Blood Pressure

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Hypertensive Emergencies

 

Chronic uncontrolled or poorly controlled hypertension predisposes to a cerebrovascular event, such as hemorrhage, transient ischemic attack (TIA), thrombosis and hypertensive encephalopathy, as well as aortic dissection, cardiac disease (angina, myocardial infarction, congestive heart failure) and renal failure.

Hypertensive Encephalopathy

Hypertensive encephalopathy is seen when the blood pressure exceeds the limits of autoregulation by the blood-brain barrier. Blood enters brain tissue causing cerebral edema. The process develops over hours to days, with symptoms of headache, nausea, vomiting and an altered mental status ranging from confusion to lethargy. Visual changes, seizures and focal neurological changes may occur. The physical exam often reveals papilledema and/or retinal hemorrhages. Pressures may exceed 250/130 mmHg.
Treatment: nitroprusside (Nipride) 0.5 ug/kg/min IV is a fast acting arterial and venous dilator. Labetalol (Normodyne) in 20mg IV increments may also be used.

Aortic Dissection

Aortic dissection is a tear of the thoracic aorta at the arch. Blood dissects through the tunica intima into the tunica media. The typical patient is an older hypertensive male with sudden onset of severe chest pain of a “tearing”quality, radiating to the back. A proximal dissection affecting the aortic valve and heart results in the diastolic murmur of aortic insufficiency, and possible pericardial effusion and tamponade. Involvement of the carotid arteries may result in signs of stroke. Paraplegia may be present if the vertebral and spinal arteries are involved. Pulse differences are aften present in the extremities. Tachycardia and signs of inadequate organ perfusion such as clammy skin and delayed capillary refill may be present. A chest x-ray often shows a widened mediastinum.
Treatment: a thoracic surgeon should be immediately notified. A beta-blocker such as labetalol (Normodyne) 20 mg IV is administered, followed by nitroprusside (Nipride), beginning at 0.5 µg/kg/min, to maintain the systolic pressure at about 120 mmHg.

Hypertension and Cerebrovascular Accident
In hypertension accompanying a cerebrovascular accident, it is sometimes difficult to determine whether hypertension is the cause or the result of the problem. Increased blood pressure is frequently a response to stroke, although the patient with a thrombotic or embolic stroke usually has only a small elevation. As with an ischemic stroke, hypertension may contribute to an intracerebral hemorrhage, or be the result of it. Subarachnoid hemorrhage is seen in a younger population and is the result of a ruptured cerebral aneurysm or a bleeding arteriovenous malformation.
Treatment: blood pressure management is seldom required for an ischemic stroke. If the diastolic rises over 130 mmHg, increments of labetolol (Normodyne) 10 mg IV every 20 minutes may be given to reduce the diastolic to slightly above prestroke levels for both hemorrhagic and ischemic strokes.

Hypertension and Cardiac Emergency

As with an acute cerebrovascular accident, it is often difficult to determine whether the hypertension caused the angina, myocardial infarction or pulmonary edema, or was the result of an alteration in left ventricular performance secondary to increased afterload that raised the blood pressure.
Treatment: nitroglycerine, a dilator of coronary arteries, is begun at 10 µg/ min IV. Further control may be needed by nitroprusside 0.5 µg/kg/min..