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.     

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.     

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.     

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

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

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

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

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.     

Medetomidine–ketamine–sevoflurane anaesthesia in juvenile Nile crocodiles (Crocodylus niloticus) undergoing experimental surgery

Objective

To describe the anaesthetic, physiological and side effects of intramuscular (IM) medetomidine and ketamine, followed by inhalational anaesthesia with sevoflurane, in Nile crocodiles (Crocodylus niloticus).

Tramadol improved the efficacy of ketamine–xylazine anaesthesia in young pigs

ObjectiveTo evaluate the influence of premedication with tramadol on xylazine–ketamine anaesthesia in young pigs.Study designProspective, randomized, blinded cross-over study.AnimalsTen young Niger hybrid pigs: mean weight 6.1 ± 0.6 kg.MethodsPigs were anaesthetized twice. Xylazine (2.5 mg kg^?1), ketamine (25 mg kg^?1) and atropine (0.04 mg kg^?1) were administered by intramuscular (IM) injection, 5 minutes after either tramadol (5 mg kg^?1)) (treatment XKT) or saline (treatment XKS). Time to loss of righting reflex (TLRR), duration of antinociception, duration of recumbency (DR) and recovery times (RCT) were recorded. Quality of induction of anaesthesia including ease of endotracheal intubation was assessed using a subjective ordinal rating score of 1 (worst) to 4 (best). Heart, pulse and respiratory rates, arterial oxygen saturations and rectal temperatures were determined over 60 minutes. Antinociception was assessed by the pigs’ response to artery forceps applied at the interdigital space. Data were compared with Student's t-test, Mann–Whitney's test or analysis of variance (anova) for repeated measures as appropriate and are presented as mean ± standard deviation.ResultsThe quality of anaesthetic induction was significantly better and duration of antinociception significantly longer (p < 0.05) in treatment XKT (3.1 ± 0.7 score; 43.7 ± 15.5 minutes) than in treatment XKS (2.8 ± 0.6 score; 32.0 ± 13.3 minutes). TLRR, DR and RCT did not differ significantly (p > 0.05) between treatment XKT (2.1 ± 0.8, 65.8 ± 17.0 and 13.2 ± 6.7 minutes) and treatment XKS (2.1 ± 1.3, 58.0 ± 14.8 and 10.3 ± 5.6 minutes). Physiological measurements did not differ between the treatments.Conclusion and clinical relevanceTramadol improved the quality of anaesthetic induction and increased the duration of antinociception in xylazine–ketamine anaesthetized young pigs without increasing duration of anaesthesia, nor causing additional depression of the physiological parameters measured.     

Intramuscular alfaxalone and methadone with or without ketamine in healthy cats: effects on sedation and echocardiographic measurements

ObjectiveTo evaluate the effect of alfaxalone and methadone administered intramuscularly (IM), with or without ketamine, on sedation and echocardiographic measurements in healthy cats.Study designA randomized, blinded, clinical study.AnimalsA group of 24 client-owned cats.MethodsBaseline echocardiographic evaluation (bEchoCG) was performed. Cats were given IM alfaxalone (2 mg kg^–1) and methadone (0.3 mg kg^–1) with (AMK group) or without (AM group) ketamine (1 mg kg^–1). A sedation score (0–5, indicating none to good sedation) was assigned at 5 (T5), 10 (T10) and 15 (T15) minutes after IM injection. At T15, a second echocardiographic evaluation (sEchoCG) was performed. Data are shown as median (range). Significance was p < 0.05.ResultsFinally, 21 cats were included. Sedation score was significantly higher in the AMK (11 cats) than in the AM group (10 cats): 4 (1–5) versus 0.5 (0–4) at T5 (p = 0.003); 4 (1–5) versus 1.5 (0–5) at T10 (p = 0.043); and 4 (1–5) versus 2 (0–5) at T15 (p = 0.024). All echocardiographic measurements obtained were within reference ranges. Between the groups, aortic root area (p = 0.009) and end-diastolic aortic dimension (p = 0.011) were significantly higher in the AM group at bEchoCG and sEchoCG, respectively. Within each group, values at bEchoCG and sEchoCG showed no significant differences, except for pulmonary peak velocity (0.85 m second^–1; p = 0.028) in the AMK group and ejection time (154 m second; p = 0.03) in the AM group; both variables decreased after sedation.Conclusions and clinical relevanceIn this population of healthy cats, neither protocol produced clinically meaningful effects on the echocardiographic variables evaluated. Alfaxalone with methadone produced mild sedation, whereas the addition of 1 mg kg^–1 ketamine induced adequate sedation for diagnostic procedures.     

