Hypertensive emergencies. Etiology and management.

Although systemic hypertension is a common clinical disorder, hypertensive emergencies are unusual in clinical practice. Situations that qualify as hypertensive emergencies include accelerated or malignant hypertension, hypertensive encephalopathy, acute left ventricular failure, acute aortic dissection, pheochromocytoma crisis, interaction between tyramine-containing foods or drugs and monoamine oxidase inhibitors, eclampsia, drug-induced hypertension and possibly intracranial hemorrhage. It is important to recognize these conditions since immediate lowering of systemic blood pressure is indicated. The diagnosis of hypertensive emergencies depends on the clinical manifestations rather than on the absolute level of the blood pressure. Depending on the target organ that is affected, the manifestations of hypertensive emergencies can be quite expressive, yet variable. Thus, the physician has to make the clinical diagnosis urgently in order to render appropriate therapy. Several parenteral drugs can quickly and effectively lower the blood pressure in hypertensive emergencies. Intravenous fenoldopam, a selective dopamine (DA1) receptor agonist, offers the advantage of improving renal blood flow and causing natriuresis. Intravenous nicardipine may be beneficial in reserving tissue perfusion in patients with ischemic disorders. Whereas trimethaphan camsilate is the drug of choice for managing acute aortic dissection, hydralazine remains the drug of choice for the treatment of eclampsia. The alpha-adrenoceptor, phentolamine, is useful in patients with pheochromocytoma crisis. Enalaprilat is the only ACE inhibitor available for parenteral use and may be particularly useful in treating hypertensive emergencies in patients with heart failure. However, ACE inhibitors may cause a precipitous fall in blood pressure in patients who are hypovolemic. Although useful as adjunctive therapy in hypertensive crises, diuretics should be used with caution in these patients because prior volume depletion may be present in some conditions such as malignant hypertension. The treating physician should be familiar with the pharmacological and clinical actions of drugs which are indicated for and useful in the treatment of hypertensive emergencies. Once the patient's situation has stabilized, the patient may be switched to an oral medication and the physician should discuss long term follow up plans. With appropriate clinical diagnosis, hypertensive emergencies can be successfully treated and the complications can be prevented with timely intervention.