- Although injection techniques for avian patients are essentially the same as in other species, careful and efficient technical skills are required.
- All injections are best delivered by the smallest gauge needle possible due to the relatively thin, delicate skin of the bird.
- Intramuscular injections are typically administered into pectoral muscles along the mid-keel region. Hemorrhage is more likely to occur when injections are made into cranial pectoral musculature.
- Subcutaneous injections can be administered into the inguinal, axillary, or interscapular regions.
- In psittacine birds, intravenous injections are most commonly delivered into the right jugular vein and the basilic vein. The medial metatarsal vein may be more accessible in some large avian species.
- When intravenous injection is impossible, injectable euthanasia agents can be administered via the intracoelomic or intraperitoneal route in the unconscious or anesthetized bird.
The avian patient poses interesting and challenging dilemmas for delivery of injectable medications. Critically ill birds often cannot tolerate prolonged handling or sedation, therefore careful and efficient technical skills are required. Although most procedures used in small animals are easily adapted to birds, veterinary health professionals must also familiarize themselves with unique anatomic and physiologic features of the bird.
If a patient is not already being handled for tube feeding or is highly resistant to medications delivered by syringe, then parenteral drug administration can be utilized. Injectable drug delivery is also required when gastrointestinal motility is altered or if the desired medication is poorly absorbed from the gastrointestinal tract. Parenteral drug administration can be accomplished by intramuscular (IM), intravenous (IV) or intraosseous (IO), subcutaneous (SC), or in very rare instance, intracoelomic (IC) or intraperitoneal injections. The route of drug administration selected is often dictated by the drug preparations available. All injections are best delivered by the smallest gauge needle possible due to the relatively thin, delicate skin of the bird.
Parenteral drug administration provides the advantage of delivering a precise dose with the rapid development of therapeutic blood levels. Plasma drug levels generally peak seconds following IV administration, within 30-60 minutes after IM administration and in 60-120 minutes with oral routes (Ritchie 1990). Disadvantages of drug delivery via injection include stress induced by handling a metabolically compromised patient, and the irritation, necrosis or abscessation that may occur at the injection site with some medications. Local tissue reactions commonly occur when large quantities of drugs are injected, or when the formulation contains certain carriers such as propylene glycol or glycerol.
Intramuscular injections are typically administered into pectoral musculature along either side of the mid-keel region (Fig 1). Avoid the cranial portion of the pectoral muscles to prevent inadvertent injection into vasculature located in this region. Drugs injected into the leg muscles may be excreted by the kidneys through the renal portal system before reaching systemic circulation. The injection of nephrotoxic drugs into the legs is particularly dangerous and contraindicated.
To perform an intramuscular injection, wipe feathers away from the featherless tract (sternal apterium) along the ventral midline of the keel with isopropyl alcohol. Insert the needle a short angle (less than 30°) into the muscles. A short (less than 0.625-in or 1.588 cm), small-gauge (25- to 28-gauge) needle serves well in psittacine birds. See the LafeberVet video: Intramuscular Injections in Birds for additional information.
Subcutaneous injections can be administered into the inguinal, axillary, or interscapular regions. When selecting the latter site, avoid the dorsal neck due to the presence of the cervicocephalic air sac space. As a general rule, up to 20 ml/kg can be administered in one location, however remember that subcutaneous injections are poorly absorbed in the severely dehydrated patient or during shock.
Intratracheal injection provides a route for drug delivery to the lungs and airways. This route of administration can be used to deliver antifungal agents, like amphotericin B or clotrimazole, as well as emergency drugs like epinephrine and atropine during resuscitation efforts.
To perform a tracheal injection, select a water-soluble drug and a sterile, red rubber tube or similar tube of appropriate size OR a small-diameter, sterile, metal gavage tube. Volumes up to 2 ml/kg can be safely administered (Jenkins 1997). If the bird is awake, it should be manually restrained with the beak held open. A mouth speculum or gauze loops are necessary for psittacine birds. Quickly pass the tube through the glottis in the conscious patient or through the endotracheal tube in the anesthetized patient. Inject the medication into the trachea with some degree of force. If the patient is conscious, immediately release it afterwards allowing the bird to clear its throat and make cough-like sounds (Jenkins 1997).
