Resuscitation 85 (2014) e97–e98
Contents lists available at ScienceDirect
Resuscitation journal homepage: www.elsevier.com/locate/resuscitation
Letter to the Editor False positive absent somatosensory evoked potentials in cardiac arrest with therapeutic hypothermia Sir, Somatosensory evoked potentials (SSEPs) are commonly utilized in assessing neurological prognosis in comatose cardiac arrest survivors. Here we present a case that challenges the current AAN practice parameter, which states that SSEPs can be used to assess poor prognosis within 1–3 days after cardiac arrest.1 In fact, it may be prudent to wait a full 3 days post-rewarming before using SSEP for prognostication purposes.
Our case involves a 31-year-old comatose cardiac arrest victim who underwent therapeutic hypothermia, whose SSEP results at 48 h placed him into a poor prognostic category, but who survived to a meaningful neurological outcome. He suffered a ventricular fibrillation arrest followed by pulseless electrical activity. Therapeutic hypothermia was initiated 4 h post-arrest, and 3.5 h after the return of spontaneous circulation. His neurologic examination before the initiation of hypothermia showed unequal, sluggishly reactive pupils and no other brainstem reflexes, and he had no reaction to deep painful stimulation. He was cooled to a target temperature of 32–34 ◦ C for 24 h, paralyzed and sedated per institutional protocol. On neurological examination 72 h post-arrest, he remained comatose with minimal
Fig. 1. Median nerve somatosensory evoked potentials performed at 49 h after cardiac arrest. At 49 h there were no N19/P22 components at greater than 0.1 V. The channel derivations from top to bottom are Cc-Ci, Ci-FZ, C2 spine-FZ, Erb’s Point-FZ, with G2 relative negative causing an upward deflection (Cc and Ci are C3 and C4 electrode locations contralateral and ipsilateral to the side of stimulation). Time calibrations are 5 ms per division. Amplitude calibrations in microvolts per division are 0.7, 0.7, 2.0, 3.0, 0.7, 0.7, 1.5, and 2.0. Calibration bars show an approximate division. http://dx.doi.org/10.1016/j.resuscitation.2014.02.015 0300-9572/© 2014 Elsevier Ireland Ltd. All rights reserved.
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Letter to the Editor / Resuscitation 85 (2014) e97–e98
brainstem reflexes. He was flaccid with no movement to noxious stimuli. Somatosensory evoked potential testing using needle stimulation of the median nerve at the wrist was performed 49 h post-arrest and 20 h after the cessation of cooling, revealing the bilateral absence of cortical (N20) peaks (Fig. 1). Based on this and the above clinical information, it was predicted that the patient would most likely have a poor neurological outcome. His family wished to pursue aggressive measures, however, and over the ensuing days the patient gradually regained neurological function. Prior to discharge to a rehabilitation facility on day 22, he was alert, fully oriented, had dysarthric but fluent speech, and could ambulate with a walker. The 2006 AAN practice parameter recommendation was based on 8 studies which showed high accuracy and reliability of bilaterally absent thalamocortical (N20) responses for predicting poor outcome after cardiac arrest, with extremely low false positive rates.1 However, the majority of data behind the AAN guidelines were from patients who did not undergo therapeutic hypothermia, now standard of care in many centers for patients following cardiac arrest. More recently, studies have focused on SSEP in patients who underwent therapeutic hypothermia. The predictive value of SSEP in cardiac arrest patients post-hypothermia appears to be highly accurate, with a low false positive rate comparable to that in patients not treated with hypothermia. A meta-analysis of cardiac arrest patients after therapeutic hypothermia found that only 1 of 152 patients with a bilaterally absent SSEP at 72 h post arrest survived to have a good neurologic outcome.2 One further patient with minimally detectable SSEP was reported to have recovered neurologic function.3 SSEP remains a highly accurate tool to assess neurologic prognosis after therapeutic hypothermia. However, in a patient who undergoes 24 h of cooling, a minimum of 72 h should pass before assessment is employed.
Funding This research received no specific grant from any funding agency in the public, commercial or not-for-profit sectors. Conflict of interest statement There are no conflict or competing interests. References 1. Wijdicks EF, Hijdra A, Young GB, Bassetti CL, Wiebe S. Practice parameter: prediction of outcome in comatose survivors after cardiopulmonary resuscitation (an evidence-based review): report of the Quality Standards Subcommittee of the American Academy of Neurology. Neurology 2006;67:203–10. 2. Kamps MJ, Horn J, Oddo M, et al. Prognostication of neurologic outcome in cardiac arrest patients after mild therapeutic hypothermia: a meta-analysis of the current literature. Intensive Care Med 2013;39:1671–82. 3. Leithner C, Ploner CJ, Hasper D, Storm C. Does hypothermia influence the predictive value of bilateral absent N20 after cardiac arrest? Neurology 2010;74:965–9.
Allison E. Arch Department of Neurology, Yale University School of Medicine, New Haven, CT, USA Keith Chiappa Department of Neurology, King Edward VII Memorial Hospital, Hamilton, Bermuda David M. Greer ∗ Department of Neurology, Yale University School of Medicine, New Haven, CT, USA ∗ Corresponding
author at: LLCI 912, Department of Neurology, Yale University School of Medicine, 15 York Street, New Haven, CT 06520, USA. E-mail addresses: [email protected] (A.E. Arch), [email protected] (D.M. Greer).
Disclaimer
19 February 2014
The views expressed in this article are our own and do not represent the official position of our institution.
