Because hypothermia in trauma patients is associated with mortality, body temperature control of trauma patients is emphasized in pre-hospital care. Warmed infusion solutions are therefore recommended for hypothermia prevention. In cases of intravenous infusion at outdoor emergency scenes, we used a pre-warmed infusion bag, but the infusion solution inside the tubing turned cloudy and stopped flowing. Although there was no record of the temperature at that time, it occurred on a very cold day with a minimum temperature of −12.8℃. The infusion might have frozen. As the first step to find measures to prevent temperature decrease of the infusion solution, we conducted a preliminary study to investigate the temperature decrease in infusion solution when used in a cold environment. The findings indicated that the pre-warmed infusion solution cooled rapidly while flowing through the infusion circuit. It cooled almost to air temperature by the time it completed the infusion circuit. Given these preliminary findings, after specifically examining the rapid cooling of the infusion solution in the circuit, we proposed a heating method for use in cold environments. First, we heated the infusion circuit to 50℃, 55℃, and 60℃ to find the temperatures to which the infusion circuit needed to be warmed to prevent a decrease in infusion temperature. Then we examined the heating effects obtained in environmental temperatures of 0℃, −5℃, and −10℃. Heating at 55℃ was sufficient to prevent cooling of the infusion solution at environmental temperatures of 0℃ and −5℃. However, the limited heating area did not prevent a temperature decrease of the infusion solution in extremely cold environments such as −10℃. These heating conditions and their effects can be important knowledge for preventing hypothermia in trauma patients at emergency sites during prehospital care. Additionally, after developing a prototype heating device with power supplied by a mobile battery, we examined the possibility of clinical application in actual emergency sites. Decrease of heater temperature remained an issue with our heating device, but results demonstrated the possibility of warming of the infusion solution. A heating device that prevents cooling of infusion solution in cold environments may be useful for prehospital care at emergency sites and for application to disaster medicine.