 hypothermia circulatori reflex human total circulatori occlus releas result hemodynam phenomena provid integr cardiovascular reflex includ carotid sinu aortic baroceptor arteriolar vasomotor tone venomotor reactiv baroceptor depress appear moder level cool sympathet vasomotor depress 28 degre depress total abolish level 28 degre critic physiolog level repres limit clinic hypothermia 