Association between glomerular filtration rate and 1,25-dihydroxyvitamin D in cardiac surgery

Abstract

Background. Renal impairment is a risk factor for poor clinical outcome in cardiac surgical patients and low circulating levels of the vitamin D hormone 1,25-dihydroxyvitamin D (1,25[OH]2D) may contribute to this risk. Methods. We investigated the association between glomerular filtration rate (GFR) and 1,25(OH)2D in 151 heart transplant recipients and 59 other cardiac surgical patients in postoperative week 1 and at postoperative month 1. GFR estimates (eGFR) were calculated from cystatin C (CysC) and serum creatinine (SCr)-based formulas. Results. With both formulas, linear models provided a better fit between eGFR and circulating 1,25(OH)2D than nonlinear models. Nonetheless, the association between 1,25(OH)2D and eGFR in the early postoperative period was stronger with the CysC-based formula (r = 0.560; P <0.001) than with the SCr-based equation (r = 0.386; P <0.001). CysC-eGFR and SCr-eGFR displayed considerably lack of agreement in the early postoperative period, especially in heart transplant recipients. Conclusions. There is a relatively close association between CysC-eGFR and circulating 1,25(OH) 2D in cardiac surgical patients. Data underline the importance of preserved kidney function in cardiac surgery for adequate circulating 1,25(OH)2D levels. The SCr-based formula is probably too imprecise for estimating GFR in the early postoperative period correctly. © 2012 Informa Healthcare.