Surgical preparation, post-operative care important considerations for avian patients

Most successful surgical procedures in avian patients, as with other species, require that the veterinarian and his or her staff give special attention to the details of perioperative management. In some instances, special techniques may be required to perform and successfully complete appropriate procedures; however, in many instances the same techniques used in companion species (dogs/cats) may be adapted or adjusted for use in exotic species.

Veterinarians should familiarize themselves with appropriate anatomy, physiology/pathophysiology as well as available protocols for preparation, instrumentation and perioperative management.

Preoperative preparation

Without a doubt, two of the most critical aspects of perioperative management of the surgical patient are the history and physical examination. The history obtained from the owner should evaluate all aspects of husbandry including source of pet(s), length of ownership, diet, environment and current or previous illness(es).

The physical examination will help evaluate cardiopulmonary status, overall physical condition, severity of illness(es) if present and any conditions unknown to the owner. The veterinarian and staff can then assess presurgical condition and classify the necessity of anesthesia and surgery. Health problems identified during the physical examination such as anemia, dehydration and hypoglycemia should be addressed and corrected prior to placing the pet under anesthesia unless absolutely necessary.

Preoperative diagnostics

The minimum database for any procedure that requires anesthesia should include a packed cell volume (PCV), total protein or solids (TP) and blood glucose. For more extensive procedures a complete blood count (CBC), biochemical profile, electrolytes, urinalysis and radiographs may be required. All patients should be as physiologically stable as possible prior to anesthesia and surgery.

Fasting

The purpose of fasting is to allow the upper gastrointestinal system, especially the crop, to empty thereby reducing the likelihood that the patient will regurgitate/vomit or reflux and aspirate the ingesta. Because of the small size of most avian patients a prolonged fasting period is not recommended. It is important to remember that birds, especially neonatal birds, are unable to handle prolonged fasting presumably due to the limited hepatic glycogen stores. A three-hour fast is usually sufficient for most companion avian species. Small species such as budgerigars, canaries, finches may require an even shorter fasting period. Raptors and especially waterfowl may require a fast of 12 hours or more.

Anesthetic protocol

There are numerous sources of information concerning anesthetic protocols for avian species. To become familiar with these protocols, I would recommend purchasing an appropriate source for this information. Sources include:

• Veterinary Clinics of North American Exotic Animal Practice
• Seminars in Avian and Exotic Pet Medicine
• Avian Medicine: Principles and Applications
• Avian Medicine and Surgery
• Manual of Avian Medicine
• Laboratory Medicine: Avian and Exotic Pets
• Exotic Animal Formulary*
• Manual of Avian Practice
• Seminars if Avian and Exotic Pet Medicine.

When choosing an anesthetic protocol, select one that will allow you to complete the desired procedure with minimal to no physiologic changes to the patient. Appropriate emergency drugs should be readily available or prepared in syringes prior to initiating the anesthetic protocol. This is a time-saving move that allows the veterinarian or attending staff to address anesthetic emergencies (cardiopulmonary arrest) as soon as they occur. I would suggest intubating any patient that will be under anesthesia for longer than 10-15 minutes.

Patient preparation

Patient preparation is another critical aspect of perioperative management of avian species. Most avian patients have extremely high metabolic rates in addition to their small size that can make hypothermia a real and constant problem. To minimize heat loss during procedures use heating pads (circulating water), Bair Hugger Total Temperature Control Systems™ (Augustine Medical, Inc., 10393 West 70th Street, Elden Prairie, MN 55344) and warm fluids. Another option is to warm the surgical suite. When using heating blankets/pads or bottles be sure to separate the patient from the heat source by a towel to avoid burning the patient during and after the procedure.

To prepare the area for surgery pluck feathers to a minimum distance of 2-3 cm around the surgical site. Additionally, care must be taken to not damage feather follicles when preparing birds for surgery; feathers should be pulled in the direction they normally grow. Filoplumes may be clipped with a small clipper or scissors.

