The body can only expend so much energy to maintain its temperature. In a deeply compromised state, these normal mechanisms do not work well. Even indoors in a hospital, IV fluids off-the-shelf are typically stored at room temperature 21°C (70°F). This creates an immediate 16°C (28°F) gradient between normal body temperature and the resuscitation fluids. Blood products are stored refrigerated, at 4°C (39°F), which greatly increases the temperature gradient a compromise patient has to overcome.
Resuscitation fluids given to trauma, critically ill, and surgical patients are known to potentially lower body temperature. They are one contributor to hypothermia; combined with shock, blood loss, exposure to evaluate injuries, the external environment, anesthesia, and opening a body cavity for surgical repair.