Perioperative pulmonary aspiration

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CHAPTER 241

Perioperative pulmonary aspiration

Allen Brian Shoham, MD and Michael J. Murray, MD, PhD

Perioperative pulmonary aspiration occurs infrequently, but its impact on individual patients can be devastating. Patients who appear to have the greatest risk of aspirating are those who have recently eaten and are undergoing an emergency procedure, those with small bowel obstruction, and those with comorbid conditions such as diabetes or gastroesophageal reflux disease. For patients who do aspirate, the risk of severe pulmonary morbidity or death after aspiration is greatest for those who are sick (American Society of Anesthesiologists physical classification 3 or greater) and elderly. As a general rule, children have less morbidity from pulmonary aspiration.

Importance of pulmonary aspiration

Five large studies from 1970 to 2000 documented the overall frequency of perioperative pulmonary aspiration to be approximately 1:3000; the mortality rate is 5% in patients who have a witnessed aspiration. Fortunately, not all patients who aspirate develop respiratory sequelae. The frequency of pulmonary complications and fatality as a consequence of aspiration are shown in Table 241-1.

Table 241-1

Risk of Aspiration-Associated Pulmonary Complications and Death after General Anesthesia by American Society of Anesthesiologists Physical Status Classification

	Frequency
ASA Physical Status Classification	Pulmonary Complications*	Deaths^†
I	1/39,865 (1:39,865)	0
II	2/87,471 (1:43,735)	0
III	7/78,714 (1:11,245)	1/78,714 (1:78,714)
IV and V	3/9438 (1:3146)	2/9438 (1:4719)
Total	13/215,488 (1:16,576)	3/215,488 (1:71,829)

ASA, American Society of Anesthesiologists.

^*Pulmonary complications include acute respiratory distress syndrome, pneumonitis, and pneumonia (with or without positive viral or bacterial identification).

^†Death from aspiration-associated pulmonary complications within 6 months of aspiration.

From Warner MA, Warner ME, Weber JG. Clinical significance of pulmonary aspiration during the perioperative period. Anesthesiology. 1993;78:56-62.

Based on the information in Table 241-1, if similar mortality rates were to be found within the United States in general, approximately 200 deaths from perioperative pulmonary aspiration would be expected each year. In our largest institutions (i.e., those that perform as many as 50,000 general anesthetics annually), only 1 death from pulmonary aspiration would occur every 18 months. By applying the numbers (1 death per 75,000 general anesthetics) to individual practice settings, an idea of the anticipated frequency of this event can be derived.

Serious morbidity and considerable costs are associated with aspiration of gastric contents that results in an aspiration pneumonitis, acute lung injury, or acute respiratory distress syndrome. Approximately 25% of patients who perioperatively aspirate gastric contents require intensive care support. About 10% of these patients need mechanical ventilation support for more than 24 h, and, as mentioned previously, half of them will die.