CPK

CPK

Definition:

A blood test that measures creatine phosphokinase (CPK; an enzyme found predominantly in the heart, brain, and skeletal muscle). When the total CPK level is substantially elevated, it usually indicates injury or stress to one or more of these areas.

Alternative Names:

CK; Creatine kinase; Creatine phosphokinase

How the test is performed:

Adult or child:
Blood is drawn from a vein (venipuncture), usually from the inside of the elbow or the back of the hand. The puncture site is cleaned with antiseptic, and a tourniquet (an elastic band) or blood pressure cuff is placed around the upper arm to apply pressure and cause veins below the tourniquet to distend (fill with blood). A needle is inserted into the vein, and the blood is collected in an air-tight vial or a syringe. During the procedure, the tourniquet is removed to restore circulation. Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.

Infant or young child:
The area is cleansed with antiseptic and punctured with a sharp needle or a lancet. The blood may be collected in a pipette (small glass tube), on a slide, onto a test strip, or into a small container. Cotton or a bandage may be applied to the puncture site if there is any continued bleeding.

This test may be repeated over 2 or 3 days for hospitalized people. The pattern of a rise or fall in CPK (or CPK isoenzymes) can be diagnostically significant.

How to prepare for the test:

Adult:
Usually no special preparation is necessary.

Infants and children:
The physical and psychological preparation a parent can provide for this or any test or procedure depends on the child's age, interests, previous experiences, and level of trust. For specific information regarding how you can prepare your child, see the following topics as they correspond to your child's age:

infant test or procedure preparation (birth to 1 year)
toddler test or procedure preparation (1 to 3 years)
preschooler test or procedure preparation (3 to 6 years)
schoolage test or procedure preparation (6 to 12 years)
adolescent test or procedure preparation (12 to 18 years)

How the test will feel:

When the needle is inserted to draw blood, some people may feel moderate pain, while others may feel only a prick or stinging sensation. Afterward, there may be some throbbing.

Why the test is performed:

When a muscle is damaged, CPK leaks into the bloodstream. Determining which isoenzyme (specific form of CPK) is elevated will help determine which tissue has been damaged.

This test is used to:

diagnose heart attack
evaluate cause of chest pain
determine the extent of muscle damage caused by drugs, trauma or immobility
detect early dermatomyositis and polymyositis
distinguish malignant hyperthermia from a postoperative infection
help discover carriers of muscular dystrophy (Duchenne)

Repeated CPK levels may be performed. The pattern and timing of a rise and/or fall in CPK levels can be diagnostically significant, particularly if a heart attack is suspected.

What abnormal results mean:

Higher than normal total CPK levels may be seen with:

heart attack
myocarditis (inflammation of the heart muscle)
central nervous system trauma or stroke
convulsions
delirium tremens
dermatomyositis or polymyositis
electric shock
muscular dystrophies
pulmonary infarction (tissue death)

Additional conditions that may give positive test results:

What the risks are:

excessive bleeding
fainting or feeling light-headed
hematoma (blood accumulating under the skin)
infection (a slight risk any time the skin is broken)
multiple punctures to locate veins

Special considerations:

Other tests will need to be conducted to determine the exact location of muscle damage.

Factors that can affect test results include cardiac catheterization, intramuscular injections, trauma to muscles, recent surgery, and vigorous and prolonged exercise.

Drugs that can increase CPK measurements include amphotericin B, ampicillin, some anesthetics, anticoagulants, aspirin, clofibrate, dexamethasone, furosemide, morphine, alcohol and cocaine.

Veins and arteries vary in size from one patient to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.

Review Date: 11/16/2001
Reviewed By: Steven Angelo, M.D. Department of Internal Medicine, Yale School of Medicine, Hospital of Saint Raphael, New Haven, CT. Review provided by VeriMed Healthcare Network.

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