Responses of the Hypothalamic-Pituitary-Adrenal and Renin-Angiotensin Axes and the Sympathetic System During Controlled Surgical and Anesthetic Stress

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Abstract
We studied the responses of plasma CRH, ACTH, cortisol, norepinephrine, epinephrine, and renin activity in 11 patients undergoing parathyroid or thyroid surgery after identical preoperative sedation and during isoflurane (Forane) anesthesia. During surgical exploration, plasma CRH levels [10 ± 2 (±sem) pg/mL] remained at basal (unstimulated) levels, and plasma ACTH (11.5 ± 1.4 pg/mL), cortisol (24 ± 4 μg/dL), and epinephrine (35 ± 10 pg/mL) concentrations remained within their normal morning ranges. The majority of the patients had no evidence of pulsatile ACTH secretion during the operation, but, rather, secreted ACTH and cortisol continuously. There was a small elevation of plasma norepinephrine and PRA which was associated with a small increase in heart rate and decrease in blood pressure. Anesthesia reversal, endotrachial extubation, and the early recovery period were associated with marked mean peak increases in plasma ACTH (173 ± 45 pg/ mL), cortisol (35 ± 6 μg/dL), and epinephrine (220 ± 56 pg/mL) and the return of plasma norepinephrine and PRA to basal levels. All hormones returned to basal levels by the first postoperative day. The data suggest that with modern anesthetic techniques patients undergoing neck surgery had mildly elevated plasma ACTH, cortisol, and epinephrine levels. Glucocorticoid secretion during the operation was maintained primarily by continuous rather than pulsatile ACTH secretion. The immediate postoperative period was associated with profound elevations of plasma ACTH, cortisol, and epinephrine. The major determinant of ACTH, cortisol, and epinephrine secretion was anesthesia reversal and recovery and not surgical trauma.