Quantitative assessment of somatosensory-evoked potentials after cardiac arrest in rats: Prognostication of functional outcomes

Jai Madhok, Anil Maybhate, Wei Xiong, Matthew A. Koenig, Romergryko G. Geocadin, Xiaofeng Jia, Nitish V. Thakor

Research output: Contribution to journalArticle

Abstract

Objective: High incidence of poor neurologic sequelae after resuscitation from cardiac arrest underscores the need for objective electrophysiological markers for assessment and prognosis. This study aims to develop a novel marker based on somatosensory evoked potentials (SSEPs). Normal SSEPs involve thalamocortical circuits suggested to play a role in arousal. Due to the vulnerability of these circuits to hypoxic-ischemic insults, we hypothesize that quantitative SSEP markers may indicate future neurologic status. Design: Laboratory investigation. Setting: University Medical School and Animal Research Facility. Subjects: Sixteen adult male Wistar rats. Interventions: None. Measurements and Main Results: SSEPs were recorded during baseline, during the first 4 hrs, and at 24, 48, and 72 hrs postasphyxia from animals subjected to asphyxia-induced cardiac arrest for 7 or 9 mins (n = 8/group). Functional evaluation was performed using the Neurologic Deficit Score (NDS). For quantitative analysis, the phase space representation of the SSEPs-a plot of the signal vs. its slope-was used to compute the phase space area bounded by the waveforms recorded after injury and recovery. Phase space areas during the first 85-190 mins postasphyxia were significantly different between rats with good (72 hr NDS ≥50) and poor (72 hr NDS <50) outcomes (p =.02). Phase space area not only had a high outcome prediction accuracy (80-93%, p <.05) during 85-190 mins postasphyxia but also offered 78% sensitivity to good outcomes without compromising specificity (83-100%). A very early peak of SSEPs that precedes the primary somatosensory response was found to have a modest correlation with the 72 hr NDS subscores for thalamic and brainstem function (p =.066) and not with sensory-motor function (p =.30). Conclusions: Phase space area, a quantitative measure of the entire SSEP morphology, was shown to robustly track neurologic recovery after cardiac arrest. SSEPs are among the most reliable predictors of poor outcome after cardiac arrest; however, phase space area values early after resuscitation can enhance the ability to prognosticate not only poor but also good long-term neurologic outcomes.

Original languageEnglish (US)
Pages (from-to)1709-1717
Number of pages9
JournalCritical care medicine
Volume38
Issue number8
DOIs
StatePublished - Aug 2010

Keywords

  • cardiac arrest
  • eectrophysiology
  • functional outcomes
  • prognosis
  • quantitative neural monitoring
  • somatosensory evoked potentials

ASJC Scopus subject areas

  • Critical Care and Intensive Care Medicine

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