Atypical triphasic waves associated with the use of pentobarbital

To report a case in which triphasic waves developed during pentobarbital treatment. Pentobarbital coma is indicated in status epilepticus, refractory to other anticonvulsants, and in certain neurologic conditions in order to decrease brain metabolism. At high doses of pentobarbital, the EEG shows a typical burst-suppression pattern, while at low doses, diffuse slowing. Triphasic waves have not been reported in association with pentobarbital. A 54-year-old female underwent surgery for giant ophthalmic aneurysm clipping. Due to tearing and bleeding of the carotid artery, a clamp was placed, an external-internal carotid artery bypass was done, and the patient was started on pentobarbital. The patient remained comatose, the EEG showed a burst-suppression pattern, and the pentobarbital level was 30.5 micrograms/dl. One week later, the patient was still comatose, the EEG showed generalized triphasic waves with anterior predominance, and the pentobarbital level was 11 micrograms/dl. One day later, the patient was awake, and the EEG was normalized. The patient made a complete recovery. Triphasic waves may be seen in patients on pentobarbital. It is important to recognize this finding in patients on pentobarbital due to status epilepticus. This pattern should not be misinterpreted as 'electrical' status epilepticus.