Resuscitation from experimental heatstroke by hyperbaric oxygen therapy.
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.
Tsai
Hsin-Mao
HM
Institute of Physiology, National Yang-Ming University, Taipei, Taiwan.
Gao
Chun-Jin
CJ
Li
Wen-Xiong
WX
Lin
Mao-Tsun
MT
Niu
Ko-Chi
KC
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
D015415:Biomarkers; D014409:Tumor Necrosis Factor-alpha; D019344:Lactic Acid; D018698:Glutamic Acid; D019289:Pyruvic Acid; D005990:Glycerol