Minimum infusion rate of alfaxalone for total intravenous anaesthesia after sedation with acepromazine or medetomidine in cats undergoing ovariohysterectomy

ObjectiveTo determine the induction doses, then minimum infusion rates of alfaxalone for total intravenous anaesthesia (TIVA), and subsequent, cardiopulmonary effects, recovery characteristics and alfaxalone plasma concentrations in cats undergoing ovariohysterectomy after premedication with butorphanol-acepromazine or butorphanol-medetomidine.Study designProspective randomized blinded clinical study.AnimalsTwenty-eight healthy cats.MethodsCats undergoing ovariohysterectomy were assigned into two groups: together with butorphanol [0.2 mg kg^?1 intramuscularly (IM)], group AA (n = 14) received acepromazine (0.1 mg kg^?1 IM) and group MA (n = 14) medetomidine (20 μg kg^?1 IM). Anaesthesia was induced with alfaxalone to effect [0.2 mg kg^?1 intravenously (IV) every 20 seconds], initially maintained with 8 mg kg^?1 hour^?1 alfaxalone IV and infusion adjusted (±0.5 mg kg^?1 hour^?1) every five minutes according to alterations in heart rate (HR), respiratory rate (f_R), Doppler blood pressure (DBP) and presence of palpebral reflex. Additional alfaxalone boli were administered IV if cats moved/swallowed (0.5 mg kg^?1) or if f_R >40 breaths minute^?1 (0.25 mg kg^?1). Venous blood samples were obtained to determine plasma alfaxalone concentrations. Meloxicam (0.2 mg kg^?1 IV) was administered postoperatively. Data were analysed using linear mixed models, Chi-squared, Fishers exact and t-tests.ResultsAlfaxalone anaesthesia induction dose (mean ± SD), was lower in group MA (1.87 ± 0.5; group AA: 2.57 ± 0.41 mg kg^?1). No cats became apnoeic. Intraoperative bolus requirements and TIVA rates (group AA: 11.62 ± 1.37, group MA: 10.76 ± 0.96 mg kg^?1 hour^?1) did not differ significantly between groups. Plasma concentrations ranged between 0.69 and 10.76 μg mL^?1. In group MA, f_R, end-tidal carbon dioxide, temperature and DBP were significantly higher and HR lower.Conclusion and clinical relevanceAlfaxalone TIVA in cats after medetomidine or acepromazine sedation provided suitable anaesthesia with no need for ventilatory support. After these premedications, the authors recommend initial alfaxalone TIVA rates of 10 mg kg^?1 hour^?1.     

Pharmacokinetic and pharmacodynamic modelling of intravenous,intramuscular and subcutaneous buprenorphine in conscious cats

ObjectiveTo describe simultaneous pharmacokinetics (PK) and thermal antinociception after intravenous (IV), intramuscular (IM) and subcutaneous (SC) buprenorphine in cats.Study designRandomized, prospective, blinded, three period crossover experiment.AnimalsSix healthy adult cats weighing 4.1 ± 0.5 kg.MethodsBuprenorphine (0.02 mg kg^?1) was administered IV, IM or SC. Thermal threshold (TT) testing and blood collection were conducted simultaneously at baseline and at predetermined time points up to 24 hours after administration. Buprenorphine plasma concentrations were determined by liquid chromatography tandem mass spectrometry. TT was analyzed using anova (p < 0.05). A pharmacokinetic-pharmacodynamic (PK-PD) model of the IV data was described using a model combining biophase equilibration and receptor association-dissociation kinetics.ResultsTT increased above baseline from 15 to 480 minutes and at 30 and 60 minutes after IV and IM administration, respectively (p < 0.05). Maximum increase in TT (mean ± SD) was 9.3 ± 4.9 °C at 60 minutes (IV), 4.6 ± 2.8 °C at 45 minutes (IM) and 1.9 ± 1.9 °C at 60 minutes (SC). TT was significantly higher at 15, 60, 120 and 180 minutes, and at 15, 30, 45, 60 and 120 minutes after IV administration compared to IM and SC, respectively. IV and IM buprenorphine concentration-time data decreased curvilinearly. SC PK could not be modeled due to erratic absorption and disposition. IV buprenorphine disposition was similar to published data. The PK-PD model showed an onset delay mainly attributable to slow biophase equilibration (t_1/2k_e0 = 47.4 minutes) and receptor binding (k_on = 0.011 mL ng^?1 minute^?1). Persistence of thermal antinociception was due to slow receptor dissociation (t_1/2k_off = 18.2 minutes).Conclusions and clinical relevanceIV and IM data followed classical disposition and elimination in most cats. Plasma concentrations after IV administration were associated with antinociceptive effect in a PK-PD model including negative hysteresis. At the doses administered, the IV route should be preferred over the IM and SC routes when buprenorphine is administered to cats.     

