Immobilization of Polar and Brown Bears Using Etorphine and Xylazine
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J. Zoo An. Med. 13: 11·18, 1982 down" agent for capturing bears, but it has no narcotic nor analgesie properties. It has IMMOBILIZATION OF POLAR been shown that phencyclldine and (Thalaretos marItIm.,.) AND BROWN etorphine are safer to use in the bear. 8,14 As (Ursus aretos) BEARS USING phencyclidine has been taken off the market ETORPHINE AND XYLAZINE as a result of its abuse by drug addicts ("angel dust"), etorphine is now the primary T. Gatesman " drug that can be administered by a single H. Wiesner" dart to effect immobilization. Other drugs, such as xylazine (8-10 mg/kg), 3,15,17,19 ketamine (10-12 mg/kg),9,13 and droperldol Introduetlon plus fentanyl (as Innovar-Vet® + 1 ml/18 The polar bear and the brown bear are kg)9 are also effective in bears. However, exceedingly strong and ferocious animals so that capture and handling of them is ' the effective dose constitutes such a large fraught with many dangers, both for the volume oE fluid that It Is prohibitive for use in a dart, although 2.0 mg of ketamine has human attendant and for the bears been administered in two darts to a bear for themselves. When these bears are kept in immobilization before maintenance on captlvity, many occasions arise when halothane oxygen anesthesia. 16 veterinary attention is called for and Etorphine induces analgesia and therefore, an adequate means ~f reSb-aint is catatonia. The dose-related side effects are required. When anesthesia was first excitement, tachycardia, raised blood considered for use in bears, either volatile pressure, opisthotonus, mydriasis, anesthetics, e.g., ether (administered in an hyperpyrexia, respiratory depression, cough ether chamber) or intravenous anesthetics center depression, inhibition of e.g., chloral hydrate, morphine, and ' gastrointestinal motility, and antidluresis.1,1l halothane (administered with the bear in a Etorphlne is unique in that it is safer to glve squeeze cage) were used. S 80th of these the maximum dosage rather than the methods requlred the use of physical minimum effective dosage, as underdoslng restraint, which caused the animal results in marked hyperexcitability and considerable stress and also increased the hyperventilation leading to a possible fatal risk of injury to the bear. alkalosis. Bears have been found to be one The administration of narcotics and other drugs from afar, by a projectile syringe or of the more sensitive species to the effects dart, lessens the necessity of physical of etorphine, with the dosage per kilogram being relatively low. It has been used in capture. 12 Only those narcotics effective in small doses are satisfactory because of the polar bears at dosages of 2-3 mg/animaJ,7 0.5 mg/45 kg body weight20,22 or 6-8 limited capacity of the darts. p./kg.2 For brown bears, 8-10 p./kg has Phencyclidine, a disassociative anesthetic been suggested. 2 was the first drug that could be used in a ' Various tranquilizers have been dart for the immobilization of bears. Used administered simultaneously with etorphine alone, its side effects of excitement and to reduce the excitement effects. 22 Etorphlne tonic/clonic muscle spasms were marked, is now sold in some parts of the world but these were reduced by the simultaneous use of a variety of tranquilizers. 6,18,24 already mixed with a phenothiazine tranquilizer under the trade names of "Large Succinylcholine chloride, a depolarizing Animal Immobilon® " and "Small Animal muscle relaxant, was used as a "knock- Immobilon® ." Some workers have found that the addition of acepromazine to Hellabrunn, Siebenbrunner Sir. 8, 0-8000 Munchen 90 ~~~park etorphine results in too much residual 11 sedation.2 could precipitate unwanted excitement and This report discusses the results of five aggression. Such reactions either effectively years experience in the use of Large Animal increased the dose of Immobilin required, or Immobilon® in Tierpark Hellabrunn, induced tachycardia and rapid respiration primarily in the polar bear but also in the predisposing to the development of brown bear. hyperventilation, thus leading to severe Materials and Methods alkalosis and possibly death. 