Effects of body position on intracranial pressure and cerebral perfusion in patients with large hemispheric stroke

Abstract

Background and purpose: The purpose of this study was to prospectively evaluate the effects of body position in patients with large supratentorial stroke.

Methods: We performed 43 monitoring sessions in 18 patients with acute complete or subtotal middle cerebral artery (MCA) territory stroke. Intracranial pressure (ICP) was monitored with a parenchymal probe. Mean arterial blood pressure, ICP, and MCA peak mean flow velocity (VmMCA) were continuously recorded. Patients with acute ICP crises were excluded. After baseline values at a 0 degree supine position were attained, the backrest was elevated in 2 steps of 5 minutes each to 15 degrees and 30 degrees and then returned to 0 degree.

Results: Baseline mean arterial pressure was 90.0+/-1.6 mm Hg and fell to 82.7+/-1.7 mm Hg at 15 degrees and 76.1+/-1.6 mm Hg at 30 degrees backrest elevation (P<0.0001). ICP decreased from 13.0+/-0.9 to 12.0+/-0.9 mm Hg at 15 degrees and 11.4+/-0.9 mm Hg at 30 degrees backrest elevation (P<0.0001). As a result, cerebral perfusion pressure decreased from a baseline value of 77.0+/-1.8 to 70.0+/-1.8 mm Hg at 15 degrees and 64.7+/-1.7 mm Hg at 30 degrees backrest elevation (P<0.0001). VmMCA was already higher on the affected side during baseline measurements. VmMCA decreased from 72.8+/-11.3 cm/s at 0 degree to 67.2+/-9.7 cm/s at 15 degrees and 61.2+/-8.9 cm/s at 30 degrees on the affected and from 49.9+/-3.7 cm/s at 0 degree to 47.7+/-3.6 cm/s at 15 degrees and 46.2+/-2.2 cm/s at 30 degrees on the contralateral side (P<0.0001).

Conclusions: In patients with large hemispheric stroke without an acute ICP crisis, cerebral perfusion pressure was maximal in the horizontal position although ICP was usually at its highest point. If adequate cerebral perfusion pressure is considered more desirable than the absolute level of ICP, the horizontal position is optimal for these patients.