Role of Body Mass Index in Acute Kidney Injury Patients after Cardiac Surgery

Abstract

Background/Aims: To explore the association of body mass index (BMI) with the risk of developing acute kidney injury after cardiac surgery (CS-AKI) and for AKI requiring renal replacement therapy (AKI-RRT) after cardiac surgery. Methods: Clinical data of 8,455 patients undergoing cardiac surgery, including demographic preoperative, intraoperative, and postoperative data were collected. Patients were divided into underweight (BMI <18.5), normal weight (18.5≤ BMI <24), overweight (24≤ BMI <28), and obese (BMI ≥28) groups. The influence of BMI on CS-AKI incidence, duration of hospital, and intensive care unit (ICU) stays as well as AKI-related mortality was analyzed. Results: The mean age of the patients was 53.2 ± 13.9 years. The overall CS-AKI incidence was 33.8% (n = 2,855) with a hospital mortality of 5.4% (n = 154). The incidence of AKI-RRT was 5.2% (n = 148) with a mortality of 54.1% (n = 80). For underweight, normal weight, overweight, and obese cardiac surgery patients, the AKI incidences were 29.9, 31.0, 36.5, and 46.0%, respectively (p < 0.001). The hospital mortality of AKI patients in the 4 groups was 9.5, 6.0, 3.8, and 4.3%, whereas the hospital mortality of AKI-RRT patients in the 4 groups was 69.2, 60.8, 36.4, and 58.8%, both significantly different (p < 0.05). Hospital and ICU stay durations were not significantly different in the 4 BMI groups. Conclusion: The hospital prognosis of AKI and AKI-RRT patients after cardiac surgery was best when their BMI was in the 24-28 range.