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.