THE EFFECT OF A COMBINATION OF MEDETOMIDINE-BUTORPHANOL AND MEDETOMIDINE, BUTORPHANOL, ATROPINE ON GLOMERULAR FILTRATION RATE IN DOGS

The effects of intramuscularly administered medetomidine and butorphanol (MB), and medetomidine, butorphanol, atropine (MBA) on glomerular filtration rate (GFR) were determined in six dogs as measured by 99m-Tc-labeled diethylenetriaminepentaacetic acid (99mTc-DTPA) nuclear scintigraphy. Direct systolic, diastolic, and mean arterial blood pressures and heart rate were measured at regular time intervals before, during, and after GFR calculations. The mean GFR measurement following MB was significantly greater (4.44 ml/min/kg) than following MBA (3.82 ml/min/kg) or saline treatment (3.41 ml/min/kg). There was no significant difference between the mean GFR measurements following MBA injection and following saline injection. Diastolic and mean arterial pressures following MBA injection were significantly higher than the values recorded after either MB or saline alone. Heart rate following MB administration was significantly lower than that recorded for dogs receiving MBA or saline alone. The results of this study indicate that the administration of medetomidine in combination with butorphanol significantly increases total GFR in healthy dogs, while the administration of the combination of medetomidine, butorphanol, and atropine does not.     

Immobilization,cardiopulmonary and blood gas effects of ketamine–butorphanol–medetomidine versus butorphanol–midazolam–medetomidine in free-ranging serval (Leptailurus serval)

ObjectiveTo compare ketamine–butorphanol–medetomidine (KBM) with butorphanol–midazolam–medetomidine (BMM) immobilization of serval.Study designBlinded, randomized trial.AnimalsA total of 23 captures [KBM: five females, six males; 10.7 kg (mean); BMM: 10 females, two males; 9.6 kg].MethodsServal were cage trapped and immobilized using the assigned drug combination delivered via a blow dart into gluteal muscles. Prior to darting, a stress score was assigned (0: calm; to 3: markedly stressed). Drug combinations were dosed based on estimated body weights: 8.0, 0.4 and 0.08 mg kg^–1 for KBM and 0.4, 0.3 and 0.08 mg kg^–1 for BMM, respectively. Time to first handling, duration of anaesthesia and recovery times were recorded. Physiological variables including blood glucose and body temperature were recorded at 5 minute intervals. Atipamezole (5 mg mg^–1 medetomidine) and naltrexone (2 mg mg^–1 butorphanol) were administered intramuscularly prior to recovery. Data, presented as mean values, were analysed using general linear mixed model and Spearman’s correlation (stress score, glucose, temperature); significance was p < 0.05.ResultsDoses based on actual body weights were 8.7, 0.4 and 0.09 mg kg^–1 for KBM and 0.5, 0.4 and 0.09 mg kg^–1 for BMM, respectively. Time to first handling was 10.2 and 13.3 minutes for KBM and BMM, respectively (p = 0.033). Both combinations provided cardiovascular stability during anaesthesia that lasted a minimum of 35 minutes. Recovery was rapid and calm overall, but ataxia was noted in KBM. Stress score was strongly correlated to blood glucose (r² = 0.788; p = 0.001) and temperature (r² = 0.634; p = 0.015).Conclusions and clinical relevanceBoth combinations produced similar effective immobilization that was cardiovascularly stable in serval. Overall, BMM is recommended because it is fully antagonizable. A calm, quiet environment before drug administration is essential to avoid capture-induced hyperglycaemia and hyperthermia.     

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.     

Sedative and analgesic effects of medetomidine in beagle dogs infected and uninfected with heartworm

The sedative and analgesic effects of medetomidine were evaluated in heartworm-infected (HW+) and uninfected (HW–) beagle dogs by intravenous (IV) and intramuscular (IM) administration of 30 µg/kg and 40 µg/kg doses, respectively. Posture, response to noise and the pedal reflex were monitored. A procedure for mock radiographic positioning was performed to evaluate its overall clinical use. Observation times were 0, 15, 30, 60, 90, 120 and 180 min. In addition, the times from injection until the dog could not stand on its feet (down time), from lateral to sternal recumbency (sternal recumbency time), and from sternal recumbency to rising again (rising time) were also noted.Medetomidine produced rapid sedation and analgesia by both routes. Down times for the IM and IV routes were similar, which verified the manufacturer's recommended doses. The HW+ dogs had shorter down times, probably owing to increased blood flow to the brain caused by adrenergic alpha-2 activity. Sternal recumbency and rising times did not differ between the groups, suggesting a similar metabolism. Sedation and analgesia were adequate for performing the procedure in all dogs. HW– dogs showed less resistance to handling during the procedure than HW+ dogs. Overall, medetomidine seems to be a suitable agent for short-term chemical restraint in dogs, even with subclinical heartworm infestation.     

