BMI Affects Outcomes in Patients With AKI Following Cardiac Surgery

A body mass index (BMI) between 24 and 28 kg/m² is associated with better outcomes among patients with acute kidney injury (AKI) and AKI requiring renal replacement therapy (AKI-RRT) following cardiac surgery, according to a recent study.

For their study, the researchers evaluated 8455 patients undergoing cardiac surgery. Patients’ mean age was 53.2 years. Patients were categorized as underweight (BMI below 18.5 kg/m²), normal weight (BMI of 18.5 to 24 kg/m²), overweight (BMI of 24 and 28 kg/m²), and obese (BMI of 28 kg/m² or higher).
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Patients’ clinical data, including demographic perioperative data, were assessed as well as the influence of BMI on the incidence of AKI following cardiac surgery, hospital length of stay, intensive care unit (ICU) length of stay, and AKI-related mortality.

Results indicated that AKI following cardiac surgery had occurred in 2855 (33.8%) patients, with in-hospital mortality occurring in 154 (5.4%) patients. A total of 148 (5.2%) patients had experienced AKI-RRT, of whom 80 (54.1%) had died. Ultimately, AKI following cardiac surgery had occurred in 29.9% of patients who were underweight, 31.0% of patients with normal weight, 36.5% of patients with overweight, and 46.0% of patients with obesity.

The researchers observed significant differences between in-hospital mortality rates among those with AKI vs AKI-RRT. Among those with AKI, rates of in-hospital mortality were 9.5% (underweight), 6.0% (normal weight), 3.8% (overweight), and 4.3% (obese). However, among those with AKI-RRT, rates of in-hospital mortality were 69.2% (underweight), 60.8% (normal weight), 36.4% (overweight), and 58.8% (obese).

Hospital and ICU lengths of stay were similar between the groups.

“The hospital prognosis of AKI and AKI-RRT patients after cardiac surgery was best when their BMI was in the 24-28 range,” the researchers concluded.

—Christina Vogt

Reference:

Zou Z, Zhuang Y, Liu L, et al. Role of body mass index in acute kidney injury patients after cardiac surgery. CardioRenal Med. 2018;8(1):9-17. https://doi.org/10.1159/000477824.