“Check the CPK.” This is the first thing that we hear when working up someone for rhabdomyolysis. But at what level of CPK should you be concerned? And how can you confidently say that someone has rhabdo, anyway?
Rhabdo is a clinical diagnosis: there is no one specific test you can do for it, and definitions change from clinician to clinician. Make a diagnosis of rhabdo with a markedly elevated CPK (most would agree >10,000 is alarming) along with electrolyte abnormalities and/or myoglobin in the urine or renal dysfunction. A single CPK elevation does NOT make rhabdo.
Several abnormalities you may see:
- Signs of renal failure (acute tubular necrosis)
- UA dipstick positive for blood with no RBCs in the sediment
- hyperkalemia, hyperphosphatemia, hypocalcemia
- arrhythmias from above electrolyte abnormalities
It is important to note when muscles are swollen, compartment syndrome is a threat. Another feared complication of rhabdo is DIC.