THE INFLUENCE OF THORACIC EPIDURAL ANALGESIA ALONE AND IN COMBINATIONWITH GENERAL-ANESTHESIA ON CARDIOVASCULAR FUNCTION AND MYOCARDIAL-METABOLISM IN PATIENTS RECEIVING BETA-ADRENERGIC BLOCKERS

Thoracic epidural analgesia combined with chronic beta-adrenergic bloc ker medication may cause cardiac depression. We investigated the cardi ovascular and myocardial metabolic effects of a T1-T12 epidural block in 18 patients (age <65 yr, ejection fraction >0.5), receiving chronic beta-adrenergic blocker medication and scheduled for aortocoronary by pass surgery. After randomization into a light or deeper general anest hetic group, the cardiovascular and myocardial metabolic effects of a subsequent general anesthesia induction were investigated. Thoracic ep idural analgesia induced a moderate decrease in mean arterial pressure , coronary perfusion pressure, free fatty acids, and myocardial consum ption of free fatty acids. General anesthesia with thiopental (2-4 mg/ kg) and a low fentanyl dose (5 mug/kg) increased heart rate, coronary perfusion pressure, and coronary vascular resistance, whereas mean pul monary arterial pressure and pulmonary capillary wedge pressure decrea sed. After thiopental (2-4 mg/kg) and a high fentanyl dose (30 mug/kg) , mean arterial pressure and left ventricular stroke work index decrea sed. We conclude that a T1-T12 epidural block in well sedated, beta-ad renergic blocked patients does not induce clinically significant cardi ovascular effects. Induction of general anesthesia was well tolerated, but the light general anesthetic could not prevent an increase in hea rt rate and coronary vascular resistance, whereas the deeper anestheti c induced slight myocardial depression. No effect on the atrioventricu lar conduction, as measured by the PQ-time, was noted.