Brief Episodes of Intracranial Hypertension and Cerebral Hypoperfusion Are Associated With Poor Functional Outcome After Severe Traumatic Brain Injury

Background: Management strategies after severe traumatic brain injury (TBI) target prevention and treatment of intracranial hypertension (ICH) and cerebral hypoperfusion (CH). We have previously established that continuous automated recordings of vital signs (VS) are more highly correlated with outcome than manual end-hour recordings. One potential benefit of automated vital sign data capture is the ability to detect brief episodes of ICH and CH. The purpose of this study was to establish whether a relationship exists between brief episodes of ICH and CH and outcome after severe TBI. Materials: Patients at the R Adams Cowley Shock Trauma Center were prospectively enrolled over a 2-year period. Inclusion criteria were as follows: age > 14 years, admission within the first 6 hours after injury, Glasgow Coma Scale score < 9 on admission, and placement of a clinically indicated ICP monitor. From high-resolution automated VS data recording system, we calculated the 5-minute means of intracranial pressure (ICP), cerebral perfusion pressure (CPP), and Brain Trauma Index (BTI = CPP/ICP). Patients were stratified by mortality and 6-month Extended Glasgow Outcome Score (GOSE). Results: Sixty subjects were enrolled with a mean admission Glasgow Coma Scale score of 6.4 +/- 3.1, a mean Head Abbreviated Injury Severity Scale score of 4.2 +/- 0.7, and a mean Marshall CT score of 2.5 +/- 0.9. Significant differences in the mean number of brief episodes of CPP < 50 and BTI < 2 in patients with a GOSE 1-4 versus GOSE 5-8 (9.4 vs. 4.7, p = 0.02 and 9.3 vs. 4.9, p = 0.03) were found. There were significantly more mean brief episodes per day of ICP > 30 (0.52 vs. 0.29, p = 0.02), CPP < 50 (0.65 vs. 0.28, p < 0.001), CPP < 60 (1.09 vs. 0.7, p = 0.03), BTI < 2 (0.66 vs. 0.31, p = 0.002), and BTI < 3 (1.1 vs. 0.64, p = 0.01) in those patients with GOSE 1-4. Number of brief episodes of CPP < 50, CPP < 60, BTI < 2, and BTI < 3 all demonstrated high predictive power for unfavorable functional outcome (area under the curve = 0.65-0.75, p < 0.05). Conclusions: This study demonstrates that the number of brief 5-minute episodes of ICH and CH is predictive of poor outcome after severe TBI. This finding has important implications for management paradigms which are currently targeted to treatment rather than prevention of ICH and CH. This study demonstrates that these brief episodes may play a significant role in outcome after severe TBI.