CARDIOVASCULAR JOURNAL OF AFRICA • Volume 34, No 5, November/December 2023 AFRICA 279 calculations using blood cell analysis and lipid analysis.10 Recent studies have shown that MHR is used as a potential marker to predict mortality and major adverse cardiovascular events in patients with ST-elevation myocardial infarction (STEMI) who underwent primary percutaneous coronary intervention (pPCI).11 Kanbay et al. reported in their study that high MHR was associated with worse cardiovascular profile in predialytic chronic renal failure patients with decreased estimated glomerular filtration rate (eGFR) and that MHR was an independent predictor of major cardiovascular events during follow up.12 Again, Canpolat et al. reported that it was an independent predictor of recurrence of atrial fibrillation (AF) after atrialbased catheter ablation and was significantly associated with the presence of slow coronary flow.13 Lui et al. showed that high MHR levels were associated with poor functional outcomes in patients with acute ischaemic stroke.14 In this study we aimed to investigate the association of pre-operative MHR with early postoperative AKI in isolated CABG surgery. Methods The medical records of a total of 1 404 patients who underwent isolated CABG between June 2014 and June 2022 were reviewed retrospectively. The operations were performed at the same centre by the same surgery team; 954 (67.9%) patients who had serum creatinine (sCr) levels of < 1.5 mg/dl who underwent isolated CABG with CPB were included in the study. The diagnosis of AKI was based on the highest sCr concentration measured during the first seven days after surgery compared with the baseline sCr concentration, defined as the last concentration measured before surgery. Urine output was not used to define AKI, because it might have been altered by diuretics administered during anaesthesia and CPB.7 Patients who developed AKI in the early postoperative period were classified as group 1 (n = 161) and those with normal postoperative renal function were classified as group 2 (n = 793). The diagnosis of AKI was made by comparing the baseline and postoperative sCr to determine the predefined significant change based on the kidney disease improving global outcomes (KDIGO) definition (increase in sCr by ≥ 0.3 mg/dl within 48 hours of surgery or increase in sCr to ≥ 1.5 times baseline within three days of cardiac surgery).15 We excluded patients previously diagnosed with end-stage renal disease who were on dialysis. Also excluded from the study were patients who had peripheral and carotid arterial disease, valvular heart disease, systemic inflammatory diseases, chronic obstructive pulmonary disease, congenital cardiac disease, malignancy, haematological proliferative diseases, autoimmune diseases, endocrinological disorders, immunosuppressive drug treatment within the past two weeks before surgery, advanced age (> 75 years), left ventricular systolic function disorder [left ventricular ejection fraction (LVEF) ≤ 30%], renal impairment (sCr ≥ 1.5 mg/dl), patients with low pre-operative haemoglobin levels (≤ 10 g/dl), the use of steroids or non-steroidal antiinflammatory drugs, the presence of signs of clinical infection [fever 37.5°C, CRP ≥ 5 mg/dl, erythrocyte sedimentation rate (ESR) > 20 mm/h or leukocyte count > 11 000 cells/μl] before surgery, patients who had an acute myocardial infarction and percutaneous coronary intervention in the last 30 days prior to operation, emergency operations, patients who required intra-aortic balloon pump, patients who were re-operated on due to haemodynamic instability or bleeding, patients who were operated on a beating heart or redo CABG. Additionally, patients for whom data such as sCr levels or urine output were missing and patients whose cardiac catheterisations were performed within the last 15 pre-operative days were excluded. The demographic and clinical data of the patients were obtained from the hospital’s software system. Age, gender, smoking (defined as continuous or cumulative smoking for six or more months or at least six months every day; passive smoking refers to non-smokers inhaling the smoke from smokers’ breath for at least 15 minutes per day for more than one day per week), history of statin use, diabetes (including history of diabetes mellitus and newly diagnosed diabetes), hypertension (defined as history of hypertension and newly diagnosed hypertension), dyslipidaemia (defined as low HDL-C and high triglycerides; the cut-off values were selected at HDL-C < 40 mg/dl (1.04 mmol/l) and triglycerides ≥ 200 mg/dl (2.26 mmol/l) in both men and women), LVEF, laboratory parameters (haemoglobin, haematocrit, leukocyte count, thrombocyte count, monocyte count, LDL-C, HDL-C, total cholesterol, triglycerides, serum creatinine, urea and uric acid, eGFR, ESR and CRP), operation information, the number of grafts used, duration of CPB and aortic cross-clamp (ACC), use of blood products and length of stay in the ICU and hospital were recorded. Laboratory examinations, including blood cell counts and lipid profiles, were routinely obtained within 24 hours of fasting upon admission to the hospital. Approximately 5–7 ml venous blood samples were placed pre-operatively into two types of sterile tubes: one with EDTA for blood count and one dry biochemistry tube for biochemical analysis. Haematological parameters were calculated by an automated blood count device (Abbott CELL-DYN 3700; Abbott Laboratory, Abbott Park, Illinois, USA) following a waiting time of one hour. Serum levels of total cholesterol, LDL-C, HDL-C and triglycerides were determined in all specimens using an automatic multichannel biochemical analyser (Hitachi-7450, Hitachi, Tokyo, Japan) following routine laboratory procedures in our hospital. MHR was calculated by dividing the number of pre-operative monocyte counts by HDL-C level.16 This study complied with the Declaration of Helsinki and was carried out following approval of the Ethics Committee for Clinical Trials of Kocaeli Derince Training and Research Hospital of Health Sciences, University ethics committee approval number: 2022-106. All patients were operated on with median sternotomy under general anaesthesia. Standard CPB was established with aortic and venous cannulations, systemic heparin (300 IU/kg) with maintenance of activated clotting time > 450 seconds. Hyperkalaemic cold blood cardioplegia was applied for cardiac arrest. Surgery was performed under moderate hypothermia (28–30ºC). CPB flow was maintained at 2.2–2.5 l/min/m2, mean perfusion pressure between 50 and 80 mmHg, and haematocrit level between 20 and 25%. All distal anastomoses were done during the ACC period and proximal anastomoses onto the ascending aorta on a beating heart. All patients were intubated and transferred postoperatively to the ICU. They were extubated following the onset of spontaneous breathing and normalisation of orientation and
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