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

AbstractOBJECTIVE:
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 >or=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.
AuthorsJai Madhok, Anil Maybhate, Wei Xiong, Matthew A Koenig, Romergryko G Geocadin, Xiaofeng Jia, Nitish V Thakor
JournalCritical care medicine (Crit Care Med) Vol. 38 Issue 8 Pg. 1709-17 (Aug 2010) ISSN: 1530-0293 [Electronic] United States
PMID20526197 (Publication Type: Comparative Study, Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't)
Topics
  • Analysis of Variance
  • Animals
  • Asphyxia (complications)
  • Blood Gas Analysis
  • Disease Models, Animal
  • Evaluation Studies as Topic
  • Evoked Potentials, Somatosensory
  • Heart Arrest (diagnosis, etiology, physiopathology)
  • Male
  • Neurologic Examination
  • Prognosis
  • ROC Curve
  • Random Allocation
  • Rats
  • Rats, Wistar
  • Risk Assessment
  • Statistics, Nonparametric
  • Survival Rate

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