Evaluation of the anaesthetic effects of medetomidine and ketamine in rats and their reversal with atipamezole

ObjectivesTo compare the anaesthetic effects of varying doses of medetomidine (MED) combined with ketamine (KET) in rats, and to determine the efficacy of atipamezole (ATI) in the reversal of these effects using electroencephalogram (EEG) and assessment of clinical parameters.Study designProspective, randomized experimental trial.AnimalsTwenty-one male Sprague–Dawley rats weighing 300–398 g and aged 8–11 weeks old.MethodsThree groups received intraperitoneal injections of MED (0.2, 0.4 or 0.8 mg kg^?1) with KET (60 mg kg^?1) (MED-200, MED-400 and MED-800). Atipamezole, at doses five times higher than the previous dose of MED, was then administered intraperitoneally 70 minutes after MED-KET injection. The EEG band powers and spectral edge frequencies (SEFs), respiratory rates, reflex scores to toe-web clamping and behavioural changes were measured. Correlations between EEG parameters and reflex scores were also evaluated.ResultsThe duration of surgical anaesthesia was directly proportional to the dose of MED. Lower frequency bands (δ1 to α2) increased in all groups, and these changes were reversed by ATI. Minimal changes were observed in the higher frequency bands (β1 to γ), but their powers were increased by ATI. The SEFs were decreased in all groups, and they were reversed by ATI. While α1 band power and SEF95 showed strong correlations with the depth of anaesthesia, their changes appeared before the measured decreases in reflex score. Recovery from anaesthesia was extended by increasing the dose of MED.Conclusions and clinical relevanceSpectral EEG parameters may not accurately predict the depth of surgical anaesthesia because they had already changed during the induction of surgical anaesthesia. The ATI dose used in the present study may not be enough for complete reversal of anaesthesia induced by MED-KET.     

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.     

Sedative effects of propofol in horses

Objective  We hypothesized that propofol can produce rapidly-reversible, dose-dependent standing sedation in horses.
Study design  Prospective randomized, blinded, experimental trial.
Animals  Twelve healthy horses aged 12 ± 6 years (mean ± SD), weighing 565 ± 20 kg, and with an equal distribution of mares and geldings.
Methods  Propofol was administered as an intravenous bolus at one of three randomized doses (0.20, 0.35 and 0.50 mg kg⁻¹). Cardiovascular and behavioral measurements were made by a single investigator, who was blinded to treatment dose, at 3 minute intervals until subjective behavior scores returned to pre-sedation baseline values. Continuous data were analyzed over time using repeated-measures anova and noncontinuous data were analyzed using Friedman tests.
Results  There were no significant propofol dose or temporal effects on heart rate, respiratory rate, vertical head height, or jugular venous blood gases (pH_v, P_vO₂, P_vCO₂). The 0.35 mg kg⁻¹ dose caused mild sedation lasting up to 6 minutes. The 0.50 mg kg⁻¹ dose increased sedation depth and duration, but with increased ataxia and apparent muscle weakness.
Conclusions and clinical relevance  Intravenous 0.35 mg kg⁻¹ propofol provided brief, mild sedation in horses. Caution is warranted at higher doses due to increased risk of ataxia.     

Anaesthetic potency of isoflurane in cattle: determination of the minimum alveolar concentration

