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Objective: To investigate the cardiovascular and sedation reversal effects of IM administration of atipamezole (AA) in dogs treated with medetomidine hydrochloride (MED) or MED and vatinoxan (MK-467)., Animals: 8 purpose-bred, 2-year-old Beagles., Procedures: A randomized, blinded, crossover study was performed in which each dog received 2 IM treatments at a ≥ 2-week interval as follows: injection of MED (20 μg/kg) or MED mixed with 400 μg of vatinoxan/kg (MEDVAT) 30 minutes before AA (100 μg/kg). Sedation score, heart rate, mean arterial and central venous blood pressures, and cardiac output were recorded before and at various time points (up to 90 minutes) after AA. Cardiac and systemic vascular resistance indices were calculated. Venous blood samples were collected at intervals until 210 minutes after AA for drug concentration analysis., Results: Heart rate following MED administration was lower, compared with findings after MEDVAT administration, prior to and at ≥ 10 minutes after AA. Mean arterial blood pressure was lower with MEDVAT than with MED at 5 minutes after AA, when its nadir was detected. Overall, cardiac index was higher and systemic vascular resistance index lower, indicating better cardiovascular function, in MEDVAT-atipamezole-treated dogs. Plasma dexmedetomidine concentrations were lower and recoveries from sedation were faster and more complete after MEDVAT treatment with AA than after MED treatment with AA., Conclusions and Clinical Relevance: Atipamezole failed to restore heart rate and cardiac index in medetomidine-sedated dogs, and relapses into sedation were observed. Coadministration of vatinoxan with MED helped to maintain hemodynamic function and hastened the recovery from sedation after AA in dogs.

Eight adult tigers ( Panthera tigris) underwent a complete echocardiographic examination following sedation with medetomidine, midazolam, and induction of general anesthesia using ketamine and isoflurane (phase 1). Atipamezole was used to antagonize medetomidine (phase 2) and a second echocardiographic examination was performed. Physiologic tricuspid and pulmonic regurgitations were common findings in the sample population and one tiger was excluded from final analyses due to the finding of a ventricular septal defect. Measurements and mean arterial pressure were assessed for statistically significant differences between the two examination phases as well as gender and weight. There was a statistically significant difference between interventricular septum thickness at end systole, ejection fraction, and mean arterial pressure between anesthetic phases while fractional shortening and left ventricular internal dimension at end-systole approached, but did not reach, statistical significance between phases. Weight was found to be a statistically significant predictor of stroke volume and left ventricular internal dimension at end-diastole. The echocardiographic measurements obtained during this study can be used as guidelines for future examinations in adult tigers. The effects of medetomidine on these measurements and systolic function should be taken into account when performing echocardiograms and monitoring anesthetic events.

Objective: To evaluate the effect of the peripherally acting α 2 -adrenoceptor antagonist vatinoxan (MK-467) on the sedative properties of medetomidine (MED) when injected intramuscularly (IM) in the same syringe and on reversal of this sedation with atipamezole in sheep., Study Design: Randomized, blinded, crossover experimental trial., Animals: Eight healthy adult female sheep., Methods: Sheep received MED (30 μg kg -1 IM) alone or combined in the same syringe with vatinoxan (300 μg kg -1 IM, MED+VAT) with a 2 week washout period. Atipamezole (150 μg kg -1 IM) was administered 30 minutes later for reversal. Sedation was assessed using two sedation scores, a visual analog score and a descriptive scale before treatments (T0) and at intervals up to 5 hours thereafter. Pulse rate (PR) was counted at T0 and at 30 (T30) and 90 (T90) minutes. Rectal temperature was measured at T0 and T90 postinjection. Plasma samples were analyzed for drug concentrations at T30 and T90., Results: The first signs of sedation were seen significantly earlier after MED+VAT (4.6 ± 1.7 minutes versus 9.4 ± 2.6 minutes after MED) and the sedation scores were significantly higher after MED+VAT than MED. All animals laid with head down 10.0 ± 3.4 minutes after MED+VAT, whereas three MED animals did not become recumbent before atipamezole was administered. The plasma concentrations of dexmedetomidine were significantly higher at T30 (2.47 ± 0.2 ng mL -1 ) and significantly lower at T90 (1.23 ± 0.3 ng mL -1 ) with MED+VAT than with MED (1.19 ± 0.8 and 1.83 ± 0.4 ng mL -1 , respectively). While no significant differences were observed between treatments in PR at T30, PR at T90 was significantly higher with MED+VAT than with MED., Conclusions and Clinical Relevance: When administered IM in the same syringe, vatinoxan hastened and intensified the initial sedative effects of MED and enhanced the sedation reversal by atipamezole., (Copyright © 2018 Association of Veterinary Anaesthetists and American College of Veterinary Anesthesia and Analgesia. Published by Elsevier Ltd. All rights reserved.)

