From: Management of delayed cerebral ischemia after subarachnoid hemorrhage
Device | Physiological parameter measured | Normal range | Pathological condition |
---|---|---|---|
Continuous electroencephalography | Brain activity Epileptiform discharges | • Alpha/delta ratio > 50 % • No epileptiform discharges • Reactivity to stimuli | • Alpha/delta ratio < 50 % • Epileptiform discharges • No reactivity |
Transcranial Doppler ultrasound | Mean blood flow velocity (FVm) | • FVm MCA: 30–75 cm/s | • MCA FVm 120–180 cm/s: intermediate probability of vasospasm • MCA FVm >180 cm/s: high probability of vasospasm |
Cerebral blood flow monitor (Hemedex) | Cerebral blood flow (CBF) | • >40 ml/100 g/min | • <20 ml/100 g/min: indicative of ischemia assuming preserved metabolic demand |
Jugular venous oximetry | Balance between oxygen delivery and consumption (SjO2) | • 50–75 % | • <50 %; increased oxygen extraction fraction, indicative of ischemia |
Brain tissue oxygen tension (Licox) | Regional parenchymal brain tissue oxygen tension (PbtO2) | • 25–35 mmHg in white subcortical matter | • <20 mmHg: indicative of cerebral hypoxia |
Cerebral microdialysis | • Glucose • Lactate • Pyruvate • Lactate/pyruvate ratio • Glutamate • Glycerol | • 0.8–4.0 μmol/L • 0.7–3.0 μmol/L • Unknown • < 25 • 2–10 μmol/L • 10–90 μmol/L | • <0.2 μmol/L • ≥4.0 μmol/L • Unknown • >40 indicative of anaerobic metabolism • >10 μmol/L • >90 μmol/L |