Hypertensive Urgencies and Emergencies
Hypertensive urgencies and emergencies are defined by the necessity to reduce blood pressure quickly to prevent target organ damage, not by an absolute blood pressure level. Elevated blood pressure in and of itself without symptoms or signs of target organ damage does not usually require aggressive therapy. Aggressive blood pressure reduction in a patient who presents with incidentally noted elevated blood pressure is inappropriate in the absence of a true urgency or emergency. It is of particular importance to obtain an accurate blood pressure measurement to avoid overdiagnosis of a hypertensive emergency when none is present (e.g., to consider the possibility of pseudohypertension as just discussed). It is possible to produce complications such as orthostatic hypotension or coronary or cerebral hypoperfusion syndromes resulting from treating an elderly patient with elevated blood pressure too aggressively.
Hypertensive urgencies are more common than true hypertensive emergencies. These are defined as situations in which blood pressure should be lowered within 24 h to prevent the risk of target organ damage, such as accelerated or malignant hypertension without symptoms or evidence of ongoing target organ damage.
The majority of these situations may be managed as with oral administration of antihypertensive medications but generally necessitate a hospitalized setting for frequent blood pressure monitoring. The medications recommended for this situation include nifedipine, clonidine, labetalol, and captopril. Because no additional benefit has been noted with the use of sublingual administration of any of these agents and the more rapid onset of action may unpredictably produce a deleterious reduction in blood pressure, the oral dosage forms, which are effective within 15 to 30 min, are recommended. It should be noted that the blood pressure need not be reduced to normal levels within 24 h; indeed, an attempt to do so carries with it the risks of complications from coronary or cerebral hypoperfusion.
Examples of true hypertensive emergencies in older patients include hypertensive encephalopathy, intracranial hemorrhage, acute heart failure with pulmonary edema, dissecting aortic aneurysm, and unstable angina. These situations present with symptoms and signs of vascular compromise of the affected organs: brain (symptoms of severe headache, altered vision, altered mental status, and severe hypertensive retinopathy including papilledema, or focal neurologic signs), heart (symptoms and signs of left ventricular failure or angina), or kidney (presenting as acute renal failure).
The goal of treatment in these emergent clinical situations is immediate reduction in blood pressure, although again not necessarily to a normal level. The management of these conditions usually requires an acute hospital setting to permit the parenteral administration of an antihypertensive agent and continuous blood pressure monitoring by either arterial line, automatic cuff, or oscillometric (Finapres) devices. Intravenous nitroprusside has been the most widely utilized of these medications.<!- adv ->
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Its onset of action is essentially immediate, it has a very short duration of action, and its rate of infusion may be titrated to result in a carefully controlled reduction in blood pressure over a 30- to 60-min period. Prolonged nitroprusside administration is limited by the accumulation of a thiocyanate metabolite and the risk of cyanide toxicity. Intravenous nitroglycerine is an alternative for longer duration of therapy. Additional parenteral alternatives include labetalol, enalaprilat, and hydralazine.
In addition, for patients with evidence for fluid overload, parenteral loop diuretics may aid in achieving blood pressure control. Once the hypertensive emergency or urgency has been managed, the next steps are an evaluation to attempt to determine an explanation for the increase in blood pressure (i.e., a workup for secondary causes paying particular attention to the possibility of renovascular hypertension, assessment of adherence with the antihypertensive regimen, and evaluation of resistant hypertension) and developing a plan to achieve effective blood pressure control with appropriate close patient follow-up and monitoring.