Hypertensive emergencies.

Sustained, severe hypertension increases the risk of stroke and renal insufficiency in all patients, and may lead to aortic dissection or accelerated ischemic heart disease in patients with underlying vascular disease. In many situations, such hypertension demands urgent, immediate blood pressure reduction. In some cases, a gradual lowering of blood pressure is not only preferable, but is essential in preventing damage from overzealous therapy. Effective treatment of mild to moderate hypertension would prevent the great majority of hypertensive crises.