Avian critical care (Proceedings)

It is a clinical challenge when veterinarians have to administer therapeutic procedures to pet avian patients. The thoughtful use of therapeutic procedures on a debilitated patient is often correlated to the success or failure of treating a patient.

The initial phase of evaluating a patient's health is through a rapid external physical examination. If the patient appears to be severely debilitated or getting worse the bird should be "put down" and placed in a critical care unit. Any antibiotic, chelation agent or fluid therapy should be initiated prior to the patient's placement into the incubator.

Fluid Therapy

If it is determined the patient can withstand the stress of handling and treatment then fluid therapy may be initiated. Normosol or Lactated Ringers Solution can be administered through the following routes: subcutaneous, intravenous, intraosseous, orally and through the cloaca. Anatomic sites commonly used for IO catheter placement include the distal ulna (larger birds), proximal ulna, proximal tibiotarsal bone and lateral femur (young and small birds). Placement of the IO catheter begins with proper site preparation, similar to epithelial preparation for an IV catheter. A 22-gauge, 1½" spinal needle is the catheter of choice in most psittacine cases although any size needle may be used, provided that a stylet is inserted into the needle prior to placement of the IO catheter into the medullary cavity of the bone.1 When the IO catheter is placed in the distal ulna, the distal wing tip is flexed and the needle is inserted at a 45 to 60° angle, and this angle is reduced once the catheter enters the cortex.2 The needle should be advanced to the hub, stylet removed and the catheter flushed with heperized saline. The catheter is capped with a PRN and managed as an IV catheter. Intraosseous catheters require more maintenance than an IV catheter and should be flushed 6 to 8 times a day to maintain patency. Subcutaneous fluid therapy is not an effective method of rapid restoration of circulatory fluid volume.3 Adding hyaluronidase (Wydase, Wyeth-Ayerst Pharmaceuticals, Philadelphia, PA) to lactated Ringer's solution (LRS) for SC fluid administration has been recommended as a method to increase the absorption rate of the fluid into the circulatory system.1

When determining the dehydration deficit of a psittacine patient, the veterinarian must estimate the percentage of deficit prior to calculating replacement fluid volumes.1 Parameters applied to measure dehydration status in psittacine species include skinfold elasticity, corneal moisture, appearance of the globe and packed cell volume.1 Dehydrated psittacine chicks have wrinkled and reddened skin, with a sunken face and prominent eyes.4 It is generally believed that in most cases of severe trauma or disease a 5% to 10% dehydrated status should be estimated for the avian patient.1 The estimated deficit should be replaced over a 48 – 72 hour period.1 The recommended daily fluid maintenance formula for psittacine species is 100 ml/kg/day, and baby birds consume 2 to 3 times the maintenance fluid levels as adult patients.1 Recent recommendations to compensate for tissue fluid loss are a crystalloid (eg, LRS) 10 ml/kg + colloid (eg, hetastarch) at 5 ml/kg increments. The crystalloid/colloid combination given at 1 to 2 bolus infusions will generally raise the blood pressure to greater than 90 mm Hg systolic. Fluids should be warmed before administration and bolus fluids can be given with relative safety IO or IV over a 3 – 5 minute period.1 Once the fluid deficit is replaced and the bird is eating and drinking normally for 2 or 3 days, the maintenance hydration therapy can be discontinued.1

Fluids therapy may be replaced through subcutaneous, intravenous or intraosseous administration. Subcutaneous fluid replacement can be achieved using a 26 or 25 gauge needle attached to a syringe filled with a warmed crystalloid or colloidal agent. The sites usually preferred for subcutaneous administration are the featherless inguinal and/or axillary regions of most avian species. Intravenous catheters are placed in the jugular vein of larger birds and median metatarsal of smaller companion avian species. The distal ulna and proximal tibiotarsal bone are the recommended sites for IO catheter placement. Although IO catheter placement is easier in smaller birds, these catheters require more maintenance to prevent plugging. Intraosseous catheters have a similar delivery to IV catheters and are much easier to place, especially in smaller species.

