From the Guidelines
Yes, checking creatine kinase (CK) levels is crucial when evaluating for rhabdomyolysis, as it directly measures muscle breakdown and helps identify the risk of acute kidney injury, which is correlated with increased mortality. CK is the primary laboratory test used to diagnose this condition, and its levels are markedly elevated in rhabdomyolysis, often exceeding 1,000 U/L and sometimes reaching 100,000 U/L or higher 1. When suspecting rhabdomyolysis, ordering a CK test immediately and monitoring levels serially is essential to track disease progression or resolution. Some key points to consider when evaluating for rhabdomyolysis include:
- Normal CK levels typically range from 20-200 U/L, but in rhabdomyolysis, they are significantly elevated 1
- The degree of CK elevation often correlates with the extent of muscle damage
- Other important laboratory tests to order concurrently include renal function tests (BUN, creatinine), electrolytes (particularly potassium, calcium, and phosphorus), and urinalysis to check for myoglobinuria
- Early detection through CK measurement is crucial for prompt intervention with aggressive IV fluid therapy to prevent acute kidney injury, which is the most serious complication of rhabdomyolysis
- Raising CPK levels above five times normal (approximately 1000 IU/L) is a sign of rhabdomyolysis, and levels above 75,000 IU/L are associated with a high incidence of newly formed acute kidney injury 1
- The measurement of plasma myoglobin may be more sensitive and specific than CPKs in identifying the risk of acute kidney injury, which is correlated with increased mortality 1
From the Research
Rhabdomyolysis and Creatine Kinase (CK) Levels
- Rhabdomyolysis is a syndrome caused by muscle breakdown, which can lead to acute kidney injury (AKI) and other complications 2.
- Creatine kinase (CK) levels are often used as a biological marker to identify patients at high risk of AKI following rhabdomyolysis 3.
- Elevated CK levels can range from 10,000 to 200,000 or higher in patients with rhabdomyolysis, with higher levels indicating greater renal damage and associated complications 2.
Monitoring CK Levels
- Monitoring CK levels is important in patients with rhabdomyolysis to assess the risk of AKI and potential renal damage 4.
- A peak CK level of at least 5,000 U/L has been shown to be 55% specific and 83% sensitive for predicting AKI requiring renal replacement therapy 3.
- However, CK levels may not be a specific or early predictor of AKI in patients with rhabdomyolysis, and other factors such as the McMahon score may be more useful for identifying patients at high risk 3.
Clinical Implications
- Patients with extremely high CK activity (>150,000 U/L) may not always develop AKI, and preserved kidney function is possible in some cases 5.
- Young age, no concurrent cocaine use, and adequate oral fluid hydration may prevent AKI in rhabdomyolysis 5.
- Clinicians should have a high index of suspicion for rhabdomyolysis in patients with multiple risk factors, and early recognition of the disease is important for preventing and managing life-threatening complications 2.