Association of the standardized phase angle with the incidence and severity of acute kidney injury after cardiac surgery

Bioelectrical impedance permits the measurement of variables related to morbidity and mortality in cardiac surgery patients. The preoperative phase angle (PhA) is one of the variables associated with increased mortality, prolonged duration of invasive mechanical ventilation, and prolonged hospital stay. However, its relationship with acute kidney injury (AKI) is unknown. A prospective cohort study measured the PhA 24 hours before surgery, and the standardized phase angle (SPhA) was calculated from data from the reference population. The incidence and severity of AKI were determined over 7 days after surgery. Multivariate analysis was performed to determine the relationships between PhA or SPhA and the incidence and severity of AKI after cardiac surgery. A total of 120 patients were recruited. The incidence of AKI during the 7 days after cardiac surgery was 37%, 70% of which were classified as Kidney Disease Improving Global Outcomes (KDIGO) 1, 19% as KDIGO 2, and 11% as KDIGO 3. SPhA > -0.54 was associated with a lower incidence of AKI at 21% and lower AKI KDIGO 1 at 8% (2/24 patients) than SPhA ≤ -0.54 was associated with an AKI incidence of 40% (P = .072) and AKI KDIGO 1 incidence of 30% (29/96 patients) (P = .029). There were no differences in the incidence of AKI classified as KDIGO 2-3. According to the multivariate analysis, an SPhA > -0.54 was a protective factor (RR 0.254, CI 0.074-0.870, P = .029). A high SPhA (>-0.54) serves as a protective factor against AKI, particularly against AKI classified as KDIGO 1.