A study to evaluate buprenorphine at 40 μg kg(-1) compared to 20 μg kg(-1) as a post-operative analgesic in the dog

ObjectiveComparison of the analgesic effect of buprenorphine at 20 or 40 μg kg^?1.Study designAn investigator ‘blinded’, randomised study.AnimalsTwenty six dogs presented for ovariohysterectomy.MethodsDogs were premedicated intramuscularly with acepromazine 0.03 mg kg^?1 and buprenorphine at either 20 (B20, n = 12) or 40 μg kg^?1 (B40, n= 14) followed by anaesthetic induction with propofol and maintenance with isoflurane. During anaesthesia non invasive blood pressure, heart rate, respiratory rate, blood oxygen saturation, inspired and expired volatile agent, end-tidal carbon dioxide and ECG were recorded. Pain and sedation were assessed using interactive VAS scores; mechanical nociceptive thresholds were measured at the wound and hindlimb - all were assessed before and up to 22 hours after administration. Carprofen was used for rescue analgesia.ResultsThere were no significant differences between the two groups for any of the parameters examined. Rescue analgesia was required around 5 hours after administration of buprenorphine in a significant number of animals. Sedation was good preoperatively and scores decreased over time postoperatively. Hock thresholds did not change over time; wound thresholds decreased significantly compared to the baseline value from 3 hours onwards.ConclusionsAdministration of buprenorphine at either 20 or 40 μg kg^?1 IM with acepromazine provided good pre-operative sedation. Cardiovascular and respiratory values remained within clinically acceptable limits during anaesthesia. There was no evidence that increasing dose increased adverse events that may be associated with opioid administration (e.g. bradycardia and respiratory depression).Clinical relevanceIncreasing the dose of buprenorphine from 20 to 40 μg kg^?1 did not provide any benefits with respect to analgesia after ovariohysterectomy as assessed using the VAS scoring system.     

Effects of opioids and anesthetic drugs on body temperature in cats

ObjectiveTo determine which class of opioid alone or in conjunction with other anesthetic drugs causes post-anesthetic hyperthermia in cats.Study designProspective, randomized, crossover study.AnimalsEight adult, healthy, cats (four spayed females and four castrated males weighing 3.8 ± 0.6 kg).MethodsEach cat was instrumented with a wireless thermistor in the abdominal cavity. Temperature in all phases was recorded every 5 minutes for 5 hours. Population body temperature (PBT) was recorded for ～8 days. Baseline body temperature is the final 24 hours of the PBT. All injectable drugs were given intramuscularly. The cats were administered drugs in four phases: 1) hydromorphone (H) 0.05, 0.1, or 0.2 mg kg^?1; 2) morphine (M) (0.5 mg kg^?1), buprenorphine (BUP) (0.02 mg kg^?1), or butorphanol (BUT) (0.2 mg kg^?1); 3) ketamine (K) (5 mg kg^?1) or ketamine (5 mg kg^?1) plus hydromorphone (0.1 mg kg^?1) (KH); 4) isoflurane in oxygen for 1 hour. Fifteen minutes prior to inhalant anesthetic, cats received either no premed (I), hydromorphone (0.1 mg kg^?1) (IH), or hydromorphone (0.1 mg kg^?1) plus ketamine (5 mg kg^?1) (IHK).ResultsMean PBT for all unmedicated cats was 38.9 ± 0.6 °C (102.0 ± 1 °F). The temperature of cats administered all doses of hydromorphone increased from baseline (p < 0.03) All four opioids (H, M, BUP and BUT) studied increased body temperature compared with baseline (p < 0.005). A significant difference was observed between baseline temperature values and those in treatment KH (p < 0.03). Following recovery from anesthesia, temperature in treatments IH and IHK was different from baseline (p < 0.002).Conclusions and clinical relevanceAll of the opioids tested, alone or in combination with ketamine or isoflurane, caused an increase in body temperature. The increase seen was mild to moderate (<40.1 °C (104.2 °F) and self limiting.     

Alfaxalone or ketamine‐medetomidine in cats undergoing ovariohysterectomy: a comparison of intra‐operative parameters and post‐operative pain

