Comparison of sedative effects induced by medetomidine, medetomidine-midazolam and medetomidine-butorphanol in dogs

EVALUATION OF A BUTORPHANOL-MIDAZOLAM-MEDETOMIDINE PROTOCOL FOR SHORT PROCEDURES IN LESSER CHEVROTAINS (TRAGULUS SP.)

Twenty lesser chevrotains (Tragulus sp.), 10 males and 10 females, were anesthetized with a combination of butorphanol-midazolam-medetomidine (BMidM), to assess the efficacy of this protocol for short procedures in this genus. The animals received BMidM (0.32, 0.06, 0.15 mg/kg, respectively) intramuscularly via hand injection. Physiological variables were recorded once the animals reached a working depth of anesthesia that lasted 30 min (range 12-60 min). At the end of the procedure, medetomidine and butorphanol were antagonized with atipamezole (0.75 mg/kg) and naltrexone (0.3 mg/kg) intramuscularly, respectively. Induction and recovery were 9.4 ± 4.0 min and 10.2 ± 4.1 min, respectively. Supplementation with isoflurane via face mask was required in five animals to reach light anesthesia. Times to reach the various stages of anesthesia were compared between sexes. There was no difference between males and females reaching the different stages of anesthesia, except for the time required to reach the ambulatory stage, in which females took a significantly longer time (11.8 min vs 7.8 min for the males) to stand after the injection of the antagonists (P = 0.02). Heart rate, respiratory rate, rectal temperature, and peripheral hemoglobin oxygen saturation were similar between sexes and stable throughout the procedure. At the dosage tested BMidM was a reliable and safe protocol for short, minimally invasive procedures in lesser chevrotains with a fast induction and smooth recovery without complications.

Cutaneous anaphylactoid reaction to polyoxyethylene hydrogenated castor oil in dogs

BACKGROUND

Polyoxyethylene hydrogenated castor oil (HCO ethoxylates) is a nonionic surfactant used as an excipient for ointments and injections in human and veterinary drugs. Several polyethylene glycol (PEG) derivatives can be obtained depending on the number of moles of ethylene oxide (EO). HCO ethoxylates have the potential to cause anaphylactoid reactions. There is little published information about these types of reactions in dogs.

OBJECTIVE

To determine the potential for HCO-ethoxylate-containing drugs to cause anaphylactoid reactions in dogs, employing intradermal testing (IDT) with various concentrations of HCO ethoxylates (HCO-25, -40, -60 and -80).

ANIMALS

Four healthy male laboratory dogs.

MATERIALS AND METHODS

We performed IDT with drugs containing HCO ethoxylates and HCO ethoxylates alone to determine threshold concentrations. The IDT scores and threshold concentrations were compared. Analysis of skin biopsies from IDT sites was used to measure the percentage of degranulated mast cells. The effect of histamine at IDT sites was investigated by pre-treatment with an antihistamine.

RESULTS

All HCO-ethoxylate-containing drugs caused a wheal-and-flare reaction. The threshold concentrations (0.001% and 0.00001%) of each HCO-ethoxylate depended on the number of moles of EO (p < 0.05). Mast cell degranulation was enhanced by all HCO ethoxylates. The HCO-60-induced reaction was suppressed by an oral antihistamine.

CONCLUSIONS AND CLINICAL RELEVANCE

The threshold concentration can serve as a consideration for developing safe new drug formulations and for clinical decision-making around using drugs containing PEG derivatives. IDT is useful to predict the risk of adverse effects. Antihistamines could demonstrate a prophylactic effect.

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

OBJECTIVE

To 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 DESIGN

Prospective, randomized, blinded clinical trial.

ANIMALS

A total of 40 adult wild common palm civets, 24 female and 16 male, weighing 1.5-3.4 kg.

METHODS

The 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.

RESULTS

Onset 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 RELEVANCE

Both 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.

