Preoperative Clear Fluid Fasting Duration and Arterial Hypotension During Anesthesia Induction: A Narrative Review.

Background: Preoperative clear fluid fasting is intended to reduce aspiration risk, but prolonged abstinence may impair hydration, comfort, and cardiovascular stability. Arterial hypotension during anesthesia induction is a common perioperative complication, and its association with fasting duration has become an important concern. The objective of this review was to evaluate the relationship between the duration of preoperative clear fluid fasting and the risk of arterial hypotension during anesthesia induction in both adult and pediatric populations. Methods: A structured PubMed search identified 17 studies, including randomized controlled trials, prospective cohorts, registry-based analyses, and interventional imaging investigations. Data were extracted on patient age, fasting duration, hypotension definitions, and monitoring modalities. Subgroups included adults, pediatric patients, and studies employing echocardiography or ultrasound to evaluate preload. Results: A total of 96,017 patients were included (77,978 adults; 17,685 children). In adults, fasting beyond two hours was associated with hypovolemia and a greater incidence of post-induction hypotension, while fasting of ≤2 h improved hemodynamic stability without increasing aspiration risk. Pediatric studies demonstrated fasting durations often exceeding 6-10 h, correlating with higher odds of hypotension and metabolic derangements. Liberalized regimens, including carbohydrate-containing fluids, were consistently safe. Ultrasound-based studies revealed increased inferior vena cava collapsibility and reduced ventricular filling after prolonged fasting, providing a mechanistic explanation for blood pressure instability. Conclusions: Prolonged preoperative fasting was not consistently an independent predictor of peri-induction hypotension in all populations; however, data from large adult and pediatric studies demonstrate that extended fasting increases hypotension risk through volume and metabolic depletion. These findings support the importance of liberalized fasting policies and proactive fluid optimization to reduce early hemodynamic instability during anesthesia induction.