Following removal of feathers standard aseptic technique should be used to prepare the skin for surgery. The goal of surgical preparation of the skin is to reduce the numbers of bacteria without damaging the skin, thereby reducing postoperative infections.

Surgical prep solutions should contain chlorhexidine diacetate (0.5%) (Nolvasan Solution, Fort Dodge Laboratories, Fort Dodge, IA) or Chlorhexidine gluconate (4.0%) (Hibiclens, Stuart Pharmaceuticals Division, ICI America, Wilmongton, DE). In most instances, veterinarians use alcohol as a surgical rinse. The use of saline is preferable because it doesn't contribute to as much heat loss as alcohol.

Instrumentation

Most techniques and instruments used in companion species (dogs and cats) can be used in exotic species. In many instances, a surgical pack with ophthalmic instruments can be used, but for delicate surgical procedures, microsurgical instruments are required. Microsurgical instruments are available from a variety of sources (ASSI, Accurate Surgical & Scientific Instruments Corporation, Westbury, NY; Sontec Instruments, Inc., Englewood, CO; Pilling Co., Ft. Washington, PA) and are preferred for several reasons; their length allows the surgeon's wrists to rest comfortably on the table while the tips are within the body cavity, the handles are rounded so that they can be rolled between the thumb and first finger which reduces tremors, and they are counter balanced which reduces fatigue.

Tissue retractors

Tissue retractors are of great benefit during surgical procedures as the small patient size may limit the number of surgeons that can actively participate in the procedure. The Lone Star Veterinary Retractor System (Jorgensen Laboratories, Inc., Loveland, CO) consists of a notched, autoclavable frame and a set of tissue hooks on elastic bands. However, the stays are not autoclavable. The hooks are placed in the tissue and the appropriate amount of tension is placed on the band to allow visualization of the surgical field. The band is then inserted into one of the notches. The first two hooks must be placed on opposite sides of the surgical site to allow stabilization of the frame.

Radiosurgical units

I consider radiosurgical units an absolute necessity for all procedures. Electrosurgical units employ a high-frequency alternating current to generate energy that creates molecular heat within each cell causing water to vaporize and the cell to rupture while the electrode remains cool. Coagulation of tissues occurs when the current density is sufficient to dehydrate the cell(s) and their contents. Electrosurgical units use two electrodes, an active electrode and an indifferent electrode (ground plate). This results in concentration of the current at the tip of the active electrode. For most electrosurgery units, the ground plate is placed as close to the surgical area as possible, with contact improved by the use of a gel or paste. In contrast, the Surgitron (Ellman International, Inc., Helwett, N.Y.) produces radiofrequency wavelength energy that allows the ground plate to act as an antenna rather than as a ground plate. Thus, the ground plate does not need to be in contact with the patient. This is important when considering the small patient size of many exotic patients. Burns can occur when the ground plate contacts only a small area because the current exiting the patient is concentrated at this location. The radiosurgical units also have a bipolar forceps which eliminate the need for the groundplate altogether.

Laser surgical units

Lasers (light amplification by stimulated emission of radiation) are also viable options for surgical procedures in exotic patients. Since the operator can control the laser's output and focus the beam there is less collateral heat damage to surrounding tissues that leads to better healing.

The most commonly used lasers in the veterinary medical field are the carbon dioxide laser and the diode laser. CO2 lasers (Accuvet CO2, ESC/Sharplan) produce a beam of light energy at a wavelength of 10,600 nm. This wavelength is highly absorbed by water making it ideal for cutting (with a focused beam) and vaporizing (with a defocused beam). Incisions with the CO2 laser are essentially bloodless as it seals vessels with a diameter of 0.6 mm or less. CO2 lasers also seal lymphatic vessels that may reduce postoperative edema. Smaller nerves are also sealed which may reduce postoperative pain. It is thought that the thermal insult resulting from the use of the CO2 laser is superficial (approximately 50-100µm deep); however, when used incorrectly, lasers can cause significant thermal injury.