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.     

The effect of body condition on propofol requirement in dogs

ObjectiveTo determine if body condition score (BCS) influences the sedative effect of intramuscular (IM) premedication or the dose of intravenous (IV) propofol required to achieve endotracheal intubation in dogs.Study designProspective clinical study.AnimalsForty–six client–owned dogs undergoing general anaesthesia.MethodsDogs were allocated to groups according to their BCS (BCS, 1 [emaciated] to 9 [obese]): Normal–weight Group (NG, n = 25) if BCS 4–5 or Over–weight Group (OG, n = 21) if BCS over 6. Dogs were scored for sedation prior to IM injection of medetomidine (5 μg kg^?1) and butorphanol (0.2 mg kg^?1) and twenty minutes later anaesthesia was induced by a slow infusion of propofol at 1.5 mg kg^?1 minute^?1 until endotracheal intubation could be achieved. The total dose of propofol administered was recorded. Data were tested for normality then analyzed using Student t–tests, Mann–Whitney U tests, chi–square tests or linear regression as appropriate.ResultsMean ( ± SD) propofol requirement in NG was 2.24 ± 0.53 mg kg^?1 and in OG was 1.83 ± 0.36 mg kg^?1. The difference between the groups was statistically significant (p = 0.005). The degree of sedation was not different between the groups (p = 0.7). Post–induction apnoea occurred in 11 of 25 animals in the NG and three of 21 in OG (p = 0.052).ConclusionsOverweight dogs required a lower IV propofol dose per kg of total body mass to allow tracheal intubation than did normal body condition score animals suggesting that IV anaesthetic doses should be calculated according to lean body mass. The lower dose per kg of total body mass may have resulted in less post–induction apnoea in overweight/obese dogs. The effect of IM premedication was not significantly affected by the BCS.Clinical relevanceInduction of general anaesthesia with propofol in overweight dogs may be expected at lower doses than normal–weight animals.     

Assessment of a carbon dioxide laser for the measurement of thermal nociceptive thresholds following intramuscular administration of analgesic drugs in pain‐free female cats

ObjectiveTo assess the potential of a thermal carbon dioxide (CO₂) laser to explore antinociception in pain-free cats.Study designExperimental, prospective, blinded, randomized study.AnimalsSixty healthy adult female cats with a (mean ± standard deviation) weight of 3.3 ± 0.6 kg.MethodsCats were systematically allocated to one of six treatments: saline 0.2 mL per cat; morphine 0.5 mg kg⁻¹; buprenorphine 20 μg kg⁻¹; medetomidine 2 μg kg⁻¹; tramadol 2 mg kg⁻¹, and ketoprofen 2 mg kg⁻¹. Latency to respond to thermal stimulation was assessed at baseline and at intervals of 15–30, 30–45, 45–60, 60–75, 90–105 and 120–135 minutes. Thermal thresholds were assessed using time to respond behaviourally to stimulation with a 500 mW CO₂ laser. Within-treatment differences in response latency were assessed using Friedman’s test. Differences amongst treatments were assessed using independent Kruskal–Wallis tests. Where significant effects were identified, pairwise comparisons were conducted to elucidate the direction of the effect.ResultsCats treated with morphine (X² = 12.90, df = 6, p = 0.045) and tramadol (X² = 20.28, df = 6, p = 0.002) showed significant increases in latency to respond. However, subsequent pairwise comparisons indicated that differences in latencies at specific time-points were significant (p < 0.05) only for tramadol at 60–75 and 90–105 minutes after administration (21.9 and 43.6 seconds, respectively) in comparison with baseline (11.0 seconds). No significant pairwise comparisons were found within the morphine treatment. Injections of saline, ketoprofen, medetomidine or buprenorphine showed no significant effect on latency to respond.Conclusions and clinical relevanceThe CO₂ laser technique may have utility in the assessment of thermal nociceptive thresholds in pain-free cats after analgesic administration and may provide a simpler alternative to existing systems. Further exploration is required to examine its sensitivity and comparative utility.     

