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.     

Alfaxalone induction dose following administration of medetomidine and butorphanol in the dog

ObjectiveTo determine in dogs the effects of medetomidine and butorphanol, alone and in combination, on the induction dose of alfaxalone and to describe the induction and intubation conditions.Study designProspective, randomized, blinded clinical trial.AnimalsEighty-five client-owned dogs (ASA 1 or 2).MethodsSubjects were block randomized to treatment group according to temperament. The treatment groups were: medetomidine 4 μg kg^?1 (M), butorphanol 0.1 mg kg^?1 (B), or a combination of both (MB), all administered intramuscularly. After 30 minutes, a sedation score was assigned, and alfaxalone 0.5 mg kg^?1 was administered intravenously over 60 seconds by an observer who was unaware of treatment group. Tracheal intubation conditions were assessed and, if tracheal intubation was not possible after 20 seconds, further boluses of 0.2 mg kg^?1 were given every 20 seconds until intubation was achieved. Induction dose and adverse events (sneezing, twitching, paddling, excitement, apnoea and cyanosis) were recorded; induction quality and intubation conditions were scored and recorded.ResultsThe mean dose of alfaxalone required for induction was similar for groups M and B: 1.2 ± 0.4 mg kg^?1. The mean dose requirement for group MB (0.8 ± 0.3 mg kg^?1) was lower than groups M and B (p < 0.0001). Induction dose was not influenced by temperament or level of sedation. Induction and intubation scores did not differ between treatment groups. Adverse events were noted in 16 dogs; there was no association with treatment group, temperament or level of sedation.Conclusions and clinical relevanceMedetomidine and butorphanol administered in combination reduce the anaesthetic induction dose of alfaxalone compared to either agent alone. This difference should be taken into account when using this combination of drugs in a clinical setting.     

Effects of vatinoxan in dogs premedicated with medetomidine and butorphanol followed by sevoflurane anaesthesia: a randomized clinical study

ObjectiveTo investigate effects of vatinoxan in dogs, when administered as intravenous (IV) premedication with medetomidine and butorphanol before anaesthesia for surgical castration.Study designA randomized, controlled, blinded, clinical trial.AnimalsA total of 28 client-owned dogs.MethodsDogs were premedicated with medetomidine (0.125 mg m^?2) and butorphanol (0.2 mg kg^?1) (group MB; n = 14), or medetomidine (0.25 mg m^?2), butorphanol (0.2 mg kg^?1) and vatinoxan (5 mg m^?2) (group MB-VATI; n = 14). Anaesthesia was induced 15 minutes later with propofol and maintained with sevoflurane in oxygen (targeting 1.3%). Before surgical incision, lidocaine (2 mg kg^?1) was injected intratesticularly. At the end of the procedure, meloxicam (0.2 mg kg^?1) was administered IV. The level of sedation, the qualities of induction, intubation and recovery, and Glasgow Composite Pain Scale short form (GCPS-SF) were assessed. Heart rate (HR), respiratory rate (f_R), mean arterial pressure (MAP), end-tidal concentration of sevoflurane (Fe′Sevo) and carbon dioxide (Pe′CO₂) were recorded. Blood samples were collected at 10 and 30 minutes after premedication for plasma medetomidine and butorphanol concentrations.ResultsAt the beginning of surgery, HR was 61 ± 16 and 93 ± 23 beats minute^?1 (p = 0.001), and MAP was 78 ± 7 and 56 ± 7 mmHg (p = 0.001) in MB and MB-VATI groups, respectively. No differences were detected in f_R, Pe′CO₂, Fe′Sevo, the level of sedation, the qualities of induction, intubation and recovery, or in GCPS-SF. Plasma medetomidine concentrations were higher in group MB-VATI than in MB at 10 minutes (p = 0.002) and 30 minutes (p = 0.0001). Plasma butorphanol concentrations were not different between groups.Conclusions and clinical relevanceIn group MB, HR was significantly lower than in group MB-VATI. Hypotension detected in group MB-VATI during sevoflurane anaesthesia was clinically the most significant difference between groups.     

