In phlebotomy, your tools are just as critical as your technique. Lesson 3 covers the comprehensive list of supplies required for a standard venipuncture, the mechanics of the vacuum system, and the critical “Order of Draw.”

1. The Blood Collection System

Most modern facilities use the Evacuated Tube System (ETS). It is a closed system that minimizes exposure to bloodborne pathogens. It consists of three primary components:

• • The Multi-Sample Needle: Double-pointed needles. One end enters the patient, while the other (covered by a rubber sleeve) pierces the tube stopper.

  • The Tube Holder (Adapter): A plastic cylinder that holds the needle and allows for the easy insertion and removal of vacuum tubes.

  • Evacuated Tubes: Color-coded glass or plastic tubes containing a pre-measured vacuum that automatically draws the exact volume of blood needed.

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2. Needle Anatomy and Gauges

Selecting the right needle size prevents hemolysis (the rupturing of red blood cells) and patient discomfort.

• Bevel: The slanted tip of the needle. It must always face up during insertion.

• Shaft: The long, slender portion of the needle.

• Lumen: The hollow internal space of the needle.

• Gauge (Ga): Refers to the diameter of the lumen.

  • The larger the gauge number, the smaller the needle diameter.

  • 21-Gauge: The standard needle for routine adult venipuncture (usually green cap).

  • 22-Gauge: Used for smaller or more fragile veins (usually black cap).

  • 23-Gauge (Butterfly): Used for scalp veins, hand veins, or pediatric patients (usually winged infusion sets).

3. Additives and the “Order of Draw”

Each tube contains specific additives designed to either prevent clotting (anticoagulants) or encourage it (clot activators). To prevent cross-contamination of additives between tubes, you must follow the Clinical & Laboratory Standards Institute (CLSI) order:

4. Essential Ancillary Supplies

Beyond the needle and tube, your tray must be stocked with these items for every draw:

• Tourniquet: Applied 3–4 inches above the puncture site. It restricts venous flow to make veins more prominent but must not be left on for more than 60 seconds to avoid hemoconcentration.

• Antiseptics: 70% Isopropyl Alcohol is the standard. For blood cultures, Chlorhexidine Gluconate or Povidone-Iodine is used.

• Gauze Pads: Used to apply pressure post-withdrawal. Cotton balls are discouraged as the fibers can stick to the clotting site.

• Sharps Container: A puncture-resistant, leak-proof container for immediate disposal of needles. Never recap a needle.

• Gloves: Non-sterile, powder-free nitrile or vinyl gloves (avoid latex due to allergies).

5. Specialized Equipment: The Butterfly Set

The Winged Infusion Set (Butterfly) provides greater flexibility. It features a short needle attached to a long, thin plastic tube.

Critical Rule: If using a butterfly set to draw a Light Blue (Citrate) tube first, you must use a “Discard Tube” to prime the tubing. This clears the air from the line so the vacuum tube fills to the correct 9:1 blood-to-additive ratio.

6. Tourniquet Application & Hazards

Proper application is a balance of pressure.

• Too Loose: Veins will not fill.

• Too Tight: Obstructs arterial flow, causing the arm to turn numb or white.

• Prolonged Use: Can lead to petechiae (small red spots) or altered lab results due to fluid shifting out of the blood.