• View in gallery
    Figure 1

    Mean ± SEM heart rate for 12 red-footed tortoises (Chelonoidis carbonaria) following dexmedetomidine-midazolam-ketamine (DMK) injection. Time 0 represents the time when DMK injection was completed. Heart rate decreased significantly (P < 0.001) over time.

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    Figure 2

    Mean ± SEM respiratory rate for the tortoises in Figure 1 following DMK injection. Respiratory rate decreased significantly (P < 0.001) over time.

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    Figure 3

    Mean ± SEM respiratory rate for the tortoises in Figure 1 from 5 to 60 minutes after DMK injection. After removing the time 0 measurement from the analysis, respiratory rate was still significantly (P = 0.014) decreased over time.

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    Figure 4

    Mean ± SEM cloacal temperature for the tortoises in Figure 1 following dexmedetomidine-midazolam-ketamine injection. Although there was a slight increase over time, the change was nonsignificant.

  • 1.

    Barros MS, Resende LC, Silva AG, Ferreira PD Jr. Morpho- logical variations and sexual dimorphism in Chelonoidis carbonaria (Spix, 1824) and Chelonoidis denticulata (Linnaeus, 1766) (Testudinidae). Braz J Biol. 2012;72(1):153161.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 2.

    Turtle Taxonomy Working Group. Turtles of the world: annotated checklist and atlas of taxonomy, synonymy, distribution, and conservation status. 8th ed. Chelonian Research Foundation and Turtle Conservancy. Accessed Dec 25, 2019. images.turtleconservancy.org/documents/2017/crm-7-checklist-atlas-v8-2017.pdf

    • Search Google Scholar
    • Export Citation
  • 3.

    Mueller-Paul J, Wilkinson A, Hall G, Huber L. Radial-arm-maze behavior of the red-footed tortoise (Geochelone carbonaria). J Comp Psychol. 2012;126(3):305317.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 4.

    Wilkinson A, Mueller-Paul J, Huber L. Picture–object recognition in the tortoise Chelonoidis carbonaria. Anim Cogn. 2013;16(1):99107.

  • 5.

    Meireles YS, Shinike FS, Matte DR, et al. Ultrasound characterization of the coelomic cavity organs of the red-footed tortoise (Chelonoidis carbonaria). Ciênc Rural. 2016;46(10):18111817.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 6.

    Santacà M, Miletto Petrazzini ME, Wilkinson A, Agrillo C, et al. Red-footed tortoises (Chelonoidis carbonaria) do not perceive the Delboeuf illusion. Can J Exp Psychol. 2020;74(3):201206.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 7.

    Read MR. Evaluation of the use of anesthesia and analgesia in reptiles. J Am Vet Med Assoc. 2004;224(4):547552.

  • 8.

    Sladky KK, Mans C. Clinical anesthesia in reptiles. J Exot Pet Med. 2012;21(1):1731.

  • 9.

    Knotek Z. Alfaxalone as an induction agent for anaesthesia in terrapins and tortoises. Vet Rec. 2014;175(13):327329.

  • 10.

    Lock BA, Heard DJ, Dennis P. Preliminary evaluation of medetomidine/ketamine combinations for immobilization and reversal with atipamezole in three tortoise species. Bull Assoc Rept Amphib Vet. 1998;8(4):69.

    • Search Google Scholar
    • Export Citation
  • 11.

    Sleeman JM, Gaynor J. Sedative and cardiopulmonary effects of medetomidine and reversal with atipamezole in desert tortoises (Gopherus agassizii). J Zoo Wildl Med. 2000; 31(1):2835.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 12.

    Divers SJ. Endoscopic sex identification in chelonians and birds (psittacines, passerines, and raptors). Vet Clin North Am Exot Anim Pract. 2015;18(3):541554.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 13.

    Emmel ES, Rivera S, Cabrera F, Blake S, Deem SL. Field anesthesia and gonadal morphology of immature Western Santa Cruz tortoises (Chelonoidis porteri). J Zoo Wildl Med. 2021;51(4):848855.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 14.

    Polanco JB, Mamprim MJ, Silva JP, et al. Computed tomographic and radiologic anatomy of the lower respiratory tract in the red-foot tortoise (Chelonoidis carbonaria). Pesqui Vet Bras. 2020;40(8):637646.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 15.

    Campos R, Justo AF, Jacintho FF, et al. Pharmacological and transcriptomic characterization of the nitric oxide pathway in aortic rings isolated from the tortoise Chelonoidis carbonaria. Comp Biochem Physiol C Toxicol Pharmacol. 2019;222:8289.

    • Search Google Scholar
    • Export Citation
  • 16.

    Sousa RP, Nogueira LF, Pessoa GT, Feitosa ML, Carvalho MA, Moura WL. Morphological analysis of peripheral blood cells of Chelonoidis carbonaria (Spix, 1824). Biosci J. 2015;31(1):242247.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 17.

    De Santi M, Cruz N, Barranco G, Lima G. Cutaneous melanoma in a Red-footed tortoise (Chelonoidis carbonaria). J Exot Pet Med. 2020;34:4447.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 18.

    Monteiro ER, da Silva EL, Santos MG, Rossi JL Jr, Ferreira PD Jr. Pharmacological restraint of red-footed tortoises using combinations of ketamine, midazolam and butorphanol. Rev Academica Cienc Anim. 2011;9(3):295298.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 19.

    Arnett-Chinn ER, Hadfield CA, Clayton LA. Review of intramuscular midazolam for sedation in reptiles at the National Aquarium, Baltimore. J Herpetologic Med Surg. 2016;26(1–2):5963.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 20.

    Mans C, Sladky KK, Schumacher J. General anesthesia. In: Divers SJ, Stahl SJ, eds. Mader’s Reptile and Amphibian Medicine and Surgery. 3rd ed. WB Saunders; 2019:447464.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 21.

    Emery L, Parsons G, Gerhardt L, Schumacher J. Sedative effects of intranasal midazolam and dexmedetomidine in 2 species of tortoises (Chelonoidis carbonaria and Geochelone platynota). J Exot Pet Med. 2014;23(4):380383.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 22.

    Mans C, Foster JD. Endoscopy-guided ectopic egg removal from the urinary bladder in a leopard tortoise (Stigmochelys pardalis). Can Vet J. 2014;55(6):569572.

