Hypertension Blog

Treatment usually begins in the emergency department and continues in the intensive care unit (ICU).The vasodilator of choice for emergency hypertension is sodium nitroprusside administered at 0.3 to 10 µg/kg/minute . By working directly on the vessels, this drug immediately lowers the patient’s blood pressure. After his blood pressure has been stabilized and he has begun taking an oral antihypertensive drug, sodium nitroprusside can be discontinued.

Several other antihypertensive drugs also are commonly used to treat emergency hypertension. Drugs with a short duration of action are preferred because hypotensive effects can be reversed quickly by reducing the dose or stopping the drug.

A physician prescribes the drug regimen based in part on the complications the patient has. Depending on the complication, a physician may need to prescribe a vasodilator other than nitroprusside (nitroglycerin, diazoxide, or hydralazine), an adrenergic blocker (phentolamine mesylate or labetalol), an ACE inhibitor (enalapril), a ganglionic blocker (trimethaphan), or a calcium channel blocker (nicardipine).

Nitroglycerin

Nitroglycerin dilates veins and arterioles. It also decreases preload and afterload. To treat emergency hypertension, you’ll administer nitroglycerin at a rate of 5 to 10 µg/ minute and increase the rate by 5 µg/minute every 3 to 5 minutes, as ordered. If the patient’s blood pressure doesn’t decrease by the time he’s receiving 20 µg/minute, increase the rate by 10 to 20 µg/minute, as prescribed, until the desired blood pressure is reached. Typically, nitroglycerin begins working in 5 minutes.

A patient receiving nitroglycerin may experience orthostatic hypotension, tachycardia, flushing, and headache. Also, he may develop a tolerance to the drug over time.

Diazoxide

Diazoxide dilates arteriolar smooth muscle. It’s administered to treat emergency hypertension in doses of 50 to 150 mg every 5 minutes as an I.V. bolus or 7.5 to 30 mg/minute as an I.V. infusion. Diazoxide begins working 1 to 5 minutes after administration.

A patient receiving diazoxide may experience nausea, vomiting, abdominal discomfort, hyperglycemia, tachycardia, hypotension, sodium retention, fluid retention, and angina. Diazoxide may exacerbate an MI, heart failure, and an aortic dissection. It also may trigger cerebral ischemia.

When administering diazoxide, don’t mix it with other drugs. Protect the drug from light. And inject it rapidly, in less than 30 seconds, to overcome protein binding.

During and after administration, monitor your patient’s blood glucose level. Also, monitor him for sodium and fluid retention. If he’s retaining sodium and fluid, he may need a diuretic.

Hydralazine

Typically, a physician prescribes hydralazine, which dilates arteriolar smooth muscle, for patients with renal insufficiency because it doesn’t compromise renal function. For emergency hypertension, the drug usually is administered as an I.V. bolus of 5 to 20 mg. It begins to work in 5 to 20 minutes.

A patient receiving hydralazine may experience tachycardia, palpitations, headache, fluid retention, nasal congestion, gastrointestinal (GO symptoms, angina, and an Ml. If the patient shows signs and symptoms of lupus-like syndrome, discontinue the drug.

Phentolamine Mesylate

A physician may prescribe phentolamine mesylate, an alpha-blocker, for emergency hypertension resulting from elevated catecholamine levels, clonidine withdrawal, and interactions between monoamine oxidase inhibitors and tyramine.

Phentolamine mesylate is administered as an I.V. bolus dose of 2.5 mg. You can also give a subsequent I.V. bolus of 5 mg, as ordered. Usually, the drug begins working within seconds.

A patient receiving phentolamine mesylate may experience tachycardia, dry mouth, flushing, nausea, vomiting, MI, arrhythmias, angina, and hypotension.

Labetalol

Labetalol, an alpha-blocker and beta-blocker, is prescribed for emergency hypertension resulting from elevated catecholamine levels and antihypertensive drug withdrawal. It’s prescribed for patients with emergency hypertension who have had an MI and for those with an aortic dissection. It also is prescribed for emergency hypertension in patients with renal failure because the drug doesn’t compromise renal perfusion.

For emergency hypertension, labetalol is administered as an I.V. infusion at a rate of 0.5 to 2 mg/minute or as an I.V. bolus in doses of 20 to 80 mg every 10 minutes. The maximum cumulative dose for the drug is 300 mg. Usually, it begins to work in 5 minutes.

A patient receiving labetalol may experience orthostatic hypotension, bronchospasm, nausea, vomiting, heart failure, and arrhythmias. When administering the drug, monitor the patient for heart failure and heart block.

Enalapril

Enalapril, which suppresses the renin-angiotensin­aldosterone system, is prescribed for emergency hypertension in I.V. doses of 0.625 to 1.25 mg over 5 minutes. You also can give it in subsequent 1.25 mg doses every 6 hours, as ordered. Usually, the drug begins to work in 5 to 15 minutes.

A patient receiving enalapril may experience proteinuria, renal failure, loss of taste, hyperkalemia, tachycardia, neutropenia, and agranu­locytosis. If the patient has hypovolemia or is taking a diuretic when enalapril is administered, he also may experience excessive hypotension.

Trimethaphan

Trimethaphan blocks transmission in the autonomic ganglia, exerting a direct peripheral vasodilator effect. A physician prescribes it for patients who have emergency hypertension and acute aortic dissection because it reduces blood pressure and reduces the sharpness of the pulse wave produced by ventricular contractions.

Trimethaphan is administered I.V. in 500 mg doses diluted in 500 ml of dextrose 5% in water or 0.9% normal saline solution and infused at a rate of 0.5 to 5 mg/minute. Then, it’s titrated until the desired blood pressure is reached. Usually, the drug begins to work in 1 to 2 minutes.

A patient receiving trimethaphan may experience intestinal and bladder paresis, blurred vision, dry mouth, respiratory arrest, orthostatic hypotension, paralytic ileus, and urticaria.

Nicardipine

Nicardipine, a calcium channel blocker, dilates the arterioles. It’s prescribed for emergency hypertension in patients with renal failure because it doesn’t compromise renal perfusion.

Nicardipine is administered by I.V. infusion at a rate of 5 to 15 mg/hour. Usually, it begins to work in 1 to 15 minutes.

A patient receiving nicardipine may experience tachycardia, nausea, vomiting, flushing, and headache. The drug is contraindicated in a patient who has aortic stenosis.

Tags:Acute Complication, Hydralazine, hypertension treatment, hypertesion, Labetalol, Nitroglycerin Trimethaphan