Preoperative starvation and pulmonary aspiration. New perspectives and guidelines

Abstract

The fear of aspiration of gastric contents and its life-threatening consequences in patients(aspiration pneumonitis and respiratory failure), has caused many medical practitioners, particularly anaesthetists, to rigidly follow conservative (i.e. prolonged) preoperative fasting standards. This is the nil per os (NPO) order for clear fluids/liquids and solids overnight or six to eight hours preceding the induction of anaesthesia. This practice neither takes into account the differences in the rate of gastric emptying for solid food (which may exceed six hours) and clear liquids (which is one to two hours), nor the differences in scheduled times of surgery. Long-term prospective studies and retrospective reviews have shown that the incidence of significant clinical aspiration is low: 1.4-6.0 per 100,00 anaesthetics for elective general surgery. Risk factors for pulmonary aspiration include: a high American Society of Anaesthesiologists (ASA) physical status score; emergency surgery; difficult airway management; increased gastric volume and acidity; increased intra-abdominal pressure; gastro-oesophageal reflux; oesophageal disease; head injury with impaired consciousness and extremes of age. Experimental studies and reviews have consistently shown the safety of clear liquid ingestion up to two hours before induction of anaesthesia in healthy patients without risk factors, and the fact that a longer fluid fast does not necessarily offer any added protection against pulmonary aspiration. The conservative pre-operative fasting standard causes discomfort and in some cases, suffering of patients and is therefore unnecessary for patients without risk factor(s). Anecdotal reports at the University Hospital of the West Indies (UHWI) have shown that application of the liberalized guidelines for preoperative fasting and fluid intake has not resulted in increased pulmonary aspiration, morbidity or mortality. Instead it has resulted in decreased irritability, anxiety, thirst and hunger in the peri-operative period. Patients, especially children are more comfortable and the perioperative period is better tolerated. It is therefore time that all medical personnel adopt the liberalized guidelines.