Objective To determine the minimum alveolar concentration (MAC) of isoflurane in cattle.
Study design Prospective study.
Animals Sixteen healthy adult female Holstein-Friesian cattle weighing 612 ± 17 kg (× ± SEM) and aged 5.7 ± 0.9 years old.
Methods The unsedated cattle were restrained in right lateral recumbency using a rope harness technique. Anaesthesia was induced with isoflurane (ISO) in oxygen via a face mask connected to a large-animal, semiclosed anaesthetic circle system. Each cow was intubated with a cuffed orotracheal tube (25 mm ID). Inspired and end-tidal ISO were monitored using a calibrated infra red analyser with a methane filter. The MAC of ISO that prevented gross purposeful movement in response to a tail and dewclaw clamp was determined. The time from the start of ISO administration to intubation, the time interval between discontinuance of ISO and the time the animal regained sternal recumbency, were recorded. Time to standing and quality of recovery were also recorded.
Results The time from the start of ISO administration to tracheal intubation was 18.68 ± 2.77 minutes. The MAC of ISO in these cattle was 1.27 ± 0.03% (1.14 ± 0.01% corrected to sea level). Time to sternal recumbency after 90 ± 16 minutes of anaesthesia from intubation was 4.60 ± 0.58 minutes and time to standing was 6.70 ± 1.02 minutes. All cattle were extubated when they regained sternal recumbency.
Conclusion The MAC of isoflurane in these cattle was 1.27 ± 0.03% (1.14 ± 0.01% corrected to sea level). ISO provided a smooth induction to, and rapid recovery from, anaesthesia.
Clinical relevance Knowledge of the MAC of ISO in cattle will facilitate its appropriate clinical use.     

Anesthesia in Sheep With Propofol or With Xylazine-Ketamine Followed by Halothane

Objective- This study evaluates the clinical usefulness and anesthetic effect of propofol, and compares these effects with those of xylazine-ketamine-halothane anesthesia in sheep.
Study Design- Prospective, randomized, clinical trial. Animals or Sample Population- Fourteen healthy adult male sheep.
Methods- Sheep were randomly assigned to two different drug regimens: (1) Bolus injection of propofol (3 mg/kg, intravenously [IV]) followed by continuous intravenous infusion and (2) xylazine (0.11 mg/kg, IV) and ketamine (2.2 mg/kg, IV) for induction followed by halothane anesthesia. Heart rate, respiratory rate, and arterial blood pressures were monitored during anesthesia. Venous blood samples were collected for blood gas analysis. Quality of induction and recovery were also recorded.
Results- The average dose of propofol used to induce and maintain anesthesia was 6.63 ±2.06 mg/kg and 29.3 ±11.7 mg/kg/hr (0.49 ±0.20 mg/kg/min), respectively. The duration of propofol anesthesia was 45.3 ±13.2 minutes and recovery to standing occurred in 14.7 ±5.7 minutes. Sheep receiving xylazine-ketamine-halothane were anesthetized for 35.9 ±4.0 minutes and recovery to standing occurred within 28.5 ±7.5 minutes. Sheep anesthetized with propofol had a significantly higher heart rate, diastolic blood pressure and Pvo₂, and a lower Pvco₂ at 30 minutes and lower BE at 15 and 30 minutes than sheep anesthetized with xylazine-ketamine-halothane.
Conclusions- Propofol anesthesia was characterized by a smooth induction, effective surgical anesthesia and rapid recovery which was comparable to anesthesia with xylazine-ketamine-halothane.
Clinical Relevance- Propofol may be indicated in situations when it is desirable to maintain anesthesia with an intravenous infusion followed by a rapid recovery in healthy sheep.     

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.     

Analgesic and motor-blocking action of epidurally administered levobupivacaine or bupivacaine in the conscious dog