Photochemical fate of medetomidine in coastal and marine environments

Medetomidine has been authorized in ship hull paints as an antifouling biocide under the biocidal product regulation in Europe since 2016. Its release into marine systems causes concerns over persistence and toxicity. However, the environmental fate of medetomidine has not been fully investigated. In this study, the photodegradation of medetomidine under natural sunlight conditions was investigated using collected coastal and sea waters. In addition, the phototransformation of medetomidine with reactive species (i.e., singlet oxygen, excited triplet state organic matter, and hydroxyl radicals) under UVA light was examined. Photoproducts were isolated by high-performance liquid chromatography (HPLC), identified by a combination of nuclear magnetic resonance (NMR) spectroscopy and time-of-flight mass spectrometry (qTOF), and reaction mechanisms were proposed. The results show that medetomidine is a neutral base (pKa of protonated form = 7.2) that leads to two different protonation states in the aquatic environment. Photodegradation of neutral medetomidine was dominated by reaction with singlet oxygen, while protonated medetomidine was relatively photostable. The contribution of reactive species to the overall photodegradation of neutral medetomidine was calculated to provide an assessment of phototransformation of medetomidine. The half-live of medetomidine was < 1.5 days in natural waters (pH_coastal = 8.3; pH_sea = 8.1) under sunlit near-surface conditions, suggesting that it is not persistent in the aquatic environment. Because medetomidine has a relatively short half-life in sunlit aquatic ecosystems, a number of products, such as 2-(2,3-dimethylphenyl)propanamide, can be formed by photochemical reactions of medetomidine, with unknown consequences for marine and coastal waters.

The anesthetic effects of intramuscular alfaxalone in dogs premedicated with low-dose medetomidine and/or butorphanol

We aimed to evaluate the induction, anesthesia, and cardiorespiratory effects of intramuscular (IM) anesthetic protocol with alfaxalone following premedication with low-dose medetomidine, butorphanol, or a combination of both (medetomidine–butorphanol) in dogs. Six healthy beagles were administered 1, 2.5, or 5 mg/kg alfaxalone IM following premedication with low-dose medetomidine (5 µg/kg; MA-IM), butorphanol (0.3 mg/kg; BA-IM), or medetomidine-butorphanol (5 µg/kg and 0.3 mg/kg, respectively; MBA-IM). Each dog received 9 treatments with minimum 7-day washout period between treatments. Dogs were allowed to breath room air during anesthetic induction. We attempted endotracheal intubation after alfaxalone administration. Alfaxalone produced a dose-dependent anesthetic effect in each anesthetic protocol. Intubation was achieved in 4 out of 6 dogs that received MA-IM and BA-IM with 2.5 mg/kg alfaxalone and in all dogs that received MBA-IM with 1, 2.5, and 5 mg/kg alfaxalone. The median durations [minimum–maximum] of accepting intubation were 79 [0–89], 97 [84–120], and 117 [84–217] min, respectively. Hypotension (mean arterial blood pressure <60 mmHg) did not develop, but bradycardia (heart rate <60 beats/min) was observed in all dogs that received the MA-IM and MBA-IM protocols. Severe hypoxemia (percutaneous arterial oxygen saturation <90%) developed in 2 dogs that received MBA-IM with 5 mg/kg alfaxalone. We consider that the MA-IM and BA-IM protocols with ≥2.5 mg/kg alfaxalone and the MBA-IM protocol with 1–2.5 mg/kg alfaxalone could provide clinically useful and effective anesthesia without causing severe cardiorespiratory depression in healthy dogs.

Pharmacokinetics and efficacy of trazodone following rectal administration of a single dose to healthy dogs

OBJECTIVE

To determine the pharmacokinetics and efficacy of trazodone following rectal administration of a single dose to healthy dogs.

ANIMALS

6 healthy adult dogs.

PROCEDURES

Each dog received a single dose of trazodone (approx 8 mg/kg) per rectum. Trazodone tablets were crushed into a powder, mixed with 5 mL of tap water, and injected into the rectum via a red rubber catheter. Sedation scores were assigned, and blood samples were collected for determination of plasma trazodone concentration at predetermined times before and after drug administration. Pharmacokinetic parameters were estimated by noncompartmental analysis.

RESULTS

Plasma trazodone concentration remained below the detection limit for 1 dog even though it became moderately sedate. Median (interquartile [25th to 75th percentile] range [IQR]) maximum plasma trazodone concentration and volume of distribution and clearance corrected for bioavailability were 1.00 μg/mL (0.66 to 1.40 μg/mL), 10.3 L/kg (7.37 to 14.4 L/kg), and 639 mL/kg/h (594 to 719 mL/kg/h), respectively. Median time to maximum plasma trazodone concentration and elimination half-life were 15 minutes (range, 15 to 30 minutes) and 12 hours (IQR, 7.99 to 12.7 hours), respectively. All dogs became mildly or moderately sedate, and the extent of sedation was maximal at a median of 30 minutes (IQR, 30 to 60 minutes) after trazodone administration. No adverse effects were observed.