1 The depth of anesthesia was initially The agents used in the immobilization of ascertained by gently stimulating the pinna the bears were: of the ear, with a stick (such as a broom 1) Immobilon® - (Large Anima!) - Reckitt handle), to elicit the ear twitch reflex. This and Colman. One ml contains 2.45 mg reflex is used as the head is the last part of etrophine (as hydrochloride) and 10 mg the body affected by the immobilization. acepromazine maleate, a neurolept Once the ear twitch reflex was suppressed it analgesie, 2) Revivon® - Reckitt and was deemed safe to enter the endosure and Colman. One ml contains 3 mg attend to the anima\. diprenorphine (as hydrochloride) (with The depth of anesthesia was considered methylene blue 0.001 % and chlorocresch to be %), 0.1 areversal agent, direct antagonist to a) Unsatis/actory - if the animal could etorphine), 3) Rompun® - Bayer. One ml actively move its limbs and even stand up, contains 100 mg xylazine, a tranquilizer and when its ear pinna was stimulated or if the analgesie agent, and 4) Kinetin® animal was approached. - Schering. One ampule contains 150 IU b) Satis/actory - if the ear twitch reflex had hyaluronidase as a dry substance. Used to gone, but stimulaton elicited physical increase the uptake into the blood of the reactions, such as limb flexion. This level of active agents from the musde. anesthesia was considered to be adequate One ampule of kinetin was added to the for transferring the bear from one place to immobilizing agent, either Immobilon or another or for procedures which are not Immobilon plus Rompun, which was then very painful (such as the taking of blood administered to the animal intramuscularly sampIes). using the Telinject blowpipe and dart system c) Light - if the ear twitch reflex was (Telinject G.m.b.H.).23 present and feeble movements could be The bears were either put singly into their elicited on stimulation. small sleeping cages and darted from the d) Operation Deep (op. deep) - if reaction outside through the bars, using the 1.0 m to painful stimuli was also suppressed. blowpipe , or were darted in the main endosure, using the 2.0 m blowpipe e) Too Deep - if there were signs of (maximum range 15 m). Darts of 2 ml respiratory embarrassment. volume were used in all cases. The bear, in If during the handling of the animal the particularly the polar be ar , is endowed with level of narcosis was not considered to be a thick layer of subcutaneous fat, wh ich deep enough, a further dose of Immobilon may be up to 7.5 cm thick in some areas of was injected intramuscularly, with up to a the body. Therefore, the darts were aimed quarter of the initial dose being given. at the neck and shoulder musculature, When the handling of the animal was where the fat is thinnest, to assure that the finished, all equipment and auxiliary injection was intramuscular and not intrafat. personnel were removed from the bear's After darting, the anima I was left cage or endosure and a computed dose of undisturbed until fully immobilized, since Revivon was given (double the dose of continual dose assessment of the animal Immobilon) intramuscularly, plus 1 ml 12 subcutaneously to prevent the danger of narcosis recurring later due to the E'" E'" Q)- gj enterohepatic recirculation of the etorphine. 'Co'" ~ c. (/):::.- Q) .... The vein of choice was the tongue vein, as w '"0; '" :; :;'" this was always readily available, whereas o o the femoral vein, wh ich is also suggested. '" '" ~" ~" was far more difficult to use. As the tongue vein is very thin walled, it is better not to c: c: .2 draw back on the syringe, as this will cause .2 ~ the vein to collapse. Any bleeding after the .~o= _-.0 Q . needle was removed, was stemmed by the 'C 0 ",1!1 E: E .-c:"'" application of firm press ure . If the vein .§ C:o -c:"'Q)O could not be used, the Revivon was given ÜQ) intramuscularly into the tongue muscles. - "Ci)'" Once the Rivivon was administered, prompt ~_ 0 Q)o~ exit from cage was required as the speed of ...J '" recovery is very fast. Z Animals showing any signs of hangover, ... aI e.g., drowsiness, during the following 24 i5 hours post-immobilization, were given more a. Q) Revivon intramuscularly by dart (0.5-1.0 ml). =ö c: Results ..: 0 Fifty be ars were immobilized in the five year period from 1975 to 1980 (Tables I ~~ ~:ä ~ c. and 11), thirty-three with Immobilon alone ~ 0 o $ E _",'" 'C and seventeen with ImmobiIon plus E ci Rompun. No fatalities due to the Q) ~ 0 .r:. immobilization occurred. - c: ö ~G)c The side effects seen were: o E· ~ ".- E a) Muscular spasms caused by etorphine, :l 'CI-- Ul E: when Immobilon was used alone. a:Q) b) Three of the bears suffered drowsiness following reversal of the immobilization [Table No. 1(10), 1(14), and 11(1)] extending to the next day in one of the bears [No. 1(10)]. LO C'J c) One polar be ar [Table No. 1(25)] N experienced epileptiform convulsions while under the effects of the ImmobiIon but it recovered uneventfully on administration of + + 8 g Revivon. Perhaps convulsions were related ~ to a head injury sustained 14 days x Q) previously. (/) The average induction time was about thirteen minutes for ImmobiIon alone, and fifteen minutes for Immobilon plus Rompun. o It is possible that the induction times of over z ,...: N 13 Dose Second Dose "ImmobIlon" "Rompun" Inductlon Level TIme After Level Indlcatlon No.