Field immobilization using alfaxalone and alfaxalone–medetomidine in free-ranging koalas (Phascolarctos cinereus): a randomized comparative study

ObjectiveTo characterize and compare two intramuscular drug protocols using alfaxalone and alfaxalone–medetomidine combination for the field immobilization of free-ranging koalas.Study designBlinded, randomized, comparative field study.AnimalsA total of 66 free-ranging koalas from the Mount Lofty Ranges, South Australia.MethodsKoalas were randomly allocated into two groups. Group A animals were given alfaxalone alone at 3.5 mg kg^–1. Group AM animals were given alfaxalone 2 mg kg^–1 and medetomidine 40 μg kg^–1, reversed with atipamezole at 0.16 mg kg^–1. Blinded operators recorded heart rate (HR), respiratory rate (f_R), cloacal temperature, depth of sedation and times to: first effect, sedation suitable for clinical interventions, first arousal and full recovery. Data were analysed using independent t test, Mann–Whitney U test, chi-square analysis and log-rank test at 5% level of significance.ResultsSuitable immobilization for clinical examination and sample collection was achieved in all animals. In groups A and AM, median time to working depth was 6.5 minutes (range: 3.4–15) and 8.1 minutes (range: 4.3–24) and time to complete recovery was 66 minutes (range: 12–138) and 34 minutes (range: 4–84), respectively, following reversal. Time to first effect was significantly shorter in group A (p = 0.013), whereas time to full arousal was significantly shorter in group AM (p = 0.007) probably due to the administration of atipamezole. Maximum HR was 117 ± 28 beats minute^–1 in group A, which was a significant increase from baseline values (p < 0.0001), whereas group AM showed a significant tachypnoea of 67 ± 25 (normal f_R 10–15; p < 0.0001).Conclusions and clinical relevanceBoth the protocols produced immobilization, enabling clinical examination and sample collection; however, protocol AM was more suitable for field work due to shorter recovery times.     

A comparison of the efficacy and cardiorespiratory effects of four medetomidine-based anaesthetic protocols in the red fox (Vulpes vulpes)

ObjectiveTo evaluate the anaesthetic and cardiorespiratory effects of four anaesthetic protocols in red foxes (Vulpes vulpes).Study designProspective, blinded and randomized complete block design.AnimalsTen adult captive red foxes.MethodsFoxes were anaesthetized by intramuscular (IM) injection using four protocols in random order: medetomidine 40 μg kg^?1, midazolam 0.3 mg kg^?1 and butorphanol 0.1 mg kg^?1 (MMiB), medetomidine 40 μg kg^?1 and ketamine 4 mg kg^?1 (MK40/4), medetomidine 60 μg kg^?1 and ketamine 4 mg kg^?1 (MK60/4), medetomidine 40 μg kg^?1 and tiletamine/zolazepam 2 mg kg^?1 (MTZ). Time to lateral recumbency, induction time and time to recovery following IM administration of atipamezole 0.2 mg kg^?1 were recorded. Heart rate (HR), respiratory rate (_fR) and rhythm, blood pressure, rectal temperature, end-tidal CO₂ tension (Pe′Co₂), functional oxygen saturation and presence/absence of interdigital, palpebral and ear reflexes were recorded every 10 minutes, and following administration of atipamezole. Data were analysed using two-way repeated-measures anova with Bonferroni post tests; p < 0.05 was considered significant.ResultsAll protocols produced profound sedation with good muscle relaxation. Only the MMiB protocol diverged significantly from the others. Induction of anaesthesia and recovery time following atipamezole were significantly longer, and f_R and initial HR significantly lower with MMiB than with the other protocols. With all protocols, mean arterial blood pressure (MAP) was initially relatively high (140–156 mmHg), and decreased significantly over time. With all protocols, the administration of atipamezole resulted in a rapid, significant decrease in MAP and an increase in HR.Conclusions and clinical relevanceAll four protocols provided anaesthetic conditions suitable for minor procedures and allowed endotracheal intubation. The cyclohexanone protocols provided quicker and more reliable inductions and recoveries than the MMiB protocol.     