CONCLUSIONS AND CLINICAL RELEVANCE

Rectal administration of trazodone may be a viable option for sedation and treatment of anxiety in dogs for which administration of sedatives and anxiolytics by other routes is contraindicated. Further research is necessary to better elucidate the pharmacokinetics and efficacy of trazodone following rectal administration and determine optimal dosing.

Effects of Sedation by Intramuscular Administration of Medetomidine on Canine Abdominal Vascular System and Hepatic Parenchyma Imaging Using Enhancement Dynamic Computed Tomography

This prospective crossover study compared the effects of intramuscular administration of medetomidine for sedation on parameters of the abdominal vascular system, measured by enhancement computed tomography (CT), to those of propofol-induced sevoflurane maintenance anesthesia, as a control, in five clinically healthy adult male beagle dogs (11.4–12.8 kg). Each animal underwent both protocols at a 1-week interval. The enhancement (HU) and time to peak enhancement on CT were measured for the aorta (AO), caudal vena cava (CVC), portal vein (PV), and hepatic parenchyma (HP). The contrast effects in the AO, PV, and HP were significantly delayed under medetomidine sedation compared to the control anesthesia protocol. Particularly, the contrast effect in the PV and HP was significantly delayed under sedation, appearing approximately 1 min after contrast medium injection. This delay likely reflects the peripheral vasoconstrictive effect of medetomidine. We noted a generally early high contrast enhancement of the CVC under medetomidine sedation, likely contributed by the induced bradycardia. Therefore, findings obtained on contrast enhancement CT under medetomidine sedation may be different from those obtained under propofol-induced sevoflurane maintenance anesthesia. These differences are important to consider when using the findings to inform diagnosis.

Evaluation of anaesthetic and cardiorespiratory effects after intramuscular administration of alfaxalone alone, alfaxalone-ketamine and alfaxalone-butorphanol-medetomidine in common marmosets (Callithrix jacchus)

BACKGROUND

Anaesthesia is often required in common marmosets undergoing various procedures. The aim of this study was to evaluate anaesthetic and cardiopulmonary effects of alfaxalone, alfaxalone-ketamine and alfaxalone-butorphanol-medetomidine in common marmosets.

METHODS

The following treatments were repeatedly administered to seven female common marmosets: Treatment A, alfaxalone (12 mg kg^-1 ) alone; treatment AK, alfaxalone (1 mg animal^-1 ) plus ketamine (2.5 mg animal^-1 ); treatment AMB, alfaxalone (4 mg kg^-1 ), medetomidine (50 µg kg^-1 ) plus butorphanol (0.3 mg kg^-1 ); and treatment AMB-Ati, AMB with atipamezole at 45 minutes.

RESULTS AND CONCLUSIONS

Marmosets became laterally recumbent and unresponsive for approximately 30 minutes in A and AK and for approximately 60 minutes in AMB. The animals showed rapid recovery following atipamezole injection in AMB-Ati. The decrease in heart rate and SpO₂ was significantly greater in AMB compared to A and AK. Oxygen supplementation, anaesthetic monitors and atipamezole should be available especially when AMB is administered.

Effect of Intramuscular Medetomidine Administration on Tear Flow in Rats

Medetomidine has been reported to decrease tear flow significantly in dogs, cats, and pigs when used as a sedative or analgesic; however, there are no such reports when it comes to rats. The present study aimed to investigate the effect of medetomidine on tear flow in rats. Medetomidine in doses of 50, 100, or 200 µg/kg or a physiological saline solution as the control, were administered intramuscularly to male Slc:Wistar/ST rats. After the administration of medetomidine, tear flow in both eyes was measured using a phenol red thread tear test. The area under the curve (AUC) of phenol red thread test values from baseline to 8 h was calculated. Data were plotted against the dose of medetomidine and simple linear regression analysis was performed. The effect of the drug on phenol red thread test values was considered dose-related when linear analysis yielded a significant relationship. In all medetomidine-treated groups, tear flow decreased significantly in both eyes after administration, while no significant changes were observed in either eye in the control group. The AUC values from baseline to 8 h after administration in groups treated with 100 and 200 µg/kg of medetomidine were significantly lower in both the left and right eyes compared to the control group. The linear regression of the AUC values was significant for both eyes. Our results indicated that the intramuscular administration of medetomidine in rats decreased tear flow significantly in a dose-dependent manner.

