Automated Measurement of “Pressure Times Time Dose” of Intracranial Hypertension Best Predicts Outcome After Severe Traumatic Brain Injury

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Background:Earlier, more accurate assessment of secondary brain injury is essential in management of patients with traumatic brain injury (TBI). We assessed the accuracy and utility of high-resolution automated intracranial pressure (ICP) and cerebral perfusion pressure (CPP) recording and their analysis in patients with severe TBI.Methods:ICP and CPP data for 30 severe TBI patients were collected automatically at 6-second intervals. The degree and duration of ICP and CPP above and below treatment thresholds were calculated as “pressure times time dose” (PTD; mm Hg · h) using automated recordings (PTDa) or manual recordings (PTDm) for early stage (trauma resuscitation unit [TRU]) and total monitoring time (TRU and intensive care unit).Results:Bland-Altman plots showed lack of agreement between PTDa and PTDm. For ICP >20 mm Hg and CPP <60 mm Hg, PTDa, but not PTDm, was significantly higher in patients with unfavorable outcome (Extended Glasgow Outcome Scale score ≤4) than in patients with favorable outcome (Extended Glasgow Outcome Scale score >4). Total PTDa for ICP >20 mm Hg and CPP <60 mm Hg had high predictive power for functional outcome (area under the receiver operating characteristics curve: 0.92 ± 0.05 and 0.82 ± 0.08, respectively) and inhospital mortality (0.76 ± 0.15 and 0.79 ± 0.14, respectively) and were strongly correlated with length of intensive care unit stay (p = 0.009 and 0.007), length of hospital stay (p = 0.009 and 0.005), and discharge Glasgow Coma Scale scores (p = 0.008 and p = 0.038). PTDa of CPP >100 mm Hg during TRU monitoring and during the first 24 hours showed highest predictive power for mortality (area under the receiver operating characteristics curve: 0.72 ± 0.18 and 0.85 ± 0.13, respectively). PTDa was better than PTDm and the duration of episodes alone in predicting outcome.Conclusions:PTD calculation of high resolution ICP and CPP recording is a reliable and feasible way of monitoring severe TBI patients.

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