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Avian critical care (Proceedings)

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Apr 01, 2010

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.