ObjectiveTo compare post-operative pain in cats after alfaxalone or ketamine- medetomidine anaesthesia for ovariohysterectomy (OHE) and physiologic parameters during and after surgery.Study designProspective ‘blinded’ randomized clinical study.AnimalsTwenty-one healthy cats.MethodsCats were assigned randomly into two groups: Group A, anaesthesia was induced and maintained with alfaxalone [5 mg kg^?1 intravenously (IV) followed by boli (2 mg kg^?1 IV); Group MK, induction with ketamine (5 mg kg^?1 IV) after medetomidine (30 μg kg^?1 intramuscularly (IM)], and maintenance with ketamine (2 mg kg^?1 IV). Meloxicam (0.2 mg kg^?1 IV) was administered after surgery. Basic physiological data were collected. At time T = -2, 0, 0.5, 1, 2, 4, 6, 8, 12, 16, 20, and 24 hours post-operatively pain was assessed by three methods, a composite pain scale (CPS; 0–24 points), a visual analogue scale (VAS 0–100 mm), and a mechanical wound threshold (MWT) device. Butorphanol (0.2 mg kg^?1 IM) was administered if CPS was scored =13. Data were analyzed using a general linear model, Kruskal–Wallis analyses, Bonferroni-Dunn test, unpaired t-test and Fisher's exact test as relevant. Significance was set at p < 0.05.ResultsVASs were significantly higher at 0.5, 1, 2, 4, and 20 hours in group A; MWT values were significantly higher at 8 and 12 hours in group MK. Post-operative MWT decreased significantly compared to baseline in both groups. There was no difference in CPS at any time point. Five cats required rescue analgesia (four in A; one in MK).Conclusion and clinical relevanceAnaesthesia with ketamine-medetomidine was found to provide better post-surgical analgesia than alfaxalone in cats undergoing OHE; however, primary hyperalgesia developed in both groups. Alfaxalone is suitable for induction and maintenance of anaesthesia in cats undergoing OHE, but administration of additional sedative and analgesic drugs is highly recommended.     

Sedative and analgesic effects of buprenorphine,combined with either acepromazine or dexmedetomidine,for premedication prior to elective surgery in cats and dogs

ObjectiveTo evaluate the sedative and analgesic effects of intramuscular buprenorphine with either dexmedetomidine or acepromazine, administered as premedication to cats and dogs undergoing elective surgery.Study designProspective, randomized, blinded clinical study.AnimalsForty dogs and 48 cats.MethodsAnimals were assigned to one of four groups, according to anaesthetic premedication and induction agent: buprenorphine 20 μg kg^?1 with either dexmedetomidine (dex) 250 μg m^?2 or acepromazine (acp) 0.03 mg kg^?1, followed by alfaxalone (ALF) or propofol (PRO). Meloxicam was administered preoperatively to all animals and anaesthesia was always maintained using isoflurane. Physiological measures and assessments of pain, sedation and mechanical nociceptive threshold (MNT) were made before and after premedication, intraoperatively, and for up to 24 hours after premedication. Data were analyzed with one-way, two-way and mixed between-within subjects anova, Kruskall–Wallis analyses and Chi squared tests. Results were deemed significant if p ≤ 0.05, except where multiple comparisons were performed (p ≤ 0.005).ResultsCats premedicated with dex were more sedated than cats premedicated with acp (p < 0.001) and ALF doses were lower in dex cats (1.2 ± 1.0 mg kg^?1) than acp cats (2.5 ± 1.9 mg kg^?1) (p = 0.041). There were no differences in sedation in dogs however PRO doses were lower in dex dogs (1.5 ± 0.8 mg kg^?1) compared to acp dogs (3.3 ± 1.1 mg kg^?1) (p < 0.001). There were no differences between groups with respect to pain scores or MNT for cats or dogs.ConclusionChoice of dex or acp, when given with buprenorphine, caused minor, clinically detectable, differences in various characteristics of anaesthesia, but not in the level of analgesia.Clinical relevanceA combination of buprenorphine with either acp or dex, followed by either PRO or ALF, and then isoflurane, accompanied by an NSAID, was suitable for anaesthesia in dogs and cats undergoing elective surgery. Choice of sedative agent may influence dose of anaesthetic induction agent.     

Blood pressure and electrocardiographic effects of acepromazine in anaesthetized horses