Assessment of the effects of intramuscular administration of alfaxalone with and without medetomidine in Horsfield's tortoises (Agrionemys horsfieldii)

ObjectiveTo characterise four different intramuscular (IM) anaesthetic protocols, two with alfaxalone and two with alfaxalone in combination with medetomidine in terrestrial tortoises.Study designBlinded, randomized, cross‐over experimental study.AnimalsNine healthy adult male Horsfield's tortoises (Agrionemys horsfieldii).MethodsEach tortoise was randomly assigned to one of four different protocols: 1) 10 mg kg^?1 alfaxalone; 2) 10 mg kg^?1 alfaxalone + 0.10 mg kg^?1 medetomidine; 3) 20 mg kg^?1 alfaxalone; and 4) 20 mg kg^?1 alfaxalone + 0.05 mg kg^?1 medetomidine. During the experiment, the following variables were recorded: heart rate; respiratory rate; peripheral nociceptive responses; muscle strength; ability to intubate; palpebral, corneal and tap reflexes; and cloacal temperature.ResultsProtocols 1 and 2 resulted in moderate sedation with no analgesia, and moderate to deep sedation with minimal analgesia, respectively. Protocols 3 and 4 resulted in deep sedation or anaesthesia with variable analgesic effect; these two protocols had the longest total anaesthetic time and allowed intubation in 6/9 and 8/9 tortoises respectively. The total anaesthesia/sedation time produced by alfaxalone was significantly increased (p <0.05) by the addition of medetomidine. There were no significant differences regarding time to plateau phase and duration of plateau phase. Baseline heart rate of 53 ± 6 beats minute^?1 decreased significantly (p <0.05) with all protocols, and was lower (p <0.05) in protocols 3 and 4. Heart rate increased after atipamezole administration, but the increase was transient. In two tortoises, extreme bradycardia with no cardiac activity for 10 minutes was observed with protocols 3 and 4.Conclusion and clinical relevanceAlfaxalone 10 and 20 mg kg^?1 IM can be used for sedation for non‐painful procedures. Alfaxalone in combination with medetomidine can be used for deeper sedation or anaesthesia, but the observed respiratory and cardiovascular depression may limit its use.     

Effects of different doses of dexmedetomidine on anaesthetic induction with alfaxalone – a clinical trial

ObjectiveTo document the effects of two doses of dexmedetomidine on the induction characteristics and dose requirements of alfaxalone.Study designRandomized controlled clinical trial.AnimalsSixty one client owned dogs, status ASA I-II.MethodsDogs were allocated randomly into three groups, receiving as pre-anaesthetic medication, no dexmedetomidine (D₀), 1 μg kg^?1 dexmedetomidine (D₁) intramuscularly (IM) or 3 μg kg^?1 dexmedetomidine IM (D₃). All dogs also received 0.2 mg kg^?1 methadone IM. Level of sedation was assessed prior to induction of anaesthesia. Induction of general anaesthesia was performed with alfaxalone administered intravenously to effect at a rate of 1 mg kg^?1 minute^?1; the required dose to achieve tracheal intubation was recorded. Anaesthesia was maintained with isoflurane in oxygen. Cardiopulmonary parameters were recorded throughout the anaesthetic period. Quality of intubation, induction and recovery of anaesthesia were recorded. Quantitative data were compared with one-way anova or Kruskal-Wallis test. Repeated measures were log-transformed and analysed with repeated measures anova (p < 0.05).ResultsTreatment groups were similar for categorical data, with exception of sedation level (p < 0.001). The doses (mean ± SD) of alfaxalone required for intubation were D₀ 1.68 ± 0.24, D₁ 1.60 ± 0.36 and D₃ 1.41 ± 0.43, the difference between D₀ and D₃ being statistically significant (p = 0.036). Heart and respiratory rates during the anaesthetic period were significantly different over time and between groups (p < 0.001); systolic arterial blood pressure was significantly different over time (p < 0.001) but not between groups (p = 0.833). Induction quality and recovery scores were similar between groups (p = 1.000 and p = 0.414, respectively).Conclusions and clinical relevanceThe administration of alfaxalone resulted in a good quality anaesthetic induction which was not affected by the dose of dexmedetomidine. Dexmedetomidine at 3 μg kg^?1 IM combined with methadone provides good sedation and enables a reduction of alfaxalone requirements.     