Objective: To characterize a propofol-medetomidine-ketamine total intravenous anaesthetic in impala (Aepyceros melampus)., Study Design: Prospective clinical study., Animals: Ten adult female impala., Materials and Methods: Impala were immobilized at 1253 m above sea level with 2.0 mg thiafentanil and 2.2 mg medetomidine via projectile darts. Propofol was given to effect (0.5 mg kg -1 boluses) to allow endotracheal intubation, following which oxygen was supplemented at 2 L minute -1 . Anaesthesia was maintained with a constant-rate infusion of medetomidine and ketamine at 5 μg kg -1 hour -1 and 1.5 mg kg -1 hour -1 , respectively, and propofol to effect (initially 0.2 mg kg -1 minute -1 ) for 120 minutes. The propofol infusion was titrated according to reaction to nociceptive stimuli every 15 minutes. Cardiopulmonary parameters were monitored continuously and arterial blood gas samples were analysed intermittently. After 120 minutes' maintenance, the thiafentanil and medetomidine were antagonized using naltrexone (10:1 thiafentanil) and atipamezole (5:1 medetomidine), respectively., Results: All impala were successfully immobilized. The median dose [interquartile range (IQR)] of propofol required for intubation was 2.7 (1.9-3.3) mg kg -1 . The propofol-medetomidine-ketamine combination abolished voluntary movement and ensured anaesthesia for the 120 minute period. Propofol titration showed a generally downward trend. Median (IQR) heart rate [57 (53-61) beats minute -1 ], respiratory rate [10 (9-12) breaths minute -1 ] and mean arterial blood pressure [101 (98-106) mmHg] were well maintained. Arterial blood gas analysis indicated hypoxaemia, hyper- capnia and acidaemia. Butorphanol (0.12 mg kg -1 ) was an essential rescue drug to counteract thiafentanil-induced respiratory depression. All impala regurgitated frequently during the maintenance period. Recovery was calm and rapid in all animals. Median (IQR) time to standing from antagonist administration was 4.4 (3.2-5.6) minutes., Conclusions and Clinical Relevance: A propofol-medetomidine-ketamine combination could provide adequate anaesthesia for invasive procedures in impala. The propofol infusion should begin at 0.2 mg kg -1 minute -1 and be titrated to clinical effect. Oxygen supplementation and airway protection with a cuffed endotracheal tube are essential., (Copyright © 2016 Association of Veterinary Anaesthetists and American College of Veterinary Anesthesia and Analgesia. Published by Elsevier Ltd. All rights reserved.)

We investigated the influence of the peripherally acting α2 -adrenoceptor antagonist MK-467 on the sedative and antinociceptive actions and plasma drug concentrations of medetomidine, an α2 -adrenoceptor agonist that is used in veterinary medicine as a sedative and analgesic agent. Eight healthy beagle dogs received intravenous medetomidine (10 μg/kg) or medetomidine with MK-467 (250 μg/kg) in a randomized crossover design. A standardized nociceptive pressure stimulus was applied to a nail bed of a hindlimb. Times for withdrawal of the limb and for head lift were measured, and sedation was scored. EEG data were collected prior to and after stimulation. Plasma drug concentrations were measured. Co-administration of MK-467 significantly attenuated medetomidine analgesia, as assessed with limb withdrawal, and also shortened the duration of sedation. The apparent plasma clearance of both enantiomers of medetomidine, dexmedetomidine and levomedetomidine, was more than doubled in the presence of MK-467. Antagonism by MK-467 of medetomidine-evoked vasoconstriction is seen as the mechanism behind this pharmacokinetic drug interaction. Thus, MK-467 attenuated the antinociceptive and sedative effects of medetomidine. This can probably be explained by increased clearance and decreased concentrations of dexmedetomidine in plasma after co-administration of MK-467 with racemic medetomidine., (© 2016 John Wiley & Sons Ltd.)