Objective  To compare the analgesic and motor-blocking effects of epidurally administered levobupivacaine and bupivacaine in the conscious dog.
Study design  Prospective, randomized, cross-over study.
Animals  Six adult female Beagle dogs.
Methods  Each animal received three doses of levobupivacaine or bupivacaine (0.5, 1.0 and 1.5 mg kg⁻¹; concentrations 0.25%, 0.50%, and 0.75%, respectively) in a total volume of 0.2 mL kg⁻¹ by means of a chronically implanted epidural catheter. Onset, duration (through pinch response in the sacral, lumbar and toe areas) and degree of analgesia and motor-blocking status was determined with a scoring system and at regular intervals over 8.5 hours before (baseline) and after drug administration.
Results  Epidurally administered levobupivacaine and bupivacaine had a similar dose-dependent analgesic action with no significant differences in onset (range: 5–8 minutes), duration (bupivacaine: 42 ± 28, 135 ± 68 and 265 ± 68 minutes, and levobupivacaine: 28 ± 33, 79 ± 55 and 292 ± 133 minutes; 0.25%, 0.50%, and 0.75%, respectively) or maximum degree of analgesia. However, levobupivacaine tended to produce a shorter duration of motor block than bupivacaine and the difference in the motor to nociceptive blockade times was significant at the highest dose.
Conclusion  Epidural levobupivacaine produced an analgesic action similar to that of bupivacaine.
Clinical relevance  Epidural levobupivacaine is suitable for clinical use in dogs, mostly at the highest dose if a high degree of analgesia is required.     

Atipamezole changes the antinociceptive effects of butorphanol after medetomidine–ketamine anaesthesia in rats

Objective  To investigate the effects of atipamezole administered before butorphanol, on tail-flick latency (TFL) and also following medetomidine–ketamine anaesthesia in rats.
Study design  Prospective, randomized experimental study.
Animals  Thirty-four adult male Sprague–Dawley rats weighing 260–390 g.
Methods  TFL in 50 °C water was used to measure antinociception. In the first experiment, rats received saline ( n  = 5) or atipamezole ( n  = 5) followed by butorphanol treatments. In the second experiment, three groups of rats received saline ( n  = 8), atipamezole ( n  = 8) or atimpamezole ( n  = 8) followed by butorphanol 60 minutes after medetomidine–ketamine administration.
Results  In the first experiment, butorphanol significantly increased TFL compared to baseline. Atipamezole significantly decreased this effect. In the second experiment, TFL was significantly increased after recovery from medetomidine–ketamine anaesthesia compared to baseline. This was almost completely blocked by atipamezole. Atipamezole with butorphanol after recovery from the anaesthesia significantly reduced TFL compared to saline but still significantly increased TFL compared to the baseline.
Conclusion and clinical relevance  Atipamezole attenuated the analgesic effects of butorphanol. When postoperative atipamezole is used to hasten recovery from anaesthesia in rats, it may interfere with the postoperative analgesic effect of butorphanol.     

The effect of pre-anaesthetic medication on the incidence of cardiac arrhythmias during halothane anaesthesia in cats

Objective To compare the incidence of arrhythmias in cats receiving either acepromazine or diazepam for pre-anaesthetic medication prior to halothane anaesthesia.
Study design A blinded, randomized clinical study.
Animals Forty-six healthy cats undergoing surgery.
Methods Animals were allocated to one of two groups for pre-anaesthetic medication. Group 1 received diazepam (0.2 mg kg⁻¹). Group 2 received acepromazine (0.02 mg kg⁻¹). The trial drug was administered intramuscularly in combination with buprenorphine (0.01 mg kg⁻¹) 30 minutes prior to induction of anaesthesia with propofol (approximately 5 mg kg⁻¹). Anaesthesia was maintained using halothane: delivered concentration was 1–2% carried in oxygen and nitrous oxide via an endotracheal tube attached to an Ayre's T-piece (with Jackson-Rees modification) breathing system. The incidence of cardiac arrhythmias was determined by continuously monitoring the electrocardiogram from the time of induction until recovery occurred. Demographical group characteristics were compared using analysis of variance. The incidence of cardiac arrhythmias was compared by the Chi squared test. Statistical significance was set at the 5% level.
Results The two groups were similar in weight, age, length and type of procedure undertaken. The incidence of arrhythmias was the same in each group (3/23 cases) ( p = 1.0).
Conclusions The incidence of cardiac arrhythmias in this study did not appear to be influenced by the nature of pre-anaesthetic medication.
Clinical relevance The incidence of cardiac arrhythmias under halothane anaesthesia was 13% in this study. Acepromazine did not appear to exert an anti-arrhythmic effect. This may not be the case in a larger scale study.     

