The thermal antinociceptive effects of a high-concentration formulation of buprenorphine alone or followed by hydromorphone in conscious cats

ObjectiveTo evaluate the thermal antinociceptive effects of a high-concentration formulation of buprenorphine alone or followed by hydromorphone in conscious cats.Study designRandomized, blinded, placebo-controlled crossover study design.AnimalsA total of six purpose-bred, adult female ovariohysterectomized Domestic Short Hair cats.MethodsCats were allocated into three treatments each consisting of two injections, subcutaneous then intravenous (IV) administration, 2 hours apart: treatment SS, two injections of 0.9% saline; treatment BS, buprenorphine (0.24 mg kg^–1, 1.8 mg mL^–1) and saline; and treatment BH, buprenorphine (0.24 mg kg^–1) and hydromorphone (0.1 mg kg^–1). Skin temperature (ST) and thermal threshold (TT) were recorded before (baseline) and for 24 hours following first injection. TT data were analyzed using mixed linear models and a Benjamini–Hochberg sequential adjustment procedure (p < 0.05).ResultsThere were no significant differences among treatments for baseline ST and TT values, treatment SS over time and between treatments BS and BH. Compared with baseline, TT was significantly increased at all time points in treatments BH and BS except at 2 hours in treatment BS. TT was significantly higher than SS at 3–18 hours and 4–12 hours for treatments BS and BH, respectively. Maximal increases in TT were 47.5 °C at 2 hours, 53.9 °C at 3 hours and 52.4 °C at 6 hours in treatments SS, BS and BH, respectively.Conclusions and clinical relevanceAdministration of IV hydromorphone following high-concentration buprenorphine provided no additional antinociception and decreased the duration of effect when compared with high-concentration buprenorphine alone. Alternative analgesics should be considered if additional analgesia is required after administration of high-concentration buprenorphine.     

Thermal antinociception following oral administration of tapentadol in conscious cats

Objective

To evaluate the onset, magnitude and duration of thermal antinociception after oral administration of two doses of tapentadol in cats.

Effect of low dose rate ketamine infusions on thermal and mechanical thresholds in conscious cats

ObjectiveTo determine the thermal and mechanical antinociceptive effects of two different subanesthetic constant rate infusions of racemic ketamine in cats.Study designProspective, randomized, blinded, experimental study.AnimalsEight healthy adult domestic shorthair cats (two intact females and six neutered males).MethodsThe thorax and the lower thoracic limbs of each cat were shaved for thermal (TT) and mechanical threshold (MT) testing and a cephalic catheter was placed. Three intravenous treatments of equivalent volume were given as loading dose (LD) followed by an infusion for 2 hours: (K5) 0.5 mg kg^?1 ketamine followed by 5 μg kg^?1 minute^?1 ketamine infusion, (K23) 0.5 mg kg^?1 ketamine followed by 23 μg kg^?1 minute^?1 ketamine infusion or (S) 0.9% saline solution. Effects on behavior, sedation scores, MT and TT were obtained prior to drug treatment and 0.25, 0.5, 0.75, 1, 1.5, 2, 2.25, 2.5 2.75, 3 hours then every 0.5 hours for 7 hours and 10, 12, 14 and 26 hours after loading dose administration.ResultsKetamine induced mild sedation for the period of the infusion, no adverse behavioral effects were observed. Thermal threshold was significantly higher than baseline (K5: 44.5 ± 0.7 °C; K23: 44.5 ± 0.5 °C) at 15 minutes in the K5 group (46.8 ± 3.5 °C) and at 45 minutes in the K23 group (47.1 ± 4.1 °C). In the K23 group TT was significantly increased compared to S and K5 at 45 minutes. In K5 at 15 minutes MT (9.6 ± 4.0 N) was different to baseline (6.1 ± 0.8 N) and to the S group (5.9 ± 2.3 N).Conclusion and clinical relevanceLow dose rate ketamine infusions minimally affect thermal and mechanical antinociception in cats. Further studies with different nociceptive testing methods are necessary to assess whether ketamine could be a useful analgesic in cats.     

