The cause and incidence of secondary insults in severely head-injured adults and children

The cause and incidence of reductions in cerebral perfusion pressure, and r ises in intracranial pressure have been examined in a series of patients wi th severe head injury defined as an initial Glasgow Coma Sum of less than o r equal to 8. Two-hundred-and-seven adults (aged over 16 years) and 84 chil dren admitted to Newcastle General Hospital, who had intracranial pressure monitoring as part of their routine management, were studied. Intracranial pressure (ICP), arterial pressure and cerebral perfusion pressure (CPP) wer e sampled and recorded every 2 min. Patients' CT findings were classified i nto distinct groups using the method described by Marshall. Secondary insul ts were defined using the Edinburgh University Secondary Insult Grades (EUS IG) and the incidence and cause (raised ICP, reduced CPP or a combination o f the two) was established. Outcome was assessed at 6 months using the Glas gow Outcome Scale. In the majority of adults with head injury it is the com bination of reduced arterial pressure and raised ICP that contributes to th e reduction in cerebral perfusion pressure. This was not the case for Diffu se Injury Type I. In children similar characteristics were found across eac h of the CT classifications. The vast majority of falls in CPP down to 60 m mHg were caused by reduced arterial pressure. Reductions below 50 mmHg were almost always due to a combination of both reduced arterial pressure and r aised ICP. The results in adults were similar, but not identical, to those of the paediatric cases. Diffuse Injury Type I stood out from all the other categories as the only one where reductions in perfusion pressure were alm ost exclusively due to reductions in arterial pressure and not to increases in ICP. The management of these patients should ensure the adequacy of per fusion pressure by maintaining arterial pressure at a satisfactory level. T hese results suggest that vigilant monitoring of both intracranial pressure and arterial pressure is required to lower the incidence of secondary insu lts.