Effect of body position on cerebral oxygenation and physiologic parameters in patients with acute neurological conditions

Abstract

How body position influences brain tissue oxygen (PbtO2) and intracranial pressure (ICP) in critically ill neurosurgical patients remains poorly defined. In a prospective observational repeated measures study, we examined the effects of 12 different body positions on neurodynamic and hemodynamic outcomes. Thirty-three consecutive patients (mean +/- SD, age = 48.3 +/- 16.6 years; 22 men), admitted after traumatic brain injury, subarachnoid hemorrhage, or craniotomy for tumor, were evaluated in a neurocritical care unit at a level 1 academic trauma center. Patients were eligible if the admission score in the Glasgow Coma Scale was < or =8 and they had a Licox CMP Monitoring System (Integra Neurosciences, Plainsboro, NJ). Patients were exposed to all 12 positions in random order. Changes from baseline to the 15-minute postposition assessment mean change scores showed a downward trend for PbtO2 for all positions with statistically significant decreases observed for supine head of bed (HOB) elevated 30 degrees and 45 degrees (p < .01) and right and left lateral positioning HOB 30 degrees (p < .05). ICP decreased with supine HOB 45 degrees (p < .01) and knee elevation, HOB 30 degrees and 45 degrees (p < .05), and increased (p < .05) with right and left lateral HOB 15 degrees. Hemodynamic parameters were similar in the various positions. Positioning practices can positively or negatively affect PbtO2 and ICP and fluctuate with considerable variability among patients. Nurses must consider potential effects of turning, evaluate changes with positioning on the basis of monitoring feedback from multimodality devices, and make independent clinical judgments about optimal positions to maintain or improve cerebral oxygenation.