title: Near-infrared spectroscopy: a tool to monitor cerebral hemodynamic and metabolic changes after cardiac arrest in rats.
abstract: BACKGROUND
  Cardiac arrest (CA) is associated with poor neurological outcome and is associated with a poor understanding of the cerebral hemodynamic and metabolic changes. The objective of this study was to determine the applicability of near-infrared spectroscopy (NIRS), to observe the changes in cerebral total hemoglobin (T-Hb) reflecting cerebral blood volume, oxygenation state of Hb, oxidized cytochrome oxidase (Cyto-C), and brain water content following CA.
  
  
  METHODS
  Fourteen rats were subjected to normothermic (37.5 degrees C) or hypothermic (34 degrees C) CA induced by 8 min of asphyxiation. Animals were resuscitated with ventilation, cardiopulmonary resuscitation (CPR), and epinephrine (adrenaline). Hypothermia was induced before CA. NIRS was applied to the animal head to measure T-Hb with a wavelength of 808 nm (n = 10) and oxygenated/deoxygenated Hb, Cyto-C, and brain water content with wavelengths of 620-1120 nm (n = 4).
  
  
  RESULTS
  There were no technical difficulties in applying NIRS to the animal, and the signals were strong and consistent. Normothermic CA caused post-resuscitation hyperemia followed by hypoperfusion determined by the level of T-Hb. Hypothermic CA blunted post-resuscitation hyperemia and resulted in more prominent post-resuscitation hypoperfusion. Both, normothermic and hypothermic CA resulted in a sharp decrease in oxygenated Hb and Cyto-C, and the level of oxygenated Hb was higher in hypothermic CA after resuscitation. There was a rapid increase in brain water signals following CA. Hypothermic CA attenuated increased water signals in normothermic CA following resuscitation.
  
  
  CONCLUSIONS
  NIRS can be applied to monitor cerebral blood volume, oxygenation state of Hb, Cyto-C, and water content following CA in rats.
authors.affiliation: Department of Emergency Medicine, Louisiana State University Health Science Center in Shreveport, 1501 Kings Highway, Shreveport, LA 71130, USA. fxiao@lsuhsc.edu
authors.forename: Feng
authors.initials: F
authors.lastname: Xiao
authors.forename: Juan
authors.initials: J
authors.lastname: Rodriguez
authors.forename: Thomas C
authors.initials: TC
authors.lastname: Arnold
authors.forename: Shu
authors.initials: S
authors.lastname: Zhang
authors.forename: Davon
authors.initials: D
authors.lastname: Ferrara
authors.forename: Jennifer
authors.initials: J
authors.lastname: Ewing
authors.forename: J Steven
authors.initials: JS
authors.lastname: Alexander
authors.forename: Donna L
authors.initials: DL
authors.lastname: Carden
authors.forename: Steven A
authors.initials: SA
authors.lastname: Conrad
mesh_terms: D000818:Animals; D001921:Brain / Q000503:physiopathology*; D006323:Heart Arrest / Q000503:physiopathology*; D006439:Hemodynamics; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D019265:Spectroscopy, Near-Infrared