Effects of timing and duration of hypothermia on survival in an experimental gerbil model of global ischaemia

PurposeDespite 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.MethodsSurvival 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.ResultsUnder 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.ConclusionsHypothermia-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.