Definition of renal function
The study was an observational province wide cohort study which included 13 cardiac centres in Jiangsu province. Data were collected routinely as part of a province CABG register, the register website is: http://221.226.218.114:10004/Multicenter. The Province-wide CABG Registry system was set in Nanjing First Hospital, the study was approved by the Ethics Committee of Nanjing First Hospital, and patient’s identifiers were removed before analysis. DM was defined as the requirement for dietary modification, oral agents and/or insulin to lower blood glucose concentrations and was accepted as present based on the patient’s history corroborated where possible by the medical records. The estimated glomerular filtration rate (eGFR) was calculated by the abbreviated Modification of Diet in Renal Disease equation:186×(serum creatinine/88.4)−1.154 × (age)−0.203 ×(0.742 if female). AKI was defined and classified according to the criteria proposed by the Acute Kidney Injury Network (AKIN) as AKIN stage 1: increase creatinine × 1.5 from baseline or increase of > 0.3 mg/dL within 48 hours; AKIN stage 2: increase creatinine × 2 from baseline; and AKIN stage 3: increase in creatinine × 3 from baseline or creatinine > 4 mg/dL with an acute increase > 0.5 mg/dL within 48 hours or new-onset of dialysis therapy[13].
Study Population
A standard set of perioperative data was collected prospectively for patients undergoing primary isolated CABG who were enrolled in Jiangsu province CABG register between January 2017 and December 2019.
Patients undergoing a concomitant cardiac surgical procedure, reoperation, urgent or emergent operations,or with incomplete information were excluded. Totally there were 4325 cases up to the standard which were divided into 3 groups: A group(non-DM, n = 3067(70.9%)), B group(DM with oral hypoglycemic agents, n = 706, 16.3%) and C group(DM with insulin treatment, and with or without oral hypoglycemic agents, n = 552, 12.8%).
On-pump CABG was performed via median sternotomy using a membrane oxygenator equipped with an arterial filter, cold blood antegrade cardioplegia under moderate systemic hypothermia (30 to 34 °C). The perfusion pressure during cardiopulmonary bypass(CPB) was maintained within 60–70 mmHg. Off-pump CABG was performed by a suction stabilizer. Good exposure of lateral vessels might be got by using deep pericardial retraction sutures. Visualization was enhanced by using a blower device. Intra-coronary shunt was used routinely.
21 perioperative variables were collected including: age, gender, body mass index(BMI), eGFR, smoking, hypertension, DM and the type of treatment, hyperlipemia, chronic obstructive pulmonary disease(COPD), peripheral vascular disease(PVD), prior cerebro-vascular accident(CVA), myocardial infarction(MI) and percutaneous coronary intervention(PCI), left ventricular ejection fraction(LVEF), number of vessel disease, EuroSCOREⅡ, number of distal anastomosis, the application of left internal mammary artery(LIMA) and radial artery, application of CPB or not and CPB time, the incidence and severity of AKI.
Statistical analysis
Data are represented as the mean ± standard deviation unless otherwise indicated. Categorical variables are represented as frequency distributions and single percentages. Normally distributed continuous variables were compared using a Student t-test, non-normally distributed continuous variables using the Mann-Whitney U test, and categorical variables were compared by χ2 test.
The multivariable analysis was adjusted for age, gender, BMI, eGFR, hypertension, hyperlipemia, COPD, PVD, prior CVA, MI and PCI, LVEF, number of vessel disease, EuroSCOREⅡ, number and type of grafts, CPB and CPB time.
All statistical tests were two-sided. A p-value of less than 0.05 was considered significant. All statistical analysis were done with IBM SPSS Statistics 20.0 or STATA Data analysis and statistical software.