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.     

Cardiorespiratory and anesthetic effects produced by the combination of butorphanol,medetomidine and alfaxalone administered intramuscularly in Beagle dogs

This study evaluated anesthesia quality, degree of analgesia and cardiorespiratory parameters after intramuscular (IM) injection of a combination of butorphanol (0.1 mg/kg), medetomidine (10 µg/kg) and alfaxalone (1.5 mg/kg) in ten healthy adult Beagle dogs. Rectal temperature (T), heart rate (HR), respiratory rate (f_R), arterial pressure, arterial blood gases and M-mode echocardiographic left ventricular (LV) indices were measured before drug administration and every 10 min thereafter until extubation. Mean duration of anesthesia, recovery and analgesia were 89 ± 17, 6 ± 1 and 80 ± 12 min. HR, f_R, partial pressure of arterial CO₂ and O₂, arterial pressure, and LV contractility were significantly altered during anesthesia. IM administration of the drug combination provided acceptable anesthesia, but produced substantial cardiorespiratory suppression.     

Evaluation of the anaesthetic effects of combinations of ketamine, medetomidine, romifidine and butorphanol in European badgers (Meles meles)

OBJECTIVE: To evaluate the effects of three anaesthetic combinations in adult European badgers (Meles meles). STUDY DESIGN: Prospective, randomized, blinded, experimental trial. ANIMALS: Sixteen captive adult badgers. METHODS: The badgers were each anaesthetized by intramuscular injection using the three techniques assigned in random order: romifidine 0.18 mg kg(-1), ketamine 10 mg kg(-1) and butorphanol 0.1 mg kg(-1) (RKB); medetomidine 0.1 mg kg(-1), ketamine 9 mg kg(-1) and butorphanol 0.1 mg kg(-1) (MKB); and medetomidine 0.1 mg kg(-1) and ketamine 10 mg kg(-1) (MK). Initial drug doses were calculated based on a body mass of 10 kg. Additional anaesthetic requirements, time to drug effect, duration of action and recovery from anaesthesia were recorded. Heart rate and rhythm, respiratory rate and rhythm, rectal and subcutaneous microchip temperature and oxygen saturation were recorded every 5 minutes. Depth of anaesthesia was assessed using: muscle tone; palpebral and pedal reflexes; and tongue relaxation at these time points. Blood samples and a tracheal aspirate were obtained under anaesthesia. Atipamezole was administered if the badger had not recovered within 60 minutes Parametric data were analysed using anova for repeated measures, and nonparametric data using Friedman's, and Cochran's Q tests: p < 0.05 was considered significant. RESULTS: All combinations produced good or excellent muscle relaxation throughout the anaesthetic period. RKB had the shortest duration of anaesthesia (16.8 minutes compared with MKB 25.9 minutes and MK 25.5 minutes) and antagonism was not required. RKB depressed respiratory rate less than MK and MKB. There was no significant difference between techniques for heart rate and rhythm. CONCLUSIONS AND CLINICAL RELEVANCE: All combinations provided anaesthetic conditions suitable for sampling and identification procedures in adult badgers. The RKB protocol provided a significantly shorter period of anaesthesia when compared with the combinations containing medetomidine.     

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.     

Alfaxalone compared with ketamine for induction of anaesthesia in horses following xylazine and guaifenesin

ObjectiveTo compare anaesthesia induced with either alfaxalone or ketamine in horses following premedication with xylazine and guaifenesin.Study designRandomized blinded cross-over experimental study.AnimalsSix adult horses, five Standardbreds and one Thoroughbred; two mares and four geldings.MethodsEach horse received, on separate occasions, induction of anaesthesia with either ketamine 2.2 mg kg^?1 or alfaxalone 1 mg kg^?1. Premedication was with xylazine 0.5 mg kg^?1 and guaifenesin 35 mg kg^?1. Incidence of tremors/shaking after induction, recovery and ataxia on recovery were scored. Time to recovery was recorded. Partial pressure of arterial blood oxygen (PaO₂) and carbon dioxide (PaO₂), arterial blood pressures, heart rate (HR) and respiratory rates were recorded before premedication and at intervals during anaesthesia. Data were analyzed using Wilcoxon matched pairs signed rank test and are expressed as median (range).ResultsThere was no difference in the quality of recovery or in ataxia scores. Horses receiving alfaxalone exhibited a higher incidence of tremors/shaking on induction compared with those receiving ketamine (five and one of six horses respectively). Horses recovered to standing similarly [28 (24–47) minutes for alfaxalone; 22 (18–35) for ketamine] but took longer to recover adequately to return to the paddock after alfaxalone [44 (38–67) minutes] compared with ketamine [35 (30–47)]. There was no statistical difference between treatments in effect on HR, PaO₂ or PaCO₂ although for both regimens, PaO₂ decreased with respect to before premedication values. There was no difference between treatments in effect on blood pressure.Conclusions and clinical relevanceBoth alfaxalone and ketamine were effective at inducing anaesthesia, although at induction there were more muscle tremors after alfaxalone. As there were no differences between treatments in relation to cardiopulmonary responses or quality of recovery, and only minor differences in recovery times, both agents appear suitable for this purpose following the premedication regimen used in this study.     

