ALTERATIONS IN HYPOTHALAMIC FUNCTION FOLLOWING THERMAL INJURY

Abstract

Nine burn patients with a mean burn size of 39% (range, 23-65%) and five normal individuals studied in an environmental chamber selected optimal comfort temperature by regulating a bedside temperature control unit. The normal individuals selected 27.8 degrees C plus or minus 0.6 (SE) as the comfort temperature and their mean skin temperature was 33.4 plus or minus 0.6 and core temperature 36.9 plus or minus 0.1 while in this environment. In contrast, the burn patients maintained a higher ambient comfort temperature (mean 30.4 plus or minus 0.7, p less than 0.05 when compared to controls) associated with an elevated core (38.4 plus or minus 0.3, p less than 0.01) and surface temperature (35.2 plus or minus 0.4, p less than 0.05). Human growth hormone response to insulin hypoglycemia and arginine infusion was measured in nine additional burn patients (mean burn size, 52%; range, 23-90%) and five normals. Fasting HGH was significantly elevated (1.7 plus or minus 0.2 ng/ml, n = 18, versus control of 0.9 plus or minus 0.1, n = 10, p less than 0.001), despite fasting hyperglycemia in the burn patients (123 plus or minus 5 mg/100 glycemia in the burn patients (123 plus or minus 5 mg/100 ml versus 91 plus or minus 2, p less than 0.001). HGH response to insulin hypoglycemia was diminished in the burn patients with peak HGH value in patients averaging 12.6 ng/ml compared to 27.8 in the recovered patients and 32.6 in the controls (p less than 0.01). Patients receiving an arginine infusion also demonstrated diminished HGH response following injury. The HGH response to known stimuli returned toward normal with time and recovery in the surviving patients. Alterations in comfort temperature, fasting blood glucose, and glucose-HGH interaction occur following thermal trauma. These changes taken together suggest that metabolic responses to injury may be the consequence of homeostatic readjustment within the hypothalamus.