Abstract: BACKGROUND: Due to the small size of severe heatstroke small animal models, there is a limitation to the implementation of blood purification and other clinical interventions, while mostly used large animal models, such as baboon, are expensive. The Bama miniature pig used in this study has good genetic stability, and is similar to the human body in terms of body temperature regulation and cardiovascular response, which is also easy to obtain and has low cost.
OBJECTIVE: To prepare the pig model of severe heatstroke under high temperature and high humidity environment, thereby providing an experimental platform for blood purification and other intervention treatments.
METHODS: Twelve male experimental miniature pigs were randomly divided into two groups (n=6 per group): group A (control) and group B in which a pig model of severe heatstroke was established. The experimental conditions are as follows: group A: temperature 35-37 °C; group B: temperature 44-47 °C; the humidity was (65±5)% in both groups; and the experiment in each group lasted for 4 hours. The autonomic state, conjunctiva and levator ani reflex were recorded in detail. The vital signs of experimental animals were continuously monitored by multi-channel physiological recorder. The whole blood cell count, liver and kidney function, creatine kinase, blood coagulation function and urine routine were detected before and after modeling. After the end of the experiment, the important organs and tissues of the experimental animals were taken for pathological examination. The study protocol was approved by the Medical Ethics Committee of the 83rd Army Hospital of Chinese PLA.
RESULTS AND CONCLUSION: Pigs in the two groups were exposed to different environmental conditions for 4 hours. There were significant changes in autonomous behaviors and vital signs of pigs in group B before and after the experiment, and also in laboratory examination results, including whole blood white blood cells, activated partial thromboplastin time, prothrombin time, blood potassium, creatinine and urea nitrogen, aminotransferase and creatine kinase levels (P < 0.05 or P < 0.01). Pathomorphological observations showed multiple organ injuries. There was no significant abnormality in autonomous behaviors of pigs in group A, and there were slight changes in vital signs and laboratory examination results. To conclude, after being exposed to the constant environment of 44-47 °C and humidity of (65±5)% for 4 hours, the pigs present with significant abnormalities in autonomous behaviors, vital signs and laboratory tests, which can reach the standard of severe heatstroke. The pig model of severe heatstroke has good repeatability, which can meet the needs of blood purification for clinical severe heatstroke.

Key words: severe heatstroke, large animals, multiple organ failure, model, pig, high temperature, high humidity, heat injury