Injectable Anesthesia and Analgesia of Birds by J. Paul ... - Ufersa

More documents

Recommendations

Info

excitement [33], although darting procedures, regardless of the anesthetic, can create a period of excitement. Medetomidine as a sole anesthetic agent is ineffective in the ostrich [35]. When medetomidine was combined with ketamine and followed by intravenous propofol, it was an effective combination for chemical immobilization of captive ostriches, although positive pressure ventilation was recommended [22]. Apnea is a common occurrence during ostrich anesthesia, regardless of the induction agents selected. Ventilatory support is highly recommended for this group of birds. Analgesia Opioids - The early literature regarding the use of opioids in birds is confusing and contradictory. For example, one study used two different strains of chickens to evaluate the analgesic effect of equal doses of morphine. Based on their response to a noxious thermal stimulus, one strain had a hyperalgesic response while another strain had an analgesic response [36]. With many such conflicting results in the literature, it was assumed that opioids were not effective analgesics for birds. More recently, the physiological effects of opioids on birds have been documented using isoflurane-sparing techniques [37-39]. In these studies, unpremedicated birds are anesthetized with isoflurane. The minimal anesthetic concentration (MAC) is determined in each bird, after which each bird is injected with an analgesic and MAC is again determined. A significant reduction of MAC indicates that the drug being tested has analgesic properties. Using this technique, the analgesic effects of butorphanol were evaluated in cockatoos, African grey parrots, and Amazon parrots. Butorphanol at 1 mg/kg was found to be analgesic in African gray parrots and cockatoos, but not Amazon parrots [38,39]. Following injection of butorphanol, heart rate, tidal volume, and inspiratory and expiratory times were all significantly decreased [38,39]. A similar study compared mu and kappa opioids in chickens and both drugs had isoflurane-sparing effects [37]. Recent studies evaluated the effects of butorphanol and buprenorphine in conscious parrots [40,41]. In African grey parrots, butorphanol (1 - 2 mg/kg, IM) had an analgesic effect while large doses of buprenorphine had no significant analgesic effect [41]. In Hispanolian parrots, higher doses of butorphanol (3 mg/kg) were needed to produce a similar analgesic effect (J. Paul-Murphy, personal observation). Species variability in response to opioids does occur and caution is advised when extrapolating butorphanol doses from one avian species to another. Fentanyl (0.02 mg/kg, IM), a synthetic mu agonist, was tested in a similar fashion in cockatoos, and was found to have little analgesic effect; a higher dose (0.2 mg/kg, SQ) was analgesic (S. Hoppes, unpublished data). This may be due to fentanyl binding both mu and kappa receptors when given at high doses. An excitement phase was noted in several of the birds shortly after fentanyl was injected (S. Hoppes, unpublished data). The duration of effect of all of these opioids has only been evaluated empirically and their duration of effect may be as short as 2 - 4 hours. Pharmacodynamic studies have demonstrated that pigeons have more kappa opioid receptors than mu opioid receptors [42]. This one piece of information in pigeons is used to explain why birds do not respond as do mammals to mu agonists like morphine, buprenorphine and fentanyl, and why kappa opioids, such as butorphanol, may be more efficacious analgesic in birds. Butorphanol is currently recommended for opioid analgesia in birds, and it can be given as a pre-operative and postoperative analgesic. When butorphanol is used as an induction agent and pre-operative analgesic the concentration of isoflurane needed for anesthesia will be reduced. Non-steroidal anti-inflammatory drugs There are several categories of nonsteroidal anti-inflammatory drugs (NSAIDS), but few have been investigated in birds and even fewer have been evaluated for clinical application [26,43]. Much of the information about doses and effects for birds has been gained through practical application. Studies using chickens have provided pharmacokinetic information on oral dosing of a few NSAIDS and short half-life and low bioavailability were common findings, but pharmacokinetic studies are a poor predictor of analgesic efficacy [44-46]. In mammalian species, NSAIDS are synergistic with other classes of analgesic agents and may be most effective for perioperative analgesia when used in combination with opioids [47]. In birds, as in other species, pre-emptive use of NSAIDS may decrease tissue sensitization caused by surgical trauma and may reduce the period of post-operative opioid therapy. The most commonly used NSAIDS in avian medicine today are carprofen and ketoprofen. The