Establishment and evaluation of a hypothermia model of Bama mini‐pigs

BACKGROUND: The occurrence of cold injury persists in modern military operations. Frigid weather imposes extreme physiological stresses to animal and human life. OBJECTIVE: To develop a hypothermia model using Bama miniature pigs for biochemical and physiological study of cold injuries. MATERIALS AND METHODS: Twelve Bama mini‐pigs (20 to 25 kg) were allocated to four groups: control, cold exposure alone, cold exposure with strong wind, and cold exposure with intermittent blasts. Pigs were anesthetized using ketamine/sumianxin II (1 mg), supplemented with pentobarbital sodium as needed. Blood samples were collected during progressive hypothermia for the evaluation of biochemical, hematologic and coagulation profiles. Skin manifestations and hypothermia progression were recorded prior to euthanasia and histopathological organ analysis. RESULTS: Hypothermic pigs exhibited progressive decrease in body temperature, leg frostbite, ice formation around the mouth, and other injuries over a period of 8 days. Cold exposure significantly altered the body temperature, blood cell count (excluding platelets), blood biochemistry, coagulation function and thromboelastography of animals as compared to the control group ( P < 0.05). Abnormal swelling of bladders with urinary retention and prominent pericardial effusion were observed upon autopsy examination. Pathological examination from HE-stained slides revealed edema, inflammation, hyperplasia and hemorrhage in vital organs. Cold exposure with strong wind resulted in the most rapid and severe hypothermia (27.27 ± 1.33°C). CONCLUSION: This study evaluated the physiological responses of Bama mini‐pigs under extreme cold stress and demonstrated that Bama mini‐pig is a useful hypothermia model for investigation of cold injuries.