Evaluation of an anaesthetic technique used in dogs undergoing craniectomy for tumour resection

ObjeCTIVE: To evaluate a total intravenous anaesthetic technique in dogs undergoing craniectomy. STUDY DESIGN: Prospective clinical study. ANIMALS: Ten dogs admitted for elective surgical resection of rostro-tentorial tumours. METHODS: All dogs were premedicated with methadone, 0.2 mg kg(-1) intramuscularly 30 minutes prior to induction of anaesthesia. Anaesthesia was induced with propofol administered intravenously (IV) to effect, following administration of lidocaine 1 mg kg(-1) IV and maintained with a continuous infusion of propofol at < or =0.4 mg kg(-1) minute(-1) during instrumentation and preparation and during movement of the animals to recovery. During surgery, anaesthesia was maintained using a continuous infusion of propofol at 相似文献   

Anaesthesia with a combination of ketamine and medetomidine in the rabbit: effect of premedication with buprenorphine

ObjectiveTo assess the effects of premedication with buprenorphine on the characteristics of anaesthesia induced with ketamine/medetomidine.Study designProspective crossover laboratory study.AnimalsSix female New Zealand White rabbits.MethodsRabbits received, on occasions separated by 7 days, either buprenorphine (0.03 mg kg^?1) or saline subcutaneously (SC) as premedication, followed 1 hour later by SC ketamine (15 mg kg^?1) and medetomidine (0.25 mg kg^?1) (K/M). At pre-determined time points reflex responses and cardiopulmonary parameters were recorded and arterial blood samples taken for analysis. Total sleep time was the duration of loss of the righting reflex. Duration of surgical anaesthesia was the time of suppression of the ear pinch and pedal withdrawal reflexes. Wilcoxon signed-ranks tests were used to compare data before (T₀) and 10 minutes after (T₁₀) injection with K/M.ResultsAll animals lost all three reflex responses within 10 minutes of injection of K/M. The duration of loss of these reflexes significantly increased in animals that received buprenorphine. At induction, animals that had received buprenorphine tended to have a lower respiration rate but there were no significant differences in arterial PCO₂, PO₂ or pH between treatments. Hypoxaemia [median PaO₂ < 6.0 kPa (45 mmHg)] developed in both treatments at T₁₀ but there was no significant difference between treatments. Mean arterial pressure (MAP) was lower at T₁₀ in animals that had received buprenorphine.Conclusion and clinical relevancePremedication with buprenorphine significantly increased the duration of anaesthesia induced by K/M, with no significant depression of respiration further to the control treatment within the first 10 minutes of anaesthesia. The MAP decreased but this was not reflected in a difference in other physiological parameters. These data show that premedication with buprenorphine, before K/M anaesthesia in the rabbit, has few negative effects and may provide beneficial analgesia.     

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

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

Effects of different propofol infusion rates on EEG activity and AEP responses in rats

Parameters calculated from the auditory-evoked potential (AEP) recorded over the auditory cortex and from the electroencephalogram (EEG) recorded over the near vertex were compared in rats at three different infusion rates of propofol (62.5, 35 and 25 mg/kg/h). Depth of anaesthesia was assessed clinically using the strength of the pedal withdrawal reflex. Well-defined AEP responses were consistently obtained. As the propofol concentration was reduced, peak latencies decreased and peak to peak amplitudes increased. Amplitude and latency values were closely associated with the strength of the pedal withdrawal responses. Parameters calculated from the EEG showed no significant change as the propofol concentration was reduced. Periods of burst suppression became more frequent as the propofol infusion rate was increased. The study showed some of the difficulties that may be encountered when using EEG as a tool to assess depth of anaesthesia during propofol infusion. The AEP showed dose dependent changes in rats at different infusion rates of propofol. However, large variability between animals limits the use of this technique for monitoring depth of anaesthesia.     

