Lower Blood Pressure Slowly in Hypertensive Emergency



SAN FRANCISCO – Rapidly lowering blood pressure in patients who are having a hypertensive emergency or hypertensive urgency isn’t necessary and may be harmful, except in the case of aortic dissection.

Lower blood pressure gradually in the emergency department to maintain cerebral perfusion within acceptable limits, Dr. Michael J. Bresler advised at the annual meeting of the American College of Emergency Physicians. For most patients, don’t push diastolic blood pressure down below 110 mm Hg, he added.

Dr. Michael J. Bresler

Hypertensive emergencies should be treated with IV medications, said Dr. Bresler of Stanford (Calif.) University. It’s not an emergency unless acute high blood pressure is causing end-organ damage, usually to the brain, heart, or kidneys. Blood pressure usually measures above 220 mm Hg systolic or 130 mm Hg diastolic in hypertensive emergencies.

Hypertensive urgency consists of blood pressure greater than 220 mm Hg systolic or 120 mm Hg diastolic but without acute organ failure or acute symptoms directly attributable to the blood pressure elevation. Physicians may opt to treat hypertensive urgency with oral medications in the ED, but usually the patient gets a prescription for outpatient therapy, he said.

Patients with elevated blood pressure greater than 140 mm Hg systolic or 90 mm Hg diastolic do not have urgent or emergent hypertension, but should be referred for further evaluation. Physicians may choose to write a prescription for outpatient antihypertensive therapy, but treatment in the ED is not warranted, Dr. Bresler said.

"It’s not the numbers that count" in assessing hypertension in the ED, he said. "It’s whether the patient has an acute problem from the blood pressure."

When choosing antihypertensive therapy, some medications are more suitable for the ED than are others.

The most commonly used antihypertensive in emergency medicine is nitroprusside, a parenteral vasodilator that’s very effective and has a very short half-life. The drug has disadvantages, however. It’s unstable in UV light, and so must be wrapped, and it metabolizes to cyanide/thiocyanate. Nitroprusside can cause orthostatic hypotension, is toxic at higher doses and potentially toxic to fetuses, increases intracranial pressure, and can cause tissue necrosis if there’s extravasation.

Nitroglycerin, another parenteral vasodilator, is good for patients with heart failure and angina, but it’s not a good drug for hypertensive crisis, Dr. Bresler said.

Among calcium channel blockers, the most useful for blood pressure control in the emergency department are IV nicardipine or IV clevidipine. These drugs are as effective as nitroprusside without the cyanide/thiocyanate toxicity. They are not light sensitive and so don’t need a foil wrap. Rate adjustments are required about a third as often as with nitroprusside. The IV calcium channel blockers don’t need an arterial line and don’t cause intracerebral vasodilation, which can lead to edema.

"Many of us are switching to nicardipine instead of nitroprusside," Dr. Bresler said.

Among beta-blockers, his top picks for emergency medicine are IV labetalol (which also is an alpha-blocker), oral or IV metoprolol, or IV esmolol, a short-acting cardioselective agent. In patients with coronary artery disease or with anxiety, beta-blockers are a good choice, he said. For oral therapy, the long-acting preparations are best.

ACE inhibitors are especially helpful for hypertension in patients with diabetes, renal failure, or heart failure. The most useful for emergency departments is IV enalapril, he said. But 1 in 2,000 patients who are treated with an ACE inhibitor will develop angioedema, and 1 in 10 will develop cough.

Angiotension II receptor blockers (ARBs) such as losartan, valsartan, or irbesartan are as effective as ACE inhibitors and have fewer side effects. Angioedema is rare, and the drugs do not cause cough. "I think as these become generic, they will replace ACE inhibitors," Dr. Bresler said.

Like ARBs, direct renin inhibitors such as aliskiren are similar in efficacy to ACE inhibitors with fewer side effects.

Hypertensive urgency also could be treated with oral clonidine, an alpha2 adrenergic agonist.

Diuretics have no role in treating high blood pressure in the ED, but are a mainstay of outpatient therapy, he said. Diuretics are inexpensive and are at least as effective as ACE inhibitors or calcium channel blockers, but most hypertensive patients will require other medications in addition to diuretics.

Dr. Bresler said he has no relevant conflicts of interest.

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