Acute kidney injury in rhabdomyolysis defined by serum creatine kinase ≥1000 IU/L: association with creatine kinase levels

BACKGROUND: Rhabdomyolysis is a potentially life-threatening consequence of muscle injury. The aim of our study was to analyse the relation between serum creatine kinase (CK), acute kidney injury (AKI), renal outcomes, and mortality among adults with serum CK over 1000 IU/L within 72 h of hospital admission. METHODS: Our single-centre cohort study enrolled 855 patients with serum CK over 1000 IU/L. Univariate and multivariate analyses were performed for short- and long-term mortality, based on a logistic regression model and a cox proportional hazards model, respectively. RESULTS: AKI developed in 368 of 855 patients (43%). Those with CK 5001-10 000 IU/L and over 10 000 IU/L were more likely to develop stages 2 and 3 AKI than those with lower levels of serum CK (P = .001 and P < .001, respectively). Renal replacement therapy (RRT) was required by 43 (5.0%) patients during their hospitalization, 15 of whom had pre-existing non-dialysis dependent chronic kidney disease (CKD). The requirement for RRT was greatest among those with serum CK over 5000 IU/L (P < .001). Among the 269 patients with AKI who survived at least 3 years, 235 (87.4%) had complete recovery of renal function, 26 (9.7%) had partial recovery, while 8 (3.0%) remained dialysis dependent. Complete recovery was more likely in patients with stages 1 and 2 AKI than those with stage 3 AKI (P < .018). All eight patients who remained dialysis dependent had initially presented with stage 3 AKI. For patients who were still alive 90 days after hospital admission, neither AKI or CK levels were associated with subsequent mortality. Age was the only predictor of their long-term mortality identified by multivariate analysis. CONCLUSIONS: AKI is a common but not inevitable consequence of rhabdomyolysis. Most patients with AKI have complete recovery of renal function. Serum CK predicts likelihood of more severe forms of AKI but has no discernible effect on either short- or long-term mortality. Key messages What is already known on this topic: Acute kidney injury (AKI) is a common and potentially life-threatening complication of rhabdomyolysis. Studies have shown varying results when describing relationship between serum creatine kinase (CK) and AKI. What this study adds: Our study showed an AKI incidence of 43% in patients with serum CK over 1000 IU/L. Most patients with AKI had complete recovery of their renal function. Serum CK over 5000 IU/L predicted likelihood of more severe forms of AKI, including the need for dialysis, but was not associated with either short or long-term mortality. How this study might affect research, practice, or policy: Greater awareness of the relation between serum CK and AKI should prompt preventive measures, including early rehydration and treatment of infection if present, to reduce the incidence of severe AKI.