Context: Despite increasing use of extracorporeal-life-support (ECLS) for treatment of refractory cardiac arrest patients, prognosis remains dismal, often resulting in brain-death. However, clinical assessment of brain-death onset is difficult in post-cardiac arrest patients, sedated, paralyzed and under mild therapeutic hypothermia (MTH). 
The objective of this study was to assess usefulness of Bispectral Index (BIS) monitoring for detection of brain-death onset in refractory cardiac arrest patients treated by ECLS.
Methods: We performed a retrospective study in an intensive care unit at Necker hospital. Forty-six patients suffering from refractory cardiac arrest treated by ECLS were included. BIS was continuously recorded during ICU hospitalization. Clinical brain-death onset was confirmed when appropriate by EEG and/or cerebral CT scan.
Results: Twenty-nine patients evolved into brain-death and had average BIS values under MTH and after rewarming (temperature≥35°C) of 4 (0–47) and 0 (0–82), respectively. Among these, 11 (38%) entered into a procedure of organs donation. Among the 17 non-brain-dead patients, the average BIS values at admission and after rewarming were 39 (0–65) and 59 (22–82), respectively. Two patients had an admission BIS value equal to zero and evolved to a poor prognostic (Cerebral Performance Categorie scale of 4) and died after care limitations. In both groups, no difference was observed between the AUCs of ROC curves for BIS values under MTH and after rewarming (respectively 0.85 vs 0.96, p>0.05).
Conclusion: Despite mild hypothermia and ECLS, a lower BIS value after CA is associated with a poor neurological outcome. A BIS value of zero is a good predictor of brain death. 
Since BIS monitoring is non invasive and its interpretation requires a limited training, it could be used in refractory patients under ECLS and mild therapeutic hypothermia in ICU, in order to reduce time to organ harvesting and reducing waste of health resources in futile resuscitation.

Usefulness of the Bispectral Index (BIS) in patients treated by extra corporeal life support (ECLS) for refractory cardiac arrest