A comparison in dogs of medetomidine,with or without MK‐467, and the combination acepromazine‐butorphanol as premedication prior to anaesthesia induced by propofol and maintained with isoflurane

ObjectiveTo compare the haemodynamic effects of three premedicant regimens during propofol-induced isoflurane anaesthesia.Study designProspective, randomized cross-over study.AnimalsEight healthy purpose-bred beagles aged 4 years and weighing mean 13.6 ± SD 1.9 kg.MethodsThe dogs were instrumented whilst under isoflurane anaesthesia prior to each experiment, then allowed to recover for 60 minutes. Each dog was treated with three different premedications given intravenously (IV): medetomidine 10 μg kg^?1 (MED), medetomidine 10 μg kg^?1 with MK-467 250 μg kg^?1 (MMK), or acepromazine 0.01 mg kg^?1 with butorphanol 0.3 mg kg^?1 (AB). Anaesthesia was induced 20 minutes later with propofol and maintained with isoflurane in oxygen for 60 minutes. Heart rate (HR), cardiac output, arterial blood pressures (ABP), central venous pressure (CVP), respiratory rate, inspired oxygen fraction, rectal temperature (RT) and bispectral index (BIS) were measured and arterial and venous blood gases analyzed. Cardiac index (CI), systemic vascular resistance index (SVRI), oxygen delivery index (DO₂I), systemic oxygen consumption index (VO₂I) and oxygen extraction (EO₂) were calculated. Times to extubation, righting, sternal recumbency and walking were recorded. The differences between treatment groups were evaluated with repeated measures analysis of covariance.ResultsHR, CI, DO₂I and BIS were significantly lower with MED than with MMK. ABP, CVP, SVRI, EO₂, RT and arterial lactate were significantly higher with MED than with MMK and AB. HR and ABP were significantly higher with MMK than with AB. However, CVP, CI, SVRI, DO₂I, VO₂I, EO₂, T, BIS and blood lactate did not differ significantly between MMK and AB. The times to extubation, righting, sternal recumbency and walking were significantly shorter with MMK than with MED and AB.Conclusions and clinical relevanceMK-467 attenuates certain cardiovascular effects of medetomidine in dogs anaesthetized with isoflurane. The cardiovascular effects of MMK are very similar to those of AB.     

Hyoscine‐N‐butylbromide premedication on cardiovascular variables of horses sedated with medetomidine

ObjectiveTo evaluate the effects of intravenous (IV) or intramuscular (IM) hyoscine premedication on physiologic variables following IV administration of medetomidine in horses.Study designRandomized, crossover experimental study.AnimalsEight healthy crossbred horses weighing 330 ± 39 kg and aged 7 ± 4 years.MethodsBaseline measurements of heart rate (HR), cardiac index (CI), respiratory rate, systemic vascular resistance (SVR), percentage of patients with second degree atrioventricular (2^oAV) block, mean arterial pressure (MAP), pH, and arterial partial pressures of carbon dioxide (PaCO₂) and oxygen (PaO₂) were obtained 5 minutes before administration of IV hyoscine (0.14 mg kg^?1; group HIV), IM hyoscine (0.3 mg kg^?1; group HIM), or an equal volume of physiologic saline IV (group C). Five minutes later, medetomidine (7.5 μg kg^?1) was administered IV and measurements were recorded at various time points for 130 minutes.ResultsMedetomidine induced bradycardia, 2^oAV blocks and increased SVR immediately after administration, without significant changes in CI or MAP in C. Hyoscine administration induced tachycardia and hypertension, and decreased the percentage of 2^oAV blocks induced by medetomidine. Peak HR and MAP were higher in HIV than HIM at 88 ± 18 beats minute^?1 and 241 ± 37 mmHg versus 65 ± 16 beats minute^?1 and 192 ± 38 mmHg, respectively. CI was increased significantly in HIV (p ≤ 0.05). Respiratory rate decreased significantly in all groups during the recording period. pH, PaCO₂ and PaO₂ were not significantly changed by administration of medetomidine with or without hyoscine.Conclusion and clinical relevanceHyoscine administered IV or IM before medetomidine in horses resulted in tachycardia and hypertension under the conditions of this study. The significance of these changes, and responses to other dose rates, requires further investigation.     

