Haemodynamic response to ACTH administration in essential hypertension.
1. The haemodynamic and volume response to ACTH administration was investigated in six patients with mild, untreated essential hypertension and two patients with Addison's disease on maintenance steroids. Blood pressure, heart rate and weight were recorded daily. Plasma volume (125I-HSA) and cardiac output (thermo-dilution) were measured during the control period and on the 5th day of ACTH treatment. 2. In the hypertensive subjects, mean arterial pressure rose from 94.3 +/- 2.2 to 105.7 +/- 2.8 mmHg on the 5th day of ACTH administration (P less than 0.02). Plasma volume rose from 29.8 +/- 2.2 to 34 +/- 2.2 ml/kg. Cardiac index increased from 2.85 +/- 0.21 to 3.32 +/- 0.14 l/min per m2 (P less than 0.05). Cardiac output rose from 5.81 +/- 0.69 to 6.72 +/- 0.59 l/min. Calculated total peripheral resistance, heart rate and body weight were unchanged. No such changes were seen in patients with Addison's disease. 3. The haemodynamic characteristics of ACTH in patients with mild untreated essential hypertension are similar to those in the experimental model of ACTH induced hypertension in sheep.