The effect of buprenorphine on isoflurane minimum alveolar concentration in dogs

ObjectiveTo determine the effect of intravenous (IV) buprenorphine on the isoflurane (ISO) minimum alveolar concentration (ISOMAC) in dogs.Study designRandomized, crossover, design.AnimalsSix healthy, adult (2–3 years old), intact dogs (two males and four females) weighing 7.4–11.0 kg.MethodsEach dog was studied on three occasions, 1 week apart, and baseline ISOMAC (MAC_B) was determined on each occasion. ISOMAC was defined as the mean of the end-tidal ISO concentrations that prevented and allowed purposeful movement in response to a noxious stimulus. After MAC_B determination, dogs were randomly given buprenorphine (BUP) at either 0.01, 0.05 or 0.1 mg kg^?1 IV, and ISOMAC was determined at two time periods after BUP administration. The first post-treatment determination (MAC_T1) was initiated 45 minutes after BUP administration and the second determination (MAC_T2) was initiated 4 hours after BUP administration. MAC values were determined in duplicate and the mean values were used for statistical analysis.ResultsIsoflurane minimum alveolar concentration was decreased at 141 minutes (the time of MAC_T1 determination) by 25%, 35%, and 27% after administration of BUP at 0.01, 0.05, and 0.1 mg kg^?1, respectively (p ≤ 0.05). The MAC reductions were not statistically different among doses. The reductions in ISOMAC at 342 minutes (the time of MAC_T2 determination) ranged from 13 to 16%, and were not statistically different among doses.Conclusions and clinical significanceBuprenorphine at 0.01, 0.05, and 0.1 mg kg^?1 significantly decreased ISOMAC in dogs at 141 minutes but not at 342 minutes. When using BUP for MAC reduction re-dosing may be required for procedures of long duration, and there may be no advantage to using the 0.1 mg kg^?1 dose.     

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.     

Sedative, cardiovascular, haematologic and biochemical effects of four different drug combinations administered intramuscularly in cats

ObjectiveTo compare effects of four drug combinations on sedation, echocardiographic, haematologic and biochemical variables and recovery in cats.Study designExperimental randomized ‘blinded’ cross-over study.AnimalsSix healthy cats.Materials and MethodsTreatments were administered intramuscularly: midazolam 0.4 mg kg^?1 and butorphanol 0.4 mg kg^?1 (MB); midazolam 0.4 mg kg^?1, butorphanol 0.4 mg kg^?1 and ketamine 3 mg kg^?1 (MBK); midazolam 0.4 mg kg^?1, butorphanol 0.4 mg kg^?1 and dexmedetomidine 5 μg kg^?1 (MBD); ketamine 3 mg kg^?1 and dexmedetomidine 5 μg kg^?1(KD). Sedation was evaluated at time-points over 10 minutes post injection. Echocardiography, systolic arterial blood pressure (SAP) measurement and blood sampling were performed at baseline and from 10 minutes after treatment. Quality of recovery was scored. Data were analysed by anova for repeated measures. p < 0.05 was considered significant.ResultsThe lowest sedation score was obtained by MB, (median 10.5 [7; 20]), highest by KD (36.5 [32; 38]). Quality of recovery was best with KD (0.5 [0; 2]), and worst with MB (7.5 [4; 11]). Relative to baseline measurements, treatments decreased SAP by 17%, 25%, 13%, 5% in MB, MBK, MBD and KD, respectively. Heart rate decreased (p < 0.05) after MBD (44%) and KD (34%). All treatments decreased stroke volume by 24%, 21%, 24%, 36%, and cardiac output by 23%, 34%, 54%, 53% in MB, MBK, MBD and KD, respectively. Packed cell volume was decreased (p < 0.05) by 20%, 31%, 29% in MBK, MBD and KD, respectively. Plasma glucose was increased after MBD (31%) and KD (52%) and lactate concentration was decreased (p < 0.05) after MBK (58%), MBD (72%) and KD (65%).Conclusions and clinical relevanceThe MB combination did not produce sedation in healthy cats. Treatment MBK led to acceptable sedation and minimal cardiovascular changes. Both treatments with dexmedetomidine produced excellent sedation and recovery but induced more cardiovascular depression and haematologic changes.     

