Hypertension in the Emergency Department

Management of hypertensive crises

Hypertensive emergencies are life-threatening conditions because their course is complicated with acute target organ damage. They can present with neurological, renal, cardiovascular, microangiopathic hemolytic anemia, and obstetric complications. After diagnosis, they require the immediate reduction of blood pressure (in <1 hour) with intravenous drugs such as sodium nitroprusside, administered in an intensive care unit. These patients present with a mean arterial pressure >140 mm Hg and grade III to IV retinopathy. Only occasionally do they have hypertensive encephalopathy, reflecting cerebral hyperperfusion, loss of autoregulation, and disruption of the blood-brain barrier. In hypertensive emergencies, blood pressure should be reduced about 10% during the first hour and another 15% gradually over the next 2 to 3 hours to prevent cerebral hypoperfusion. The exception to this management strategy is aortic dissection, for which the target is systolic blood pressure <120 mm Hg after 20 minutes. Oral antihypertensive therapy can usually be instituted after 6 to 12 hours of parenteral therapy. Hypertensive urgencies are severe elevations of blood pressure without evidence of acute and progressive dysfunction of target organs. They demand adequate control of blood pressure within 24 hours to several days with use of orally administered agents. The purpose of this review is to provide a rational approach to hypertensive crisis management.

Emergency room management of hypertensive urgencies and emergencies

Hypertensive crisis affects upward of 500,000 Americans each year. Although the incidence of hypertensive crisis is low, affecting fewer than 1% of hypertensive adults, more than 50 million adult Americans suffer from hypertension. Presentation of a patient with severe hypertension to the emergency room demands immediate evaluation, prompt recognition of a hypertensive emergency or urgency, and the prompt institution of appropriate therapeutic measures to prevent progression of target-organ damage and to avoid a catastrophic event. Hypertensive emergencies are severe elevations in blood pressure that are complicated by evidence of progressive target-organ dysfunction such as coronary ischemia, disordered cerebral function, a cerebrovascular event, pulmonary edema, or renal failure. Although therapy with parenteral antihypertensive agents may be initiated in the emergency department, these patients warrant prompt admission to an intensive care unit where continuous monitoring of blood pressure can be assured during therapy.

Oral antihypertensives for hypertensive urgencies

OBJECTIVE

To review the data describing the use of oral antihypertensive agents in the treatment of hypertensive urgencies (HU).

DATA SOURCES

A MEDLINE search of the English-language literature and fan searches of papers evaluating oral antihypertensives in HUs and emergencies were conducted.

STUDY SELECTION

Controlled and uncontrolled studies in humans are reviewed. Emphasis was placed on recent trials evaluating individual agents and comparative trials.

DATA SYNTHESIS

Comparative trials have demonstrated that four currently available oral agents can lower blood pressure rapidly and predictably. Nifedipine, the most extensively studied, and clonidine have served traditionally as the oral agents of choice for the treatment of HUs. All the agents can lower blood pressure effectively within the first few hours after dosing, but their use also has been associated with adverse effects. Nifedipine and captopril are the two agents with the most rapid onset, within 0.5-1 hour, and may treat hypertensive emergencies as well as urgencies. Clonidine and labetalol have maximal blood pressure lowering effects at 2-4 hours.

CONCLUSIONS

Captopril, clonidine, labetalol, and nifedipine are all effective agents for the treatment of HUs. Agent selection should be based on the perceived need for urgent blood pressure control, the cause of HU, and concomitant conditions. A definite benefit from acute blood pressure lowering in HUs has yet to be demonstrated, especially in asymptomatic patients. More controlled trials with less aggressive dosing regimens and placebo controls need to be performed to assess the most appropriate treatment for HUs with the fewest adverse effects.

Evaluation of drug therapy for treatment of hypertensive urgencies in the emergency department

Oral nifedipine (N) and clonidine (C) are often used in the treatment of hypertensive urgencies; however, until recently, there were no comparative studies using the same patient population. The authors reviewed the records of hypertensive patients treated in the emergency department between October 1, 1987 and September 30, 1988. Selected patients had a diastolic blood pressure (DBP) of greater than 115 mm Hg without evidence of acute end organ damage. Patients were stratified into three treatment groups: N, C, and group 3 (G3). G3 received a variety of drug therapies but not exclusively N or C. Systolic blood pressure (SBP), DBP, mean arterial pressure (MAP), percent decrease in MAP (%MAP), time to lower blood pressure, admissions, and discharges were evaluated. Efficacy and safety were defined as reaching a DBP less than 110 mm Hg but %MAP of no greater than either 25% or 40%, respectively. Thirty-five N, 32 C, and 27 G3 patients were identified with no statistical difference between groups in race, gender, pretreatment SBP, DBP, or MAP. N, C, and G3 significantly reduced SBP, DBP, and MAP (P less than .01). Comparing N, C, and G3, no differences were observed in %MAP, admissions, discharges, efficacy, or safety. Time required to decrease blood pressure differed between all three groups (44 +/- 32 N v 77 +/- 57 C v 152 +/- 94 min G3) (p less than .05). These results indicate that N, C, and a variety of drug therapies are equally effective and safe in the treatment of hypertensive urgencies.

Blood pressure decrease prior to initiating pharmacological therapy in nonemergent hypertension

In order to characterize the decrease in blood pressure that occurs in the emergency department (ED) setting in cases of nonemergent hypertension before beginning pharmacological therapy, 94 consecutive cases of hypertension seen at the University of Illinois Hospital were reviewed. Each patient in the analysis had a triage blood pressure recorded by the nursing staff and second blood pressure reading taken between 10 minutes and 2 hours after the triage pressure before pharmacological therapy was begun. Patients with diastolic pressures less than 90 mm Hg were excluded, as were patients with acute end-organ pathology secondary to hypertension. In the remaining 54 cases, the mean arterial pressure fell by 6% (P less than .003), the systolic pressure fell by 6% (P less than .022), and the diastolic pressure fell by 6.4% (P less than .003), suggesting that in nonemergent hypertension, a significant decrease in blood pressure occurs in the ED before pharmacological therapy is begun. The blood pressure decrease was not statistically different when sex and age were considered, but when patients were grouped into those with diastolic pressures between 90 mm Hg and 114 mm Hg and those with diastolic pressures greater than or equal to 115 mm Hg, there was a statistically significant decrease in systolic, diastolic, and mean arterial pressures only in patients with diastolic pressures greater than or equal to 115 mm Hg. Our findings suggest that patients with nonemergent hypertension do not always require immediate and aggressive pharmacological intervention in the ED setting and are best observed for a short period and then reassessed before beginning pharmacological therapy.