    • Search Google Scholar
    • Export Citation
  • 23.

    Mans C, Sladky KK. Endoscopically guided removal of cloacal calculi in three African spurred tortoises (Geochelone sulcata). J Am Vet Med Assoc. 2012;240(7):869875.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 24.

    Karklus AA, Sladky KK, Johnson SM. Respiratory and antinociceptive effects of dexmedetomidine and doxapram in ball pythons (Python regius). Am J Vet Res. 2021;82(1):1121.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 25.

    Hansen LL, Bertelsen MF. Assessment of the effects of intramuscular administration of alfaxalone with and without medetomidine in Horsfield’s tortoises (Agrionemys horsfieldii). Vet Anaesth Analg. 2013;40(6):e68e75.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 26.

    Morici M, Interlandi C, Costa GL, Di Giuseppe M, Spadola F. Sedation with intracloacal administration of dexmedetomidine and ketamine in yellow-bellied sliders (Trachemys scripta scripta). J Exot Pet Med. 2017;26(3):188191.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 27.

    Dennis PM, Heard DJ. Cardiopulmonary effects of a medetomidine-ketamine combination administered intravenously in gopher tortoises. J Am Vet Med Med. 2002;220(10):15161519.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 28.

    Díaz M, Becker DE. Thermoregulation: physiological and clinical considerations during sedation and general anesthesia. Anesth Prog. 2010;57(1):2533.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 29.

    Ikeda T, Kazama T, Sessler DI, et al. Induction of anesthesia with ketamine reduces the magnitude of redistribution hypothermia. Anesth Analg. 2001;93:934938.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 30.

    Kischinovsky M, Duse A, Wang T, Bertelsen MF. Intramuscular administration of alfaxalone in red-eared sliders (Trachemys scripta elegans)–effects of dose and body temperature. Vet Anaesth Analg. 2012;40(1):1320.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 31.

    Greer LL, Jenne KJ, Diggs HE. Medetomidine-ketamine anesthesia in red-eared slider turtles (Trachemys scripta elegans). Contemp Top Lab Anim Sci. 2001;40(3):911.

    • Search Google Scholar
    • Export Citation
  • 32.

    Holz P, Holz RM. Evaluation of ketamine, ketamine/xylazine, and ketamine/midazolam anesthesia in red-eared sliders (Trachemys scripta elegans). J Zoo Wildl Med. 1994;25(4):531537.

    • Search Google Scholar
    • Export Citation
  • 33.

    Bisetto SP, Melo CF, Carregaro AB. Evaluation of sedative and antinociceptive effects of dexmedetomidine, midazolam and dexmedetomidine–midazolam in tegus (Salvator merianae). Vet Anaesth Analg. 2018;45(3):320328.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 34.

    Bennett RA. Reptile anesthesia. Semin Avian Exotic Pet med 1998;7(1):3040.

  • 35.

    Hernandez-Divers SJ, Stahl SJ, Farrell R. An endoscopic method for identifying sex of hatchling Chinese box turtles and comparison of general versus local anesthesia for coelioscopy. J Am Vet Med Assoc. 2009;234(6):800804.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 36.

    Kuchling G. Endoscopic sex determination in juvenile freshwater turtles, Erymnochelys madagascariensis: morphology of gonads and accessory ducts endoscopic sex determination in juvenile freshwater turtles. Chelonian Conserv Biol. 2006;5(1):6773.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 37.

    Kuchling G, Goode E, Praschag P. Endoscopic imaging of gonads, sex ratio and temperature dependent sex determination in captive bred juvenile Burmese star tortoises Geochelone platynota. Asian Herpetol Res. 2011;2(4):240244.

    • Search Google Scholar
    • Export Citation
  • 38.

    Kuchling G, Goode EV, Praschag P. Endoscopic imaging of gonads, sex ratio, and temperature-dependent sex determination in juvenile captive-bred radiated tortoises, Astrochelys radiata. Chelonian Res Monogr. 2013;6:113118.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 39.

    Shepard MK, Divers S, Braun C, Hofmeister EH. Pharmacodynamics of alfaxalone after single-dose intramuscular administration in red-eared sliders (Trachemys scripta elegans): a comparison of two different doses at two different ambient temperatures. Vet Anaesth Analg. 2013;40(6):590598.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 40.

    McGuire JL, Hernandez SM, Smith LL, Yabsley MJ. Safety and utility of an anesthetic protocol for the collection of biological samples from gopher tortoises. Wildl Soc Bull. 2014;38(1):4350.

    • Crossref
    • Search Google Scholar
    • Export Citation

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Evaluation of the effects of a dexmedetomidine-midazolam-ketamine combination administered intramuscularly to captive red-footed tortoises (Chelonoidis carbonaria)

David EsharFrom the Department of Clinical Sciences, College of Veterinary Medicine, Kansas State University, Manhattan, KS 66506

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Theresa A. RooneyFrom the Department of Clinical Sciences, College of Veterinary Medicine, Kansas State University, Manhattan, KS 66506

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Sara GardhouseFrom the Department of Clinical Sciences, College of Veterinary Medicine, Kansas State University, Manhattan, KS 66506

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Hugues BeaufrèreDepartment of Clinical Studies, Ontario Veterinary College, University of Guelph, Guelph, ON N1G 2W1, Canada.

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Abstract

OBJECTIVE

To evaluate the effects of a dexmedetomidine-midazolam-ketamine (DMK) combination administered IM to captive red-footed tortoises (Chelonoidis carbonaria).

ANIMALS

12 healthy adult red-footed tortoises.

PROCEDURES

In a prospective experimental study, DMK (0.1, 1.0, and 10 mg/kg, respectively) was administered IM as separate injections into the right antebrachium. Atipamezole (0.5 mg/kg, IM) and flumazenil (0.05 mg/kg, SC) were administered into the left antebrachium 60 minutes later. Times to the first treatment response and maximal treatment effect after DMK administration and time to recovery after reversal agent administration were recorded. Vital signs and reflexes or responses to stimuli were assessed and recorded at predetermined intervals.

