Effects of timing and duration of hypothermia on survival in an experimental gerbil model of global ischaemia.
OBJECTIVE
Despite the use of animal models to study post-cardiac-arrest resuscitation, the effects of hypothermia on physiological circulatory parameters are still not fully understood. In this study, using a gerbil model of global ischaemia/reperfusion, we aimed to assess the effects of hypothermia on physiological parameters and evaluated the optimal timing for the induction of hypothermia to achieve a better survival rate.


METHODS
Survival rates at 72 h after reperfusion were evaluated by varying the degree of hypothermia and/or duration of ischaemia, and then examined by varying induction timing and/or extending the duration of ischaemia. Physiological parameters were measured using an intravital microscopy system.


RESULTS
Under normothermic cerebral ischaemia, the survival rate was dramatically decreased by the induction of 15-20 min of ischaemia. Induction of hypothermia significantly improved the survival rate only when it occurred less than 10 min after ischaemic onset. In the hypothermia-treated groups, post-ischaemic hyperperfusion was significantly suppressed, and post-ischaemic vasoconstriction of the pial arteriole was prevented.


CONCLUSIONS
Hypothermia-induced suppression of post-ischaemic hyperperfusion and the prevention of vasoconstriction of the pial arteriole play an important role in improving the survival rate after global ischaemia/reperfusion, but the time window for induction of hypothermia remains relatively narrow.
Department of Traumatology and Acute Critical Medicine, Osaka University Graduate School of Medicine, 2-15 Yamadaoka, Suita, Osaka 565-0871, Japan. kazuo-n@hp-emerg.med.osaka-u.ac.jp
Kazuo
K
Noguchi
Naoya
N
Matsumoto
Tadahiko
T
Shiozaki
Osamu
O
Tasaki
Hiroshi
H
Ogura
Yasuyuki
Y
Kuwagata
Hisashi
H
Sugimoto
Akitoshi
A
Seiyama
D000818:Animals; D016887:Cardiopulmonary Resuscitation / Q000379:methods*; D004195:Disease Models, Animal; D005500:Follow-Up Studies; D005849:Gerbillinae; D006323:Heart Arrest / Q000401:mortality / Q000503:physiopathology / Q000628:therapy*; D007036:Hypothermia, Induced; D007511:Ischemia / Q000401:mortality* / Q000503:physiopathology; D008297:Male; D051381:Rats; D015996:Survival Rate / Q000639:trends; D013997:Time Factors