Journal of Zoo and Wildlife Medicine 33(2): 157±162, 2002 Copyright 2002 by American Association of Zoo Veterinarians

REPEATED CHEMICAL IMMOBILIZATION OF A CAPTIVE GREATER ONE-HORNED RHINOCEROS (RHINOCEROS UNICORNIS), USING COMBINATIONS OF ETORPHINE, DETOMIDINE, AND

Mark W. Atkinson, B.V.Sc., M.R.C.V.S., Bruce Hull, D.V.M., A. Rae Gandolf, D.V.M., and Evan S. Blumer, V.M.D.

Abstract: An adult, 23 yr-old, male greater one-horned rhinoceros (Rhinoceros unicornis) was repeatedly immobi- lized with combinations of etorphine, detomidine, and ketamine to provide medical and surgical care to chronic, bilateral, soft tissue lesions on the hind feet and to collect semen by electroejaculation. The rhinoceros was successfully immobilized on 24 occasions over a 55 mo period at approximately 8±10 wk intervals, 17 times with a combination of etorphine and detomidine (M99±D, i.m.) by projectile dart and seven times with a combination of etorphine, ketamine, and detomidine (M99±K±D, i.m.) by pole syringe. The combination of etorphine, detomidine, and ketamine repeatedly and safely induced prolonged anesthesia, and a suitable drug combination includes 3.5±3.8 mg etorphine, 14 mg detomidine, and 400 mg ketamine (M99-K-D) administered i.m. into the neck. Key words: Etorphine, detomidine, ketamine, chemical immobilization, greater one-horned rhinoceros, Rhinoceros unicornis.

INTRODUCTION Prolonged lateral recumbency places a large rhi- The greater one-horned rhinoceros (Rhinoceros noceros at risk of hypoventilation, ventilation±per- unicornis) has been chemically restrained in the fusion mismatching, pulmonary shunting, progres- 8,22 ®eld using etorphine and ,3 although sive atalectasis, and hypoxemia. This necessi- there are few references to chemical immobilization tates the recognition and careful evaluation of ox- of this species in captivity, where immobilization ygenation trends and the degree of hypoxemia may be necessary for physical examination, sur- during anesthesia. gery, reproductive manipulation, or medical treat- Detomidine is a potent alpha-2 adrenoceptor ag- ment.1,10,11 The need for intervention is evidenced onist that produces effective and prolonged anal- 9 by the large number of medical problems, particu- gesia in the horse and is a suitable agent 16 larly chronic, nonhealing foot lesions in adult male in horses with chronic hoof pain. Ketamine is fre- R. unicornis within the zoo population, which may quently used as a supplemental agent to ± require frequent chemical restraint to facilitate alpha-2 anesthesia in nondomestic perisso- treatment.20,24,25 dactylids. In tapirs, ketamine prolongs the immo- , such as etorphine, provide excellent re- bilization period, increases the depth of sedation, straint and analgesia in many nondomestic spe- and maintains a desired plane of anesthesia induced 4,23 cies,5,6,7,17 including the rhinoceros.3,7,14,15,26 In com- by ±xylazine. Alpha-2 re- bination with alpha-2 adrenergic agonists such as duce ketamine requirements by their effect on the detomidine, etorphine provides prolonged and con- central nervous system and by increasing ketamine 12 trolled anesthesia with good muscle relaxation. The bioavailability. addition of alpha-2 agonists improves the quality of CASE REPORT induction and maintenance of opioid immobiliza- tion.12 Opioids, however, cause respiratory depres- A captive, adult, 23-yr-old, male greater one- sion and hypoxia in rhinoceroses.8,13 A chemical horned rhinoceros (R. unicornis) was immobilized immobilization regimen using ±butorpha- 24 times using combinations of etorphine (M99- nol combinations has been used successfully in oth- Ten, Wildlife Pharmaceuticals, Fort Collins, Colo- er rhinoceros species.18 rado 80524 USA), detomidine (Dormosedan, P®zer, Exton, Pennsylvania 19380, USA), and ketamine (Ketaset, Fort Dodge Laboratories, Inc., Fort From The Wilds, 14000 International Road, Cumber- land, Ohio 43732, USA (Atkinson, Gandolf, Blumer); and Dodge, Iowa 50501, USA) between June 1996 and the College of Veterinary Medicine, The Ohio State Uni- January 2001. The primary purpose of the immo- versity, 601 Tharp Street, Columbus, Ohio 43210, USA bilizations was to permit long-term medical and (Hull). Correspondence should be directed to Dr. Atkin- surgical care to chronic, active, bilateral, hind foot son. soft tissue lesions. On eight of the occasions, semen

