Myocardial Circulatory and Metabolic Effects of Isoflurane and Sufentanil during Coronary Artery Surgery

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Abstract
The global and regional coronary hemodynamic and myocardial metabolic effects of isofluorane administered intraoperatively as an adjunct to sufentanil were studied in seven of nine patients who experienced increased systemic arterial pressure while undergoing elective coronary artery bypass grafting. All patients were premedicated and maintained on their preoperative medications (.beta.-blockers, nitates, Ca++ entry blockers) up to and including the morning of surgery. Systemic and pulmonary hemodynamics and global (coronary sinus, CS) and regional (great cardiac vein, GCV) coronary blood flows were measured, and blood samples were obtained for systemic and myocardial metabolic parameters: a) after induction with 30 mcg/kg of sufentanil and 0.12 mg/kg vecuronium (FIO2 1.0), but prior to incision (control); b) 5 min after sternotomy; and c) during ventilation with isoflurane-oxygen. Heart rate, cardiac output, stroke volume, and GCV/CS flow ratio did not change throughout the study. Neither global nor regional myocardial lactate production was detected in any patient at any time, and the electrocardiogram (lead II, V5) remained unchanged. In response to sternotomy, seven of nine patients experienced an increase in mean systemic arterial pressure of 20% or more (27 .+-. 3% from control values), due to an elevation in systemic vascular resistance (30 .+-. 5%). Coronary sinus (CS) and great vein (GCV) flows, as well as CS and GCV lactate extractions, were unchanged 5 min after sternotomy. Both global and regional myocardial oxygen extraction increased, while coronary venous oxygen content decreased. Isoflurane was administered in a dose that restored systemic arterial pressure to baseline values (inspired concentration 0.75-1.0%). Concomitantly, global and regional myocardial oxygen extraction and venous oxygen content returned toward control values. These data suggest that, in doses which produce no significant hypotension, isoflurane is a safe and effective adjunct for control of intraoperative elevation of systemic arterial pressure and vascular resistance during high dose sufentanil anesthesia in patients undergoing elective coronary artery bypass grafting.