Secondary insults prevalence, co-occurrence and relationship with outcome after severe TBI.

Introduction: Secondary insults due to high intracranial pressure (ICP), low cerebral perfusion pressure (CPP) and impaired cerebral pressure reactivity (PRx) predict outcome after severe traumatic brain injury (TBI). Research question: What is the prevalence, co-occurrence and prognostic importance of secondary insults due to deranged ICP, CPP or PRx after TBI. Material and methods: Severe TBI patients requiring ICP monitoring were included. Secondary insults due to ICP, PRx, and CPP were defined as having at least 1 h with a mean value above (or below for CPP) a respective threshold (ICP 20, CPP 60, and PRx 0.25). Percentage time with isolated or co-occurring insults was calculated (impaired ICP only, CPP only, PRx only, ICP and PRx, ICP and CPP, CPP and PRx, ICP CPP and PRx). Prognostic importance for mortality was assessed using a logistic regression model. Results: 822 patients were included of which 76% had elevated ICP, 92% had disturbed pressure reactivity and 55% had low CPP for at least an hour. Out of the total 115,459 h, 46,111 (40%) were spent with at least one variable within the defined secondary injury range. Odds ratios for mortality were greater for combined (impaired ICP, CPP and PRx OR 1.17 95%CI 1.09 to 1.28) than isolated insults (impaired ICP only OR 1.01 95%CI 1.00-1.02, impaired CPP only 1.00 95%CI 0.95-1.05). Discussion and conclusion: ICP and autoregulation insults are common after TBI and often occur independently. Concurrent ICP, CPP and PRx insults portend worse prognosis than when a single variable is deranged.