157 158 JOURNAL OF ZOO AND WILDLIFE MEDICINE collection by electroejaculation was attempted after D administrations, respectively. Mean Ϯ SD times provision of foot care. of immobilization were 65.8 Ϯ 22.2 min and 76.6 The anesthetic drugs are referred to by alpha- Ϯ 25.5 min for M99±D and M99±K±D procedures, numeric designation, with etorphine ϭ M99, de- respectively. To achieve consistent immobilization tomidine ϭ D, and ketamine ϭ K.21 Immobilizing results, the etorphine dosage was gradually in- doses of M99±D (n ϭ 17) were administered i.m. creased, from 3 mg in June 1996 to 3.8 mg in June by projectile dart (PneuDart, Inc., Williamsport, 2000. To maintain an adequate plane of anesthesia Pennsylvania 17703, USA). Combinations of M99± during procedures, the mean total amounts of sup- K±D (n ϭ 7) were administered i.m. with a spring- plementary ketamine administered were 767.7 Ϯ loaded pole syringe (DanInject, Wildlife Pharma- 537.9 mg for M99±D and 428.6 Ϯ 215.8 mg for ceuticals). Each restraint episode was performed M99±K±D. within a 36-m2 concrete stall with sliding doors, Heart rates were 45±75 (x ϭ 60 Ϯ 11.11) beats/ steel pipe fence, and gates. The ¯oor of the stall min and 46±69 (x ϭ 56 Ϯ 8.07) beats/min for was thickly bedded with hardwood mulch. The an- M99±D and M99±K±D immobilizations, respec- imal's estimated weight was 2,500 kg. tively. Respiratory rates were 8±19 (x ϭ 11 Ϯ 2.62) For procedures using M99±D the mean immo- breaths/min and 8±14 (x ϭ 9 Ϯ 3.43) breaths/min bilizing dosages were 3.36 Ϯ 0.2 mg i.m. and 12.65 for M99±D and M99±K±D immobilizations, re- Ϯ 1.54 mg i.m., respectively. For M99±K±D the spectively. Rectal body temperatures were 36± mean immobilizing dosages were 3.71 Ϯ 0.15 mg 38.4ЊC(x ϭ 36.9 Ϯ 1.03) and 37.1±38.4ЊC(x ϭ i.m., 400 mg i.m., and 14 mg i.m., respectively (Ta- 37.8 Ϯ 0.59) for M99±D and M99±K±D immobi- ble 1). To achieve consistent immobilization results, lizations, respectively. Pulse oximetry readings the M99±D dosage was gradually increased, from were 70±98% (x ϭ 87% Ϯ 5.15) and 80±95% (x 3 mg in June 1996 to 3.5 mg in June 2000 for ϭ 87% Ϯ 4.26) for M99±D and M99±K±D im- M99±D and from 3.5 mg in November 1999 to 3.8 mobilizations, respectively. After administration of mg in January 2001 for M99±K±D. For both com- , mean times to standing were 3.5 Ϯ 1.7 binations, ketamine (100±250 mg i.v. by hand sy- min and 2.5 Ϯ 0.6 min for M99±D and M99±K±D ringe into an auricular vein) was administered at procedures, respectively. Reversal was considered 20- to 30-min intervals (or as required) to lengthen smooth and controlled for all procedures but was the immobilization period and increase the depth of always accompanied by transient, mild to moderate sedation. Total dose of supplemental ketamine was facial pruritis. 100±2,250 mg per restraint episode, depending on the depth and duration of anesthesia required. At DISCUSSION the termination of each procedure, the effects of Both drug combinations proved effective for re- etorphine were antagonized by administration of peated immobilization of one adult R. unicornis. naltrexone (150±300 mg, half i.v. and half i.m.). Despite adequate immobilization after drug admin- No reversal agent was administered to antagonize istration by darting, dif®culties were encountered. the effects of detomidine. Although the massive musculature and relatively Time from injection to recumbency, total im- thin skin make the neck a suitable dart site for adult mobilization time, and time to standing after rever- rhinoceroses, such peculiar anatomical features as sal were recorded. Patient monitoring included car- the large skin folds of the neck signi®cantly reduce dio-pulmonary auscultation, measurement of rectal the target area in R. unicornis. body temperature (ЊC), and pulse oximetry Limitations of dart size also precluded the addi- (pneuPAC, Bedfordshire, U.K.) with the probe tion of other agents to the immobilizing dose. A placed over a lingual artery, dependant ear, or pe- pole syringe allows rapid administration of a rela- ripheral skin fold. Arterial blood oxygenation tively large volume, but success is limited by how trends (SaO2) were continuously recorded during all closely the operator can approach the animal. In the immobilizations. In 15 out of 24 immobilization ep- present case, suitable facilities, skilled animal man- isodes, 100% oxygen was administered through a agement staff, and a relatively tractable patient al- nasal cannula by a demand valve resuscitator lowed successful drug administration. (LSP1, Allied Health Care Products, St. Louis, Mis- Multiple confounding variables make the relative souri 63110, USA) capable of ¯ow rates up to 160 advantages and disadvantages of each drug com- L/min. Oxygen was administered on the basis of bination dif®cult to ascertain. Subjectively, the an-

