Free Serum Cortisol during the Postoperative Acute Phase Response Determined by Equilibrium Dialysis Liquid Chromatography-Tandem Mass Spectrometry

Abstract

In severely ill patients low concentrations of the corticosteroid binding globulin are typically found; the aim of this study was to quantify directly free bioactive cortisol concentrations in the sera of postoperative cardiosurgical patients. Serum samples of 12 consecutive patients undergoing aortocoronary bypass surgery taken preoperatively and on the postoperative days 1 to 4 were analyzed. Total serum cortisol was quantified using liquid chromatography-tandem mass spectrometry with an on-line sample extraction system and tri-deuterated cortisol as the internal standard, and free serum cortisol was measured after over-night equilibrium dialysis. Whereas on the first postoperative day, the median total serum cortisol concentration was approximately two-fold increased compared to preoperative samples (preoperatively, 245 nmol/l (interquartile range (IQR) 203 -293 nmol/l); first postoperative day, 512 nmol/l (IQR 410 -611 nmol/l)), median dialyzable free cortisol concentration was almost seven-fold increased (preoperatively, 14.2 nmol/l (IQR 10.9 -20.7 nmol/l); first postoperative day, 98.3 nmol/l (IQR 81.3 -134 nmol/l)). On the fourth postoperative day, median free cortisol was still significantly increased compared to baseline sampling (p < 0.05), whereas median total cortisol was not. A median of 5.7% (IQR 5.4 -7.0%) of total cortisol was found as free cortisol on the preoperative day, 21.2% (IQR 18.9 -23.5%) on the first postoperative day and 10.5% (IQR 9.8 -14.0%) on the fourth postoperative day. It is concluded that during the postoperative period the freeto-bound ratio of cortisol is highly variable and that during the acute phase response direct quantification of free bioactive cortisol concentrations seems to be biologically more appropriate than the measurement of total cortisol concentrations. Clin Chem Lab Med 2003; 41(2):146 -151

Free serum cortisol: quantification applying equilibrium dialysis or ultrafiltration and an automated immunoassay system

“…Equilibrium dialysis of serum samples was essentially performed as described previously (17,18,20). For conditioning of dialysis membranes, an approx.…”

“…Furthermore, no automated test for CBG measurement is available, and calculated free serum cortisol incorporates the inaccuracy of two immunometric assays. As a potentially more accurate approach, direct quantification of free serum cortisol after equilibrium dialysis of serum samples may be applied (5,17,18). As applies for equilibrium dialysis, a protein-free fraction can also be obtained from serum samples by ultrafiltration techniques (14,19).…”

HIF1α synergizes with glucocorticoids to promote BFU-E progenitor self-renewal

“…38,39 Importantly, our dose-response curves with the use of Dex, which has a longer half-life and is a Ϸ30-fold more potent GCR agonist than cortisol, 40 are readily converted to physiologic cortisol levels. Although daytime-free cortisol levels normally reach 14-15nM (corresponding to 0.43-0.45nM Dex), levels increase to 98nM (ϳ 3.0nM Dex) after surgery 41 and Յ 120nM (ϳ 3.6nM Dex) during septic shock. 42 Our dose response curves (in the absence of DMOG) show that normal GC concentrations (0.45nM Dex) hardly increase CFU-E formation, whereas a clear effect is seen at GC levels detected during stress (Ͼ 1nM Dex) (Figure 5B-C).…”

Assessing adrenal insufficiency of corticosteroid secretion using free versus total cortisol levels in critical illness

“…A subnormal response to ACTH in critical illness was defined by a total cortisol increase \250 nmol/l or increase\100 nmol/l, as reported by others and ourselves [5,6]. Serum free cortisol levels were measured by equilibrium dialysis of undiluted serum samples followed by radioimmunoassay (Orion Diagnostica, Espoo, Finland; \6% cross reactivity with cortisone) [4,13,16,17,25,26]. The intra-and interassay coefficients of variation were less than 7 and 8%, respectively.…”