The haemodynamic effects of clonidine in patients with grade III to IV hypertension.

In 10 patients (aged 46 to 72 years) with essential hypertension (grade III to IV), the acute effects on the haemodynamics in the systemic and pulmonary circulation were analysed following intravenous administration of clonidine. Pressure measurements in the right atrium (RA), right ventricle (RV), and the pulmonary artery (PA) were taken using cardiac catheterisation. Cardiac output was calculated according to the Fick principle.