Abstract
Introduction
In recent years, surgery in pet avian species has become more and more sophisticated. Development of newer gaseous anesthetics has made complicated internal work relatively routine. The purpose of this paper is to describe a few of the procedures which are now performed in a progressive pet avian practice.
Isoflurane Anesthesia
The anesthetic for routine and involved surgical procedures is a new gaseous anesthetic, isoflurane (Forane® - Ohio Chemical). We consider this product the anesthetic of choice in pet avian medicine. First used and studied in birds by Harrison, this gaseous anesthetic gives excellent surgical control. The product is now used extensively in humans because of problems with delayed hepatopathies of patients and an increased cancer rate in operating room personnel working with halothane and metofane.
Besides the safety of the gas and the ease of administration without the necessity of endotracheal intubation, the birds recover extremely fast with little or no wing flapping. The patients will often stand within seconds of cessation of the gas flow.
Other Anesthetics
Other anesthetic regimens can be used, of course,. but do not have the safety and other advantages of isoflurane. Metofane induction by cone, followed by intubation and the use of halothane by an open breathing system, is one regimen. Others prefer metofane induction and metofane maintenance in a closed system. Gaseous anesthetics are usually chosen because of rapid recovery time and relative safety and control.
Injectable anesthetics are used for certain procedures but are not as easy to control as the gases. Respiratory and cardiac depression may be complication factors. The authors prefer intravenous Rompun-Ketamine (equal volumes of 100 mg/cc Ketarnine and 20 mg/cc Xylazine) if an injectable must be used.
In gases other than isoflurane and with the use of injectables, wing flapping on recovery is prevented by wrapping the patient in a large towel. By the time the bird can work itself out of the towel, it usually can perch and not injure itself.
Gaseous anesthetics are preferable for birds. It is extremely reassuring to have a patient "walk off the table;' rather than remain comatose for a prolonged period of time following injectable anesthetics.
Pre-operative Evaluation
The clinical pathology laboratory plays in important role in the preoperative evaluation of the avian patient. The problem of subclinical illness in caged birds and their ability to mask symptoms makes diagnosis of illness difficult.
In an elective surgery, every attempt is made to correct any abnormalities before proceeding. In a non-elective surgical procedure, the abnormalities are treated as part of the post-operative care. In a non-elective surgical procedure, the clinician is advised to be especially wary if an SGOT (SAST) rise has occurred. While not liver specific, an SGOT (SAST) rise often indicates liver disease which may portend potential bleeding problems. An injection of vitamin K1 (1-2 mg/kg) prior to surgery may help minimize potential bleeding.
Antibiotics, Steroids and Fluids
Prior to an elective surgery, the authors prefer to initiate antibiotic therapy. Injectable penicillin derivatives such as Piperacillin (Pipracil®- Leder le) and Carbenicillin (Geopen®- Roche) used in combination with the newer arninoglycosides such as Tobramycin (Nebcin®- Eli Lilly) or Amikacin (Amikin®-Bristol) are preferred.
If a particularly risky surgery is to be attempted, especially in small bird patients, we prefer to give a shock dose of Dexamethasone (I mg/lb I.M.) prior to surgery. In our experience, this seems to enhance success. We have most frequently used this technique when removing abdominal masses from budgerigars or attempting risky procedures such as egg yolk peritonitis cleanup or ectopic egg removal in small birds.
Fluid therapy is seldom necessary unless blood loss is severe. Intravenous fluids may be given to the anesthetized bird through the ulnar veins, using 25 or 26 gauge needles or butterfly catheters (Angiocath®- Deseret), We usually use Lactated Ringers solution or a mixture of 50:50 5% Dextrose and Lactated Ringers at a volume of .Oycc/gm/body weight. Some of the fluids can be given I.V. and the rest subcutaneously (axillary and inguinal areas). Fluids are given by rapid bolus administration.
Warmth is critical to recovery in the avian surgical patient. Judicious use of heated cages, heating pads and incubators is important.