Acepromazine, a phenothiazine tranquilizer, causes hypotension in standing horses ( Parry et al. 1982 ). However, a retrospective study ( Taylor & Young 1993 ) showed that acepromazine pre‐anesthetic medication did not affect arterial blood pressure (MAP) in anaesthetized horses. This study examined the effects of acepromazine on MAP during romifidine–ketamine–halothane anaesthesia in horses anaesthetized for various surgical procedures. Forty‐four horses were allocated by block randomization to groups A and B. Group A received acepromazine 0.05 mg kg^?1 IM 30 minutes before induction of anaesthesia, group B did not. All horses received romifidine 0.1 mg kg^?1 IV 5 minutes before anaesthesia was induced with diazepam 0.05 mg kg^?1 and 2.2 mg kg^?1 ketamine IV. The horses' trachea were intubated and horses breathed 50% oxygen and 50% nitrous oxide plus halothane (concentration adjusted as required clinically) from a circle breathing system. Nitrous oxide was discontinued after 10 minutes and analgesics, flunixin 1.1 mg kg^?1 and either morphine 0.1 mg kg^?1 or butorphanol 0.05 mg kg^?1 (matched for horses undergoing the same procedure) administered IV. The facial or dorsal metatarsal artery was catheterized for direct measurement of MAP (every 10 min) and withdrawal of blood for gas analysis (every 30 min). The electrocardiogram (ECG) was monitored continuously with a 10 seconds printout obtained every 10 minutes. Intermittent positive pressure ventilation (IPPV) was instigated if PaCO₂ exceeded 9.3 kPa (70 mm Hg). Dobutamine was infused (1.0–5.0 kg^?1minute^?1) if MAP < 58 mm Hg and was continued until MAP > 70 mm Hg. Mean age, weight and duration of anaesthesia were compared between the groups using a t‐test for independent samples. Gender distribution and numbers of horses requiring IPPV or dobutamine were compared between groups using a chi‐squared test (with Yates correction). To compare MAP over time, the area under the curve (MAPAUC) was calculated and compared between groups using a t‐test. Horses receiving dobutamine were excluded from MAPAUC and MAP comparisons. The ECG printouts were examined for arrhythmias. There were no significant differences between groups (p > 0.05). Group A contained three stallions, 10 geldings and nine mares, aged 6.3 years (range 0.75–18). Group B comprised eight stallions, 11 geldings and three mares aged 7.3(1–16) years. Duration of anaesthesia was group A 97 (50–140) minutes, group B 99 (50–160) minutes. Eight horses in group A and three in group B required IPPV. Nine horses in group A and four in group B received dobutamine. Mean arterial pressure ranged from 60 to 128 mm Hg in group A and 58–96 mm Hg in group B. Mean MAPAUC was 5941 mm Hg minute^?1 in group A, in B 6000 mm Hg minute^?1. Atrial pre‐mature complexes were recorded from one horse in group B. No other arrhythmias were detected. Although MAP was lower in the acepromazine group, this appeared unlikely to cause a clinical problem. The incidence of arrhythmias was too low to determine the influence of acepromazine in this study.     

The isoflurane sparing effect of a medetomidine constant rate infusion in horses

This clinical study analysed the anaesthetic sparing effect of a medetomidine constant rate infusion (CRI) during isoflurane anaesthesia in horses. Forty healthy horses undergoing different types of orthopaedic and soft tissue surgeries were studied in a randomized trial. Orthopaedic surgeries were primarily arthroscopies and splint bone extractions. Soft tissue surgeries were principally castrations with one ovariectomy. All horses received 0.03 mg kg^?1 acepromazine IM 1 hour prior to sedation. Group A (11 orthopaedic and nine soft tissue surgeries), was sedated with 1.1 mg kg^?1 xylazine IV, group B (13 orthopaedic and seven soft tissue surgeries) with 7 µg kg^?1 medetomidine IV. Anaesthesia was induced in both groups with 2.2 mg kg^?1 ketamine and diazepam 0.02 mg kg^?1 IV. Maintenance of anaesthesia was with isoflurane (ISO) in 100% oxygen, depth of anaesthesia was always adjusted by the first author. Group B received an additional CRI of 3.5 µg kg^?1 hour^?1 medetomidine. Respiratory rate (RR), heart rate (HR), mean arterial blood pressure (MAP), Fe ′ISO and Fe ′CO₂ were monitored with a methane insensitive monitor (Cardiocap 5, Ohmeda, Anandic, Diessenhofen) and noted every 5 minutes. Arterial blood was withdrawn for gas analysis (PaO₂, PaCO₂) 5 minutes after the induction of anaesthesia and every 30 minutes thereafter. Dobutamine (DOB) was given as a CRI to maintain mean arterial blood pressure above 70 mm Hg. Data were averaged over time (sum of measurements/number of measurements) and tested for differences between groups by unpaired t‐tests. There were no significant differences between the groups in terms of body mass (group A, 508 ± 73.7 kg; group B, 529.25 ± 78.4 kg) or duration of anaesthesia (group A, 125.5 ± 36 minutes; group B, 121.5 ± 48.4 minutes). The mean Fe ′ISO required to maintain a surgical plane of anaesthesia was significantly higher in group A (1.33 ± 0.13%) than in group B (1.07 ± 0.19%; p = 2.78 × 10^?5). Heart rate was different between the two groups (group A, 42.2 ± 8.3; group B, 32.6 ± 3.5; p = 8.8 × 10^?5). Dobutamine requirements were higher in group A (group A, 0.72 ± 0.24 μg kg^?1 minute^?1; group B, 0.53 ± 0.23 μg kg^?1 minute^?1; p = 0.023). Respiratory rate, Fe ′CO₂, PaO₂, PaCO₂ were not different between the groups. Adjustment of anaesthetic depth subjectively was easier with the medetomidine infusion and isoflurane (group B) than with isoflurane as a sole agent (group A). In group A 12 horses and in group B five horses showed purposeful movements on 27 (A) and 12 (B) occasions. They were given thiopental (group A, 0.0114 mg kg^?1 minute^?1; group B, 0.0023 mg kg^?1 minute^?1). In group A, a further 17 horses were given ketamine to deepen anaesthesia (52 occasions, 0.00426 mg kg^?1 minute^?1) whereas in group B only nine horses needed ketamine (34 occasions, 0.00179 mg kg^?1 minute^?1). An infusion of 3.5 µg kg^?1 MED during ISO anaesthesia resulted in a significantly reduced ISO requirement.     

