Predictive Value of Serum Myoglobin and Creatine Phosphokinase for Development of Acute Kidney Injury in Traumatic Rhabdomyolysis.

Introduction: Rhabdomyolysis (RM) is a condition where there is injury to striated muscle fibers causing release of myoglobin, creatine phosphokinase (CPK), and other intracellular contents into the circulation. High myoglobin levels cause acute kidney injury (AKI). Trauma is the most common cause of RM and development of complications related to the degree of myoglobin released. Currently, the degree of RM is assessed and treatment is instituted based on serum CPK. As myoglobin is the direct cause of AKI, we set out to determine if serum myoglobin is a more reliable predictor than CPK for the development of AKI in traumatic RM.

Methodology: A prospective observational study of 90 patients was admitted to the surgical Intensive Care Unit/high dependency unit of a tertiary hospital with traumatic RM whose serum CPK >5000 U/L. Along with standard treatment including intravascular volume optimization and hemodynamic stabilization, they were treated with "crush protocol." Daily/twice a day, serum CPK and myoglobin were estimated. Categorical data are expressed as frequency and percentage, and the continuous variables are presented as mean (standard deviation) or median (interquartile range) based on normality. Other statistical analyses were done using the Chi-square test, independent -test, and rank sum test based on normality.

Results: Fourteen out of 90 patients developed AKI and one patient required renal replacement therapy. CPK value of >12,000 U/l was identified to have 64% sensitivity and 56% specificity for developing AKI whereas serum myoglobin value of >5000 ng/ml was identified to have 78% sensitivity and 77% specificity for developing AKI.

Conclusion: Following traumatic RM, in patients on "crush protocol," serum myoglobin is a more sensitive and specific test than serum CPK, for predicting AKI.