ICU · Neurocritical care / monitoring

Brain Tissue Oxygen (PbtO2) & Multimodality Neuromonitoring

Also known as Brain tissue oxygen · PbtO2 · Licox · Multimodality monitoring · Cerebral microdialysis · Jugular venous oxygen saturation · SjvO2 · Pressure reactivity index · PRx · BOOST trial · Lactate-pyruvate ratio

No single neuromonitor is sufficient. The ICP monitoring alone misses the brain tissue hypoxia (the PbtO2 can be low even when the ICP is normal). Multimodality neuromonitoring integrates the ICP, the PbtO2 (brain tissue oxygen, measured by the Licox probe; normal 20-40 mmHg, target above 15-20 mmHg), the SjvO2 (the jugular venous oxygen saturation, 55-75 per cent; below 50 is the cerebral hypoxia), the cerebral microdialysis (a lactate-pyruvate ratio of 40 or more with brain glucose under 0.7 mmol/L defines the metabolic crisis), the continuous EEG (for the non-convulsive status), the transcranial Doppler (the Lindegaard ratio for the vasospasm), and the PRx (the pressure reactivity index for the optimal CPP). The PbtO2-guided therapy (the BOOST-2 trial) reduced the burden of brain tissue hypoxia (proportion of time hypoxic 0.45 to 0.16) on top of ICP/CPP-guided care in severe TBI, with a trend toward better outcome — the Phase III BOOST-3 trial followed. This topic covers each monitor, its thresholds, and the integrated, protocolised therapy that treats the patient rather than the number.