When we want to draw blood and the regular straight needle is not ideal we use the butterfly needle for this job , the butterfly needle is indicated in some situations as when the patient is anxious , can't stay still , to allow the ability of movement during the drawing process and it is specially used for patients with deep or thin veins.
The butterfly needle differs from the straight ordinary needle in some points , as butterfly needle is shorter having rubber wings on both sides to provide a good grip during handling and at the end it is connected to the collecting tubes.
Butterfly needles comes in different gauges 21 , 23 , 25 where here by increasing gauge number the diameter decreases , but choosing the right gauge for a specific patient follows some guidelines
- Size of patients veins: higher gauge needles work better for pediatric or geriatric patients in many cases. but, care should be taken to avoid too much vacuum when drawing or pressure when infusing as it can have harmful side effects and even render a sample useless.
- Speed of infusion or draw: thinner needles move less fluid that thicker needles. Depending on time requirements or the equipment and tubing used, particular butterfly needle sizes might be required.
- Specific medication requirements: some medications are thicker and more viscous. This requires a larger diameter needle to properly infuse the medication without causing complications with clotting or pressure in the loop.