Abstract
The positioning of intracranial hypertensive patients for treatment of intracranial pressure (ICP) and cerebral perfusion pressure (CPP) varies among institutions and the optimal grade of head elevation is still under discussion. Reductions in intracranial pressure at head elevation have been noted both experimentally and clinically. However, since the reports suggested that CPP is a better predictor of outcome than ICP and that patients with a CPP of less than 40 mmHg have a poor prognosis regardless of ICP, we have to take CPP into consideration. The purpose of this study was to investigate the effect on the ICP, CPP and Pressure Volume Index (PVI) of 30゜ head elevated position in severely head injured patients. Twenty three severely head injured patients (GCS≤8) were involved in this study. All patients remained intubated, paralyzed and mechanically ventilated during the study. ICP was measured by fluid filled ventricular catheter connecting to a bedside monitor and the radial artery was cannulated for blood pressure measurement. The transducer level of both ICP and blood pressure were always referred to foramen of Monro. The CPP was calculated by the following equation : CPP=mean BP-mean ICP. Patients were positioned at O゜ head elevation first, then elevated to 30゜ and returned to O゜ head elevation again. Each position was maintained for exactly 15 minutes. Thirty two studies were performed among 23 patients. PVI at O゜ head elevation were obtained in all patients and PVI at 30゜ head elevation were obtained in 10 patients after 15 minutes head elevation. At the 30゜ head elevation, ICP was decreased in each study, however CPP was altered differently. Of the 32 studies were performed, the CPP of 12 studies were increased or remained unchanged and the CPP of 20 studies were decreased. The PVI was statistically lower in the patients whose CPP were increased or remained unchanged at 30゜ head elevation. We concluded that 30゜ head elevation benefits the patients those who have a tight brain (low PVI). Our data also showed that PVI was not altered by 30゜ head elevation, suggesting brain compliance remains stable during position change.