Intravenous drug administration allows precise dosing and results in rapid systemic distribution of the therapeutic agent. Intravenous injections are most commonly delivered into the right jugular vein and the basilic vein (Fig 2), with the jugular vein being most accessible. Drugs can also be delivered less commonly through the medial metatarsal vein (Fig 3).
Crystalloid volumes of up to 10 to 15 ml/kg can be safely administered as a single fluid bolus, provided the bird is not critically anemic and repeat administration is not required. Place an intravenous catheter when fluids must be delivered relatively slowly or when ongoing vascular administration is required (Fig 4).
Vascular access can be virtually impossible during shock and in these cases intraosseous injection may be necessary. Fortunately absorption from IO catheters has been shown to be almost as rapid as IV administration (Kamiloglu 2008 ). Intraosseous injections are most commonly delivered into the distal ulna or proximal tibia using a 22-to-25 gauge hypodermic or spinal needle. Of course potentially pneumatic bones, like the humerus or femur, should be avoided. Provide sedation and analgesia to reduce pain associated with insertion and prevent movement.
Intradermal injection is rarely performed in the avian patient. Historically, tuberculin testing was performed in birds (Bernardelli et al 1990, Krejcí et al 1974), and more recently intradermal injections have been used in avian allergen testing research (Nett et al 2003, Colombini et al 2000, Macwhirter and Mueller 1998). Intradermal injections are also used for some infectivity studies in fowl (Swaggerty et al 2012, Ul Hassan et al 2012). In the studies by Colombini and Nett, birds (pigeons and Amazon parrots respectively) were anesthetized with isoflurane, and 0.02 ml of fluid was injected into the skin overlying the proventer (sternal) region with the use of a 30-gauge needle.
When intravenous injection is impossible, injectable euthanasia agents can be administered via the intracoelomic (IC) or intraperitoneal route. AVMA Guidelines (2013) state the bird should be unconscious or anesthetized in order for this technique to be considered humane. Although the technique for IC injection is essentially the same as for abdominocentesis, unlike paracentesis, when a needle is inserted into a fluid-filled space, an injection into the intestinal peritoneal cavity involves more of a potential space. The intestinal peritoneal cavity occupies either side of midline of the post-sternal abdomen (Ducker 1979), however the complexities of the avian peritoneal cavities also make it relatively easy to inject into the air sac space. The air sacs must be avoided because of the potential for respiratory compromise, irritation of the respiratory system, and delayed drug absorption.
To perform an IC injection, restrain the bird upright or in dorsal recumbency. Moisten the feathers on the ventrum with an alcohol swab and then part the feathers to expose a midline featherless tract. The caudal edge of the ventral sternum is visible as the cranial landmark and the pelvis is visible caudally (Taylor 2014). Insert a small-gauge needle just off midline. Some clinicians (Taylor 2014) recommend injection just left of midline (Figure 5). Injections can also be made just right of midline, to prevent inadvertent injection into the ventriculus. In tiny patients, injection into the intestinal peritoneal cavity–without puncture of intestinal loops—can also be facilitated by lifting the skin and thin body wall with atraumatic forceps (Taylor 2014). Often when using the IC route for euthanasia, the needle is directed craniad in an effort to deliver drug directly into the liver. Hepatic delivery of a nonirritating barbiturate or other approved solution makes the effect particularly rapid.
The intracoelomic route is contraindicated in birds with subcutaneous emphysema or air sac rupture since it is more difficult to avoid inadvertent injection of the air sac space.
The avian patient poses special challenges for delivery of injectable medications. Although the techniques involved are not unique to birds, special knowledge of avian anatomy as well as delicate, proficient technical skills are required. Depending on the species, the individual, and the clinical situation, injections can be delivered by intramuscular, intravenous, intraosseous, subcutaneous, intratracheal, or intracoelomic routes. Parenteral drug administration provides the advantage of delivering a precise dose when a rapid therapeutic response is necessary. Disadvantages include stress as well as the potential irritation or pathology that can occur at the injection site.