gms | German Medical Science

Objective: Neuromonitoring in neurocritically ill patients using continuous PbrO₂-measurement has been widely accepted. However, only one reliable PbrO₂-neuromonitoring system in clinical use has been sufficiently studied so far. New PbrO₂-technologies are now available on the market. Our goal is to test a new PbrO₂-probe (TO, Raumedics^®) vs. the established Licox-technology (IntegraNeurosciences^®).

Methods: In nine male swine two different (TO vs. Licox) PbrO₂-catheters were implanted into the subcortical area. Contralaterally, a parenchymal ICP-probe was inserted. All relevant physiological parameters were continuously recorded. We performed physiological maneuvers such as FiO₂-challenges, medically induced hypo- and hypertension, TRIS-buffer application and hyper- and hypoventilation. Post mortem the parenchymal catheter locations were macroscopically controlled. Bland-Altman plots were generated to statistically compare both technologies.

Results: The Bland-Altman analysis revealed a good comparability of both technologies under baseline conditions (mean_diff = 2,09 mm Hg). Mean values during FiO₂-challenges (FiO₂ = 100%) showed significantly different profiles. The TO-probe reached up to 1.5 fold higher PbrO₂ values than the Licox-probe. This may be explained by an “O₂-consumptive” effect of the Licox technology. During hypoventilation (FiO₂ = 5%), the TO-probe indicated the hypoxic level of 8.5 mm Hg two minutes before Licox which may play an important role in critically ill patients. All other maneuvers showed similar responses in both technologies. The TO-probe is easy to handle, and does not need a specific storage or calibration procedure before implantation. It is a solid probe that is not very sensitive to breakage. It can be inserted using a multilumen bolt-kit as the caliber is small (2 mm). In addition, the brain temperature is recorded simultaneously.

Conclusions: We present a new PbrO₂-technology that was experimentally compared to the “gold standard” Licox. We provide data that the new PbrO₂ technology (TO) will reliably measure PbrO₂ under physiological conditions as compared to Licox. However, the TO-probe is more sensitive to O₂-changes which may have a positive effect on patient outcome, especially with critically low PbrO₂-values. Further studies, i.e. using cerebral microdialysis, are needed to evaluate whether both technologies have the same numeric hypoxic level.