide precise, tailored instructions that supersede general guidelines.
The Critical Importance of Adherence
Strict adherence to pre-operative fasting instructions is a safety measure designed to protect the patient. Failure to follow these guidelines can have immediate and significant consequences. The most common outcome is surgery delay or cancellation, as proceeding with a non-empty stomach exposes the patient to unacceptable risks, particularly pulmonary aspiration.
If a patient accidentally consumes food or drink, or if fasting was not possible before emergency surgery, the medical team must be informed immediately. While emergency measures can minimize aspiration risk, they are typically reserved for urgent cases. Honest communication ensures appropriate safety protocols are implemented, prioritizing patient well-being.