Venipuncture Equipment & Technique

Venipuncture is the core skill of phlebotomy and the largest content area on the NHA CPT exam (32%). Mastering the equipment, vein selection, and step-by-step technique is essential.

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Blood Collection Systems

1. Evacuated Tube System (ETS) — Primary Method

The ETS is the most commonly used blood collection system. Components include:

Advantages: Closed system reduces exposure risk, tubes fill automatically, consistent fill volumes, multiple tubes collected with one venipuncture.

2. Winged Infusion Set (Butterfly Needle)

Critical Note for Blue-Top Tubes: When using a butterfly set, a discard tube (plain red or blue top) must be drawn first to fill the dead space in the tubing. This prevents under-filling the first tube, which is especially important for coagulation tests (light blue top) where the blood-to-anticoagulant ratio must be exact.

3. Syringe Method

Important: When transferring blood from a syringe to evacuated tubes, use a syringe transfer device (blood transfer device). Do NOT remove the tube stopper and pour — this increases exposure risk and can cause hemolysis.

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Needle Selection

Remember: A lower gauge number = larger bore (larger needle opening). A 16-gauge needle is much larger than a 25-gauge needle.

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Vein Selection

Primary Venipuncture Site: Antecubital Fossa

The antecubital fossa (inside of the elbow) contains the three primary veins used for venipuncture:

Sites to AVOID

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Venipuncture Technique — Step by Step

Step 1: Preparation

• Verify patient identity (two identifiers)
• Review requisition and select correct tubes (order of draw)
• Assemble equipment and check expiration dates
• Position the patient (seated or supine)

Step 2: Apply Tourniquet

• Apply 3-4 inches above the intended puncture site
• Tight enough to impede venous flow but NOT arterial flow
• The patient should still have a radial pulse
• Maximum tourniquet time: 1 minute — release and reapply after 2 minutes if needed

Step 3: Select the Vein

• Palpate using your index finger (not your thumb — thumb has its own pulse)
• A vein feels like a bouncy, resilient tube that rebounds when pressed
• An artery pulsates — never puncture a pulsating vessel
• A tendon feels hard and cord-like and does NOT rebound

Step 4: Clean the Site

• Clean with 70% isopropyl alcohol in a circular motion from center outward
• Allow to air dry completely (30-60 seconds) — wiping or blowing on the site recontaminates it
• Do NOT repalpate after cleaning — if you must, clean again

Step 5: Perform the Venipuncture

• Anchor the vein by pulling the skin taut below the puncture site with your non-dominant hand
• Insert the needle at a 15-30 degree angle, bevel UP
• A "flash" of blood in the tubing (butterfly) or tube indicates successful entry
• Push the first evacuated tube onto the needle inside the holder
• Allow the tube to fill completely by vacuum

Step 6: Fill Tubes in Order of Draw

• Follow the correct order of draw (see Section 3.2)
• Gently invert tubes with additives immediately after filling (do NOT shake)
• Release the tourniquet when the last tube begins filling (or within 1 minute of application)

Step 7: Remove the Needle

• Place gauze over the puncture site (do NOT press until needle is removed)
• Remove the needle smoothly at the same angle of insertion
• Immediately activate the safety device on the needle
• Apply firm pressure with gauze for 3-5 minutes (longer for patients on anticoagulants)

Step 8: Label Specimens

• Label tubes at the bedside with:
  • Patient's full name
  • Date of birth or medical record number
  • Date and time of collection
  • Phlebotomist's initials
• NEVER pre-label tubes — labels are applied only after confirming the patient's identity and completing the draw

Step 9: Apply Bandage and Dispose

• Apply adhesive bandage or wrap after bleeding stops
• Dispose of needle and holder in sharps container
• Ask the patient if they feel okay before leaving

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Tourniquet Application — Best Practices

The tourniquet is a critical tool in venipuncture, but improper use can significantly affect specimen quality and patient safety.

Proper Tourniquet Technique

• Apply 3-4 inches (7.5-10 cm) above the intended puncture site
• Use a flat tourniquet — avoid rolling or twisting which creates a tighter, more uncomfortable band
• The tourniquet should restrict venous flow (blood returning to the heart) but NOT arterial flow (blood flowing to the hand)
• Check the radial pulse — if absent, the tourniquet is too tight and must be loosened
• Request the patient to make a gentle fist (do NOT pump the fist, which can falsely elevate potassium)

Effects of Prolonged Tourniquet Application (Hemoconcentration)

If the tourniquet remains on longer than 1 minute, blood begins to pool and fluid shifts into surrounding tissue, causing hemoconcentration:

Key Rule: If the tourniquet has been on for more than 1 minute, release it for 2 minutes before reapplying to allow blood flow to normalize.

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Alternative Venipuncture Sites

When the antecubital veins are not accessible, the following alternative sites may be used:

Important: Drawing blood from foot or ankle veins requires physician authorization in most healthcare facilities due to increased risk of deep vein thrombosis (DVT) and infection.