The effects of anesthesia with a combination of intramuscular xylazine-diazepam-ketamine on heart rate, respiratory rate and cloacal temperature in roosters

ObjectiveTo examine the anesthetic effects of a xylazine-diazepam-ketamine (XDK) combination in roosters.Study designProspective experimental trial.AnimalsSix healthy white Leghorn roosters weighing 2.03 ± 0.08 kg.MethodsEach rooster was pre-medicated with xylazine (3 mg kg⁻¹, IM) and after 15 minutes anesthesia was induced with a diazepam (4 mg kg⁻¹) and ketamine (25 mg kg⁻¹) combination injected into the pectoral muscles. Heart and respiratory rates were recorded before anesthesia and every 15 minutes after induction for 165 minutes. Cloacal temperature was measured before and 15 minutes after pre-medication and every 75 minutes thereafter during anesthesia. Quality of induction and recovery were scored subjectively; duration of loss of righting reflex, abolition of response to a painful stimulus and palpebral reflex were also recorded.ResultsIntramuscular injection of xylazine smoothly induced loss of the righting reflex within 3–4 minutes. Loss of response to a painful stimulus occurred at 13.1 ± 2.9 minutes (mean ± SD) after the administration of the D-K combination, and lasted for 63.0 ± 5.3 minutes. Roosters anesthetized with this combination had a significant decrease in heart and respiratory rates and cloacal temperature. The recovery period lasted for up to 4 hours (227.5 ± 15.4 minutes). Quality of recovery was satisfactory for four roosters but excitation was noted in two birds.Conclusions and clinical relevanceThe XDK combination was a useful anesthetic technique for typhlectomy in roosters. Nevertheless this drug combination should be used with caution and cardiopulmonary parameters monitored carefully. Under the conditions of this experiment it was associated with a decreased cloacal temperature and prolonged recoveries.     

Gastro-oesophageal reflux during anaesthesia in the kitten: comparison between use of a laryngeal mask airway or an endotracheal tube

Objective  To compare the incidence of gastro-oesophageal reflux (GOR) during anaesthesia in the kitten when using a laryngeal mask airway (LMA) or an endotracheal tube (ET).
Study design  Prospective randomized cross-over experimental study.
Animals  Forty Domestic Short Hair laboratory cats, 19 females and 21 males, aged 12–15 weeks and weighing 0.57–1.73 kg (mean 1.13 ± SD 0.26).
Methods  Kittens were anaesthetized twice, once using the LMA and once the ET. Following induction of anaesthesia with isoflurane in an anaesthetic chamber and intubation of the trachea with the ET or placement of the LMA, a pH-electrode was introduced into the lower oesophagus. Monitoring of the oesophageal pH was performed for 45 minutes while anaesthesia was maintained with isoflurane. At the end of the experiment, gastric pH was measured. Kittens that had GOR during the experiment were treated with sucralfate, cisapride and ranitidine for 15 days.
Results  Oesophageal pH was 6.51 ± 0.76 and gastric pH was 1.54 ± 0.59. GOR was observed in nine kittens when the ET was used, and in 20 kittens when the LMA was used, the difference being significant ( p  =   0.013). The refluxate nearly always was acidic, being alkaline in only one kitten. Most of the GOR episodes occurred shortly after induction of anaesthesia and the oesophageal pH remained below 4.0 until the end of the experiment. No regurgitation was observed.
Conclusions and clinical relevance  The use of the LMA is associated with an increased incidence of GOR during anaesthesia in the kitten, which is not detected by observation. That this may have occurred should be considered if the kitten demonstrates signs of oesophagitis in the postoperative period.     

