Immobilization quality and cardiopulmonary effects of etorphine alone compared with etorphine–azaperone in blesbok (Damaliscus pygargus phillipsi)

ObjectiveTo evaluate the immobilization quality and cardiopulmonary effects of etorphine alone compared with etorphine–azaperone in blesbok (Damaliscus pygargus phillipsi).Study designBlinded, randomized, crossover design.AnimalsA total of 12 boma-habituated female blesbok weighing [mean ± standard deviation (SD)] 57.5 ± 2.5 kg.MethodsEach animal was administered etorphine (0.09 mg kg^–1) or etorphine–azaperone (0.09 mg kg^–1; 0.35 mg kg^–1) intramuscularly with 1-week intertreatment washout period. Time to first sign of altered state of consciousness and immobilization time were recorded. Physiological variables were recorded, arterial blood samples were taken during a 40-minute immobilization period, and naltrexone (mean ± SD: 1.83 ± 0.06 mg kg^–1) was intravenously administered. Recovery times were documented, and induction, immobilization and recovery were subjectively scored. Statistical analyses were performed; p < 0.05 was significant.ResultsNo difference was observed in time to first sign, immobilization time and recovery times between treatments. Time to head up was longer with etorphine–azaperone (0.5 ± 0.2 versus 0.4 ± 0.2 minutes; p = 0.015). Etorphine caused higher arterial blood pressures (mean: 131 ± 17 versus 110 ± 11 mmHg, p < 0.0001), pH, rectal temperature and arterial oxygen partial pressure (59.2 ± 7.7 versus 42.2 ± 9.8 mmHg), but lower heart (p = 0.002) and respiratory rates (p = 0.01). Etorphine–azaperone combination led to greater impairment of ventilatory function, with higher end-tidal carbon dioxide (p < 0.0001) and arterial partial pressure of carbon dioxide (58.0 ± 4.5 versus 48.1 ± 5.1 mmHg). Immobilization quality was greater with etorphine-azaperone than with etorphine alone (median scores: 4 versus 3; p < 0.0001).Conclusions and clinical relevanceBoth treatments provided satisfactory immobilization of blesbok; however, in addition to a deeper level of immobilization, etorphine–azaperone caused greater ventilatory impairment. Oxygen supplementation is recommended with both treatments.     

Immobilization of African buffaloes (Syncerus caffer) using etorphine–midazolam compared with etorphine–azaperone

ObjectiveTo compare induction times and physiological effects of etorphine–azaperone with etorphine–midazolam immobilization in African buffaloes.Study designRandomized crossover study.AnimalsA group of 10 adult buffalo bulls (mean body weight 353 kg).MethodsEtorphine–azaperone (treatment EA; 0.015 and 0.15 mg kg^–1, respectively) and etorphine–midazolam (treatment EM; 0.015 and 0.15 mg kg^–1, respectively) were administered once to buffaloes, 1 week apart. Once in sternal recumbency, buffaloes were instrumented and physiological variables recorded at 5 minute intervals, from 5 minutes to 20 minutes. Naltrexone (20 mg mg^–1 etorphine dose) was administered intravenously at 40 minutes. Induction (dart placement to recumbency) and recovery (naltrexone administration to standing) times were recorded. Arterial blood samples were analysed at 5 and 20 minutes. Physiological data were compared between treatments using a general linear mixed model and reported as mean ± standard deviation. Time data were compared using Mann-Whitney U test and reported as median (interquartile range) with p ≤ 0.05.ResultsActual drug doses administered for etorphine, azaperone and midazolam were 0.015 ± 0.001, 0.15 ± 0.01 and 0.16 ± 0.02 mg kg^–1, respectively. Induction time for treatment EA was 3.3 (3.6) minutes and not different from 3.2 (3.2) minutes for treatment EM. The overall mean arterial blood pressure was significantly lower for treatment EA (102 ± 25 mmHg) than that for treatment EM (163 ± 18 mmHg) (p < 0.001). The PaO₂ for treatment EA (37 ± 12 mmHg; 5.0 ± 1.6 kPa) was not different from that for treatment EM (43 ± 8 mmHg; 5.8 ± 1.1 kPa). Recovery time was 0.8 (0.6) minutes for treatment EA and did not differ from 1.1 (0.6) minutes for treatment EM.Conclusions and clinical relevanceTreatment EA was as effective as treatment EM for immobilization in this study. However, systemic arterial hypertension was a concern with treatment EM, and both combinations produced clinically relevant hypoxaemia. Supplemental oxygen administration is recommended with both drug combinations.     

