Circadian Rhythm of Cortisol is Altered in Postsurgical Patients*

Abstract

Although the existence of a circadian periodicity of plasma corticosteroid levels is well documented in man, few studies have been performed in surgical patients relating alterations in the circadian rhythmicity of adrenocortical function to surgical procedures. The present study used frequent sampling techniques to examine the effects of varying types of surgery on the secretory pattern of adrenocorticosteroids. In 10 patients, 36–65 yr old, blood was drawn from a superficial vein every 20 min for 2 24-h periods: 1 beginning 48 h before surgery, the other beginning 48 h after surgery. Patients were divided into 2 groups according to the degree of severity of their surgery: a low trauma group not requiring laparotomy (n = 4), and a high trauma group which required laparotomy (n = 6). Cortisol was measured by RIA, and computer analysis revealed a postoperative rise in plasma cortisol levels which persisted from 48–72 h after surgery and could be significantly correlated with the severity of surgery. The episodic nature of cortisol secretion was unaffected by surgery. However, surgical procedures caused phase shifting in the circadian rhythms of plasma cortisol which were significant only in the high trauma group. We conclude the following. 1) The magnitude of the postsurgical rise in plasma cortisol is positively correlated with the severity of surgery. However, contrary to many previous reports, elevated levels of cortisol persisted up to 2–3 days after surgery. 2) The episodic nature of cortisol secretion is an intrinsic characteristic of the secretory mechanism which persists during and after surgical stress even in the face of increased overall adrenocortical activity. 3) Circadian cortisol rhythms are sustained after surgery but are shifted in time proportionately to the magnitude of surgical trauma. These studies establish a relationship between the circadian rhythmicity of adrenal corticoids and the magnitude of surgical trauma which may provide insight into the postoperative management of surgical patients.