Avian Restraint & Anesthesia (JTA 4)

Question 1

How does the minimum alveolar concentration of isoflurane in white eyed parakeets differ from other birds?

How is that affected by tramadol?

What is the mechanism of action of tramadol?

Answer 1

Higher (2.5%) than other birds (1-1.5%).

Tramadol did not affect MAC. It also did not affect time to extubation.

Tramadol is a synthetic opioid that enhances release of serotonin & NE and inhibits their reuptake.

Source: JZWM 48(2): 380–387, 2017. EFFECTS OF TRAMADOL ON THE MINIMUM ANESTHETIC CONCENTRATION OF ISOFLURANE IN WHITE-EYED PARAKEETS (PSITTACARA LEUCOPHTHALMUS)

Question 2

How do avian anesthetic mortality rates compare to other companion animals?

What proposed explanations exist for this discrepancy?

Answer 2

• Mortality rates within 48 hours after anesthesia reportedly higher in parrots (3.95%) and other birds (1.76%) than cats (0.24%), dogs (0.17%), and people (0.02-0.005%)
• Possible reasons – limited functional residual lung volume (apnea more dangerous), excitement increases NE & Epi sensitizing the myocardium to arrhythmias
• Birds do have higher risk

JAVMA 2017 - Outcome following inhalation anesthesia in birds at a veterinary referral hospital: 352 cases (2004–2014)

Question 3

Describe the differences between alfaxalone only, alfaxalone + midazolam, and alfaxalone + butorphanol anesthesia in the Bengalese finch.

Answer 3

• Significant dose-dependent increases in the duration of anesthesia for dose response trial
• Alfax midaz resulted in significantly faster induction compared with both alfaxalone and Alfax torb
• Righting times statistically longer and slower recovery for AM and AB groups than for A alone
• Only AM had statistically significantly lower pulse rates compared with A alone
• Apnea was not observed in any animal
• Minimal dose-dependent reductions in response to noxious stimulation of the phalanx
• Addition of midazolam but not butorphanol reduced responses to noxious stimuli
• AM reached maximal muscle relaxation quicker (leg- 10 min; wing- 15–20 min) than AB (leg and wing - 25 min) and was slightly more effective in reducing muscle tone
• Duration was similar for both AB and AM, with effects wearing off 40 min and lasting on average 85–90 min

Perrin, K. L., Nielsen, J. B., Thomsen, A. F., & Bertelsen, M. F. (2017). Alfaxalone anesthesia in the Bengalese finch (Lonchura domestica). Journal of Zoo and Wildlife Medicine, 48(4), 1146-1153.