Assessing adrenal status in patients before and immediately after coronary artery bypass graft surgery

Patients with cortisol deficiency poorly tolerate any systemic inflammatory response syndrome (SIRS), and may die if not treated with sufficient exogenous glucocorticoids. Controversy surrounds what constitutes a 'normal' adrenal response in critical illness. This study uses conventional tests for adrenal insufficiency to investigate cortisol status in patients undergoing elective coronary artery bypass surgery, a condition frequently associated with SIRS.

A prospective, observational study.

Thirty patients with impaired left ventricular function (ejection fraction >23% <50%) underwent basal ACTH measurement, and a short cosyntropin test (250 μg, i.v.) 1 week preoperatively, and at +4 h following induction of general anaesthesia. Preoperatively, a 30 min cortisol level post cosyntropin >550 nmol/l was taken as a normal response.

Prior to surgery, all patients had a normal response to cosyntropin. Postoperatively, eight patients (26.7%) did not achieve stimulated cortisol levels >550 nmol/l and the mean peak cortisol postoperatively was lower (1048 vs 730 nmol/l; P<0.001). There was a significant rise in ACTH after surgery (21 vs 184 ng/l; P=0.007) and reduction in Δ-cortisol post cosyntropin (579 vs 229 nmol/l; P<0.001). There was no change in basal cortisol pre- and post-operatively (447 vs 501; P=0.4). All patients underwent routine, uneventful postoperative recovery.

Up to one quarter of patients with a normal cortisol status preoperatively demonstrated a raised ACTH and deficient cortisol response postoperatively. Despite these responses, all patients had uneventful outcomes. These data reinforce the need for caution when interpreting results of endocrine testing following major surgery or in the intensive care environment, and that prognostic value of these results may be of limited use.