Needles and syringes
When administering injectable medication, the medical assistant must use the correct needle and syringe. Using the correct technique to uncap, recap, and switch needles is important for infection control. The following sections discuss needles, syringes, and the correct techniques to use when working with them.
Hypodermic needles
A hypodermic needle attaches to a hypodermic syringe. Hypodermic needles come with syringes or are packaged separately. The entire needle needs to remain sterile for the injection. It is important for the medical assistant to know the parts of the needle. The parts of a hypodermic needle include the following:
- Hub: Attaches or screws onto the syringe
- Hilt: Where the needle attaches
- Bevel: Slanted end of the shaft
- Lumen: Hollow space inside the needle; the size is indicated by the gauge number
Gauge and length
Each needle has two measurements: the gauge (G) and the length. The lumen size is indicated by the gauge and is given a numeric value. The higher the gauge number, the smaller the lumen. The thickness of the needle wall increases along with the lumen size. This means that an 18 G needle makes a larger hole than a 25 G needle. The 18 G needle has a thicker wall than the 25 G needle. As the gauge number increases, the needles bend more easily. Thicker-walled needles (smaller gauge numbers) are used for deeper injections. Thinner-walled needles (larger gauge numbers) are used for more superficial injections.
The medication’s viscosity is also an important factor when selecting the gauge of the needle. A medication with a syrupy thickness (high viscosity) would be harder to push out of a needle compared with a medication as thin as water. Using a wider lumen needle (smaller gauge number) would be better for thicker medications. Using a finer lumen needle (a larger gauge number) would be more appropriate for watery medications.
The needle length refers to the length of the shaft. The needle length used is dependent on the type of injection given and the size of the patient. The length of the needle for an intradermal injection is smaller than that used for an intramuscular injection. The length of an intramuscular injection needle for a 300-pound person would be longer than that for a 100-pound person. Knowing the length and gauge required for an injection are important information for the medical assistant.
Safety needles
Due to the Needlestick Safety and Prevention Act, safety needles are common in the ambulatory care setting. Safety needles are designed to reduce the risk of needlesticks after an injection. A passive safety needle is designed so that the needle is automatically covered after the injection. Passive safety needles are currently used with insulin pens (e.g., the BD AutoShield Duo pen needle). An active safety needle requires the healthcare professional to activate the safety device. These are most common for injections. Current active safety needles fall into two groups:
- Protective sheaths and hinged needle shields: The safety device is a sleeve over the syringe barrel or a hinged needle shield. These devices are moved over the needle after the injection. Once they are in place, the needle cannot be uncovered. The risk of needlesticks decreases if the safety device is activated with the hand holding the syringe.
- Retractable needles: After the injection, the healthcare professional activates a device that retracts the needle either into the syringe or into another chamber.
Hypodermic syringes
Hypodermic syringes attach to needles and hold the medication for the injection. They come in many sizes (e.g., 1, 3, 5, 6, 10, and 12 mL), but usually, the facility only stocks three or four sizes. The two parts of a syringe are considered to be the barrel and the plunger. Syringes can have either a Luer-Lok tip or a slip tip. Calibration marks are on the barrel of the syringe. It is important for the medical assistant to be able to read medication amounts in syringes.
Working with the needle and syringe
Syringes come packaged in different ways:
- A syringe can be packaged without a needle. A needle must be added to the syringe when giving an injection.
- A syringe may be packaged with a needle that is not attached. The unit must be assembled.
- A syringe and needle unit may come preassembled. Always tighten the needle on the syringe before using the unit.
The needle and syringe can be assembled with clean, ungloved hands.
When a syringe is packaged by itself, first open the syringe. When removing the syringe from the packaging, it is important not to touch the syringe tip to anything. The tip needs to remain sterile because it attaches to the needle. The syringe should be held until the needle is attached. As you are holding the syringe between your middle and ring fingers, use your thumbs and index fingers to open the needle package. It is important to hold down the packaging flaps to prevent contamination of the needle. Attach the syringe to the needle and lift the needle out of the package. The needle and syringe unit can be placed on the counter. The needle cover should remain on to protect the sterility of the needle.
When the needle and syringe are packaged together but not assembled, carefully open the packaging. Hold down the packaging flaps. Angle the contents so the syringe can be grasped without going over or touching the needle. Remove the syringe, then attach it to the needle. Remove the needle from the packaging. Once the syringe and needle are assembled, the unit can be placed on the counter.
When working with the plunger, only touch the section that remains outside of the syringe when the plunger is completely pushed in. Touching the plunger that goes inside the barrel could potentially contaminate the medication.
Uncapping and recapping needles
Never recap a needle that has been used on a patient. Needles can be recapped until they are used on a patient. As you prepare medication, you will need to uncap and recap the needle. It is important to maintain the sterility of the needle. If there is any doubt, consider the needle contaminated and replace it with a new one.
- To uncap: Hold the cover between the fingers and thumb of your nondominant hand. Hold the syringe with the fingers and thumb of your dominant hand. Pull your hands apart horizontally (side to side) in a smooth continuous motion.
- To recap: Use the one-handed scoop technique. Place the cover on a firm, flat surface. If the cover rolls, place a finger of your nondominant hand at the far end of the cover. This will keep the cover in place. Carefully insert the needle into the cover. If the needle touches the outside surface of the cover or any other surface, it is contaminated and must be replaced. Scoop up the cover and secure the cover onto the needle.
Switching needles
When switching needles, it is important not to give yourself a needlestick and to protect the sterility of the new needle. Several methods are used to switch needles. One method includes opening the new needle package. Hold the packaging flaps down with the index finger and thumb of your nondominant hand. With your dominant hand, place the syringe with the covered needle between the middle and ring fingers of your nondominant hand. Firmly grasp the covered needle in your palm. The syringe should be above the top of your hand. With your dominant hand, remove the syringe from the old needle and attach it to the new needle. Your nondominant hand should be holding both needles the entire time. Discard the old needle into the biohazardous sharps container.