Circadian Rhythms of Serum Aldosterone, Cortisol and Plasma Renin Activity in Burn Injuries

Circadian rhythm of serum aldosterone and cortisol concentrations and of plasma renin activity (PRA) were measured by radioimmunoassay in 10 adults with thermal injuries. The determinations were begun 6 to 48 hours after the injury and continued for five consecutive days four times a day. In all patients, the normal pattern of the circadian rhythm for all three hormones disappeared and values remained quite high at any time of the day or the night. Four patients developed an hypertensive crisis with quite elevated levels of aldosterone, cortisol and plasma renin activity. The same hormones were also found very elevated in two hypotensive patients with 80 percent or more of injured body surface who were in agonal conditions and succumbed to the injury.