Clinical PaperBispectral Index to Predict Neurological Outcome Early After Cardiac Arrest☆
Introduction
Successfully resuscitated cardiac arrest remains a condition with a high mortality rate, even when applying the best medical care to the patients.1, 2, 3, 4 This high mortality of about fifty percent of the patients admitted to the hospital after successful pre-hospital resuscitation is mainly due to neurological impairment consecutive to the anoxic period during cardiac arrest and possibly during reperfusion.5, 6 The ability to predict outcome early after cardiac arrest would represent a major breakthrough towards personalized medicine by adapting the treatment strategy individually to the patient. This early prediction would allow avoiding futile healthcare to patients with irreversible neurological damage while maintaining resources in patients most likely to benefit. However, neurological prognostication of comatose patients after successful resuscitation and admission to the intensive care unit (ICU) remains a challenge.7
Several studies have focused on the prognostic value of biomarkers and electrophysiological parameters, but none could demonstrate an accurate prediction of outcome within the first 24 hours after cardiac arrest in hypothermia-treated patients.7, 8, 9, 10 Thus, there is an unmet need for early prediction tools. The actual lapse of time to reliably predict outcome, generally 24, 48 or even 72 hours after cardiac arrest, might be too lengthy if therapeutic decisions on highly invasive acute cardiac assistance have to be taken.11, 12 In previous reports, bispectral index (BIS), a processed electroencephalogram, initially designed to assess the depth of anesthesia, has potential to predict outcome early after cardiac arrest.13, 14, 15, 16, 17 In these studies, either BIS value monitored at a single time-point or the lowest recorded BIS value were considered in prediction analyses.
The aim of this study was to refine the value of BIS as an early predictor of outcome after cardiac arrest. Using serial measurements of BIS over the first 24 hours after admission to the ICU, we determined BIS cut-off values and time of recording providing optimal prediction of outcome.
Section snippets
Patients
We included all successfully resuscitated adult cardiac arrest patients enrolled in a prospective local registry admitted from February 2009 to June 2013 to our general ICU. Part of the patients have been involved in previous studies, although none of these addressed the prognostic value of continuous BIS monitoring.16, 18, 19, 20 All patients were older than 18 years, unconscious (Glasgow coma score below or equal to 8) and received induced hypothermia at 33 °C with sedation and neuromuscular
Patients
Over the four year enrollment period, 121 patients were admitted to our ICU after cardiac arrest. Twenty-five patients had to be excluded (Figure 1). Thus, 96 patients were enrolled in this study. Median time from ROSC to first BIS measurement was 197 [166–246] minutes and time to target temperature was 300 [237–391] minutes. Median doses of midazolam, fentanyl and cisatracurium were respectively: 0.16 [0.12-0.25] mg/kg/h, 1.69 [0.99-2.4] μg/kg/h and 0.11 [0.08-0.12] mg/kg/h. There was no
Discussion
This study supports the hypothesis that continuous monitoring and calculation of mean BIS during the first 24 hours after ICU admission allows an early and accurate prediction of outcome. We determined cut-off values for BIS and duration of monitoring that allow optimal prediction. BIS monitoring had an additive prognostic value to standard clinical parameters.
Patients with good and poor neurological outcome differed in terms of age, time to ROSC, illness severity score (SAPS II) and initial
Conclusions
Calculation of the mean BIS value over the first 12.5 hours after ICU admission might be another potential predictor of neurological outcome after cardiac arrest. Further studies are warranted to confirm and refine these findings.
The data of this paper do not overlap with previous publications and the manuscript, including related data, figures and tables, have not been published previously and the manuscript is not under consideration elsewhere.
Conflicts of interest: None.
Financial support:
Conflict of interest
The authors declare that they have no conflict of interest.
Acknowledgements
We are grateful to Jacqueline Kieffer for her meticulous work for data extraction. We thank Loredana Jacobs, Mélanie Vausort, Christelle Nicolas and Bernadette Leners for technical assistance.
This work was supported by grants from the Ministry of Culture, Higher Education and Research of Luxembourg.
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Cited by (33)
Bispectral index and suppression ratio after cardiac arrest: are they useful as bedside tools for rational treatment escalation plans?
2022, Revista Espanola de CardiologiaThe revised Cerebral Recovery Index improves predictions of neurological outcome after cardiac arrest
2018, Clinical NeurophysiologyThe validation of simplified EEG derived from the bispectral index monitor in post-cardiac arrest patients
2018, ResuscitationCitation Excerpt :Unfortunately, our time point of validation was situated approximately three days after CA. As previous studies showed that the prognostic power of EEG lies within the first 24 h, we acknowledge that the prognostic value of simplified BIS EEG warrants further examination in a similar time window [14,15,35–37]. Aside from experienced neurophysiologists, treating physicians should also be capable of interpreting simplified EEG traces on the BIS monitor as they can play a prominent role in the early identification of epileptic activity.
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A Spanish translated version of the summary of this article appears as Appendix in the final online version at http://dx.doi.org/10.1016/j.resuscitation.2014.09.009.