Nicardipine, Nifedipine, and Isradipine are calcium channel blockers that work to decrease systemic vascular resistance and subsequently lower blood pressure. Hydralazine and Sodium nitroprusside are systemic vasodilators, thereby reducing afterload, however can be found to have reflex tachycardia, making them likely second or third line choices. Sodium nitroprusside was previously the first-line choice due to its rapid onset, although now it is less commonly used due to side effects, drastic drops in blood pressure, and cyanide toxicity. Sodium nitroprusside is also contraindicated in patients with myocardial infarction, due to coronary steal. It is again important that the blood pressure is lowered slowly. The initial goal in hypertensive emergencies is to reduce the pressure by no more than 25% the mean arterial pressure. Excessive reduction in blood pressure can precipitate coronary, cerebral, or kidney ischemia and, possibly, infarction.A hypertensive emergency is not based solely on an absolute level of blood pressure, but also on a patients baseline blood pressure before the hypertensive crisis occurs. Individuals with a history of chronic hypertension may not tolerate a "normal" blood pressure, and can therefore present symptomatically with hypotension, including fatigue, light-headedness, nausea, vomiting, or syncope. Prognosis
Severe hypertension is a serious and potentially life-threatening medical condition. It is estimated that people who do not receive appropriate treatment only live an average of about three years after the event.The morbidity and mortality of hypertensive emergencies depend on the extent of end-organ dysfunction at the time of presentation and the degree to which blood pressure is controlled afterward.
Treatment
In a hypertensive emergency, treatment should first be to stabilize the patients airway, breathing, and circulation per ACLS guidelines. Patients should have their blood pressure slowly lowered over a period of minutes to hours with an antihypertensive agent. Documented goals for blood pressure include a reduction in the mean arterial pressure by less than or equal to 25% within the first 8 hours of emergency. If blood pressure is lowered aggressively, patients are at increased risk of complications including stroke, blindness, or kidney failure. Several classes of anti hypertensive agents are recommended, with the choice depending on the cause of the hypertensive crisis, the severity of the elevation in blood pressure, and the patients baseline blood pressure prior to a hypertensive emergency. Physicians will attempt to identify a cause of the patients hypertension, including chest radiograph, serum laboratory studies evaluating kidney function, urinalysis, as that will alter the treatment approach for a more patient-directed regimen.Hypertensive emergencies differ from hypertensive urgency in that they are treated parenterally, whereas in urgency it is recommended to use oral anti hypertensives to reduce the risk of hypotensive complications or ischemia. Parenteral agents are classified into beta-blockers, calcium channel blockers, systemic vasodilators, or other (fenoldopam, phentolamine, clonidine). Medications include labetalol, nicardipine, hydralazine, sodium nitroprusside, esmolol, nifedipine, minoxidil, isradipine, clonidine, and chlorpromazine. These medications work through a variety of mechanisms. Labetalol is a beta-blocker with mild alpha antagonism, decreasing the ability of catecholamine activity to increase systemic vascular resistance, while also decreasing heart rate and myocardial oxygen demand.