title: Resuscitation from experimental heatstroke by hyperbaric oxygen therapy.
abstract: OBJECTIVE
  Heatstroke is characterized by hyperthermia, vasoplegic shock, and cerebral ischemia and hypoxia. Hyperbaric oxygen (HBO) has been shown to reduce brain ischemia and behavioral dysfunction during cerebral artery occlusion. The efficacy of HBO therapy for resuscitation from heatstroke remains to be determined in the laboratory.
  
  
  METHODS
  Anesthetized rats were randomized to several groups and administered: 1) no resuscitation (normobaric air) after onset of heatstroke, 2) HBO for 1 hr (100% oxygen at 253 kPa for 1 hr), 3) cyclic HBO intermitted by a 5-min air break for 1 hr of treatment (100% oxygen at 253 kPa), 4) hyperbaric air (air at 253 kPa for 1 hr), 5) normobaric hyperoxia (100% oxygen at 101 kPa for 1 hr), or 6) 8% HBO (hyperbaric 8% oxygen at 253 kPa for 1 hr).
  
  
  METHODS
  Laboratory investigation.
  
  
  METHODS
  Sprague-Dawley rats (300- to 400-g males).
  
  
  METHODS
  Rats were exposed to an ambient temperature of 43 degrees C to induce heatstroke. Their colonic temperature; mean arterial pressure; heart rate; arterial blood levels of pH, Paco2, Pao2, So2%, and tumor necrosis factor-alpha; the cortical levels of ischemic and damage markers, and cortical neuronal damage scores were determined. The moment at which mean arterial pressure began to decrease from peak levels was arbitrarily taken as the onset of heatstroke.
  
  
  RESULTS
  Survival time (interval between onset of heatstroke and animal death) was 19 +/- 1 (n = 10), 131 +/- 18 (n = 14), 159 +/- 28 (n = 13), 72 +/- 14 (n = 10), 68 +/- 12 (n = 10), and 45 +/- 11 (n = 10) mins, respectively, for normobaric air, HBO for 1 hr, cyclic HBO, hyperbaric air, normobaric hyperoxia, and 8% HBO groups. The heatstroke induced arterial hypotension and bradycardia, decreased arterial levels of pH, Pao2, and So2%, increased arterial levels of tumor necrosis factor-alpha, and increased values of cellular ischemia and damage markers. In addition, neuronal damage scores in the cortex were significantly reduced by HBO for 1 hr and cyclic HBO resuscitation.
  
  
  CONCLUSIONS
  We successfully demonstrated that HBO and, to some extent, hyperbaric air, normobaric hyperoxia, or HBO 8% was found beneficial in resuscitating rats with experimental heatstroke. HBO effectively reduced heatstroke-induced arterial hypotension, hypoxia, plasma tumor necrosis factor-alpha overproduction, and cerebral ischemia and damage and improved survival.
authors.affiliation: Institute of Physiology, National Yang-Ming University, Taipei, Taiwan.
authors.forename: Hsin-Mao
authors.initials: HM
authors.lastname: Tsai
authors.forename: Chun-Jin
authors.initials: CJ
authors.lastname: Gao
authors.forename: Wen-Xiong
authors.initials: WX
authors.lastname: Li
authors.forename: Mao-Tsun
authors.initials: MT
authors.lastname: Lin
authors.forename: Ko-Chi
authors.initials: KC
authors.lastname: Niu
mesh_terms: D000818:Animals; D015415:Biomarkers / Q000378:metabolism; D001927:Brain Diseases / Q000175:diagnosis / Q000209:etiology; D004195:Disease Models, Animal; D018698:Glutamic Acid / Q000378:metabolism; D005990:Glycerol / Q000378:metabolism; D018883:Heat Stroke / Q000150:complications / Q000378:metabolism / Q000628:therapy*; D006931:Hyperbaric Oxygenation / Q000379:methods*; D007511:Ischemia / Q000209:etiology / Q000378:metabolism; D019344:Lactic Acid / Q000378:metabolism; D008297:Male; D019289:Pyruvic Acid / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D012016:Reference Values; D012151:Resuscitation / Q000379:methods*; D016019:Survival Analysis; D016896:Treatment Outcome; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
chemical_list: D015415:Biomarkers; D014409:Tumor Necrosis Factor-alpha; D019344:Lactic Acid; D018698:Glutamic Acid; D019289:Pyruvic Acid; D005990:Glycerol