Heads down: flat positioning improves blood flow velocity in acute ischemic stroke

Abstract

Background: Acute stroke patients are routinely positioned with the head of the bed (HOB) elevated at 30 degrees despite lack of evidence for increased intracranial pressure.

Objectives: To determine the effect of HOB positions in real time on residual blood flow velocity in acutely occluded arteries causing stroke and whether resistance to residual flow increased with lower HOB positions.

Methods: In a repeated-measures quasi-experiment, the effect of 30, 15, and 0 degrees HOB on middle cerebral artery (MCA) mean flow velocity (MFV) in patients with acute (<24 hours) ischemic stroke was measured with transcranial Doppler using MFV and pulsatility index (PI) of the residual flow signals at the site of persisting acute occlusion.

Results: Twenty patients were evaluated (mean age 60 +/- 15 years; median NIH Stroke Scale [NIHSS] score 14 points). MCA MFV increased in all patients with lowering head position (maximum absolute MFV value increase 27 cm/s, range 5 to 96% from baseline values at 30 degrees). On average, MCA MFV increased 20% (12% from 30 to 15 degrees and 8% from 15 to 0 degrees; p < or = 0.025). Mean arterial pressure and heart rate were unchanged throughout the intervention. PI remained unchanged (mean values 0.89 at 30 degrees elevation, 0.91 at 15 degrees elevation, and 0.83 at 0 degrees elevation) at each HOB position, indicating no increase in resistance to blood flow. Immediate neurologic improvement (average 3 NIHSS motor points) occurred in three patients (15%) after lowering head position.

Conclusion: Acute ischemic stroke patients may benefit from lower head-of-the-bed positions to promote residual blood flow to ischemic brain tissue.