A clinical study on the effect in horses during medetomidine-isoflurane anaesthesia, of butorphanol constant rate infusion on isoflurane requirements, on cardiopulmonary function and on recovery characteristics

ObjectiveTo test if the addition of butorphanol by constant rate infusion (CRI) to medetomidine–isoflurane anaesthesia reduced isoflurane requirements, and influenced cardiopulmonary function and/or recovery characteristics.Study designProspective blinded randomised clinical trial.Animals61 horses undergoing elective surgery.MethodsHorses were sedated with intravenous (IV) medetomidine (7 μg kg^?1); anaesthesia was induced with IV ketamine (2.2 mg kg^?1) and diazepam (0.02 mg kg^?1) and maintained with isoflurane and a CRI of medetomidine (3.5 μg kg^?1 hour^?1). Group MB (n = 31) received butorphanol CRI (25 μg kg^?1 IV bolus then 25 μg kg^?1 hour^?1); Group M (n = 30) an equal volume of saline. Artificial ventilation maintained end-tidal CO₂ in the normal range. Horses received lactated Ringer’s solution 5 mL kg^?1 hour^?1, dobutamine <1.25 μg kg^?1 minute^?1 and colloids if required. Inspired and exhaled gases, heart rate and mean arterial blood pressure (MAP) were monitored continuously; pH and arterial blood gases were measured every 30 minutes. Recovery was timed and scored. Data were analyzed using two way repeated measures anova, independent t-tests or Mann–Whitney Rank Sum test (p < 0.05).ResultsThere was no difference between groups with respect to anaesthesia duration, end-tidal isoflurane (MB: mean 1.06 ± SD 0.11, M: 1.05 ± 0.1%), MAP (MB: 88 ± 9, M: 87 ± 7 mmHg), heart rate (MB: 33 ± 6, M: 35 ± 8 beats minute^?1), pH, PaO₂ (MB: 19.2 ± 6.6, M: 18.2 ± 6.6 kPa) or PaCO_2. Recovery times and quality did not differ between groups, but the time to extubation was significantly longer in group MB (26.9 ± 10.9 minutes) than in group M (20.4 ± 9.4 minutes).Conclusion and clinical relevanceButorphanol CRI at the dose used does not decrease isoflurane requirements in horses anaesthetised with medetomidine–isoflurane and has no influence on cardiopulmonary function or recovery.     

Assessment of ketamine/medetomidine anaesthesia in the New Zealand White rabbit

Objective To compare the characteristics of anaesthesia induced with four dose combinations of ketamine/medetomidine. Design Prospective randomized study. Animals Five female New Zealand White (NZW) rabbits of approximately 2.3 kg. Methods Rabbits were given one of four drug combinations (25/0.25; 15/0.5; 15/0.25 and 10/0.5 mg kg^?1 IM) on four successive occasions with a four day interval. Response to injection and then arterial blood gas and cardiovascular parameters were recorded at predetermined time points. Toe and ear pinch reflexes gave measures of total duration of surgical anaesthesia and total sleep time. Analyses used repeated measures analysis of variance. Results Induction was smooth with little reaction to injection and intubation achieved easily. Two combinations (15/0.25, 10/0.5) produced moderate hypoxaemia (mean pO₂ < 8.0 kPa) and two (25/0.25, 15/0.5) very marked hypoxaemia (mean pO₂ < 5.3 kPa). This was reversed within 15 minutes of oxygen administration and all rabbits recovered uneventfully. Heart rates fell in all cases, with only minimal effects on arterial blood pressure and no cardiac arrhythmias. Mean duration of surgical anaesthesia was significantly longer for dose groups 25/0.25 (57 ± 12 minutes) and 15/0.5 (59 ± 17 minutes, p = 0.01) compared to dose group 15/0.25 (27 ± 8 minutes). Only three animals in the 10/0.5 mg kg^?1 group achieved surgical anaesthesia. Mean duration of loss of the ear pinch reflex was similar between doses, being, respectively, 64 ± 13, 81 ± 7, 60 ± 22 and 62 ± 24 minutes. Sleep time was significantly longer for the 15/0.5 dose (112 ± 10 minutes) compared to 15/0.25 (86 ± 22 minutes, p = 0.04). Sleep times for the 25/0.25 and 10/0.5 mg kg^?1 doses were, respectively, 103 ± 23 and 108 ± 12 minutes. Conclusions Ketamine/medetomidine reliably produces smooth induction and recovery in the NZW rabbit, but due to the degree of hypoxaemia produced, should only be used with simultaneous provision of oxygen. Clinical relevance Currently recommended dose rates of ketamine/medetomidine for minor procedures such as ovariohysterectomy in rabbits (25 mg/0.5 mg kg^?1) are unnecessarily high; a dose of 15/0.25 mg kg^?1 should be adequate for 15–30 minutes of surgical anaesthesia.     

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.