4. Select and assemble the needed equipment.

5. Place the arm in a downward position to prevent back-flow. Apply a tourniquet three to four inches above the puncture site, just tight enough to be slightly uncomfortable. Ask the patient to make a fist. Do not allow the patient to make a very tight fist or to pump their fist since this can falsely elevate the potassium level. This makes the veins more palpable. Do not leave the tourniquet on for more than 1 minute. It may be necessary to release the tourniquet after vein selection and to reapply it immediately prior to the puncture. Check both arms. Always select the most suitable vein for puncture. The three main veins are the cephalic, median cubital, and basilic. Generally, the median cubital is the one of choice because it is well-anchored in tissue and will not roll or move when the needle punctures it. The median basilic, at the inner edge of the arm, may have tendency to roll and is near a main artery and nerve. This part of the arm is very tender. The cephalic vein also has a tendency to roll and the skin over it is often tough. Using the index finger, palpate the arm, feeling for the best vein. It should feel similar to an elastic tube.

6. If a vein cannot be found try the following suggestions.
a. Gently pat the site to enlarge the veins.
b. Massage the arm.
c. Wrap the arm in a warm towel.
d. Check both arms. Always select the most suitable vein for puncture. When selecting a vein, seek another site for puncture if any of the following conditions exist.
e. edema
f. burn
g. hematoma
h. I.V. (See notes at end of procedure for patients with IVs
i. blood transfusion (best to wait until transfusion is complete if possible)
j. cannula
k. pustules on the puncture site
l. vascular graft
m. mastectomy on side of puncture site
If another site is not available, consult the supervisor.

7. Scrub the site of the puncture with a 70% alcohol pad. Use a circular scrubbing motion, from inside to outside only. Cover a wide area around the selected site, 3 to 4 inches and scrub for at least 30 seconds. This may have to be repeated depending on the cleanliness of the patient. Cleansing the site prevents chemical or microbial contamination of specimen and patient. Do not touch this area again.

8. Let the area air dry. Do not blow on or fan the area. The alcohol should be allowed to dry to avoid hemolysis and/or burning sensation when the venipuncture is performed.