proprionic acid class of NSAIDS are analgesic, anti-inflammatory and antipyretic in mammals and are expected to have similar effects in birds. Chickens given a 1 mg/kg subcutaneous dose of carprofen had peak plasma levels 1 - 2 hours after injection and pain thresholds were raised for at least 90 min [48]. When carprofen-treated feed was offered to chickens, lame chickens selected more drugged feed than sound birds and the amount of carprofen consumed increased with the severity of lameness [49]. Low plasma concentrations of carprofen (0.28 µg/ml) provided some analgesia for birds, but to reach plasma levels of 8.3 µg/ml, similar to therapeutic plasma levels in mammals, an equivalent of 40 mg/kg body weight per bird was needed in the feed [48]. A documented side effect of NSAIDS in mammals is gastrointestinal ulceration and bleeding due to inhibition of prostaglandin synthesis. A similar toxic effect in birds was reported when high dosages of flunixin meglumide (10 mg/kg)
caused regurgitation and tenesmus in budgerigars [43]. The most serious complication of flunixin meglumide in birds is renal ischemia. Bobwhite quail experimentally given daily intramuscular injections of flunixin meglumide for 7 days had histological evidence of renal damage in all birds, even at doses as low as 0.1 mg/kg. Severity of the lesions was directly correlated to the dose of flunixin meglumide with acute necrotizing glomerulitis, tophi in the renal tubules and visceral gout occurring at 32 mg/kg [50]. Renal ischemia and necrosis has been documented in Siberian cranes treated with flunixin meglumide (5 mg/kg) for muscle and skeletal trauma [51]. The use of flunixin meglumide currently is contraindicated in cranes and used with great caution with other avian species. Piroxicam is used in mammals to treat chronic inflammatory conditions such as arthritis. It as been used to treat chronic degenerative joint disease in cranes and other species of birds and appears to provide mild to moderate improvement and willingness to bear weight on affected limbs over extended treatment periods. Drug Dosage (Dose), Route Species / Remarks Reference Atipamezole 182 - 281 mg/kg (250 mg dose), IV Mallard ducks: to reverse medetomidine; rapidly regained consciousness, struggled & flapped wings; tachycardia and tachypnea observed. Machin [21] 0.2 mg/kg, IV; and 0.2 mg/kg, SC Ostriches: to reverse medetomidine; half of the total 0.4 mg/kg dose was given IV, the other half SC; recovery was smooth and ranged from ~14 - 28 min Langan [22] 3.75 - 10 mg/kg Pigeons (Columbia livia) and Amazon Parrots (Amazona spp.): Used to reverse medetomidine; the dose given was 2.5 or 5 times the medetomidine dose administered. No differences were seen between the higher and lower doses. Recovery was smooth and rapid; standing times were all within 4 min Sandmeier [18] 0.25 - 1.0 mg/kg Various avian species: Recommends a dose 5 times that of medetomidine to reverse its effects. Jalanka [52] 0.5 - 2.5 mg/kg Various avian species: Recommends a dose 5 times that of medetomidine to reverse its effects. Berthier [53] Atipamezole (A) / Diprenorphine (D) Atipamezole (A) Flumazenil (F) (A) 40 - 161 mg/kg (5 - 20 mg dose) (D) 12 - 20 mg/kg (15 - 25 mg dose), IV (A) 182 - 281 mg/kg (250 mg dose) (F) 18 - 28 mg/kg (25 mg dose), IV Red-necked ostriches (Struthio camelus): to reverse meditomidine/etorphine combination; lead to a fast but violent recovery. Mallard ducks: to reverse medetomidine/midazolam, respectively; rapidly regained consciousness, struggled & flapped wings; tachycardia and tachypnea observed. Ostrowski [33] Machin [21] Atropine 0.006 mg/kg, IV Ratite; used to treat bradycardia. Lin [30] Butorphanol (B) 1 - 2 mg/kg, IM African grey parrots (Psittacus erithacus): 6/11 birds had an increased pain threshold to a noxious electrical stimulus after administration of 1 mg/kg B (this may represent the ED 50 for the drug); higher dosages such as 2 - 3 mg/kg have been used to treat pain in subsequent studies without adverse side effects (unpublished findings). Cockatoos (Cacatua spp.): reduced isoflurane requirement in cockatoos; heart rate was reduced by 12%; apnea was not observed; respiratory rate increased by 77%, while tidal volume decreased by 25%, thus having no significant net effect on minute ventilation. Paul- Murphy [41] 1 mg/kg, IM Curro [38] 1 mg/kg, IM Psittacines: significantly reduced isoflurane ED 50 in cockatoos (Cacatua spp.) and African grey parrots (Psittacus erithacus), but had no affect on the isoflurane ED 50 in blue-fronted Amazons(Amazona aestiva aestiva). Curro [39]
Page 1 and 2: In: Recent Advances in Veterinary A
Page 3: as to avoid the bird recovering und
Page 7 and 8: Drug Dosage (Dose), Route Species /
Page 13 and 14: 5. Clubb SL. Round table discussion

Injectable Anesthesia and Analgesia of Birds by J. Paul ... - Ufersa

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?