Emergency Room Management of Hypertensive Urgencies and Emergencies
BY: Donald G. Vidt, MD
[J Clin Hypertens 3(3):158-164, 2001. © 2001 Le Jacq Communications, Inc.]
Introduction
Hypertensive crisis affects upward of 500,000 Americans each year. Although the incidence of hypertensive crisis is low, affecting fewer than 1% of hypertensive adults, more than 50 million adult Americans suffer from hypertension. Presentation of a patient with severe hypertension to the emergency room demands immediate evaluation, prompt recognition of a hypertensive emergency or urgency, and the prompt institution of appropriate therapeutic measures to prevent progression of target-organ damage and to avoid a catastrophic event. Hypertensive emergencies are severe elevations in blood pressure that are complicated by evidence of progressive target-organ dysfunction such as coronary ischemia, disordered cerebral function, a cerebrovascular event, pulmonary edema, or renal failure. Although therapy with parenteral antihypertensive agents may be initiated in the emergency department, these patients warrant prompt admission to an intensive care unit where continuous monitoring of blood pressure can be assured during therapy.
Hypertensive urgencies are severe elevations in blood pressure without evidence of progressive target organ dysfunction and can usually be managed by orally administered medications initiated in the emergency department with appropriate follow-up within 24 hours, to several days depending upon individual characteristics of the patient. Elevated blood pressure alone rarely requires emergency therapy.[1]
Most hypertensive urgencies or emergencies are preventable and are the result of inadequate treatment of mild to moderate hypertension or nonadherence to antihypertensive therapy.[2,3] In a few cases, a previously unrecognized form of secondary hypertension, such as renal vascular hypertension or pheochromocytoma, and rarely, primary hyperaldosteronism, may be responsible and will obviously require early recognition if specific therapy is to be initiated. Prompt emergency room evaluation is undertaken to identify the clinical status of the patient, to provide clues to an underlying etiology of the hypertension, to assess the degree of target organ involvement, and to select the most appropriate pharmacologic agent and method of administration.
Assessments
Initial
Early triage is critical in an effort to assure the most timely and appropriate therapy for each patient.[4] A brief but thorough history should address the duration as well as the severity of hypertension, all current medications, including prescription and nonprescription drugs, and the use of recreational drugs. A history of other co morbid conditions and prior cardiovascular or renal disease is critical to the initial evaluation.
Direct questioning regarding the level of compliance with current antihypertensive medications may establish inadequacy of therapy. Frequent or continuous monitoring of blood pressure should be established. Look for historical information regarding neurologic, cardiovascular, and/or renal symptoms and look for specific manifestations, such as headache, seizures, chest pain, dyspnea, and edema.
Physical
Physical assessment should start with an assessment of blood pressure, with an appropriate size cuff, in both upper extremities. Brachial, femoral, and carotid pulses should be measured. A careful cardiovascular examination as well as a thorough neurologic examination, including mental status, should be conducted. This assessment should establish the degree of involvement of affected target organs and should provide clues to the possible existence of a secondary form of hypertension, such as renal vascular hypertension. If a secondary cause of hypertension is suspected, appropriate blood and urine samples should be obtained before aggressive therapy is initiated. A careful funduscopic examimation should be performed to detect hemorrhages, exudates, and/or papilledema.
Initial Laboratory Studies
A urinalysis with sediment examination, a stat chemistry profile, and an electrocardiogram, together with a complete history and thorough physical examination, should enable a clinical assessment of the degree of target orgainvolvement and should facilitate the selection of an appropriate antihypertensive agent for initial treatment. The urinalysis may show significant proteinuria, red blood cells, and/or cellular casts. Cellular casts are suggestive of renal parenchymal disease. Electrolyte abnormalities, particularly hypokalemia or hypomagnesemia, increase the risk of cardiac arrhythmias, and the chemistry profile will also provide evidence of renal dysfunction.
The electrocardiogram should identify evidence of coronary ischemia and left ventricular hypertrophy, and pulse deficits should raise the question of aortic dissection. A computed tomographic (CT) scan of the head should be considered when the clinical examination suggests cerebrovascular ischemia or hemorrhage, or in the comatose patient. The decision to treat as a hypertensive emergency should prompt immediate admission to an intensive care unit where continuous monitoring of blood pressure can be established for subsequent parenteral treatment of the hypertensive emergency.
