CME Heads down Flat positioning improves blood flow velocity in acute ischemic stroke Anne W. Wojner-Alexander, PhD; Zsolt Garami, MD; Oleg Y. Chernyshev, MD, PhD; and Andrei V. Alexandrov, MD Abstract—Background: Acute stroke patients are routinely positioned with the head of the bed (HOB) elevated at 30° 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° 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°). On average, MCA MFV increased 20% (12% from 30 to 15° and 8% from 15 to 0°; p  0.025). Mean arterial pressure and heart rate were unchanged throughout the intervention. PI remained unchanged (mean values 0.89 at 30° elevation, 0.91 at 15° elevation, and 0.83 at 0° 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. NEUROLOGY 2005;64:1354 –1357 Ischemic stroke is a potentially reversible process that is dependent on restoration of arterial blood flow within a window of cellular viability that varies according to the severity and duration of the flow deficit. Measures that promote blood flow during the acute phase of ischemic stroke may directly impact the subsequent development of brain infarction and associated clinical deficit. One such measure may be flat head-of-the-bed (HOB) positioning to promote a gravity-induced increase in arterial flow to ischemic brain tissue; however, patients with stroke and other neurologic diagnoses are routinely positioned using 30° HOB elevation by paramedics and emergency room personnel. Several studies aimed to identify optimal HOB position for patients with neurologic disorders, often including heterogeneous samples of patients with differing diagnoses and potential or actual increases in intracranial pressure (ICP). 1-11 Most HOB posi- tioning studies included patients with traumatic brain injury. The studies focused on cerebral perfu- sion pressure (CPP) variables rather than real-time arterial flow variables. To date, findings from these studies have been inconclusive, with some favoring HOB elevation, 1,3,7,9,10 flat positioning, 4,11 and posi- tioning guided by individual patient factors. 2,5,6,8 There is only one HOB study consisting entirely of patients with large subacute ischemic strokes and normal ICP. 12 Whereas ICP and CPP were the pri- mary variables of interest, these researchers also ob- tained middle cerebral artery (MCA) mean flow velocity (MFV) data using transcranial Doppler (TCD) in 18 anesthetized patients. This study sug- gested that although ICP was higher in a flat posi- tion, CPP and MCA MFV were highest when patients were placed in the 0° HOB position. We sought to determine if MCA flow velocity could be augmented by simple HOB positioning during the acute phase of stroke while avoiding arterial flow compromise secondary to increased resistance to flow. We have previously shown the ability to mea- sure residual flow signals at the point of acute intra- cranial arterial occlusions using TCD. 13 TCD may be used to grade the severity of arterial occlusion and to indirectly estimate flow changes if insonation angle is maintained constant over short observation peri- ods. 14 In ischemic stroke, increased ICP with reduc- tion of CPP has been reported to peak at or beyond 48 hours post infarction. 15-17 Therefore, we did not anticipate significant aggravation of ICP with lower HOB positioning during the first 24 hours following symptom onset. Methods. A quasi-experimental repeated-measures design was used to study the effect of 30, 15, and 0° HOB elevation on resid- ual arterial flow signals in patients with acute ischemic stroke. Two hypotheses guided this study: 1) MCA MFV would signifi- From the University of Texas Health Science Center at Houston. Received September 8, 2004. Accepted in final form January 5, 2005. Address correspondence and reprint requests to Dr. A.W. Wojner-Alexander, Stroke Team, Department of Neurology, University of Texas Health Science Center at Houston, 6431 Fannin, MSB 7.044, Houston, TX 77030; e-mail: Anne.W.Wojner@uth.tmc.edu 1354 Copyright © 2005 by AAN Enterprises, Inc. Published Ahead of Print on April 7, 2005 as 10.1212/01.WNL.0000158284.41705.A5