Background: Cortisol is an essential stress hormone and deficient patients suffering a systemic inflammatory response (SIR) will rapidly die if not replaced. However, controversy remains on the definition for a normal adrenal response in critically ill patients. We investigated cortisol status in patients undergoing coronary artery bypass surgery (CABG), surgery frequently associated with a SIR, varying in severity from sub-clinical, to life-threatening.
Methods: A prospective study was performed to analyse tests for adrenal insufficiency pre- and post-operatively. Prior to CABG 30 patients had a basal ACTH and a short Synacthen test (250 μg, i.v). After being weaned off cardiopulmonary bypass, patients were transferred to CICU, and had a post-op ACTH and Synacthen test around 4 h from time of induction. A 30 min cortisol post-Synacthen <550 nmol/l was taken as an abnormal response. Intensive care monitoring parameters were recorded.
|Mean (95% CI)||Pre-op||Post-op||P value|
|Basal cortisol (nmol/l)||447 (385509)||501 (393609)||0.4|
|Peak cortisol post-Synacthen (nmol/l)||1048 (9451151)||730 (632828)||<0.001|
|Δ cortisol post-Synacthen (nmol/l)||579 (504654)||229 (170288)||< 0.001|
|% Change in cortisol (100% * peak-basal cortisol/basal cortisol)||161 (112210)||77 (45107)||0.002|
|ACTH (ng/l)||21 (1626)||184 (72296)||0.007|
|Cortisol/ACTH ratio||24 (2127)||9 (612)||<0.001|
Results: Prior to surgery all patients had a normal response to Synacthen with a peak cortisol >550 nmol/l. In contrast, post-op, eight patients (26.7%) did not obtain stimulated-cortisol levels >550 nmol/l. 11/22 in those with a response to Synacthen >550 nmol/l and 5/8 in those with a response <550 nmol/l needed inotropes with a significant difference in time on inotropes (8.4 vs 21.0 h; P=0.05) and time to extubation (5.6 vs 11.7 h; P<0.001). Notwithstanding, all patients had a good final outcome from surgery.
Interpretation: The results show that up to a quarter of patients with a normal pre-operative ACTH and cortisol response to Synacthen show a raised ACTH and apparent deficient cortisol response post-operatively. In conclusion, caution needs to be taken interpreting endocrine tests post major surgery. Future studies need to focus on the ability of tests to predict outcome from steroid intervention.