Comparative evaluation of sedative and clinical effects of dexmedetomidine and xylazine in dromedary calves (Camelus dromedarius)

ObjectiveTo compare the sedative and clinical effects of intravenous (IV) administration of dexmedetomidine and xylazine in dromedary calves.Study designExperimental, crossover, randomized, blinded study.AnimalsA total of seven healthy male dromedary calves aged 14 ± 2 weeks and weighing 95 ± 5.5 kg.MethodsCalves were assigned three IV treatments: treatment XYL, xylazine (0.2 mg kg⁻¹); treatment DEX, dexmedetomidine (5 μg kg⁻¹); and control treatment, normal saline (0.01 mL kg⁻¹). Sedation scores, heart rate (HR), respiratory rate (f_R), rectal temperature (RT) and ruminal motility were recorded before (baseline) and after drug administration. Sedation signs were scored using a 4-point scale. One-way anova and Mann–Whitney U tests were used for data analysis.ResultsCalves in treatments XYL and DEX were sedated at 5–60 minutes. Sedation had waned in XYL calves, but not DEX calves, at 60 minutes (p = 0.037). Sedation was not present in calves of any treatment at 90 minutes. HR decreased from baseline in XYL and DEX at 5–90 minutes after drug administration and was lower in DEX than XYL at 5 minutes (p = 0.017). HR was lower in DEX (p = 0.001) and XYL (p = 0.013) than in control treatment at 90 minutes. f_R decreased from baseline in XYL and DEX at 5–60 minutes after drug administration and was lower in DEX than XYL at 5 minutes (p = 0.013). RT was unchanged in any treatment over 120 minutes. Ruminal motility was decreased in XYL at 5, 90 and 120 minutes and absent at 10–60 minutes. Motility was decreased in DEX at 5, 10 and 120 minutes and was absent at 15–90 minutes.Conclusion and clinical relevanceThe duration of sedation from dexmedetomidine (5 μg kg^–1) and xylazine (0.2 mg kg^–1) was similar in dromedary calves.     

The effects of decreased body temperature on the onset,duration and action of medetomidine and its antagonist atipamezole in juvenile farmed estuarine crocodiles (Crocodylus porosus)

ObjectiveTo determine the efficacy of medetomidine for immobilisation of captive juvenile crocodiles over a range of temperatures, and its reversibility with atipamezole.Study designProspective experimental study.AnimalsForty male estuarine crocodiles (body weight 2.0 to 4.8 kg).MethodsEach crocodile was randomly assigned to one of four temperature groups: Group 1:32 °C; Group 2:27 °C; Group 3:22 °C; and Group 4:17 °C (n = 10 for each group). Medetomidine (0.5 mg kg^?1) was administered intramuscularly (IM) into the thoracic limb of all crocodiles. After 50 minutes, all animals from each group received 2.5 mg kg^?1 atipamezole IM in the opposite thoracic limb and time to recovery was documented. Heart and respiratory rates and the degree of immobilisation were monitored every 5 minutes until recovery, and behaviour monitored for 7 subsequent days.ResultsOnset of immobilisation occurred at 15 ± 10 minutes in Group 1, and at 30 ± 10 minutes in Groups 2 and 3. In Group 4, animals were not immobilised. Recovery following atipamezole was 10 ± 5 minutes at all temperatures. One-way analysis of variance (anova) demonstrated a significant difference in induction times between groups (p < 0.01) but not in recovery times following atipamezole administration (p < 0.25). Heart and respiratory rates decreased markedly following medetomidine administration and increased markedly following atipamezole reversal.Conclusions and clinical relevanceMedetomidine administered in the thoracic limb of juvenile captive estuarine crocodiles provides profound sedation or immobilisation at temperatures of 22 °C and above. Atipamezole administered in the contralateral thoracic limb results in consistent reversal of the effects of medetomidine and a return to normal behaviour within 15–20 minutes regardless of temperature. Even though immobilisation is not induced at 17 °C, profound reversible sedation does occur reliably and repeatably.     

