Hypertensive emergencies and urgencies: Pathophysiology and clinical aspects

A hypertensive urgency should be distinguished from a hypertensive emergency. Although the distinction may not always be obvious, certain guidelines may help the clinician determine which therapeutic approaches are most appropriate for each patient. Hypertensive emergencies include those conditions in which new or progressive severe end-organ damage is present and a delay in appropriate therapy might result in permanent damage, progression of complications, and a poor prognosis. Hypertensive urgencies include those conditions with minimal to no obvious end-organ damage in which blood pressure should be lowered expeditiously. The risk of immediate complications or organ damage is less likely to occur, and thus the immediate prognosis is better, although the ultimate prognosis, if untreated, is poor. There is a marked individual, racial, sexual, and age difference in the ability to tolerate high intraarterial pressure, as evidenced by patients' symptoms and signs of end-organ damage.Patients may have no symptoms of elevated blood pressure until significant intraarterial levels are reached. If symptoms are present, they may include headache, dizziness, blurred vision, shortness of breath (especially with exertion), chest pain, rapid pulse, palpitations, malaise and fatigue, nocturia, or pedal edema.^7,11–14 Signs of hypertensive disease vary and depend not only on the level of blood pressure but also include funduscopic changes with arteriolar narrowing, atrioventricular nicking, hemorrhages, exudates or papilledema, central nervous system changes and neurologic abnormalities, cardiac changes with gallop rhythm, cardiomegaly, tachycardia, ectopic ventricular beats, left ventricular hypertrophy or signs of congestive heart failure, pulmonary edema, and signs of renal insufficiency.^7,11–14Although there is a definite correlation between the level of blood pressure and end-organ damage, there is no definite systolic or diastolic level of blood pressure that induces end-organ damage. Some patients may tolerate very high blood pressures with few symptoms or signs, whereas others may manifest end-organ damage at lower blood pressures. Thus, the definition of hypertensive emergency and urgency depends on the clinical assessment of the blood pressure level and clinical and laboratory assessments of end-organ damage. The absolute blood pressure in itself does not determine the seriousness of the clinical situation, the expediency of treatment, or the need for in-hospital monitoring in a critical care unit.It is important not to lower the blood pressure precipitously or to a subnormal level particularly in patients with end-organ damage. Such treatment may critically reduce blood flow and perfusion to vital organs and induce a cerebrovascular accident, myocardial ischemia, or renal failure. A smooth, gradual reduction in blood pressure is crucial to patient management with oral or parenteral antihypertensive drugs. However, in hypertensive emergencies blood pressure control should be accomplished within 1 hour, whereas with hypertensive urgencies control should be within 24 hours.Those patients who have hypertensive emergencies with malignant hypertension and end-organ damage should be admitted to a hospital intensive care unit for evaluation and treatment. These patients have a diffuse arteritis, as of a result of their hypertension, that may take 4 to 6 weeks to heal. Many patients who present with diastolic blood pressure 120 mm Hg or greater will be found to have a secondary cause of hypertension (such as renovascular hypertension) after careful evaluation. On the other hand, those patients with hypertensive urgencies as defined previously can be treated in the emergency room or outpatient department and can avoid hospital admission. Careful, immediate, and routine follow-up is important in these patients.