We have previously described a high incidence of admission hypokalemia in trauma patients at our institution. We subsequently performed a prospective study of 112 trauma patients to examine the possible etiologies of post-traumatic hypokalemia. Trauma patients >or=5 years old were evaluated within 6 h of injury with a variety of studies including catecholamines, cortisol, and insulin levels, with studies repeated 24 to 36 h after admission. No potassium replacement was given during this time. Demographic factors such as age, types of injury, and severity of injuries were collected. We found that the mean age of those with post-traumatic hypokalemia (