Effect of head elevation on intracranial blood flow velocity following acute ischemic stroke
Current nursing practice for the care of patients with acute ischemic stroke advocates routine elevation of the head of the bed (HOB) to 30 degrees. Evidence supporting this practice is lacking, reflecting an inappropriate generalization of findings from studies conducted primarily on traumatic brain injury patients with associated increased intracranial pressure (ICP) to the ischemic stroke population. A repeated measures quasi-experimental design was used to study the effect of 30, 15, and 0 degree HOB elevation on middle cerebral artery (MCA) mean flow velocity (MFV) in a convenience sample of 20 patients presenting with acute ischemic stroke. Transcranial Doppler (TCD) sonography mounted by head frame was used to measure MCA MFV. Patients were on average 59.5 years of age (SD = 15.4), with a mean National Institutes of Health Stroke Scale score of 11.95 (SD = 6.46) indicating moderate to severe stroke. On average, a 12% increase in MCA MFV was measured when the HOB was lowered to 15 degrees from the 30 degree elevation standard (p < .001); MCA MFV increased on average by an additional 8% when the HOB was again lowered from the 15 degree position to the 0 degree (flat) position (p = NS). The overall increase in MCA MFV achieved from lowering the HOB position from 30 degrees to a 0 degree position was 20% (p < .001). Mean arterial pressure; heart rate; and pulse pressure remained stable without significant change throughout the positioning intervention and measurement period. Pulsatility index remained within normal limits in all HOB positions tested indicating that an increase in resistance to blood flow due to increased ICP did not occur with 0 degree positioning. These findings suggest that patients with acute ischemic stroke may benefit from lower HOB positions, in particular flat positioning, to promote an increase in blood flow to ischemic brain tissue that may ultimately reduce brain infarct volume.