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

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

Effects of dissociative anesthesia opioid-free protocols combined with local anesthesia,with or without flumazenil or atipamezole postoperatively,for orchiectomy in cats

ObjectiveTo evaluate the anesthetic effects of two drug combinations with local anesthesia, with or without postoperative antagonists, for orchiectomy in cats.Study designProspective, randomized blinded clinical study.AnimalsA total of 64 healthy cats.MethodsCats were assigned to four equal groups: ketamine (5 mg kg^–1) and dexmedetomidine (10 μg kg^–1) were administered intramuscularly (IM), followed postoperatively with intravenous (IV) saline (5 mL; group KDS) or atipamezole (50 μg kg^–1; group KDA); and ketamine (14 mg kg^–1) with midazolam (0.5 mg kg^–1) and acepromazine (0.1 mg kg^–1) IM, with postoperative IV saline (5 mL; group KMAS) or flumazenil (0.1 mg kg^–1; group KMAF). Lidocaine (2 mg kg^–1) was divided between subcutaneous and intratesticular injection. Physiologic variables were recorded at time points during anesthesia. Ketamine rescue dose was recorded. The degree of sedation and the quality of recovery were evaluated postoperatively.ResultsTime to loss of pedal reflex was longer in groups KMAS and KMAF than in groups KDS and KDA (p = 0.010). Total rescue dose of ketamine was higher in KMAS and KMAF than in KDS and KDA (p = 0.003). Heart rate (HR) during anesthesia was higher in KMAS and KMAF than in KDS and KDA (p = 0.001). Times to head up (p = 0.0005) and to sternal recumbency (p = 0.0003) were shorter in KDA than in KDS, KMAS and KMAF. Lower sedation scores were assigned sooner to KDA than KDS, KMAS and KMAF (p < 0.001). Recovery quality scores were good in all groups.Conclusions and clinical relevanceBoth anesthetic protocols allowed the performance of orchiectomy. Groups KMAS and KMAF required higher rescue doses of ketamine before injecting lidocaine. HR and oscillometric systolic pressure were minimally changed in groups KD and tachycardia was recorded in groups KMA. Only atipamezole shortened the anesthetic recovery.     

Comparison of bupivacaine femoral and sciatic nerve block versus bupivacaine and morphine epidural for stifle surgery in dogs

ObjectiveTo evaluate the efficacy of combined femoral and sciatic nerve blocks as an alternative to epidural anesthesia and analgesia in dogs undergoing stifle surgery under general anesthesia.Study designProspective, blinded, randomized, clinical comparison.AnimalsTwenty dogs weighing 37 ± 11 (mean ± SD) kg, aged 3 (1–8) [median (minimum–maximum)] years undergoing elective unilateral tibial-plateau leveling osteotomy.MethodsDogs were assigned randomly to receive either epidural anesthesia (bupivacaine 0.5%, 0.5 mg kg^?1 + morphine 0.1%, 0.1 mg kg^?1, in 0.2 mL kg^?1; EPID) or femoral and sciatic nerve blocks (Bupivacaine 0.5%, 0.1 mL kg^?1, was administered at each site; F + S) guided by electrolocation. All patients received a standard general anesthesia technique. Pain and sedation were scored (on scales of 0–10 and 0–3, respectively) pre-operatively, at extubation, and at 1, 4 and then every 4 hours thereafter up to 24 hours. Postoperatively, hydromorphone was administered to any patient with a pain score of >5 or whenever the blinded caregiver determined that more hydromorphone was necessary. Intraoperative heart rate (HR), mean arterial pressure (MAP), end tidal isoflurane (FE′ISO), body temperature, post-operative pain scores, time to first hydromorphone dose after surgery, time to first feeding, time to first drinking, time to first urination, time to first ambulation (walk on a lead) and cumulative dose of hydromorphone were recorded.ResultsIntra-operatively, FE′ISO and MAP were significantly lower in the EPID group (p = 0.05 and p = 0.04, respectively). Postoperatively, the cumulative hydromorphone consumption (p = 0.04) and the incidence of urinary retention (p = 0.03) were higher in the EPID group.Conclusion and clinical relevance F + S is a practical alternative to EPID that produces less urine retention and reduces opioid consumption in the 24 hours after surgery. EPID might be associated with a lower isoflurane requirement and lower systemic blood pressure.     

