Clinical Impact of Different Crystalloid Solution on Early Biomarkers of Kidney Injury After Lumbar Fusion Surgery in Elderly Patients

This is a single-center prospective randomized comparative study. A total of 174 elderly patients scheduled for elective lumbar fusion surgery under general anesthesia will be randomly assigned in a 1:1 ratio to receive either sodium acetate Ringer's solution (Group A, n = 87) or sodium lactate Ringer's solution (Group B, n = 87) for intraoperative fluid management. Conventional renal function indicators, including serum creatinine (SCr) and estimated glomerular filtration rate (eGFR), as well as early renal injury biomarkers, including lactate, urinary neutrophil gelatinase-associated lipocalin (uNGAL), urinary kidney injury molecule-1 (uKIM-1), and serum cystatin C (sCysC), will be compared between the two groups. Postoperative AKI will be assessed according to the KDIGO serum creatinine criteria. The study will evaluate whether the choice of intraoperative crystalloid solution influences early postoperative renal stress in this high-risk population.