RESULTS

DMK treatment produced deep sedation or light anesthesia for ≥ 20 minutes in all tortoises. Induction and recovery were rapid, with no complications noted. Median times to first response, maximum effect, and recovery were 4.5, 35, and 14.5 minutes, respectively. Two tortoises required additional reversal agent administration but recovered < 20 minutes after the repeated injections. Mean heart and respiratory rates decreased significantly over time. All animals lost muscle tone in the neck and limbs from 35 to 55 minutes after DMK injection, but other variables including palpebral reflexes, responses to mild noxious stimuli (eg, toe pinching, tail pinching, and saline ([0.9 NaCl] solution injection), and ability to intubate were inconsistent.

CONCLUSIONS AND CLINICAL RELEVANCE

DMK administration produced deep sedation or light anesthesia with no adverse effects in healthy adult red-footed tortoises. At the doses administered, deep surgical anesthesia was not consistently achieved. Anesthetic depth must be carefully evaluated before performing painful procedures in red-footed tortoises with this DMK protocol.

Abstract

OBJECTIVE

To evaluate the effects of a dexmedetomidine-midazolam-ketamine (DMK) combination administered IM to captive red-footed tortoises (Chelonoidis carbonaria).

ANIMALS

12 healthy adult red-footed tortoises.

PROCEDURES

In a prospective experimental study, DMK (0.1, 1.0, and 10 mg/kg, respectively) was administered IM as separate injections into the right antebrachium. Atipamezole (0.5 mg/kg, IM) and flumazenil (0.05 mg/kg, SC) were administered into the left antebrachium 60 minutes later. Times to the first treatment response and maximal treatment effect after DMK administration and time to recovery after reversal agent administration were recorded. Vital signs and reflexes or responses to stimuli were assessed and recorded at predetermined intervals.

RESULTS

DMK treatment produced deep sedation or light anesthesia for ≥ 20 minutes in all tortoises. Induction and recovery were rapid, with no complications noted. Median times to first response, maximum effect, and recovery were 4.5, 35, and 14.5 minutes, respectively. Two tortoises required additional reversal agent administration but recovered < 20 minutes after the repeated injections. Mean heart and respiratory rates decreased significantly over time. All animals lost muscle tone in the neck and limbs from 35 to 55 minutes after DMK injection, but other variables including palpebral reflexes, responses to mild noxious stimuli (eg, toe pinching, tail pinching, and saline ([0.9 NaCl] solution injection), and ability to intubate were inconsistent.

CONCLUSIONS AND CLINICAL RELEVANCE

DMK administration produced deep sedation or light anesthesia with no adverse effects in healthy adult red-footed tortoises. At the doses administered, deep surgical anesthesia was not consistently achieved. Anesthetic depth must be carefully evaluated before performing painful procedures in red-footed tortoises with this DMK protocol.

Introduction

The red-footed tortoise (Chelonoidis carbonaria) is a medium-sized (carapace length, 30 to 40 cm) chelonian species from South America and Central America.1,2 These tortoises are commonly kept as pets or in zoological collections and are frequently studied in behavioral research.3,4,5,6

Chemical immobilization or anesthesia of tortoises is often necessary to enable clinicians to perform examinations or diagnostic procedures. The application of species-specific safe and effective anesthesia protocols is desired.7,8 Because chelonians tend to retract into their shells and hold their breath for prolonged periods of time, injectable anesthesia is necessary to facilitate some clinical procedures, including endotracheal intubation for invasive or potentially painful procedures.9

Suitable combinations of injectable immobilization drugs should ideally involve short-acting anesthetics with a wide safety margin that are also reversible.7,8,10,11 Regimens that involve SC or IM injection of combinations of ketamine and α2-adrenoceptor agonists are routinely used as a practical method for anesthetizing chelonians, especially in settings where inhalation anesthesia equipment is not available or when the animal retracts its head and cannot be readily intubated.8,12,13 Injections are traditionally administered in a forelimb owing to the presence of renal-portal and hepatic-portal circulation systems.8

There are some previous reports of injectable anesthesia in red-footed tortoises. In 1 study,14 a combination of ketamine hydrochloride (0.5 mg/kg) and propofol (7.0 mg/kg) was injected into the dorsal cervical sinus to facilitate radiography and CT of these animals, and maintenance with smaller doses of ketamine (0.2 mg/kg) and propofol (4.0 mg/kg) were required. In other investigations, red-footed tortoises were anesthetized with ketamine (40 mg/kg, IM) and midazolam (2.0 mg/kg, IM) for ultrasonography5 or with midazolam (2.0 mg/kg, IM), ketamine (40 mg/kg, IM), and propofol (15 mg/kg, IV) for exsanguination.15 A combination of ketamine (3.16 mg/kg) and xylazine (0.13 mg/kg) administered IM in a forelimb produced sedation sufficient for collection of a jugular venous blood sample within approximately 15 minutes in another study,16 and a combination of butorphanol (1.0 mg/kg), ketamine (40 mg/kg), and midazolam (2.0 mg/kg) administered IM in a forelimb resulted in sufficient relaxation to allow intubation for inhalation anesthesia of a red-footed tortoise undergoing surgical treatment for cutaneous melanoma.17 In 1 prospective, crossover-design study18 to evaluate drug combinations for pharmacological restraint of red-footed tortoises, the animals received each of 3 IM treatments (ketamine [30 mg/kg], ketamine [30 mg/kg] plus midazolam [1.0 mg/kg], and ketamine [30 mg/kg] plus butorphanol [1.0 mg/kg]). In that study,18 there were no significant differences among treatments for the time to onset of anesthesia (median, 6 to 16 minutes), and none of the treatments resulted in a surgical plane of anesthesia, although all treatments produced a degree of sedation that allowed jugular venous blood sample collection, oral swabbing, and biometric testing.