Epidural ketamine in the dromedary camel

ObjectiveTo evaluate the clinical and physiological effects of epidural injection of ketamine in camels.Study designRandomized prospective study.AnimalsTen healthy immature male dromedary camels.MethodsKetamine was administered epidurally at doses of 1 and 2 mg kg^?1 (five animals in each treatment). The drug was injected into the first intercoccygeal epidural space. Anti-nociception, sedation, ataxia, and effect on cardiopulmonary, rectal temperature and some selected haematological parameters were recorded at different intervals before (baseline) and after the drug administration. Data were analyzed by anova or U Mann–Whitney tests, as relevant and significance was taken as p < 0.05.ResultsEpidural ketamine at the 2 mg kg^?1 dose produced complete anti-nociception in the tail, anus and perineum, whilst the 1 mg kg^?1 dose produced complete anti-nociception only in the tail. Epidural ketamine resulted in mild to moderate sedation at the 1 mg kg^?1 dose and deep sedation at the 2 mg kg^?1 dose. Ataxia was observed in all test subjects and was severe, resulting in recumbency, in the 2 mg kg^?1 group. Respiratory rate and rectal temperature did not change significantly after injection of either treatment. Following epidural injection of 2 mg kg^?1 of ketamine, heart rate increased significantly from the pre-injection baseline of 55 ± 2 to 76 ± 4 (mean ± SD) beats minute^?1, but after the lower dose changes were not significant. The only significant changes in measured haematologic parameters were decreases in total erythrocyte count at 45 minutes and total leukocyte count from 45–75 minutes, in the 2 mg kg^?1 group.ConclusionEpidural ketamine injection was associated with caudal anti-nociception, sedation and ataxia in the dromedary camels; the intensity and duration of which was dose dependant.Clinical relevanceNeither of the doses of epidural ketamine injection in our study was applicable for standing surgical procedures in dromedary camels.     

Impact of surgical preparatory rinses with isopropyl alcohol or water on perioperative body temperature in pediatric female dogs and cats

ObjectiveTo describe the effects of presurgical preparation with an isopropyl alcohol or water rinse on the perioperative rectal temperature (RT) of puppies and kittens.Study designRandomized clinical trial.AnimalsA total of 48 intact female mixed breed puppies and 43 intact female Domestic Short Hair kittens aged 8–18 weeks.MethodsAll animals were premedicated with intramuscular buprenorphine (0.02 mg kg^–1) and acepromazine (0.05 mg kg^–1). Anesthesia was induced with intravenous propofol (4 mg kg^–1 to effect) for puppies or ketamine (5 mg kg^–1) and midazolam (0.25 mg kg^–1) for kittens. RT was measured every minute for the first 15 minutes at the beginning of hair/fur removal, then every 5 minutes for 45 minutes (dogs) and 35 minutes (cats). All animals were prepared for surgery using a 1.6% chlorhexidine solution, then rinsed with either isopropyl alcohol (group CA) or water (group CW).ResultsMean RT difference between the groups was not significant at any time point. The mean RT at 45 minutes for dogs was 35.9 °C and 36.0 °C in groups CA and CW, respectively (p = 0.74). The mean RT at 35 minutes for cats was 35.1 °C in both groups (p = 0.84).Conclusions and clinical relevanceThe use of either water or alcohol as a rinsing agent results in the same degree of perioperative temperature change. Other factors that contribute to perioperative hypothermia should be considered when choosing between these rinsing agents in surgical preparation of pediatric and small animals.     

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

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

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.     

