Preoperative fasting, commonly known as nil per os (NPO), is essential for reducing the risk of pulmonary aspiration during anesthesia. However, guidelines for NPO duration, especially for afternoon procedures, have evolved over time to balance patient safety with comfort. Traditional “NPO after midnight” practices are increasingly being replaced with evidence-based protocols tailored to individual surgical schedules and patient needs.
Modern NPO guidelines emphasize the need for more flexible fasting periods based on the type of intake. For clear liquids such as water, clear juice without pulp, or black coffee, a fasting period of two hours prior to surgery is generally considered safe. This practice improves patient hydration, reduces discomfort, and reduces preoperative anxiety without significantly increasing aspiration risk (1). For solid food or meals high in fat or protein, an eight-hour fasting period is typically recommended. Such distinctions are particularly relevant for afternoon procedures, where prolonged fasting under traditional NPO guidelines can exacerbate patient irritability, dehydration, and hypoglycemia, especially in vulnerable populations such as children and the elderly (2).
Afternoon procedures present unique challenges for NPO compliance. Patients are required to fast from midnight under traditional guidelines, resulting in extended fasting periods that can exceed 12 to 15 hours. This prolonged deprivation can have physiological and psychological effects, including increased insulin resistance, dehydration, and increased preoperative stress. Research shows that allowing patients to consume clear liquids up to two hours before afternoon procedures significantly mitigates these adverse effects while maintaining safety (3). Additionally, adequate hydration through shorter fasting times has been associated with improved hemodynamic stability during induction of anesthesia and faster postoperative recovery.
Institutional compliance with updated NPO guidelines remains inconsistent, despite clear recommendations from organizations such as the American Society of Anesthesiologists (ASA). Studies show that a significant proportion of institutions still mandate “NPO after midnight” policies, even for late-night procedures, resulting in unnecessary patient discomfort and deviations from evidence-based practices. Such rigid protocols are often the result of logistical convenience rather than clinical necessity, highlighting the need for education and policy reform (3).
Special populations, including pediatric and diabetic patients, require individualized NPO strategies. For children undergoing afternoon procedures, prolonged fasting often leads to irritability, dehydration, and increased metabolic stress. To address this, pediatric guidelines recommend clear liquids up to two hours before surgery to improve tolerance and reduce perioperative complications (4). Diabetic patients are another high-risk group, as prolonged fasting can disrupt glycemic control. Tailored approaches involving close glucose monitoring and adjustments to insulin or oral hypoglycemic agents are essential for these patients.
Emerging evidence also supports the use of carbohydrate-rich clear liquids up to two hours before surgery to further improve metabolic and psychological outcomes. These drinks increase glycogen stores, maintain insulin sensitivity, and reduce patient-reported thirst and hunger. While such strategies are gaining acceptance in Europe and other regions, their adoption in the United States remains limited due to variability in institutional practices and concerns about patient safety.
In summary, NPO guidelines for afternoon procedures are evolving from one-size-fits-all models to more patient-centered and evidence-based approaches. By aligning fasting practices with current research, healthcare providers can minimize patient discomfort, enhance metabolic stability, and improve surgical outcomes while maintaining safety. Widespread dissemination and institutional adoption of these guidelines is critical to standardizing care and improving patient satisfaction.
References
- Crenshaw JT, Winslow EH. Preoperative fasting: old habits die hard. Am J Nurs. 2002;102(5):36-45. doi:10.1097/00000446-200205000-00033
- Smallman B, Dexter F. Optimizing the arrival, waiting, and NPO times of children on the day of pediatric endoscopy procedures. Anesth Analg. 2010;110(3):879-887. doi:10.1213/ANE.0b013e3181ce6bbc
- Sendelbach S. Preoperative fasting doesn’t mean nothing after midnight. Am J Nurs. 2010;110(9):64-65. doi:10.1097/01.NAJ.0000388269.73122.3d
- Beazley B, Bulka CM, Landsman IS, Ehrenfeld JM. Demographic Predictors of NPO Violations in Elective Pediatric Surgery. J Perianesth Nurs. 2016;31(1):36-40. doi:10.1016/j.jopan.2015.01.014