Establishment and standardized modeling of lethal shock rat models in high-altitude, high-cold, and high-heat environments

Abstract Objective To establish lethal shock models in high-altitude, high-cold, and high-heat environments based on the conventional environment hemorrhagic shock (HS) model established in our laboratory, in order to provide animal models for lethal shock treatment in special environments. Methods A total of 864 SPF-grade male SD rats (12 weeks old, weighing 200±20 g) were divided into high-altitude environment group (simulated 4 000 m altitude in a low-pressure oxygen chamber, exposed to 22±2 ℃ for 48 h), high-cold environment group (altitude 200 to 300 m, exposure to -20 ℃ for 6 h), high-heat environment group (altitude 200 to 300 m, exposure to 35 ℃ for 12 h), and conventional environment control group (no environmental pretreatment) according to different environmental pretreatment, with 216 animals in each group. After environmental pre-conditioning, 4 types of spleen injury methods were used to induce free intra-abdominal bleeding to construct corresponding uncontrolled HS model. The injury methods were as follows: ① Transverse transection at 3 cm away from the end of the splenic parenchyma; ② Transverse transection separately at 3 and 5 cm away from the end of the splenic parenchyma; ③ Transverse arteriotomy of a small arterial branch at the splenic tail; ④ Transverse arteriotomy of a small arterial branch at the splenic tail combined with transection at 3 cm away from the end of the splenic parenchyma. Free intra-abdominal bleeding was induced by above 4 methods until the mean arterial pressure (MAP) dropped to 40 mmHg, which was defined as successful establishment of the uncontrolled HS model. After successful modeling, lactated Ringer’s (LR) solution was employed to maintain MAP at 50 to 60 mmHg at low pressure for 1 h. After the splenic artery was ligated for complete hemostasis, definitive resuscitation was obtained with LR solution of 2×blood loss volume. MAP, respiratory rate (RR) and heart rate (HR) were monitored, cardiac function [troponin I (TnI)], liver function [aspartate aminotransferase （AST）， alanine aminotransferase（ALT）］、and renal function ［blood urea nitrogen （BUN）， serum creatinine （Scr）］ were evaluated, survival time was observed, and 6-hour survival rate was calculated to screeen the appropriate modeling methods for each environment. Then the obtained modeling methods were applied on Bama pigs to establish HS models for high-altitude, high-cold, and high-heat environments, respectively. After modelling, the pigs were resuscitated according to the aforementioned treatment regimens, and basic physiological indicators (MAP, RR, HR), organ functions (heart, liver, kidney), and survival status were observed to verify the stability of the modeling methods. Results There were differences in the appropriate modeling methods for different environments: the conventional environment preferred method ④, the high-altitude environment preferred method ③, the high-cold environment preferred method ①, and the high-heat environment preferred method ②. All the above methods met the model standards of a 6-hour mortality rate >70% after shock, a blood loss >50% after low-pressure resuscitation, and a survival rate >50% after definitive resuscitation. In the state of shock, the MAP of rats was significantly reduced in each group (P