Invasive and noninvasive assessment of cerebral oxygenation in patients with severe traumatic brain injury

Abstract

Purpose: The aim of this study is to investigate the relationship between invasive brain tissue oxygen pressure (PbrO2) and noninvasive regional transcranial oxygen saturation (rSO2) in 22 stable patients with severe traumatic brain injury (TBI) during a 16 h period. Methods: This was a prospective, observational study carried out in the Neurocritical Care Unit of a level 1 trauma center in a teaching hospital. A total of 41,809 paired records for neuromonitoring variables were analyzed and compared. Results: A direct and independent correlation between rSO2 and PbrO2 was con-firmed through adjusted [b coefficient and (95% confidence interval, CI) = 0.36 (0.35-0.37)] and logistic [PbrO2 ≥15 mmHg, as a dependent variable; adjusted odds ratio (AOR) and (95% CI) = 1.11 (1.10-1.12)] regression analyses. A receiver-operating characteristic (ROC) curve demonstrated that rSO2 had low accuracy for detecting moderate (PbrO2 ≤15 mmHg) intracerebral hypoxia [area under curve (AUC) = 0.62], with the likelihood ratio for a positive test (LR+) = 1.2 for an optimal cutoff of rSO2 ≤70%. In contrast, the ROC analysis showed that rSO 2 was moderately accurate for detecting severe (PbrO2 ≤12 mmHg) intracerebral hypoxemia (AUC = 0.82; LR+ = 5.3) for an optimal cutoff of rSO2 ≤60%. Conclusions: In patients with severe TBI, PbrO2 and rSO2 were directly and significantly related. Severe intracerebral hypoxia was better detected by rSO2 than was moderate intracerebral hypoxia. However, the diagnostic accuracy of rSO 2 was limited, and this measure should not be considered a substitute for routine PbrO2 monitoring. © 2010 jointly held by Springer and ESICM.