Objective: To establish a safe, reliable and reversible immobilization protocol for captive juvenile crocodiles., Study Design: Prospective, randomized, clinical study., Animals: Thirty male estuarine crocodiles (body mass 1-12.1 kg) and 10 male Australian freshwater crocodiles (body mass 4.1-12.8 kg)., Methods: An optimized dose of medetomidine (0.5 mg kg(-1)) was administered intramuscularly (IM) into the tail (Group 1; n = 5), pelvic limb (Group 2; n = 5) and thoracic limb (Groups 3 and 4; n = 5 in each group) of estuarine crocodiles weighing 3-12.1 kg. Their heart and respiratory rates and degree of immobilization were monitored every 15 minutes until recovery and daily thereafter for 3 subsequent days. In Group 4 (n = 5), medetomidine was antagonized with an optimized dose of atipamezole (2.5 mg kg(-1)) given IM into the thoracic limb and time to recovery recorded. The effects of increasing doses of medetomidine given IM in the thoracic limb (n = 4) and intravenously (n = 6) were determined in 1-2 kg estuarine crocodiles. Australian freshwater crocodiles (4.1-12.8 kg) were administered medetomidine IM into the thoracic limb in divided doses at 0.5 mg kg(-1) (n = 5) and 0.75 mg kg(-1) (n = 5) and similarly monitored., Results: Immobilization was achieved only in the estuarine crocodiles >3 kg and when medetomidine was administered into the thoracic limb. Immobilization was achieved within 30 minutes and the duration of immobilization lasted approximately 90 minutes. Immobilization in estuarine crocodiles was readily reversed with atipamezole. A dose of 0.75 g kg(-1) was required to immobilize Australian freshwater crocodiles and the onset of immobilization was longer and the duration shorter than seen in the estuarine crocodiles. The heart and respiratory rates of all immobilized animals decreased significantly and arterial blood pressure became undetectable in the animals in which it was measured., Conclusions and Clinical Relevance: Medetomidine administered in the thoracic limb of captive estuarine and Australian freshwater crocodiles, ranging from 3 to 12.8 kg, provides a predictable onset and duration of immobilization sufficient for physical examination, sample collection, short minor procedures and translocation of the animals. Atipamezole administered in the thoracic limb results in complete reversal of the effects of medetomidine in the estuarine crocodile and a rapid return to normal behaviour., (© 2012 The Authors. Veterinary Anaesthesia and Analgesia. © 2012 Association of Veterinary Anaesthetists and the American College of Veterinary Anesthesiologists.)

The Judas technique is a method used for landscape control of feral donkeys (Equus asinus) in northern Australia. Central to the success of any Judas program is the safe, efficient, and humane attachment of the telemetry device. For feral donkeys, this involves the use of field immobilization. We examine the replacement of the current chemical capture agent, succinylcholine, with contemporary immobilization agents to achieve positive animal welfare outcomes. A combination of medetomidine and ketamine delivered by remote injection from a helicopter was used to capture 14 free-ranging feral donkeys for the fitting of telemetry collars in Western Australia in November 2010. Dose rates of 0.14 mg/kg medetomidine and 4.1 mg/kg ketamine were appropriate to immobilize animals in 9 min (± SD = 3). Mean recovery time (total time in recumbency) was 21 min (± 14). All animals recovered uneventfully after being administered atipamezole, a specific antagonist of medetomidine, intramuscularly at 0.35 mg/kg. Physiologic parameters were recorded during recumbency, with environment-related hyperthermia being the only abnormality recognized. No significant complications were encountered, and this drug combination represents an efficient approach to capturing wild donkeys. This new method allows a rapid, safe, cost-effective approach to the immobilization of feral donkeys for use as Judas animals. This drug combination will replace the relatively inhumane succinylcholine for the field immobilization of feral donkeys.

Twenty adult, free-ranging, female Svalbard reindeer (Rangifer tarandus platyrhynchus) were immobilized with medetomidine-ketamine from 30 September through 9 October 1999 at Svalbard, Norway (78 degrees 55'N, 11 degrees 56'E). The animals were approached on foot, and the drugs were administered into the heavy muscles of the shoulder or the thigh by dart syringe injection from 15-25 m. The mean (SD) induction time in 10 animals immobilized with 0.113 (0.009) mg/kg of medetomidine and 2.26 (0.19) mg/kg of ketamine (group 2) was significantly shorter (P < 0.05) than in 10 animals immobilized with 0.215 (0.043) mg/kg of medetomidine and 1.08 (0.21) mg/kg of ketamine (group 1): 6.5 (3.2) versus 14.3 (10.6) min, respectively. Inductions were calm, major clinical side effects were not detected, and there were no significant differences between groups regarding rectal temperature, pulse rate, respiratory rate, or relative arterial oxygen saturation. The 5 mg of atipamezole/1 mg of medetomidine were given half intramuscularly and half subcutaneously for reversal, and the animals were standing within 9.5 (4.5, group 1) and 13.0 (6.4, group 2) min, respectively, after administration of the antagonist.