Medetomidine/midazolam/ketamine anaesthesia in ferrets: effects on cardiorespiratory parameters and evaluation of plasma drug concentrations

ObjectiveTo evaluate the cardiorespiratory effects and plasma concentrations of medetomidine-midazolam-ketamine (MMK) combinations administered by intramuscular (IM) or subcutaneous (SC) injection in sable ferrets (Mustela putorius furo).Study designProspective randomized experimental study.AnimalsEighteen adult ferrets: weight median 1.19 (range 0.81–1.60) kg.MethodsAnimals were allocated to one of three groups: group IM07 received 20 μg kg^?1 medetomidine, 0.5 mg kg^?1 midazolam and 7 mg kg^?1 ketamine IM; group IM10 20 μg kg^?1 medetomidine, 0.5 mg kg^?1 midazolam and 10 mg kg^?1 ketamine IM; and group SC10 20 μg kg^?1 medetomidine, 0.5 mg kg^?1 midazolam and 10 mg kg^?1 ketamine SC. Following instrumentation, cardiorespiratory parameters and plasma drug concentrations were measured every 5 minutes (T5–T30) for 30 minutes Ferrets were then euthanased. Data were analysed using anova for repeated measures. p < 0.05 was considered significant.ResultsResults are mean ± SD. Induction of anaesthesia (minutes) in IM07 and IM10 [2 (1)] was significantly faster than in SC10 [5 (2)]. All groups demonstrated the following: results given as groups IM07, IM10 and SC10 respectively. Mean arterial blood pressures (mmHg) were initially high [186 (13); 174 (33) and 174 (9) at T5] but decreased steadily. Pulse rates were initially 202 (20), 213 (17) and 207 (33) beats minute^?1, decreasing with time. PaO₂ (mmHg) was low [54.0 (8), 47.7 (10) and 38.5 (1)] at T5, although in groups IM07 and IM10 it increased over time. Plasma concentrations of all drugs were highest at T5 (36, 794 and 8264 nmol L^?1 for medetomidine, midazolam and ketamine, respectively) and decreased thereafter: for both midazolam and ketamine, concentrations in IM07 and IM10 were higher than SC10.Conclusions and clinical relevanceMMK combinations containing either 7 or 10 mg kg^?1 ketamine and given IM are suitable combinations for anaesthetising ferrets, although the observed degree of hypoxaemia indicates that oxygen administration is vital.     

Anaesthetic,analgesic and cardiorespiratory effects of intramuscular medetomidine‐ketamine combination alone or with morphine or tramadol for orchiectomy in cats

ObjectivesTo compare the anaesthetic, analgesic and cardiorespiratory effects of intramuscular (IM) medetomidine and ketamine administered alone or combined with morphine or tramadol, for orchiectomy in cats.Study designRandomised, blinded, prospective clinical study.AnimalsThirty client-owned cats.Materials and methodsCats (n = 10 in each group) received a combination of medetomidine (60 μgkg^?1) and ketamine (10 mg kg^?1) alone (MedK); combined with morphine (0.2 mg kg^?1) (MedKM), or combined with tramadol (2 mg kg^?1) (MedKT) IM. Time of induction, surgical and recovery events were recorded, and physiological parameters measured and recorded. Analgesia was evaluated with a visual analogue scale, a composite scoring system and the von Frey mechanical threshold device, every hour from three to eight hours post-drug administration injection. Data were analyzed with a linear mixed model, Kruskal–Wallis or Chi-square tests (p < 0.05).ResultsMedian (IQR) induction and recovery times (minutes) were not significantly (p = 0.125) different between groups: 5.6 (2.7–8.0), 7.4 (5.1–9.6) and 8.0 (5.8–14.9) for induction and 128.5 (95.1–142.8), 166.4 (123.1–210.0) and 142.9 (123.4–180.2) for recovery, with MedK, MedKT and MedKM, respectively. Two cats (MedKM) required alfaxalone for endotracheal intubation. In all groups, three or four cats required additional isoflurane for surgery. Arterial oxygen tension overall (mean ± SD: 66 ± 2 mmHg) was low. Surgery resulted in increased systolic arterial blood pressure (p < 0.001), haemoglobin saturation (p < 0.001), respiratory (p = 0.003) and heart rates (p = 0.002). Pain scores did not differ significantly between groups. Von Frey responses decreased over time; changes over time varied by treatment (p < 0.001), MedK returning to baseline values more rapidly than MedKM and MedKT. No cat required rescue analgesics.Conclusion and clinical relevanceAll three protocols can provide adequate anaesthesia and analgesia for orchiectomy in cats. However, rescue intervention to maintain surgical anaesthesia may be required in some cats. Oxygen supplementation is advised.     

