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Background Renal dysfunction is related to the poor outcomes of cardiac surgery. Preoperative occult renal dysfunction (PORD) is defined as patients with normal serum creatinine (Scr) but the glomerular filtration rate (GFR) less than 60 ml/min/1.73m2. However, there is no report on prognosis of elderly PORD patients undergoing coronary artery bypass grafting (CABG). This problem deserves further exploration. Methods Totally 1103 patients undergoing CABG with normal Scr and age ≥ 70 years old were enrolled. The estimated GFR (eGFR) of each patient was monitored using the Berlin initiative study formula. The patients were divided by eGFR into PORD group and control group. Propensity score matching was used to adjust preoperative characteristics. Univariate and multivariate analyses were performed to identify risk factors for postoperative acute kidney injury (AKI) and postoperative mortality. The Kaplan-Meier method was applied to estimate survival rates. A multivariate cox regression model was used to analyze the impacts of factors on long-term survival. Results Elderly patients with normal Scr had high PORD proportion (27.65%). The PORD group had significantly higher preoperative Cr (99.20 ± 12.74 vs. 71.57 ± 11.96), postoperative AKI rates (39.13% vs. 17.75%) and postoperative mortality (5.80% vs. 1.81%) compared with control group. PORD was a significant risk factor for postoperative mortality (OR = 11.648) and postoperative AKI (OR = 2.731). PORD was also a significant risk factor for long-term death after CABG (HR = 1.724). Conclusions PORD is a risk factor for postoperative AKI and short- and long-term death in elderly patients undergoing CABG. eGFR shall be used to assess preoperative renal function.

Background Estimated glomerular filtration rate (eGFR) is a recognized and available method for assessing renal functions. Owing to different design purposes and applicable objects, there are different eGFR equations in clinical practice. The aim of this study was to assess the predictive ability of different methods of eGFR for postoperative acute renal injury (AKI) in patients undergoing coronary artery bypass grafting (CABG). Methods Totally 2557 patients undergoing CABG were included. Their perioperative clinical data were collected retrospectively through the hospital information system. The predictive power of the Cockcroft-Gault equation (CG), the Berlin Initiative Study equation (BIS), the chronic kidney disease epidemiology collaboration equation (CKD-EPI), and the full age spectrum equation (FAS) was validated both in the total cohort and in the elderly (≥ 70 years) according to the applicability of each equation. The predictive power of these equations for postoperative AKI was assessed and compared using the receiver’s operating characteristic curve, the Bland-Altman plot, decision curve analysis, the net reclassification index (NRI) and integrated discrimination improvement (IDI). Results Totally 418 (16.35%) patients were diagnosed with post-operative AKI during the hospital stay, but this percentage reached 25.61% in the elderly population. The CG and CKD-EPI equations were suitable for predicting the occurrence of postoperative AKI in the total cohort, and the FAS equation performed the best (area under the curve = 0.757). The BIS, CKD-EPI, and FAS equations performed generally in the elderly population, but were more consistent and again approximately equal in terms of clinical benefit. NRI and IDI showed the FAS equation continued to perform the best in the total cohort. Conclusions The FAS equation can predict the occurrence of postoperative AKI after CABG both in the total cohort and in the elderly population. All of these equations have available predictive power in the elderly population. Clinical trial registration number: ChiCTR2200061191

Background Elderly patients undergoing cardiac operation often suffer various metabolic comorbidities, such as diabetes mellitus (DM) and obesity. The metabolic disorders in these individuals are widely considered to be possible predisposing factors for unfavourable prognosis. This retrospective study was aimed to determine the association of metabolic diseases with the mortality of elderly patients after coronary artery bypass grafting (CABG) and to identify the protective or risk factors related to their short- and long-term survival. Methods Totally 684 patients aged 75 years or above undergoing isolated CABG were evaluated retrospectively. There were two groups depending on the body mass index (BMI): an overweight and obesity group (n = 354) and a normal weight and lean group (n = 330). Propensity score matching (PSM) was performed to adjust baseline clinical characteristics, which reduced confounding bias. The short-term postoperative mortality was tested via logistic regression. Kaplan–Meier and Cox regression analyses were done to compute the overall survival in each group and to identify relevant variables associated with all-cause mortality, respectively. Results The prevalence rates of metabolic comorbidities in the total cohort were: diabetes mellitus (32.5%), overweight or obesity (51.8%) and hypertension (72.8%). The 30-day postoperative mortality was 5.1% and the long-term mortality was 15.25% at a median 46.2-month follow-up (1.0–178.6 months). The 30-day postoperative mortality was relevant to DM, diseased coronary arteries, New York Heart Association class, intra-aortic balloon pump and emergency surgery. The long-term mortality was negatively associated with overweight and obesity. Univariate and multivariate logistic regression recognized DM as an adverse factor related with 30-day postoperative mortality whether before or after PSM. The long-term mortality was not significantly relevant with DM (HR = 0.753, 95% CI 0.402–1.411). Overweight or obesity was not the risk factor of 30-day postoperative mortality (OR = 1.284, 95% CI 0.426–3.868), but was the protective factor of long-term survival (HR = 0.512, 95% CI 0.279–0.939). Conclusions The “obesity paradox” exists regarding the prognosis of individuals aged ≥ 75, which was presented as lower long-term mortality no matter from all cause or cardio-cerebrovascular cause in patients with BMI ≥ 24. Trial registration ChiCTR2200061869 (05/07/2022).