Haptoglobin 2‐2 Phenotype Is Associated With Increased Acute Kidney Injury After Elective Cardiac Surgery in Patients With Diabetes Mellitus

BACKGROUND: Recent studies reported an association between the 2‐2 phenotype of haptoglobin (Hp 2‐2) and increased cardiorenal morbidity in nonsurgical diabetic patients. Our goal was to determine whether the Hp 2‐2 phenotype was associated with acute kidney injury (AKI) after elective cardiac surgery in patients with diabetes mellitus. METHODS AND RESULTS: We prospectively enrolled 99 diabetic patients requiring elective cardiac surgery with cardiopulmonary bypass. Haptoglobin phenotypes were determined by gel electrophoresis. Cell‐free hemoglobin, haptoglobin, and total serum bilirubin were quantified as hemolysis markers. The primary outcome was postoperative AKI, as defined by the Acute Kidney Injury Network classification. The incidence of AKI was significantly higher in Hp 2‐2 patients compared with patients without this phenotype (non–Hp–2‐2; 55.6% versus 27%, P<0.01). The need for renal replacement therapy was also significantly higher in the Hp 2‐2 group (5 patients versus 1 patient, P=0.02). Thirty‐day mortality (3 versus 0 patients, P=0.04) and 1‐year mortality (5 versus 0 patients, P<0.01) were also significantly higher in patients with the Hp 2‐2 phenotype. In multivariable analysis, Hp 2‐2 was an independent predictor of postoperative AKI (P=0.01; odds ratio: 4.17; 95% confidence interval, 1.35–12.48). CONCLUSIONS: Hp 2‐2 phenotype is an independent predictor of postoperative AKI and is associated with decreased short and long‐term survival after cardiac surgery in patients with diabetes mellitus.