Objective: To assess the sedative and cardiopulmonary effects of medetomidine and xylazine and their reversal with atipamezole in calves., Animals: 25 calves., Procedures: A 2-phase (7-day interval) study was performed. Sedative characteristics (phase I) and cardiopulmonary effects (phase II) of medetomidine hydrochloride and xylazine hydrochloride administration followed by atipamezole hydrochloride administration were evaluated. In both phases, calves were randomly allocated to receive 1 of 4 treatments IV: medetomidine (0.03 mg/kg) followed by atipamezole (0.1 mg/kg; n = 6), xylazine (0.3 mg/kg) followed by atipamezole (0.04 mg/kg; 7), medetomidine (0.03 mg/kg) followed by saline (0.9% NaCl; 6) solution (10 mL), and xylazine (0.3 mg/kg) followed by saline solution (10 mL; 6). Atipamezole or saline solution was administered 20 minutes after the first injection. Cardiopulmonary variables were recorded at intervals for 35 minutes after medetomidine or xylazine administration., Results: At the doses evaluated, xylazine and medetomidine induced a similar degree of sedation in calves; however, the duration of medetomidine-associated sedation was longer. Compared with pretreatment values, heart rate, cardiac index, and PaO(2) decreased, whereas central venous pressure, PaCO(2), and pulmonary artery pressures increased with medetomidine or xylazine. Systemic arterial blood pressures and vascular resistance increased with medetomidine and decreased with xylazine. Atipamezole reversed the sedative and most of the cardiopulmonary effects of both drugs., Conclusions and Clinical Relevance: At these doses, xylazine and medetomidine induced similar degrees of sedation and cardiopulmonary depression in calves, although medetomidine administration resulted in increases in systemic arterial blood pressures. Atipamezole effectively reversed medetomidine- and xylazine-associated sedative and cardiopulmonary effects in calves.

A combination of 0.05 mg/kg medetomidine and 1.5 mg/kg ketamine was used to immobilize nine adult free-ranging hog deer (Axis porcinus) captured in drive nets in the Royal Bardia National Park, Nepal, 22-23 February 2000. The drugs were administered intramuscularly from separate syringes and the mean time (+/-SD) to complete immobilization was 4.6+/-1.0 min. Muscle relaxation was good and no major clinical side effects were seen. Mean values for physiologic parameters, recorded at 10-12 and 18-20 min after drug administration, were 40.6+/-0.5 and 41.1+/-0.6 C, 87+/-5 and 84+/-4%, 107+/-16 and 113+/-16 beats/ min, and 46+/-9 and 40+/-8 breaths/min for rectal temperature, SpO2, pulse rate, and respiratory rate, respectively. All animals received 0.25 mg/ kg atipamezole intramuscularly 20-22 min after administration of medetomidine-ketamine and the mean time to coordinated running was 4.8+/-0.8 min. All animals survived for at least 5 mo post-capture. To reduce stress and to facilitate handling, medetomidine-ketamine and atipamezole are recommended for reversible immobilization of free-ranging hog deer captured in drive nets.

A combination of medetomidine, Telazol, and ketamine hydrochloride was used to immobilize captive Chacoan peccaries (Catagonus wagneri) for translocation within Paraguay during August-October 2002. Animals were darted in enclosed areas of varying size. The average dose used was 32.5+/-7.2 microg/kg of medetomidine, 0.63+/-0.2 mg/kg of Telazol, and 3.9+/-0.65 mg/kg of ketamine. First effects were noted at 4.3+/-2.1 min, and ability to handle the animals was achieved by 12.6+/-3.7 min. Heart and respiratory rates declined and oxygen saturation increased during anesthesia. Muscle relaxation was good. Atipamezole was used to antagonize the medetomidine, although recoveries were still slow. This drug combination provided adequate immobilization of Chacoan peccaries; however, this protocol would not be considered to be reversible, and confinement during recovery is recommended.

