Abstracts

Rationale: Continuous electroencephalography (cEEG) is a valuable tool in the management of status epilepticus (SE) and guides treatment with antiepileptics (AEDs) and anesthetics. Ketamine is an anesthetic that has been recently employed in the treatment of SE. In patients undergoing anesthesia, Ketamine induces an alpha fronto-central rhythm that resembles EEG spindle oscillations generated by the reticular thalamus. We describe characteristic EEG rhythms induced by Ketamine in the status epilepticus population and its efficacy in control of ongoing seizures in refractory SE. Methods: Records of 24 patients with SE requiring cEEG monitoring between July 2011 and June 2012 were reviewed. Ten received Ketamine as part of AED regimen at doses 8 to 92 microgram/kg/min for 2 to 14 days. EEGs were reviewed prior to initiation, during administration, and after cessation of Ketamine. Results: Ten of 24 (41%) received Ketamine as part of the treatment for SE. No clear adverse effects were reported with prolonged use of Ketamine. Characteristic EEG changes described as generalized frontally predominant archiform theta and alpha rhythms (7 to 13 Hz) of 25 to 35 microvolts in amplitude were seen in 4 patients. The appearance of such EEG changes was not dependent on dose (range 8 to 67 mcg/kg/min) and occurred regardless of co-administration of other anesthetics. All four patients with ketamine EEG effect had temporal or frontotemporal SE. In 3 of 4 (75%), Ketamine introduction resulted in termination of SE without burst suppression. In all six patients without characteristic EEG changes, Ketamine did not provide resolution of status. In 3 of 6, the cessation of status was eventually achieved with the addition of pentobarbital (2), and with focal brain resection (1). Three of these patients died while no deaths were reported in the group where Ketamine successfully aborted status epilepticus. Five of the six patients had extratemporal SE. Conclusions: Ketamine causes a characteristic fronto-central archiform theta and alpha rhythms in some patients being treated for SE. The underlying mechanism that generates this surface EEG pattern is unknown, but it appears to correlate with success of Ketamine in aborting SE. This may be related to the underlying pathophysiology of the patient's SE, localization of the seizure activity and patient's potential susceptibility to Ketamine.