Inclusion Criteria:  To be included in the study, subjects must be 18 - 80 years of age Non-traumatic cardiac arrest (regardless of non-perfusing rhythm, etiology, or location of arrest) in whom the decision to treat unequivocal electrographic SE (as defined by the American Clinical Neurophysiology Society: having generalized spike/sharp-wave discharges ≥ 3Hz or any evolving pattern reaching > 4Hz, lasting ≥ 10 minutes, or comprising > 50% of any hour of recording) has been made, Requiring anesthetic infusion for any reason, Have reliable arterial access for frequent blood sampling Be enrolled and have the first specimen drawn within 48 hours of PASE onset.  Exclusion Criteria:  Subjects must not have a prior history of generalized epilepsy Be pregnant or Have PASE onset preceding initiation of EEG monitoring.