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Correspondence |

Long-Latency Sensory-Evoked Responses and Prognosis in Cardiac Arrest SurvivorsSensory-Evoked Responses and Prognosis FREE TO VIEW

Alberto Grande-Martín, MD; José Manuel Pardal-Fernández, PhD; Virgilio Córcoles-González, MD
Author and Funding Information

From the Department of Clinical Neurophysiology (Drs Grande-Martín and Pardal-Fernández) and the Department of Critical Care (Dr Córcoles-González), General Hospital of Albacete.

CORRESPONDENCE TO: Alberto Grande-Martín, MD, General Hospital of Albacete, C/Hermanos Falcó, S/N, 02006-Albacete, Spain; e-mail: agrandem@yahoo.es


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FINANCIAL/NONFINANCIAL DISCLOSURES: The authors have reported to CHEST that no potential conflicts of interest exist with any companies/organizations whose products or services may be discussed in this article.

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Chest. 2015;147(6):e228-e229. doi:10.1378/chest.15-0159
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To the Editor:

We read with great interest the recent article published in CHEST (November 2014) by Ben-Hamouda et al.1 Persistent coma after global cerebral ischemia is a serious clinical disorder, and this condition is not rare among patients resuscitated from cardiac arrest. The prospect of neurologic recovery is poor for many patients, and clinicians are often confronted with the question of whether continuing treatment is worthwhile. To answer this question, it is important to know which clinical, neurophysiologic, imaging, and laboratory features determine prognosis. In this robust article, all of them are perfectly exposed, and a multimodal approach is highlighted with the algorithm. The authors have made a significant contribution to current literature.

However, regarding neurophysiologic assessment of these patients, we would like to emphasize that median nerve somatosensory evoked potential can be used to predict not only poor prognosis, based on bilateral absence of early cortical response (N20),2,3 but also awakening, through assessment of long-latency sensory-evoked potentials (N35 and N70),4,5 not mentioned by the authors. In particular, a previous study showed that patients with an N70 peak latency within 130 milliseconds had a good recovery (positive predictive value of 98%).5

As discussed in the article, presence of mismatch negativity in a comatose patient is superior to somatosensory-evoked potential for the prediction of awakening (100% specificity),3 but we do not value it because standard analysis requires the detection of a robust N1 component of the auditory-evoked potential, resulting in exclusions of a high percentage of patients from the final analysis. Thus, in a survivor of cardiac arrest, the presence of N20 with normal amplitude and latency does not mean that the patient will recover consciousness, having a weak prognostic value.2 In this clinical scenario, we also analyze long-latency responses (Fig 1), and if N70 is present and not delayed beyond 130 milliseconds, prediction of awakening is possible with great certainty.

Figure Jump LinkFigure 1 –  A, B, Somatosensory evoked potential from two patients who remained in coma 24 h after cardiac arrest. Stimulus applied to the median nerve left (left column) and right (right column). Vertical line indicates 70 ms. A, Presence of N20 (asterisk) and N70 (arrow); the patient survived and recovered well. B, Presence of N20 (asterisk), but N70 peak is absent (circle); this patient died.Grahic Jump Location

References

Ben-Hamouda N, Taccone FS, Rossetti AO, Oddo M. Contemporary approach to neurologic prognostication of coma after cardiac arrest. Chest. 2014;146(5):1375-1386. [CrossRef] [PubMed]
 
Logi F, Fischer C, Murri L, Mauguière F. The prognostic value of evoked responses from primary somatosensory and auditory cortex in comatose patients. Clin Neurophysiol. 2003;114(9):1615-1627. [CrossRef] [PubMed]
 
Fischer C, Luauté J, Némoz C, Morlet D, Kirkorian G, Mauguière F. Improved prediction of awakening or nonawakening from severe anoxic coma using tree-based classification analysis. Crit Care Med. 2006;34(5):1520-1524. [CrossRef] [PubMed]
 
Cruse D, Norton L, Gofton T, Young GB, Owen AM. Positive prognostication from median-nerve somatosensory evoked cortical potentials. Neurocrit Care. 2014;21(2):238-244. [CrossRef] [PubMed]
 
Madl C, Kramer L, Domanovits H, et al. Improved outcome prediction in unconscious cardiac arrest survivors with sensory evoked potentials compared with clinical assessment. Crit Care Med. 2000;28(3):721-726. [CrossRef] [PubMed]
 

Figures

Figure Jump LinkFigure 1 –  A, B, Somatosensory evoked potential from two patients who remained in coma 24 h after cardiac arrest. Stimulus applied to the median nerve left (left column) and right (right column). Vertical line indicates 70 ms. A, Presence of N20 (asterisk) and N70 (arrow); the patient survived and recovered well. B, Presence of N20 (asterisk), but N70 peak is absent (circle); this patient died.Grahic Jump Location

Tables

References

Ben-Hamouda N, Taccone FS, Rossetti AO, Oddo M. Contemporary approach to neurologic prognostication of coma after cardiac arrest. Chest. 2014;146(5):1375-1386. [CrossRef] [PubMed]
 
Logi F, Fischer C, Murri L, Mauguière F. The prognostic value of evoked responses from primary somatosensory and auditory cortex in comatose patients. Clin Neurophysiol. 2003;114(9):1615-1627. [CrossRef] [PubMed]
 
Fischer C, Luauté J, Némoz C, Morlet D, Kirkorian G, Mauguière F. Improved prediction of awakening or nonawakening from severe anoxic coma using tree-based classification analysis. Crit Care Med. 2006;34(5):1520-1524. [CrossRef] [PubMed]
 
Cruse D, Norton L, Gofton T, Young GB, Owen AM. Positive prognostication from median-nerve somatosensory evoked cortical potentials. Neurocrit Care. 2014;21(2):238-244. [CrossRef] [PubMed]
 
Madl C, Kramer L, Domanovits H, et al. Improved outcome prediction in unconscious cardiac arrest survivors with sensory evoked potentials compared with clinical assessment. Crit Care Med. 2000;28(3):721-726. [CrossRef] [PubMed]
 
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