BACKGROUND: Although arterial hypotension occurs frequently with propofol use in humans, its effects on intravascular volume and vascular capacitance are uncertain. We hypothesized that propofol... Show moreBACKGROUND: Although arterial hypotension occurs frequently with propofol use in humans, its effects on intravascular volume and vascular capacitance are uncertain. We hypothesized that propofol decreases vascular capacitance and therefore decreases stressed volume.METHODS: Cardiac output (CO) was measured using Modelflow(®) in 17 adult subjects after upper abdominal surgery. Mean systemic filling pressure (MSFP) and vascular resistances were calculated using venous return curves constructed by measuring steady-state arterial and venous pressures and CO during inspiratory hold manoeuvres at increasing plateau pressures. Measurements were performed at three incremental levels of targeted blood propofol concentrations.RESULTS: Mean blood propofol concentrations for the three targeted levels were 3.0, 4.5, and 6.5 µg ml(-1). Mean arterial pressure, central venous pressure, MSFP, venous return pressure, Rv, systemic arterial resistance, and resistance of the systemic circulation decreased, stroke volume variation increased, and CO was not significantly different as propofol concentration increased.CONCLUSIONS: An increase in propofol concentration within the therapeutic range causes a decrease in vascular stressed volume without a change in CO. The absence of an effect of propofol on CO can be explained by the balance between the decrease in effective, or stressed, volume (as determined by MSFP), the decrease in resistance for venous return, and slightly improved heart function.CLINICAL TRIAL REGISTRATION: Netherlands Trial Register: NTR2486. Show less
Martini, C.H.; Boon, M.; Bevers, R.F.; Aarts, L.P.; Dahan, A. 2014
OBJECTIVE We present a new physiological model that discriminated between changes in the systemic arterial and venous circulation. To test our model, we studied the effects of dobutamine and... Show moreOBJECTIVE We present a new physiological model that discriminated between changes in the systemic arterial and venous circulation. To test our model, we studied the effects of dobutamine and hypovolemia in intact pentabarbital-anesthetized piglets. METHODS Aorta pressure (Pao), central venous pressure (Pcv), mean systemic filling pressure (Pmsf) and cardiac output (CO), were measured in 10 piglets, before, during and after dobutamine infusion (6 µg kg⁻¹ min⁻¹), as well as during hypovolemia (-10 mL kg⁻¹), and after fluid resuscitation to normovolemia. Venous (Rv) and total systemic (Rsys) resistance were determined from Pao, Pcv, Pmsf and CO. The quotient of Rv/Rsys was used to determine the predominant location of vascular changes (i.e. vasoconstriction or dilatation on either venous or arterial side). RESULTS Administration of dobutamine increased heart rate and CO, whereas it decreased Pmsf, Rsys, Rv and Rv/Rsys. The decrease in Rv was significantly greater than Rsys. Pao and Pcv did not change. Hypovolemia decreased CO, Pcv, Pmsf, Rv and Rv/Rsys, but kept Rsys constant and increased heart rate. CONCLUSIONS Hypovolemia and dobutamine differentially alter Pmsf, Rsys, Rv and Rv/Rsys ratio. The increase in CO during dobutamine infusion was attributed to the combined increased cardiac function and decreased Rv. The decrease in CO with hypovolemia was due to a decreased Pmsf but was partly compensated for by a decrease in Rv tending to preserve venous return and thus CO. Show less