Use of midazolam in combination with medetomidine for premedication in healthy dogs

OBJECTIVE

To assess the sedative effects, propofol sparing properties and impact on quality of induction and intubation of intravenous (IV) medetomidine and midazolam administered consecutively at different doses compared to medetomidine alone in healthy dogs for premedication.

STUDY DESIGN

Prospective, randomized, blinded, clinical study.

ANIMALS

A total of 40 adult healthy client owned dogs, weighing 18 ± 7 kg (mean ± standard deviation).

METHODS

Dogs were assigned to four groups: medetomidine 15 μg kg^-1 (positive control group), medetomidine 10 μg kg^-1 and midazolam 0.2 mg kg^-1, medetomidine 5 μg kg^-1 and midazolam 0.3 mg kg^-1, and medetomidine 5 μg kg^-1 and midazolam 0.2 μg kg^-1. The same clinician assessed sedation after administration at T2.5 minutes and T5 minutes using a composite simple descriptive sedation scale ranging between 0 and 15 (0 = no sedation; 15 = profound sedation). The dose of propofol for induction, quality of induction, ease of intubation and any adverse events were recorded.

RESULTS

There was no significant difference in sedation scores between treatment groups at T2.5 minutes or T5 minutes (p = 0.82 and p = 0.63, respectively). Administration of midazolam in combination with medetomidine resulted in 71% of dogs displaying paradoxical behaviours (p < 0.0001) such as agitation, excitation, restlessness, aggression and vocalization, which was different from pre-sedation. Propofol requirement was not different between groups. Induction and tracheal intubation quality was smooth in all groups.

CONCLUSION

In healthy dogs, at the doses studied, the combination of medetomidine-midazolam administered IV for premedication provided moderate sedation but was associated with a high incidence of paradoxical behaviours. This drug combination IV is not recommended for premedication in healthy dogs.

Randomised clinical trial comparing clinically relevant sedation outcome measures in dogs after intramuscular administration of medetomidine in combination with midazolam or butorphanol for routine diagnostic imaging procedures

The aim of this study was to investigate the sedative effects of medetomidine in combination with midazolam or butorphanol for routine imaging procedures in dogs. Eighty client owned dogs were recruited in a prospective, randomised, blinded clinical study and randomly assigned to receive one of four treatments intramuscularly (IM): (1) 30μg/kg medetomidine (Med30); (2) 20μg/kg medetomidine combined with 0.3mg/kg butorphanol (Med20But0.3); (3) 20μg/kg medetomidine combined with 0.3mg/kg midazolam (Med20Mid0.3); and (4) 10μg/kg medetomidine combined with 0.3mg/kg midazolam (Med10Mid0.3). The level of sedation was evaluated using a composite sedation scale assessed by one investigator (0=no sedation, 15=profound sedation). The number of dogs deemed to be adequately clinically sedated and the dose of propofol administered as rescue sedation were recorded. Mean±standard deviation sedation scores at 30min after the commencement of treatment in the groups that received Med20But0.3 (9.8±4) and Med20Mid0.3 (8.9±4.4) were not statistically significantly different from each other, but were significantly different from the group receiving Med10Mid0.3 (5.6±3.6). Only Med20But0.3 was significantly associated with adequate clinical sedation, while Med10Mid0.3 was associated with 85% sedation failure. The rescue sedation dose of propofol (1.5±1mg/kg) for the Med10Mid0.3 group was significantly higher than for other treatments. A sedation score≥10 out of 15 was a satisfactory cut-off to predict adequate clinical sedation. In healthy dogs, the combination of medetomidine with midazolam did not provide comparable sedation to the same dose of medetomidine in combination with butorphanol in a clinical setting.

