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

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.

Comparison of Subcutaneous versus Intramuscular Dexmedetomidine–Midazolam–Ketamine–Morphine (DMKM) Mixture as Chemical Restraint for Endoscopic Sex Determination in Aldabra Giant Tortoises (Aldabrachelys gigantea)

“…Additionally, among the animals successfully induced with IM DMKM, one tortoise did not lose the neck retraction reflex, and another did not lose the palpebral reflex, indicating a lighter plane of anaesthesia. HR and RR decreased significantly over time in both groups before the start of the celioscopic procedure, as also reported in the study by Eshar et al [35] using IM DMK administration in captive red-footed tortoises (Chelodinis carbonaria). In dogs and cats, the pharmacokinetics of anaesthetic drugs are influenced by the route of administration [35].…”

“…HR and RR decreased significantly over time in both groups before the start of the celioscopic procedure, as also reported in the study by Eshar et al [35] using IM DMK administration in captive red-footed tortoises (Chelodinis carbonaria). In dogs and cats, the pharmacokinetics of anaesthetic drugs are influenced by the route of administration [35]. Specifically, the subcutaneous route does not always allow for complete and rapid uptake of the drug mixture.…”

“…Both opioids and a2-adrenoceptor agonists can induce respiratory depression in reptiles [10,12,[45][46][47]. The occurrence of apnoea after the administration of medetomidine and dexmedetomidine is reported in chelonians [13,35,46]. In this study, 12/14 tortoises belonging to the IM and SC groups (8 IM, 4 SC) had apnoea and needed intubation and manual ventilation.…”

“…This was supposedly related to the poor distensible skin and the well-developed antebrachial muscles, which are typical features of large terrestrial chelonians [34], in relation to the volume of the injected drug mixture. In a recent study evaluating the effect of the IM dexmedetomidine-midazolam-ketamine (DMK) combination in red-footed tortoises, the median time to maximum drug effect was reached in approximately 35 min [35]. In the literature, as there are no available studies about the effects of DMKM in Aldabra giant tortoises, a limit of 45 min was chosen as a cut-off for the time to loss of reflexes, and in the case of persistent thoracic and pelvic limb withdrawal reflexes, the animal would be induced with IV propofol.…”

“…In fact, a DMK combination provided sufficient sedation or light anaesthesia, allowing the execution of various clinical procedures, including minimally invasive endoscopic examinations, blood sample collection, and imaging [18,24,27,43,44]. The authors of prior studies focusing on the anaesthesia of red-footed tortoises used higher doses of dexmedetomidine-midazolam and ketamine than those used in the present DMKM protocol [35,44] and did not include morphine in the drug mixture. In this case, morphine was chosen as an additional pain relief agent, as this has been demonstrated to be effective in several reptilian species [18].…”