A dose titration study into the effects of diazepam or midazolam on the propofol dose requirements for induction of general anaesthesia in client owned dogs,premedicated with methadone and acepromazine

ObjectiveTo assess the effect of a benzodiazepine co–induction on propofol dose requirement for induction of anaesthesia in healthy dogs, to describe any differences between midazolam and diazepam and to determine an optimal benzodiazepine dose for co–induction.Study designProspective, randomised, blinded placebo controlled clinical trial.AnimalsNinety client owned dogs (ASA I–III, median body mass 21.5kg (IQR 10–33)) presented for anaesthesia for a variety of procedures.MethodsDogs were randomised to receive saline 0.1 mL kg^?1, midazolam or diazepam at 0.2, 0.3, 0.4 or 0.5 mg kg^?1. All dogs received 0.01 mg kg^?1 acepromazine and 0.2 mg kg^?1 methadone intravenously (IV). Fifteen minutes later, sedation was assessed and scored prior to anaesthetic induction. Propofol, 1 mg kg^?1, was administered IV, followed by the treatment drug. Further propofol was administered until endotracheal intubation was possible. Recorded data included patient signalment, sedation score, propofol dosage and any adverse reactions.ResultsMidazolam (all groups combined) significantly reduced propofol dose requirement compared to saline (p < 0.001) and diazepam (p = 0.008). Midazolam (0.4 mg kg^?1) significantly reduced propofol dose requirement (p = 0.014) compared to saline, however other doses failed to reach statistical significance. Diazepam did not significantly reduce propofol dose requirement compared to saline (p = 0.089). Dogs weighing <5 kg, regardless of treatment group, required a greater propofol dose than those weighing 5–40 kg (p = 0.002) and those >40 kg (p = 0.008). Dogs which were profoundly sedated required less propofol than those which were mildly sedated (p < 0.001) and adequately sedated (p = 0.003).Conclusions and clinical relevanceMidazolam (0.4 mg kg^?1) given IV after 1 mg kg^?1 of propofol significantly reduced the further propofol dose required for intubation compared to saline. At the investigated doses, diazepam did not have significant propofol dose sparing effects.     

Effect of anaesthetic maintenance with isoflurane or propofol on ease of endoscopic duodenal intubation in dogs

ObjectiveTo compare the ease of endoscopic duodenal intubation (EDI) in dogs during maintenance of general anaesthesia with isoflurane or propofol infusion.Study designProspective, randomized, partially blinded clinical trial.AnimalsA total of 22 dogs undergoing upper gastrointestinal tract endoscopy to include EDI were recruited.MethodsDogs were randomly assigned isoflurane (ISO; n = 10) or propofol (PROP; n = 11) for maintenance of general anaesthesia. Following anaesthetic premedication with intramuscular medetomidine (0.005 mg kg^–1) and butorphanol (0.2 mg kg^–1), general anaesthesia was induced with propofol, to effect, maintained with 1.5% (vaporizer setting) isoflurane in 100% oxygen or 0.2 mg kg^–1 minute^–1 propofol. The dose of both agents was adjusted to maintain general anaesthesia adequate for the procedure. Degree of sedation 20 minutes post-anaesthetic premedication, propofol induction dose, anaesthetist and endoscopist training grade, animal’s response to endoscopy, presence of gastro-oesophageal and duodenal-gastric reflux, spontaneous opening of the lower oesophageal and pyloric sphincters, antral movement and time to achieve EDI were recorded. EDI was scored 1 (immediate entry with minimal manoeuvring) to 4 (no entry after 120 seconds) by the endoscopist, blinded to the agent in use. Data were tested for normality (Shapiro-Wilk test) and differences between groups analysed using independent t test, Mann-Whitney U test and Fisher’s exact test as appropriate.ResultsThere were no significant differences between groups for EDI score [median (interquartile range): 2 (3) ISO, 2 (3) PROP] or time to achieve EDI [mean ± standard deviation: 52.50 ± 107.00 seconds (ISO), 70.00 ± 196.00 seconds (PROP)]. Significantly more dogs responded to passage of the endoscope into the oesophagus in group PROP compared with group ISO (p = 0.01).Conclusions and clinical relevanceMaintenance of general anaesthesia with either isoflurane or propofol did not affect EDI score or time to achieve EDI.     

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.     

