Management of Hypertensive Emergencies

From: http://emedicine.medscape.com/article/1952052-overview#a30

Approximately 3-45% of adult patients have at least one incident of increased BP during their stay in the emergency department (ED). The fundamental principle in determining the necessary ED care of the hypertensive patient is the presence or absence of end-organ dysfunction. Many patients present to the ED with elevated BPs; however, only a small proportion of patients will require emergency treatment. An important point to remember in the management of the patient with any degree of BP elevation is to "treat the patient and not the number."
The primary goal of the emergency physician is to determine which patients with acute hypertension are exhibiting symptoms of end-organ damage and require immediate intravenous (IV) parenteral therapy. In contrast, patients presenting with acutely elevated BP (systolic BP [SBP] >200 mm Hg or diastolic BP [DBP] >120 mm Hg) without symptoms that are sustained throughout the ED stay and whose BP stays significantly elevated to this level on discharge should have initiation of medical therapy and close follow-up in the outpatient setting.[6]
Thus, optimal control of hypertensive situations balances the benefits of immediate decreases in BP against the risk of a significant decrease in target organ perfusion. The emergency physician must be capable of appropriately evaluating patients with an elevated BP, correctly classifying the hypertension, determining the aggressiveness and timing of therapeutic interventions, and making disposition decisions.
Acutely lowering BP in the ED for clinical situations other than those listed below is controversial and generally should be avoided.

