Pulmonary gas exchange in coronary artery surgery patients during sevoflurane and isoflurane anesthesia.

Abstract

As the surgical population ages, the number of patients presenting with coronary artery disease and age-related loss of pulmonary recoil will increase. Although their influence on gas exchange in this population remains unknown, sevoflurane and isoflurane are used for an increasing variety of surgical procedures. We examined pulmonary gas exchange (multiple inert gas elimination technique) in 30 patients presenting for coronary artery bypass grafting. After a baseline measurement taken during midazolam anesthesia, patients were continued on sevoflurane (n = 10), isoflurane (n = 10), or midazolam (n = 10) for 20 min, then a second measurement was taken. During sevoflurane and isoflurane anesthesia, blood flow to lung areas with a low ventilation/perfusion ratio (Va/Q) was significantly increased in comparison with control. During sevoflurane anesthesia, blood flow to lung areas with a normal Va/Q ratio (76 +/- 12 versus control: 89 +/- 5, mean +/- SD) and PaO(2) (138 +/- 31 versus control: 156 +/- 35 mm Hg, mean +/- SD) were depressed, whereas an increase in Va/Q-dispersion (log SD(Q)) was observed during isoflurane anesthesia. We conclude that both sevoflurane and isoflurane alter the distribution of perfusion in the lung, but only sevoflurane significantly depresses PaO(2). Both sevoflurane and isoflurane modified pulmonary blood flow in patients with coronary artery disease, but only sevoflurane depresses arterial oxygenation in this population.