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.     

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.     

The use of a medetomidine,butorphanol and atropine combination to enable blood sampling in young pigs

AIM: To determine the suitability of a reversible, injectable anaesthetic combination including medetomidine, butorphanol and atropine to produce the degree of immobilisation required to allow blood sampling in young pigs.

METHODS: Twenty 6-week-old crossbred, intact male pigs were sedated with an intramuscular (I/M) injection of 80 µ'g/kg medetomidine, 200 µ'g/kg butorphanol and 25 µ'g/kg atropine. Heart and respiratory rates and rectal temperatures were monitored. Excessive salivation, gagging, laryngeal reflex, presence of pedal reflex and deep and surface analgesia were noted. Time of injection and the time when pigs reached mild and full sedation were also recorded.

RESULTS: Mild sedation was produced in 90% of pigs after 5.6 (SEM 0.96) min (n=18; median 5, range 2–16 min), and full sedation (lateral recumbency and loss of jaw tone) in 60% of pigs after 12.5 (SEM 2.14) min (n=12; median 10, range 5-28 min). The depth and duration of sedation were very variable and most animals were easily aroused. Ninety percent of the animals required the administration of halothane by mask to allow blood sampling, but the amount of halothane required was small. Heart and respiratory rates decreased (p<0.001) but remained within the normal range. Rectal temperature was above normal at the time of sedation and at the time of blood sampling when the ambient temperature was 29° C but not when the ambient temperature was reduced to 25°C.

CONCLUSIONS: The combination of medetomidine, butorphanol and atropine at these doses produced sedation of variable depth and duration that was insufficient on its own to allow blood sampling in the majority of pigs. Hyperthermia can occur in temperature-controlled environments when using medetomidine, butorphanol and atropine in pigs. Reduction of stress and a quieter environment may improve the effects of the anaesthetic combination.     

Alfaxalone in cyclodextrin for induction and maintenance of anaesthesia in ponies undergoing field castration

Objective  To evaluate the induction and maintenance of anaesthesia using alfaxalone following pre-anaesthetic medication with romifidine and butorphanol in ponies undergoing castration in the field.
Study design  Prospective clinical study.
Animals  Seventeen male ponies weighing 169 ± 29 kg.
Methods  The ponies were sedated with romifidine and butorphanol intravenously (IV). Induction time was recorded following administration of alfaxalone 1 mg kg⁻¹ and diazepam 0.02 mg kg⁻¹ IV. If movement during surgery occurred, alfaxalone 0.2 mg kg⁻¹ was administered IV. The quality of anaesthetic induction, and recovery were scored on a subjective scale of 1 (good) to 5 (poor). The number of attempts to attain sternal recumbency and standing, quality of recovery and times from induction to end of surgery, first head lift, sternal recumbency and standing were recorded.
Results  Induction quality was good [median score (range) 1 (1–3)] with a mean ± SD time of 29 ± 6 seconds taken to achieve lateral recumbency. Ten ponies required incremental doses of alfaxalone during surgery. Mean times to the end of surgery, first head lift, sternal recumbency and standing were 26 ± 9 minutes, 31 ± 9 minutes, 33 ± 9 minutes and 34 ± 9 minutes respectively. The number of attempts to attain sternal recumbency was 1(1–1) and to attain standing was 1(1–2). Quality of recovery was good, with a recovery score of 1(1–2).
Conclusions and clinical relevance  Alfaxalone provided smooth induction and recovery characteristics and was considered suitable for maintenance of anaesthesia for castration in ponies.     

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.     

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.     

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.     

