Experimental research of cerebral protective effect of mild hypothermia by semiconductor cooling device on the liver surface in rabbits after cardiac arrest / 中华危重病急救医学

ABSTRACT

Objective To observe the cerebral protective effect of mild hypothermia by semiconductor cooling device on the liver surface in rabbits after cardiac arrest (CA). Methods Eighteen healthy male New Zealand white rabbits were randomly and equally divided into CA control group, ice saline group and semiconductor group. CA was induced by rapid intravenous injection of potassium chloride. Five minutes after onset of CA, CPR was initiated. Compared to the control group, which was not treated by hypothermia intervention after CPR, the ice saline group was treated by 4 ℃ ice saline infusion and the semiconductor group was treated by the semiconductor refrigeration piece device cooling on the liver surface for hypothermia intervention after CPR. We recorded the changes of temperature (tympanic temperature and anus temperature), heart rate (HR), mean arterial pressure (MAP) of rabbits in each group, neurological deficit scores (NDS) at 24, 48, 72 hours after the return of spontaneous circulation (ROSC) and the changes of serum neuron specific enolase (NSE) by enzyme linked immunosorbent assay (ELISA). Pathological changes of the hippocampus tissue, liver tissue and skin tissue were obtained by HE staining. Results There was no significant difference in ROSC time in each group. Two rabbits died at 55 hours and 67 hours after ROSC respectively in the control group. The remaining rabbits survived to 72 hours after challenge. There was no significant difference in the overall survival time in groups. Two hypothermia intervention groups had significantly lower level of serum NSE at 24 hours after ROSC and lower DNS scores at 24, 48, 72 hours after ROSC than control group. And the level of serum NSE after 24 hours of ROSC in the semiconductor group were significantly lower than the ice saline group (μg/L 6.916±1.161 vs. 8.615±1.430, P < 0.05). DNS scores at 24, 48, 72 hours after ROSC in the semiconductor group were all significantly lower than the ice saline group (scores 1.33±0.52 vs. 2.00±0.01, 1.01±0.41 vs. 2.00±0.01, 0.92±0.40 vs. 2.10±0.52 respectively, all P < 0.05). Two hypothermia intervention groups had more minor damage of neuronal cell in hippocampus than the control group. And the semiconductor group had more minor damage than the ice saline group. There were no obvious hepatic and subcutaneous tissue injury through which the semiconductor induced hypothermia was performed at corresponding liver surface skin. Conclusion The hypothermia by semiconductor cooling device on the liver surface is a new safe way of protecting brain tissue after CA, which has better cerebral protective effect than ice saline infusion.