Midazolam has been frequently used in anesthetic protocols for reptiles because of its sedative, anxiolytic, and muscle relaxation properties.8,19,20 Dexmedetomidine can be added to protocols for chemical restraint in reptiles, as it can produce sedation and muscle relaxation and provide analgesia.20 The addition of ketamine, a dissociative, centrally acting antagonist of the N-methyl-d-aspartate receptor, can increase the level of sedation and provide some analgesia, which can facilitate the performance of more invasive procedures or result in a longer duration of immobilization.20 Intranasally administered midazolam (0.5 or 1.5 mg/kg) or dexmedetomidine (0.05 or 0.15 mg/kg) was not found to produce adequate sedation for diagnostic and handling procedures in red-footed or Indian star tortoises (Geochelone platynota).21 However, a leopard tortoise (Stigmochelys pardalis) with an ectopic egg in its urinary bladder underwent SC administration of medetomidine (0.15 mg/kg), midazolam (1.0 mg/kg), and ketamine (5 mg/kg), which produced deep sedation within approximately 30 minutes and allowed endoscopy-guided egg removal.22 Ketamine-dexmedetomidine-hydromorphone (or morphine) combinations administered IM provide anesthesia sufficient to facilitate endoscopic evaluation of gonads, although aquatic and semiaquatic species seem more sensitive to the treatment (requiring 10 to 20 mg of ketamine/kg and 0.05 mg of dexmedetomidine/kg) than terrestrial tortoises (requiring 20 to 40 mg of ketamine/kg and 0.1 mg of dexmedetomidine/kg).12 In a field study13 that included endoscopic gonadal evaluation, Western Santa Cruz tortoises (Chelonoidis porteri) were anesthetized with ketamine (10 mg/kg) and medetomidine (0.1 mg/kg) administered IM, which provided an adequate plane of anesthesia, and the medetomidine was reversed with atipamezole (0.5 mg/kg, IM).

The clinical application of injectable combinations of dexmedetomidine-midazolam-ketamine (DMK) was previously reported for several chelonian species. In African spurred tortoises (Centrochelys sulcata), SC administration of DMK (0.07 to 0.1, 1.0, and 2.5 to 5.0 mg/kg, respectively) produced moderate to deep sedation, which was suitable for cloacal endoscopy, and recovery was rapid after reversal treatment with atipamezole.23 In red-eared slider turtles (Trachemys scripta elegans), SC administration of DMK (0.1, 1.0, and 2.0 mg/kg, respectively) produced moderate to deep sedation, which was suitable for cloacal endoscopy and intrathecal injection, with turtles recovering rapidly after reversal treatment.8

The objective of the study reported here was to determine the physiologic effects and anesthetic properties of a DMK combination (0.1, 1.0, and 10 mg/kg, respectively) after IM administration to healthy red-footed tortoises. We hypothesized that this protocol would produce deep sedation (with immobilization) or anesthesia in these animals without adverse effects.

Materials and Methods

Animals

Twelve adult (6 males and 6 females) zoo-kept red-footed tortoises were included in the study as part of their annual health examination performed in the month of September. The tortoises were housed in 5 zoological collections and were observed daily by the caretakers to monitor general appearance and behavior. The animals were deemed healthy on the basis of daily observations by their keepers and the results of physical examination by a veterinarian. The study protocol was approved by each zoo’s ethics committee and the Institutional Animal Care and Use Committee at Kansas State University (No. 4366.1).

Experimental procedures

Prior to experimental procedures, animals were brought indoors to allow time for acclimation to the study room and temperature (mean, 25 °C). At this time, a physical examination was performed for each tortoise and body weight was determined with the scales available at each institution. Exclusion criteria included any history or visible signs of systemic illness (eg, signs of respiratory or cardiovascular abnormalities, infection, inflammation, trauma, or neoplasia) or discomfort. Baseline (pretreatment) vital signs were often not determined owing to the shy nature of the tortoises and the need to minimize handling stress that could potentially affect the measured anesthetic variables.

For study purposes, treatment with the DMK combination was considered successful when a stable plane of deep sedation and immobilization (complete muscle relaxation and most reflexes or responses absent) or a surgical plane of anesthesia (complete loss of all reflexes and responses, including responses to deep pain) was produced.

All injections were performed with 3-mL syringes and 22-gauge, 1.5-inch needles (Luer-Lok syringes with PrecisionGlide needles; Becton, Dickinson, and Co). Dexmedetomidine hydrochloride (Dexdomitor; 0.1 mg/kg), midazolam hydrochloride (1.0 mg/kg), and ketamine hydrochloride (Ketaset; 10 mg/kg) were administered as 3 separate IM injections in the right antebrachium.

The times to first treatment response (first observed change in at least one of the assessed variables attributable to sedation or anesthesia) and maximum treatment effect (as assessed by loss of spontaneous movement and maximum decreases in variables for the anesthetic episode) were measured from the time of DMK administration. Recovery time was measured from the time of reversal agent administration. A tortoise was deemed recovered from sedation or anesthesia when all tested reflexes or responses were present; neck, jaw, and limb muscle tone scores indicated these were present (reduced or intact [vs absent]); and the animal was able to hold its head above ground and initiate spontaneous movement.

Monitoring and assessments—Immediately after DMK injection, each tortoise was placed into a large plastic container and closely monitored. Time to first response was noted by means of visual observation during this phase.

The following variables were assessed immediately after DMK injection and at 5-minute intervals thereafter until the reversal agents were administered: vital signs (heart rate, respiratory rate, and cloacal temperature); spontaneous movement; skeletal muscle tone in the neck, jaw, forelimbs, and hind limbs; palpebral reflexes, forelimb, and hind limb withdrawal responses; and response to a tail pinch. After reversal agent administration, these measurements were repeated at 5-minute intervals until the tortoise had recovered from anesthesia.

Vital signs were assessed in the following order at each time point. Heart rate was measured with a Doppler ultrasonic flow detector (Model 811-B; Parks Medical Electronics Inc), which was directed toward the heart in a cervicobrachial acoustic window. Respiratory rate was assessed by observation of skin movement in the region between the neck and shoulder region or the femoral fossa. Cloacal temperature was monitored with a laboratory-grade thermometer (MicroTherma 2T; Braintree Scientific Inc).