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

ObjectiveTo establish a safe, reliable and reversible immobilization protocol for captive juvenile crocodiles.Study designProspective, randomized, clinical study.AnimalsThirty male estuarine crocodiles (body mass 1–12.1 kg) and 10 male Australian freshwater crocodiles (body mass 4.1–12.8 kg).MethodsAn optimized dose of medetomidine (0.5 mg kg^?1) was administered intramuscularly (IM) into the tail (Group 1; n = 5), pelvic limb (Group 2; n = 5) and thoracic limb (Groups 3 and 4; n = 5 in each group) of estuarine crocodiles weighing 3–12.1 kg. Their heart and respiratory rates and degree of immobilization were monitored every 15 minutes until recovery and daily thereafter for 3 subsequent days. In Group 4 (n = 5), medetomidine was antagonized with an optimized dose of atipamezole (2.5 mg kg^?1) given IM into the thoracic limb and time to recovery recorded. The effects of increasing doses of medetomidine given IM in the thoracic limb (n = 4) and intravenously (n = 6) were determined in 1–2 kg estuarine crocodiles. Australian freshwater crocodiles (4.1–12.8 kg) were administered medetomidine IM into the thoracic limb in divided doses at 0.5 mg kg^?1 (n = 5) and 0.75 mg kg^?1 (n = 5) and similarly monitored.ResultsImmobilization was achieved only in the estuarine crocodiles >3 kg and when medetomidine was administered into the thoracic limb. Immobilization was achieved within 30 minutes and the duration of immobilization lasted approximately 90 minutes. Immobilization in estuarine crocodiles was readily reversed with atipamezole. A dose of 0.75 mg kg^?1 was required to immobilize Australian freshwater crocodiles and the onset of immobilization was longer and the duration shorter than seen in the estuarine crocodiles. The heart and respiratory rates of all immobilized animals decreased significantly and arterial blood pressure became undetectable in the animals in which it was measured.Conclusions and clinical relevanceMedetomidine administered in the thoracic limb of captive estuarine and Australian freshwater crocodiles, ranging from 3 to 12.8 kg, provides a predictable onset and duration of immobilization sufficient for physical examination, sample collection, short minor procedures and translocation of the animals. Atipamezole administered in the thoracic limb results in complete reversal of the effects of medetomidine in the estuarine crocodile and a rapid return to normal behaviour.     

Comparison of analgesia provided by lidocaine, lidocaine-morphine or lidocaine-tramadol delivered epidurally in dogs following orchiectomy

ObjectiveTo evaluate and compare the postoperative analgesia provided by epidural lidocaine, lidocaine/morphine or lidocaine/tramadol in dogs following elective orchiectomy.Study designProspective experimental trial.AnimalsThirty-six mongrel dogs aged 2-8 years old, weighing 6.6-22 kg.MethodsThe dogs received 6.0 mg kg^?1 of lidocaine combined with 1.0 mg kg^?1 of tramadol, 0.1 mg kg^?1 of morphine or 0.01 mL kg^?1 of 0.9% NaCl epidurally. Analgesia was assessed at 4, 8, 12, 18 and 24 hours (T4, T8, T12 and T24) after the offset of lidocaine using a scale composed of physiologic and behavioral parameters. Rescue analgesia with morphine (0.2 mg kg^?1, IM) was performed if the evaluation score exceeded 10 during the postoperative period. The scores over time were analyzed using the Friedman’s two-way analysis of variance and the comparison between groups was made by the Kruskal-Wallis test with statistical significances accepted if p = 0.05.ResultsThere were no differences in the pain scores between the morphine and tramadol groups over time and no rescue analgesia was administered. In the NaCl group, rescue analgesia was needed at T4, T8 and T12. Within this group, the final evaluation times (T18 and T24) had lower pain scores than at T4, T8 and T12.Conclusions and clinical relevanceEpidural lidocaine/tramadol provided an analgesic effect comparable to that of epidural lidocaine/morphine during the first 12 hours after surgical castration without substantial side effects, suggesting that tramadol may be an effective postoperative analgesic in dogs submitted to this surgical procedure.     

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.     

