Critical care of avian patients (Proceedings)

Emergency critical care and subsequent nursing care can mean the difference between life and death for a beloved pet. Critical care is an integral part of emergency management of disease in zoological species. A high mortality rate is inherent in exotic animal emergency medicine. The nature of these species and the fact that they are fairly recently domesticated dictates that they hide their illness until they have decompensated. Owners need to be aware that their pet is in serious condition but by providing critical care, you provide them with the chance for their pet's recovery.

The statement that by the time the animal is showing signs of illness it is in critical condition was never truer than it is for avian patients. It is very important that owners be made aware that their pet is very sick and that it may decompensate at any time during your exam or treatment. It may only be possible to do one procedure at a time, giving the bird time to recover in between. If at any point during handling the bird is open mouthed breathing, stops struggling, seems dazed, develops a weak grip, or shuts its eyes longer than momentarily, put it down to recover. Oxygen cages or flow-by oxygen may help the patient recover. Anesthetic restraint may be administered to extremely stressed or fractious patients but evaluation must be kept to a minimum and requires monitoring of respiratory rate, effort, and heart rate during the entire anesthetic event. Birds can be intubated using an appropriately sized endotracheal tube, 2.5-4.0 I.D., by placing the tube in the glottal opening at the base of the tongue. Do not inflate the cuff as this may result in tracheal necrosis as the cartilaginous rings do not expand.

Hospitalization caging considerations 

Standard stainless steel hospital cages are acceptable for use when housing psittacine birds. An appropriately sized perch should also be provided if the animal is strong enough to perch. Incubators or other heated cages should be used for patients unable to maintain their own body temperature. Care must be taken to avoid placing electric cords, heat sources, or other dangerous items in reach of the psittacine patient as they are likely to chew on these. Avoid using galvanized metal objects or caging. Food and water should be made available at all times unless there is concern that the patient could lose consciousness at which time the water source should be removed.

Fluid administration

Intravenous (IV) catheterization of birds is possible using the jugular vein, the medial metatarsal veins, or the basilic veins. However, IV catheters placed in psittacine birds (parrots) are often removed prematurely by the patient. An intraosseous (IO) catheter can be placed in the distal ulna or the proximal tibia in birds. This should be performed in a sterile manner and the catheter should be taped and bandaged in place using a figure 8 wing wrap. A 3 cc syringe case can be fashioned into a catheter guard as psittacine birds will often chew on the catheter. Fluids can also be provided by subcutaneous (SQ) or IO routes. SQ fluids are administered either in the inguinal area using the fold of skin located where the leg meets the body or in the wing skin folds where the wings meet the body. Fluids given should be warmed prior to administration. Bolus fluids may be given IV or IO at a rate of 10-25 ml/kg over 5-10 minutes. LRS or NaCl 0.9% are most commonly given and may be spiked with 50% dextrose to create a 5% dextrose solution (add 1 ml of 50% dextrose to 10 ml fluids). Fluids with a dextrose concentration of >2.5% should not be given by SQ route. Fluids administered for more than one day should be supplemented with 0.1-0.2 mEq potassium per day. Maintenance fluid rates for birds are 40-69 ml/kg/day. Shock doses rise to 10 ml/kg/hr for 2 hours, then 5-8 ml/kg/hr until the patient is stable. If colloidal fluid therapy is indicated, Hetastarch at a rate of 10-15 ml/kg IV or IO per 8 hrs may be used. 

Basics of hospitalization care

Supplemental heat is very important as sick birds quickly lose the ability to thermoregulate. Providing an external heat source reduces the physiological stress on the animal during hospitalization care. Pediatric or veterinary incubators are the best means of providing supplemental heat and should be set at approximately 90-95 degrees F. Incubators come in a variety of sizes and may incorporate fluid pumps and oxygen delivery systems. Many times, used pediatric incubators that are in good working order may be obtained from human hospital surplus. Radiant heating lamps may be attached to cage doors or placed over aquaria to provide ambient heating when an incubator is unavailable. Do not allow the patient or potentially flammable materials to be in direct contact with the lamp as burns are possible. Heating pads and heating discs are good alternatives for providing supplemental heat for patients that are ambulatory and do not need constant thermal regulation. 