The clinical characteristics of the hypertensive emergency are listed in Table I. The level of blood pressure alone does not determine a hypertensive emergency; rather, it is the degree of target organ involvement that determines the rapidity with which blood pressure should be reduced to a safer level to prevent or limit target organ damage. Initial therapy will often be based on a presumptive diagnosis based on the information available during the initial triage evaluation (Table II). Blood pressure reduction should not be delayed until the results of all diagnostic studies are available for review, but rather should be initiated as soon as the patient's clinical status is established.
Hypertensive Emergencies
The initial goal for blood pressure reduction is not to obtain a normal blood pressure, but rather to achieve a progressive but controlled reduction in blood pressure to minimize the risk of hypoperfusion in cerebral, coronary, and renal vascular beds.[5] It is recommended that the initial reduction in mean arterial pressure (MAP) not be more than 20%-25% below the pretreatment blood pressure, or that MAP be reduced within the first 30-60 minutes to 110-115 mm Hg.6 If this level of blood pressure is well tolerated and the patient is clinically stable, further gradual reductions toward a normal blood pressure can be effected over the next 12-24 hours. Excessively rapid reduction in blood pressure has been associated with acute deterioration in renal function, ischemic, cardiac, or cerebral events, and occasional retinal artery occlusion and acute blindness.
Hypertensive Urgencies
The caveat with hypertensive urgencies is that "elevated blood pressure alone rarely requires emergency therapy." The initial triage should identify those patients who have an elevated blood pressure without any evidence of significant target organ damage and no evidence of other impending cardiovascular events (Table II). An effort should be made to separate out those patients with severely elevated blood pressure and clinical evidence of target organ damage who may benefit from a period of observation in the emergency department following the administration of one or several oral medications to reduce blood pressure over a period of several hours. If clinically stable, these patients can safely be sent home with oral medications, with arrangements made for a follow-up visit within 24 hours in an outpatient setting. Several oral agents can provide a rapid response in blood pressure within 1-3 hours. Control efforts can then be continued under the supervision of a primary physician.Most patients with hypertensive urgencies are previously diagnosed hypertensives who are either noncompliant with therapy or are receiving inadequate therapy to control blood pressure. Further evaluation, if needed, can then be performed in the outpatient setting.
To discharge the patient from an emergency room without a confirmed follow-up appointment is a missed opportunity to get that patient back into treatment, and optimal control of blood pressure should be a management goal. For the patient with elevated blood pressure and no evidence of target organ damage or other acute cardiovascular problems, reassurance and a period of observation in the emergency department may be appropriate, particularly if an anxiety-related event is suspected. For those patients inadequately treated or noncompliant with therapy, medication may be resumed or modified and arrangements made for outpatient follow-up within several days. For the occasional patient with previously undiagnosed hypertension, efforts should be made to confirm access to a primary physician for follow-up blood pressure screening and evaluation, if indicated. For most patients who are noncompliant with therapy or undertreated by their primary physician, the recommendations outlined in the Joint National Committee VI Guidelines are appropriate.[1]
Oral Agents for Hypertensive Urgencies
The following oral agents can be used for hypertensive urgencies (see Table III).[7] Captopril, an angiotensin-converting enzyme inhibitor, is well tolerated and has effectively reduced blood pressure in hypertensive urgencies. Given by mouth, captopril is usually effective within 15-30 minutes and may be repeated in 1-2 hours dependingupon the response.[8] The drug has been administered sublingually, in which case the onset of action may occur within 10-20 minutes, with the maximal effect reached within 1 hour. Administration may lead to acute renal failure in patients with bilateral renal artery stenosis, and reflex tachycardia may be observed. Responsiveness to this agent can be enhanced by the administration of a loop diuretic, such as furosemide.
Clonidine is a centrally acting a-adrenergic agonist with onset of action 30-60 minutes following oral administration and maximal effects seen within 2-4 hours. Although it is most commonly administered in a loading regimen of 0.1-0.2 mg followed by 0.1 mg hourly for several hours, evidence suggests that comparable responses may be seen with a single 0.2 mg dose.[3] The most common adverse effect seen in the acute setting is drowsiness, affecting up to 45% of patients. Clonidine may be a poor choice when monitoring of mental status is important. Dry mouth is also a common complaint and lightheadedness is occasionally observed.
