Preoperative moderate renal impairment is an independent risk factor of transfusion in elderly patients undergoing hip fracture surgery and receiving low-molecular-weight heparin for thromboprophylaxis

Abstract

Study objective: To define the risk factors of allogeneic erythrocyte transfusion in patients older than 65 years of age who underwent hip fracture surgery.

Design: Retrospective, single-center study.

Setting: Orthopedic unit of a university hospital.

Measurements: The records of 413 consecutive patients undergoing hip fracture surgery over a 12-month period and receiving low-molecular-weight heparin (LMWH) for thromboprophylaxis were retrospectively reviewed. Preoperative independent predictors of transfusion were determined by multivariate analysis, from which a model of individual probability of transfusion was derived using creatinine clearance calculated by Cockroft-Gault (CG) and the Modification of Diet in Renal Disease (MDRD) formulas.

Main results: Using the CG and MDRD formulas, 56.9% and 50.1% of patients had moderate renal impairment that was an independent factor associated with transfusion, with adjusted odds ratios of 2.44 (1.49 - 4.02) and 2.35 (1.32 - 4.18), respectively. Other factors were fracture with trochanteric extension, preoperative hemoglobin (Hb) < 12 g/dL, and weight. The observed transfusion rate and probability of transfusion calculated with the regression logistic model were well correlated: y = 0.9534x + 0.0287, P < 0.0001, Pearson coefficient 0.988, goodness of fit, χ(2), P = 1 with CG; y = 0.9197x + 0.0504, P < 0.0001, Pearson coefficient 0.956, goodness of fit, χ(2), P = 1 with MDRD).

Conclusion: This predictive model may be useful to identify those elderly patients undergoing hip fracture repair who are at risk of blood transfusion.