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Acute kidney injury (AKI) is a serious complication in hospitalized patients, particularly after major surgical procedures, such as cardiac surgery. It can reach an incidence of approximately 37% in postoperative coronary artery bypass graft (CABG) surgery patients, with about 0.3% to 15% of patients progressing to the need for renal replacement therapy (RRT). The significance of this lies in the fact that the presence of AKI increases mortality rates to around 1.3% to 22.3%, reaching values between 25% and 88.9% in patients requiring RRT.
Given this, we propose, through this study, to assess the incidence of AKI in the postoperative period of patients undergoing CABG surgery at the University Hospital of the Federal University of Piauí (HU-UFPI), identify associated risk factors, and evaluate the effect of AKI on length of stay in the intensive care unit (ICU) and in-hospital mortality.
To achieve this, we followed prospectively patients exclusively undergoing CABG surgery at HU-UFPI from May 1, 2023, to September 31, 2023. Patients were monitored from immediate postoperative to the 5th postoperative day or until the ICU discharge date to determine the need for dialysis and death. Preoperatively, data on comorbidities and baseline creatinine level were collected. In the postoperative period, data were collected on the use of inotropic drugs up to the 2nd postoperative day, the number of revascularized arteries, duration of cardiopulmonary bypass, serum creatinine levels, urine output, need for dialysis, ICU length of stay, and mortality during the period. AKI was defined according to KDIGO criteria, and chronic kidney disease was defined as an estimated glomerular filtration rate by CKD-EPI < 60 ml/min for at least 3 months. For patients requiring renal replacement therapy, intermittent hemodialysis was used.
The sample at the end of the study period comprised 32 patients. Table I describes the baseline and preoperative characteristics of the studied population.
The incidence of AKI in the postoperative period was 21.8% (7 patients). The mean age of patients with AKI was 61.8 + 15.6 years, and for those without AKI, it was 61.4 + 8.79 years. The mean preoperative creatinine was 1.0 + 0.3 in patients who developed AKI, while in patients without this complication, it was 0.84 + 0.3. Regarding the duration of cardiopulmonary bypass, it was 76.7 + 9.47 in patients with AKI and 81.1 + 20.4 in patients without AKI. Table II compares the group that developed AKI with the group that did not in relation to other monitored variables.
Of the patients who developed AKI, 28.6% (2 patients) required dialysis, representing 6.2% of the total sample. The ICU length of stay for this group was 10.8 days (+ 13.8), while in the group without this complication, it was 3.6 days (± 0.9). Mortality in the AKI group was 14.2% (1 patient), corresponding to 3.1% of the studied sample. There were no deaths in the group without AKI.
The incidence of AKI was 21.8%. We observed that characteristics such as the presence of stroke, chronic kidney disease, and heart failure were factors that increased the likelihood of developing this complication in the studied patient group, and its development leads to an increase in ICU bed stay and mortality.