The Association Between Rhabdomyolysis, Acute Kidney Injury, Renal Replacement Therapy, and Mortality

BACKGROUND: We examined the association between creatine phosphokinase level in rhabdomyolysis patients and risk of acute kidney injury, renal replacement therapy, and death within 30 days. METHODS: The cohort included patients admitted with rhabdomyolysis from November 1, 2011 to March 1, 2014. Rhabdomyolysis was defined as a creatine phosphokinase level higher than 1000 U/L. Information on laboratory variables was obtained from a laboratory database. Medical data were obtained from registries. Acute kidney injury was defined according to the Kidney Disease Improving Global Outcome (KDIGO) guidelines. The 30-day risk of outcomes was estimated using the cumulative incidence method. Spline regression applied to imputed datasets with adjustment for baseline variables was used to assess the appropriateness of the categorization chosen for creatine phosphokinase (1000-5000 U/L, 5001-15,000 U/L, and 15,000+ U/L). RESULTS: The study included 1027 patients (58.2% male) with a median age of 73.5 years. The median creatine phosphokinase level at rhabdomyolysis diagnosis was 2257 U/L (interquartile range=1404-3961 U/L). The 30-day risks of acute kidney injury according to the three creatinine phosphokinase levels were 42% (95% CI=38-45%), 44% (95% CI=36-52%), and 74% (95% CI=57-85%), respectively, and the risks of renal replacement therapy for the three levels were 3% (95% CI=2-5%), 4% (95% CI=2-7%), and 11% (3-23%), respectively. The 30-day risk of death was 17% (95% CI=14-20%), 16% (95% CI=11-22%), and 11% (95% CI=3-23%), respectively. With increasing creatine phosphokinase levels, the spline plots supported the increasing risk of acute kidney injury and renal replacement therapy, as well as a decreasing risk of death. However, the risk estimates for renal replacement therapy and death were imprecise. CONCLUSION: Elevated initial creatine phosphokinase values were associated with an increased risk of acute kidney injury, while estimates of the risk of renal replacement therapy and death were imprecise.