[Hypertensive crises. 1. Pathogenesis and symptomatology].

Hypertensive crisis is a medical emergency presenting with a severely increased blood pressure. The condition is associated with a state of increased vasoconstriction, coexisting hyponatriaemia and hypovolaemia. Besides the absolute level of blood pressure evidence of organ damage is also important in initial judgement of the case. Hypertensive crises are most commonly seen in younger patients with essential hypertension and in patients with secondary hypertension. It is unknown why a patient with hypertension suddenly develops a hypertensive crisis, but the renin-angiotension system seems to play an important role. Untreated, the disease will lead to irreversible end-organ damage. Hypertensive crises may be divided into "hypertensive emergencies" with evidence of severe new and/or progressive end-organ damage, requiring careful reduction of blood pressure within an hour, and "hypertensive urgencies" with no evidence of end-organ damage or complications where reduction of blood pressure to a safe level must be achieved within a few hours.