Influence of Propranolol Plasma Levels on Hemodynamics during Coronary Artery Bypass Surgery

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Abstract
Hemodynamic effects of propranolol during coronary artery surgery were investigated in 26 patients who chronically took propranolol and who received a standardized morphine/diazepam/pancuronium/halothane anesthetic. Effects were shown by correlating logarithm of the plasma propranolol concentrations vs. percentage change in hemodynamics following stressful events (induction, intubation, skin incision, sternotomy and sternal retraction). Log propranolol and hemodynamics following cardiopulmonary bypass also were correlated. A broad range of propranolol levels were observed. Levels (range and mean) were preinduction 0-96 (25.6 .+-. 21.6) ng/ml; preincision 0-86 (27.2 .+-. 24.4) ng/ml. The range of hemodynamic responses to stressful events also was broad. Representative changes between preincision control and sternotomy were (range and mean): HR [heart rate]-8-30 (7 .+-. 10) beats/min; PCWP [pulmonary capillary wedge pressure] 1-21 (8.5 .+-. 4.6) mm Hg; CI -0.2-1.1 (-0.2 .+-. 0.7) 1 .cntdot. min-1 .cntdot. m-2, and SVR [systemic vascular resistance]-244-1,288 (310 .+-. 388) dyn .cntdot. s .cntdot. cm-5. By the time of sternal retraction, CI had declined from preincision values in 14 patients. Linear regression analysis demonstrated an inverse correlation between log propranolol and magnitude of HR, MAP, [mean arterial pressure], PCWP and CI response to stressful stimulation. A direct but statistically weaker correlation with SVR also was seen. Significant correlations between log propranolol vs. hemodynamic response to anesthetic induction and vs. postcardiopulmonary bypass hemodynamics were not observed. Evidently propranolol, in proportion to the log plasma level, attenuated stress-induced changes in HR and to a lesser degree changes in MAP, PCWP and CI and at higher levels this effect was achieved with some decline in CI and increase in SVR.