Onk, Oruç Alper; Onk, Didem; Ozcelik, Fatih; Gunay, Murat; Turkmen, Kultigin

Introduction: Acute kidney injury (AKI) is an important complication of cardiac surgery due to its high mortality. The aim of the present study was to detect the factors leading to AKI in patients who underwent coronary artery bypass surgery (CABS) and also to determine the optimal timing for detecting AKI using the biomarker neutrophil gelatinase-associated lipocalin (NGAL). Materials and Methods: The records of 375 patients who underwent CABS were reviewed in this case-control study. Ejection fraction (EF), common carotid artery intima-media thickness (CCA-IMT) and cross-clamp (C-C) time of the patients were recorded. Blood samples were taken from all patients on preoperative day 1 as well as 6, 12, 24, 36, 48 h and 7 days after operation. Biochemical parameters were studied in patients with and without AKI. Results: According to the Risk Injury Failure Loss End Stage criteria, 24 patients had renal risk, 17 had injury and 4 had failure. Postoperative 24-hour serum creatinine levels indicated the risk of renal dysfunction for only 4 patients in the AKI group. CCA-IMT, C-C time, haematocrit (HCT) and preoperative interleukin-6 levels were significantly higher in the AKI group than in the non-AKI group. Postoperative 6- and 12-hour NGAL levels in the AKI group correlated with postoperative 36-hour serum creatinine levels. The optimal cut-off values for postoperative 6- and 12-hour NGAL test were 310 and 283 ng/ml, respectively. The area under the curve was higher in the 12-hour NGAL test (p < 0.0086). Conclusion: The number of stenotic coronary arteries, EF, CCA-IMT and HCT are all important risk factors. Early postoperative NGAL results were highly specific for the early recognition of AKI.

Gulhan, Baris; Turkmen, Kultigin; Aydin, Merve; Gunay, Murat; Cikman, Aytekin; Kara, Murat

Background/Objective: Elevated pulse wave velocity (PWV) and central aortic blood pressures are independent predictors of increased cardiovascular morbidity and mortality in hemodialysis (HD) patients. Oxalic acid is a uremic retention molecule that is extensively studied in the pathogenesis of calcium oxalate stones. Oxalobacter formigenes, a member of the colon microbiota, has important roles in oxalate homeostasis. Data regarding the colonization by and the exact role of O. formigenes in the pathogenesis of oxalic acid metabolism in HD patients are scant. Hence, we aimed to determine the relationship between fecal O. formigenes colonization, serum oxalic acid and hemodynamic parameters in HD patients with regard to the colo-reno-cardiac axis. Methods: Fifty HD patients were enrolled in this study. PWV and central aortic systolic (cASBP) and diastolic blood pressures (cADBP) were measured with a Mobil-O-Graph (I.E.M. GmbH, Stolberg, Germany). Serum oxalic acid levels were assessed by ELISA, and fecal O. formigenes DNA levels were isolated and measured by real-time PCR. Results: Isolation of fecal O. formigenes was found in only 2 HD patients. One of them had 113,609 copies/ml, the other one had 1,056 copies/ml. Serum oxalic acid levels were found to be positively correlated with PWV (r = 0.29, p = 0.03), cASBP (r = 0.33, p = 0.001) and cADBP (r = 0.42, p = 0.002) and negatively correlated with LDL (r = -0.30, p = 0.03). In multivariate linear regression analysis, PWV was independently predicted by oxalic acid, glucose and triglyceride. Conclusions: This is the first study that demonstrates the absence of O. formigenes as well as a relation between serum oxalic acid and cASBP, cADBP and PWV in HD patients. Replacement of O. formigenes with pre- and probiotics might decrease serum oxalic acid levels and improve cardiovascular outcomes in HD patients.