Acepromazine‐dexmedetomidine‐ketamine for injectable anaesthesia in captive European brown hares (Lepus europaeus)

ObjectiveTo evaluate a combination of acepromazine, dexmedetomidine and ketamine (ADK) on induction and recovery from anaesthesia, and on physiological parameters in hares undergoing non‐invasive procedures.Study designProspective clinical study.AnimalsSixteen European hares (Lepus europaeus), seven males and nine females, aged (mean ± SD) 3.25 ± 0.9 months and weight 2.1 ± 0.6 kg.MethodsAcepromazine 1% (A), dexmedetomidine 0.05% (D) and ketamine 5% (K) were mixed and given intramuscularly (IM) at 0.25 mL kg^?1, representing 10 mg kg^?1 K, 0.25 mg kg^?1 A, 12.5 μg kg^?1 D. If the righting reflex was present after four minutes, a second injection of 0.15 mL kg^?1 (6 mg kg^?1 K, 0.15 mg kg^?1 A, 7.5 μg kg^?1 D) was administered IM. Surgical anaesthesia was judged as present when righting, palpebral, ear‐pinch and pedal withdrawal reflexes were absent. Anaesthetized hares were tagged, and underwent blood sampling and ocular ultrasound examination. Physiological parameters were recorded every ten minutes, and were compared by Kruskal‐Wallis tests.ResultsA single dose induced loss of righting reflex in 11/16 (69%) hares within four minutes; the second dose was effective in the remaining hares. Ten minutes after the loss of the righting reflex, a surgical plane of anaesthesia was present in all hares. Sleep time to regaining righting reflex was 34 ± 11 (range 21–62) minutes and recovery was calm. Although there were some statistical differences over time, cardiovascular parameters remained within an acceptable range but there was respiratory depression and hares were hypoxemic.Conclusions and clinical relevanceThe ADK mixture produced a smooth and rapid induction of anaesthesia, a low incidence of untoward side effects and full recovery after four hours. Supplementary oxygen might be advisable if a deeper plane of anaesthesia was required. Chemical restraint was adequate to perform non‐invasive procedures.     

A randomized, blinded, controlled trial of the antiemetic effect of ondansetron on dexmedetomidine-induced emesis in cats

ObjectiveTo determine the effect of ondansetron on the incidence of vomiting in cats pre-medicated with dexmedetomidine and buprenorphine.Study designRandomized, blinded, controlled trial.AnimalsEighty-nine female domestic shorthair cats, aged 3–60 months (median, 12 months) and weighing 1.2–5.1 kg.MethodsEach cat received dexmedetomidine (40 μg kg^?1) plus buprenorphine (20 μg kg^?1), intramuscularly as pre-anesthetic medication. Cats were assigned to three treatment groups: ondansetron (0.22 mg kg^?1, intramuscular [IM]), either 30 minutes before the pre-anesthetic medication (ONDA group, n = 31) or with the pre-anesthetic medication (OPM group, n = 30) mixed with the pre-anesthetic medications in the same syringe, or not to receive the antiemetic (control group, n = 28). Emesis was recorded as an all-or-none response. The number of episodes of emesis and the time until onset of the first emetic episode were recorded for each cat. Clinical signs of nausea were recorded whenever they occurred, and a numerical rating scale was used to quantify these signs. Data were analyzed using Kruskal–Wallis and Chi-square test; a Bonferroni correction was made for six comparisons; thus, the two-sided p for significance was 0.05/6 = 0.008.ResultsThere was a significant reduction in the number of cats vomiting, in the episodes of vomiting/cat, the time elapsed between the premedication and the first vomiting and the severity of nausea in the OPM group compared to the ONDA and control groups.Conclusions and clinical relevanceIn cats, the administration of ondansetron (0.22 mg kg^?1) ameliorates and reduced the severity of dexmedetomidine-induced nausea and vomiting only when it was administered in association with this drug.     

