title: Evaluation of medetomidine-ketamine anesthesia with atipamezole reversal in American alligators (Alligator mississippiensis).
abstract: Sixteen captive and wild-caught American alligators (Alligator mississippiensis), seven juveniles (< or = 1 m total length [TL]; 6.75 +/- 1.02 kg), and nine adults (> or = 2 m TL; 36.65 +/- 38.85 kg), were successfully anesthetized multiple times (n = 33) with an intramuscular (i.m.) medetomidine-ketamine (MK) combination administered in either the triceps or masseter muscle. The juvenile animals required significantly larger doses of medetomidine (x = 220.1 +/- 76.9 microg/kg i.m.) and atipamezole (x = 1,188.5 -/+ 328.1 microg/kg i.m.) compared with the adults (medetomidine, x = 131.1 +/- 19.5 microg/kg i.m.; atipamezole, x = 694.0 +/- 101.0 microg/kg i.m.). Juvenile alligators also required higher (statistically insignificant) doses of ketamine (x = 10.0 +/- 4.9 mg/kg i.m.) compared with the adult animals (x = 7.5 +/- 4.2 mg/kg i.m.). The differences in anesthesia induction times (juveniles, x = 19.6 +/- 8.5 min; adults, x = 26.6 +/- 17.4 min) and recovery times (juveniles, x = 35.4 +/- 22.1 min; adults, x = 37.9 +/- 20.2 min) were also not statistically significant. Anesthesia depth was judged by the loss of the righting, biting, corneal and blink, and front or rear toe-pinch withdrawal reflexes. Recovery in the animals was measured by the return of reflexes, open-mouthed hissing, and attempts to high-walk to the opposite end of the pen. Baseline heart rates (HRs) were significantly higher in the juvenile animals (x = 37 +/- 4 beats/min) compared with the adults (x = 24 +/- 5 bpm). However, RRs (juveniles, x = 8 +/- 2 breaths/min; adults, x = 8 +/- 2 breaths/min) and body temperatures (juveniles, x = 24.1 +/- 1.1 degrees C; adults, x = 25.2 +/- 1.2 degrees C) did not differ between the age groups. In both groups, significant HR decreases were recorded within 30-60 min after MK administration. Cardiac arrhythmias (second degree atrio-ventricular block and premature ventricular contractions) were seen in two animals but were not considered life-threatening. Total anesthesia times ranged from 61-250 min after i.m. injection. Although dosages were significantly different between the age groups, MK and atipamezole provided safe, effective, completely reversible anesthesia in alligators. Drug-dosage differences appear to be related to metabolic differences between the two size-classes, requiring more research into metabolic scaling as a method of calculating anesthetic dosages.
authors.affiliation: Department of Pathobiology, College of Veterinary Medicine, University of Florida, Gainesville 32611-0880, USA.
authors.forename: Terrell G
authors.initials: TG
authors.lastname: Heaton-Jones
authors.forename: Jeff C H
authors.initials: JC
authors.lastname: Ko
authors.forename: D L
authors.initials: DL
authors.lastname: Heaton-Jones
mesh_terms: D000316:Adrenergic alpha-Agonists; D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000489:Alligators and Crocodiles / Q000502:physiology*; D018712:Analgesics, Non-Narcotic / Q000037:antagonists & inhibitors; D000758:Anesthesia / Q000592:standards / Q000662:veterinary*; D000762:Anesthesia Recovery Period; D019162:Anesthetics, Combined / Q000037:antagonists & inhibitors; D000778:Anesthetics, Dissociative / Q000037:antagonists & inhibitors; D000818:Animals; D004562:Electrocardiography / Q000662:veterinary; D006339:Heart Rate / Q000187:drug effects; D007093:Imidazoles / Q000494:pharmacology; D007649:Ketamine / Q000037:antagonists & inhibitors; D020926:Medetomidine / Q000037:antagonists & inhibitors; D012018:Reflex / Q000187:drug effects; D012119:Respiration / Q000187:drug effects; D012149:Restraint, Physical / Q000662:veterinary
chemical_list: D000316:Adrenergic alpha-Agonists; D000317:Adrenergic alpha-Antagonists; D018712:Analgesics, Non-Narcotic; D019162:Anesthetics, Combined; D000778:Anesthetics, Dissociative; D007093:Imidazoles; C050701:atipamezole; D007649:Ketamine; D020926:Medetomidine