Comparison of three anaesthetic protocols in Bennett’s wallabies (Macropus rufogriseus)

ObjectiveInvestigate physiological and sedative/anaesthetic effects of xylazine, medetomidine or dexmedetomidine combined with ketamine in free-ranging Bennett's wallabies.Study designProspective clinical trial.AnimalsTwenty-six adult free-ranging Bennett's wallabies.MethodsAnimals were darted intramuscularly with one of three treatments: xylazine and ketamine, 2.0 and 15.0 mg kg^?1, respectively (XK): medetomidine and ketamine 0.1 and 5.0 mg kg^?1 (MK) and dexmedetomidine and ketamine 0.05 and 5.0 mg kg^?1 (DMK). Body weights were estimated. If the animal was still laterally recumbent after 45 minutes of anaesthesia, then an alpha-2 adrenoceptor antagonist, atipamezole, was administered (XK: 0.4 mg kg^?1, MK: 5 mg kg^?1, DMK: 2.5 mg kg^?1). Heart rate (HR) and respiratory rate (f_R) were recorded at 5-minute intervals and temperature at 10-minute intervals. Venous blood was taken 30 minutes after initial injection. Statistical analysis utilized anova. p < 0.05 was considered significant.ResultsAnimals became recumbent rapidly in all groups. XK animals had muscle twitches, responded to external stimuli, and three animals required additional dosing; this was not observed in the MK and DMK groups. HR (mean ± SD beats minute^?1) in XK (81 ± 4) was significantly higher than MK (74 ± 2) and DMK (67 ± 4). There were no differences in f_R, temperature, blood-gas and biochemical values between groups. More animals in MK (9/10) and DMK (5/6) needed antagonism of anaesthesia compared with XK (1/10). There were no adverse effects after anaesthesia.Conclusion and clinical relevanceCardio-respiratory effects were similar in all groups. There were fewer muscle twitches and reactions to external stimuli in MK and DMK. Duration of anaesthesia was shorter in XK; most animals in MK and DMK needed atipamezole to assist recovery. All three treatments provided satisfactory sedation/anaesthesia and are suitable for use in Bennett's wallabies.     

Anti‐nociceptive and sedative effects of romifidine,tramadol and their combination administered intravenously slowly in ponies

ObjectiveTo evaluate the anti-nociceptive and sedative effects of slow intravenous (IV) injection of tramadol, romifidine, or a combination of both drugs in ponies.Study designWithin-subject blinded.AnimalsTwenty ponies (seven male, 13 female, weighing mean ± SD 268.0 ± 128 kg).MethodsOn separate occasions, each pony received one of the following three treatments IV; romifidine 50 μg kg⁻ (R) tramadol 3 mg kg⁻¹ given over 15 minutes (T) or tramadol 3 mg kg⁻¹followed by romifidine 50 μg kg⁻¹ (RT). Physiologic parameters and caecal borborygmi (CB) were measured and sedation and response to electrical stimulation of the coronary band assessed before and up to 120 minutes following drugs administration. Results were analyzed using the Friedman’s test and 2 way anova as relevant.ResultsWhen compared to baseline, heart (HR, beats minute⁻¹) and respiratory rates (f_R, breaths minute⁻¹) increased with treatment T (highest mean ± SD, HR 43 ± 1; f_R 33 ± 2) and decreased with R (lowest HR 29 ± 1 and f_R 10 ± 4) and RT (lowest HR 32 ± 1 and f_R 9 ± 3). There were no changes in other measured physiological variables. The height of head from the ground was lower following treatments R and TR than T. There was slight ataxia with all three treatments. No excitatory behavioural effects were observed. The response to electrical stimulation was reduced for a prolonged period relative to baseline following all three treatments, the effect being significantly greatest with treatment RT.ConclusionTramadol combined with romifidine at the stated doses proved an effective sedative and anti-nociceptive combination in ponies, with no unacceptable behavioural or physiologic side effects.Clinical relevanceSlow controlled administration of tramadol should reduce the occurrence of adverse behavioural side effects.     

Evaluation of medetomidine-ketamine and dexmedetomidine-ketamine in Chinese water deer (Hydropotes inermis)