A comparison of epidural buprenorphine with epidural morphine for postoperative analgesia following stifle surgery in dogs

Objective To compare the efficacy of epidural buprenorphine with epidural morphine for post‐operative pain relief in dogs undergoing cranial cruciate ligament rupture repair. Study design A randomized, double blind clinical trial. Animals Twenty client‐owned dogs with cranial cruciate ligament rupture. Methods Dogs were randomly assigned to receive either epidural buprenorphine (4 µg kg^?1) or epidural morphine (0.1 mg kg^?1) in a total volume of 0.2 mL kg^?1. Epidural injections were performed immediately after induction of anesthesia. End‐tidal halothane and CO₂ were recorded every 15 minutes from the time of epidural administration of drug to extubation. A numerical rating pain score system was used by a blinded observer to evaluate analgesia beginning at extubation and continuing at specific intervals for 24 hours after surgery. Heart rate, respiratory rate, and blood pressure were recorded noninvasively at the same times. If pain score indicated moderate discomfort, rescue morphine at 1.0 mg kg^?1 was administered intramuscularly. Results There were no significant differences between groups with respect to pain score, heart rate, respiratory rate, indirect blood pressure, end‐tidal halothane or end‐tidal CO₂ at any time point. Fifty percent of dogs in the buprenorphine group and 50% of dogs in the morphine group required rescue analgesic medication. Time of systemic rescue morphine administration did not differ significantly between the two groups. There were no clinically observable side‐effects from epidural administration of either drug in any of the dogs of this study. Conclusions Epidural buprenorphine is as effective as epidural morphine for the relief of postoperative hindlimb orthopedic pain in dogs. Clinical relevance Buprenorphine appears to be an effective opioid for epidural use in healthy dogs. Buprenorphine may offer certain advantages over morphine for epidural use, such as lower abuse potential and, in some clinics, reduced cost and less wastage of drug.     

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.     

Effects of acepromazine on the incidence of vomiting associated with opioid administration in dogs

Objective To evaluate the anti‐emetic properties of acepromazine in dogs receiving opioids as pre‐anesthetic medication. Study design Randomized prospective clinical study. Animals One hundred and sixteen dogs (ASA I or II), admitted for elective surgical procedures. The dogs were a mixed population of males and females, purebreds and mixed breeds, 0.25–13.4 years of age, weighing 1.8–57.7 kg. Methods A prospective clinical trial in which the dogs were randomly assigned to one of three groups. All groups received acepromazine (0.05 mg kg^?1 intramuscularly (IM)). Group I received acepromazine 15 minutes prior to opioid administration. Group II received acepromazine in combination with the opioid. Group III received acepromazine 15 minutes after opioid administration. One of three different opioids was administered IM to each dog: morphine sulfate at 0.5 mg kg^?1; hydromorphone hydrochloride at 0.1 mg kg^?1; or oxymorphone hydrochloride at 0.075 mg kg^?1. Results Dogs receiving acepromazine before the opioid (group I) had a significantly lower incidence of vomiting (18%) than dogs in groups II (45%) and III (55%). The degree of sedation was significantly lower in the dogs receiving the combination of acepromazine and the opioid (group II) than in dogs receiving the opioid as the first drug (group III). Conclusions and clinical relevance Acepromazine administered 15 minutes before the opioid lowers the incidence of vomiting induced by opioids.     

RESEARCH PAPER: Sedative and cardiorespiratory effects of dexmedetomidine and buprenorphine administered to cats via oral transmucosal or intramuscular routes

ObjectiveTo determine if buprenorphine plus dexmedetomidine administered via the oral transmucosal route produces sufficient sedation in cats so that students can insert intravenous catheters.Study DesignProspective, randomized, blinded, clinical trial.AnimalsEighty‐seven shelter‐owned female cats aged 4–48 months, weighing 1.1–4.9 kg.MethodsCats were randomly allocated to two treatment groups based on route of drug administration: oral transmucosal (OTM), or intramuscular (IM). Buprenorphine (20 μg kg^?1) plus dexmedetomidine (20 μg kg^?1) were administered as pre‐medicants via one of these two routes. Prior to and 20 minutes after drug administration, heart and respiratory rates, systolic arterial pressure, and posture were measured and recorded. Twenty minutes after drug administration the same variables plus each cat’s response to clipper sound, clipping, and restraint were recorded; higher scores indicated more sedation.ResultsThere were no significant differences between the two groups prior to pre‐medication. Within each treatment group heart rate was significantly lower 20 minutes after treatment, but it did not differ significantly between the two groups. Twenty minutes after treatment, respiratory rate was significantly less in the OTM group, but did not differ significantly between the two groups. Systolic arterial pressure did not differ within or between the two groups at either time. Scores for posture increased significantly within both groups, and cats in the IM group had higher scores after treatment. Twenty minutes after treatment, cats in the IM group had higher scores for clipping and restraint than OTM cats. Ketamine (IM) was necessary to facilitate catheterization in 25% and 16% of cats in the OTM and IM groups, respectively, but this was not significantly different.Conclusions and clinical relevanceAdministration of dexmedetomidine plus buprenorphine by the OTM route is easy to perform, but produces less sedation than the IM route for IV catheterization in cats.     

