WASHINGTON (FRONTLINE MEDICAL NEWS) Burst suppression patterns on EEGs of comatose patients after cardiac arrest is not necessarily associated with poor outcomes, according to findings from a retrospective study presented at the annual meeting of the American Epilepsy Society.

Traditionally, burst suppression patterns (BSP) in post–cardiac arrest patients, especially without anesthesia or cooling, has been considered strongly associated with poor network-level recovery, but findings reported by Krithiga Sekar, MD, PhD, and her colleagues in a poster at the meeting show that patients with BSP on EEG recover consciousness with the same frequency as do those who recover without BSP.

In fact, Dr. Sekar, an epilepsy fellow at Columbia University, New York, and her colleagues asserted that prognoses of poor outcomes are more accurately associated with characteristics of the signals themselves, with some cases of BSP acting as a neuroprotective mechanism during metabolic stress.

“The brain is inactivated discontinuously, so those cells that are particularly vulnerable and that are at the threshold of survival, had they been activated continuously, might not have survived,” said Dr. Sekar, who was a neurology resident at Cornell University, New York, when the study was conducted. “Maybe activating them discontinuously is a protective mode that the brain takes on to rescue those cells from death in the setting of this massive metabolic disarray that occurs after cardiac arrest.”

Dr. Sekar and her coinvestigators retrospectively studied 73 cardiac arrest patients who underwent therapeutic hypothermia with continuous video EEG monitoring at Cornell. Of those studied, 45 (62%) had BSP on EEG, a common occurrence after cardiac arrest, according to Dr. Sekar.

Of those with BSP on EEG, 14 (31%) recovered consciousness within the first 72 hours of arrest, as did 10 (36%) who recovered without BSP.

For those who did not recover, the median number of days hooked up was around 9, much longer than in other studies, which could be why more patients recovered compared with those in older literature, according to Dr. Sekar and her fellow investigators.

“The length of time for withdrawal of care was around 9 or 10 days, while much of the literature I had read had withdrawal of care within the first 4 or 5 days,” Dr. Sekar said. “If people think [BSP] is a poor prognosticator, they will withdraw care more often, and then that accumulates more data that this is a poor prognosticator.”

Of the 49 who did not recover, 12 patients in the BSP group and 10 patients in the non-BSP group had care withdrawn.

During the study, Dr. Sekar and her colleagues found two patients with spontaneous BSP, both of whom were taken off anesthetics and remained in burst suppression: one for 72 hours and one for 4 days. Both patients fully recovered consciousness.

When first induced, the patients with spontaneous BSP started with bursts that had more of a delta feature. However, once spontaneous BSP kicked in, a prominent theta feature emerged and grew increasingly more evident.

The investigators found similar theta features in patients who recovered with only induced and reduced BSP. But those who did not do well either had a flat spectra, similar to type A EEG that is correlated with poor outcomes, or had some signs of theta features within 72 hours and then lost them.

“This suggests this theta frequency activity within the bursts, maybe it signals underlying networks that are potentially recoverable and are necessary for consciousness,” Dr. Sekar explained. “In these cases, maybe they were early on available but as energy dynamics lagged behind recovery of the brain, maybe they just never got those networks to function again.”

Going forward, Dr. Sekar and her colleagues plan to do a prospective study with a longer period of observation to see the effects of these theta frequency features.

The study was supported by individual grants from the National Institutes of Health, a Leon Levy Neuroscience Fellowship Award, and several foundations. The investigators reported no relevant financial disclosures.

SOURCE: Sekar K et al., AES Abstract 1.097


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