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A clinical blood test is one of the list of standard manipulations for examining patients for the purpose of prevention or treatment. It allows you to evaluate the amount of hemoglobin, erythrocytes, leukocytes, platelets, to identify a color index. Blood sampling is carried out in only two ways – from the ring finger or from a vein. A needle or butterfly catheter is used to collect venous blood. What you need to know about medical instruments, what are its varieties and how to use a butterfly needle correctly?
What you need to know about the butterfly needle?
The butterfly needle is a standard medical needle to which a catheter is attached. In practice, only two types of needles are used – hollow and surgical. “Butterfly” belongs to the first category. It can be used to perform injections, collect/transfer samples and biological samples. Most often, the needle is used to collect venous blood from children and patients with thin veins. The tubes are made from austenitic stainless steel of one of the types that are listed in the relevant government documentation.
The production of medical instruments is strictly regulated by the state in order to ensure maximum safety and quality. The needles themselves are used in pediatrics, some intensive care units, veterinary medicine and gerontology (the science of aging of all living organisms).
A catheter is a medical instrument in the form of a tube, with the help of which the vessels are connected to the external environment for subsequent emptying. A soft catheter is attached to the butterfly needle. It is made of plastic materials like plasticized PVC or rubber. For the “butterfly” use vascular catheters with venous cannula. A cannula is a hollow soft tube that is inserted into the internal cavity of the human body. The catheter provides not only blood sampling, but also the introduction of drugs into the bloodstream or detoxification.
Absolutely all catheters require additional fixation. They are attached to the skin with plasters, suture material or special fixatives. The cannula is equipped with a flexible retainer (made of slightly colored polyethylene), which visually resembles the wings of a butterfly. Because of this similarity, the instrument got its name. The color of the retainer is not chosen for ethical reasons, but to indicate the size of the needle. Size range of needles: 18, 19, 21, 22, 23, 25, 27. Each number is assigned a specific shade of the palette, which helps doctors and nurses to quickly navigate the tools. To avoid confusion, the size of the needle is marked on the wings of the latch and additionally indicated on the sterile individual packaging.
| Size (G) | Fixer tint | Inner diameter (mm) | Flow rate (ml/mm) |
|---|---|---|---|
| 18 | Pink | 1,2 | 60 |
| 19 | Yellow | 1,0 | 42 |
| 21 | Green | 0,8 | 21 |
| 22 | Black | 0,7 | 11 |
| 23 | Blue | 0,6 | 5 |
| 25 | Orange | 0,5 | 3,2 |
| 27 | Gray | 0,4 | 2,5 |
What is a luer adapter?
A luer adapter is one of the components of a butterfly needle. Visually, it resembles a container for collecting, transporting and storing biological materials. One part of the device is a luer connector. With it, the adapter is connected to the catheter holder. On the modern market, you can find two variations of the device for blood sampling – with a luer adapter or a holder-holder. Luer allows you to perform several manipulations at once – take blood for analysis, conduct an intravenous injection, attach a needle to the system for infusion of solutions.
The second part of the device is a needle for piercing a vacuum tube. It is closed with a tight rubber cap, which prevents blood from splashing during sample extraction and transportation. All luer adapters are supplied in individual cases with an information label and perforations for visual inspection.
Advantages and disadvantages of a medical instrument
The strength of the butterfly needle is its versatility. It is suitable for taking biological fluid from patients of any age category. It is even used to diagnose the blood of newborns or older babies, if the amount of blood received by the lancet from the heel is not enough. Strong fixation of the catheter greatly simplifies the task for both the patient and the doctor or nurse. The medical staff will be able to easily and accurately obtain blood from even the most active and frightened patients. The advantages of the needle include minimal tissue trauma. Compared to conventional double-ended needles or vacuum tubes, the risk of nerve damage from butterfly needles is much lower.
What are the disadvantages of a butterfly catheter? The first thing you should pay attention to is the size of the needle. It is much smaller than a standard double ended blood collection needle. This increases the risk of cell damage. Platelets can simply stick together, and red blood cells can collapse. To avoid this, the medical worker must correctly select the size of the needle and strictly follow the rules for taking biological material. The disadvantages include the high cost of butterfly needles, pressure reduction and “runaway” of the vein during the procedure.
Another disadvantage is the relatively slow blood flow. The smaller the needle is in the vein, the faster the body can recover and recover from stress (even minimal). When blood is taken with a butterfly needle, the liquid passes through the cannula rather slowly, which increases the residence time of the needle in the vessel. As a result, more blood may be required to fill the entire catheter tube, including the dead space. Some nurses use an empty vacuum tube to fill the “dead space” and then dispose of it.
If the amount of biological fluid received is still not enough, the medical officer performs a second venipuncture. He once again pierces the wall of the venous vessel, inserts a needle and draws blood a second time.