SaO2 trends (decreasing trends of SaO2 below 80%). esthetic events improved when the etorphine dos- Mean Ϯ SD times to recumbency were 16.6 Ϯ 8.9 age was increased, ketamine was administered with min and 7.6 Ϯ 2.4 min after M99±D and M99±K± the immobilizing combination, and the drugs were ATKINSON ET AL.ÐRHINOCEROS IMMOBILIZATION 159 (%) 2 3.95 5.15 O a 87.43 87 93 88 86 89 80 89 87.06 85 78 97 87 85 92 92 87 84 93 88 76 86 85 90 89 86 9.71 3.45 7 8 7 6 2.62 8 8 8 8 rate min) S 13 14 13 11.12 10 12 12 12 11 12 11 11 11 19 13 12 11 (breaths/ Respiratory time 2.43 0.53 3 2 3 3 2 2 2 3.47 1.65 3 4 2 4 2.5 3 2 3 6 2 5 8 2 4 4 2.5 2 (min) Reversal ) repeatedly immobilized with etorphine (M99), (mg) 18.90 46.13 242.86 250 200 250 250 250 250 250 229.41 250 250 300 300 200 250 250 200 250 300 200 150 175 175 200 250 200 Naltrexone time 76.57 24.53 52 44 95 82 90 62 65.76 22.20 55 49 59 61 40 96 74 83 64 47 56 97 56 44 67 48 (min) 111 122 Rhinoceros unicornis Immobilization (mg) K suppl. 428.57 215.75 400 500 300 750 200 650 200 767.65 537.92 600 500 600 400 900 600 600 100 250 600 600 600 350 1,200 2,250 1,500 1,400 7.57 2.44 8 6 4 6 8 8.87 5 8 5 time (min) 10 11 16.59 10 11 15 27 12 20 33 36 18 15 19 15 21 12 Induction 0.00 0.00 0.00 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 400.00 400 400 400 400 400 400 400 0.00 1.54 14.00 14 14 14 14 14 14 14 12.65 14 14 12 12 12 14 14 14 14 10 10 10 12 14 13 14 12 M99 (mg) D (mg) K (mg) 3.71 0.15 3.5 3.5 3.8 3.8 3.8 3.8 3.8 3.36 0.20 3.5 3.5 3.5 3.5 3.2 3.4 3.4 3.5 3.5 3 3 3 3.3 3.5 3.6 3.5 3.2 Date of event Feb 2000 Jun 2000 Aug 2000 Oct 2000 Dec 2000 Jan 2001 Aug 1999 Apr 2000 Jan 1998 Mar 1998 Nov 1998 Dec 1998 Feb 1999 Mar 1999 Jun 1999 Aug 1996 Sep 1996 Dec 1996 Jan 1997 Feb 1997 Apr 1997 Nov 1997 Drug dosages and anesthetic parameters of an adult, male greater one-horned rhinoceros ( Table 1. Mean SD M99-K-D Nov 1999 Mean SD M99-D Jun 1996 detomidine (D), and ketamine (K) combinations. 160 JOURNAL OF ZOO AND WILDLIFE MEDICINE

Table 2. Selected anesthetic parameters of an adult, male greater one-horned rhinoceros (Rhinoceros unicornis) repeatedly induced with 3.5 mg etorphine (M99) and 14 mg detomidine (D), and with the same dosages of M99-D and 400 mg ketamine (K).

