Sodium nitroprusside–induced, but not desflurane–induced, hypotension decreases myocardial tissue oxygenation in dogs anesthetized with 8% desflurane

Abstract

Objective: To compare sodium nitroprusside (SNP)–induced hypotension with desflurane-induced hypotension for the effects on myocardial blood flow and tissue oxygenation in dogs. Design: Prospective, randomized, crossover, nonblinded. Setting: University teaching hospital. Participants: Male nonpurpose-bred hounds (n = 8). Interventions: Dogs were anesthetized with 8% desflurane. Catheters were inserted into the femoral artery and coronary sinus. A flow probe was placed in the left anterior descending (LAD) branch of the coronary artery. A sensor that measured myocardial oxygen pressure (PmO2) was inserted into the myocardium of the left ventricle. Myocardial oxygen consumption (MV̇O2) was calculated as LAD flow × arterial − coronary sinus oxygen content. Measurements and Main Results: Measurements were made at baseline blood pressure levels of 99 mmHg (measure 1), during hypotension to 62 to 66 mmHg using intravenous SNP or 14% desflurane (measure 2), and during SNP or 14% desflurane with blood pressure support using phenylephrine (measure 3). Each dog randomly received both hypotensive treatments, separated by 1 hour. Baseline measures were PmO2 = 46 ± 9 mmHg, LAD flow = 43 ± 11 mL/min, and MV̇O2 = 2.47 ± 0.73 mL O2/min. During hypotension induced with SNP, PmO2 decreased 30% (p < 0.05), LAD flow increased 40% (p < 0.05), and MV̇O2 did not change. During hypotension induced with 14% desflurane, PmO2 did not change, and LAD flow and MV̇O2 decreased 25% and 40% (p < 0.05). Blood pressure support with phenylephrine increased LAD flow and MV̇O2 but did not change PmO2 during SNP or 14% desflurane treatment. Conclusion: SNP-induced hypotension produced myocardial vasodilation, but tissue oxygenation was impaired. PmO2 was maintained during desflurane-induced hypotension. Copyright 2002, Elsevier Science (USA). All rights reserved.