What are the major principles of treating a patient with a hypertensive emergency?
Normal autoregulation of vascular beds allows a tissue to receive relatively constant perfusion across a wide range of blood pressures. In hypertensive emergencies, the autoregulatory capacity of many vascular beds is reset, so that the autoregulatory zone is optimized for the much higher blood pressure in the days to weeks before the medical encounter. This allowed the vessels, over time, to constrict and continue to deliver an appropriate (if not quite normal) flow of blood and oxygen, despite the very high blood pressures. A primary treatment goal is to gradually reduce the blood pressure over a short but sufficient amount of time to allow vascular beds to adjust to the “new, lower” pressure without causing ischemia. A corollary is that lowering blood pressure into the “normal” range should be avoided, because prior to the patient’s presentation, the threshold for ischemia has also been shifted to the right.
Most authorities recommend admission to an intensive care unit, although a method to monitor blood pressure (intraarterial line versus automated oscillometric device), an intravenous line to deliver the antihypertensive agent, and an attentive physician can begin treatment in the emergency department.
No trials have been done to establish a blood pressure target, but most authorities recommend a decrease in mean arterial pressure by about 10% in the first hour and no more than 25% during the first 2 hours. Most patients tolerate a blood pressure of about 160 to 180/100 mm Hg well after the first 2 hours or so, but the antihypertensive medication dose should be individualized and should be reduced if deterioration occurs when the blood pressure is decreased “too fast” or “too far.” After the blood pressure has been stabilized (usually for 6 to 24 hours) and after oral treatment is administered, intravenous antihypertensive therapy can be withdrawn.