Blood biochemistry and hematological changes in rats after administration of a mixture of three anesthetic agents

Currently, given the concerns regarding animal welfare, it is required that anesthesia or analgesia be used during surgery in experimental animals. Therefore, it is important to understand how anesthesia affects the health conditions of experimental animals. In this study, rat blood biochemistry and hematological changes were examined following administration of a mixture of three anesthetic agents—medetomidine, midazolam and butorphanol (MMB). One of three MMB dose combinations was subcutaneously administered to rats. After 1 hr, rats were treated with atipamezole, to reverse the anesthetic effects. Blood biochemistry and hematological parameters were assessed at 1, 4 and 24 hr post-MMB treatment. We also recorded body weight and food intake at 0, 2, 4, 6 and 24 hr post-MMB administration. Following MMB administration, transient increases were observed in glucose (GLUC) levels, hematocrit (HCT) values and hemoglobin (HGB) levels, whereas transient decreases were observed in total protein (TP) content and white blood cell (WBC) counts. Most of these parameters returned to control values 24 hr following MMB administration. Additionally, body weight and food intake decreased in MMB-treated rats. In conclusion, intermediate and high doses of MMB changed some blood biochemistry and hematological parameters, body weight and food intake. In contrast, low-dose MMB did not cause these effects. Therefore, depending on the experimental design, MMB may influence the results of studies that use laboratory animals. Consequently, anesthetic agents used in laboratory animals should be chosen based on detailed knowledge of their pharmacological effects.

Evaluation of the use of midazolam as a co-induction agent with ketamine for anaesthesia in sedated ponies undergoing field castration

BACKGROUND

There are limited investigations comparing ketamine to a ketamine-midazolam co-induction.

OBJECTIVES

To compare quality and safety of general anaesthesia induced using ketamine alone with anaesthesia co-induced using ketamine and midazolam.

STUDY DESIGN

Randomised, double blinded, placebo controlled trial.

METHODS

After i.v. detomidine (20 μg/kg) thirty-eight ponies undergoing field castration received either 0.06 mg/kg (0.6 mL/50 kg) midazolam (group M) or 0.6 mL/50 kg placebo (group P) with 2.2 mg/kg ketamine i.v. for anaesthetic induction. Quality of anaesthetic induction, endotracheal intubation, surgical relaxation and recovery were scored using combinations of simple descriptive and visual analogue scales. Time of sedation, induction, start of endotracheal intubation, first movement, sternal recumbency and standing were recorded, as were time, number and total quantity of additional i.v. detomidine and ketamine injections. Cardiorespiratory variables were assessed every 5 min. Adverse effects were documented. Data were tested for normality and analysed with a mixed model ANOVA, Fisher's exact test, unpaired Students' t test and Wilcoxon Rank-sum as appropriate; P<0.05 was considered significant.

RESULTS

Group M had better scores for induction (P = 0.005), intubation (P<0.001) and surgical relaxation (P<0.001) and required fewer additional injections of detomidine and ketamine (P = 0.04). Time (minutes) from induction to first movement (P<0.001), sternal recumbency (P =< 0.001) and standing was longer (P = 0.05) in group M. Recoveries were uneventful with no difference in quality between groups (P = 0.78).

MAIN LIMITATIONS

Clinical study with noninvasive monitoring undertaken in field conditions.

CONCLUSIONS

Ketamine-midazolam co-induction compared to ketamine alone improved quality of induction, ease of intubation and muscle relaxation without impacting recovery quality.

Blood biochemical changes in mice after administration of a mixture of three anesthetic agents

Currently, from the viewpoint of animal welfare, anesthesia or analgesia is required during experimental procedures in animals that are likely to cause pain. A part of these anesthetics have been reported to influence a blood biochemical level. It is important for us to understand the effect of the anesthetic on blood biochemistry when we choose the anesthetic agent to be used in experiments. In this study, we examined the blood biochemical changes in mice after administration of a new mixture of three anesthetic agents −medetomidine / midazolam / butorphanol (MMB). We subcutaneously administered two dose combinations of MMB (0.45 / 6 / 7.5 and 0.9 / 12 / 15 mg/kg) in mice, followed by administration of atipamezole, for reversal of anesthetic effects, after 1 hr. Thereafter, blood biochemistry was assessed at 1, 4 and 24 hr after MMB administration. We observed that MMB administration caused a transient increase in blood sugar, inorganic phosphorus, potassium and creatine kinase levels. These, however, returned to the reference range 24 hr after MMB administration. In conclusion, MMB changes the levels of some blood biochemical parameters, but not to an extent that would threaten health. However, when using laboratory animals, this effect of MMB may influence the experimental results, depending on the experimental content. Hence, the choice of anesthetic agents used in laboratory animals should be based on detailed knowledge of their pharmacological effects.