Effect of pre-medication on gastroduodenoscopy in isoflurane-anesthetized cats

The pre‐medicant chosen may influence the ease with which gastroduodenoscopy (GD) is performed. The purpose of this study was to evaluate the relative ease of GD in cats under ketamine and isoflurane anesthesia after IM injection of hydromorphone (H, 0.1 mg kg^?1), hydromorphone plus glycopyrrolate (HG, 0.1 mg kg^?1 (H), 0.01 mg kg^?1 (G)), medetomidine (M, 0.03 mg kg^?1), or butorphanol (B, 0.4 mg kg^?1). Eight cats were assigned randomly to receive each treatment in a cross‐over design with at least 7 days between treatments. Twenty minutes after pre‐medication, medetomidine produced greater (p = 0.001) sedation than the other treatments when assessed, using a subjective ordinal scale. The cats were injected with ketamine (10 mg kg^?1 IM), orotracheally intubated, connected to a pediatric circle breathing system, and allowed to spontaneously breathe isoflurane in oxygen. Once end‐tidal isoflurane concentration was stable at 1.4% for 15 minutes, endoscopy was started. A single endoscopist (REG), who was unaware of the treatment used, performed all endoscopies. The endoscopist scored the difficulty of endoscopy subjectively (0–3). The significance of differences between treatments was evaluated using Friedman's test. Time for entering the stomach was 9.4 (4.7–15.9) (median (minimum–maximum)), 6.6 (5.2–11.7), 8.4 (6.3–16.5), and 7.7 (5.1–14.7) seconds and for entering the duodenum from the stomach was 20.5 (13.8–40.9), 18.2 (10.3–39.8), 20.2 (16.2–119.5), and 22.2 (11.8–83.8) seconds for H, HG, M, and B treatments, respectively. There were no significant differences in the time for, or difficulty of, endoscopy. We conclude that any of these drugs can be used satisfactorily at the doses and combinations tested to pre‐medicate cats prior to general anesthesia for GD.     

Comparison of the pharmacokinetics and thermal antinociceptive pharmacodynamics of 20 µg kg−1 buprenorphine administered sublingually or intravenously in cats

Little is known about the analgesic action of buprenorphine (BUP) in cats. Relative to man, the cat has a more alkaline oral pH, which may make this an effective route for administering BUP in this species. This study aimed to assess and compare the pharmacokinetics and pharmacodynamics of sublingual (S‐L) and IV administration of BUP. Thermal threshold (TT) was measured and blood samples were collected following IV or S‐L administration (20 µg kg^?1) of the injectable formulation. Six cats (five spayed females, one castrated male, 4.1–6.6 kg) were used. Each cat received both treatments in a randomized cross‐over study design with 1 month between experiments. Twenty‐four hours prior to each study, the lateral thorax of each of the cats was shaved, cephalic and jugular catheters placed, and oral pH measured. On the day of the study, TT was measured using a ‘thorax‐mounted’ thermal threshold‐testing device specifically developed for cats. The cats were free to move around. Skin temperature was recorded before each test, then the heater activated. When the cat responded by flinching, turning, or jumping, the stimulus was terminated and the threshold temperature was recorded. The thermal threshold cut‐off point was 55.5 °C. Three baseline thresholds were recorded before treatment with S‐L or IV (via cephalic catheter) BUP (20 µg kg^?1). Blood was withdrawn (jugular) at 1, 2, 4, 6, 10, 15, 30, 45, 60 minutes and at 2, 4, 6, 8, 12, and 24 hours post‐administration. TT was measured every 30 minutes?6 hours, 1–12 hours, and at 24 hours post‐administration. Plasma was immediately separated, stored at ?20.5 °C, and assayed within 4 months using a commercially available ¹²⁵I radioimmunoassay. Threshold data were analyzed using anova with a repeat factor of time. No adverse effects were noted. Pupils were dilated for up to 9 hours post‐BUP. Behavioral changes were calm euphoria. Measured oral pH was 9 in each cat. Pre‐treatment mean threshold (±SD) was 41.2 ± 0.9 °C in the S‐L group and 40.8 ± 0.85 °C in the IV group. There were no significant differences between the groups with respect to thresholds over time (p = 0.72). Thresholds were significantly increased from 30 to 360 minutes in both the groups (>44.615 °C). Peak plasma BUP (C_max) was lower (11 ± 6.7 ng mL^?1vs. 92.9 ± 107.9 ng mL^?1) and occurred later (T_max) (30 minutes vs. 1 minute) after S‐L compared to IV administration, respectively. BUP (20 µg kg^?1)‐administered S‐L or IV provided antinociception between 30 and 360 minutes after administration. Plasma levels did not correspond to TT.     

