Background: The present observational study was undertaken to identify potential markers of poor outcome, such as renal failure and mortality, after hip fracture surgery.
Methods: Forty-three patients, with a mean age of 78 years, were studied having undergone acute hip fracture surgery. Analysis included the urinary excretion of cortisol, albumin and sodium. The degree of fluid retention was evaluated based on the urinary excretion of metabolic end products. Fluid retention and the excretion of albumin and neutrophil gelatinase-associated lipocalin (NGAL) were measured repeatedly in a sub-group of 15 patients who also underwent haemodynamic monitoring. The perioperative change in serum creatinine and a 30-day mortality served as outcome measures.
Results: Although serum creatinine increased by > 25% in 21% of the patients, only a high preoperative creatinine concentration correlated with a 30-day mortality. The subgroup analysis revealed that fluid retention was pronounced and remained essentially unchanged up to the first postoperative day. A rise in serum creatinine was always preceded by increased urinary excretion of NGAL that, in turn, was associated with preoperative fluid retention. The only perioperative event that correlated with a higher 30-day mortality was perioperative aggravation of albuminuria (67% vs 0%, P < 0.01), which became more common with advanced age and a low cardiac index.
Conclusions: Two different mechanisms seem to affect the kidneys during hip fracture surgery. The first elevates the serum creatinine concentration while the second increases the albuminuria. Only the second mechanism had a bearing on mortality.
Keywords: acute kidney injury; albuminuria; creatinine; hip fracture; mortality; surgery.