Short paperStratifying comatose postanoxic patients for somatosensory evoked potentials using routine EEG
Introduction
EEG is a commonly used tool to assess brain function in comatose patients resuscitated after a cardiac arrest (CA).1 A classification of benign, malignant and highly malignant EEG patterns have previously been proposed.2 A benign EEG may identify patients with a good prognosis.3
Somatosensory evoked potentials (SSEP) is an important method for predicting poor prognosis.4, 5 If cortical N20-potentials are absent bilaterally the prognosis is poor with specificities close to 100%.4, 6 SSEP is less available compared to EEG1 and its sensitivity to predict a poor outcome is limited.7
A clinically relevant question is whether to perform SSEP in all patients or not. Previous studies have evaluated SSEP in addition to EEG to predict poor outcome.6, 8 One study explored if clinical data and EEG could predict absence of N20-potentials,9 but no study has investigated if a benign EEG can be used to anticipate presence of N20-potentials. The aim of this study was to investigate if a routine EEG can identify patients where SSEP is unnecessary to perform.
Section snippets
Methods
In the Targeted Temperature Management (TTM) Trial, 939 adult comatose patients following an out-of-hospital CA were randomised to two different temperature treatments (33 °C or 36 °C). The trial was granted by the ethics committees in each participating country.10
Consecutive patients at the 36 sites were included in the present study if both EEG and SSEP were performed within 10 days after CA. According to the trial protocol11 a routine EEG was mandatory to be performed in patients still
Patients
161 patients from 15 sites had performed both routine EEGs and SSEP and were included in the present study (Fig. 1). The cohort was divided into three EEG categories, benign (n = 29), malignant (n = 69) or highly malignant (n = 63). Patient characteristics and CA related variables are presented in supplementary tables S1 and S2.
EEG and SSEP results
Table 1 presents the SSEP results in each EEG category. A benign EEG defined as a continuous normal-voltage background and absence of abundant discharges was seen in 29
Discussion
Neurophysiological methods are included in algorithms for prognostication following CA,4, 5 but questions remain regarding their most efficient usage. In this cohort, we showed that all patients with a benign EEG had present N20-potentials. Since a benign EEG can predict presence of N20-potentials we suggest that SSEP does not need to be performed in this subgroup of patients. We base this assumption on the traditional view that present N20-potentials is a poor indicator of a good outcome but
Conclusions
In this cohort, benign EEGs were always associated with present N20-potentials. A routine EEG could therefore be used to identify the patients where SSEP is of limited prognostic use.
Funding source
The Swedish Heart and Lung Association; the Skåne University Hospital Foundations; the Gyllenstierna-Krapperup Foundation; the Segerfalk foundation; the Swedish National Health System (ALF); the County Council of Skåne; the Swedish Society of Medicine; the Koch Foundation, The Swedish Heart-Lung Foundation, AFA Insurance, The Swedish Research Council and Hans-Gabriel and Alice Trolle-Wachtmeister Foundation; all in Sweden. The Tryg Foundation; Denmark. EU programme Interreg IV A.
Statistical analysis
Susann Ullén, statistician at our institution, advised the statistical analysis.
Authors’ contributions
All authors contributed to the conceptualization and methodology of the study. AF and EW performed the formal analysis and wrote the first draft of the manuscript. All authors critically reviewed and accepted the final manuscript.
Disclosures
The authors have no disclosures to report.
Declaration of conflicts of interest
None.
Acknowledgements
We would like to acknowledge the 15 sites that contributed data, site investigators (SI) and the contacts of the EEG-laboratories: Copenhagen University Hospital Rigshospitalet (Christian Hassager SI, Jesper Kjaergaard SI, Michael Wanscher SI, Troels Wesenberg Kjaer EEG), Denmark; Santa Maria degli Angeli Hospital Pordenone (Tommaso Pellis SI), Trieste (Vincenzo Campanile SI), Italy; Centre Hospitalier de Luxembourg (Pascal Stammet SI, Stefan Beyenburg EEG), Luxembourg; Academisch Medisch
References (15)
- et al.
Survey on current practices for neurological prognostication after cardiac arrest
Resuscitation
(2015) - et al.
Highly malignant routine EEG predicts poor prognosis after cardiac arrest in the Target Temperature Management trial
Resuscitation
(2018) - et al.
Target Temperature Management after out-of-hospital cardiac arrest–a randomized, parallel-group, assessor-blinded clinical trial–rationale and design
Am Heart J
(2012) - et al.
Neurological prognostication after cardiac arrest and targeted temperature management 33 degrees C versus 36 degrees C: Results from a randomised controlled clinical trial
Resuscitation
(2015) - et al.
Cortical somatosensory evoked high-frequency (600Hz) oscillations predict absence of severe hypoxic encephalopathy after resuscitation
Clin Neurophysiol
(2016) - et al.
Electroencephalography (EEG) for neurological prognostication after cardiac arrest and targeted temperature management; rationale and study design
BMC Neurol
(2014) - et al.
Part 4: advanced life support: 2015 international consensus on cardiopulmonary resuscitation and emergency cardiovascular care science with treatment recommendations
Circulation
(2015)
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Topography of MR lesions correlates with standardized EEG pattern in early comatose survivors after cardiac arrest
2020, ResuscitationCitation Excerpt :This problem is aggravated by the fact that these modalities are unlikely to be independent since most of them assess the function and/or structure of the central nervous system.1 Positive correlation between prognostic modalities has been demonstrated by others and have included clinical examination and electroencephalography (EEG),11 EEG and somatosensory evoked potentials (SSEP),11,12 EEG and neuron-specific enolase (NSE),13 as well as magnetic resonance imaging (MRI) and NSE.14 One previous study was explicitly designed to compare MR and EEG findings in comatose patients after CA.15