To investigate the effect of subcryogenic therapy on rabbit cerebral ischemia and reperfusion injury and secondary cerebral edema after cardiopulmonary resuscitation.

A rabbit cardiac arrest model was established, and then 40 rabbits recovering the autonomous cycle were divided into a normal temperature group and a sub-low temperature group, with 20 rabbits in each group. After resuscitation for 72 h, 18 surviving rabbits in each group were evaluated according to the brain neurological function rating scale. The left side of brain tissue was cut open to make pathological sections. The expression levels of matrix metalloproteinase-9 (MMP-9) and neuron-specific enolase (NSE) in the left cerebral tissue of rabbits were determined by immunohistochemical staining. The heart rate, mean arterial pressure and oxygen saturation before cardiac arrest (T0), after successful cardiopulmonary resuscitation(0 h after cardiopulmonary resuscitation, T1), after reaching the target body temperature of mild hypothermia (2 h after cardiopulmonary resuscitation, T2), before rewarming (14 h after cardiopulmonary resuscitation, T3) and after returning to normal temperature (24 h after cardiopulmonary resuscitation, T4) were compared between these two groups.

There was a significant difference in the heart rate between the normal temperature group and sub-low temperature group at T0, T1, T2, T3 and T4 time points (F = 13.155, P = 0.001). The heart rates at T2 [(185 ± 14) beats/min vs. (209 ± 8) beats/min] and T3 [(182 ± 12) beats/min vs. (205 ± 8) beats/min] time points in the sub-low temperature group were significantly lower than those at the same time point in the normal temperature group (both P < 0.05). After 72 h of cardiopulmonary resuscitation, the neurological deficit score [(35 ± 23) vs. (56 ± 28)] and the positive area of MMP-9 [(1 603 ± 573) μm² vs. (3 633 ± 1 571) μm²] and NSE [(2 075 ± 564) μm² vs. (3 532 ± 988) μm²] in the sub-low temperature group were significantly lower than those in the normal temperature group (t = 2.398, 4.498, 4.697; P = 0.022, 0.001, 0.001).

Subcryogenic therapy can decrease the expression of MMP-9 and NSE in the brain tissue of rabbits after cardiopulmonary resuscitation and promote the recovery of brain function.