Antagonistic effect of atipamezole, flumazenil and naloxone following anaesthesia with xylazine, tramadol and tiletamine/zolazepam combinations in pigs

ObjectiveTo evaluate the antagonistic effects of atipamezole (ATI), flumazenil (FLU) and naloxone (NAL) alone and in various combinations following administration of tiletamine–zolazepam–xylazine–tramadol.Study designProspective, experimental, randomized cross-over study.AnimalsEight Chinese miniature pigs (three females and five males) mean age 8 (range 7–10) months and bodyweight 57.5 (52.4–62.1) kg.MethodsAll animals were anaesthetized with tiletamine/zolazepam (3.0 mg kg^?1), xylazine (1.2 mg kg^?1) and tramadol (1.6 mg kg^?1) given intramuscularly (IM). Thirty minutes later, one of eight treatments was administered IM: saline control, ATI (0.12 mg kg^?1), FLU (0.1 mg kg^?1), NAL (0.03 mg kg^?1), ATI–FLU, FLU–NAL, ATI–NAL or ATI–FLU–NAL. After injection of antagonists the following times were recorded: to recovery of the palpebral, pedal and tail clamp reflexes, to head movement, sternal recumbency, standing and walking. Posture, sedation, analgesia, jaw relaxation and auditory response were scored at set times until 120 minutes after injection of antagonists. Heart rates, respiratory rates and rectal temperature were measured at those times. Data were analyzed by anova for repeated measures, followed by the Tukey’s test to compare differences between means, or by Kruskal–Wallis test as appropriate.ResultsFLU, NAL alone, or FLU–NAL did not effectively antagonize anaesthesia induced by tiletamine/zolazepam–xylazine–tramadol. ATI, ATI–FLU, ATI–NAL and ATI–FLU–NAL produced an immediate and effective recovery from anaesthesia. The combination of ATI–FLU–NAL was the most effective combination in antagonizing the anaesthetic effect. Adverse effects such as tachycardia, tachypnoea, excitement and muscle tremors were not observed during this study.Conclusion and clinical relevanceATI–FLU–NAL is the most effective combination for antagonizing tiletamine/zolazepam–xylazine–tramadol anaesthesia in pigs. However, ATI alone or in various combinations also provides effective antagonism.     

Thermal antinociceptive pharmacodynamics of 0.1 mg kg−1 hydromorphone administered intramuscularly in cats and effect of concurrent butorphanol administration

Hydromorphone (HY) has not been objectively assessed as an analgesic in cats. It has been suggested that butorphanol (B) can have a synergistic action with pure μ‐agonists. The aim of this study was to assess the antinociceptive activity of a single dose of HY, and to examine the effect of concurrent B administration on the thermal threshold (TT). Thermal thresholds were measured following IM administration of HY, B, a combination of B and HY (HY‐B), or saline (S). Six cats (four spayed females, two castrated males, 4.75–6.8 kg) were used. Each cat received HY (0.1 mg kg^?1), B (0.4 mg kg^?1), HY (0.1 mg kg^?1), and B (0.4 mg kg^?1) (HY‐B), or S (0.05 mL kg^?1) in a randomized, blinded, cross‐over study design. Each cat received each treatment, with at least 12 days interval between the treatments. All injections were IM randomized to left or right quadriceps using a 24 SWG needle. Twenty‐four hours prior to each study, the thorax of each of the cats was shaved. On the day of the study, TT was measured using a thorax‐mounted thermal threshold‐testing device specifically developed for cats. Skin temperature was recorded before each test and then the heater was activated. When the cat responded by flinching, turning, or jumping, the stimulus was terminated and the threshold temperature was recorded. Three baseline thresholds were recorded over 1 hour before IM injection of test drug. Thermal threshold cut‐off was 55.5 °C. TT was measured at 5 and 15 minutes, every 15 to 360 minutes, every 30 minutes to 8 hours, every hour to 12 hours, and at 24 hours post‐injection. Threshold data were analyzed using an anova with a repeat factor of time. Behavioral adverse effects (dysphoria) were associated with B administration, but not with HY or HY‐B administration (these produced calm euphoria). The control group was stable over time (p = 0.22) (mean threshold 40.15 °C). Overall, there was no period effect, no significant effect of administering B, but a significant effect (raised TT) of administering HY or HY‐B. If the mean value of one of the experimental groups differed from the control group (40.075 °C) by more than 2.355 °C (>42.425 °C), that mean was significantly different from control at p < 0.05 (Bonferroni's t‐tests). This occurred between 15 and 165 minutes for B, from 15 to 345 minutes for HY, and between 15 and 540 minutes for HY‐B. In this model, HY provided up to 5.75 hours of antinociception at 0.1 mg kg^?1, and concurrent administration of butorphanol (0.4 mg kg^?1) decreased the intensity of antinociception over the first 2 hours, but extended the duration of significant antinociception to about 9 hours.