Comparison of cardiopulmonary effects of etorphine and thiafentanil administered as sole agents for immobilization of impala (Aepyceros melampus)

ObjectiveTo compare the cardiopulmonary effects of the opioids etorphine and thiafentanil for immobilization of impala.Study designTwo-way crossover, randomized study.AnimalsA group of eight adult female impala.MethodsImpala were given two treatments: 0.09 mg kg^–1 etorphine or 0.09 mg kg^–1 thiafentanil via remote dart injection. Time to recumbency, quality of immobilization and recovery were assessed. Respiratory rate, heart rate (HR), mean arterial blood pressure (MAP) and arterial blood gases were measured. A linear mixed model was used to analyse the effects of treatments, treatments over time and interactions of treatment and time (p < 0.05).ResultsTime to recumbency was significantly faster with thiafentanil (2.0 ± 0.8 minutes) than with etorphine (3.9 ± 1.6 minutes; p = 0.007). Both treatments produced bradypnoea, which was more severe at 5 minutes with thiafentanil (7 ± 4 breaths minute^–1) than with etorphine (13 ± 12 breaths minute^–1; p = 0.004). HR increased with both treatments but significantly decreased over time when etorphine (132 ± 17 to 82 ± 11 beats minute^–1) was compared with thiafentanil (113 ± 22 to 107 ± 36 beats minute^–1; p < 0.001). Both treatments caused hypertension which was more profound with thiafentanil (mean overall MAP = 140 ± 14 mmHg; p < 0.001). Hypoxaemia occurred with both treatments but was greater with thiafentanil [PaO₂ 37 ± 13 mmHg (4.9 kPa)] than with etorphine [45 ± 16 mmHg (6.0 kPa)] 5 minutes after recumbency (p < 0.001). After 30 minutes, PaO₂ increased to 59 ± 10 mmHg (7.9 kPa) with both treatments (p < 0.001).Conclusions and clinical relevanceThe shorter time to recumbency with thiafentanil may allow easier and faster retrieval in the field. However, thiafentanil caused greater hypertension, and ventilatory effects during the first 10 minutes, after administration.     

Evaluation of intramuscular anesthetic protocols in healthy domestic horses

ObjectiveTo assess anesthetic induction, recovery quality and cardiopulmonary variables after intramuscular (IM) injection of three drug combinations for immobilization of horses.Study designRandomized, blinded, three-way crossover prospective design.AnimalsA total of eight healthy adult horses weighing 470–575 kg.MethodsHorses were administered three treatments IM separated by ≥1 week. Combinations were tiletamine–zolazepam (1.2 mg kg⁻¹), ketamine (1 mg kg⁻¹) and detomidine (0.04 mg kg⁻¹) (treatment TKD); ketamine (3 mg kg⁻¹) and detomidine (0.04 mg kg⁻¹) (treatment KD); and tiletamine–zolazepam (2.4 mg kg⁻¹) and detomidine (0.04 mg kg⁻¹) (treatment TD). Parametric data were analyzed using mixed model linear regression. Nonparametric data were compared using Skillings–Mack test. A p value <0.05 was considered statistically significant.ResultsAll horses in treatment TD became recumbent. In treatments KD and TKD, one horse remained standing. PaO₂ 15 minutes after recumbency was significantly lower in treatments TD (p < 0.0005) and TKD (p = 0.001) than in treatment KD. Times to first movement (25 ± 15 minutes) and sternal recumbency (55 ± 11 minutes) in treatment KD were faster than in treatments TD (57 ± 17 and 76 ± 19 minutes; p < 0.0005, p = 0.001) and TKD (45 ± 18 and 73 ± 31 minutes; p = 0.005, p = 0.021). There were no differences in induction quality, muscle relaxation score, number of attempts to stand or recovery quality.Conclusions and clinical relevanceIn domestic horses, IM injections of tiletamine–zolazepam–detomidine resulted in more reliable recumbency with a longer duration when compared with ketamine–detomidine and tiletamine–zolazepam–ketamine–detomidine. Recoveries were comparable among protocols.     

Evaluation of butorphanol-azaperone-medetomidine in captive cheetah (Acinonyx jubatus) immobilization

Objective

The butorphanol-azaperone-medetomidine fixed-dose combination (BAM, respectively, 30-12-12 mg mL^?1) with subsequent antagonism by naltrexone-atipamezole was evaluated for reversible immobilization of captive cheetahs (Acinonyx jubatus).

