Elimination kinetics of myoglobin and creatine kinase in rhabdomyolysis: Implications for follow-up

OBJECTIVE: Creatine kinase and myoglobin are markers of muscular damage in rhabdomyolysis. Whereas myoglobin is considered to be the principal compound causing tubular damage, serum creatine kinase level is presently guiding therapeutic interventions in clinical practice to prevent acute renal failure. Because differences in elimination kinetics of these two compounds may influence therapeutic decisions, we studied elimination kinetics of myoglobin and creatine kinase in patients with rhabdomyolysis. DESIGN: Open, noncomparative study. SETTING: Intensive and intermediary care units in a university hospital. PATIENTS: A total of 13 consecutive patients with rhabdomyolysis whose baseline serum creatine kinase exceeded 5000 IU/L. Ten of 13 patients were treated with forced alkaline diuresis, and none were dialyzed. RESULTS: Myoglobin had faster elimination kinetics than creatine kinase (p <.01), and the average times to reach the 50% level of initial values were 12 hrs for myoglobin and 42 hrs for creatine kinase. Elimination of myoglobin was not affected by glomerular filtration rate. Compared with creatinine clearance (mean, 102 mL/min), myoglobin clearance was low (mean, 3 mL/min), both in patients with preserved renal function (n = 11) and in those with acute renal failure (n = 2). CONCLUSION: Serum myoglobin has faster elimination kinetics than creatine kinase in patients treated with forced alkaline diuresis for rhabdomyolysis. Considering the etiologic role of myoglobin, our data suggest that serum myoglobin level, rather than that of creatine kinase, should be used to guide therapy in patients with rhabdomyolysis.