LEFT-VENTRICULAR SYSTOLIC AND DIASTOLIC FUNCTION IS UNALTERED DURING PROPOFOL INFUSION IN NEWBORN SWINE

Propofol is a cardiac depressant with minimal diastolic effects in the adult myocardium. Cardiac effects of propofol in the newborn are unkn own. We examined hemodynamic variables and systolic and diastolic left ventricular function in 12 newborn pigs exposed to propofol at three different infusion rates (7.5, 15, and 30 mg.kg(-1).h(-1)) in random o rder with a background of fentanyl (100 mu g.kg(-1).h(-1)). Left ventr icular (LV) pressure (P-lv) and LV anterior-posterior dimension, deter mined by sonomicrometry, were continuously monitored. Mean arterial pr essure (MAP), heart rate (HR), and LV end-diastolic pressure (LVEDP) w ere determined at every infusion. Systolic function was assessed by th e maximal pressure-time derivative (dP/dt(max)), the slope of the end- systolic pressure-dimension relationship (ESP-D), and by the preload r ecruitable stroke work index (PRSWI). Diastolic function was assessed by relaxation indices, the minimal pressure-time derivative (dP/dt(min )) and the relaxation time constant (tau), and by a stiffness index, t he slope of the EDP-D relationship. MAP decreased approximately 25%, f rom 75.9 +/- 15.6 to 56.3 +/- 14.8 mm Hg (P < 0.05) with propofol, wit h no dose effect. HR and LVEDP were unchanged from control. Both dP/dt (max) and dP/dt(min) decreased with propofol infusion, but load-indepe ndent indices of systolic function (ESP-D slope and PRSWI) and tau wer e unchanged. Diastolic stiffness was not affected with either 7.5- or 30-mg.kg(-1).h(-1) infusions but decreased significantly from 0.27 +/- 0.18 mmHg/mm at control to 0.18 +/- 0.18 mm Hg/mm (P < 0.05) with pro pofol 15 mg.kg(-1).h(-1). With this profile, propofol may be useful fo r the newborn requiring anesthesia. Implications: Most anesthetics dep ress heart function in the newborn. We examined both heart contraction and relaxation during anesthesia with propofol in newborn pigs. Propo fol had minimal influence on heart function in this model at the doses studied. This may therefore be a useful anesthetic to test in the new born human.