20 February 2014
Contents lists available at ScienceDirect
Resuscitation journal homepage: www.elsevier.com/locate/resuscitation
Letter to the Editor False positive absent somatosensory evoked potentials in cardiac arrest with therapeutic hypothermia Sir, Somatosensory evoked potentials (SSEPs) are commonly utilized in assessing neurological prognosis in comatose cardiac arrest survivors. Here we present a case that challenges the current AAN practice parameter, which states that SSEPs can be used to assess poor prognosis within 1–3 days after cardiac arrest.1 In fact, it may be prudent to wait a full 3 days post-rewarming before using SSEP for prognostication purposes.
Our case involves a 31-year-old comatose cardiac arrest victim who underwent therapeutic hypothermia, whose SSEP results at 48 h placed him into a poor prognostic category, but who survived to a meaningful neurological outcome. He suffered a ventricular fibrillation arrest followed by pulseless electrical activity. Therapeutic hypothermia was initiated 4 h post-arrest, and 3.5 h after the return of spontaneous circulation. His neurologic examination before the initiation of hypothermia showed unequal, sluggishly reactive pupils and no other brainstem reflexes, and he had no reaction to deep painful stimulation. He was cooled to a target temperature of 32–34 ◦ C for 24 h, paralyzed and sedated per institutional protocol. On neurological examination 72 h post-arrest, he remained comatose with minimal
Fig. 1. Median nerve somatosensory evoked potentials performed at 49 h after cardiac arrest. At 49 h there were no N19/P22 components at greater than 0.1 V. The channel derivations from top to bottom are Cc-Ci, Ci-FZ, C2 spine-FZ, Erb’s Point-FZ, with G2 relative negative causing an upward deflection (Cc and Ci are C3 and C4 electrode locations contralateral and ipsilateral to the side of stimulation). Time calibrations are 5 ms per division. Amplitude calibrations in microvolts per division are 0.7, 0.7, 2.0, 3.0, 0.7, 0.7, 1.5, and 2.0. Calibration bars show an approximate division. http://dx.doi.org/10.1016/j.resuscitation.2014.02.015 0300-9572/© 2014 Elsevier Ireland Ltd. All rights reserved.
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Letter to the Editor / Resuscitation 85 (2014) e97–e98
brainstem reflexes. He was flaccid with no movement to noxious stimuli. Somatosensory evoked potential testing using needle stimulation of the median nerve at the wrist was performed 49 h post-arrest and 20 h after the cessation of cooling, revealing the bilateral absence of cortical (N20) peaks (Fig. 1). Based on this and the above clinical information, it was predicted that the patient would most likely have a poor neurological outcome. His family wished to pursue aggressive measures, however, and over the ensuing days the patient gradually regained neurological function. Prior to discharge to a rehabilitation facility on day 22, he was alert, fully oriented, had dysarthric but fluent speech, and could ambulate with a walker. The 2006 AAN practice parameter recommendation was based on 8 studies which showed high accuracy and reliability of bilaterally absent thalamocortical (N20) responses for predicting poor outcome after cardiac arrest, with extremely low false positive rates.1 However, the majority of data behind the AAN guidelines were from patients who did not undergo therapeutic hypothermia, now standard of care in many centers for patients following cardiac arrest. More recently, studies have focused on SSEP in patients who underwent therapeutic hypothermia. The predictive value of SSEP in cardiac arrest patients post-hypothermia appears to be highly accurate, with a low false positive rate comparable to that in patients not treated with hypothermia. A meta-analysis of cardiac arrest patients after therapeutic hypothermia found that only 1 of 152 patients with a bilaterally absent SSEP at 72 h post arrest survived to have a good neurologic outcome.2 One further patient with minimally detectable SSEP was reported to have recovered neurologic function.3 SSEP remains a highly accurate tool to assess neurologic prognosis after therapeutic hypothermia. However, in a patient who undergoes 24 h of cooling, a minimum of 72 h should pass before assessment is employed.
Funding This research received no specific grant from any funding agency in the public, commercial or not-for-profit sectors. Conflict of interest statement There are no conflict or competing interests. References 1. Wijdicks EF, Hijdra A, Young GB, Bassetti CL, Wiebe S. Practice parameter: prediction of outcome in comatose survivors after cardiopulmonary resuscitation (an evidence-based review): report of the Quality Standards Subcommittee of the American Academy of Neurology. Neurology 2006;67:203–10. 2. Kamps MJ, Horn J, Oddo M, et al. Prognostication of neurologic outcome in cardiac arrest patients after mild therapeutic hypothermia: a meta-analysis of the current literature. Intensive Care Med 2013;39:1671–82. 3. Leithner C, Ploner CJ, Hasper D, Storm C. Does hypothermia influence the predictive value of bilateral absent N20 after cardiac arrest? Neurology 2010;74:965–9.
Allison E. Arch Department of Neurology, Yale University School of Medicine, New Haven, CT, USA Keith Chiappa Department of Neurology, King Edward VII Memorial Hospital, Hamilton, Bermuda David M. Greer ∗ Department of Neurology, Yale University School of Medicine, New Haven, CT, USA ∗ Corresponding
author at: LLCI 912, Department of Neurology, Yale University School of Medicine, 15 York Street, New Haven, CT 06520, USA. E-mail addresses: [email protected] (A.E. Arch), [email protected] (D.M. Greer).
Disclaimer
19 February 2014
The views expressed in this article are our own and do not represent the official position of our institution.
20 February 2014
