PURPOSE: Creatine is released into the circulation after destruction of muscle cells in rhabdomyolysis patients. As excess circulating creatine forms creatinine, the serum creatinine (SCr) elevation in rhabdomyolysis patients may become disproportionate to the degree of reduction in glomerular filtration rate (GFR).
METHODS: All 469 inpatients at a tertiary care medical center with rhabdomyolysis as a discharge diagnosis from January 1, 2005 till June 30, 2010 were reviewed. Only 29 rhabdomyolysis patients had normal admission SCr and a subsequent rise of SCr during the hospital stay (with serum creatine kinase greater than 1500 U/L on the day when SCr first became abnormal). Thirty-two patients were chosen using random number table from all non-rhabdomyolysis inpatients, admitted during the aforesaid period, with normal admission SCr and subsequent development of acute kidney injury (AKI) during the hospital stay (non-rhabdomyolysis group). The rate of SCr rise, the blood urea nitrogen (BUN) to SCr ratio (on the day SCr reached its peak), and the serum electrolyte levels (potassium, magnesium, inorganic phosphate, and calcium) in these two groups were compared.
RESULTS: The rate of SCr rise to its peak (in mg/dL/day) was faster in the rhabdomyolysis group vs. non-rhabdomyolysis group (1.18 vs. 0.60, p = 0.0001). The two groups had similar electrolyte levels. The rate of SCr rise to its peak (in mg/dL/day) remained faster in the rhabdomyolysis group vs. non-rhabdomyolysis group even when males below 50 years of age (who are likely to have higher muscle mass and thus higher circulating creatinine) were analyzed (1.45 vs. 0.69, p = 0.003). The BUN to SCr ratio (on the day SCr reached its peak) was lower in the rhabdomyolysis group vs. non-rhabdomyolysis group (13.18 vs. 20.37, p = 0.002).
CONCLUSIONS: A faster rise of SCr and a lower peak BUN/creatinine ratio in the setting of rhabdomyolysis suggest that SCr elevation in such patients may be disproportionate to the degree of reduction in GFR.
CLINICAL IMPLICATIONS: SCr may not be an accurate marker of GFR reduction in the setting of rhabdomyolysis. Other markers/derangements of AKI (BUN, urine output, electrolytes, etc.) should be closely monitored in such patients.
DISCLOSURE: The following authors have nothing to disclose: Neeraj Sinha, Nivas Balasubramaniyam, Inderpreet Dardi, Tarek Moqattash, Dipak Chandy
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