SA JOURNAL OF DIABETES & VASCULAR DISEASE RESEARCH ARTICLE VOLUME 20 NUMBER 2 • NOVEMBER 2023 25 weeks after the angiography procedure. Pre-operatively, immediately after cardiac catheterisation, the Nephrology Department was consulted and patients were hydrated under appropriate conditions. Patients did not take any regular nephrotoxic medication before or after the procedure. Basal creatinine concentrationwasmeasuredwithin the following seven days before surgery. After surgery, data were collected daily for seven consecutive days, including serum creatinine concentration and urine output. Urine output was measured at one-hour intervals during the first 72 hours postoperatively while the patient was in the post-operative care unit. The day of surgery was defined as day 0. Patients were assessed for the development of acute kidney injury (AKI) from postoperative day 1 to day 7, based on changes in serum creatinine concentration. Pre-operative creatinine levels, and post-operative day 2 and day 5 creatinine values were compared in groups 1 and 2, taking into account the minimum increase in creatinine concentration within 48 hours and one week, as in the acute kidney injury network (AKIN) and kidney disease improving global outcomes (KDIGO) criteria.8,9 Although the AKIN criterion seems to be more applicable than the KDIGO criterion, as it suggests a shorter time interval for the time of diagnosis, it was planned to look at day 5 creatinine values in addition to day 2 values, as this may underestimate the severity of AKI. Peri-operative outcomes were compared between the groups and post-operative complications were recorded. According to the AKIN classification, AKI was defined as an increase of ≥ 50% or 0.3 mg/dl in the pre-operative baseline creatinine level within 48 hours.9 Post-operative AKI was compared in both groups. All operations were performed on-pump by the same surgical team. There was no difference between coronary revascularisation techniques in the two groups. After releasing the left internal mammary artery, standard cannulation was performed, followed by antegrade cardioplegia cannula placement and CPB was initiated. Moderate hypothermia was maintained, and a roller pump and membrane oxygenator were used during CPB. The perfusion rate was set at 50–75 ml/kg/ min and mean arterial pressure at 60 mmHg and above. Myocardial protection was achieved with intermittent blood cardioplegia and topical cooling, following clamping of the aorta when appropriate conditions were provided. Distal anastomoses were made in crossclamps and proximal anastomoses were made in side clamps. Blood pressure, rhythm, amount of chest tube drainage, urine output, oxygenation profile, state of consciousness and pain control were closely monitored during intensive care unit (ICU) follow up. Mean arterial blood pressure was maintained at 60 mmHg and above by ensuring stable haemodynamics. Urine output was monitored hourly and blood gas, potassium and bicarbonate values were measured intermittently. Fluid support was provided so that urine output was 1 ml/kg/hour and above. The effect of crossclamps, total perfusion time and the number of bypass vessels on the change in postoperative creatinine value were investigated in both groups. Statistical analysis Analysis of the data was done in the IBM SPSS 22.0 (SPSS Inc, Chicago, IL, USA) package program. Descriptive statistics are shown as mean (standard deviation) for normally distributed variables and median (minimum – maximum) for non-normally distributed variables. The differences between the groups were evaluated with the t-test when the assumption of normal distribution was provided, and with the Mann–Whitney U-test when the assumption of normal distribution was not provided. The Spearman correlation test was used since the normality assumption was not provided for the relationship between continuous variables. Pearson’s chi-squared test was employed for intergroup comparison of categorical variables. For p < 0.05, the results were considered statistically significant. No sample calculation was made before the study. All patient records were accessed. Post hoc power analysis was performed with Gpower 3.1. The power was calculated as 0.69 for creatinine on postoperative day 2 and 0.84 for creatinine on postoperative day 5. Results A total of 93 patients with LLVEF ≤ 35% who underwent isolated CABG were analysed. Among these patients, 60 were in the group with DM (group 1) and 33 were in the non-DM group (group 2). The demographic characteristics of the patients are given in Table 1. The pre-operative LLVEF was found to be 32% (2.1) in group 1, and 31% (2.0) in group 2, and no statistically significant differences were found between the groups. There were no differences between the groups in terms of other demographic data. Although the peri-operative data of the patients (cross-clamp time, total perfusion time, number of bypass vessels) were numerically higher in group 1, this did not cause a statistically significant difference (Table 2). When comparing the two groups, no significant differences were found between the pre-operative creatinine values (p = 0.294). The postoperative creatinine values on days 2 and 5 were significantly higher in group 1 compared to group 2 (p = 0.033 and p = 0.005 respectively). Pre- and post-operative data are shown in Table 3. When both groups were evaluated, the post-operative creatinine levels at days 2 and 5 were significantly higher than the preoperative levels in group 1 (p = 0.008 and p = 0.001, respectively) (Fig. 1). Post-operative creatinine levels increased in group 2, but not to a statistically significant level (Table 4). The creatinine level increased above 2.0 mg/dl in two patients in the DM group on the second postoperative day. Since the urinary output was less than 0.5 ml/kg/hour, furosemide was given at a dose of 0.5 mg/hour for 12 hours in one patient and 24 hours in the other in order to provide cardiovascular stability. No patient required haemodialysis in the study groups. Table 1. Demographic characteristics of the groups DM group Non-DM group Demographics (n = 60) n (%) (n = 33) n (%) p-value* Age (years) 67.7 (9.9) 54.6 (6.3) 0.87 Gender Female 33 (55) 19 (57.5) 0.91 Male 27 (45) 14 (42.5) 0.94 Hypertension 18 (30) 10 (30.3) 0.80 BMI 27.0 (3.1) 26.71 (4.3) 0.61 COPD 15 (25) 8 (24.2) 0.44 Smoking 30 (50.0) 17 (51.5) 0.31 Ejection fraction 32 (2.1) 31 (2.0) 0.48 EuroSCORE (mean) 1.8 (0.6) 1.40 (0.4) 0.46 BMI: body mass index; COPD: chronic obstructive pulmonary disease, DM: diabetes mellitus. *Mann–Whitney U-test.
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