European Journal of Neurology 2014, 21: 890–893

doi:10.1111/ene.12405

Knowledge about post-anoxic somatosensory evoked potentials present or not? B. Jaegera,*, A. Bouwesb,c,*, J. M. Binnekadeb, A. A. Hilgevoordd,e, J. Hornb and A.-F. van Rootselaara a

Department of Neurology and Clinical Neurophysiology, Academic Medical Centre, Amsterdam; bDepartment of Intensive Care, Academic Medical Centre, Amsterdam; cUniversity of Applied Sciences, Faculty of Health Care, Utrecht; dDepartment of Neurology and Clinical Neurophysiology, Sint Lucas Andreas Hospital, Amsterdam; and eDepartment of Neurology and Clinical Neurophysiology, Zaans Medical Centre, Zaandam, The Netherlands

Keywords:

anoxic, cardiac, coma, critical care, evoked potentials/ somatosensory, prognosis Received 3 December 2013 Accepted 7 February 2014

Background and purpose: Median nerve somatosensory evoked potential (SEP) recordings play an important role in outcome algorithms in comatose patients after cardiopulmonary resuscitation. Knowledge of technical difficulties, clinical implications and uniform interpretation of SEP recordings is crucial. The aim of this study was to evaluate the skills of neurologists to interpret SEP recordings in post-anoxic patients. Methods: Nationwide Dutch clinical neurophysiology examinations from 2007, 2008 and 2011, containing SEP related questions, were analysed. Participants were classified as neurology residents, neurologists with less than 10 years of experience, neurologists with more than 10 years of experience and clinical neurophysiologists. End-points were the knowledge of all participants about SEP recordings per year as well as improvement in knowledge over the years, as reflected by the test scores. Results: A total of 194 participants completed the examination in 2007, 200 in 2008 and 263 in 2011. Between 2007 and 2008, all groups of respondents showed a significant increase in percentage of correct answers to SEP questions. Sixty-six participants completed all three examinations. The SEP score of this group improved in 2008 [75%, interquartile range (IQR) 50–75, P < 0.001] compared with 2007 (38%, IQR 38 50); there was no further improvement in 2011 (69%, IQR 54 77). Conclusion: Continuing education about technical knowledge, possible pitfalls and interpretation of SEP recordings remains of utmost importance.

Introduction Since the publication of the Practice Parameter ‘Prediction of outcome in comatose survivors after cardiopulmonary resuscitation’ of the American Academy of Neurology (AAN) in 2006, median nerve somatosensory evoked potential (SEP) recordings play an important role in prediction of outcome in comatose patients after cardiopulmonary resuscitation (CPR) [1,2]. The bilateral absence of cortical N20 SEP responses in post-anoxic coma has been shown to be a predictor of poor outcome and thus guides decisions Correspondence: A.F. van Rootselaar, Department of Clinical Neurophysiology, Room D2-113, Academic Medical Centre, PO Box 22660, 1100 DD, Amsterdam, The Netherlands (tel.: +31 20 5663600/3842; fax: +31 20 6971438; e-mail: [email protected]). *These authors contributed equally to this work.

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about treatment restrictions [3,4]. The SEP has proved to be a robust measure, with less susceptibility to metabolic changes or sedative drugs compared with other prognosticators, including neurological examination and electroencephalography [5–7]. An important limitation in interpretation of SEP recordings of patients in a post-anoxic coma, however, is the interobserver agreement, which was demonstrated by Zandbergen et al. [8] to be only moderate amongst clinical neurophysiologists. In their study, the main cause of interobserver disagreement was related to noise levels and failure to adhere strictly to the guidelines. In the same study recommendations for practical assessment of SEP are given. The interobserver reliability improves by, for instance, administration of muscle relaxants and turning electric equipment off in order to reduce noise levels 10 years Clinical neurophysiologists

[38–50] [38–50] [25–50] [38–50]

[67–83] [50–67] [50–83] [67–83]

[69–85] [60–77] [54–77] [69–85]

A subgroup of 66 participants completed all three examinations. The percentages of correct answers to SEP questions of this 3-year-participant sample are presented in Fig. 3. The SEP score of this subgroup improved in 2008 (75%, IQR 50–75, P < 0.001) compared with 2007 (38%, IQR 38–50), but there was no further improvement in 2011 (69%, IQR 54–77).

70 60 50 40 30 20 10 0

Discussion Our study suggests that the knowledge about median nerve SEP recordings has increased in the Netherlands in the years following the publication of the AAN guideline in 2006. A significant improvement occurred between 2007 and 2008. Not only the SEP scores on group level but also the scores of the 3-year-participant subgroup improved over the years. This suggests that the improvement of the SEP scores reflects increased knowledge of the participants concerning SEP recordings and interpretation.

2007

2008

2011

Year

Figure 3 Median percentages with their interquartile ranges of correct answers on SEP questions of participants who completed the examination in all 3 years (n = 66): 2007, median 37.5 (IQR 37.5–50); 2008, median 75 (IQR 50–75); 2011, median 69.2 (IQR 53.9–76.9).

A possible explanation of the improvement of the SEP score is education. In addition to the educational sessions organized by the Dutch Society of Clinical © 2014 The Author(s) European Journal of Neurology © 2014 EAN

Knowledge about post-anoxic SEPs

Neurophysiology and literature provided to prepare for the examination, one of the topics of the biannual education sessions of the Dutch Society of Neurology in 2007 was post-anoxic encephalopathy. Half of the neurologists visit the session in spring, before the clinical neurophysiology examination, the other half in autumn. These educational sessions could well have influenced the SEP scores of 2007 and even more the scores of 2008. A second explanation is the increased implementation of median nerve SEP as a prognosticator in comatose patients after cardiac arrest in daily clinical practice [1–3]. A limitation of this study is the retrospective design. However, although the SEP questions were not designed for the purpose of this study, they did cover the full range of knowledge needed to assess SEP recordings correctly. Our conclusions might be limited by the fact that the 2008 examination contained only four SEP related questions, but the improvement in SEP score was still present in 2011. Changes in patient care might affect SEPs recorded in post-anoxic patients. Nowadays, treatment with mild hypothermia (32–34°C) in patients admitted after CPR is part of international guidelines and is widely implemented [2,9,10]. Two studies showed prolonged peripheral and central conduction times of median nerve SEPs in patients during treatment with hypothermia after CPR [11,12]. Furthermore, SEP latencies recorded after rewarming remained longer compared with values available from the standard population [12]. Changes in clinical practice like this warrant further education in SEP recording and interpretation. Knowledge about technical difficulties and clinical importance as well as a uniform interpretation of SEP recordings is crucial as absence of the N20 responses of median nerve SEPs will often lead to decisions about treatment restrictions [3,4]. Although our study demonstrated an improvement in SEP knowledge, one could question if these SEP scores are sufficient considering the role SEPs play in clinical practice nowadays. In our opinion one should aim at a 100% score. Literature on the implementation of guidelines suggests that it takes time and education at regular intervals before knowledge is incorporated in daily clinical practice [13]. Permanent education about technical knowledge, possible pitfalls and interpretation of SEP recordings remains of utmost importance.

Disclosure of conflicts of interest The authors declare no financial or other conflicts of interest. © 2014 The Author(s) European Journal of Neurology © 2014 EAN

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Supporting Information Additional Supporting Information may be found in the online version of this article: Appendix S1. Examples of SEP questions.

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Knowledge about post-anoxic somatosensory evoked potentials--present or not?

Median nerve somatosensory evoked potential (SEP) recordings play an important role in outcome algorithms in comatose patients after cardiopulmonary r...
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