A butterfly needle, formally known as a winged infusion set, is a specialized medical instrument used for drawing blood samples or administering intravenous (IV) fluids and medications. This device is a modification of the standard straight needle, designed to offer distinct operational benefits in venipuncture procedures. Its construction provides enhanced control, which is useful when accessing veins that present a challenge for traditional collection methods.
Defining the Device and Its Advantage
The butterfly needle earns its name from the two flexible, plastic wings positioned at the base of the short, thin needle. These wings provide a secure grip point for the phlebotomist, allowing for precise placement and stabilization during insertion into the vein. The needle itself is typically smaller in diameter than standard needles, often ranging between 21 and 23 gauge, though sizes up to 27 gauge are available for the smallest veins.
The needle is connected to a thin, flexible tube, typically 8 to 15 inches long, which attaches to a vacuum tube holder or a syringe. This tubing provides a buffer, allowing the collection tube to be manipulated without transmitting movement to the needle tip inside the vein. This minimizes the risk of the needle shifting or the vein collapsing, which is the primary advantage over a rigid, straight needle system.
Specific Patient and Procedure Applications
The winged infusion set is the preferred tool in situations involving difficult venous access. This includes veins that are small, fragile, or prone to “rolling” away from the needle during a standard draw. Veins in the hands and wrists, for example, are often smaller and more superficial, making them ideal candidates for the butterfly system’s enhanced precision.
The smaller size and reduced discomfort make the device suitable for specific patient populations. Pediatric and geriatric patients often have smaller, delicate veins that require a gentler technique. Patients who experience anxiety or needle phobia also benefit from the smaller, less intimidating appearance and greater comfort of the butterfly needle.
Beyond blood collection, the butterfly needle is frequently used for short-term IV therapy, such as delivering hydration fluids or medications. The flexible tubing allows for patient movement during the infusion without dislodging the needle. This is useful for quick treatments where a traditional, rigid IV catheter is not necessary.
Considerations for Use and Limitations
While offering superior control, the butterfly needle has limitations related to its physical design. The smaller gauge and long, narrow tubing can increase the shear force on red blood cells, potentially leading to hemolysis. Hemolysis, the rupture of red blood cells, compromises the quality of the blood sample, leading to inaccurate test results and the need for a redraw.
This risk is pronounced when using the smallest sizes, such as 25 or 27 gauge needles. The slower flow rate inherent to the smaller bore means that collecting a large volume of blood is significantly slower than with a standard straight needle. This inefficiency makes the butterfly needle less practical for routine, high-volume phlebotomy procedures. Furthermore, the cost of a winged infusion set is generally higher than a straight needle and holder.