Electrographic and Clinical Determinants of Good Outcome After Postanoxic Status Epilepticus

Postanoxic electrographic status epilepticus (PSE) affects up to a third of all comatose patients after cardiac arrest (CA) and is associated with high mortality. Late PSE onset (>24 hours), from a restored continuous background pattern, and absence of established indicators of poor outcome at multimodal prognostication are described in survivors. We aimed to determine the increase in probability of good long-term outcome after PSE in patients presenting with this favorable PSE profile compared with all patients with PSE.

This is a prospective observational substudy of the international Targeted Hypothermia vs Targeted Normothermia After Out-of-Hospital Cardiac Arrest trial (TTM2-trial, 2017-2020) including adult comatose patients resuscitated from CA with continuous EEG (cEEG) monitoring. EEG background pattern and type of PSE were determined using standardized EEG terminology of the American Clinical Neurophysiology Society, blinded to clinical data. On day 4, multimodal prognostication was performed according to the European postresuscitation guidelines. Good outcome was defined as a modified Rankin Scale score of 0-3 at 6 months. Detailed follow-up was performed at 6 and 24 months.

A total of 191 patients were monitored with cEEG, of whom 52 (27%) developed possible or definite PSE at a median of 42 hours [IQR 32-46] after CA. The median age was 70 (IQR 63-77) years, and 35% were female. Favorable PSE profile was present in 20 patients (38%), of whom 12 patients (60%) survived until 6 months and 8 (40%) had good outcome; thus, the probability of good outcome increased 2.7 times. All patients lacking a favorable PSE profile had poor outcome. All patients with good outcome obeyed commands within the first 7 days. At 24 months, all 12 survivors were still alive and 7 had good functional outcome. Detailed follow-up at 24 months showed that most had only mild cognitive impairment and overall life satisfaction was similar to the general population.

PSE is compatible with good outcome when onset is late and from a continuous background and no established indicators of poor outcome are present. One-third of patients with PSE had favorable PSE profile, of whom well over a third eventually had good outcome and showed improved level of consciousness within the first week.

ClinicalTrials.gov Identifier: NCT02908308.