Birds tend not to eat what they are unfamiliar with so having the owner bring the bird's food from home is ideal if the bird is to be hospitalized. If the bird's regular food is unavailable, providing a seed mixture may encourage self-feeding. If the bird is not eating on its own, supplemental feeding is imperative. Several supplemental feeding diets are available and will provide complete nutrition to ill birds. The gruel must be administered by gavage tube directly into the bird's crop and should be warm (101-104?F). A metal ball-tip feeding tube is ideal. Make sure to palpate the tube in the crop to avoid infusing gruel into the trachea. The crop capacity varies with the size of the bird. In general, the average gavage feeding amount equals 2.5% of the birds body weight (0.025 x BW in grams = mls of formula per feeding). Feeding interval is generally 6 hours but may be longer or shorter depending on crop emptying. Make sure to watch the oral cavity as the food is administered to check for over-filling.

Nutritional support must be provided to hospitalized patients, especially those with high metabolic rates where anorexia results in cachexia rapidly. The caloric requirements of the patients must be calculated and those requirements met on a daily basis through self-feeding or supplemental feeding. Metabolic rates are measured in kilocalories per day (kcal/day). The basal metabolic rate (BMR) takes into account a species coefficient (K) based on the animal's metabolic rate. Once the BMR is calculated, the maintenance energy requirement (MER), the metabolic rate based on activity, can be determined by multiplying the BMR by the activity level of the patient (1-2, 1.5 for convalescing animals, 2 for growth).

• BMR kcal/day = K x Weight kg (0.75)

• MER kcal/day = 1.5 x BMR

• K values

• passerines = 129

• non-passerines = 78

Once the number of kilocalories needed for MER are determined, the amount of food needed to meet that requirement can be calculated. The best way to determine if a patient is receiving appropriate nutrition is to weigh the patient daily on an accurate gram scale prior to assisted feeding or medication administration. Supplemental feeding can then be adjusted as appropriate.

Cpr and euthanasia

Zoological species presenting in critical condition have a high mortality rate due to the nature of their illnesses, the advanced nature of the emergency when clinical signs are first observed, and the speed with which their condition declines. Respiratory resuscitation, if performed when respiratory arrest is first observed, is often successful and should be the first component of cardiopulmonary resuscitation (CPR). If at all possible, the patient should be immediately intubated and ventilated. If intubation is not possible, then artificial respiration may be performed by mouth to face respiration. Most zoological species maintained as pets are small enough that the handler's mouth will cover the patient's nose and mouth. Consideration must be given to the zoonotic potential of the patient before this technique is used. Small puffs of air are generally sufficient to inflate the patient's lungs. Patients that are showing decreased respiration but that are not in full arrest will benefit from oxygen therapy delivered by mask. Air sac cannulation of birds is an option for providing artificial ventilation or oxygen therapy when intubation is ineffective or unavailable. With the bird in lateral recumbency and the leg pulled cranially, a small incision is placed just caudal to the thigh and the body wall is punctured. A breathing tube is then introduced into the body cavity and air sac. IV or IO emergency drugs are administered similarly to their use in domestic pets. If vascular access is unavailable, then drugs may be administered via endotracheal tube directly into the lungs. If cardiac arrest develops, cardiac compressions must be given at a rapid rate. Compression of the body wall over the location of the heart will compress the heart and circulate blood. Compressions in a bird should be done with the bird in dorsal recumbency while the keel is compressed towards the spine.

Euthanasia is the preferred or elected treatment for some zoological species presented for critical care. Vascular access by IV or IO routes allows for the routine administration of euthanasia solution. Intracoelomic injections in birds are contraindicated due to the air sac system. Whenever possible, the patient is placed under general anesthesia prior to euthanasia to minimize stress and discomfort.

Resources

BSAVA Manual of Exotic Pets, 4th ed. Meredith A. and Redrobe S, eds. 2002. Iowa State University Press, Ames, IA.

Manual of Avian Practice. Rupley A.E. 1997. W.B. Saunders Co., Philadelphia, PA.

The Veterinary Clinics of North America – Exotic Animal Practice; Common Procedures. Griffin C. ed. 2006. W.B. Saunders Co., Philadelphia, PA.

The Veterinary Clinics of North America – Exotic Animal Practice; Critical Care. Rupley AE. ed. 1998. W.B. Saunders Co., Philadelphia, PA.

Avian Medicine and Surgery in Practice; Companion and Aviary Birds. Doneley B. 2011. Manson Publishing Ltd., London, UK.