Comparison of adenosine, isoflurane, and desflurane on myocardial tissue oxygen pressure during coronary artery constriction in dogs

Abstract

Objective: To compare adenosine-, isoflurane-, or desflurane-induced hypotension with and without left anterior descending (LAD) coronary artery constriction for the effects on myocardial tissue oxygen pressure (PmO 2) in dogs. Design: Prospective, randomized, nonblinded. Setting: University teaching hospital. Participants: Male nonpurpose-bred dogs (n = 18). Interventions: Dogs were anesthetized with 1.5% isoflurane (n = 12) or 8% desflurane (n = 6). A flow probe and balloon occluder were placed on the LAD artery. A probe that measured myocardial oxygen pressure was inserted into the middle myocardium in the LAD region. Myocardial oxygen consumption (MVO 2) was calculated as LAD flow x arterial minus coronary sinus oxygen content. Measures and Main Results: Measures were made during hypotension produced by adenosine infusion, 2.8% isoflurane, or 14% desflurane with and without LAD constriction to decrease blood flow 30%. Without LAD artery constriction, adenosine infusion increased LAD flow 90% and MVO 2 70%, 2.8% isoflurane produced no change in MVO 2, and 14% desflurane decreased MVO 2 25%, but no treatment changed PmO 2. LAD artery constriction decreased PmO 2 50% by itself. Adenosine infusion during LAD constriction decreased tissue oxygen pressure an additional 60%, 2.8% isoflurane produced no change, and 14% desflurane increased PmO 2 100%. Conclusion: There was an inverse relationship between the effect of adenosine, 2.8% isoflurane, and 14% desflurane on MVO 2 and PmO 2 during ischemia. This is consistent with reports that increasing oxygen demand worsens myocardial ischemia.