Evaluation of butorphanol–azaperone–medetomidine (BAM) in captive blesbok immobilization (Damaliscus pygargus phillipsi)

Objective

The fixed-dose combination of butorphanol, azaperone and medetomidine (BAM; 30, 12 and 12 mg mL^?1, respectively) with subsequent antagonism by naltrexone–atipamezole was evaluated for reversible immobilization of captive blesbok (Damaliscus pygargus phillipsi).

The utility of a novel formulation of alfaxalone in a remote delivery system

ObjectiveTo quantify induction time, reliability, physiological effects, recovery quality and dart volume of a novel formulation of alfaxalone (40 mg mL^?1) used in combination with medetomidine and azaperone for the capture and handling of wild bighorn sheep.Study designProspective clinical study.AnimalsA total of 23 wild bighorn sheep (Ovis canadensis) in Sheep River Provincial Park, AB, Canada.MethodsFree-ranging bighorn sheep were immobilized using medetomidine, azaperone and alfaxalone delivered with a remote delivery system. Arterial blood was collected for measurement of blood gases, physiologic variables (temperature, heart and respiratory rates) were recorded and induction and recovery length and quality were scored.ResultsData from 20 animals were included. Administered dose rates were alfaxalone (0.99 ± 0.20 mg kg^?1; 40 mg mL^?1), azaperone (0.2 ± 0.04 mg kg^?1; 10 mg mL^?1) and medetomidine (0.16 ± 0.03 mg kg^?1; 30 mg mL^?1). The mean drug volume injected was 1.51 mL. The median (range) induction time was 7.7 (5.8–9.7) minutes, and recovery was qualitatively smooth.Conclusions and clinical relevanceAn increased concentration formulation of alfaxalone was administered in combination with medetomidine and azaperone, and resulted in appropriate anesthesia for the capture and handling of bighorn sheep. The dart volume was small, with potential for reducing capture-related morbidity.     

Comparison of some cardiopulmonary effects of etorphine and thiafentanil during the chemical immobilization of blesbok (Damaliscus pygargus phillipsi)

ObjectiveTo determine the cardiopulmonary effects of etorphine and thiafentanil for immobilization of blesbok.Study designBlinded, randomized, two-way crossover study.AnimalsA group of eight adult female blesbok.MethodsAnimals were immobilized twice, once with etorphine (0.09 mg kg^–1) and once with thiafentanil (0.09 mg kg^–1) administered intramuscularly by dart. Immobilization quality was assessed and analysed by Wilcoxon signed-rank test. Time to final recumbency was compared between treatments by one-way analysis of variance. Cardiopulmonary effects including respiratory rate (?_R), arterial blood pressures and arterial blood gases were measured. A linear mixed model was used to assess the effects of drug treatments over the 40 minute immobilization period. Significant differences between treatments, for treatment over time as well as effect of treatment by time on the variables, were analysed (p < 0.05).ResultsThere was no statistical difference (p = 0.186) between treatments for time to recumbency. The mean ?_R was lower with etorphine (14 breaths minute^–1) than with thiafentanil (19 breaths minute^–1, p = 0.034). The overall mean PaCO₂ was higher with etorphine [45 mmHg (6.0 kPa)] than with thiafentanil [41 mmHg (5.5 kPa), p = 0.025], whereas PaO₂ was lower with etorphine [53 mmHg (7.1 kPa)] than with thiafentanil [64 mmHg (8.5 kPa), p < 0.001]. The systolic arterial pressure measured throughout all time points was higher with thiafentanil than with etorphine (p = 0.04). The difference varied from 30 mmHg at 20 minutes after recumbency to 14 mmHg (standard error difference 2.7 mmHg) at 40 minutes after recumbency. Mean and diastolic arterial pressures were significantly higher with thiafentanil at 20 and 25 minute measurement points only (p < 0.001).ConclusionsBoth drugs caused clinically relevant hypoxaemia; however, it was less severe with thiafentanil. Ventilation was adequate. Hypertension was greater and immobilization scores were lower with thiafentanil.     

