Catecholamines - blood

Definition

The blood test for catecholamines measures the level of catecholamines in the plasma portion of blood.

How the test is performed

Catecholamines are more often measured with a urine test than with this blood test.

Blood is drawn from a vein, usually from the inside of the elbow or the back of the hand. The puncture site is cleaned with antiseptic. An elastic band is placed around the upper arm to apply pressure and cause the vein to swell 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 band 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.

In infants or young children:

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. A bandage may be applied to the puncture site if there is any bleeding.

How to prepare for the test

Certain foods can increase catecholamine levels including coffee, tea, bananas, chocolate, cocoa, citrus fruits, and vanilla. Avoid these foods for several days prior to the test, particularly if both serum and urine catecholamines are to be measured.

Avoid other interfering factors:

• Acute stress
• Vigorous exercise

Consult your health care provider regarding the need to discontinue potentially interfering drugs. Drugs that can increase catecholamine measurements include caffeine, levodopa, lithium, aminophylline, chloral hydrate, clonidine, disulfiram, erythromycin, insulin, methenamine, methyldopa, nicotinic acid (large doses), quinidine, tetracyclines, and nitroglycerin.

Drugs that can decrease catecholamine measurements include clonidine, disulfiram, guanethidine, imipramine, MAO inhibitors, phenothiazines, salicylates, and reserpine.

Never discontinue any medication without first consulting your provider.

How the test will feel

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

Why the test is performed

This test is used primarily to screen for, diagnose, and monitor treatment of pheochromocytoma or neuroblastoma.

Catecholamines are chemically similar small molecules derived from tyrosine, an amino acid. The major catecholamines are dopamine, norepinephrine, and epinephrine (which used to be called adrenalin).

• Dopamine is a neurotransmitter (a chemical used to transmit impulses between nerve cells), mainly found in the brain.
• Norepinephrine is the primary neurotransmitter in the sympathetic nervous system (controls "fight or flight" reactions) and is also found in the brain.
• Epinephrine is not only a brain neurotransmitter but also a major hormone in the body. Epinephrine is secreted from the adrenal medulla in response to low blood glucose, exercise, and various forms of acute stress. Epinephrine causes several responses:
  • A breakdown of glycogen to glucose in the liver
  • The release of fatty acids from fat tissue
  • Vasodilation of small arteries within muscle tissue
  • Increase in rate and strength of the heartbeat

Normal Values

Normal value ranges may vary slightly among different laboratories.

Epinephrine: 20 ng/100 mL (ng/mL = nanograms per milliliter)

Norepinephrine: 60 ng/100 mL

What abnormal results mean

Elevated levels of blood catecholamines may indicate the following:

• Acute anxiety
• Ganglioblastoma (very rare)
• Ganglioneuroma (very rare)
• Neuroblastoma (rare)
• Pheochromocytoma (rare)
• Severe stress

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

The test's accuracy is affected by several foods and drugs as well as such things as physical activity and stress.

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 from some people than from others.

Illustrations

Blood test

Page Content:

Norepinephrine - blood; Epinephrine - blood; Adrenalin - blood; Dopamine - blood