The pharmacological effects of intramuscular administration of alfaxalone combined with medetomidine and butorphanol in dogs

The pharmacological effects of intramuscular (IM) administration of alfaxalone combined with medetomidine and butorphanol were evaluated in 6 healthy beagle dogs. Each dog received three treatments with a minimum 10-day interval between treatments. The dogs received an IM injection of alfaxalone 2.5 mg/kg (ALFX), medetomidine 2.5 µg/kg and butorphanol 0.25 mg/kg (MB), or their combination (MBA) 1 hr after the recovery from their instrumentation. Endotracheal intubation was attempted, and dogs were allowed to breath room air. Neuro-depressive effects (behavior changes and subjective scores) and cardiorespiratory parameters (rectal temperature, heart rate, respiratory rate, direct blood pressure, central venous pressure and blood gases) were evaluated before and at 2 to 120 min after IM treatment. Each dog became lateral recumbency, except for two dogs administered the MB treatment. The duration was longer in the MBA treatment compared with the ALFX treatment (100 ± 48 min vs 46 ± 13 min). Maintenance of the endotracheal tube lasted for 60 ± 24 min in five dogs administered the MBA treatment and for 20 min in one dog administered the ALFX treatment. Cardiorespiratory variables were maintained within clinically acceptable ranges, although decreases in heart and respiratory rates, and increases in central venous pressure occurred after the MBA and MB treatments. The MBA treatment provided an anesthetic effect that permitted endotracheal intubation without severe cardiorespiratory depression in healthy dogs.

Plasma concentrations and sedative effects of a dexmedetomidine, midazolam, and butorphanol combination after transnasal administration in healthy rabbits

Plasma concentrations of dexmedetomidine (D = 0.1 mg/kg), midazolam (M = 2 mg/kg), and butorphanol (B = 0.4 mg/kg) were analyzed by liquid chromatography-mass spectrometry (LC-MS/MS) after their simultaneous (DMB) transnasal (TN) administration to healthy rabbits. Time-dependent changes in sedation and antinociception were evaluated by measuring a sedation score based on rabbit's posture, loss of the righting, palpebral and pedal withdrawal reflexes and by instrumental monitoring of rectal temperature, heart rate, arterial blood pressure, pulse-oximetry, and capnometry. The peak plasma concentration (Cmax ) of each drug was reached within 5 min (Tmax ) from DMB-TN administration along with deep sedation and analgesia. Such effects subsided after 45 min into a moderate sedation and analgesia lasting for additional 15 min. All rabbits awakened spontaneously and uneventfully 90 min after DMB-TN administration. During the anesthetic procedure, arterial blood pressure markedly decreased and respiratory depression ensued requiring oxygen supplementation. The results of this study show that all three molecules of the DMB combination were absorbed through the TN route, inducing deep sedation and analgesia suitable for minor surgical procedures. Such combination should be used with caution in rabbits bearing cardiovascular or respiratory diseases because of its ability to induce hypotension and respiratory depression.

Novel and effective balanced intravenous-inhalant anaesthetic protocol in swine by using unrestricted drugs

