Urinary free cortisol values in children under stress.

Children with adrenocortical insufficiency are commonly instructed to increase their baseline glucocorticoid replacement doses by three to five times during periods of stress such as surgery or febrille illness. We conducted this to determine whether these recommendations reflect the actual change in urinary free cortisol (UFC) output during stress. The 24-hour UFC excretion was determined in 78 children who were admitted to a general pediatric department or intensive care unit with temperature > 38.7 degrees C, after major surgery, or during status epilepticus; we reevaluated 43 of the patients 2 weeks after recovery. In addition, the 24-hour UFC levels were determined in 127 healthy children aged 1.8 to 17 years. The UFC level positively correlated with age (r = 0.254; p < 0.001). The amount of UFC per gram of creatinine was inversely correlated with age (r = 0.255; p < 0.001). The amount of UFC per surface area was independent of age. The mean change in the level of UFC per square meter surface area was highest among children who had cardiothoracic surgery and those with multiple trauma. The increase in UFC level during bacterial infection was significantly greater than that during viral infection. The current recommendation to increase the dose to three to five times the baseline glucocorticoid dose during times of stress may underestimate the changes in UFC found in some patients with major surgery, trauma, or certain serious bacterial infections. Production rate studies are needed to prove this point.