After vital signs were recorded, the remaining variables evaluated at each time point were assessed in the following order: neck tone and jaw tone, palpebral reflexes, forelimb muscle tone, hind limb muscle tone, forelimb withdrawal, hind limb withdrawal, and response to a tail pinch. Spontaneous movement was defined as any purposeful and coordinated movement. Skeletal muscle tone in the neck, jaw, forelimbs, and hind limbs was evaluated by assessing resistance to manual manipulation (gentle head, jaw, and limb retraction). Palpebral reflexes were tested with a small cotton-tipped applicator gently touching rostral canthus of each eye twice. The forelimb and hind limb withdrawal responses were tested by pinching a digit and the skin bilaterally on each limb; the tail-pinch response was tested in the same manner. A hemostat was used to apply increasing amounts of subjectively determined pressure (each pressure applied 2 times/location) until a response was observed. The responses were subjectively assessed as present or absent.

At each time point, endotracheal intubation with a 2.0- to 3.0-mm uncuffed endotracheal tube (Sheridan; Teleflex Inc) was attempted when spontaneous movement and jaw tone were absent. Intubation was considered successful if the tube was placed uneventfully or only a minor response was elicited. Intubation was considered unsuccessful when attempted tube placement evoked a jaw contraction or gag reflex or if the animal moved spontaneously.

Every 15 minutes after DMK injection up to the time of drug reversal, each tortoise was evaluated for responsiveness to IM injection of 0.1 mL of sterile saline (0.9% NaCl) solution. The injection was administered in the left pelvic limb (femorotibialis muscle).

Reversal agents—Atipamezole (Antisedan; 0.5 mg/kg, IM) and flumazenil (0.05 mg/kg, SC) were administered in the left antebrachium 60 minutes after DMK injection. Tortoises were monitored as described until recovery from anesthesia or sedation and were later monitored closely by their keepers for any signs of resedation or other adverse effects.

Statistical analysis

Changes in heart rate, respiratory rate, and cloacal temperature were assessed over time (from the time of DMK administration [time 0 for this analysis] until the time of reversal agent administration) by use of linear mixed models, with time, sex, age, and weight as fixed effects and animal as the random effect. Residual plots were used to assess linearity, homogeneity of variances, normality, and outliers. Quantile plots were also used to assess the residuals for normality. Post hoc analysis was performed with a Tukey adjustment. All analyses were performed with a statistical program (R package version 3.1-121; R Foundation for Statistical Computing). Values of P < 0.05 were considered significant.

Results

The ages of tortoises in the study ranged from 11 to 52 years. The median body weight was 4.65 kg (range, 3.0 to 9.2 kg). There was no significant effect of sex, age, or weight on any of the measured variables. The median time to first response after DMK administration was 4.5 minutes (range, 2 to 18 minutes; IQR, 3 to 8.25 minutes), and median time to maximum drug effect was 35 minutes (range, 25 to 45 minutes; IQR, 28.75 to 35 minutes). The median time to recovery after reversal agent injection was 14.5 minutes (range, 2 to 44 minutes; IQR, 9.5 to 34.75 minutes). Both induction and recovery were deemed fast and smooth (ie, no struggling, hyperactivity, signs of disorientation, or other anomalies were observed).

No animals had adverse effects detected during or after the procedure. Two tortoises had delayed recoveries (based on the authors’ experience with other animals in the study) and were administered a second dose of reversal agents 20 minutes after the first, and both recovered within approximately 20 minutes after a second dose was administered.

The mean heart rate decreased significantly (P < 0.001) over time after DMK injection, with a mean ± SEM change of –0.14 ± 0.02 beats for each 1-minute increment of time (Figure 1). The maximum decrease in heart rate, compared with the time 0 value, was 60.2% minutes after DMK administration. The mean respiratory rate also decreased significantly (P < 0.001) over time (Figure 2). However, because the values at time 0 had a much higher order of magnitude than those at all subsequent time points, the model did not fit the statistical assumptions. When the time 0 values were removed from the analysis, respiratory rate was still significantly (P = 0.014) decreased over time, but the effect was clinically negligible (mean ± SEM change, –0.02 ± 0.008 breaths for each 1-minute increment), and no differences between individual time points were found on post hoc analysis (Figure 3). The maximum decrease in respiratory rate, compared with the time 0 value, was 99.5% 40 minutes after DMK administration. There was a slight increase in mean cloacal temperature during the procedure, with the greatest change from the time 0 value (6.8%) at 60 minutes after DMK injection (Figure 4). However, the change over time was nonsignificant.

Figure 1
Figure 1

Mean ± SEM heart rate for 12 red-footed tortoises (Chelonoidis carbonaria) following dexmedetomidine-midazolam-ketamine (DMK) injection. Time 0 represents the time when DMK injection was completed. Heart rate decreased significantly (P < 0.001) over time.

Citation: American Journal of Veterinary Research 82, 11; 10.2460/ajvr.82.11.858

Figure 2
Figure 2

Mean ± SEM respiratory rate for the tortoises in Figure 1 following DMK injection. Respiratory rate decreased significantly (P < 0.001) over time.

Citation: American Journal of Veterinary Research 82, 11; 10.2460/ajvr.82.11.858

Figure 3
Figure 3

Mean ± SEM respiratory rate for the tortoises in Figure 1 from 5 to 60 minutes after DMK injection. After removing the time 0 measurement from the analysis, respiratory rate was still significantly (P = 0.014) decreased over time.

Citation: American Journal of Veterinary Research 82, 11; 10.2460/ajvr.82.11.858

Figure 4
Figure 4

Mean ± SEM cloacal temperature for the tortoises in Figure 1 following dexmedetomidine-midazolam-ketamine injection. Although there was a slight increase over time, the change was nonsignificant.

Citation: American Journal of Veterinary Research 82, 11; 10.2460/ajvr.82.11.858

The numbers of tortoises in which muscle tone and tested reflexes or responses were absent at various time points are summarized (Table 1). All tortoises had complete muscle relaxation of the neck and limbs from 35 to 55 minutes after DMK injection; however, the results for all other tested variables were mixed and inconsistent.

Table 1

Numbers of red-footed tortoises (Chelonoidis carbonaria) in which muscle tone and reflexes or responses were absent* at predetermined time points in a study to determine the physiologic effects and anesthetic properties of DMK (0.1, 1.0, and 10 mg/kg, respectively) after IM administration in this species.