The sedative effects of low-dose medetomidine and butorphanol alone and in combination intravenously in dogs

ObjectiveTo evaluate the sedative effects of intravenous (IV) medetomidine (1 μg kg^?1) and butorphanol (0.1 mg kg^?1) alone and in combination in dogs.Study designProspective, blinded, randomized clinical trial.AnimalsSixty healthy (American Society of Anesthesiologists I) dogs, aged 6.2 ± 3.2 years and body mass 26 ± 12.5 kg.MethodsDogs were assigned to four groups: Group S (sodium chloride 0.9% IV), Group B (butorphanol IV), Group M (medetomidine IV) and Group MB (medetomidine and butorphanol IV). The same clinician assessed sedation before and 12 minutes after administration using a numerical scoring system in which 19 represented maximum sedation. Heart rate (HR), respiratory rate, pulse quality, capillary refill time and rectal temperature were recorded after each sedation score assessment. Sedation scores, sedation score difference (score after minus score before administration) and patient variables were compared using one-way anova for normally distributed variables and Kruskal–Wallis test for variables with skewed distributions and/or unequal variances. Where significance was found, further evaluation used Bonferroni multiple comparisons for pair-wise testing.ResultsBreed, sex, neuter status, age and body mass did not differ between groups. Sedation scores before substance administration were similar between groups (p = 0.2). Sedation scores after sedation were significantly higher in Group MB (mean 9.5 ± SD 5.5) than in group S (2.5 ± 1.8) (p < 0.001), group M (3.1 ± 2.5) (p < 0.001) and group B (3.7 ± 2.0) (p = 0.003). Sedation score difference was significantly higher in Group MB [7 (0–13)] than in Group S [0 (?1 to 4)] (p < 0.001) and Group M [0 (0–6)] (p < 0.001). HR decreased significantly in Groups M and MB compared with Group S (p < 0.05).Conclusion and clinical relevanceLow-dose medetomidine 1 μg kg^?1 IV combined with butorphanol 0.1 mg kg^?1 IV produced more sedation than medetomidine or butorphanol alone. HR was significantly decreased in both medetomidine groups.     

A preliminary investigation comparing pre-operative morphine and buprenorphine for postoperative analgesia and sedation in cats

Objective To compare the postoperative analgesic and sedative properties of buprenorphine and morphine in cats. Study Design Prospective, randomized, blinded study. Animals Thirty‐two domestic cats undergoing surgery. Methods Cats received pre‐anaesthetic medication with acepromazine (0.05 mg kg^?1) given intramuscularly and were randomly allocated to group M and given morphine (0.1 mg kg^?1) intramuscularly (IM) or to group B and given buprenorphine (0.01 mg kg^?1) IM. Anaesthesia was induced with propofol and maintained with halothane in oxygen and nitrous oxide. Pain and sedation scores using visual analogue scales, and heart and respiratory rates, were measured immediately before, and 30, 60, 120, 180, 300 and 420 minutes after anaesthesia. Results Pain scores were significantly lower at 60, 120 and 180 minutes after anaesthesia in group B. Group B also had higher heart rates at 30 minutes. There were no other statistically significant differences between the groups. Clinical relevance Buprenorphine (0.01 mg kg^?1) appeared to provide better postoperative analgesia than morphine (0.1 mg kg^?1) and may also have a longer duration of action.     

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.     

Midazolam,as a co‐induction agent,has propofol sparing effects but also decreases systolic blood pressure in healthy dogs

ObjectiveTo evaluate the effects of the co-administration of midazolam on the dose requirement for propofol anesthesia induction, heart rate (HR), systolic arterial pressure (SAP) and the incidence of excitement.Study designProspective, randomized, controlled and blinded clinical study, with owner consent.AnimalsSeventeen healthy, client owned dogs weighing 28 ± 18 kg and aged 4.9 ± 3.9 years old.MethodsDogs were sedated with acepromazine 0.025 mg kg^?1 and morphine 0.25 mg kg^?1 intramuscularly (IM), 30 minutes prior to induction of anesthesia. Patients were randomly allocated to receive midazolam (MP; 0.2 mg kg^?1) or sterile normal saline (CP; 0.04 mL kg^?1) intravenously (IV) over 15 seconds. Propofol was administered IV immediately following test drug and delivered at 3 mg kg^?1 minute^?1 until intubation was possible. Scoring of pre-induction sedation, ease of intubation, quality of induction, and presence or absence of excitement following co-induction agent, was recorded. HR, SAP and respiratory rate (f_R) were obtained immediately prior to, immediately following, and 5 minutes following induction of anesthesia.ResultsThere were no significant differences between groups with regard to weight, age, gender, or sedation. Excitement occurred in 5/9 dogs following midazolam administration, with none noted in the control group. The dose of propofol administered to the midazolam group was significantly less than in the control group. Differences in HR were not significant between groups. SAP was significantly lower in the midazolam group compared with baseline values 5 minutes after its administration. However, values remained clinically acceptable.Conclusions and clinical relevanceThe co-administration of midazolam with propofol decreased the total dose of propofol needed for induction of anesthesia in sedated healthy dogs, caused some excitement and a clinically unimportant decrease in SAP.     

