Diuretics in cardiac oedema.

Cardiogenic oedema results from an increase in capillary hydrostatic pressure (either pulmonary or systemic). This increase produces a reduction in the plasma colloidosmotic pressure-capillary pressure gradient, facilitating the accumulation of fluid in the interstitial space and reducing the circulating plasmatic volume. The administration of diuretics to patients with acute ventricular dysfunction has both haemodynamic and renal effects, and causes a reduction in extravascular fluid. In chronic heart failure, the use of diuretics may result in a haemodynamic improvement once the volaemia is reduced. However, in some patients diuretics may cause activation of the neurohumoral axis and consequently a transient haemodynamic deterioration.