Comparison of azaperone–detomidine–butorphanol–ketamine and azaperone–tiletamine–zolazepam for anaesthesia in piglets

ObjectiveTo investigate a combination of azaperone, detomidine, butorphanol and ketamine (DBK) in pigs and to compare it with the combination of azaperone, tiletamine and zolazepam (TZ).Study designProspective, randomized, blinded, cross–over study.AnimalsTwelve clinically healthy crossbred pigs aged about 2 months and weighing 16–25 kg.MethodsPigs were pre–medicated with azaperone (4 mg kg^?1). Ten minutes later anaesthesia was induced with intramuscular DBK (detomidine 0.08 mg kg^?1, butorphanol 0.2 mg kg^?1, ketamine 10 mg kg^?1) or TZ (tiletamine and zolazepam 5 mg kg^?1). The pigs were positioned in dorsal recumbency. Heart and respiratory rates, posture, anaesthesia score, PaO₂, PaCO₂, pH and bicarbonate concentration were measured. t–test was used to compare the areas under time–anaesthesia index curve (AUC_anindex) between treatments. Data concerning heart and respiratory rates, PaO₂, PaCO₂ and anaesthesia score were analysed with anova for repeated measurements. Wilcoxon signed rank test was used for the data concerning the duration of sedation and anaesthesia.ResultsThe sedation, analgesia and anaesthesia lasted longer after DBK than TZ. The AUC_anscore were 863 ± 423 and 452 ± 274 for DBK and TZ, respectively (p = 0.002). The duration of surgical anaesthesia lasted a median of 35 minutes (0–105 minutes) after DBK and a median of 15 minutes (0–35 minutes) after TZ (p = 0.05). Four pigs after DBK and six after TZ did not achieve the plane of surgical anaesthesia. The heart rate was lower after DBK than after TZ. Both treatments had similar effects on the other parameters measured.ConclusionsAt the doses used DBK was more effective than TZ for anaesthesia in pigs under field conditions.Clinical relevanceThe combinations can be used for sedation and minor field surgery in pigs. The doses and drugs chosen were insufficient to produce a reliable surgical plane of anaesthesia in these young pigs.     

Anaesthesia with medetomidine,midazolam and ketamine in six gorillas after premedication with oral zuclopenthixol dihydrochloride

ObjectiveTo evaluate the effects of medetomidine, midazolam and ketamine (MMK) in captive gorillas after premedication with oral zuclopenthixol.Study designCase series.AnimalsSix gorillas, two males and four females, aged 9–52 years and weighing 63–155 kg.MethodsThe gorillas were given zuclopenthixol dihydrochloride 0.2 ± 0.05 mg kg^?1 per os twice daily for 3 days for premedication. On the day of anaesthesia the dose of zuclopenthixol was increased to 0.27 mg kg^?1 and given once early in the morning. Anaesthesia was induced with medetomidine 0.04 ± 0.004 mg kg^?1, midazolam 0.048 ± 0.003 mg kg^?1 and ketamine 4.9 ± 0.4 mg kg^?1 intramuscularly (IM). Upon recumbency, the trachea was intubated and anaesthesia was maintained on 1–2% isoflurane in oxygen. Physiological parameters were monitored every 10 minutes and arterial blood gas analysis was performed once 30–50 minutes after initial darting. At the end of the procedure, 42–115 minutes after initial darting, immobilisation was antagonized with atipamezole 0.21 ± 0.03 mg kg^?1 and sarmazenil 5 ± 0.4 μg kg^?1 IM.ResultsRecumbency was reached within 10 minutes in five out of six animals. One animal required two additional darts before intubation was feasible. Heart rate ranged from 60 to 85 beats minute^?1, respiratory rate from 17 to 46 breaths minute^?1 and temperature from 36.9 to 38.3 °C. No spontaneous recoveries were observed and anaesthetic level was stable. Blood gas analyses revealed mild respiratory acidosis, and mean PaO₂ was 24.87 ± 17.16 kPa (187 ± 129 mmHg) with all values being above 13.4 kPa (101 mmHg). Recovery was smooth and gorillas were sitting within 25 minutes.Conclusion and clinical relevanceThe drug combination proved to be effective in anaesthetizing captive gorillas of various ages and both sexes, with minimal cardio-respiratory changes.     

Evaluation of butorphanol, medetomidine and midazolam as a reversible narcotic combination in free-ranging African lions (Panthera leo)