Evaluation of different doses of propofol in xylazine pre-medicated horses

Objective To characterize responses to different doses of propofol in horses pre‐medicated with xylazine. Animals Six adult horses (five females and one male). Methods Each horse was anaesthetized four times with either ketamine or propofol in random order at 1‐week intervals. Horses were pre‐medicated with xylazine (1.1 mg kg^?1 IV over a minute), and 5 minutes later anaesthesia was induced with either ketamine (2.2 mg kg^?1 IV) or propofol (1, 2 and 4 mg kg^?1 IV; low, medium and high doses, respectively). Data were collected continuously (electrocardiogram) or after xylazine administration and at 5, 10 and 15 minutes after anaesthetic induction (arterial pressure, respiratory rate, pH, PaO₂, PaCO₂ and O₂ saturation). Anaesthetic induction and recovery were qualitatively and quantitatively assessed. Results Differences in the quality of anaesthesia were observed; the low dose of propofol resulted in a poorer anaesthetic induction that was insufficient to allow intubation, whereas the high dose produced an excellent quality of induction, free of excitement. Recorded anaesthesia times were similar between propofol at 2 mg kg^?1 and ketamine with prolonged and shorter recovery times after the high and low dose of propofol, respectively (p < 0.05; ketamine, 38 ± 7 minutes; propofol 1 mg kg^?1, 29 ± 4 minutes; propofol 2 mg kg^?1, 37 ± 5 minutes; propofol 4 mg kg^?1, 50 ± 7 minutes). Times to regain sternal and standing position were longest with the highest dose of propofol (32 ± 5 and 39 ± 7 minutes, respectively). Both ketamine and propofol reversed bradycardia, sinoatrial, and atrioventricular blocks produced by xylazine. There were no significant alterations in blood pressure but respiratory rate, and PaO₂ and O₂ saturation were significantly decreased in all groups (p < 0.05). Conclusion The anaesthetic quality produced by the three propofol doses varied; the most desirable effects, which were comparable to those of ketamine, were produced by 2 mg kg^?1 propofol.     

Anaesthesia with ketamine/medetomidine in the rabbit: influence of route of administration and the effect of combination with butorphanol

Objective To compare the characteristics of anaesthesia induced with ketamine/medetomidine administered by the subcutaneous and intramuscular routes and to assess the effects of the addition of butorphanol to this combination. Study design Prospective randomised study. Animals Six female New Zealand White rabbits. Methods Rabbits were given one of four combinations of ketamine and medetomidine (K/M) either subcutaneously (SC) or intramuscularly (IM) on four successive occasions with a 7‐day interval between treatments. The dose combinations were; 15/0.25 mg kg^?1 SC; 15/0.25 mg kg^?1 IM; 15/0.5 mg kg^?1 SC, and 15/0.25 mg kg^?1 together with 0.4 mg kg^?1 butorphanol (K/M/B) SC. The effects of anaesthesia on arterial blood gas values and cardiovascular variables were recorded at predetermined time points. Toe and ear pinch reflexes were judged to determine the duration of surgical anaesthesia. Loss of the righting reflex was used to measure the duration of sleep time. Analyses used repeated measures analysis of variance. Results All groups lost the righting reflex and ear pinch response. Three animals in the groups that received K/M alone lost their toe pinch reflex, whereas four lost this reflex when given K/M/B. Time of onset of loss of the righting, toe and ear pinch reflexes did not differ significantly among the groups. The higher dose combination of medetomidine with ketamine and the combination of K/M/B produced a greater duration of loss of the ear pinch response than the lower dose of K/M administered by either route. No significant differences were found among the groups in the duration of loss of the toe pinch reflex. All animals developed a moderate bradycardia (mean heart rate <166 beats minute^?1) and moderate hypoxaemia (mean P_aO₂ < 6.0 kPa). Animals given butorphanol showed the greatest reduction in respiratory rate (31 ± 13 breaths minute^?1, p < 0.05) but this was not reflected in any significant differences in arterial PCO₂, PO₂ or pH among the groups. Conclusions Administration of K/M by the SC route produced equivalent effects in comparison to intramuscular administration. The addition of butorphanol increased the duration of anaesthesia, but produced a slight increase in the degree of respiratory depression. All dose rates resulted in hypoxaemia so oxygen should be administered when these combinations are used in rabbits. Clinical relevance Subcutaneous administration is both technically simpler and may cause less discomfort to the animal than IM injection, and so is preferred. The combination of K/M with butorphanol has relatively minor effects on the depth and duration of anaesthesia, so offers little advantage to the use of K/M alone.     

