Creatine Kinase (CK)

 Creatine kinase (CK) is an enzyme found in muscle and brain tissue that reflects tissue catabolism resulting from cell trauma. The CK level begins to rise within 6 hours of muscle damage, peaks at 18 hours, and returns to normal in 2 to 3 days. The test for CK is performed to detect myocardial or skeletal muscle damage or central nervous systemdamage. Isoenzymes include CK-MB (cardiac), CK-BB (brain), and CK-MM (muscles):

• CK-MM is found mainly in skeletal muscle.
• CK-MB is found mainly in cardiac muscle
• CK-BB is found mainly in brain tissue

Normal Lab Values for Creatinine Kinase and Isoenzymes

• Creatine kinase (CK)
  • Male: 38 – 174 U/L
  • Women: 26 – 140 U/L
• Creatinine kinase isoenzymes
  • CK-MM: 95% – 100% of total
  • CK-MB: 0% – 5% of total
  • CK-BB: 0%

Nursing Considerations

• If the test is to evaluate skeletal muscle, instruct the client to avoid strenuous physical activity for 24 hours before the test.
• Instruct the client to avoid ingestion of alcohol for 24 hours before the test.
• Invasive procedures and intramuscular injections may falsely elevate CK levels.