This study aimed to compare the antagonistic effects of atipamezole (40,120, and 320 microg/kg, IM), yohimbine (110 microg/kg, IM), and saline on neurohormonal and metabolic responses induced by medetomidine (20 microg/kg, IM). Five beagle dogs were used in each of the 5 experimental groups in randomized order. Blood samples were taken for 6 h. Medetomidine significantly decreased norepinephrine, epinephrine, insulin, and nonesterified fatty acid levels, and increased plasma glucose levels. Both atipamezole and yohimbine antagonized these effects. The reversal effect of atipamezole was dose-dependency, except on epinephrine. Yohimbine caused prolonged increases in plasma norepinephrine and insulin levels compared to atipamezole, possibly because of its longer half-life elimination. Only yohimbine increased the cortisol levels. Neither glucagon nor lactate levels changed significantly. Based on these findings, when medetomidine-induced sedation is antagonized in dogs, we recommend using atipamezole IM, from 2- to 6-fold the dose of medetomidine, unless otherwise indicated.

The purpose of this study was to evaluate the cardio-respiratory effects of the combination of medetomidine and thiopentone followed by reversal with atipamezole as a combination for anaesthesia in 10 healthy German Shepherd dogs breathing spontaneously in a room at an altitude of 1486 m above sea level with an ambient air pressure of 651 mmHg. After the placement of intravenous and intra-arterial catheters, baseline samples were collected. Medetomidine (0.010 mg/kg) was administered intravenously and blood pressure and heart rate were recorded every minute for 5 minutes. Thiopentone was then slowly administered until intubation conditions were ideal. An endotracheal tube was placed and the dogs breathed room air spontaneously. Blood pressure, pulse oximetry, respiratory and heart rate, capnography, blood gas analysis and arterial lactate were performed or recorded every 10 minutes for the duration of the trial. Thiopentone was administered to maintain anaesthesia. After 60 minutes, atipamezole (0.025 mg/kg) was given intramuscularly. Data were recorded for the next 30 minutes. A dose of 8.7 mg/kg of thiopentone was required to anaesthetise the dogs after the administration of 0.010 mg/kg of medetomidine. Heart rate decreased from 96.7 at baseline to 38.5 5 minutes after the administration of medetomidine (P < 0.05). Heart rate then increased with the administration of thiopentone to 103.2 (P < 0.05). Blood pressure increased from 169.4/86.2 mmHg to 253.2/143.0 mmHg 5 minutes after the administration of medetomidine (P < 0.05). Blood pressure then slowly returned towards normal. Heart rate and blood pressure returned to baseline values after the administration of atipamezole. Arterial oxygen tension decreased from baseline levels (84.1 mmHg) to 57.8 mmHg after the administration of medetomidine and thiopentone (P < 0.05). This was accompanied by arterial desaturation from 94.7 to 79.7% (P < 0.05). A decrease in respiratory rate from 71.8 bpm to 12.2 bpm was seen during the same period. Respiratory rates slowly increased over the next hour to 27.0 bpm and a further increases 51.4 bpm after the administration of atipamezole was seen (P < 0.05). This was maintained until the end of the observation period. Arterial oxygen tension slowly returned towards normal over the observation period. No significant changes in blood lactate were seen. No correlation was found between arterial saturation as determined by blood gas analysis and pulse oximetry. Recovery after the administration of atipamezole was rapid (5.9 minutes). In healthy dogs, anaesthesia can be maintained with a combination of medetomidine and thiopentone, significant anaesthetic sparing effects have been noted and recovery from anaesthesia is not unduly delayed. Hypoxaemia may be problematic. Appropriate monitoring should be done and oxygen supplementation and ventilatory support should be available. A poor correlation between SpO2 and SaO2 and ETCO2 and PaCO2 was found.