ObjectiveTo investigate physiological and sedative/immobilization effects of medetomidine or dexmedetomidine combined with ketamine in free-ranging Chinese water deer (CWD).Study designProspective clinical trial.Animals10 free-ranging adult Chinese water deer (11.0 ± 2.6 kg).MethodsAnimals were darted intramuscularly with 0.08 ± 0.004 mg kg^?1 medetomidine and 3.2 ± 0.2 mg kg^?1 ketamine (MK) or 0.04 ± 0.01 mg kg^?1 dexmedetomidine and 2.9 ± 0.1 mg kg^?1 ketamine (DMK) If the animal was still laterally recumbent after 60 minutes of immobilization, atipamezole was administered intravenously (MK: 0.4 ± 0.02 mg kg^?1, DMK: 0.2 ± 0.03 mg kg^?1). Heart rate (HR) respiratory rate (f_R) and temperature were recorded at 5-minute intervals. Arterial blood was taken 15 and 45 minutes after initial injection. Statistical analysis was performed using Student’s t-test or anova. p < 0.05 was considered significant.ResultsAnimals became recumbent rapidly in both groups. Most had involuntary ear twitches, but there was no response to external stimuli. There were no statistical differences in mean HR (MK: 75 ± 14 beats minute^?1; DMK: 85 ± 21 beats minute^?1), f_R (MK: 51 ± 35 breaths minute^?1; DMK; 36 ± 9 breaths minute^?1), temperature (MK: 38.1 ± 0.7 °C; DMK: 38.4 ± 0.5 °C), blood gas values (MK: PaO₂ 63 ± 6 mmHg, PaCO₂ 49.6 ± 2.6 mmHg, HCO₃^? 30.8 ± 4.5 mmol L^?1; DMK: PaO₂ 77 ± 35 mmHg, PaCO₂ 45.9 ± 11.5 mmHg, HCO₃^? 31.0 ± 4.5 mmol L^?1) and biochemical values between groups but temperature decreased in both groups. All animals needed antagonism of immobilization after 60 minutes. Recovery was quick and uneventful. There were no adverse effects after recovery.Conclusion and clinical relevanceBoth anaesthetic protocols provided satisfactory immobilisation. There was no clear preference for either protocol and both appear suitable for CWD.     

Effects of intramuscular vatinoxan (MK-467), co-administered with medetomidine and butorphanol,on cardiopulmonary and anaesthetic effects of intravenous ketamine in dogs

ObjectiveTo investigate the impact of intramuscular (IM) co-administration of the peripheral α₂-adrenoceptor agonist vatinoxan (MK-467) with medetomidine and butorphanol prior to intravenous (IV) ketamine on the cardiopulmonary and anaesthetic effects in dogs, followed by atipamezole reversal.Study designRandomized, masked crossover study.AnimalsA total of eight purpose-bred Beagle dogs aged 3 years.MethodsEach dog was instrumented and administered two treatments 2 weeks apart: medetomidine (20 μg kg^–1) and butorphanol (100 μg kg^–1) premedication with vatinoxan (500 μg kg^–1; treatment MVB) or without vatinoxan (treatment MB) IM 20 minutes before IV ketamine (4 mg kg^–1). Atipamezole (100 μg kg^–1) was administered IM 60 minutes after ketamine. Heart rate (HR), mean arterial (MAP) and central venous (CVP) pressures and cardiac output (CO) were measured; cardiac (CI) and systemic vascular resistance (SVRI) indices were calculated before and 10 minutes after MVB or MB, and 10, 25, 40, 55, 70 and 100 minutes after ketamine. Data were analysed with repeated measures analysis of covariance models. A p-value <0.05 was considered statistically significant. Sedation, induction, intubation and recovery scores were assessed.ResultsAt most time points, HR and CI were significantly higher, and SVRI and CVP significantly lower with MVB than with MB. With both treatments, SVRI and MAP decreased after ketamine, whereas HR and CI increased. MAP was significantly lower with MVB than with MB; mild hypotension (57–59 mmHg) was recorded in two dogs with MVB prior to atipamezole administration. Sedation, induction, intubation and recovery scores were not different between treatments, but intolerance to the endotracheal tube was observed earlier with MVB.Conclusions and clinical relevanceHaemodynamic performance was improved by vatinoxan co-administration with medetomidine–butorphanol, before and after ketamine administration. However, vatinoxan was associated with mild hypotension after ketamine with the dose used in this study. Vatinoxan shortened the duration of anaesthesia.     

A comparison of cardiopulmonary function,recovery quality,and total dosages required for induction and total intravenous anesthesia with propofol versus a propofol‐ketamine combination in healthy Beagle dogs

