Monitoring brain tissue oxygen tension in brain-injured patients reveals hypoxic episodes in normal-appearing and in peri-focal tissue
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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).
Prospective observational study.
Neurointensive care unit.
Patients and participants
Thirty-two consecutive TBI patients were subjected to PtiO2 monitoring.
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).
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.
KeywordsTraumatic brain injury Brain oxygenation Brain hypoxia PtiO2 Secondary insults Pathophysiology
The authors thank Angelo Colombo, MD for computer support, data processing and statistical advice; the students and nursing staff of the neurointensive care unit for their valuable cooperation.
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