Nitrous Oxide – Nitrous Oxide is rarely used, and can not be used on its own. Halothane or Isoflurane MUST be used in combination with Nitrous Oxide.
Halothane – Halothane can be used safely in avian patients though it is not our first choice of inhalants. There are several disadvantages:
- Halothane is metabolized by the liver. As many avian patients have some degree of liver disease, this inhalant can put the patient in some risk and recovery is often extended.
- Cardiac arrest often occurs at the same time as respiratory arrest giving little response time in an emergency.
- Halothane is also more likely to induce cardiac arrhythmia than many injectable anesthetics or isoflurane.
- Halothane depresses the responsiveness of the bird’s intrapulmonary chemoreceptors (IPC) to carbon dioxide. When the IPC is depressed the patient’s ability to adjust ventilation in response to changes in carbon dioxide levels will be compromised.
Isoflurane – Isoflurane has been the anesthetic of choice for avian patients for some time.
The advantages include the following, taken from Veterinary Nursing of Exotic Pets:
- “Low blood solubility and minimal metabolism of the drug by the bird (<1.02%). This means that the drug does not accumulate in the bloodstream, and is rapidly excreted by the patient, allowing rapid changes in anesthetic depth.”
- “Minimal cardiopulmonary effects at sedative or light anesthesia levels”.
- “Little or no tendency to cause cardiac arrhythmias”.
- “Unlike halothane, isoflurane does not require metabolism in the liver, making it suitable for sick avian cases”.
- “Cardiovascular arrest does not occur at the same time as respiratory arrest, allowing time for resuscitation”.
Sevoflurane – Sevoflurane requires little or no organ metabolism and is very safe. Slightly higher percentages are required to induce and maintain the patient, but low blood solubility does allow rapid changes in anesthetic levels. Sevoflurane has faster induction and recovery time due to decreased blood and tissue solubility and smoother recoveries with less ataxia than Isoflurane. At times you may not always see a faster or smoother recovery and this can be due to hypotension, acid-base imbalance, and hypoxemia.
Recovery - Avian patients should recover quickly from inhalant anesthesia. Once the anesthetic is turned off the patient should be left on oxygen until fully awake. The best way of doing this is to use an avian oxygen cage or incubator, both of which will also be help to maintain temperature.
References:
Veterinary Nursing of exotic Pets – Girling
Exotic Animal Care – Tully and Mitchell
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