Cardiopulmonary effects during anaesthesia induced and maintained with propofol in acepromazine pre‐medicated donkeys

ObjectiveTo evaluate the cardiopulmonary effects of anaesthesia induced and maintained with propofol in acepromazine pre-medicated donkeys.Study designProspective experimental study.AnimalsSix healthy male donkeys weighing 78–144 kg.MethodsDonkeys were pre-medicated with intravenous (IV) acepromazine (0.04 mg kg⁻¹). Ten minutes later, anaesthesia was induced with IV propofol (2 mg kg⁻¹) and anaesthesia maintained by continuous IV infusion of the propofol (0.2 mg kg⁻¹ minute⁻¹) for 30 minutes. Baseline measurements of physiological parameters, and arterial blood samples were taken before the acepromazine administration, then 5, 15, 30, 45, and 60 minutes after the induction of anaesthesia. Changes from baseline were analysed by anova for repeated measures.ResultsWhen compared with baseline (standing) values, during anaesthesia heart rate increased throughout: significant at 5 (p = 0.001) and 15 (p = 0.015) minutes. Mean arterial blood pressure increased significantly only at 15 minutes (p < 0.001). Respiratory rate and arterial pH did not change significantly. PaO₂ was lower throughout anaethesia, but this only reached significance at 15 minutes (p = 0.041). PaCO₂ was statistically (but not clinically) significantly reduced at the times of 30 (p = 0.02), 45 (p = 0.01) and 60 (p = 0.04). Rectal temperature decreased significantly at all times of the study.Conclusions and clinical relevanceAdministration of propofol by the continuous infusion rate for the maintenance of anaesthesia resulted in stable cardiopulmonary effects and could prove to be clinically useful in donkeys.     

Some cardiopulmonary effects of midazolam premedication in clenbuterol-treated bitches during surgical endoscopic examination of the uterus and ovariohysterectomy

Midazolam was administered intravenously to 8 bitches in a randomised, placebo-controlled clinical trial before propofol induction of surgical anaesthesia. Anaesthesia was maintained with isoflurane-in-oxygen during surgical endoscopic examination of the uterus and ovariohysterectomy. Clenbuterol was administered at the start of surgery to improve uterine muscle relaxation, and to facilitate endoscopic examination of the uterus. Ventilation was controlled. Induction of anaesthesia with propofol to obtain loss of the pedal reflex resulted in a statistically significant (P < 0.05) decrease in minute volume and arterial oxygen partial pressure in the midazolam group. Apnoea also occurred in 50% of dogs in the midazolam group. The dose for propofol in the midazolam group was 7.4 mg/kg compared to 9.5 mg/kg in the control. Minute volume was significantly (P < 0.05) higher in both groups during isoflurane maintenance, compared to the value after incremental propofol to obtain loss of the pedal reflex. Propofol induction resulted in a 25-26% reduction in the mean arterial blood pressure in both groups, and the administration of clenbuterol at the start of surgery resulted in a transient, but statistically significant (P < 0.05), decrease in mean arterial blood pressure in the midazolam group during isoflurane anaesthesia. It is concluded that intravenous midazolam premedication did not adversely affect cardiovascular function during propofol induction, but intra-operative clenbuterol during isoflurane maintenance of anaesthesia may result in transient hypotension. Midazolam premedication may increase adverse respiratory effects when administered before propofol induction of anaesthesia.     

A comparative study of neurologically-equivalent propofol anaesthetic combinations in the dog

Propofol, administered as the sole anaesthetic agent, was evaluated when given alone and to dogs premed-icated with acepromazine or medetomidine. Both preanaesthetic agents reduced the dose of propofol required for induction of anaesthesia. Medetomidine significantly reduced the dose of propofol required for the maintenance of anaesthesia for a 30-minute period. An equivalent depth of anaesthesia was established in each protocol as judged by lack of response to mechanical noxious stimuli and total amplitude reduction of brain wave activity. Differences in physiological responses between propofol and acepromazine/propofol were not significant. The dogs in the medetomidine/propofol group had a significantly higher blood pressure and longer duration of anaesthesia and recovery. Oxygen saturation was maintained above 90% by the administration of supplemental oxygen. The study demonstrated the comparative responses to a biologically equivalent depth of anaesthesia, as confirmed by brain wave analysis, using three different techniques using propofol.     

