Antecubital vein location varies slightly from person to person; however, two basic vein distribution arrangements referred to as the “H-shaped” and the “M-shaped” patterns are seen most often. The “H-shaped” pattern is so named because the most prominent veins in this pattern- the cephalic, cephalic median, median basilic, and basilic veins- are distributed on the arm in a way that resembles a slanted H. The most prominent veins of the M pattern- the cephalic, median cephalic, median basilic, and basilic veins- resemble the shape of an M. The H-shaped pattern is seen in approximately 70% of the population.
Factors in Vein Selection: Select the vein carefully. The brachial artery and several major nerves pass through the antecubital area. Accidental artery puncture and nerve injury are risks of venipuncture. Prioritizing veins can minimize the potential for accidental arterial puncture and nerve involvement. Typically, a tourniquet is used to aid in the selection of a vein unless specific tests require that a tourniquet not be used. A tourniquet is not necessary if veins are large and easily palpated. However, if only the basilic vein is visible without a tourniquet, one must be applied so the availability of safer veins (e.g. median and/or cephalic) can be assessed. Palpation is usually performed using the index finger. The collector’s thumb should not be used to palpate because it has a pulse beat. In addition to locating veins, the palpation pressure helps to differentiate veins from arteries, which pulsate, are more elastic, and have a thick wall.
Accidental Arterial Puncture: If during the procedure accidental arterial puncture is suspected (e.g. rapidly forming hematoma, rapid filling tube, and bright red blood), discontinue the venipuncture immediately. Remove the needle and apply direct forceful pressure to the puncture site for a minimum of 5 minutes until active bleeding has ceased. The nursing staff and physician must be notified and the incident documented according to institutional policy.
Consult with supervisory personnel to determine the suitability of the suspected arterial specimen for testing. If the specimen is acceptable it must be annotated that the specimen was an arterial specimen. In some cases different normal reference intervals are assigned to arterial blood. This information must be conveyed to the caregiver through Meditech Specimen Collection comment and Test Result comments.
Nerve Injury: If the patient feels a shooting, electric-like pain, or tingling or numbness proximal or distal to the venipuncture site, terminate the venipuncture and remove the needle immediately. Repeat the venipuncture in another site with a new sterile needle if needed. Document the incident and direct the patient to medical evaluation if indicated.
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