Hypertensive emergencies, characterized by extreme elevations of blood pressure and acute end organ damage specific to the heart, central nervous system, or kidneys, account for 3 to 5 percent of all admissions to medical intensive care units. The standard treatment for the hypertensive emergency has traditionally been to administer intravenous vasodilator therapy in a closely supervised setting. Therapy with nitroprusside, the most commonly used initial agent for blood pressure reduction, usually entails admission to an intensive care unit with an indwelling arterial catheter placed for continuous blood pressure monitoring. A number of current reports describe the treatment of hypertensive emergencies with nifedipine, an oral calcium channel blocking agent. Theoretically, oral nifedipine carries several advantages over intravenous nitroprusside—ease of administration, less complex and expensive monitoring, and no treatment delay while a patient is being transferred to an ICU. To date, no randomized trial has been performed comparing nitroprusside and nifedipine in patients with severe hypertension.
Patients and Methods
Patients admitted to the Medical Intensive Care Unit from the Emergency Room with diastolic blood pressure levels greater than 130 mm Hg in association with eye ground changes were considered eligible for the study. Patients excluded from the study were those with suspected myocardial infarction or dissecting aneurysm, coma or focal neurologic findings, pregnant women, and anyone who had received antihypertensive therapy in the Emergency Room. Eligible patients were randomized tQ receive either intravenous nitroprusside or oral nifedipine according to their hospital admission numbers. Patients with odd numbers were assigned to the nitroprusside group and those with even numbers were assigned to the nifedipine group Over a 15-month period, ten patients received nifedipine and five patients received nitroprusside according to this randomization plan.
Nifedipine was administered as a 10 mg oral dose (swallowed whole) on admission to the ICU. This dose was repeated within two hours if the diastolic blood pressure had not dropped below 120 mm Hg. The 10 mg of oral nifedipine was then repeated at six-hour intervals until the diastolic blood pressure was under 120 mm Hg. The maximum dose of nifedipine that could be administered in a 24-hour period was 60 mg. If the patient did not respond within 24 hours, it was considered a treatment failure.
According to a standard protocol, nitroprusside was administered by intravenous route via a flow control device beginning at a rate of 0.5 μg/kg/minute. The blood pressure response was monitored and the dose was adjusted by .25 μg/kg/minute every 15 minutes. When the patients diastolic blood pressure was under 120 mm Hg for two hours without further dose adjustments, oral vasodilator therapy was administered. All patients who were treated were monitored with an arterial cannula placed in the radial artery.
Data collected on every patient included response time for diastolic blood pressure to fall below 120 mm Hg, length of stay in ICU, morbidity, mortality and costs of therapy. Both groups of patients were compared with a group of historic control subjects who were treated with nitroprusside according to the same protocol. All patients were followed until hospital discharge.
Statistical analyses were performed as described by Zar. The Mann-Whitney test was used for comparison between the nifedipine and nitroprusside patient groups under the assumption that the data were not normally distributed.