Time (min) Muscle tone Reflex or response
Jaw Neck Fore-limb Hind limb Palpebral reflex Forelimb withdrawal Hind limb withdrawal Tail pinch Saline solution injection Intubation
After DMK injection
5 2 3 4 7 0 2 2 1 0
10 2 6 6 9 0 4 2 1 1
15 6 10 7 10 0 6 4 1 6 2
20 7 10 10 11 2 7 5 3 2
25 10 11 11 12 2 8 5 4 2
30 9 11 11 12 3 9 7 4 7 3
35 9 12 12 12 4 9 7 4 5
40 9 12 12 12 4 9 8 4 5
45 9 12 12 12 4 9 6 4 9 5
50 9 12 12 12 4 9 6 4 5
55 9 12 12 12 4 10 6 4 6
60 6 9 9 9 4 7 5 4 7 3
After reversal agent injection
5 2 7 8 8 4 6 3 1
10 2 8 6 7 3 2 2 1
15 1 7 4 7 2 1 2 1
20 0 4 3 2 0 1 0 1
25 0 2 1 2 0 1 0 1

Twelve healthy adult tortoises received the dexmedetomidine-midazolam-ketamine injection; reversal agents (atipamezole [0.5 mg/kg, IM] and flumazenil [0.05 mg/kg, SC]) were administered 60 minutes later. Variables were assessed at 5-minute intervals after each treatment, except for response to a saline (0.9% NaCl) solution injection (0.1 mL, IM), which was assessed at 15-minute intervals.

The number of tortoises reported for intubation reflects the number for which the endotracheal tube was successfully placed at the time point shown (ie, a response was absent or there was a mild response that allowed uneventful intubation).

— = Not applicable (not attempted).

Discussion

In the study reported here, healthy adult red-footed tortoises were immobilized with a DMK combination administered IM in a forelimb. This DMK protocol resulted in a rapid onset of deep sedation or light anesthesia that lasted for ≥ 20 minutes in 12 of 12 tortoises and for approximately 40 minutes, long enough to perform minor clinical procedures, in more than half of the study sample. This was followed by a smooth, uneventful recovery after administration of reversal agents, and no adverse effects were detected during or after the study.

Fifty-five minutes after DMK injection, 12 of 12 tortoises had complete muscle relaxation of the neck and limbs, and 6 of 12 could be intubated at that time. The lack of glottal control and ability to intubate some of these animals suggested that this DMK protocol can also be used as a premedication or induction protocol for gas anesthesia or for some test procedures such as bronchoalveolar lavage. The ability to intubate can also be important for patient support, given the low respiratory rates observed in the tortoises in this study. Respiratory depression is considered to be a common effect of α2-adrenoceptor agonists in reptiles.24 This lower respiratory rate was consistent with findings in other studies11,25,26 of chelonians that revealed bradypnea or apnea following administration of medetomidine. For example, a study27 in which medetomidine and ketamine were administered to gopher tortoises (Gopherus polyphemus) resulted in moderate hypercapnia, hypoxemia, and respiratory acidemia, which resolved following atipamezole administration. In ball pythons (Python regius), doxapram ameliorated the respiratory depressive effects of dexmedetomidine while preserving its antinociceptive effects.24 Thus, the addition of doxapram should be evaluated in future studies of red-footed tortoises undergoing this protocol.

The tortoises in the study reported here had a slight but nonsignificant increase in cloacal temperature after DMK administration, and this value continued to increase after reversal agent administration (data not shown). This finding contrasted with expectations, as anesthesia is generally associated with hypothermia due to vasodilation followed by a reduced response to lower temperature in the hypothalamus; the combination of these 2 physiologic changes allows cooler blood to be redistributed throughout the body.28 No significant effects on body temperature were observed in gopher tortoises anesthetized with medetomidine and ketamine.27 One common cause of hypothermia in anesthetized patients is the inhalation of cold gases, which might have been minimized by bradypnea in tortoises of the study reported here; the lack of hypothermia could have also been secondary to ketamine administration, as it causes increased peripheral arteriolar resistance that may prevent the redistribution of cooler blood.29 The ability of tortoises to remain normothermic appeared to be a possible advantage of this DMK protocol when used for the short interval assessed in the present study.

To assess the depth of sedation or anesthesia in tortoises of our study, several variables other than muscle relaxation were evaluated. These included palpebral reflexes; responses to a tail pinch, toe pinch in all 4 limbs, and saline solution injections; and ability to intubate. The responses to most of these tests were variable and inconsistent, even when all tortoises had complete muscle relaxation in the neck, forelimbs, and hind limbs and most had complete jaw relaxation. For example, the palpebral reflex was intact when responses to noxious stimuli (toe pinch, tail pinch, and saline solution injection) were absent in some of these animals. This was similar to observations reported for red-eared sliders anesthetized with alfaxalone30 or a combination of medetomidine and ketamine.31 The tail-pinch response remained intact or reduced for 8 of 12 animals throughout the immobilization event in the present study. The tail pinch response is not often tested in chelonian anesthesia studies. Instead, limb withdrawal responses are often evaluated. In a study32 that investigated combinations of ketamine, midazolam, and xylazine in red-eared sliders, the absence of a toe-pinch response and lack of neck withdrawal upon manual extension were considered indicative of anesthesia. Some of the animals in that study32 began to purposely move while they had apparently absent withdrawal responses, a finding that was attributed to the dissociative properties of ketamine. The observations in the present study suggested that the toe-pinch withdrawal responses and response to saline solution injection might be unreliable for assessment of nociception in these tortoises, either because the responses are inherently inconsistent in this species or because it is difficult to pinch through the thick skin on the limbs sufficiently to induce nociception without causing trauma to deeper structures. Considering that the tail pinch response was the only one to remain present throughout the procedure in most tortoises of our study, this may be a more sensitive indicator of peripheral nociception than either the toe-pinch or saline injection responses. This might have occurred because red-footed tortoises have thinner skin on the tail than on the limbs. Future studies may also determine the antinociceptive effects of DMK in this species by use of a thermal noxious stimulus, as described for dexmedetomidine and midazolam in other reptiles.33

The variable preservation of commonly tested reflexes and responses in the present study suggested that the described DMK protocol can produce deep sedation or light anesthesia, but not a consistent surgical plane of anesthesia,20,34 in red-footed tortoises. However, this degree of immobilization might allow veterinarians to perform several clinical procedures such as blood sample collection, imaging, oral swabbing, and some minimally invasive endoscopic examinations.12,13,22,23,35,36,37,38 The authors of previous reports on anesthesia of red-footed tortoises used much higher doses of the drugs used in the present DMK protocol. For example, ketamine (40 mg/kg, IM) and midazolam (2.0 mg/kg, IM) facilitated ultrasonographic examination,5 and much lower drug doses may be needed with this DMK protocol. In another prospective study,18 red-footed tortoises underwent 3 different treatments, including ketamine (30 mg/kg), ketamine (30 mg/kg) plus midazolam (1 mg/kg), or ketamine (30 mg/kg) plus butorphanol (1 mg/kg), and each treatment failed to produce a surgical plane of anesthesia. It is possible that tortoises of this species can tolerate much higher dosages of DMK than we evaluated to increase the degree of sedation or anesthesia; however, further studies are needed to assess the efficacy and safety of DMK with various doses of the components.

