EFFECTS OF PROPOFOL AND THIOPENTAL ON CORONARY BLOOD-FLOW AND MYOCARDIAL PERFORMANCE IN AN ISOLATED RABBIT HEART

Background. Some clinical and experimental studies suggest that propof ol decreases myocardial contractility and relaxation, whereas others r eport preserved cardiac function. To investigate the effects of propof ol on intrinsic contractility and relaxation, increasing concentration s of propofol were infused in isolated blood-perfused rabbit hearts. E quimolar concentrations of thiopental were infused as a reference grou p. Methods. Coronary blood flow, left ventricular contractility and re laxation (as maximal positive and negative left ventricular pressure d erivatives [dP/dt(max) and dP/dt(min)], respectively), and myocardial oxygen consumption (MvO2) were measured during infusion of 10-1,000 mu M propofol in blood-perfused hearts. To determine whether the effects of propofol depend on the heart's perfusate, propofol also was infused in isolated buffer-perfused rabbit hearts. In addition, the effects o f propofol solvent were investigated in blood- and buffer-perfused pre parations. Results. In blood-perfused preparations, coronary blood flo w increased with propofol concentrations greater than 30 mum and with 300 and 1,000 mum thiopental. Left ventricular dP/dt(max) and dP/dt(mi n) remained unchanged with propofol and decreased with concentrations of thiopental equal to or greater than 30 mum. MvO2 increased with 1,0 00 muM propofol, whereas coronary venous oxygen tension and content re mained unchanged. MvO2 decreased with thiopental associated with a sig nificant increase in coronary venous oxygen tension and content. In si x buffer-perfused hearts, basal coronary blood flow was much greater a nd MvO2 less than in blood-perfused hearts. Left ventricular dP/dt(max ) and dP/dt(min) decreased with 30, 100, and 300 muM propofol. Propofo l vehicle did not change coronary blood flow, myocardial performance, or MvO2 of blood- or buffer-perfused hearts. Conclusions. When compare d to a reference drug such as thiopental, propofol did not depress the myocardial performance of blood-perfused rabbit hearts. The type of t he perfusate (blood vs. buffer), however, had a major influence on the myocardial effects of propofol.