ObjectiveTo evaluate the effects of the combination butorphanol, medetomidine and midazolam (BMM) and its reversibility in lions.Study designProspective clinical trial.AnimalsThirty free-ranging lions, 10 male and 20 female, weighing 81-210 kg.MethodsLions were immobilised with butorphanol mean 0.31 ± SD 0.034 mg kg^?1, medetomidine 0.052 ± 0.006 mg kg^?1, midazolam 0.21 ± 0.024 mg kg^?1 and hyaluronidase 1250 IU administered intramuscularly with a dart gun. Upon recumbency, physiological parameters and anaesthetic depth were monitored 10-15 minutes after darting (T1) and repeated every 10 minutes for a further 30 minutes (T2, T3, T4). Arterial blood gas analyses were performed at T1 and T4. At the end of the procedure, 45-60 minutes after initial darting, immobilisation was reversed with naltrexone 0.68 ± 0.082 mg kg^?1, atipamezole 0.26 ± 0.031 mg kg^?1, and flumazenil 0.0032 ± 0.0007 mg kg^?1 administered intravenously and subcutaneously.ResultsThe BMM combination rapidly induced immobilisation and lateral recumbency was reached within 7.25 ± 2.3 minutes. Median induction score [scored 1 (excellent) to 4 (poor)] was 1.4 (range 1-2). Cardio-respiratory parameters were stable. Heart rate varied from 32 to 72 beats per minute, respiratory rate from 14 to 32 breaths minute^?1 and rectal temperature from 36.6 to 40.3 °C. No sudden arousals were observed. Arterial blood gas analyses revealed a mean pH of 7.33, PaCO₂ of 33 mmHg and PaO₂ of 87 mmHg. Mild to moderate hypoxemia was seen in four lions. Recovery was smooth and lions were walking within 4.4 ± 4.25 minutes. Median recovery score [scored 1 (excellent) to 4 (poor)] was 1.3 (range 1-2).Conclusion and clinical relevanceThe drug combination proved to be effective in immobilising free-ranging healthy lions of both sexes with minimal cardio-respiratory changes.     

Effects of intravenous acepromazine and butorphanol on propofol dosage for induction of anesthesia in healthy Beagle dogs

ObjectiveTo determine the effects of intravenous (IV) premedication with acepromazine, butorphanol or their combination, on the propofol anesthetic induction dosage in dogs.Study designProspective, blinded, Latin square design.AnimalsA total of three male and three female, healthy Beagle dogs, aged 3.79 ± 0.02 years, weighing 10.6 ± 1.1 kg, mean ± standard deviation.MethodsEach dog was assigned to one of six IV treatments weekly: 0.9% saline (treatment SAL), low-dose acepromazine (0.02 mg kg^–1; treatment LDA), high-dose acepromazine (0.04 mg kg^–1; treatment HDA), low-dose butorphanol (0.2 mg kg^–1; treatment LDB), high-dose butorphanol (0.4 mg kg^–1; treatment HDB); and a combination of acepromazine (0.02 mg kg^–1) with butorphanol (0.2 mg kg^–1; treatment ABC). Physiologic variables and sedation scores were collected at baseline and 10 minutes after premedication. Then propofol was administered at 1 mg kg^–1 IV over 15 seconds, followed by boluses (0.5 mg kg^–1 over 5 seconds) every 15 seconds until intubation. Propofol dose, physiologic variables, recovery time, recovery score and adverse effects were monitored and recorded. Data were analyzed using mixed-effects anova (p < 0.05).ResultsPropofol dosage was lower in all treatments than in treatment SAL (4.4 ± 0.5 mg kg^–1); the largest decrease was recorded in treatment ABC (1.7 ± 0.3 mg kg^–1). Post induction mean arterial pressures (MAPs) were lower than baseline values of treatments LDA, HDA and ABC. Apnea and hypotension (MAP < 60 mmHg) developed in some dogs in all treatments with the greatest incidence of hypotension in treatment ABC (4/6 dogs).Conclusions and clinical relevanceAlthough the largest decrease in propofol dosage required for intubation was after IV premedication with acepromazine and butorphanol, hypotension and apnea still occurred.     

The disposition and behavioral effects of methadone in Greyhounds

ObjectiveTo determine the behavioral effects and pharmacokinetics of methadone in healthy Greyhounds.Study designProspective experimental study.AnimalsThree male and three female healthy Greyhounds.MethodsMethadone hydrochloride, 0.5 mg kg⁻¹ IV (equivalent to 0.45 mg kg⁻¹ methadone base), was administered as an IV bolus. Trained observers subjectively assessed the behavioral effects of methadone. Blood samples were obtained at predetermined time points and plasma methadone concentrations were measured by liquid chromatography with tandem mass spectrometry. Pharmacokinetic variables were estimated with computer software.ResultsMethadone was well tolerated by the dogs with panting and defecation observed as adverse effects. Mild sedation was present, but no vomiting, excitement, or dysphoria was observed. The elimination half-life, volume of distribution, and plasma clearance were 1.53 ± 0.18 hours, 7.79 ± 1.87 L kg⁻¹, and 56.04 ± 9.36 mL minute⁻¹ kg⁻¹, respectively.Conclusions and clinical relevanceMethadone was well tolerated by Greyhounds. The volume of distribution was larger than expected, with resultant lower plasma concentrations than expected. Higher doses may need to be administered to Greyhounds in comparison with non-Greyhound dogs in order to achieve similar plasma drug concentrations. A dosage of 1–1.5 mg kg⁻¹ every 3–4 hours is suggested for future studies of analgesic efficacy of methadone in Greyhounds.     

