Parenteral Agents Used for Hypertensive Emergencies

Hypertensive emergency is an acute elevation of blood pressure (>180/120 mm Hg) associated with end-organ damage, specifically, acute effects on the brain, heart, aorta, kidneys, and/or eyes¹ (Table 61-2; Figure 61-1). Epidemiologic studies of this condition are hampered by the fact that no diagnostic code exists to differentiate hypertensive emergency from less serious clinical presentations associated with hypertension, despite the need for such a code.²

Hypertensive urgency is a clinical presentation associated with severe elevations in blood pressure without progressive target organ dysfunction.¹ Although hypertensive emergencies can be defined by the presence of end-organ dysfunction, hypertensive urgencies are not, and therefore the arbitrary numerical criterion of >180/120 mm Hg is often cited as an indication for treatment, when in fact the clinical benefit of such treatment has never been established.³ This chapter addresses the indications for acute intervention for blood pressure reduction for ED patients.

Aortic Dissection

The therapeutic goal in acute aortic dissection is a systolic blood pressure ranging from <140 to <110 mm Hg.^36–39 There are few studies that guide the treatment of hypertensive emergencies in this condition.⁴⁰ The treatment of pain with morphine is an important part of the management

Acute Sympathetic Crisis

The preferred initial treatment of an acute sympathetic crisis due to cocaine or amphetamine abuse is the administration of an IV benzodiazepine, such as lorazepam or diazepam, with repeated IV doses as needed

Eclampsia and Preeclampsia

In the treatment of eclampsia, labetalol has been tested in several trials and is the preferred agent.^55–61 Nifedipine, an agent whose use is discouraged in other settings, has performed favorably in the setting of preeclampsia without significant side effects.^55,56 Hydralazine formerly was considered the drug of choice, but is no longer recommended due to its unpredictable therapeutic profile.^59,62 Angiotensin-converting enzyme inhibitors are contraindicated in pregnancy due to their effects on the fetus

Neurologic Emergencies

Blood pressure reduction in the setting of neurologic emergencies typically requires emergency CT scanning to determine diagnosis, treatment thresholds, and priorities. Hypertensive encephalopathy is the clearest indication for blood pressure reduction, but vascular disorders, including ischemic stroke, must be ruled out first, and astute clinical judgment is required to differentiate between these two clinical diagnoses (see the earlier section Clinical Features). Blood pressure reduction is controversial in the setting of acute vascular lesions, subarachnoid hemorrhage, intracranial hemorrhage, and ischemic stroke. Untreated vascular spasm in the setting of subarachnoid hemorrhage is associated with deterioration and has been successfully treated with oral nimodipine, a calcium channel blocker that is not given to reduce blood pressure, but may affect pressures. When the decision to lower blood pressure is made for patients with subarachnoid hemorrhage, the purpose is to prevent rebleeding, which has been associated with blood pressures >160/100 mm Hg