Haemodynamic adaptation at rest and during exercise to long-term antihypertensive treatment with combined alpha- and beta-adrenoreceptor blockade by labetalol.

The effects on systemic and pulmonary haemodynamics of treatment with the alpha-and beta-adrenoceptor blocker labetalol for 20 months were studied in 9 hypertensive men aged 49 to 57 years, at rest in the supine and upright position and during exercise in the sitting position at 62 and 124 Watts. Pressures were recorded by means of catheters inserted percutaneously into the pulmonary and brachial artery, and cardiac output was determined by the Fick method.