Cardiopulmonary effects of medetomidine, oxymorphone, or butorphanol in selegiline-treated dogs

OBJECTIVES: To determine if chronic selegiline HCl administration affects the cardiopulmonary response to medetomidine, oxymorphone, or butorphanol in dogs. STUDY DESIGN: Prospective randomized experimental study. ANIMALS: Twenty-eight adult, random source, hound dogs weighing 21-33 kg. METHODS: Dogs were assigned to the following treatment groups: selegiline + medetomidine (MED; n = 6); placebo + MED (n = 6), selegiline + oxymorphone (OXY; n = 6); placebo + OXY (n = 6); selegiline + butorphanol (BUT; n = 7) or placebo + BUT (n = 6). Nine dogs were treated with two of the three pre-medicants. Dogs were treated with selegiline (1 mg kg(-1) PO, q 24 hours) or placebo for at least 44 days prior to pre-medicant administration. On the day of the experiment, arterial blood for blood gas analysis, blood pressure measurements, ECG, cardiac ultrasound (mM-mode, 2-D, and continuous wave Doppler), and behavioral observations were obtained by blinded observers. An IV injection of MED (750 micro g m(-2)), OXY (0.1 mg kg(-1)) or BUT (0.4 mg kg(-1)) was given. Cardiopulmonary and behavioral data were collected at 1, 2, 5, 15, 30, and 60 minutes after injection. RESULTS: Selegiline did not modify responses to any of the pre-medicant drugs. Medetomidine caused a significant decrease in heart rate (HR), cardiac output (CO), and fractional shortening (FS). Mean arterial pressure (MAP), systemic vascular resistance (SVR), and central venous pressure (CVP) were increased. Level of consciousness and resistance to restraint were both decreased. Oxymorphone did not affect MAP, CO, CVP, or SVR, but RR and PaCO(2) were increased. Level of consciousness and resistance to restraint were decreased. BUT decreased heart rate at 1 and 5 minutes. All other cardiovascular parameters were unchanged. BUT administration was associated with decreased arterial pH and increased PaCO(2). BUT decreased level of consciousness and resistance to restraint. CONCLUSIONS AND CLINICAL RELEVANCE: Although pre-medicants themselves altered cardiopulmonary and behavioral function, selegiline did not affect the response to medetomidine, oxymorphone, or butorphanol in this group of normal dogs.     

Alfaxalone anaesthesia in the green iguana (Iguana iguana)

ObjectiveTo characterise the anaesthetic effects of alfaxalone administered intramuscularly (IM) at 10, 20, and 30 mg kg^?1.Study designProspective, randomized cross-over study.AnimalsTen juvenile green iguanas (Iguana iguana) of mean body weight (±SD) 480 ± 134 g.MethodsAlfaxalone was administered IM in the triceps of both thoracic limbs. Times for anaesthetic induction, plateau and recovery periods were recorded. Skeletal muscle tone of the jaw, neck, thoracic limbs, pelvic limbs, and tail was scored. The palpebral, corneal and righting reflexes, and the response to painful stimuli were also assessed. Pulse rate and respiratory rate were recorded. Comparisons between different dosages and over time were made using anova.ResultsTimes are given for 10, 20 and 30 mg kg^?1 dosages respectively: mean time to maximal effect was 7.7 ± 2.2, 5.4 ± 1.7 and 3.9 ± 1.2 minutes; duration of the plateau phase was 11.3 ± 3.8, 22.1 ± 6.5 and 39.1 ± 11.5 minutes; recovery time was 10 ± 2.4, 17.5 ± 8.6 and 25 ± 7.1 minutes; and total anaesthetic duration was 29 ± 35.7, 45 ± 8.2 and 68 ± 9.8 minutes. Endotracheal intubation was possible in 40% of the subjects given 10 mg kg^?1 and in 100% subjects given both 20 and 30 mg kg^?1. Loss of response to a painful stimulus was seen in 0/10, 8/10 and 9/10 animals at 10, 20, and 30 mg kg^?1 respectively. There was an initial dose-dependent depression of respiration followed by a significant increase in frequency over time. In contrast, pulse rates decreased by 20% over the duration of the anaesthetic events.Conclusions and clinical relevanceIntramuscular administration of alfaxalone is a simple, rapid and reliable means of achieving relatively brief sedation or anaesthesia in healthy green iguanas. A dosage of 10 mg kg^?1 provides light sedation, appropriate for examination and venipuncture; 20 mg kg^?1 provides a level suitable for minor procedures or for endotracheal intubation and supplementation with inhalational anaesthesia; 30 mg kg^?1 produces an anaesthetic plane suitable for surgical procedures of limited duration (up to 40 minutes).