Protective effect and mechanism of mild hypothermia on liver injury after cardiopulmonary resuscitation in pigs

Objective: To investigate the effect of mild hypothermia therapy on liver after cardiopulmonary resuscitation. Methods: Thirty-three inbred Chinese Wuzhishan (WZS) minipigs, weighted (28±2) kg, were used to establish a ventricular fibrillation model. And 30 animals survived after cardiopulmonary resuscitation reached basic life support. The surviving animals were randomly divided into two groups: mild hypothermia group (group M, n=15) and conventional treatment group (group C, n=15). All the animals were observed for 24 hours. Blood samples were extracted at baseline, 0.5, 1, 2, 4, 6, 12 and 24 h after successful resuscitation. The concentrations of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were detected at the time points. The enzyme-linked immunosorbent assay (ELISA) was used to detect the concentrations of interleukin-6 (IL-6) and tumour necrosis factor-alpha (TNF-α). The data were compared between the two groups, LSD test was used when the variance was homogeneous, and Tamhane T2 test was used when the variance was uneven. Results: Eleven pigs (73.3%) in the group M and 8(53.3%) in the group C survived at 24 h after successful resuscitation, with no statistically significant difference between the two groups (χ(2)=1.229, P=0.225). After successful resuscitation, the AST, ALT increased in both group but less in M group (all P<0.05). After successful resuscitation, the concentrations of TFN-α and IL-6 in the blood increased in both groups, reached the peak at 4h, and then decreased gradually. The concentrations of TFN-α in group M were lower than those in group C at 0.5, 2, 4 and 6 h after successful resuscitation (t=0.01, 0.01, 0.87, 0.86, all P<0.05). The concentrations of IL-6 in the group M were lower than those in group C at 0.5, 1, 2 and 4 h after successful resuscitation (t=0.23, 0.78, 0.11, 0.80, all P<0.05). Conclusions: After successful resuscitation, the release of inflammatory mediators, such as TNF-α and IL-6, and cell apoptosis may involve in liver ischemia reperfusion injury. After successful resuscitation, the liver undergoes ischemia-reperfusion injury, which may be related to the release of inflammatory mediators such as TNF-α and IL-6. Mild hypothermia therapy can prevent the release of TNF-α, IL-6 to reduce the degree of liver damage after resuscitation.