A Prospective, Randomized, Double-Blinded, Placebo-Controlled Study of Human Intravenous Immunoglobulin for the Acute Management of Presumptive Primary Immune-Mediated Thrombocytopenia in Dogs

Background: Immune-mediated thrombocytopenia (IMT) is a common hematologic disorder in dogs. Human intravenous immunoglobulin (hIVIG) may have a beneficial effect in canine IMT.
Hypothesis: A single hIVIG infusion (0.5 g/kg) in dogs with presumed primary IMT (pIMT) is a safe adjunctive emergency treatment to accelerate platelet count recovery and shorten hospitalization time without increasing the cost of patient care.
Animals: Eighteen client-owned dogs with a presumptive diagnosis of pIMT.
Methods: Prospective, randomized, double-blinded, placebo-controlled clinical trial.
Results: There were no identifiable immediate or delayed adverse reactions associated with hIVIG administration over a 6-month period. The median platelet count recovery time for the hIVIG group was 3.5 days (mean ± SD: 3.7 ± 1.3 days; range, 2–7 days) and 7.5 days (mean ± SD: 7.8 ± 3.9 days; range, 3–12 days) for the placebo group. The median duration of hospitalization for hIVIG group was 4 days (mean ± SD: 4.2 ± 0.4 days; range, 2–8 days) and 8 days (mean ± SD: 8.3 ± 0.6 days; range, 4–12 days) for the placebo group. There was no significant difference between groups with respect to expense of initial patient care, whereas significant reduction in platelet count recovery time ( P = .018) and duration of hospitalization ( P = .027) were detected in the hIVIG group.
Conclusions and Clinical Importance: Compared with corticosteroids alone, adjunctive emergency therapy of a single hIVIG infusion was safe and associated with a significant reduction in platelet count recovery time and duration of hospitalization without increasing the expense of medical care in a small group of dogs with presumed pIMT.     

Comparative study on the sedative effects of morphine, methadone, butorphanol or tramadol, in combination with acepromazine, in dogs

Objective  To compare the effects of morphine (MOR), methadone (MET), butorphanol (BUT) and tramadol (TRA), in combination with acepromazine, on sedation, cardiorespiratory variables, body temperature and incidence of emesis in dogs.
Study design  Prospective randomized, blinded, experimental trial.
Animals  Six adult mixed-breed male dogs weighing 12.0 ± 4.3 kg.
Methods  Dogs received intravenous administration (IV) of acepromazine (0.05 mg kg⁻¹) and 15 minutes later, one of four opioids was randomly administered IV in a cross-over design, with at least 1-week intervals. Dogs then received MOR 0.5 mg kg⁻¹; MET 0.5 mg kg⁻¹; BUT 0.15 mg kg⁻¹; or TRA 2.0 mg kg⁻¹. Indirect systolic arterial pressure (SAP), heart rate (HR), respiratory rate ( f _R), rectal temperature, pedal withdrawal reflex and sedation were evaluated at regular intervals for 90 minutes.
Results  Acepromazine administration decreased SAP, HR and temperature and produced mild sedation. All opioids further decreased temperature and MOR, BUT and TRA were associated with further decreases in HR. Tramadol decreased SAP whereas BUT decreased f _R compared with values before opioid administration. Retching was observed in five of six dogs and vomiting occurred in one dog in MOR, but not in any dog in the remaining treatments. Sedation scores were greater in MET followed by MOR and BUT. Tramadol was associated with minor changes in sedation produced by acepromazine alone.
Conclusions and clinical relevance  When used with acepromazine, MET appears to provide better sedation than MOR, BUT and TRA. If vomiting is to be avoided, MET, BUT and TRA may be better options than MOR.