Intravenously administered vasodilators

As intravenous vasodilator infusions lower pulmonary artery and effective pulmonary capillary pressures, right ventricular function may be improved and interstitial edema formation reduced (Table 1). However, the intravenous use of conventional vasodilators such as nitroglycerin or epoprostenol is limited because of diffuse dilatation of the whole vasculature. Global vasodilatation of the pulmonary vasculature increases blood flow to areas of intrapulmonary shunt which further reduces the already compromised PaO2, particularly in patients with acute respiratory distress syndrome. Moreover, concurrent dilatation of the systemic vasculature may result in a dose-dependent arterial hypotension which may possibly lead to ventricular ischemia and consequent heart failure. Nevertheless, vasodilator agents play a major role in the therapeutic strategy of primary pulmonary hypertension. Continuous epoprostenol infusion not only improves the well being of patients considered for heart-lung transplantation, but also doubles median survival time ( Higenbottam,,,§!§/ 1.9.93).

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Table 1 Advantages and disadvantages of intravenous vasodilators

Vasodilator therapy is often required to treat increased pulmonary artery pressures after heart transplantation. Currently used intravenous vasodilators include epoprostenol (2-30 ng/kg/min), prostaglandin E ! (5-250 ng/kg/min), and sodium nitroprusside (0.3-2 g/kg/min). In patients without hemodynamic signs of acute right heart failure, as reflected by normal values of right ventricular end-diastolic volume, central venous pressure, stroke volume, and cardiac output, epoprostenol appears superior to NO inhalation and the best choice for intravenous vasodilator therapy after heart transplantation ( iKielerrJensen et...a/ 1995). Epoprostenol reduces both right and left ventricular outflow impedance, which is a desired effect in most transplanted patients ( 1,9.95).

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