Safe, effective, and reversible immobilization protocols are essential for the management of free-ranging red wolves (Canis rufus). Combinations using an alpha2-adrenoceptor agonist and ketamine have been shown to be effective for immobilization but are not reversible and can produce severe hypertension and prolonged or rough recoveries. To minimize hypertension and provide reversibility, 24 red wolves were immobilized using three medetomidine-butorphanol (MB) combinations without the use of ketamine in the initial injection. All wolves were administered medetomidine (0.04 mg/kg i.m.) and butorphanol (0.4 mg/kg i.m.). Seven wolves received no other immobilization agents (MB wolves), nine received diazepam (0.2 mg/kg i.v.) at the time they were instrumented (MBD wolves), and eight received ketamine (1 mg/kg i.v.) 30 min after instrumentation (MBK30 wolves). Physiologic parameters were monitored during immobilization. The heart rate was similar among the three groups for the first 30 min, and marked bradycardia was noted in one wolf from each group. Hypertension was observed initially in all three groups but was resolved within 10-30 min. The MBK30 wolves had significant elevations in heart rate and transient hypertension after intravenous ketamine administration. Most wolves had mild to moderate metabolic acidemia. Immobilizing drugs were antagonized in all wolves with atipamezole (0.2 mg/kg i.m.) and naloxone (0.02 mg/kg i.m.). The medetomidine-butorphanol-diazepam wolves were also given flumazenil (0.04 mg/kg i.v.). All wolves were standing within 12 min and were fully recovered within 17 min. Medetomamine-butorphanol and MBD combinations provided effective and reversible immobilization of red wolves without the sustained hypertension associated with the use of alpha2-adrenoceptor agonist-ketamine combinations. Delaying the administration of ketamine reduced its hypertensive effects.

Medetomidine at doses of 10, 20 or 30 microg/kg was administered along with 10 microg/kg buprenorphine intramuscularly to 48 dogs requiring sedation for various diagnostic or therapeutic procedures. The heart rate, respiratory rate and degree of sedation were recorded before and 30 minutes after administration of the drugs. Heart rate fell by a mean of 55 per cent and respiratory rate by a mean of 62 per cent. Mean sedation scores were increased in all groups. Administration of atipamezole at the end of the period of sedation produced rapid recoveries, with a mean time to standing of 12 minutes. Animals that were anaesthetised required much less thiopentone than the 10 mg/kg recommended after premedication with acepromazine maleate.

The efficacy and safety of the combination of medetomidine and ketamine was examined in order to establish an adequate chemical immobilization protocol in the Eurasian otter (Lutra lutra) for use during translocation projects in Spain. Thirty-eight Eurasian otters ranging in body mass from 3 to 8.7 kg (mean 5.3 kg) were successfully anesthetized on 82 occasions. The dosage of ketamine was 5.1+/-0.8 (3.4-6.6) mg/kg (mean +/- SD; range) combined with medetomidine at a dosage of 51+/-8 Rg/kg (34-66 microg/kg). In most cases anaesthetic effect occurred within 3 min and the mean induction time was 5.5+/-3.2 min. The mean pulse rate was 95 beats/min. The mean respiratory rate was 32 respirations/min while the relative oxyhemoglobin saturation was 93%. According to these results, this anesthetic protocol is considered safe and can be recommended in wild caught Eurasian otters for immobilization during translocation projects. It is safe, rapid and can be reversed when needed with atipamezole. However caution is required as heart depression resulting in bradychardia may occur.

Ten desert tortoises (Gopherus agassizii) were given i.m. injections of 150 microg/kg of medetomidine. Sedation was achieved in all tortoises by 20 min postinjection and was accompanied by a significant decrease in mean heart and respiratory rates, systolic, diastolic, and mean ventricular pressures, and mean ventricular partial pressure of oxygen (PO2). There was no change in mean blood pH, HCO3, Na+, K+, ionized calcium values, and mean ventricular partial pressure of carbon dioxide (PCO2). There were statistically significant but clinically insignificant changes in mean base excess and pH-corrected ionized calcium values. Atipamezole given to five of the tortoises at 0.75 mg/kg i.m. significantly reversed the sedative effects of the medetomidine, with all tortoises returning to a normal state by 30 min after administration of the reversal agent. In comparison, the other five tortoises given an equal volume of physiologic saline in place of atipamezole (control group) remained significantly sedated for the duration of the study. In addition, the heart rate and ventricular PO2 returned to baseline, but the respiratory rate and ventricular blood pressures were not significantly altered by the atipamezole as compared with those of the control group. These cardiopulmonary and physiologic effects are similar to those seen in some domestic mammals. Medetomidine can be used to safely induce sedation in desert tortoises. For procedures lasting greater than 120 min, supplemental oxygen should be provided. Atipamezole will reverse the sedation but not all of the cardiopulmonary effects, thus necessitating continued monitoring after reversal. Future studies should address the anesthetic and cardiopulmonary effects of medetomidine in combination with other agents such as ketamine and/or butorphanol.