Measurement of brain tissue oxygenation performed using positron emission tomography scanning to validate a novel monitoring method

Object. The benefits of measuring cerebral oxygenation in patients with brain injury are well accepted; however, jugular bulb oximetry, which is currently the most popular monitoring technique used has several shortcomings. The goal of this study was to validate the use of a new multiparameter sensor that measures brain tissue oxygenation and metabolism (Neurotrend) by comparing it with positron emission tomography (PET) scanning. Methods. A Neurotrend sensor was inserted into the frontal region of the brain in 19 patients admitted to the neurointensive care unit. After a period of stabilization, the patients were transferred to the PET scanner suite where C15O, O-15(2) and (H2O)-O-15 PET scans were obtained to facilitate calculation of regional cerebral blood volume, O-2 metabolism, blood flow, and O-2 extraction fraction (OEF). Patients were given hyperventilation therapy to decrease arterial CO2 by approximately 1 kPa (7.5 mm Hg) and the same sequence of PET scans was repeated. For each scanning sequence, end-capillary O-2 tension (PvO(2)) was calculated from the OEF and compared with the reading of brain tissue O-2 pressure (PbO2) provided by the sensor. In three patients the sensor was inserted into areas of contusion and these patients were eliminated from the analysis. In the subset of 16 patients in whom the sensor was placed in healthy brain, no correlation. was found between the absolute values of PbO2 and PvO(2) (r = 0.2, p = 0.29;); however a significant correlation was obtained between the change in PbO2 (DeltaPbO(2)) and the change in PvO(2) (DeltaPvO(2)) produced by hyperventilation in a 20-mm region of interest around the sensor (p = 0.78, p = 0.0035). Conclusions. The lack of correlation between the absolute values of PbO2 and PvO(2) indicates that PbO2 cannot be used as a substitute for PvO(2). Nevertheless, the positive correlation between DeltaPbO(2) and DeltaPvO(2) when the sensor had been inserted into healthy brain suggests that tissue PO2 monitoring may provide a useful tool to assess the effect of therapeutic interventions in brain injury.