Endotoxemia leads to pulmonary hypertension, which is a result of constriction of proximal pulmonary arteries during the early phase, whereas the late phase is characterised by a decline in distal pulmonary vasculature compliance.
The dopamine alpha- and beta-adrenoceptor dose-response curves are investigated in four patients who are exempt from cardiovascular disease. A dose-related increase in CO, HR and SV is observed with infusion rates of up to 3 micrograms kg-1 min-1. With concentrations greater than 10 micrograms kg-1 min-1, both BP and SVR increase. Low-dose dopamine infusion less than 3 micrograms kg-1 min-1 is investigated in ten other patients. With this infusion rate, a selective renal vasodilation is induced without peripheral or cardiac beta-adrenoceptor activation. Dopamine is responsible for an increase in diuresis FENa, GFR and RBF. These properties are indicated in renal failure, and when haemodynamic support is required in cardiac failure, if an infusion rate of up to 10 micrograms kg-1 min-1 is able to reverse cardiac insufficiency.
Lumped models are frequently used to provide a satisfactory description of the hemodynamic properties of the pulmonary vasculature. The purpose of this study is to describe a method to identify simultaneously the parameters values of windkessel models components. The following equation was used to obtain R1 (characteristic resistance), R2 (peripheral resistance), C (total compliance) and L (inertance): [formula: see text] where ki are the following functions of L, R1, R2 and C: [formula: see text] To assess the accuracy of the method, estimates of R1, R2, and C were compared to characteristic impedance Rc, vascular resistance PVR and pulmonary arterial compliance Cd respectively computed from referenced methods. Comparison between R1 and Rc, PVR and R1 + R2, C and Cd were obtained in 5 anaesthetised pigs during basal conditions and after endotoxin-shock. The results indicate that in both conditions, comparisons evidenced highly significant correlations between values computed by the different approaches (p < 0.0001). Although our method yielded to consistently lower values than values provided by referenced methods, the results were concordant with respect to the expected response of pulmonary vasculature to endotoxin insult. We conclude that our method of identification is suitable for the assessment of lumped parameters windkessel model estimates. The main interest is that actual resistance and compliance values can be obtained easily and simultaneously by a global method approach.
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