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.     

Effect of bupivacaine on epidural analgesia produced by xylazine or medetomidine in buffaloes (Bubalus bubalis)

ObjectiveTo evaluate and compare the effect of epidural bupivacaine on analgesia produced by epidural xylazine or medetomidine in buffaloes.Study designProspective, blinded study.AnimalsTen male buffalo calves (6-8 months of age; body weight 70-90 kg) were used on two occasions to conduct a total of 20 investigations.MethodsCaudal extradural analgesia was produced in four buffalo calves each by the injection of either xylazine (0.05 mg kg^?1), medetomidine (15 μg kg^?1) or 0.5% bupivacaine (0.125 mg kg^?1), or combinations of xylazine and bupivacaine (0.05 and 0.125 mg kg^?1), or medetomidine and bupivacaine (15 μg kg^?1 and 0.125 mg kg^?1) at the first intercoccygeal extradural space. Analgesia was tested using deep pinprick stimuli.ResultsExtradural administration of xylazine or medetomidine resulted in complete analgesia of the tail, perineum, inguinal region and the upper parts of the hind limbs, which was faster in onset and longer in duration in the medetomidine group than in the xylazine group. Addition of bupivacaine increased the intensity of the analgesia produced by xylazine, but not that produced by medetomidine. All the drugs caused mild to moderate ataxia, but signs of sedation were apparent only in animals which received xylazine or medetomidine. The extradural injections of all the drugs caused significant decrease in heart rate (p = 0.024), respiratory rate (p = 0.026) and rectal temperature (p = 0.036) from the respective baseline values, but the differences between the groups were not significant.ConclusionsMedetomidine produced a longer duration of analgesia than that produced by xylazine. Bupivacaine prolonged the analgesia produced by xylazine, but the analgesia produced by the combination of medetomidine and bupivacaine was not superior to that produced by medetomidine alone.Clinical relevanceBupivacaine may be used to prolong the extradural analgesia produced by xylazine, but not that produced by medetomidine in buffaloes.     

Comparison between three dosages of intramuscular alfaxalone and a ketamine–dexmedetomidine–midazolam–tramadol combination in golden-headed lion tamarins (Leontopithecus chrysomelas)

ObjectivesTo characterize the cardiopulmonary and anesthetic effects of alfaxalone at three dose rates in comparison with a ketamine–dexmedetomidine–midazolam–tramadol combination (KDMT) for immobilization of golden-headed lion tamarins (GHLTs) (Leontopithecus chrysomelas) undergoing vasectomy.Study designProspective clinical trial.AnimalsA total of 19 healthy, male, wild-caught GHLTs.MethodsTamarins were administered alfaxalone intramuscularly (IM) at 6, 12 or 15 mg kg^–1, or KDMT, ketamine (15 mg kg^–1), dexmedetomidine (0.015 mg kg^–1), midazolam (0.5 mg kg^–1) and tramadol (4 mg kg^–1) IM. Immediately after immobilization, lidocaine (8 mg kg^–1) was infiltrated subcutaneously (SC) at the incision site in all animals. Physiologic variables, anesthetic depth and quality of immobilization were assessed. At the end of the procedure, atipamezole (0.15 mg kg^–1) was administered IM to group KDMT and tramadol (4 mg kg^–1) SC to the other groups; all animals were injected with ketoprofen (2 mg kg^–1) SC.ResultsA dose-dependent increase in sedation, muscle relaxation and immobilization time was noted in the alfaxalone groups. Despite the administration of atipamezole, the recovery time was longer for KDMT than all other groups. Muscle tremors were noted in some animals during induction and recovery with alfaxalone. No significant differences were observed for cardiovascular variables among the alfaxalone groups, whereas an initial decrease in heart rate and systolic arterial blood pressure was recorded in KDMT, which increased after atipamezole administration.Conclusions and clinical relevanceAlfaxalone dose rates of 12 or 15 mg kg^–1 IM with local anesthesia provided good sedation and subjectively adequate pain control for vasectomies in GHLTs. KDMT induced a deeper plane of anesthesia and should be considered for more invasive or painful procedures. All study groups experienced mild to moderate hypothermia and hypoxemia; therefore, the use of more efficient heating devices and oxygen supplementation is strongly recommended when using these protocols.