Nowadays, because of increasing employment of swine for experimental studies and medical training, it is hopeful to investigate novel and effective anaesthetic protocols for preserving the animal welfare in medical investigation and concurrently improving the quality of research. Therefore, the aim of this study was to investigate a novel and effective anaesthetic protocol in swine undergoing major surgery, by translating know-how of combined anaesthesia from human protocols. Seven landrace swine were anaesthetized for three hours by a combined trial anaesthetic protocol (sedation: medetomidine, acepromazine, atropine and tramadol; induction: propofol, medetomidine and acepromazine; anaesthesia: isofluorane, propofol, medetomidine and acepromazine) and both clinical and haemodynamic parameters were compared with those of five swine anaesthetized with a control protocol (sedation: diazepam, ketamine and atropina; induction: diazepam and ketamine; anaesthesia: isofluorane). Both cardiac frequency (CF) and mean blood pressure (MBP) were significantly (P<0.05) more stable in trial protocol (CF: 78.3 ± 4.6-81.1 ± 5, MBP: 63.9 ± 10.7-96.4 ± 13.0) compared to control protocol (CF: 93.7 ± 5.5-102.5 ± 8.5, MBP: 71.0 ± 6.6-108.7 ± 7.2). The body temperature remained stable in trial protocol (°C: 36.9 ± 0.7-37.2 ± 0.3) compared to control anaesthesia (°C: 36.4 ± 0.3-37.3 ± 0.2, P<0.05). Haematosis improved undergoing combined anaesthesia (+2%, P<0.05) whereas did not change in control animals. There were no differences in respiratory rate between trial and control protocols. This study demonstrates that the proposed balanced intravenous-inhalant protocol permits to carry out a very effective, stable and safe anaesthesia in swine undergoing deep anaesthesia.

Anesthetic effect of a combination of medetomidine-midazolam-butorphanol in cynomolgus monkeys (Macaca fascicularis)

The anesthetic effect of a combination of medetomidine, midazolam and butorphanol (Me-Mi-Bu) was evaluated in healthy cynomolgus monkeys. The Me-Mi-Bu combination was intramuscularly administered as follows: Dose 1, Me 0.015 mg/kg-Mi 0.1 mg/kg-Bu 0.15 mg/kg; Dose 2, Me 0.02 mg/kg-Mi 0.15 mg/kg-Bu 0.2 mg/kg; and Dose 3, Me 0.04 mg/kg-Mi 0.3 mg/kg-Bu 0.4 mg/kg. The combination rapidly induced immobilization, and lateral recumbency was reached within 15 min. The duration of anesthesia for each dose administered was follows: Dose 1, 47 ± 27 min; Dose 2, 113 ± 31 min; and Dose 3, 190 ± 24 min. The anesthetic effect of the combination was abolished by the α2-adrenoceptor antagonist atipamezole. No marked changes in the levels of hematologic or serum biochemical parameters were noted in cynomolgus monkeys administered the combination plus atipamezole. Taken together, these results suggest that the Me-Mi-Bu combination exhibits reversible anesthetic effect and may be useful for studies involving cynomolgus monkeys.

Randomized clinical trial of the effects of a combination of acepromazine with morphine and midazolam on sedation, cardiovascular variables and the propofol dose requirements for induction of anesthesia in dogs

The present study evaluated the effects of acepromazine combined with midazolam and morphine on sedation and cardiovascular variables as well as the propofol dose required for induction of anesthesia in dogs compared with acepromazine-morphine or midazolam-morphine. Dogs were randomly assigned to receive an intramuscular administration of (1) acepromazine (0.05 mg/kg) with 0.5mg/kg of morphine (group AM, n=10), (2) midazolam (0.5mg/kg) with 0.5mg/kg of morphine (group MM, n=9), or (3) acepromazine with midazolam and morphine at the same doses (group AMM, n=10). After 30 min, sedation was assessed by a numeric descriptive scale (NDS, range 0-3) and a simple numerical scale (SNS, range 0-10). Dogs were then administered IV propofol to allow endotracheal intubation. NDS and SNS scores were significantly higher in the AMM than in the MM group (P<0.05). There was a trend towards more dogs presenting with intense sedation (NDS=3) in AMM (6/10 dogs) compared with AM (1/10 dogs) and MM (1/9 dogs) (P=0.057). The propofol dose required for induction of anesthesia was significantly lower in AMM (4.0mg/kg) compared with MM (6.0mg/kg, P<0.01) but not AM (4.6 mg/kg). Heart rate decreased in AM after treatment and after intubation. Blood pressure decreased in groups AM and AMM following treatment and in all groups after intubation. The combination AMM resulted in intense sedation more frequently than AM and MM, and provided the greatest sparing effect in the propofol dose. Administration of AM and AMM but not MM decreased blood pressure although hypotension was not recorded in healthy dogs.

Midazolam enhances the analgesic properties of dexmedetomidine in the rat

OBJECTIVE

To investigate the analgesic properties of different dose combinations of midazolam and dexmedetomidine administered intraperitoneally (IP) in the rat.

