Effect of sevoflurane and desflurane on the myogenic constriction and flow-induced dilation in rat coronary arterioles.
Determinants of myocardial blood flow distribution include metabolic, myogenic, endothelial, and neurohumoral control mechanisms. The authors studied the effect of sevoflurane and desflurane on the myogenic and endothelial mechanisms. Wistar rat subepicardial microvessels, approximately 100 microm in diameter, were monitored for diameter changes in vitro using a video detection system. Myogenic vasomotion was studied by varying the intraluminal pressure from 10 mmHg to 120 mmHg. Flow-induced, endothelium-dependent dilation was evaluated in U46619-preconstricted vessels by varying the pressure gradient across the isolated vessel from 10 mmHg to 80 mmHg, while maintaining the midpoint luminal pressure constant at 40 mmHg to avoid myogenic effects. Myogenic and flow-induced vasomotion both were studied in the presence of sevoflurane, 1 or 2 minimum alveolar concentration (MAC) (MAC is a unit of inhalational anesthetic potency), desflurane, 1 or 2 MAC, or no anesthetic (control). Myogenic constriction was shown above intraluminal pressures of 70 mmHg. Myogenic constriction was unchanged by sevoflurane, 1 MAC (P = 0.24), but was mildly enhanced by sevoflurane, 2 MAC (P < 0.05), or desflurane, 1 (P < 0.05) or 2 MAC (P < 0.01). Flow-induced dilation was shown over the pressure gradient range of 10-80 mmHg. Flow-induced dilation was not altered significantly by sevoflurane, 1 or 2 MAC (P > 0.3 each), but was significantly attenuated by desflurane, 1 or 2 MAC (P < 0.001 each). Sevoflurane maintains myogenic and endothelial determinants of myocardial blood flow distribution. Conversely, desflurane attenuates endothelium-dependent flow-induced dilation while mildly enhancing myogenic constriction.