High Blood Creatine Kinase Levels do not Portend Renal Failure in Exertional Rhabdomyolysis

Abstract

0255 Patients who experience exertional rhabdomyolysis (ER) often present to the hospital at the peak of their muscle pain (∼3–4 days following the event) with increased serum creatine kinase (CK) and myoglobin (Mb), classic indicators of muscle damage. High blood Mb can precipitate in the kidneys, possibly resulting in acute renal failure. Blood CK levels are commonly used as a surrogate for myoglobin in clinically assessing ER to determine whether to hospitalize and treat. However, there is no algorithm or commonly accepted critical blood CK value used to make this decision. Purpose: The purpose of this study is to examine the relationship between markers of muscle damage and renal function. Methods: 208 subjects were exercised using a modifled preacher curl bench. Damage of the elbow flexor muscles was induced by 50 maximal eccentric contractions. Blood was taken pre-exercise and 4, 7, and 10 days post-exercise and analyzed for measures of kidney function (creatinine (CR), blood urea nitrogen (BUN), potassium (K), osmololality (Osm)) and for markers of muscle damage (CK and Mb). Subjects were instructed to maintain hydration throughout the study. Results: Of the 208 subjects, 35 had CK values at 4 days post-exercise over 15,000 U/L (this value was chosen for cut off since this level is often used to determine treatment intervention.) Of the 35 subjects, 11 had CK levels between 15,000–20,000 U/l, 16 between 21,000–30,000 U/L, 7 between 31,000–50,000 U/L, and 1 subject reached a peak CK activity of 80,000 U/L. Pearson correlations of CK with Mb, K, Osm, BUN, and CR were r = 0.45 (p<0.01), 0.09 (ns), 0.26 (ns), 0.39 (p<0.01), 0.45 (p<0.01). At 4 days post-exercise, with one exception, all values of kidney function were within or close to the normal range (within 10% and/or deemed clinically insignificant). At 7 and 10 days post-exercise CK and Mb decreased towards baseline, and all values of kidney function were within or close to the normal range. No subject experienced dark urine or received any treatment for impaired renal function. Conclusion: These results show that profoundly elevated levels of CK and myoglobin in the serum can occur without impairing renal function in cases of exertional rhabdomyolysis.