Endogenous Ouabain Changes Rapidly During Cardiac Pulmonary by Pass

Objective: Endogenous Ouabain (EO) is a cardiac glycoside secreted from the adrenal glands that plays a role sodium homeostasis with hemodynamic and renal effects. It is considered a stress hormone. The role of EO during critical illness is unknown.  Aim: to study 1. the time course of EO during cardio pulmonary bypass (CPB) and 2. the ability of renal replacement therapy (RRT) to remove EO. Methods: in 11 patients undergoing mitral valve repair were performed an intraoperative time course with serial blood samples for EO, serum creatinine, NT-proBNP and cathecolamines. During surgery blood samples were repeated every 15 minutes. Then all these biomarkers were dosed at the end of surgery, 4 hours and 24 hours later. In the 15 patients undergoing EO time course during RRT, EO plasma levels were measured when AKI (Acute Kidney Injury) occurred (at R of RIFLE and 24 hours after this moment).  Results: In patients undergoing mitral valve repair EO levels increased 15 minutes after the beginning of CPB reaching the peak 4 hours after surgery (from 198±10 to 350±130 pmol/L, p<0.0001). Circulating catecholamine (Norepneephrine ad Epinephrine) levels increased immediately after CBP. NT-proBNP increased only 4 hours after surgery, reaching high plasma levels when EO decreased. Plasma EO and creatinine levels resulted significantly directly related (r=0.45, p=0.01) after surgery. Continuous RRT did not modified circulating EO in AKI patients.   Conclusion: EO may be considered a stress hormone that changes rapidly during acute volume expansion and blood pressure fall during CPB.