ObjectiveTo compare cardiopulmonary function, recovery quality, and total dosages required for induction and 60 minutes of total intravenous anesthesia (TIVA) with propofol (P) or a 1:1 mg mL⁻¹ combination of propofol and ketamine (KP).Study designRandomized crossover study.AnimalsTen female Beagles weighing 9.4 ± 1.8 kg.MethodsDogs were randomized for administration of P or KP in a 1:1 mg mL⁻¹ ratio for induction and maintenance of TIVA. Baseline temperature, pulse, respiratory rate (f_R), noninvasive mean blood pressure (MAP), and hemoglobin oxygen saturation (SpO₂) were recorded. Dogs were intubated and spontaneously breathed room air. Heart rate (HR), f_R, MAP, SpO₂, end tidal carbon dioxide tension (Pe’CO₂), temperature, and salivation score were recorded every 5 minutes. Arterial blood gas analysis was performed at 10, 30, and 60 minutes, and after recovery. At 60 minutes the infusion was discontinued and total drug administered, time to extubation, and recovery score were recorded. The other treatment was performed 1 week later.ResultsKP required significantly less propofol for induction (4.0 ± 1.0 mg kg⁻¹ KP versus 5.3 ±1.1 mg kg⁻¹ P, p = 0.0285) and maintenance (0.3 ± 0.1 mg kg⁻¹ minute⁻¹ KP versus 0.6 ±0.1 mg kg⁻¹ minute⁻¹ P, p = 0.0018). Significantly higher HR occurred with KP. Both P and KP caused significantly lower MAP compared to baseline. MAP was significantly higher with KP at several time points. P had minimal effects on respiratory variables, while KP resulted in significant respiratory depression. There were no significant differences in salivation scores, time to extubation, or recovery scores.Conclusions and clinical relevanceTotal intravenous anesthesia in healthy dogs with ketamine and propofol in a 1:1 mg mL⁻¹ combination resulted in significant propofol dose reduction, higher HR, improved MAP, no difference in recovery quality, but more significant respiratory depression compared to propofol alone.     

Comparison of intranasal and intramuscular ketamine‐midazolam combination in cats

ObjectiveThe aim of the present study was to compare intranasal (INS) and intramuscular (IM) routes of administration of a ketamine-midazolam combination in cats.Study designRandomized block design.AnimalsTwelve healthy mixed breed cats (six males and six females).MethodsThe drug combination was ketamine (14 mg kg⁻¹) and midazolam (0.5 mg kg⁻¹). In the IM group, drugs were injected into quadratus femoris muscle; in the INS. group, the combination dropped equally into the two nostrils. Pulse and respiratory rates, peripheral haemoglobin oxygen saturation (SpO₂) and rectal temperature were monitored before and at intervals after drug administration. Time to onset and duration of sedation and, during recovery to head up, sternal recumbency and recovery were recorded.ResultsThere were no significant differences between the groups in any time measured except for recovery to sternal recumbency, where time was lower in the INS than in the IM (p = 0.034). Respiratory rate was greater in the INS than in the IM group (p = 0.029), but there was no difference between groups in other physiological parameters. In both groups SpO₂ was low before and fell further during sedation.ConclusionsThe results substantiated that INS ketamine-midazolam can produce effective sedation in cats.Clinical relevanceIntranasal (INS) administration of ketamine-midazolam is atraumatic, and its use may avoid the pain of injection of ketamine combinations when this drug is used to induce sedation in cats.     

Effects of vatinoxan in dogs premedicated with medetomidine and butorphanol followed by sevoflurane anaesthesia: a randomized clinical study

ObjectiveTo investigate effects of vatinoxan in dogs, when administered as intravenous (IV) premedication with medetomidine and butorphanol before anaesthesia for surgical castration.Study designA randomized, controlled, blinded, clinical trial.AnimalsA total of 28 client-owned dogs.MethodsDogs were premedicated with medetomidine (0.125 mg m^?2) and butorphanol (0.2 mg kg^?1) (group MB; n = 14), or medetomidine (0.25 mg m^?2), butorphanol (0.2 mg kg^?1) and vatinoxan (5 mg m^?2) (group MB-VATI; n = 14). Anaesthesia was induced 15 minutes later with propofol and maintained with sevoflurane in oxygen (targeting 1.3%). Before surgical incision, lidocaine (2 mg kg^?1) was injected intratesticularly. At the end of the procedure, meloxicam (0.2 mg kg^?1) was administered IV. The level of sedation, the qualities of induction, intubation and recovery, and Glasgow Composite Pain Scale short form (GCPS-SF) were assessed. Heart rate (HR), respiratory rate (f_R), mean arterial pressure (MAP), end-tidal concentration of sevoflurane (Fe′Sevo) and carbon dioxide (Pe′CO₂) were recorded. Blood samples were collected at 10 and 30 minutes after premedication for plasma medetomidine and butorphanol concentrations.ResultsAt the beginning of surgery, HR was 61 ± 16 and 93 ± 23 beats minute^?1 (p = 0.001), and MAP was 78 ± 7 and 56 ± 7 mmHg (p = 0.001) in MB and MB-VATI groups, respectively. No differences were detected in f_R, Pe′CO₂, Fe′Sevo, the level of sedation, the qualities of induction, intubation and recovery, or in GCPS-SF. Plasma medetomidine concentrations were higher in group MB-VATI than in MB at 10 minutes (p = 0.002) and 30 minutes (p = 0.0001). Plasma butorphanol concentrations were not different between groups.Conclusions and clinical relevanceIn group MB, HR was significantly lower than in group MB-VATI. Hypotension detected in group MB-VATI during sevoflurane anaesthesia was clinically the most significant difference between groups.     

