Prolonged alterations in plasma cortisol circadian rhythms following trauma in baboons

Few studies have been performed concerning alterations in the circadian rhythmicity of adrenocortical function following trauma. The present study examined the effects of surgical trauma of varying severity on the secretory pattern of adrenocorticosteroids in the female baboon (Papio anubus). In 30 baboons, blood samples were obtained every hour for three 96-h periods: 1 wk prior to surgery; beginning 30 min following incision closure; and beginning 7 days following surgery. Animals were divided into three groups: anesthesia/surgical controls, low-trauma group [(LT), laparotomy plus 5-min bowel traction], or high-trauma group [(HT), laparotomy plus 20-min bowel traction]. A postoperative rise in plasma cortisol was observed that persisted up to 10 days postsurgery and could be significantly correlated with severity of trauma. The episodic nature of cortisol secretion was unaffected by surgery. The circadian rhythm of cortisol was phase shifted in the LT group and abolished up to 8 days postsurgery in the HT group. We conclude that the magnitude of posttrauma rise and circadian disruption of plasma cortisol is correlated with magnitude of surgical trauma. However, contrary to previous reports, elevated levels of cortisol may persist for an extended time (10 days) following the primary insult.