CAUSE, DISTRIBUTION AND SIGNIFICANCE OF EPISODES OF REDUCED CEREBRAL PERFUSION-PRESSURE FOLLOWING HEAD-INJURY

A group of 74 patients with head injury (54 severe, 17 moderate and 3 minor) had continuous monitoring of both arterial and intracranial pre ssure with computer-based registration of these pressures, cerebral pe rfusion pressure and other vairables. In 60 patients cerebral perfusio n pressure CPP fell below 60 mm Hg for periods of 5 minutes or longer. The distribution over time of these reductions in CPP during up to 12 days of monitoring was studied, and each episode of reduced CPP was a ttributed to a fall in arterial pressure, an increase in intracranial pressure, or both. Two clusters of reduced CPP were found, one during the first 24 hours of monitoring, when reduced CPP was mainly caused b y a reduction in arterial pressure, and the other at 5 or 6 days after injury, when reduced CPP was due mainly to an increase in intracrania l pressure. There was a significant correlation between low CPP due to reduced arterial pressure and the Injury Severity Score (p < 0.001), suggesting that resuscitative measures may have been less than optimal in these cases. There was also significant correlation between the du ration of low CPP and low arterial pressure and an adverse outcome fro m injury as assessed at 6, 12 and 24 months after injury (p < 0.001). It is recommended that in patients with severe and significant head in jury who require monitoring, this should include both arterial and int racranial pressure, be continued for at least 6 days, that cerebral pe rfusion pressure should be displayed and recorded, and that particular attention is paid to detecting and correcting even small reductions i n arterial pressure, especially those that reduce CPP below 60 mm Hg.