The cardiopulmonary effects of a peripheral alpha‐2‐adrenoceptor antagonist,MK‐467, in dogs sedated with a combination of medetomidine and butorphanol

ObjectiveTo compare the cardiopulmonary effects of intravenous (IV) and intramuscular (IM) medetomidine and butorphanol with or without MK-467.Study designProspective, randomized experimental cross-over.AnimalsEight purpose–bred beagles (two females, six males), 3–4 years old and weighing 14.5 ±1.6 kg (mean ± SD).MethodsAll dogs received four different treatments as follows: medetomidine 20 μg kg^?1 and butorphanol tartrate 0.1 mg kg^?1 IV and IM (MB), and MB combined with MK-467,500 μg kg^?1 (MBMK) IV and IM. Heart rate (HR), arterial blood pressures (SAP, MAP, DAP), central venous pressure (CVP), cardiac output, respiratory rate (f_R), rectal temperature (RT) were measured and arterial blood samples were obtained for gas analysis at baseline and at 3, 10, 20, 30, 45 and 60 minutes after drug administration. The cardiac index (CI), systemic vascular resistance index (SVRI) and oxygen delivery index (DO₂I) were calculated. After the follow-up period atipamezole 50 μg kg^?1 IM was given to reverse sedation.ResultsHR, CI and DO₂I were significantly higher with MBMK after both IV and IM administration. Similarly, SAP, MAP, DAP, CVP, SVRI and RT were significantly lower after MBMK than with MB. There were no differences in f_R between treatments, but arterial partial pressure of oxygen decreased transiently after all treatments. Recoveries were uneventful following atipamezole administration after all treatments.Conclusions and clinical relevanceMK-467 attenuated the cardiovascular effects of a medetomidine-butorphanol combination after IV and IM administration.     

Preliminary studies of chemical immobilization of captive juvenile estuarine (Crocodylus porosus) and Australian freshwater (C. johnstoni) crocodiles with medetomidine and reversal with atipamezole

ObjectiveTo establish a safe, reliable and reversible immobilization protocol for captive juvenile crocodiles.Study designProspective, randomized, clinical study.AnimalsThirty male estuarine crocodiles (body mass 1–12.1 kg) and 10 male Australian freshwater crocodiles (body mass 4.1–12.8 kg).MethodsAn 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.ResultsImmobilization 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 mg 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 relevanceMedetomidine 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.     

Short term pharmacological immobilization in macaque monkeys

ObjectiveTo develop a safe and effective immobilization protocol in rhesus monkeys, which is not based on dissociative anaesthetic agent.Study designProspective, randomised, experimental trial.AnimalsTwenty rhesus monkeys, weighing 2.6–8.0 kg, 1–3 years of age, of both sexes.MethodsThe monkeys received 50 μg kg^?1 medetomidine, 0.25 mg kg^?1 midazolam and 5 μg kg^?1 fentanyl with 150 IU hyaluronidase intramuscularly (IM). The animals were closely observed for behavioural changes and reaction to sound stimulus. Pulse rate and oxygen saturation of haemoglobin (SpO₂) were monitored every 5 minutes, for 20 minutes. After this period, 250 μg kg^?1 atipamezole or a placebo was administered IM and behavioural changes were closely observed.ResultsFull immobilization was observed after mean 269 ± SD 116 seconds. Ten minutes after injection mean arterial oxygen saturation of haemoglobin was 94 ± 4%, but did not fall significantly further. The median pulse rate was 116 beats minute^?1 5 minutes after the administration of the drug. This level further decreased to a median level of 108 beats minute^?1 20 minutes after the drug's administration. The median time to recover from immobilization was significantly shorter after atipamezole administration when compared to placebo (2.7 versus 55 minutes). All animals awoke smoothly and no side effects such as vomiting or agitation were observed.ConclusionsShort term and reversible pharmacological immobilization was achieved using combination of midazolam, medetomidine, and fentanyl.Clinical relevanceThe present study demonstrates that 20-minute pharmacological immobilization with a combination of midazolam, medetomidine, and fentanyl is feasible in rhesus monkeys with minimal effect on heart rate.     