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.     

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

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

Cardiac troponin I concentrations following medetomidine‐butorphanol sedation in dogs

ObjectiveTo evaluate the effect of medetomidine–butorphanol sedation on serum cardiac troponin I (cTnI) concentration, a marker of myocardial ischemia and injury, in healthy dogs undergoing pre–surgical radiographs for orthopedic procedures.Study designProspective clinical study.AnimalsTwenty client–owned dogs with no history of cardiac disease.MethodsDogs were evaluated for pre–existing cardiac disease with electrocardiogram (ECG), noninvasive blood pressure and echocardiogram. Sedation was achieved using a combination of medetomidine (10 μg kg^?1) and butorphanol (0.2 mg kg^?1) intravenously. Blood pressure, heart rate and ECG were serially recorded throughout the duration of sedation. Serum cTnI concentration was measured at baseline and 6, 18, and 24–hours post–sedation.ResultsFollowing administration of medetomidine and butorphanol, all dogs were adequately sedated for radiographs and had a decreased heart rate and increased diastolic blood pressure. Arrhythmias associated with increased parasympathetic tone occurred, including a sinus arrhythmia further characterized as a sinus bigeminy in 17 of the dogs. Serum cTnI was undetectable at all time points in all but three dogs. Two of the three dogs had a detectable concentration of cTnI at all time points measured, including prior to sedation. Only one of the two dogs had a cTnI concentration above the normal reference interval. The dogs that exhibited detectable cTnI had no significant difference in signalment, heart rate, blood pressure, or lactate concentration as compared to those with undetectable cTnI.Conclusions and clinical relevanceSedation with medetomidine and butorphanol had predictable cardiovascular effects including bradycardia, an increase in arterial blood pressure, and arrhythmias in apparently healthy dogs requiring radiographs for orthopedic injuries, but did not induce significant increases in serum cTnI concentration following the drug doses used in this study.     

Comparison of the effects of butorphanol–midazolam–medetomidine and butorphanol–azaperone–medetomidine in wild common palm civets (Paradoxurus musangus)

ObjectiveTo assess the efficacy of butorphanol–azaperone–medetomidine (BAM) and butorphanol–midazolam–medetomidine (BMM) protocols for immobilization of wild common palm civets (Paradoxurus musangus) with subsequent antagonization with atipamezole.Study designProspective, randomized, blinded clinical trial.AnimalsA total of 40 adult wild common palm civets, 24 female and 16 male, weighing 1.5–3.4 kg.MethodsThe civets were randomly assigned for anesthesia with butorphanol, azaperone and medetomidine (0.6, 0.6 and 0.2 mg kg^–1, respectively; group BAM) or with butorphanol, midazolam and medetomidine (0.3, 0.4 and 0.1 mg kg^–1, respectively; group BMM) intramuscularly (IM) in a squeeze cage. When adequately relaxed, the trachea was intubated for oxygen administration. Physiological variables were recorded every 5 minutes after intubation. Following morphometric measurements, sampling, microchipping and parasite treatment, medetomidine was reversed with atipamezole at 1.0 or 0.5 mg kg^–1 IM to groups BAM and BMM, respectively. Physiological variables and times to reach the different stages of anesthesia were compared between groups.ResultsOnset time of sedation and recumbency was similar in both groups; time to achieve complete relaxation and tracheal intubation was longer in group BAM. Supplementation with isoflurane was required to enable intubation in five civets in group BAM and one civet in group BMM. All civets in group BAM required topical lidocaine to facilitate intubation. End-tidal carbon dioxide partial pressure was lower in group BAM, but heart rate, respiratory rate, rectal temperature, peripheral hemoglobin oxygen saturation and mean arterial blood pressure were not different. All civets in both groups recovered well following administration of atipamezole.Conclusions and clinical relevanceBoth BAM and BMM combinations were effective for immobilizing wild common palm civets. The BMM combination had the advantage of producing complete relaxation that allowed intubation more rapidly.