Labetalol is a combined a- and b-adrenergic blocking agent. It can be effective given orally in a dose of 200-400 mg, which may be repeated after 2-3 hours. The onset of effect is observed within 1-2 hours.[9,10] Like any b blocking agent, it has the potential to induce heart block and to worsen symptoms of bronchospasm. Therefore, it should be avoided in patients with uncontrolled asthma or those with more than first-degree heart block, symptomatic bradycardia, or congestive heart failure. Prazosin is an a-adrenergic blocking agent that can have limited benefit in the early management of pheochromocytoma. Side effects include first-dose syncope, palpitations, tachycardia, and orthostatic hypertension.
Agents for Hypertensive Emergencies
Parenteral Agents
The following parenteral agents are effective in treating hypertensive emergencies (see Table IV).[7] Labetalol has proved particularly effective when used in bolus intravenous injections in the initial treatment of hypertensive emergencies, and can provide a controlled reduction in blood pressure to a predetermined goal.[11] Once a goal pressure is achieved, injections are stopped, and the long duration of action facilitates conversion to effective oral therapy. The infusion of labetalol at a rate of 2 mg per minute offers an alternative method of administration and is associated with a gradual yet controlled reduction in blood pressure.[12] Because b blocking effects predominate with this agent, bradycardia or heart block may occur in patients with intrinsic heart disease.
Sodium nitroprusside is a potent vasodilator and an exceptionally predictable agent when administered in a hypertensive crisis of any etiology.[5,13] The drug has an extremely rapid onset of action, within seconds of initiating an infusion, and a very rapid offset of effect within 1-2 minutes, which necessitates constant supervision of blood pressure. Its popularity relates in part to its effectiveness in reducing both preload and afterload and the ability to achieve a controlled titration of blood pressure. Nitroprusside does not cause sedation or somnolence but is rapidly degraded by light, requiring periodic exchange of solution.
One of the major concerns in using sodium nitroprusside is its metabolism to cyanogen and to thiocyanate. In patients with significant impairment in renal function, accumulation of thiocyanate may occur over several days, with toxic effects. In patients with impaired hepatic function and poor cardiac perfusion, cyanide poisoning has been reported.[14] Nicardipine, an intravenous form of the dihydropyridine calcium antagonist, has proved effective in a high percentage of hypertensive emergencies, particularly at higher infusion rates.[15] The growing popularity of this agent can be attributed to its ease of administration as a continuous infusion starting at 5 mg per hour. The infusion rate can be increased by 2.5 mg per hour at intervals of 15-20 minutes until a maximum recommended infusion rate of 15 mg per hour is obtained or until the desired reduction in blood pressure is achieved. An excellent correlation has been demonstrated between plasma concentration and dose response of diastolic blood pressure. The dosing of nicardipine is not dependent upon the patient's body weight. Nicardipine has been shown to reduce both cerebral and coronary ischemia, and headache, nausea, and vomiting may occur. Modest tachycardia may be observed.
Nitroglycerine may be of particular efficacy in hypertensive emergencies with coexistent coronary ischemia.[16] Nitroglycerine dilates collateral coronary vessels, and like nitroprusside, has a rapid onset and offset of effect, requiring close nursing supervision. When infused at low doses (5-10 mg per minute), nitroglycerine dilates capacitance vessels, whereas much higher infusion rates are required to affect arteriolar vasodilatation. The infusion rate may be increased at 3-5-minute intervals until the desired effect is achieved.
Nitroglycerine may be particularly useful in patients with severe coronary ischemia in whom blood pressures are only modestly elevated or in patients with postcoronary artery bypass hypertension. Tolerance to intravenous nitroglycerine may be observed within 24-48 hours of infusion, and unpredictable absorption in polyvinyl chloride containers and tubing necessitates the use of glass containers.
