Detection of cerebral hypoperfusion with a dynamic hyperoxia test using brain oxygenation pressure monitoring

Introduction Brain multimodal monitoring including intracranial pressure (ICP) and brain tissue oxygen pressure (PbtO 2 ) is more accurate than ICP alone in detecting cerebral hypoperfusion after traumatic brain injury (TBI). No data are available for the predictive role of a dynamic hyperoxia test in brain-injured patients from diverse etiology. Aim To examine the accuracy of ICP, PbtO 2 and the oxygen ratio (OxR) in detecting regional cerebral hypoperfusion, assessed using perfusion cerebral computed tomography (CTP) in patients with acute brain injury. Methods Single-center study including patients with TBI, subarachnoid hemorrhage (SAH) and intracranial hemorrhage (ICH) undergoing cerebral blood flow (CBF) measurements using CTP, concomitantly to ICP and PbtO 2 monitoring. Before CTP, FiO 2 was increased directly from baseline to 100% for a period of 20 min under stable conditions to test the PbtO 2 catheter, as a standard of care. Cerebral monitoring data were recorded and samples were taken, allowing the measurement of arterial oxygen pressure (PaO 2 ) and PbtO 2 at FiO 2 100% as well as calculation of OxR (= ΔPbtO 2 /ΔPaO 2 ). Regional CBF (rCBF) was measured using CTP in the tissue area around intracranial monitoring by an independent radiologist, who was blind to the PbtO 2 values. The accuracy of different monitoring tools to predict cerebral hypoperfusion (i.e., CBF < 35 mL/100 g × min) was assessed using area under the receiver-operating characteristic curves (AUCs). Results Eighty-seven CTPs were performed in 53 patients (median age 52 [41–63] years—TBI, n = 17; SAH, n = 29; ICH, n = 7). Cerebral hypoperfusion was observed in 56 (64%) CTPs: ICP, PbtO 2 and OxR were significantly different between CTP with and without hypoperfusion. Also, rCBF was correlated with ICP ( r = − 0.27; p = 0.01), PbtO 2 ( r = 0.36; p < 0.01) and OxR ( r = 0.57; p < 0.01). Compared with ICP alone (AUC = 0.65 [95% CI, 0.53–0.76]), monitoring ICP + PbO 2 (AUC = 0.78 [0.68–0.87]) or ICP + PbtO 2 + OxR (AUC = 0.80 (0.70–0.91) was significantly more accurate in predicting cerebral hypoperfusion. The accuracy was not significantly different among different etiologies of brain injury. Conclusions The combination of ICP and PbtO 2 monitoring provides a better detection of cerebral hypoperfusion than ICP alone in patients with acute brain injury. The use of dynamic hyperoxia test could not significantly increase the diagnostic accuracy.