Pharmacotherapy
An important point to remember in the management of the patient with any degree of BP elevation is to "treat the patient and not the number." In patients presenting with hypertensive emergencies, antihypertensive drug therapy has been shown to be effective in acutely decreasing blood pressure.[7]
Sodium nitroprusside is a commonly used medication. It is a short-acting agent, and the BP response can be titrated from minute to minute. However, patients must have constant monitoring in an intensive care unit. The potential exists for thiocyanate and cyanide toxicity with prolonged use or if the patient has renal or hepatic failure.
Diazoxide may also be used in hypertensive crisis. Small boluses of 100 mg are administered every 5 minutes, as indicated. Diazoxide is not preferred with concomitant congestive heart failure or low cardiac output.
Labetalol, an alpha- and beta-blocking agent, has proven to be quite beneficial in the treatment of patients with hypertensive emergencies. Labetalol is particularly preferred in patients with acute dissection. Boluses of 10-20 mg may be administered, or the drug may be infused at 1 mg/min until the desired BP is obtained. Once an adequate BP level is obtained, oral hypertensive therapy should be initiated, and patients are gradually weaned from parenteral agents.
Fenoldopam, a peripheral dopamine-1-receptor agonist is given as initial IV dose of 0.1 μg/kg/min titrated every 15 minutes.
Clevidipine, a dihydropyridine calcium channel blocker, is administered intravenously for rapid and precise BP reduction.[8] It is rapidly metabolized in the blood and tissues and does not accumulate in the body. Initiate IV infusion of clevidipine at 1-2 mg/h; titrate the dose at short intervals (ie, 90 s) initially by doubling the dose.
As the BP approaches its goal, increase the clevidipine dose by less than double, and lengthen the time between dose adjustments to every 5-10 minutes. An approximately 1-2 mg/h increase produces an additional 2-4 mm Hg decrease in SBP. Typically, the therapeutic response is achieved with 4-6 mg/h, although severe hypertension may require higher doses. Most patients have received maximum doses of 16 mg/h or less; experience is limited with short-term dosing as high as 32 mg/h. Because of lipid load restrictions, do not exceed 1000 mL or an average of 21 mg/h within a 24-hour period; experience is limited with use beyond 72 hours.
Neurologic emergencies
Rapid BP reduction is indicated in neurologic emergencies, such as hypertensive encephalopathy, acute ischemic stroke, acute intracerebral hemorrhage, and subarachnoid hemorrhage.
In hypertensive encephalopathy, the treatment guidelines are to reduce the MAP 25% over 8 hours.[9] Labetalol, nicardipine, esmolol are the preferred medications; however, nitroprusside and hydralazine should be avoided.
For acute ischemic stroke, the preferred medications are labetalol and nicardipine. Withhold antihypertensive medications unless the SBP is >220 mm Hg or the DBP is >120 mm Hg, UNLESS the patient is receiving IV or intra-arterial (IA) fibrinolysis; then, the goal BP is an SBP of < 185 mm Hg and DBP < 110 mm Hg. After treatment with fibrinolysis, the SBP should be maintained < 180 mm Hg and the DBP at < 105 mm Hg for 24 hours.[9]
For acute intracerebral hemorrhage, the preferred medications are labetalol, nicardipine, and esmolol; avoid nitroprusside and hydralazine. The treatment is based on clinical/radiographic evidence of increased intracranial pressure (ICP). If there are signs of increased ICP, maintain the MAP just below 130 mm Hg (or SBP < 180 mm Hg) for the first 24 hours after onset. In patients without increased ICP, maintain the MAP < 110 mm Hg (or SBP < 160 mm Hg) for the first 24 hours after symptom onset.[9]
Recent evidence shows that in cases of acute intracerebral hemorrhage, early intensive BP control is well tolerated and can reduce hematoma growth in patients treated within 6 hours after the onset of intracerebral hemorrhage.[10, 11] The target systolic pressure for these studies was 140 mm Hg and routine IV medications were used. The target SBP was maintained over 7 days.[10, 11]
In subarachnoid hemorrhage, nicardipine, labetalol, and esmolol are also the preferred agents; again, nitroprusside and hydralazine should be avoided. Maintain the SBP < 160 mm Hg until the aneurysm is treated or cerebral vasospasm occurs. Although oral nimodipine is used to prevent delayed ischemic neurologic deficits, it is NOT indicated for treating acute hypertension.[9]
Cardiovascular emergencies
Rapid BP reduction is also indicated in cardiovascular emergencies, such as aortic dissection, acute coronary syndrome, and acute heart failure.
In aortic dissection, the preferred medications are labetalol, nicardipine, nitroprusside (with beta-blocker), esmolol, and morphine sulfate. However, avoid beta-blockers if there is aortic valvular regurgitation or suspected cardiac tamponade. Maintain the SBP at < 110 mm Hg, unless signs of end-organ hypoperfusion are present. The preferred treatment includes a combination of narcotic analgesics (morphine sulfate), beta blockers (labetalol, esmolol), and vasodilators (nicardipine, nitroprusside). Calcium channel blockers (verapamil, diltiazem) are an alternative to beta blockers.[12]
For acute coronary syndrome, beta blockers and nitroglycerin are the preferred drugs. Treatment is indicated if the SBP is >160 mm Hg and/or the DBP is >100 mm Hg. Reduce the BP by 20-30% of baseline. Note that thrombolytics are contraindicated if the BP is >185/100 mm Hg.[13]
In acute heart failure, the preferred medications are IV or sublingual nitroglycerin and IV enalaprilat. Treat with vasodilators (in addition to diuretics) for a SBP ≥140 mm Hg.[13]
Cocaine toxicity/pheochromocytoma
Diazepam, phentolamine, and nitroglycerin/nitroprusside are the preferred drugs. However, avoid beta-adrenergic antagonists before administering phentolamine.
Hypertension and tachycardia from cocaine toxicity rarely require specific treatment. Alpha-adrenergic antagonists (phentolamine) are the preferred agents for cocaine-associated acute coronary syndromes.[14] Pheochromocytoma treatment guidelines are similar to that of cocaine toxicity. Only after alpha blockade can beta blockers be added for BP control.
Preeclampsia/eclampsia
The preferred medications are hydralazine, labetalol, and nifedipine. Avoid - Nitroprusside, angiotensin-converting enzyme inhibitors, esmolol. In women with eclampsia or preeclampsia, the SBP should be < 160 mm Hg and the DBP should be < 110 mm Hg in the antepartum and intrapartum periods. If the platelet count is less than 100,000 cells mm3, the BP should be maintained below 150/100 mm Hg. Patients with eclampsia or preeclampsia should also be treated with IV magnesium sulfate to avoid seizures.[15]
Perioperative hypertension
Nitroprusside, nitroglycerin, and esmolol are preferred. Target the perioperative BP to within 20% of the patient's baseline pressure, except if there is the potential for life-threatening arterial bleeding. Perioperative beta blockers are the first choice in patients undergoing vascular procedures or in patients with an intermediate or high risk of cardiac complications.[12]