Diode lasers (Sharplan 810 and 980, ESC/Sharplan) produces a beam of light energy in the 635nm to 980nm wavelength range. The main advantage of using Diode lasers over CO2 lasers is that they can be used through an endoscope. Additional uses of diode lasers include chromophore enhanced tissue ablation or coagulation, laser welding (tissue fusion) and photodynamic therapy. The diode laser has deeper penetration than the CO2 laser and is less precise for delicate procedures such as debriding a cornea and ablating an adrenal gland.

Lasers are to be used only after operators have received proper training to avoid injury.

Magnification

Magnification, although not absolutely necessary in all procedures, is highly recommended due to the small size of most exotic patients. Magnification may be provided by surgical scopes or loupes/telescopes such as those produced by Surgitel (General Scientific Corp., Ann Arbor, MI,

www.surgitel.com

). Binocular magnification loupes or telescopes of 1.5X to 3.5X provide excellent magnification for most procedures. Surgical scopes should have a lens objective of approximately 150mm with a 12.5mm ocular lens.

One of the least expensive options for surgical magnification are hobby loupes that can be obtained from hobby stores or other specialty shops. No matter what type of magnification system is used the surgeon should strongly consider the ergonomics of the chosen system. The ergonomically correct system will allow the surgeon to perform the procedure with the head in an erect position. It is also recommended that the magnification system have a focal range rather than a set focal distance. This will allow the surgeon a large depth of field as well as a large view of the patient.

Patient monitoring

There are numerous methods of monitoring the patient in addition to the use of a stethoscope while it is under anesthesia and undergoing a surgical procedure.

Electrocardiography (ECG) is commonly used for most procedures and affords the anesthetist a reliable indication of the patient's pulse rate as well as clues toward impending changes in the patient's cardiovascular system. The ECG should be capable of recording speeds of 100 mm/s and amplify the signal to at least 1mV equal to 1 cm. Standard lead positions described for dogs and cat are used for birds; however, many small avian patients are difficult to monitor with an ECG due to their rapid heart rates or the small electrical potential produced.

Ultrasonic Doppler detects pulsatile blood flow and are based on the principle that the frequency of transmitted sound waves are altered when reflected off moving red blood cells. Dopplers are considered to be very accurate as long as they are placed in close proximity to an artery or the heart. Unfortunately, they do not give information regarding changes in the patient's physiological status. I personally use Doppler flow detection for all avian patients. One of the best sites to use for placement of the Doppler probe is over the superficial ulnar artery or the deep radial artery just inside the elbow.

Pulse oximetry involves the use of a noninvasive technique to measure pulse and oxygenation during anesthesia and surgery. Pulse oximeters estimate arterial hemoglobin O2 saturation (SaO2 or SpO2) by measuring pulsatile signals across (transmission) or by reflectance (reflection) from perfused tissue at two discrete wavelengths (660 nm, red; 940nm infrared) using the constant component of absorption at each wavelength to normalize the signals. Pulse oximetry should be used to evaluate trends in oxygenation as values may be unsatisfactory for routine use in some exotic patients; in particular avian species.

Post-operative considerations

The immediate postoperative period is another critical time to pay special attention to avian patients recovering from anesthesia and surgery. Patients should be placed in a quiet (away from dogs, cats, high traffic), visually secure, warm recovery cage or incubator as they awaken from anesthesia. During this period, fluid balance should be addressed as well as postoperative pain. Signs of pain may include abnormal body positions, tucked abdomen/coelomic cavity, aggression (biting, attacking), vocalization, reluctance to move or stand, pronounced fear, self mutilation and inability to perform "normal" everyday activities. Unfortunately, few studies have been performed in exotic species; however, many of the same analgesics used in dogs and cats can all be used in exotic species.

Dr. Jones is associate professor of avian and zoological medicine at the University of Tennessee’s College of Veterinary Medicine. He is a diplomate of the American Board of Veterinary Practitioners-Avian Specialty. Dr. Jones’ clinical interests include raptor medicine, orthopedic and soft tissue surgery, avian nutrition and avian infectious diseases. He is also a master falconer with 15 years experience.