Evaluation of xylazine–alfaxalone anesthesia for field castration in donkey foals

ObjectiveTo evaluate the anesthetic and cardiopulmonary effects of xylazine–alfaxalone anesthesia in donkey foals undergoing field castration.Study designProspective clinical study.AnimalsA group of seven standard donkeys aged [median (range)] 12 (10–26) weeks, weighing 47.3 (37.3–68.2) kg.MethodsDonkeys were anesthetized with xylazine (1 mg kg⁻¹) intravenously (IV) followed 3 minutes later by alfaxalone (1 mg kg⁻¹) IV. Additional doses of xylazine (0.5 mg kg⁻¹) and alfaxalone (0.5 mg kg⁻¹) IV were administered as needed to maintain surgical anesthesia. Intranasal oxygen was supplemented at 3 L minute⁻¹. Heart rate (HR), respiratory rate (f_R) and mean arterial pressure (MAP) by oscillometry were recorded before drug administration and every 5 minutes after induction of anesthesia. Peripheral oxygen saturation (SpO₂) was recorded every 5 minutes after induction. Time to recumbency after alfaxalone administration, time to anesthetic re-dose, time to first movement, sternal and standing after last anesthetic dose and surgery time were recorded. Induction and recovery quality were scored (1, very poor; 5, excellent).ResultsMedian (range) induction score was 5 (1–5), and recovery score 4 (1–5). Overall, two donkeys were assigned a score of 1 (excitement) during induction or recovery. HR and MAP during the procedure did not differ from baseline. f_R was decreased at 5 and 10 minutes but was not considered clinically significant. SpO₂ was <90% at one time point in two animals.Conclusions and clinical relevanceXylazine–alfaxalone anesthesia resulted in adequate conditions for castration in 12 week old donkeys. While the majority of inductions and recoveries were good to excellent, significant excitement occurred in two animals and may limit the utility of this protocol for larger donkeys. Hypoxemia occurred despite intranasal oxygen supplementation.     

Sedative effects and pharmacokinetics of detomidine when administered intravenously and intravaginally as a gel in alpacas

ObjectivesTo evaluate the sedative effects and pharmacokinetics of detomidine gel administered intravaginally to alpacas in comparison with intravenously (IV) administered detomidine.Study designRandomized, crossover, blinded experiment.AnimalsA group of six healthy adult female Huacaya alpacas (70.3 ± 7.9 kg).MethodsAlpacas were studied on two occasions separated by ≥5 days. Treatments were IV detomidine hydrochloride (70 μg kg⁻¹; treatment DET–IV) or detomidine gel (200 μg kg⁻¹; treatment DET–VAG) administered intravaginally. Sedation and heart rate (HR) were evaluated at intervals for 240 minutes. Venous blood was collected at intervals for 360 minutes after treatment for analysis of detomidine, carboxydetomidine and hydroxydetomidine using liquid chromatography–tandem mass spectrometry. Measured variables were compared between treatments and over time using mixed model analysis. Data are presented as the mean ± standard error of the mean, and a p value of <0.05 was considered significant.ResultsOnset of sedation was faster in treatment DET–IV (1.6 ± 0.2 minutes) than in treatment DET–VAG (13.0 ± 2.5 minutes). Time to maximum sedation was shorter in treatment DET–IV (8.3 ± 1.3 minutes) than in treatment DET–VAG (25 ± 4 minutes). Duration of sedation was not different between treatments. There was a significant linear relationship between sedation score and plasma detomidine concentration. HR was less than baseline for 60 and 125 minutes for treatments DET–IV and DET–VAG, respectively. The maximal decrease in HR occurred at 15 minutes for both treatments. The mean maximum plasma concentration of detomidine, time to maximum concentration and bioavailability for treatment DET–VAG were 39.6 ng mL⁻¹, 19.9 minutes and 20%, respectively.Conclusions and clinical relevanceDetomidine administration at the doses studied resulted in moderate sedation when administered IV or intravaginally to alpacas.     

