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NEUROLOGY 2009;73:1457-1461
© 2009 American Academy of Neurology

Somatosensory evoked potentials during mild hypothermia after cardiopulmonary resuscitation

A. Bouwes, MD, J. M. Binnekade, PhD, D. F. Zandstra, MD, PhD, J. H.T.M. Koelman, MD, PhD, I. N. van Schaik, MD, PhD, A. Hijdra, MD, PhD and J. Horn, MD, PhD

From the Departments of Intensive Care (A.B., J.M.B., J.H.), Clinical Neurophysiology (J.H.T.M.K.), and Neurology (A.H.), Academic Medical Center, University of Amsterdam; and Departments of Intensive Care (D.F.Z.) and Neurology (I.N.v.S.), Onze Lieve Vrouwe Gasthuis, Amsterdam, the Netherlands.

Address correspondence and reprint requests to Dr. A. Bouwes, Department of Intensive Care, C3-423, Academic Medical Center, P.O. Box 22660, 1100 DD, Amsterdam, the Netherlands a.bouwes{at}amc.uva.nl

Objective: In patients who remain in a coma after cardiopulmonary resuscitation (CPR), the bilateral absence of cortical N20 responses of median nerve somatosensory evoked potentials (SSEP) 24 hours after admission invariably correlates with a poor neurologic outcome. Nowadays, CPR patients are treated with mild hypothermia, with simultaneously administered sedative drugs, hampering clinical neurologic assessment. We investigated whether SSEP performed during hypothermia can reliably predict a poor neurologic outcome.

Methods: Between July 2006 and April 2008, this multicenter prospective cohort study included adult comatose patients admitted after CPR and treated with induced mild hypothermia (32–34°C). SSEP was performed during hypothermia, and in patients who remained comatose after rewarming, a second SSEP was performed. Neurologic outcome was assessed 30 days after admission with the Glasgow Outcome Scale.

Results: Seventy-seven consecutive patients were included in 2 hospitals. In 13 patients (17%), the cortical N20 response during hypothermia was bilaterally absent. In 9 of these 13 patients in whom SSEP could be repeated during normothermia, the N20 response was also absent, yielding a positive predictive value of 1.00 (95% confidence interval [CI] 0.70–1.00). All 13 patients with absent SSEP during hypothermia had a poor neurologic outcome, yielding a positive predictive value of 1.00 (95% CI 0.77–1.00).

Conclusions: The results of this pilot study show that bilaterally absent cortical N20 responses of median nerve somatosensory evoked potentials performed during mild hypothermia after resuscitation can predict a poor neurologic outcome. We started a larger multicenter prospective cohort study to confirm these results.

Abbreviations: CI = confidence interval; CPR = cardiopulmonary resuscitation; GOS = Glasgow Outcome Scale; SSEP = somatosensory evoked potentials.

Supported by a research grant from The Netherlands Brain Foundation (14F06.48).

Disclosure: Author disclosures are provided at the end of the article.

Received March 28, 2009. Accepted in final form August 4, 2009.