Chemical immobilization of Weddell seals (Leptonychotes weddellii) by ketamine/midazolam combination

ObjectiveTo provide reliable, effective immobilization for Weddell seals under extreme field conditions using an injectable ketamine/midazolam combination.Study designObservational study.AnimalsThirty adult Weddell seals (12 male, 18 female) in Erebus Bay, Antarctica, body mass (mean ± SD) 412 ± 47 kg, aged 9–27 years.MethodsSeals were immobilized with a target dose of 2 mg kg^?1 ketamine hydrochloride and 0.1 mg kg^?1 midazolam hydrochloride (IM), based on visually estimated body mass. When required, maintenance doses were administered at a target of 0.5 mg kg^?1 ketamine hydrochloride and 0.025 mg kg^?1 midazolam hydrochloride (IV).ResultsComplete immobilization was achieved in 33 of 40 injections (14 of which were repeat events on the same individual). Time to immobilization averaged 12 ± 4 minutes, with a duration of initial immobility of 38 ± 19 minutes. Total immobilization time varied by handling protocol, including condition assessment and muscle biopsy (Protocol 1, 60 ± 13 minutes), condition assessment and instrument attachment (Protocol 2, 154 ± 13 minutes), and condition assessment, muscle biopsy and instrument retrieval (Protocol 3, 48 ± 8 minutes). Overall, a total immobilization time of 114 ± 60 minutes was accomplished with 4 ± 4 maintenance doses, and an average recovery time of 36 ± 17 minutes. Most effects of the anesthetic combination were unrelated to mass, age, sex or total body fat. However, leaner seals had longer duration of initial immobility (% and kg total body fat) and recovery times (kg fat). Apnea events were uncommon and treated effectively with doxapram. No animals died.Conclusions and clinical relevanceReliable and effective field immobilization of Weddell seals was accomplished with a low dose of ketamine hydrochloride and midazolam hydrochloride, utilizing IM injection initially and IV maintenance methods.     

The effects of medetomidine on the action of vecuronium in dogs anaesthetized with halothane and nitrous oxide

ObjectiveTo quantify the effects of medetomidine on the onset and duration of vecuronium-induced neuromuscular blockade in dogs.Study designRandomized, prospective clinical study.AnimalsTwenty-four, healthy, client-owned dogs of different breeds, aged between 6 months and 10 years and weighing between 5.0 and 40.0 kg undergoing elective surgery.MethodsDogs were randomly allocated to two groups. Pre-anaesthetic medication in group M+ was intramuscular acepromazine (ACP) 25 μg kg⁻¹, morphine 0.5 mg kg⁻¹ and medetomidine 5 μg kg⁻¹. Group M− received ACP and morphine only, at the same dose rate. After induction with thiopental, anaesthesia was maintained with halothane in oxygen and nitrous oxide. End-tidal halothane concentration was maintained at 1.1%. Neuromuscular blockade was produced with intravenous vecuronium (50 μg kg⁻¹) and monitored using a train of four stimulus applied at the ulnar nerve. The times taken for loss and reappearance of the four evoked responses (twitches [T]) were recorded. Normal and nonparametric data were analysed with an independent t-test and Mann-Whitney's U-test, respectively.ResultsThe fourth twitch (T4) disappeared at similar times in each group: 107 ± 19; [72–132] (mean ± SD; [range]) seconds in M+ and 98 ± 17 [72–120] seconds in M− dogs. The first twitch (T1) was lost at 116 ± 15; [96–132] seconds in group M+ and 109 ± 19; [72–132] seconds in M−. The fourth twitch returned significantly earlier in M+ dogs: 20.8 ± 3.8 [14–28] minutes compared with 23.8 ± 2.7 [20–27] minutes (p = 0.032). The duration of drug effect (T4 absent) was significantly shorter (p = 0.027) in M+ (18.9 ± 3.7 minutes) compared with M− dogs (22.2 ± 2.9 minutes). The recovery rate (interval between reappearance of T1 and T4) was significantly more rapid (p = 0.0003) in medetomidine recipients (3.0 ± 1.2 versus 5.2 ± 1.3 minutes).Conclusion and clinical relevance Medetomidine 5 μg kg⁻¹ as pre-anaesthetic medication shortened the duration of effect of vecuronium in halothane-anaesthetized dogs and accelerated recovery, but did not affect the onset time. These changes are of limited clinical significance.     

