[Preoperative treatment with beta-receptor blockers and isoflurane anesthesia. Hemodynamic interactions in patients...

Although many patients undergoing general anesthesia and surgery are pretreated with beta-adrenoceptor blocking drugs, hemodynamic interactions of beta-blockers and volatile anesthetics have so far only been studied in animals. We therefore designed a clinical study to evaluate the relationship between the extent of preoperative beta-adrenoceptor blockade and the hemodynamic effects of isoflurane anesthesia. Sixty-one patients with coronary artery disease (CAD) and normal global left ventricular function scheduled for elective myocardial revascularization were studied immediately prior to surgery. One group of patients (n = 39) had been treated with beta-adrenoceptor blocking agents for at least 3 weeks up to and including the day of surgery. The degree of clinical beta-adrenoceptor blockade was quantified using the isoproterenol sensitivity test. The dose of isoproterenol required to increase heart rate by 25 beats/min was defined as the chronotropic dose 25 (CD25), representing the degree of beta-adrenoceptor blockade. Hemodynamic data were collected before and during isoflurane anesthesia (0.5%-0.6% end-tidal) plus 50% nitrous oxide. Twenty-two patients without preoperative beta-blocker therapy served as a control group. Preanesthetic values of cardiac index (CI), heart rate (HR) and mean arterial pressure (MAP) were lower in patients pretreated with beta-blocking drugs, but statistically these differences were not significant when compared to data obtained in unblocked patients. Isoflurane anesthesia caused significant reductions of CI and arterial blood pressure. However, there were no significant differences in the absolute values or the percentage changes compared to baseline data obtained in awake patients between the two groups.(ABSTRACT TRUNCATED AT 250 WORDS)