Veterinary Clinical Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA, USA
Pain management of animal species that veterinarians treat has become an integral component of patient medical management. This is especially true for avian species. Twenty years ago little or no thought was afforded those animals in which pain may have been part of the treatment plan or disease process. It was not unusual to have a bird that had survived a major surgical procedure die during recovery from anesthesia. Of course other factors may have been contributing to these post-surgical deaths (e.g., hypovolemia, hypothermia), but pain most certainly was involved as a post-surgical negative stimulus to the patient. This should be considered if one believes that birds feel pain and at what quality and intensity this noxious stimulus is experienced. A proposed working definition of pain by the International Society for the Study of Pain is an “unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage.”1,2 Most veterinarians today believe that their avian patients experience pain. Depending on the severity of the injury, treatment, or surgical procedure there is also an understanding of pain gradients.
With the long overdue attention on pain management in veterinary medicine and specifically as it relates to birds there is a paucity of information on pain recognition in the patient, appropriate drug selection, and treatment protocol. A list of universal questions has been proposed as a way to determine if an animal is feeling pain:2 1. Would the lesion or procedure be painful to any species? 2. Is the lesion or procedure damaging to tissues in any species? 3. Does the patient display any abnormal behavioral responses? 4. My addition: If the patient were you - do you believe you would feel pain? The end result of these questions depends on the answer to each. If the answer to any of the above questions is yes, then pain management therapy should be initiated for that patient. For the question, “Does the patient display any abnormal behavioral responses?” The veterinarian must know what to look for when examining the avian patient. Clinical signs I associate with pain in an avian patient include, limping, wing drop, squinting of the eye(s), depress ion, increased blood pressure, retraction of a limb or wing when an apparent injured area is palpated, anorexia, and vocalization when the said area is palpated. Determining if an avian patient requires pain management is just the first step on the difficult journey of establishing a treatment regimen.
With close to 9,000 different avian species one must not assume that the analgesic doses determined for other animal groups can be extrapolated to birds. Even more disconcerting is the scientific evidence that shows dose differences between avian species. There have been very few published pharmacokinetic studies involving avian species as it relates to analgesic compounds. Veterinarians must also understand that the results of those studies only pertain to the species involved in those studies. Any published analgesic dose should be carefully assessed prior to administration on an avian species for which a scientifically established dose has not been determined.
Preemptive analgesia is the administration of an analgesic agent prior to a surgical procedure. The basis of preemptive analgesia is to reduce or prevent prolonged central nervous system changes resulting from pain induced by the surgical procedure that may contribute to postoperative pain. Preemptive analgesia may be used for skin incisions, internal and orthopedic surgical procures through nerve blocks. A long-acting local anesthetic agent is bupivacaine, which may provide the best clinically effective analgesic properties for this group of drugs.2 Eutectic mixture of local anesthetic (EMLA), is a topical cream mixture of 2.5% lidocaine and 2.5% prilocaine. Although no studies have been performed to scientifically measure EMLA cream’s effectiveness in avian species, its use prior to venipuncture and biopsy collection has been anecdotally reported.2
Opioid analgesic agents are used commonly in veterinary practices for pain management. Unfortunately, there is a lack of information on the effectiveness of these drugs in most avian species. There is also a lack of scientifically derived data on the concentration and distribution of the µ-, κ- , and δ-opioid receptors in different avian species’ central nervous system. Information regarding the concentration and distribution of the opioid receptors in individual avian species is important because it is the drug’s binding to these receptors from which analgesia is obtained. Each drug in this class has an affinity to specific receptors, therefore if an avian species has more or a greater concentration of the opioid receptor of choice the drug should be more effective. Morphine is a µ receptor agonist while butorphanol is a strong K receptor agonist. In most avian species butorphanol has been apparently the most consistent with supplying analgesic benefits to the patient. Buprenorphine, a slow-onset, long acting opiate is a partial µ agonist with mixed results in affecting analgesia in avian studies. Buprenorphine may be effective with many avian species but it apparently has little effect in African grey parrots, even when administered relatively large doses.2
Nonsteroidal anti-inflammatory drugs (NSAID) are arguably the most used analgesic agents in avian medicine. The newer generation of NSAIDs target the inhibition of the cyclooxygenase (COX) enzyme in the arachidonic acid pathway. The COX-2 class of drugs has been promoted over the COX-1 class because of less physical side effects, especially affecting the gastrointestinal and renal systems. Meloxicam and celecoxib are effective COX-2 inhibitors used often in avian medicine.
Once an analgesic agent has been selected the duration of treatment should be established. Of course depending on the speed of recovery the treatment period can be reduced or extended, but never without careful consideration. Any analgesic agent, has potential side effects, therefore judicious use is recommended. When the patient does not show any overt clinical signs associated with pain and when you feel recovery can progress without pain medication then analgesic administration should be discontinued.
- Butorphanol 0.5–4.0 mg/kg IM q1–4h
- Buprenorphine HCL 0.25–0.5 mg/kg IM q6h
- Gabapentin 10 mg/kg PO q12h
- Hydromorphone HCL 0.6 mg/kg IM q6h
- Meloxicam 0.1–0.2 mg/kg PO IM q24h
- Tramadol HCL raptors: 5–11 mg/kg PO q12h; psittacines: 15–30 mg/kg q6h
1. Definition of Pain: International Association for the Study of Pain website. Available from: www.iasp-pain.org/terms-p.html#Pain. (VIN editor: Link not accessible as of 5-20-2018).
2. Hawkins MG. The use of analgesics in birds, reptiles, and small exotic mammals. J Exotic Pet Med. 2006;15(3):177-192.
3. Carpenter JW ed. Exotic Animal Formulary. 4th ed. St. Louis, MO: Elsevier-Saunders; 2013.
4. Sanchez-Migallon Guzman D, Kukanich B, Drazenovich TL, Olsen GH, PaulMurphy JR. Pharmacokinetics of hydromorphone hydrochloride after intravenous administration of a single dose to American kestrels (Falco sparverius). Am J Vet Res. 2014;75(6):527–531.