Cardiovascular effects of epidural administration of methadone, ropivacaine 0.75% and their combination in isoflurane anaesthetized dogs

ObjectiveTo compare the cardiovascular effects of four epidural treatments in isoflurane anaesthetised dogs.Study designProspective, randomized. experimental study.AnimalsSix female, neutered Beagle dogs (13.3 ± 1.0 kg), aged 3.6 ± 0.1 years.MethodsAnaesthesia was induced with propofol (8.3 ± 1.1 mg kg^?1) and maintained with isoflurane in a mixture of oxygen and air [inspiratory fraction of oxygen (FiO₂) = 40%], using intermittent positive pressure ventilation. Using a cross-over model, NaCl 0.9% (P); methadone 1% 0.1 mg kg^?1 (M); ropivacaine 0.75% 1.65 mg kg^?1 (R) or methadone 1% 0.1 mg kg^?1 + ropivacaine 0.75% 1.65 mg kg^?1 (RM) in equal volumes (0.23 mL kg^?1) using NaCl 0.9%, was administered epidurally at the level of the lumbosacral space. Treatment P was administered to five dogs only. Cardiovascular and respiratory variables, blood gases, and oesophageal temperature were recorded at T-15 and for 60 minutes after epidural injection (T0).ResultsMean overall heart rate (HR in beats minute^?1) was significantly lower after treatment M (119 ± 16) (p = 0.0019), R (110 ± 18) (p < 0.0001) and RM (109 ± 13) (p < 0.0001), compared to treatment P (135 ± 21). Additionally, a significant difference in HR between treatments RM and M was found (p = 0.04). After both ropivacaine treatments, systemic arterial pressures (sAP) were significantly lower compared to other treatments. No significant overall differences between treatments were present for central venous pressure, cardiac output, stroke volume, systemic vascular resistance, oxygen delivery and arterial oxygen content (CaO₂). Heart rate and sAP significantly increased after treatment P and M compared to baseline (T-15). With all treatments significant reductions from baseline were observed in oesophageal temperature, packed cell volume and CaO₂. A transient unilateral Horner’s syndrome occurred in one dog after treatment R.Conclusions and clinical relevanceClinically important low sAPs were observed after the ropivacaine epidural treatments in isoflurane anaesthetised dogs. Systemic arterial pressures were clinically acceptable when using epidural methadone.     

Cardiopulmonary effects and recovery characteristics of horses anesthetized with xylazine–ketamine with midazolam or propofol

Objective

To evaluate cardiopulmonary and recovery characteristics of horses administered total intravenous anesthesia (TIVA) with xylazine and ketamine combined with midazolam or propofol.

Efficacy of maropitant in preventing vomiting in dogs premedicated with hydromorphone

ObjectiveThe goal of this study was to evaluate the effectiveness of maropitant (Cerenia^®) in preventing vomiting after premedication with hydromorphone.Study designRandomized, blinded, prospective clinical study.AnimalsEighteen dogs ASA I/II admitted for elective orthopedic surgical procedures. The dogs were a mixed population of males and females, purebreds and mixed breeds, 1.0–10.2 years of age, weighing 3–49.5 kg.MethodsDogs were admitted to the study if they were greater than 1 year of age, healthy and scheduled to undergo elective orthopedic surgery. Dogs were randomly selected to receive one of two treatments administered by subcutaneous injection. Group M received 1.0 mg kg^?1 of maropitant, Group S received 0.1 mL kg^?1 of saline 1 hour prior to anesthesia premedication. Dogs were premedicated with 0.1 mg kg^?1 of hydromorphone intramuscularly. A blinded observer documented the presence of vomiting, retching and/or signs of nausea for 30 minutes after premedication.ResultsAll dogs in S vomited (6/9), retched (1/9) or displayed signs of nausea (2/9). None (0/9) of the dogs in M vomited, retched or displayed signs of nausea. Dogs in M had significantly fewer incidences of vomiting (p = 0.0090), vomiting and retching (p = 0.0023) and vomiting, retching and nausea (p < 0.0001) when compared to S.Conclusion and clinical relevanceMaropitant prevents vomiting, retching and nausea associated with intramuscular hydromorphone administration in dogs.     