Nutritional Supplementation

Species specific or group specific diets have been formulated. Examples of group or species specific diets are parrot, cockatiel, parakeet, canary/finch, lori and mynah/softbill. Feeding group/species specific diets to breeding birds may increase clutch size, increase fertility of breeding birds, increase the number of clutches per year, provide better hatchability and healthier chicks that mature faster than birds fed lower quality diets. With the advent of powdered hand feeding formulas, avian nutrition has arrived in the 21st century. Homemade batch formulas no longer need to blended in order to adequately feed domestic raised companion bird species. Hand feeding formulas are as easy to make as instant pancake mix – add warm water to the powder. With the instructions on the box, the amount needed can be reconstituted without waste or storage. All unused formula should be discarded to prevent bacterial contamination. Also with warm water being used and the hand feeding formula being "ready to eat" the need to microwave the formula is no longer necessary. By eliminating the microwave process the likelihood of young birds sustaining thermal crop injuries is drastically reduced. There currently is debate on how often and when to feed young birds. No matter how advanced avian nutrition becomes is still pales to properly fed parent raised birds. If you look at birds being fed by parents the crop is always full. This is completely opposite of the hand feeding techniques advocated by aviculturists and veterinarians over the last 25 years. It is recommended that birds should be fed approximately 10cc/100 grams body weight when their crop empties. Most hand feeding owners will come very close to following the rule of feeding on an empty crop. We have noticed that certain bird species, in particular macaws, will often become stunted using this method of hand feeding. There are specially formulated macaw formulas, and they should be used but also macaws seem to thrive when their crop is maintained full and allowed to empty overnight. Hand fed birds should be weighed daily, in the morning when the crop is empty before the first feeding. If the bird is not gaining weight the formula may contain too much water, is diluted with other ingredients, the bird is not fed often enough or is not getting enough food at each feeding. Another problem with underdeveloped birds is that owners will "weaken" the formula to aid in digestion of a slow moving crop. Weakening the formula only compounds disease problems a young bird may have by reducing the nutritional intake needed by the rapidly growing animal. The needed nutrients are immense for a young bird and reducing the food intake by diluting the formula will have deleterious effects on the immune system.

As important as fluid replacement, nutritional supplementation must be considered for the debilitated avian patient.1 To calculate the nutritional requirements for the avian patient, the following formula can be used:1

Calculate basal metabolic rate (BMR):

BMR is K(W0.75)

K = kilocalories (a constant) for 24 hours

K = 78 for psittacines

W = weight of the bird in kilograms

2. Calculate maintenance:

1.5 X BMR

3. Adjust maintenance requirements for stress (Table 1)

4. Kcal required/day ÷ al/ML formula = amount of formula in mL required per day

Table 1. Adjustments to Nutritional Maintenance for Stress (As Multiples of Maintenance Energy Requirements).1

Birds that are extremely ill may need enteral feeding support. There are products available through the Lafeber Company, Cornell, IL, that provides this critical care nutritional requirement. Critical Care®, Nutri-Support® and Carbo-Boost® comprise the line up of the Lafeber avian critical care products.

When treating the avian patient, environmental support has a significant impact on the success of many cases.1 Environmental support can be classified as temperature/humidity control (in most cases heat), oxygen supplementation/administration and nebulization.1 There are many avian intensive care units (ICUs) on the market, but the veterinarian should carefully examine the clinic's needs before purchasing this piece of equipment.1 When comparing avian intensive care units, cheaper is not always better.1 Important features that improve a unit's performance are digital temperature and humidity control, ease of cleaning /disinfecting and durability.1

Air Sac Breathing Tube

An air sac breathing tube is sometimes needed to regain an appropriate air flow into the lower respiratory system if the mouth, glottis or trachea is obstructed.1 An endotracheal tube (relative to the patient's size) is placed in the caudal thoracic air sac in the area of the last 3 or four ribs, just dorsal to the dorsal edge of the pectoral muscle.1 The tube is placed through a stab incision that has been bluntly dissected through to the caudal thoracic air sac.1 The tube is secured by inflating the cuff within the coelomic cavity (if the tube has a cuff) or suturing a tape butterfly, which has been applied to the tube, to the skin.1 It has been the author's experience that to anesthetize or administer oxygen using an abdominal breathing tube requires a higher percentage of anesthetic agent plus an increased flow rate of oxygen.

Performing therapeutic techniques on pet avian species often means the difference in life and death. Knowing the proper techniques and formulas required for avian patients using the proper equipment will result in treatment successes.

References available upon request.