The Relationship of Vasogenic Waves to ICP and Cerebral Perfusion Pressure in Head Injured Patients

Abstract

Slow vasogenic waves are characterised by sudden rises and falls in both the mean ICP and its cardiac pulsatile amplitude for periods of up to an hour. On reviewing the on-line computer records of a series of 200 consecutive head injured patients, some 650 waves with increases in mean ICP of at least 15mmHg were recognized. The mean ICP, pulsatile amplitude, perfusion pressure, arterial pressure and pulse rates which had been generated every minute were reviewed in each of a 100 randomly selected waves in the hopes of allocating them into defined groups according to precipitating factors. We had expected to find that the majority of waves were precipitated by a preceding fall in cerebral perfusion pressure as a result of a transient arterial hypotension. Only in 19 of the 100 waves did this sequence become apparent and in the remainder, no recognizable precipitating factors were found. In 21 of the records, there was a fall in ICP of at least 5mmHg before the onset of the pressure wave.