Behavioural and cardiovascular effects of medetomidine constant rate infusion compared with detomidine for standing sedation in horses

ObjectiveTo compare the efficacy of a medetomidine constant rate infusion (CRI) with a detomidine CRI for standing sedation in horses undergoing high dose rate brachytherapy.Study designRandomized, controlled, crossover, blinded clinical trial.AnimalsA total of 50 horses with owner consent, excluding stallions.MethodsEach horse was sedated with intravenous acepromazine (0.02 mg kg^–1), followed by an α₂-adrenoceptor agonist 30 minutes later and then by butorphanol (0.1 mg kg^–1) 5 minutes later. A CRI of the same α₂-adrenoceptor agonist was started 10 minutes after butorphanol administration and maintained for the treatment duration. Treatments were given 1 week apart. Each horse was sedated with detomidine (bolus dose, 10 μg kg^–1; CRI, 6 μg kg^–1 hour^–1) or medetomidine (bolus dose, 5 μg kg^–1; CRI, 3.5 μg kg^–1 hour^–1). If sedation was inadequate, a quarter of the initial bolus of the α₂-adrenoceptor agonist was administered. Heart rate (HR) was measured via electrocardiography, and sedation and behaviour evaluated using a previously published scale. Between treatments, behaviour scores were compared using a Wilcoxon signed-rank test, frequencies of arrhythmias with chi-square tests, and HR with two-tailed paired t tests. A p value <0.05 indicated statistical significance.ResultsTotal treatment time for medetomidine was longer than that for detomidine (p = 0.04), and ear movements during medetomidine sedation were more numerous than those during detomidine sedation (p = 0.03), suggesting there may be a subtle difference in the depth of sedation. No significant differences in HR were found between treatments (p ≥ 0.09). Several horses had arrhythmias, with no difference in their frequency between the two infusions.Conclusions and clinical relevanceMedetomidine at this dose rate may produce less sedation than detomidine. Further studies are required to evaluate any clinical advantages to either drug, or whether a different CRI may be more appropriate.     

Cardiovascular and autonomic nervous effects of edrophonium and atropine combinations during neuromuscular blockade antagonism in sheep

ObjectiveTo study heart rate (HR), arterial blood pressure (BP) and autonomic nervous (AN) effects of edrophonium–atropine combinations during neuromuscular blockade (NMB) antagonism in sheep.Experimental design Randomized, prospective and experimental study.AnimalsSeventy-eight Scottish blackface ewes; mean age: 4.5 years; mean body mass: 54 kg.MethodsAfter induction with IV etomidate (0.5 mg kg⁻¹) and midazolam (0.5 mg kg⁻¹), anaesthesia was maintained with halothane and NMB produced with atracurium or mivacurium. In the first study (n = 53), the electrocardiographic (ECG), HR, BP and AN effects of low (40 μg kg⁻¹) and high (80 μg kg⁻¹) atropine doses combined with either of two edrophonium doses (0.5 or 1.0 mg kg⁻¹) were investigated. These variables were also measured in a second study when edrophonium (1.0 mg kg⁻¹) was administered 5 minutes before atropine (80 μg kg⁻¹) and vice versa. Data were analysed using one-way within-subjects and repeated measures anova.ResultsIn the first study, all combinations reversed NMB but significantly (p < 0.001) increased HR and BP within 2 minutes without arrhythmias. In the second study, edrophonium (1.0 mg kg⁻¹) significantly increased HR and BP, saliva flow (n = 1) and lung sounds (n = 3) and caused ECG changes (n = 1). Cardiovascular changes were partially reversed by atropine (80 μg kg⁻¹) administered 5 minutes later. Administered first, atropine (80 μg kg⁻¹) significantly decreased HR and BP effects which were fully (HR) and partially (BP) reversed by edrophonium (1 mg kg⁻¹) administered 5 minutes later.Conclusion and clinical relevance The cardiovascular effects of edrophonium and atropine were opposite to those reported in humans and dogs. Edrophonium (0.5 mg kg⁻¹) and atropine (80 μg kg⁻¹) caused the mildest HR changes without ECG and noncardiac AN disturbances, and is recommended for the antagonism of NMB in sheep.