Rapidly lowering blood pressure in the ischemic stroke patient can lead to decreased perfusion of the already stressed brain cells. An approach of “permissive hypertension,” based on the need to maintain perfusion to brain cells, may be followed dependent on the patient's symptoms. Nurses involved in stroke care need to be aware that cerebral perfusion pressure (the difference between mean arterial pressure and intracranial pressure) should be maintained at a level above 40 mm Hg to obtain adequate blood flow to brain tissue. Systolic, diastolic, and mean arterial blood pressure (MAP) will be higher than usual, as MAP below 100 mm Hg have been shown to correlate with poorer outcomes.[23] The exception is in patients who receive rt-PA: blood pressure will need to be lowered to prevent complications from the medication during reperfusion. Lower blood pressure is also the goal in patients with hemorrhagic stroke, as higher pressures lead to more bleeding and cellular irritation.
One of the controversies related to improved circulation of the brain is the “head up versus head down” controversy. Currently, there is no standard answer as to whether the head of the bed should be elevated or flat, but most agree that the head should be in a neutral position to facilitate blood flow in and out of the cranium. The degree of elevation seems to be specific to and dependent on the patient.
Classically, in patients with impairment of cerebral circulation due to a clot, reperfusion is attempted using fibrinolytic therapy (eg, rt-PA). Nurses should know the inclusion criteria to identify patients for such therapy (Table), as rapid evaluation for appropriateness and initiation of administration of fibrinolytic therapy is critical in preventing cell death.[24] It is important to remember that there is only a 3-hour window from onset of symptoms in which intravenous rt-PA can be given, after which the risk of bleeding increases.