Abstract
IntroductionBrain 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.AimTo 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.MethodsSingle-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).ResultsEighty-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.ConclusionsThe 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.
Highlights
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)
The combination of ICP and P btO2 monitoring provides a better detection of cerebral hypoperfusion than ICP alone in patients with acute brain injury
Imaging techniques can provide relevant information on cerebral blood flow (CBF) alterations after acute brain injury; in particular, cerebral computed tomography perfusion (CTP) imaging, which was initially introduced to estimate the infarct core size and evaluate the time window for thrombolysis and thrombectomy in ischemic stroke [9], can detect perfusion deficits associated with cerebral vasospasm, which might occur in patients suffering from subarachnoid hemorrhage (SAH), or reduced CBF around contusion areas and cerebral perfusion heterogeneity in the early phase of TBI [10, 11]
Summary
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). On the opposite to the initial brain injury, whose severity can be barely modified, secondary brain injuries (SBIs) could be detected and potentially avoidable. Those SBI, including either cerebral (i.e., brain edema, tissue hypoxia, seizures) or systemic (i.e., hypotension, hypocapnia, hypoxemia, dysglycemia, hyponatremia, fever and anemia) events, can enhance the extent of the primary brain insult and further contribute to poor outcome in this setting [4,5,6,7]. CTP is not a bedside tool, does not provide continuous CBF measurement and can be associated with some adverse events, such as high-dose radiation exposure and an increased risk of elevated intracranial pressure (ICP) during the in-hospital transfer to the radiology unit [12]
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