Other than the lack of reliability of the tested reflexes and responses to gauge the tortoises’ anesthetic depth, limitations of the present study included a lack of blood pressure monitoring and assessment of the cardiorespiratory effects of the DMK protocol. Blood gas analysis and capnography or closed-chamber plethysmography can be used in future studies to determine whether the lower respiratory rates are considered physiologically appropriate with this protocol.24 Also, these tortoises were tested at a room temperature of approximately 25 °C during the month of September, and the observed responses could have been different under different ambient temperatures39 or at different times of the year.40

The DMK protocol described in this report produced deep sedation or light anesthesia in this sample of healthy red-footed tortoises for ≥ 20 minutes, with no response to mild noxious stimuli and successful intubation in some of the tested animals. No apparent adverse effects were noted during the procedure and recovery or on follow-up assessments by the tortoises’ keepers. Considering the inconsistencies in preservation of several tested responses, including deep pain responses throughout the testing period, this DMK protocol alone is not recommended for surgical procedures.

Acknowledgments

Supported by an internal research grant of the Department of Clinical Sciences, College of Veterinary Medicine, Kansas State University.

The authors declare there were no conflicts of interest.

The authors thank Dr. Trent Shrader, Dr. Heather Arens, Dr. Sandra Wilson, Dr. Danelle Okeson, Kirk Nemechek, Lisa Keith, Elizabeth Brannan, Amber Melton, Alexis Sutter, Danielle Russell, Daria Hagan, Tori Matta, Kallie Woodruff, and Carolyn Mark for their assistance with this research.

References

  • 1.

    Barros MS, Resende LC, Silva AG, Ferreira PD Jr. Morpho- logical variations and sexual dimorphism in Chelonoidis carbonaria (Spix, 1824) and Chelonoidis denticulata (Linnaeus, 1766) (Testudinidae). Braz J Biol. 2012;72(1):153161.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 2.

    Turtle Taxonomy Working Group. Turtles of the world: annotated checklist and atlas of taxonomy, synonymy, distribution, and conservation status. 8th ed. Chelonian Research Foundation and Turtle Conservancy. Accessed Dec 25, 2019. images.turtleconservancy.org/documents/2017/crm-7-checklist-atlas-v8-2017.pdf

    • Search Google Scholar
    • Export Citation
  • 3.

    Mueller-Paul J, Wilkinson A, Hall G, Huber L. Radial-arm-maze behavior of the red-footed tortoise (Geochelone carbonaria). J Comp Psychol. 2012;126(3):305317.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 4.

    Wilkinson A, Mueller-Paul J, Huber L. Picture–object recognition in the tortoise Chelonoidis carbonaria. Anim Cogn. 2013;16(1):99107.

  • 5.

    Meireles YS, Shinike FS, Matte DR, et al. Ultrasound characterization of the coelomic cavity organs of the red-footed tortoise (Chelonoidis carbonaria). Ciênc Rural. 2016;46(10):18111817.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 6.

    Santacà M, Miletto Petrazzini ME, Wilkinson A, Agrillo C, et al. Red-footed tortoises (Chelonoidis carbonaria) do not perceive the Delboeuf illusion. Can J Exp Psychol. 2020;74(3):201206.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 7.

    Read MR. Evaluation of the use of anesthesia and analgesia in reptiles. J Am Vet Med Assoc. 2004;224(4):547552.

  • 8.

    Sladky KK, Mans C. Clinical anesthesia in reptiles. J Exot Pet Med. 2012;21(1):1731.

  • 9.

    Knotek Z. Alfaxalone as an induction agent for anaesthesia in terrapins and tortoises. Vet Rec. 2014;175(13):327329.

  • 10.

    Lock BA, Heard DJ, Dennis P. Preliminary evaluation of medetomidine/ketamine combinations for immobilization and reversal with atipamezole in three tortoise species. Bull Assoc Rept Amphib Vet. 1998;8(4):69.

    • Search Google Scholar
    • Export Citation
  • 11.

    Sleeman JM, Gaynor J. Sedative and cardiopulmonary effects of medetomidine and reversal with atipamezole in desert tortoises (Gopherus agassizii). J Zoo Wildl Med. 2000; 31(1):2835.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 12.

    Divers SJ. Endoscopic sex identification in chelonians and birds (psittacines, passerines, and raptors). Vet Clin North Am Exot Anim Pract. 2015;18(3):541554.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 13.

    Emmel ES, Rivera S, Cabrera F, Blake S, Deem SL. Field anesthesia and gonadal morphology of immature Western Santa Cruz tortoises (Chelonoidis porteri). J Zoo Wildl Med. 2021;51(4):848855.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 14.

    Polanco JB, Mamprim MJ, Silva JP, et al. Computed tomographic and radiologic anatomy of the lower respiratory tract in the red-foot tortoise (Chelonoidis carbonaria). Pesqui Vet Bras. 2020;40(8):637646.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 15.

    Campos R, Justo AF, Jacintho FF, et al. Pharmacological and transcriptomic characterization of the nitric oxide pathway in aortic rings isolated from the tortoise Chelonoidis carbonaria. Comp Biochem Physiol C Toxicol Pharmacol. 2019;222:8289.

    • Search Google Scholar
    • Export Citation
  • 16.

