A0040 Evaluation of Cerebral Perfusion Pressure and Cerebral Blood Flow Velocities in Different Head Positions Using Transcranial Doppler in Neurosurgical Patients

Background: Different head positions in neurosurgical patients in the postoperative unit may affect cerebral perfusion pressure. The primary aim of this study was to investigate the effects of various head positions on the cerebral blood flow velocities by transcranial Doppler (TCD) in these patients. Materials and Methods: This study with observational, prospective repeated measures was designed to measure bilateral MCA (middle cerebral artery) flow velocities, pulsatility index using TCD at different head positions in 20 patients who underwent cranial surgery admitted in the NSICU within 24 hours of surgery. The data collection was done in supine position with 0°, 30°–45° and 60°–70° head elevations. Postural changes in hemodynamic variables (HR, MAP) were recorded. Estimated cerebral perfusion pressure (eCPP) was calculated as MAP × FVd/FVm +14. Near-infrared spectroscopy, invasive blood pressure data at two different transducer locations, and changes in neurological status as the secondary outcomes were simultaneously recorded. Results: Out of 20 patients who underwent craniotomy for intracranial lesion, 14 patients (mean age 41 ± 14 years) were evaluated. Six patients were excluded due to poor cooperation and inadequate temporal window. On average, MCA mean flow velocity (mFV) on the right and left hemispheres decreased by 10% and 8%, respectively, due to the postural change from 0° to 60° with major change occurring at 60°. Mean mFV for the Rt MCA at 0 degree (mean 44.9, SD ± 8.7) decreased ( p = 0.04) at 60° (mean 39.8, SD ± 7.2). Mean mFV for the Lt MCA at 0° (mean 44.0, SD ± 14) decreased ( p = 0.14) at 60° (mean 39.9, SD ± 12). PI remained unchanged (mean 1.0 at 60°, 1.0 at 30°, and 0.9 at 0°) at each head position, indicating no distal increase in resistance to blood flow. Conclusions: We found that up to 30° to 45° head elevation did not significantly affect the CBF velocity. Generalizability is limited by small sample size.