Limitations of Threshold-Based Brain Oxygen Monitoring for Seizure Detection
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Brain tissue oxygen (PbtO2) monitors are utilized in a threshold-based fashion, triggering actions based on the presumption of tissue compromise when PbtO2 is less than 20 mmHg. Some early published practice guidelines suggest that seizure is a potential culprit when PbtO2 crosses this threshold; evidence for this is not well defined.
Data were collected manually as part of a prospective observational database. PbtO2 monitors and continuous electroencephalogram (cEEG) were placed by clinical protocol in aneurysmal subarachnoid hemorrhage (aSAH) or traumatic brain injury (TBI) patients with a Glasgow Coma Scale (GCS) ≤ 8. Eight patients with discrete seizures during an overlapping monitored period were identified. Probability of seizure when PbtO2 value was <20 mmHg (and the inverse) were calculated.
There were 343 distinct seizure episodes and 1797 PbtO2 measurements. 8.9% of seizures were followed by a PbtO2 value below 20 mmHg. Of all observed low PbtO2 values, 3.8% were associated with seizure. Seizure length did not influence PbtO2. Two patients with the highest number of seizures developed low PbtO2 values post-seizure.
Seizures were neither associated with a PbtO2 value of <20 mmHg nor associated with a drop in PbtO2 value across a clinically significant threshold. However, we cannot rule out the existence of any relationship between PbtO2 and seizure with this limited data set. Prospective research using electronically recorded data is required to more effectively examine the relationship between PbtO2 and seizure.
KeywordsTraumatic brain injury Physiologic monitoring Subarachnoid hemorrhage Non-convulsive seizure disorder Oxygen/Metabolism Brain injuries/physiopathology
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