Patient Care

New Model May Predict Risk of Acute Kidney Injury in Orthopedic Patients


Clinical question: What is the risk of acute kidney injury after orthopedic surgery, and does it impact mortality?

Background: Current studies show that acute kidney injury is associated with increased long-term mortality, future development of chronic kidney disease, and increased healthcare costs. However, no externally validated models are available to predict patients undergoing non-cardiac surgery at risk of postoperative acute kidney injury.

Study design: Observational, cohort study.

Setting: Teaching and private hospitals in the National Health Service (NHS) in the Tayside region of Scotland.

Synopsis: Investigators enrolled 10,615 adults >18 years of age undergoing orthopedic surgery into two groups: development cohort (6,220 patients) and validation cohort (4,395 patients). Using the development cohort, seven predictors were identified in the risk model: age at operation, male sex, diabetes, lower estimated glomerular filtration rate (GFR), use of ACE inhibitor/ARB, number of prescribing drugs, and American Society of Anesthesiologists (ASA) grade.

The model’s predictive performance for discrimination was good in the development cohort (C statistic 0.74; 95% CI, 0.72–0.76) and validation cohort (C statistic 0.7). Calibration was good in the development cohort but overestimated the risk in the validation cohort. Postoperative acute kidney injury developed in 672 (10.8%) patients in the development cohort and 295 (6.7%) in the validation cohort. Thirty percent (3,166) of the 10,615 patients enrolled in this study died over the median follow-up of 4.58 years. Survival was worse in the patients with acute kidney injury (adjusted hazard ratio 1.53; 95% CI, 1.38–1.70), worse in the short term (90-day adjusted hazard ratio 2.36; 95% CI, 1.94–2.87), and diminished over time.

Bottom line: A predictive model using age, male sex, diabetes, lower GFR, use of ACE inhibitor/ARB, multiple medications, and ASA grades might predict risk of postoperative acute kidney injury in orthopedic patients.

Citation: Bell S, Dekker FW, Vadiveloo T, et al. Risk of postoperative acute kidney injury in patients undergoing orthopaedic surgery—development and validation of a risk score and effect of acute kidney injury on survival: observational cohort study. BMJ 2015; 351:h5639.

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