Effect of backrest position on intracranial and cerebral perfusion pressures

Prevention of secondary injury resulting from increased intracranial pressure (ICP) and the promotion of adequate cerebral blood flow are major concerns of health care professionals caring for the neurologic patient. For the past two decades studies have indicated raising the head of the bed lowers ICP. However, when perfusion pressure has been measured along with ICP, results have been conflicting. Some investigators found cerebral perfusion pressure (CPP) decreased with head elevation; others found no change. This study examined the effect of four backrest positions (flat, head elevated 30 degrees, head elevated 30 degrees with knee gatch elevated and reverse Trendelenberg) on ICP, CPP and transcranial doppler flow velocities in four subjects. Each was placed in the flat position for 15 minutes followed by 15 minutes in one of the three randomly assigned elevated backrest positions. Findings suggest backrest position should be individually assigned after analysis of the response of the ICP, CPP and blood flow velocities to that position.