Treatment of severe hypertension and hypertensive emergencies with intravenous clonidine hydrochloride.

Eleven severely hypertensive patients, median age 54 years, were treated with intravenous (i.v.) clonidine hydrochloride (Catapres). In nine there were life-threatening complications: severe left ventricular failure (LVF), hypertensive encephalopathy, cerebral haemorrhage, dissecting aortic aneurysm, renal failure, and severe epistaxis. In two patients there was pronounced, but uncomplicated, elevation of blood pressure. 0·15 mg or 0·3 mg clonidine was given every 40 min with electrocardiographic (ECG) monitoring. The mean systolic and diastolic blood pressures in the eleven patients were respectively 266 and 165 mmHg before treatment falling to 165 and 109 mmHg after treatment (P < 0·001). The mean decrease in heart rate was 26 beats/min (P < 0·001). Doses of clonidine required for control ranged from 0·15 mg (one ampoule) to 0·9 mg (mean 0·56 mg), although one patient received a total of 0·9 mg without an adequate response. The presenting condition caused the eventual death of two patients. There were no serious side effects, except for one transient episode of sino-atrial heart block. It is concluded that clonidine is effective and safe in the treatment of hypertensive emergencies.