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

Brain multimodal monitoring including intracranial pressure (ICP) and brain tissue oxygen pressure (PbtO₂) 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.

To examine the accuracy of ICP, PbtO₂ and the oxygen ratio (OxR) in detecting regional cerebral hypoperfusion, assessed using perfusion cerebral computed tomography (CTP) in patients with acute brain injury.

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 PbtO₂ monitoring. Before CTP, FiO₂ was increased directly from baseline to 100% for a period of 20 min under stable conditions to test the PbtO₂ catheter, as a standard of care. Cerebral monitoring data were recorded and samples were taken, allowing the measurement of arterial oxygen pressure (PaO₂) and PbtO₂ at FiO₂ 100% as well as calculation of OxR (= ΔPbtO₂/ΔPaO₂). Regional CBF (rCBF) was measured using CTP in the tissue area around intracranial monitoring by an independent radiologist, who was blind to the PbtO₂ 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).

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, PbtO₂ and OxR were significantly different between CTP with and without hypoperfusion. Also, rCBF was correlated with ICP (r = - 0.27; p = 0.01), PbtO₂ (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 + PbO₂ (AUC = 0.78 [0.68-0.87]) or ICP + PbtO₂ + 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.

The combination of ICP and PbtO₂ 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.