Pulmonary aspiration: a review.

One of the main complications associated with anesthesia is aspiration of gastric contents into the tracheobronchial tree. The morbidity and mortality will vary widely depending on the volume and, more particularly, on the chemical nature of the fluid aspirated. Aspiration may be the result of either vomiting or regurgitation. Regurgitation is a passive process which is dependent on a pressure gradient between the stomach and oropharynx. Vomiting is an active reflex and is heralded by certain warning signs. Regurgitation is silent and hence more sinister in that there are no active signs initially to warn the clinician of the impending danger. Studies by Culver and associates2 and by Benson and Adriani 3 suggest that a small percentage (1627%) of anesthetized patients will, under ideal circumstances, show evidence of contaminant material in the tracheobronchial tree. This may occur as the result of channeling effects with a cuffed endotracheal tube in place but the incidence is low. Normally, the epiglottis, vocal cords, and cough reflex all serve to protect the lungs from contamination by foreign material. These protective mechanisms are reduced in efficiency or made