title: Improving neurological outcomes post-cardiac arrest in a rat model: immediate hypothermia and quantitative EEG monitoring.
abstract: OBJECTIVE
  Therapeutic hypothermia (TH) after cardiac arrest (CA) improves outcomes in a fraction of patients. To enhance the administration of TH, we studied brain electrophysiological monitoring in determining the benefit of early initiation of TH compared to conventional administration in a rat model.
  
  
  METHODS
  Using an asphyxial CA model, we compared the benefit of immediate hypothermia (IH, T=33 degrees C, immediately post-resuscitation, maintained 6h) to conventional hypothermia (CH, T=33 degrees C, starting 1h post-resuscitation, maintained 12h) via surface cooling. We tracked quantitative EEG using relative entropy (qEEG) with outcome verification by serial Neurological Deficit Score (NDS) and quantitative brain histopathological damage scoring (HDS). Thirty-two rats were divided into 4 groups based on CH/IH and 7/9-min duration of asphyxial CA. Four sham rats were included for evaluation of the effect of hypothermia on qEEG.
  
  
  RESULTS
  The 72-h NDS of the IH group was significantly better than the CH group for both 7-min (74/63; median, IH/CH, p<0.001) and 9-min (54/47, p=0.022) groups. qEEG showed greater recovery with IH (p<0.001) and significantly less neuronal cortical injury by HDS (IH: 18.9+/-2.5% versus CH: 33.2+/-4.4%, p=0.006). The 1-h post-resuscitation qEEG correlated well with 72-h NDS (p<0.05) and 72-h behavioral subgroup of NDS (p<0.01). No differences in qEEG were noted in the sham group.
  
  
  CONCLUSIONS
  Immediate but shorter hypothermia compared to CH leads to better functional outcome in rats after 7- and 9-min CA. The beneficial effect of IH was readily detected by neuro-electrophysiological monitoring and histological changes supported the value of this observation.
authors.affiliation: Department of Biomedical Engineering, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA. xjia1@jhmi.edu
authors.forename: Xiaofeng
authors.initials: X
authors.lastname: Jia
authors.forename: Matthew A
authors.initials: MA
authors.lastname: Koenig
authors.forename: Hyun-Chool
authors.initials: HC
authors.lastname: Shin
authors.forename: Gehua
authors.initials: G
authors.lastname: Zhen
authors.forename: Carlos A
authors.initials: CA
authors.lastname: Pardo
authors.forename: Daniel F
authors.initials: DF
authors.lastname: Hanley
authors.forename: Nitish V
authors.initials: NV
authors.lastname: Thakor
authors.forename: Romergryko G
authors.initials: RG
authors.lastname: Geocadin
mesh_terms: D000818:Animals; D002545:Brain Ischemia / Q000473:pathology* / Q000517:prevention & control; D016887:Cardiopulmonary Resuscitation; D004569:Electroencephalography; D006324:Heart Arrest, Induced; D007036:Hypothermia, Induced; D008297:Male; D023421:Models, Animal; D009474:Neurons / Q000473:pathology; D011897:Random Allocation; D051381:Rats; D017208:Rats, Wistar; D020127:Recovery of Function; D013997:Time Factors