Effect of maropitant,a neurokinin‐1 receptor antagonist,on the minimum alveolar concentration of sevoflurane during stimulation of the ovarian ligament in cats

ObjectiveDetermine if maropitant decreases the minimum alveolar concentration (MAC) of sevoflurane during stimulation of the ovarian ligament in cats.Study designProspective study.AnimalsFifteen, female cats weighing 2.5 ± 0.6kg (mean ± SD).MethodsAnesthesia was induced and maintained with sevoflurane. The right ovary was accessed via laparoscopy. A suture around the ovary and ovarian ligament was exteriorized through the abdominal wall for stimulation. A stimulus–response curve was created to identify the optimal force for MAC comparisons. In 10 cats, MAC was determined with only sevoflurane (baseline) then after 1 and 5 mg kg^?1 intravenous maropitant administration. The stimulation tension force used was 4.9 N. Repeated measures anova was used to compare the groups. MAC was defined as the average of the cross‐over concentrations and reported MAC is adjusted to sea‐level and depicted as mean ± SD.ResultsThe stimulus‐response curve was hyperbolic and plateaued at 4.3 ± 3 N. The optimal tension force chosen to compare MAC was 4.9 N. The baseline sevoflurane MAC was 2.96 ± 0.3%. Maropitant, 1 mg kg^?1, decreased the MAC to 2.51 ± 0.3% (15%, p < 0.01). The higher maropitant dose of 5 mg kg^?1 did not change MAC further when compared to the low dose (2.46 ± 0.4%, p = 0.33).Conclusion and clinical relevanceThe ovarian ligament stimulation model is suitable to determine MAC during visceral stimulation in cats. Maropitant decreased the anesthetic requirements during visceral ovarian and ovarian ligament stimulation in cats. Maropitant (1 mg kg^?1) decreases MAC by 15%; a higher dose had no additional effect.     

Sedative effects of hydromorphone or oxymorphone with or without acepromazine in dogs

Hydromorphone is an agonist opioid with potency approximately five times that of morphine and half that of oxymorphone. The purpose of this study was to compare hydromorphone with oxymorphone, with or without acepromazine, for sedation in dogs, and to measure plasma histamine before and after drug administration. Ten dogs received IM hydromorphone (H; 0.2 mg kg^?1), oxymorphone (O; 0.1 mg kg^?1), hydromorphone with acepromazine (H; 0.2 mg kg^?1, A; 0.05 mg kg^?1) or oxymorphone with acepromazine (O; 0.1 mg kg^?1, A; 0.05 mg kg^?1) in a randomized Latin‐square design. Sedation score, heart rate, respiratory rate, blood pressure, and SpO₂ were recorded at baseline and every 5 minutes after drug administration up to 25 minutes. Plasma histamine was measured at baseline and at 25 minutes post‐drug administration. Data were analyzed with repeated measures anova . Mean ± SD body weight was 21.62 ± 1.54 kg. Mean ± SD age was 1.07 ± 0.19 years. Sedation score was significantly greater for OA after 5 minutes than O alone (4.1 ± 3.5 versus 1.9 ± 1.5) and for HA after 15 minutes than H alone (8.6 ± 2.9 versus 5.9 ± 2.5). There was no significant difference in sedation between H and O at any time point. There was no significant difference between groups at any time with respect to heart rate, respiratory rate, blood pressure or SpO₂. Mean ± SD plasma histamine (nM ml^?1) for all groups was 1.72 ± 2.69 at baseline and 1.13 ± 1.18 at 25 minutes. There was no significant change in plasma histamine concentration in any group. Hydromorphone is effective for sedation in dogs and does not cause measurable increase in histamine. Sedation with hydromorphone is enhanced by acepromazine.