From the Guidelines
To evaluate Creatine Kinase (CK) laboratory results for rhabdomyolysis, order a serum CK level and look for values exceeding 5 times the upper limit of normal, typically above 1,000 U/L, and monitor trends every 24 hours, as this is crucial for guiding treatment decisions and assessing the risk of complications like acute kidney injury. When evaluating CK levels, it is essential to consider the clinical context, as CK levels can be elevated in other conditions like recent intense exercise, muscle injuries, or certain medications 1. The diagnosis of rhabdomyolysis should be based on a combination of clinical symptoms, such as muscle pain, weakness, and dark urine, and laboratory results, including CK levels, renal function (creatinine, BUN), electrolytes (particularly potassium), and urine myoglobin 1. Some key points to consider when evaluating CK levels include:
- Severe rhabdomyolysis is often associated with CK levels above 5,000 U/L 1
- CK levels above 75,000 IU/L are associated with a high incidence of newly formed acute kidney injury 1
- Monitoring CK trends is more important than a single value, as it helps guide treatment decisions and assess the risk of complications like acute kidney injury
- A urine dipstick positive for blood without red blood cells on microscopy can indicate myoglobinuria, which is a sign of rhabdomyolysis It is also important to note that myoglobin measurement may be more sensitive and specific than CK levels in identifying the risk of acute kidney injury, which is correlated with increased mortality 1. Therefore, a comprehensive evaluation of CK laboratory results for rhabdomyolysis should include monitoring CK trends, assessing renal function, and considering the clinical context, as well as measuring myoglobin and plasma potassium levels.
From the Research
Evaluating Creatine Kinase (CK) Laboratory Results for Rhabdomyolysis
To evaluate CK laboratory results for rhabdomyolysis, consider the following points:
- The diagnosis of rhabdomyolysis is confirmed when the serum CK level is > 1000 U/L or at least 5x the upper limit of normal 2
- CK is the biochemical "gold standard" for diagnosis of rhabdomyolysis 3
- A substantial rise in serum CK >50 000 IU/L is indicative of exertional rhabdomyolysis 4
- Extremely high CK activity (>150 000 U/L) may lead to acute kidney injury (AKI), but preserved kidney function is possible 5
- Serum CK levels are not associated with an increased need for continuous renal replacement therapy in patients with AKI following rhabdomyolysis 6
Key Considerations
- The clinical presentation of rhabdomyolysis may vary, ranging from asymptomatic to severe conditions such as volume depletion, metabolic and electrolyte abnormalities, and AKI 2
- Prompt recognition of rhabdomyolysis is important for timely and appropriate treatment 2
- Treatment of the underlying cause of the muscle insult is the first component of rhabdomyolysis management, followed by early and aggressive fluid replacement using crystalloid solution 2