Burst-suppression with identical bursts: A distinct EEG pattern with poor outcome in postanoxic coma

https://doi.org/10.1016/j.clinph.2013.10.017Get rights and content

Highlights

  • “Burst-suppression with identical bursts” is a distinct pathological EEG pattern.

  • “Burst-suppression with identical bursts” is exclusively observed in patients after diffuse cerebral ischemia.

  • “Burst-suppression with identical bursts” is invariably associated with a poor outcome in comatose patients after cardiac arrest.

Abstract

Objective

To assess the incidence, quantified EEG characteristics, and prognostic significance of “burst-suppression with identical bursts” and to discuss potential pathophysiological mechanisms.

Methods

Burst-suppression EEGs were identified from a cohort of 101 comatose patients after cardiac arrest, and from our complete database of 9600 EEGs, since 2005. Patterns with and without identical bursts were classified visually by two observers. Of patients after cardiac arrest, outcomes were assessed at three and six months. Identical and non-identical burst-suppression patterns were compared for quantified EEG characteristics and clinical outcome. Cross correlation of burstshape was applied to the first 500 ms of each burst.

Results

Of 9701 EEGs, 240 showed burst-suppression, 22 with identical bursts. Identical bursts were observed in twenty (20%) of 101 comatose patients after cardiac arrest between a median of 12 and 36 h after the arrest, but not in the six patients with other pathology than cerebral ischemia, or the 183 with anesthesia induced burst suppression. Inter-observer agreement was 0.8 and disagreement always resulted from sampling error. Burst-suppression with identical bursts was always bilateral synchronous, amplitudes were higher (128 vs. 25 μV, p = 0.0001) and correlation coefficients of burstshapes were higher (95% >0.75 vs. 0% >0.75, p < 0.0001) than in burst-suppression without identical bursts. All twenty patients with identical bursts after cardiac arrest had a poor outcome versus 10 (36%) without identical bursts.

Conclusion

“Burst-suppression with identical bursts” is a distinct pathological EEG pattern, which in this series only occurred after diffuse cerebral ischemia and was invariably associated with poor outcome.

Significance

In comatose patients after cardiac arrest, “burst-suppression with identical bursts” predicts a poor outcome with a high specificity.

Introduction

Burst-suppression in the electroencephalogram (EEG) is characterized by high amplitude events (bursts) alternated by periods of low or absent activity (suppressions) (Niedermeijer and Lopes da Silva, 1999, Steriade et al., 1994). This pattern can be physiological, for instance during early development, or pathological, for example in almost half of comatose patients within the first 48 h after cardiac arrest (Cloostermans et al., 2012). Also, burst-suppression can be induced by anesthetics (Yoon et al., 2012). Under pathological conditions, it is usually associated with a poor prognosis. However, in a previous prospective cohort study, we found that 18% of patients with burst-suppression at 12 or 24 h after cardiac arrest had a good functional outcome (Cloostermans et al., 2012).

Characteristics to classify burst-suppression patterns into subgroups with presumed differences in clinical significance include the duration of the bursts and interburst intervals, maximum peak to peak voltage, area under the curve, and the ratio of power in high versus low frequencies (Akrawi et al., 1996). For example, longer suppressions were associated with poorer recovery in patients with postanoxic coma (Wennervirta et al., 2009). Still, predictive values for poor outcome remain too low to allow treatment decisions.

Extreme similarity of burstshape is a distinct feature of some burst-suppression patterns. Herewith, subsequent bursts in a particular channel are almost “photographic” copies. Patterns with this particular characteristic have been sporadically reported and considered a rarity (Hughes, 1986, van Putten and van Putten, 2010). However, through standard use of continuous EEG in comatose patients on the intensive care, we have learned that these occur relatively frequent within the first days after acute diffuse cerebral ischemia.

Here we report on the incidence and prognostic significance of “burst-suppression with identical bursts” and quantify its EEG characteristics. We show that this is a distinct pathological EEG pattern that only occurs after diffuse cerebral ischemia and is invariably associated with a poor outcome in these patients. Since both morphology and clinical significance apparently differ from other burst-suppression patterns, we propose to label the pattern as “burst-suppression with identical bursts.” We discuss potential pathophysiological mechanisms.

Section snippets

Burst-suppression EEGs

We identified EEGs with bursts-suppression in two ways. First, we took these from comatose patients after cardiac arrest that were included in a prospective cohort study on the predictive value of continuous EEG on outcome between June 1st 2010 and September 31st 2012. Design, eligibility criteria, and main outcomes of the first 60 patients included in this study have been published previously (Cloostermans et al., 2012). In brief, since June 1st 2010, consecutive adult comatose patients after

Incidence of burst-suppression with identical bursts

From our cohort of 101 comatose patients after cardiac arrest, 48 (48%) had burst-suppression patterns at twelve or 24 h. Twenty (20%) had burst-suppression with identical bursts on visual analysis. Of all other 9600 EEGs in our database, 192 showed burst-suppression. Underlying conditions varied. Two had diffuse cerebral ischemia from other causes than cardiac arrest, both with identical bursts. Burst-suppression with identical bursts was not seen in the six patients with other pathology than

Discussion

We report on a distinct EEG burst-suppression pattern, which we propose to label “burst-suppression with identical bursts.” This pattern was present in twenty percent of our patients after diffuse cerebral ischemia, but was not seen in the six patients with other pathology than cerebral ischemia, or in the 183 patients under anesthesia. In burst-suppression with identical bursts, burstshapes are highly similar and bilateral synchronous. Inter-burst intervals are variable in duration and

Conclusion

Burst-suppression with identical bursts is a distinct pathological EEG pattern that in our series only occurred after diffuse cerebral ischemia. In comatose patients after cardiac arrest, it was invariably associated with poor outcome.

Acknowledgements

The authors thank the Medisch Spectrum Twente’s lab technicians and intensive care physicians for the constructive collaboration. MT-C was financially supported by the Dutch Ministry of Economic Affairs, Agriculture and Innovation, province Overijssel and province Gelderland through the ViP Brain Networks project. Funding sources played no role in the preparation of this manuscript or the decision to submit. The authors report no conflicts of interest.

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