Respiratory Immobili- rate Induction K suppl. zation time Naltrexone Reversal (breaths/

Date of event time (min) (mg) (min) (mg) time (min) min) SaO2 (%)

Induced with M99-D Jan 1997 19 600 56 175 4 13 85 Apr 1997 21 1,400 67 250 2.5 12 89 Mar 1999 36 2,250 122 200 3 11 87 Jun 1999 5 1,500 83 250 6 11 84 Aug 1999 10 600 55 250 3 8 85 Apr 2000 11 500 49 250 4 10 78 Mean 17.00 1,141.67 72.00 229.17 3.75 10.83 84.67 SD 11.05 696.00 27.28 33.23 1.25 1.72 3.72 Induced with M99-D and 400 mg K Nov 1999 8 400 111 250 3 7 87 Feb 2000 6 500 52 200 2 8 93 Mean 7.00 450.00 81.50 225.00 2.50 7.50 90.00 SD 1.41 70.71 41.72 35.36 0.71 0.71 4.24

administered by pole syringe. With time, there was Eight procedures used identical doses of etor- a need to gradually increase the dosage of etorphine phine (3.5 mg) and detomidine (14 mg). Six did to achieve consistently adequate immobilization not use ketamine during induction, whereas two did during the 55 mo of this study. Although the in- (Table 2). Although this data subset is limited, it creased dosages of etorphine that were used as the may be useful in evaluating the potential improve- study progressed elevated the risk of hypoxemia ments offered by the addition of ketamine to the and respiratory depression, the quality of anesthesia immobilizing dose. They suggest three likely ad- remained good throughout the study period, and no vantages of M99±K±D over M99±D: induction negative effects were noted. Opioid drug tolerance time is reduced, total amount of ketamine required may explain the need for a gradually increasing to maintain adequate anesthesia is decreased, and etorphine dosage. Anesthetic reversal was consis- reversal time after antagonism is shorter. In terms tently smooth, controlled, and rapid. Because of the of the mean amount of ketamine (in mg) required controlled conditions, postanesthetic monitoring, per minute of mean immobilization time (time from and desire for prolonged analgesia after surgery, the injection of immobilizing drugs to complete antag- effects of detomidine were not antagonized. The onism), 15.9 mg ketamine/min was required during facial pruritis may have been mediated by the ex- M99±D procedures, whereas 10.4 mg ketamine/ ogenous opioid, although this is uncertain and re- min was required during M99±K±D procedures. mains under investigation. Regardless of anesthetic regimen, arterial oxygen The mean induction time, amount of ketamine saturation values monitored by pulse oximetry were supplementation required to maintain anesthesia, similar between groups, with a mean SaO2 value of duration of immobilization, and reversal time dif- 87 Ϯ 5.2% for M99±D procedures versus 87 Ϯ fered according to anesthetic protocol (Table 1). 3.9% for M99±K±D procedures. Ketamine supplementation after induction was nec- Pulse oximetry is a useful adjunct to anesthetic essary to maintain or deepen the plane of anesthe- monitoring in wildlife species2, and it should al- sia, improve muscle relaxation, and permit surgical ways be used during rhinoceros immobilizations. procedures to be performed without premature Decreased SaO2 values may be a result of the com- arousal of the animal. Despite the variation in drug bined respiratory depressant effects of etorphine dosages, subjective assessment of the data suggests and detomidine as well as the effects of lateral re- that, when compared with M99±D, M99±K±D pro- cumbency that likely exacerbate ventilation±perfu- duces more rapid induction and is characterized by sion mismatch. Based on the normal oxygen±he- a reduced requirement for ketamine supplementa- moglobin dissociation curve, where oxygen satu- tion and a shorter reversal time after antagonism ration below 90% re¯ects an arterial pressure of with naltrexone. oxygen of 60 mm Hg or below, pulse oximetry ATKINSON ET AL.ÐRHINOCEROS IMMOBILIZATION 161 readings below 90% may indicate a hypoxemic 6. Harthoorn, A. M. 1967. Restraint of undomesticated state in an immobilized patient.4 In the present animals. J. Am. Vet. Med. Assoc. 149: 875±880. study, in 11 out of 17 (65%) immobilizations using 7. Harthoorn, A. M. 1973. The drug immobilization of M99±D and six out of seven (86%) using M99±K± large wild herbivores other than antelopes. In: Young, E. D, mean S O values were below 90%. Values of (ed.). The Capture and Care of Wild Animals. Human and a 2 Rouseau, Cape Town, South Africa. Pp. 51±61. S O during etorphine anesthesia in white rhinoc- a 2 8. Heard, D. J., J. H. Olsen, and J. Stover. 1992. Car- eros are commonly 80±85% and may fall below diopulmonary changes associated with chemical immo- 15,17,19 50% in some cases. Because of the potential bilization and recumbency in a white rhinoceros (Cera- inaccuracies of peripheral pulse oximetry monitor- totherium simum). J. Zoo Wildl. Med. 23: 197±200. ing and our lack of knowledge of R. unicornis ox- 9. Jochle, W., and D. Hamm. 1986. 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