Monitoring brain tissue oxygen tension in brain-injured patients reveals hypoxic episodes in normal-appearing and in peri-focal tissue

Objective We compared brain tissue oxygen tension (PtiO₂) measured in peri-focal and in normal-appearing brain parenchyma on computerized tomography (CT) in patients following traumatic brain injury (TBI). Design Prospective observational study. Setting Neurointensive care unit. Patients and participants Thirty-two consecutive TBI patients were subjected to PtiO₂ monitoring. Interventions Peri-focal tissue was identified by the presence of a hypodense area of the contusion and/or within 1 cm from the core of the contusion. The position of the tip of the PtiO₂ probe was assessed at follow-up CT scan. Measurements and results Mean PtiO₂ in the peri-contusional tissue was 19.7 ± 2.1 mmHg and was lower than PtiO₂ in normal-appearing tissue (25.5 ± 1.5 mmHg, p < 0.05), despite a greater cerebral perfusion pressure (CPP) (73.7 ± 2.3 mmHg vs. 67.4 ± 1.4 mmHg, p < 0.05). We observed both in peri-focal tissue and in normal-appearing tissue episodes of brain hypoxia (PtiO₂ < 20 mmHg for at least 10 min), whose median duration was longer in peri-focal tissue than in normal-appearing tissue (51% vs. 34% of monitoring time, p < 0.01). In peri-focal tissue, we observed a progressive PtiO₂ increase from pathologic to normal values (p < 0.01). Conclusions Multiple episodes of brain hypoxia occurred over the first 5 days following severe TBI. PtiO₂ was lower in peri-contusional tissue than in normal-appearing tissue. In peri-contusional tissue, a progressive increase of PtiO₂ from pathologic to normal values was observed over time, suggestive of an improvement at microcirculatory level.