Association between cerebral oxygenation and usual parameters of cerebral perfusion in critically ill patients with acute brain injury

In patients with acute brain injury (ABI), optimizing cerebral perfusion parameters relies on multimodal monitoring. This include data from systemic monitoring–mean arterial pressure (MAP), arterial carbon dioxide tension (PaCO₂), arterial oxygen saturation (SaO₂), hemoglobin levels (Hb), and temperature–as well as neurological monitoring–intracranial pressure (ICP), cerebral perfusion pressure (CPP), and transcranial Doppler (TCD) velocities. We hypothesized that these parameters alone were not sufficient to assess the risk of cerebral ischemia. We conducted a retrospective, single-center study of patients admitted in our ICU between 2015 and 2021. Patients with ABI and multimodal neuromonitoring were included. ABI included traumatic brain injury (TBI), subarachnoid hemorrhage (SAH), intracranial hemorrhage and ischemic stroke. The relationship between jugular venous oxygen saturation (SjvO₂) and cerebral perfusion parameters was analyzed. Patients were categorized into two groups based on SjvO₂, with a threshold of 60% used to define cerebral ischemia. We compared the parameters used to optimize cerebral perfusion between groups and their diagnosis accuracy for cerebral ischemia was evaluated. Univariable and multivariable analyses were performed to assess the association between the guideline-recommended therapeutic targets and the risk of cerebral ischemia. 601 evaluations from 96 patients with simultaneous ICP, SjvO₂ and TCD were analyzed. Poor relationships were found between SjvO₂ and the parameters of cerebral perfusion. TCD flow velocities and PaCO₂ were lower in the cerebral ischemia group while MAP, ICP and CPP were not different between groups. Most ischemic episodes occurred despite ICP < 22 mmHg and CPP ≥ 60 mmHg. For the diagnosis of cerebral ischemia, only TCD parameters and PaCO₂ were associated with an area under the curve (AUC) > 0.5 but with a low accuracy. In multivariable analysis, the only guideline-recommended therapeutic target associated with a reduction of cerebral ischemia was a diastolic flow velocity (FV) > 20 cm.s⁻¹.