Fenoldapam is a unique, selective, peripheral dopamine-I receptor agonist that provides systemic vasodilation, particularly in the renal circulation, and also has effects on renal proximal and distal tubules.[17] It does not bind to dopamine II receptors or b adrenergic receptors, has no a-adrenergic agonist effects, but is an a-I antagonist and does not cross the blood-brain barrier. Compared to other parenteral antihypertensive agents, fenoldipine's unique effects on the kidney provide increased urine flow rate, sodium and potassium excretion, and creatinine clearance, making this agent particularly attractive in hypertensive emergencies with renal impairment.
Clinical studies have suggested that fenoldapam is as effective as sodium nitroprusside in improving cardiac hemodynamics in patients with acute, severe congestive heart failure.[18] The onset of clinical effect is usually seen within 5 minutes and affects dissipate within 30 minutes following discontinuation of the infusion. Side effects include headache, flushing, tachycardia, and dizziness. Bradycardia has occasionally been noted and a dose-related increase in intraocular pressure has been observed in normotensive and hypertensive patients. Inactive metabolites are primarily eliminated in the urine and no dosage adjustments are required for patients with renal or hepatic impairment. Hydralazine should be restricted to pregnant women with pre-eclampsia. Five to 10 mg may be administered intravenously as a bolus injection and may be repeated.[19] The major advantage is this agent's ability to improve uterine blood flow. Hydralazine is contraindicated in patients with coronary atherosclerosis, and administration is associated with reflex tachycardia, sodium and water retention, and intense flushing. Headache and increased intracranial pressure have also been observed.
Other Agents
Enalaprilat, the active form of enalapril, is administered intravenously in a dose of 1.25 mg administered at 6-hour intervals. The onset of action is seen within 30 minutes and the response to enalaprilat in hypertensive emergencies is unpredictable, in part because of variable degrees of plasma volume expansion. This agent may be particularly useful in hypertensive emergencies associated with congestive heart failure or high plasma angiotensin II concentrations.
Esmolol is an intravenous, ultra-short-acting b-adrenergic blocker. Onset of effect is seen within 1-5 minutes, with a rapid offset of effect within 15-30 minutes following discontinuation. Esmolol is administered as a 500 mg/kg bolus injection, which may be repeated after 5 minutes. Alternatively, an infusion of 50-100 mg/kg/min may be initiated and increased to 300 mg/kg/min as needed. Adverse effects include increased heart block, congestive heart failure, and bronchoconstriction.
Phentolamine, a nonselective a-adrenergic blocking agent, is reserved today for use in suspected excess catecholamine states, such as pheochromocytoma. It may be useful as a diagnostic agent administered as a bolus injection of 5-10 mg in patients with suspected pheochromocytoma. Acute blood pressure lowering will be seen within several minutes and may last 10-30 minutes. Tachycardia is a common occurrence and may precipitate myocardial ischemia. Nitroprusside and labetalol are more easily titrated in the management of hypertensive emergencies associated with high circulating levels of catecholamines; therefore, phentolamine is rarely utilized therapeutically today.
Diazoxide is rarely used today in the treatment of hypertensive emergencies. Although a potent vasodilator, large doses of 300 mg were often associated with severe hypotension. Smaller mini-boluses of 50 mg administered every 10-15 minutes can provide a controlled reduction in blood pressure but can cause reflex tachycardia, hyperglycemia, hyperuricemia, and sodium and water retention. Diazoxide offers no advantage over several other agents that have more acceptable adverse effect profiles.
Summary
Patients presenting to emergency departments with severe hypertension deserve prompt triage to establish the presence of a hypertensive emergency or urgency. Those with hypertensive emergencies must be promptly admitted to an intensive care unit where continuous monitoring of blood pressure is available, as well as prompt therapy with parenteral antihypertensive drugs to prevent progression of target organ damage. Most patients with hypertensive urgencies can be managed on an ambulatory basis with initiation or adjustment of appropriate oral antihypertensive therapy. A key to the management of hypertensive urgencies is the assurance of appropriate follow-up care to assure continued optimal hypertension management.
From the Cleveland Clinic Foundation, Cleveland,and Ohio State University, Columbus, OH Address for correspondence/reprint requests: Donald G. Vidt, MD, Cleveland Clinic Foundation,9500 Euclid Avenue, Cleveland, OH 44195
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