Ketamine–propofol for total intravenous anaesthesia in rabbits: a comparison of premedication with acepromazine–medetomidine,acepromazine–midazolam or acepromazine–morphine

ObjectiveTo describe ketamine–propofol total intravenous anaesthesia (TIVA) following premedication with acepromazine and either medetomidine, midazolam or morphine in rabbits.Study designRandomized, crossover experimental study.AnimalsA total of six healthy female New Zealand White rabbits (2.2 ± 0.3 kg).MethodsRabbits were anaesthetized on four occasions, each separated by 7 days: an intramuscular injection of saline alone (treatment Saline) or acepromazine (0.5 mg kg^–1) in combination with medetomidine (0.1 mg kg^–1), midazolam (1 mg kg^–1) or morphine (1 mg kg^–1), treatments AME, AMI or AMO, respectively, in random order. Anaesthesia was induced and maintained with a mixture containing ketamine (5 mg mL^–1) and propofol (5 mg mL^–1) (ketofol). Each trachea was intubated and the rabbit administered oxygen during spontaneous ventilation. Ketofol infusion rate was initially 0.4 mg kg^–1 minute^–1 (0.2 mg kg^–1 minute^–1 of each drug) and was adjusted to maintain adequate anaesthetic depth based on clinical assessment. Ketofol dose and physiological variables were recorded every 5 minutes. Quality of sedation, intubation and recovery times were recorded.ResultsKetofol induction doses decreased significantly in treatments AME (7.9 ± 2.3) and AMI (8.9 ± 4.0) compared with treatment Saline (16.8 ± 3.2 mg kg^–1) (p < 0.05). The total ketofol dose to maintain anaesthesia was significantly lower in treatments AME, AMI and AMO (0.6 ± 0.1, 0.6 ± 0.2 and 0.6 ± 0.1 mg kg^–1 minute^–1, respectively) than in treatment Saline (1.2 ± 0.2 mg kg^–1 minute^–1) (p < 0.05). Cardiovascular variables remained at clinically acceptable values, but all treatments caused some degree of hypoventilation.Conclusions and clinical relevancePremedication with AME, AMI and AMO, at the doses studied, significantly decreased the maintenance dose of ketofol infusion in rabbits. Ketofol was determined to be a clinically acceptable combination for TIVA in premedicated rabbits.     

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.     

Effects of intravenous lidocaine, ketamine, and the combination on the minimum alveolar concentration of sevoflurane in dogs

ObjectiveTo evaluate the effects of intravenous lidocaine (L) and ketamine (K) alone and their combination (LK) on the minimum alveolar concentration (MAC) of sevoflurane (SEVO) in dogs.Study designProspective randomized, Latin-square experimental study.AnimalsSix, healthy, adult Beagles, 2 males, 4 females, weighing 7.8 – 12.8 kg.MethodsAnesthesia was induced with SEVO in oxygen delivered by face mask. The tracheas were intubated and the lungs ventilated to maintain normocapnia. Baseline minimum alveolar concentration of SEVO (MAC_B) was determined in duplicate for each dog using an electrical stimulus and then the treatment was initiated. Each dog received each of the following treatments, intravenously as a loading dose (LD) followed by a constant rate infusion (CRI): lidocaine (LD 2 mg kg⁻¹, CRI 50 μg kg⁻¹minute⁻¹), lidocaine (LD 2 mg kg⁻¹, CRI 100 μgkg⁻¹ minute⁻¹), lidocaine (LD 2 mg kg⁻¹, CRI 200 μg kg⁻¹ minute⁻¹), ketamine (LD 3 mg kg⁻¹, CRI 50 μg kg⁻¹ minute⁻¹), ketamine (LD 3 mgkg⁻¹, CRI 100 μg kg⁻¹ minute⁻¹), or lidocaine (LD 2 mg kg⁻¹, CRI 100 μg kg⁻¹ minute⁻¹) + ketamine (LD 3 mg kg⁻¹, CRI 100 μg kg⁻¹ minute⁻¹) in combination. Post-treatment MAC (MAC_T) determination started 30 minutes after initiation of treatment.ResultsLeast squares mean ± SEM MAC_B of all groups was 1.9 ± 0.2%. Lidocaine infusions of 50, 100, and 200 μg kg⁻¹ minute⁻¹ significantly reduced MAC_B by 22.6%, 29.0%, and 39.6%, respectively. Ketamine infusions of 50 and 100 μg kg⁻¹ minute⁻¹ significantly reduced MAC_B by 40.0% and 44.7%, respectively. The combination of K and L significantly reduced MAC_B by 62.8%.Conclusions and clinical relevanceLidocaine and K, alone and in combination, decrease SEVO MAC in dogs. Their use, at the doses studied, provides a clinically important reduction in the concentration of SEVO during anesthesia in dogs.     

