A risk prediction score for kidney failure or mortality in rhabdomyolysis

Abstract

Importance: Rhabdomyolysis ranges in severity from asymptomatic elevations in creatine phosphokinase levels to a life-threatening disorder characterized by severe acute kidney injury requiring hemodialysis or continuous renal replacement therapy (RRT).

Objective: To develop a risk prediction tool to identify patients at greatest risk of RRT or in-hospital mortality.

Design, setting, and participants: Retrospective cohort study of 2371 patients admitted between January 1, 2000, and March 31, 2011, to 2 large teaching hospitals in Boston, Massachusetts, with creatine phosphokinase levels in excess of 5000 U/L within 3 days of admission. The derivation cohort consisted of 1397 patients from Massachusetts General Hospital, and the validation cohort comprised 974 patients from Brigham and Women's Hospital.

Main outcomes and measures: The composite of RRT or in-hospital mortality.

Results: The causes and outcomes of rhabdomyolysis were similar between the derivation and validation cohorts. In total, the composite outcome occurred in 19.0% of patients (8.0% required RRT and 14.1% died during hospitalization). The highest rates of the composite outcome were from compartment syndrome (41.2%), sepsis (39.3%), and following cardiac arrest (58.5%). The lowest rates were from myositis (1.7%), exercise (3.2%), and seizures (6.0%). The independent predictors of the composite outcome were age, female sex, cause of rhabdomyolysis, and values of initial creatinine, creatine phosphokinase, phosphate, calcium, and bicarbonate. We developed a risk-prediction score from these variables in the derivation cohort and subsequently applied it in the validation cohort. The C statistic for the prediction model was 0.82 (95% CI, 0.80-0.85) in the derivation cohort and 0.83 (0.80-0.86) in the validation cohort. The Hosmer-Lemeshow P values were .14 and .28, respectively. In the validation cohort, among the patients with the lowest risk score (<5), 2.3% died or needed RRT. Among the patients with the highest risk score (>10), 61.2% died or needed RRT.

Conclusions and relevance: Outcomes from rhabdomyolysis vary widely depending on the clinical context. The risk of RRT or in-hospital mortality in patients with rhabdomyolysis can be estimated using commonly available demographic, clinical, and laboratory variables on admission.

Figure 1. Rates of In-hospital Mortality or Acute Kidney Injury Requiring Renal Replacement Therapy, Stratified by Cause of Rhabdomyolysis

AKI indicates acute kidney injury; RRT, renal replacement therapy.

Figure 2. Probability of In-hospital Mortality or Acute Kidney Injury Requiring Renal Replacement Therapy

Dark blue bars and light blue bars show the observed risk at Massachusetts General Hospital (MGH) and Brigham and Women’s Hospital (BWH), respectively. RRT indicates renal replacement therapy.