SYSTEMIC VASCULAR EFFECTS OF ISOFLURANE VERSUS PROPOFOL ANESTHESIA INDOGS

Vascular effects of general anesthesia are usually described by change s in vascular resistance, which assumes a linear pressure-flow relatio nship passing through the zero-flow zero-pressure point, and neglects the pulsatile properties of the circulation. We compared the systemic vascular effects of isoflurane versus propofol anesthesia by measureme nts of aortic pressure-flow relationships, systemic vascular impedance (SVZ), and pressure transfer function (PTF). Eight mechanically venti lated dogs received isoflurane 1.4% end-tidal and propofol 18 mg . kg( -1). h(-1) in a random sequence. During both periods, pressure-flow da ta and SVZ data were obtained at baseline and after stepwise reduction of the cardiac output by inflation of a balloon in the inferior vena cava. Instantaneous pressure and flow were measured at the aortic root using a micromanometer-tipped catheter and an ultrasonic flow probe. Compared to baseline, low flow decreased the aortic pressure and incre ased the resistance, characteristic impedance, and oscillatory/total w ork ratio. Compared with isoflurane, propofol resulted in higher aorti c pressure, lower characteristic impedance, and lower oscillatory/tota l work ratio. Low-frequency PTF moduli decreased at low flow and incre ased with propofol. We conclude that, compared with isoflurane, propof ol better preserves aortic pressure and increases aortic compliance, a nd thus improves the energy transmission from the left ventricle to th e arterial system.