Automated measurement of "pressure times time dose" of intracranial hypertension best predicts outcome after severe traumatic brain injury.
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 <or=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.
Kahraman
Sibel
S
Department of Anesthesiology, University of Maryland School of Medicine, Baltimore, Maryland 21201, USA.
Dutton
Richard P
RP
Hu
Peter
P
Xiao
Yan
Y
Aarabi
Bizhan
B
Stein
Deborah M
DM
Scalea
Thomas M
TM
D000328:Adult; D001930:Brain Injuries / Q000150:complications / Q000175:diagnosis / Q000503:physiopathology*; D003422:Critical Care / Q000379:methods; D005260:Female; D006801:Humans; D019586:Intracranial Hypertension / Q000209:etiology* / Q000503:physiopathology; D007902:Length of Stay; D008297:Male; D008991:Monitoring, Physiologic / Q000379:methods; D011379:Prognosis; D018709:Statistics, Nonparametric; D016896:Treatment Outcome