Pre- and postoperative anemia, acute kidney injury, and mortality after coronary artery bypass grafting surgery: a retrospective observational study

• Published in: Canadian journal of anesthesia Vol. 65; no. 1; pp. 46 - 59
• Main Authors: Oprea, Adriana D., Del Rio, J. Mauricio, Cooter, Mary, Green, Cynthia L., Karhausen, Jörn A., Nailer, Patrick, Guinn, Nicole R., Podgoreanu, Mihai V., Stafford-Smith, Mark, Schroder, Jacob N., Fontes, Manuel L., Kertai, Miklos D.
• Format: Journal Article
• Language: English
• Published: New York Springer US 2018; Springer Nature B.V
• Subjects: Academic Medical Centers; Acute Kidney Injury - epidemiology; Aged; Aged, 80 and over; Anemia; Anemia - complications; Anemia - epidemiology; Anesthesiology; Cardiology; Coronary Artery Bypass - adverse effects; Coronary Artery Bypass - methods; Coronary Artery Bypass - mortality; Creatinine - blood; Critical Care Medicine; Female; Heart surgery; Hemoglobins - metabolism; Humans; Incidence; Intensive; Male; Medicine; Medicine & Public Health; Middle Aged; Observational studies; Pain Medicine; Pediatrics; Pneumology/Respiratory System; Postoperative Complications - epidemiology; Postoperative Period; Preoperative Period; Proportional Hazards Models; Reports of Original Investigations; Retrospective Studies; Risk Factors; Skin & tissue grafts; Surgical outcomes
• ISSN: 0832-610X; 1496-8975
• DOI: 10.1007/s12630-017-0991-0

Background Preoperative and postoperative anemia have been identified individually as potential risk factors for postoperative complications after coronary artery bypass grafting (CABG) surgery. Their interrelationship with acute kidney injury (AKI) and long-term mortality, however, has not been clearly defined and was the purpose of this study. Methods We retrospectively evaluated 6,130 adult patients undergoing CABG surgery performed at a single large academic medical center. Preoperative and postoperative hemoglobin concentrations were used as continuous predictors of postoperative AKI and mortality. Additionally, sex-specific preoperative (< 13 g·dL −1  in men and < 12 g·dL −1  in women) and postoperative anemia (the median of the lowest in-hospital values) were used as categorical predictors. AKI was defined according to the Kidney Disease: Improving Global Outcomes (KDIGO) Clinical Practice Guidelines, when serum creatinine rose ≥ 50% during the period between day of surgery and postoperative day ten, or when a 0.3 mg·dL −1  (26.5 μmol·L −1 ) increase was detected in a rolling 48-hr window from the day of surgery to the tenth postoperative day. The association of preoperative and postoperative hemoglobin levels and anemia patterns with postoperative AKI and mortality were assessed via univariable and multivariable Cox proportional hazard analyses with time-varying effects for postoperative serum hemoglobin concentrations. Results The median preoperative and median minimum postoperative serum hemoglobin concentrations were 13.1 g·dL −1 and 8.8 g·dL −1 , respectively. The incidence of AKI was 58%. Overall, 1,880 (30.7%) patients died an average of 6.8 yr after surgery. After adjusting for differences in baseline and clinical characteristics, on any given day, patients with preoperative anemia (multivariable hazard ratio [HR], 1.23; 95% confidence interval [CI], 1.13 to 1.33; P < 0.001) and those with a combination of preoperative and postoperative anemia (multivariable HR, 1.24; 95% CI, 1.09 to 1.40; P < 0.0008) were at an elevated risk for developing postoperative AKI and mortality (preoperative anemia: multivariable HR, 1.29; 95% CI, 1.15 to 1.44; P < 0.001; preoperative and postoperative anemia: multivariable HR, 1.50; 95% CI, 1.25 to 1.79; P < 0.001). Conclusions Our findings suggest that preoperative anemia alone and preoperative anemia combined with postoperative anemia are associated with AKI and mortality after CABG surgery.