Association Between Preoperative Frailty and Postoperative Acute Kidney Injury, Complications, and Resource Utilization in Older Patients Undergoing Hip Fracture Surgery.

BACKGROUND: Hip fractures are a major public health burden in older adults. Acute kidney injury (AKI) is among the most frequent complications following hip fracture surgery and is associated with poor clinical outcomes. We investigated the relationship between preoperative frailty and postoperative complications, including AKI, using a nationwide electronic medical records database in Japan. METHODS: We identified patients aged ≥ 65 years who underwent hip fracture surgery between April 2005 and December 2021. Frailty was measured using the Hospital Frailty Risk Score (HFRS), with scores ≥ 5 indicating frailty. The primary outcome was AKI within 7 days postoperatively. Secondary outcomes included 30-day major adverse kidney events (MAKE30), cardiac, pulmonary, and delirium complications, postoperative transfusion, and length of stay. Restricted cubic spline analysis assessed associations using HFRS as a continuous variable. RESULTS: Among 29 684 patients, 17 656 (59.5%) were frail. Adjusted odds ratios (frail vs. non-frail) were 0.97 (95% CI 0.83-1.14; p = 0.72) for AKI, 1.07 (0.80-1.44; p = 0.65) for MAKE30, 1.11 (0.73-1.70; p = 0.62) for cardiac complications, 1.68 (1.39-2.02; p < 0.001) for pulmonary complications, and 1.35 (1.13-1.62; p < 0.001) for postoperative delirium. Frail patients also had higher transfusion use and longer hospital stay. Restricted cubic spline analysis demonstrated increasing risks of pulmonary complications, delirium, and transfusion with higher HFRS. CONCLUSION: Preoperative frailty was not associated with postoperative AKI or MAKE30. In contrast, frailty was significantly associated with increased risks of pulmonary complications, delirium, higher transfusion requirements, and longer hospital stay.