A butterfly needle is a specialized device used for drawing blood or delivering intravenous fluids. It consists of a thin, small-gauge needle attached to flexible plastic tubing and features two plastic “wings” for better grip and stability. The design makes it the preferred tool for venipuncture in patients with small, fragile, or difficult-to-access veins, such as those found in children or older adults. The shorter needle length and added control allow for a shallower, more precise insertion, reducing patient discomfort and the risk of vein damage compared to a traditional straight needle.
Equipment Preparation and Site Assessment
Before approaching the patient, all necessary supplies must be gathered and organized for a smooth procedure. This includes the appropriate gauge butterfly needle assembly, tube holder, collection tubes, antiseptic wipes, sterile gauze, a tourniquet, and a sharps container. Confirm patient identification against the laboratory requisition to ensure the correct tests are performed on the right person.
Select a suitable venipuncture site, which is often a vein in the hand or the antecubital fossa of the arm. Apply a tourniquet three to four inches above the chosen site to impede venous flow, causing the vein to engorge. Palpate the selected vein to assess its size, direction, and depth, ensuring it is a firm, straight target.
Clean the site thoroughly with an antiseptic solution, typically a 70% isopropyl alcohol pad. The cleansing motion must start at the center of the puncture site and move outward in a concentric, circular pattern to push contaminants away. Allow the site to completely air-dry before the puncture; failing to allow it to dry can introduce bacteria or contaminate the sample.
Insertion Technique and Flash Confirmation
Unwrap the butterfly needle and attach it to the tube holder or adapter. Hold the flexible wings between the thumb and index finger, ensuring the needle’s bevel is facing upward. Stabilize the vein by gently pulling the skin taut just below the intended insertion site with the non-dominant hand.
Insert the needle into the vein at a shallow angle, typically between 10 and 15 degrees, though sometimes up to 30 degrees for deeper veins. This low angle is a defining feature of the butterfly technique, allowing for entry into superficial veins without passing through the vessel. A successful entry into the vein is confirmed by the appearance of a small amount of blood, known as “flash,” visible in the clear plastic tubing closest to the needle. Once flash is seen, gently advance the needle slightly further, about one to two millimeters, to fully secure its position within the vein lumen.
Blood Collection and Managing the Order of Draw
Following successful insertion and flash confirmation, the blood collection process begins by attaching the first vacuum collection tube to the hub at the end of the tubing. The tube is pressed firmly onto the hub’s inner needle, which punctures the rubber stopper and allows the tube’s internal vacuum to draw blood. Use the hand holding the wings to maintain the needle’s position, preventing it from shifting within the vein.
A strict sequence, known as the “Order of Draw,” must be followed when collecting multiple tubes to prevent cross-contamination from the various chemical additives within the stoppers. Because butterfly tubing contains air, a discard tube must be drawn first when a coagulation tube is required to clear the air from the line and ensure the proper fill volume.
Subsequent tubes follow this sequence:
- Blood culture bottles
- Light blue-top tubes (coagulation tests)
- Serum tubes (red or gold tops)
- Tubes containing heparin (green tops)
- EDTA tubes (lavender or pink tops)
- Tubes for glucose testing (gray tops)
As each tube fills and is removed, gently invert it a specified number of times to mix the blood thoroughly with the additive. This mixing prevents clotting or ensures proper preservation. After the last tube is collected, release the tourniquet before withdrawing the needle to restore normal blood flow and reduce bruising.
Needle Removal and Safety Disposal
Place a piece of clean gauze over the insertion site, taking care not to press down yet. Remove the butterfly needle from the vein in one smooth motion, pulling it straight out at the same angle it entered. Immediately upon withdrawal, apply firm pressure to the venipuncture site with the gauze to prevent a hematoma from forming under the skin.
Immediately activate the butterfly needle’s built-in safety mechanism. This mechanism, which may involve sliding a sheath or retracting the needle, must be engaged while the device is still close to the patient’s arm, rendering the contaminated sharp harmless. This action is necessary for preventing accidental needlestick injuries to the collector or others handling the waste.
Discard the entire butterfly needle assembly, including the needle and attached tubing, directly into a designated, puncture-resistant sharps container. Recapping the needle is prohibited due to the risk of accidental puncture. Ensure the patient continues to apply pressure to the site until bleeding stops, and apply a bandage if needed.