Anaesthetic and cardiorespiratory effects of a constant rate infusion of fentanyl in isoflurane‐anaesthetized sheep

ObjectiveTo determine the anaesthetic and cardiorespiratory effects of a constant rate infusion of fentanyl in sheep anaesthetized with isoflurane and undergoing orthopaedic surgery.Study designProspective, randomised, ‘blinded’ controlled study.AnimalsTwenty healthy sheep (weight mean 41.1 ± SD 4.5 kg).MethodsSheep were sedated with intravenous (IV) dexmedetomidine (4 μg kg⁻¹) and morphine (0.2 mg kg⁻¹). Anaesthesia was induced with propofol (1 mg kg⁻¹ minute⁻¹ to effect IV) and maintained with isoflurane in oxygen and a continuous rate infusion (CRI) of fentanyl 10 μg kg⁻¹ hour⁻¹ (group F) or saline (group P) for 100 minutes. The anaesthetic induction dose of propofol, isoflurane expiratory fraction (Fe’iso) required for maintenance and cardiorespiratory measurements were recorded and blood gases analyzed at predetermined intervals. The quality of recovery was assessed. Results were compared between groups using t-tests or Mann–Whitney as relevant.ResultsThe propofol induction dose was 4.7 ± 2.4 mg kg⁻¹. Fe’iso was significantly lower (by 22.6%) in group F sheep than group P (p = 0). Cardiac index (mean ± SD mL kg⁻¹ minute⁻¹) was significantly (p = 0.012) lower in group F (90 ± 15) than group P (102 ± 35). Other measured cardiorespiratory parameters did not differ statistically significantly between groups. Recovery times and recovery quality were statistically similar in both groups.Conclusions and clinical relevanceFentanyl reduced isoflurane requirements without clinically affecting the cardiorespiratory stability or post-operative recovery in anaesthetized sheep undergoing orthopaedic surgery.     

Systemic lidocaine infusion as an analgesic for intraocular surgery in dogs: a pilot study

Objective To determine if systemic administration of lidocaine during intraocular surgery reduces post-operative ocular pain. Study design Randomized, masked, controlled experimental trial. Animals Twelve dogs weighing 15.5 ± 1.7 kg (mean ± SD) and aged 2.5 ± 0.6 years. Methods All dogs underwent a baseline ophthalmic examination and subjective pain score. Anesthesia consisted of acepromazine (0.1 mg kg⁻¹, IM), propofol (4–6 mg kg⁻¹, IV), and isoflurane in oxygen. There were three groups each receiving a bolus followed by an infusion (n = 4): saline (0.3 mL kg⁻¹ IV + 0.2 mL kg⁻¹hour⁻¹ IV); morphine (0.15 mg kg⁻¹ IV + 0.1 mg kg⁻¹hour⁻¹ IV); and lidocaine (1.0 mg kg⁻¹ IV + 0.025 mg kg⁻¹minute⁻¹ IV). All treatments began 15 minutes prior to starting of phacoemulsification and lens removal from the right eye. Pain scores were recorded at 0.5, 1, 2, 3, 4, 6, 8, 16, and 24 hours after t = 0 (extubation). Rescue morphine was administered (1.0 mg kg⁻¹ IM) if the subjective pain score ≥9 (maximum = 24), and the dog was excluded from further data analysis. Differences in pain scores and time-to-treatment failure (TTF) were analyzed using the Wilcoxon's rank sum test. Differences in incidence of treatment failure were analyzed using Fisher's exact test. Physiologic data were analyzed using repeated measures anova . Significance was defined as P < 0.05. Results Incidence of treatment failure was 100% in saline-treated dogs and 50% in morphine- or lidocaine-treated dogs. There was no difference in intraocular pressure, aqueous flare, cell count (or protein) between groups in the operated eye at any time following extubation. Conclusion and clinical relevance This pilot study suggests that intraoperative lidocaine may provide analgesic benefits similar to morphine for intraocular surgery in dogs, but more definitive research is needed. This model appears to be appropriate for pain assessment studies as the negative control group demonstrated 100% failure rate.