Injection techniques for drug administration and methods of restraint

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utterfly needle catheter over-the-needle the plunger until all air has been removed. Often, the syringe should be flicked first to ensure that air bubbles attached to the inner wall of the syringe are released. Following this, the needle guard is placed over the needle. In this way, the cone of the syringe is protected against contamination and needle injury is prevented so that the syringe can be safely transported to the patient or put aside (label for safety) for the time being. 11.1.2.4 Butterfly needles with extension tubing A butterfly needle is a needle with “wings” at both sides of its base, by which the needle can be held. The needle often has an extension tube with a cone at the end to which a syringe can be connected. This extension tube allows the syringe to be moved independently of the needle, giving both operator and patient more freedom of movement during the injection. This increases the chance that the needle remains in position (inside the blood vessel). Butterfly needles are therefore used in particular if: • the animal is difficult to restrain; • the injection takes longer, which increases the risk of movement and resistance; • irritating substances are to be administered. 11.1.2.5 Catheters Jos Ensink and Joris Robben 209 Catheters are often used instead of needles for IV (fluid) administration. A catheter can remain in place for several days (“long-term” catheter), but a catheter may also be applied for a single injection or for medications given IV over several hours (e.g. during surgery). Both long-term and short-term catheters should be well secured (adhesive bandage and/or stay sutures) to keep them in place (and intravenously). A catheter has the advantage that, once correctly in place, one can be sure that all injectables arrive strictly IV, even if the patient moves. A synthetic catheter causes less damage to the vessel wall than a metal needle, especially after a longer period of time in place. Easiest to insert are the so-called “over-the-needle” catheters. These consist of a synthetic catheter with an internal metal needle. The metal needle is hollow and has a sharp bevel that slightly exceeds the non-sharp tip of the catheter. At the other end, the needle has a transparent chamber in which blood can become visible once the needle has punctured a vein. The catheter can be fitted with small wings to secure it to the skin. Once the catheter is positioned in the vein with help of the internal needle, the needle is removed (Figure 11.4). Figure 11.4. An over-the-needle catheter, from the bottom upward: 1. the catheter as it comes out of the wrapping, with protective needle guard; 2.the catheter after removal of the needle guard; 3. the catheter alone; 4. the needle guard with transparent chamber alone.
210 administration set drip chamber Luer lock flow regulator air vent disinfection clipping Chapter 11 Injection techniques for drug administration and methods of restraint 11.1.2.6 Fluid administration sets Fluids for infusion are available in glass or synthetic bottles or plastic bags with penetrable stoppers, sealed with a protective cover. The solutions are usually administered through a fluid administration set. The set consists of a length of tubing with on one end a needle or spike that can be used to pierce through the stopper. The tubing is equipped with a drip chamber and an in-line flow regulator. The other end of the tubing ends in a special connector (for example a so-called “Luer lock” connection) to which a needle or catheter can be attached. The drip chamber is partially filled with fluid to function as a “buffer” when the bottle of bag is empty and air tends to fill the tubing. Furthermore, the speed of flow can be adjusted by counting the number of drops per minute/ second in the drip chamber. The flow regulator (usually an adjustable clamp or wheel that squeezes the tubing to a more or lesser extent) allows control of the flow speed. When glass or stiff plastic bottles are used negative pressure is built up during infusion, preventing the flow of solution. This is why an air vent has to be used with these types of bottles. Administration sets can have an air vent built in the spike. For non-vented sets separate tubing for air ventilation has to be used. Such an extension has a needle at one end that is pierced through the stopper, and a filter at the other end to prevent contamination of the solution. When fluids need to be given, the administration set should be set up ready prior to placement of the catheter or needle. The bottle or bag is hung upside-down above the level of the patient’s heart. This ensures the solution to flow into the animal, rather than the blood into the tubing after hooking up the set to the catheter or needle. When bottles requiring air ventilation are used in combination with a non-vented fluid administration set, the needle of a separate air vent system is pierced through the stopper, while the other end of tubing is positioned above the fluid level in the bottle. To spike the administration set with fluids, it is taken out of its wrapping and the flow regulator is closed (when the flow regulator is open after attaching the set to a fluid bottle or bag, both fluid and air bubbles will fill the system, making it difficult to free the tubing of air bubbles). Then, the needle or spike is pierced through the stopper (bottle) or connector (bag). The drip chamber is gradually filled by gently pinching it a few times, or by holding it horizontal if made of rigid plastic. Then the flow regulator is opened until all air has been expelled from the tubing. The end of the tubing has a protective cap that protects it against contamination. Sometimes, this cap needs to be removed in order to completely fill the drip tubing. 11.1.3 Practical application 11.1.3.1 Preparing the injection site Much debate surrounds the question whether it is necessary to disinfect the skin prior to IM or SC injections. The condition of the skin or coat plays an important role: injections through soiled skin (e.g. in case of diarrhoea) or dermal lesions carry an increased risk of infection, even after disinfection. In horses, it has been demonstrated that a rapid disinfection with alcohol without clipping leads to a significant reduction (± 70%) in the number of bacteria on the skin. Electrical clipping followed by disinfection leads to a reduction of over 90%. In horses, it is therefore considered good practice to disinfect the skin prior to IM or SC injections (clipping is only performed with a thick hair coat). Also in cattle, the injection site is best disinfected, unless this is impractical (injection of a group of animals; a poorly restrained or unrestrained animal). In pigs, such situations nearly always apply and injection sites are not disinfected. Prior to IM or SC injections in companion animals with a well-kept coat, clipping or disinfection is considered not necessary. Often, alcohol is used but this has merely a function of improving the view on the injection site by parting or smoothing the hairs. However, for IV injections, the injection site is always disinfected, and often clipped, in all species. Sometimes, clipping is necessary to make the vein visible for IV injection (e.g. dog, cat, thick-coated horse). If the risk of infection is to be as low as possible (e.g. intra-articular injections, long-term catheter) the skin should be clipped, cleaned and disinfected (like preparing a surgical field).
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