    Sousa RP, Nogueira LF, Pessoa GT, Feitosa ML, Carvalho MA, Moura WL. Morphological analysis of peripheral blood cells of Chelonoidis carbonaria (Spix, 1824). Biosci J. 2015;31(1):242247.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 17.

    De Santi M, Cruz N, Barranco G, Lima G. Cutaneous melanoma in a Red-footed tortoise (Chelonoidis carbonaria). J Exot Pet Med. 2020;34:4447.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 18.

    Monteiro ER, da Silva EL, Santos MG, Rossi JL Jr, Ferreira PD Jr. Pharmacological restraint of red-footed tortoises using combinations of ketamine, midazolam and butorphanol. Rev Academica Cienc Anim. 2011;9(3):295298.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 19.

    Arnett-Chinn ER, Hadfield CA, Clayton LA. Review of intramuscular midazolam for sedation in reptiles at the National Aquarium, Baltimore. J Herpetologic Med Surg. 2016;26(1–2):5963.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 20.

    Mans C, Sladky KK, Schumacher J. General anesthesia. In: Divers SJ, Stahl SJ, eds. Mader’s Reptile and Amphibian Medicine and Surgery. 3rd ed. WB Saunders; 2019:447464.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 21.

    Emery L, Parsons G, Gerhardt L, Schumacher J. Sedative effects of intranasal midazolam and dexmedetomidine in 2 species of tortoises (Chelonoidis carbonaria and Geochelone platynota). J Exot Pet Med. 2014;23(4):380383.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 22.

    Mans C, Foster JD. Endoscopy-guided ectopic egg removal from the urinary bladder in a leopard tortoise (Stigmochelys pardalis). Can Vet J. 2014;55(6):569572.

    • Search Google Scholar
    • Export Citation
  • 23.

    Mans C, Sladky KK. Endoscopically guided removal of cloacal calculi in three African spurred tortoises (Geochelone sulcata). J Am Vet Med Assoc. 2012;240(7):869875.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 24.

    Karklus AA, Sladky KK, Johnson SM. Respiratory and antinociceptive effects of dexmedetomidine and doxapram in ball pythons (Python regius). Am J Vet Res. 2021;82(1):1121.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 25.

    Hansen LL, Bertelsen MF. Assessment of the effects of intramuscular administration of alfaxalone with and without medetomidine in Horsfield’s tortoises (Agrionemys horsfieldii). Vet Anaesth Analg. 2013;40(6):e68e75.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 26.

    Morici M, Interlandi C, Costa GL, Di Giuseppe M, Spadola F. Sedation with intracloacal administration of dexmedetomidine and ketamine in yellow-bellied sliders (Trachemys scripta scripta). J Exot Pet Med. 2017;26(3):188191.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 27.

    Dennis PM, Heard DJ. Cardiopulmonary effects of a medetomidine-ketamine combination administered intravenously in gopher tortoises. J Am Vet Med Med. 2002;220(10):15161519.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 28.

    Díaz M, Becker DE. Thermoregulation: physiological and clinical considerations during sedation and general anesthesia. Anesth Prog. 2010;57(1):2533.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 29.

    Ikeda T, Kazama T, Sessler DI, et al. Induction of anesthesia with ketamine reduces the magnitude of redistribution hypothermia. Anesth Analg. 2001;93:934938.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 30.

    Kischinovsky M, Duse A, Wang T, Bertelsen MF. Intramuscular administration of alfaxalone in red-eared sliders (Trachemys scripta elegans)–effects of dose and body temperature. Vet Anaesth Analg. 2012;40(1):1320.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 31.

    Greer LL, Jenne KJ, Diggs HE. Medetomidine-ketamine anesthesia in red-eared slider turtles (Trachemys scripta elegans). Contemp Top Lab Anim Sci. 2001;40(3):911.

    • Search Google Scholar
    • Export Citation
  • 32.

    Holz P, Holz RM. Evaluation of ketamine, ketamine/xylazine, and ketamine/midazolam anesthesia in red-eared sliders (Trachemys scripta elegans). J Zoo Wildl Med. 1994;25(4):531537.

    • Search Google Scholar
    • Export Citation
  • 33.

    Bisetto SP, Melo CF, Carregaro AB. Evaluation of sedative and antinociceptive effects of dexmedetomidine, midazolam and dexmedetomidine–midazolam in tegus (Salvator merianae). Vet Anaesth Analg. 2018;45(3):320328.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 34.

    Bennett RA. Reptile anesthesia. Semin Avian Exotic Pet med 1998;7(1):3040.

  • 35.

    Hernandez-Divers SJ, Stahl SJ, Farrell R. An endoscopic method for identifying sex of hatchling Chinese box turtles and comparison of general versus local anesthesia for coelioscopy. J Am Vet Med Assoc. 2009;234(6):800804.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 36.

    Kuchling G. Endoscopic sex determination in juvenile freshwater turtles, Erymnochelys madagascariensis: morphology of gonads and accessory ducts endoscopic sex determination in juvenile freshwater turtles. Chelonian Conserv Biol. 2006;5(1):6773.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 37.

    Kuchling G, Goode E, Praschag P. Endoscopic imaging of gonads, sex ratio and temperature dependent sex determination in captive bred juvenile Burmese star tortoises Geochelone platynota. Asian Herpetol Res. 2011;2(4):240244.

    • Search Google Scholar
    • Export Citation
  • 38.

    Kuchling G, Goode EV, Praschag P. Endoscopic imaging of gonads, sex ratio, and temperature-dependent sex determination in juvenile captive-bred radiated tortoises, Astrochelys radiata. Chelonian Res Monogr. 2013;6:113118.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 39.

    Shepard MK, Divers S, Braun C, Hofmeister EH. Pharmacodynamics of alfaxalone after single-dose intramuscular administration in red-eared sliders (Trachemys scripta elegans): a comparison of two different doses at two different ambient temperatures. Vet Anaesth Analg. 2013;40(6):590598.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 40.

    McGuire JL, Hernandez SM, Smith LL, Yabsley MJ. Safety and utility of an anesthetic protocol for the collection of biological samples from gopher tortoises. Wildl Soc Bull. 2014;38(1):4350.

    • Crossref
    • Search Google Scholar
    • Export Citation

Contributor Notes

Address correspondence to Dr. Eshar (deshar@vet.k-state.edu).