STUDY DESIGN

Prospective experimental trial.

ANIMALS

Seventy adult male Sprague Dawley rats weighing 250-300 g.

METHODS

Dexmedetomidine (D) 0.03, 0.06, 0.09, 0.12, 0.15, 0.18, 0.21 mg kg(-1) and midazolam (M) 5, 10, 25, 50 mg kg(-1) were administered IP, alone then in combinations ranging from 0.03 D:5 M to 0.18 D:30 M mg kg(-1). Analgesia was evaluated using the tail-flick test at time 0 (before injection), 15, 30, 45, 60 and 75 minutes.

RESULTS

Midazolam at all doses administered (5-50 mg kg(-1)) did not significantly change tail-flick latencies from baseline values whereas D showed clear dose-dependent increases in tail-flick latency for doses administered in the range of 0.03-0.18 mg kg(-1). Tail-flick latencies in rats administered D+M combinations were significantly greater than D alone (p<0.05).

CONCLUSIONS

A dose-related analgesic effect was demonstrated for D in the rat, which was enhanced by co-administration of M.

CLINICAL RELEVANCE

The combination of D+M administered IP to rats at doses of 0.12:20 and 0.09:15 mg kg(-1) was shown to be a good combination to provide sedation/analgesia with a duration of action greater than 60 minutes. The onset of sedation was rapid (1-3 minutes), and onset of profound analgesia was reached within 5-10 minutes.

Analgesia for the critically ill dog or cat: an update

Acute pain reliably accompanies severe illness and injury, and when sufficiently severe, it can complicate the recovery of critically ill patients. Because acute pain is closely tied to the neurologic process of nociception, pharmacologic therapy is often essential and effective. This update focuses on two methods of treatment of acute pain-local anesthetic infusion and continuous intravenous infusion of multimodal agents-that can be layered on top of standard care with other drugs.

Anesthetic and cardiopulmonary effects of intramuscular morphine, medetomidine, ketamine injection in dogs

OBJECTIVE

To determine the quality and duration of anesthesia and the cardiopulmonary effects of a morphine, medetomidine, ketamine (MMK) combination administered intramuscularly (IM) to dogs.

STUDY DESIGN

Descriptive injectable anesthetic protocol evaluation.

ANIMALS

Eight intact adult Beagle dogs: five males, three females.

METHODS

The electrocardiogram, heart rate, direct arterial blood pressure, and core body temperature were monitored in eight chronically instrumented dogs. Each dog received 0.2 mg kg(-1) morphine sulfate, 20 microg kg(-1) medetomidine hydrochloride, and 5 mg kg(-1) ketamine hydrochloride IM. Anesthetic and analgesic effects (clamping the tail and metatarsus) were categorized, and the times to lateral recumbency, orotracheal intubation, extubation, and sternal recumbency were recorded. Respiratory, cardiovascular, temperature, and acid-base variables were recorded 5 minutes before, and 3, 10, 20, 30, 45, 50, and 60 minutes after MMK. Atipamezole, 100 microg kg(-1) IM, was administered 60 minutes after MMK administration and data recorded 10 minutes later.

RESULTS

The onset of anesthesia was uneventful and rapid. Time to lateral recumbency was 7.1 +/- 4.1 minutes. The tracheas of four dogs were orally intubated in 5.1 +/- 0.8 minutes. After MMK administration most dogs were unresponsive to noxious stimulation from 20 to 60 minutes and heart rate, cardiac index and venous blood pH were significantly decreased from baseline values. Arterial blood pressure increased initially and then returned to baseline values. Times to extubation (four dogs) and return to sternal recumbency after atipamezole administration were 2.8 +/- 1.8 and 4.3 +/- 4.4 minutes, respectively.

CONCLUSION

The IM administration of MMK produced anesthesia and analgesia in Beagle dogs. Hemodynamic data were within accepted normal values. Atipamezole administration produced rapid return to consciousness in all dogs.

CLINICAL RELEVANCE

Morphine/medetomidine/ketamine may be used for minor medical and surgical procedures requiring short-term anesthesia and analgesia but it is not recommended for medical procedures that are painful.

Clinical efficacy and safety of dexmedetomidine and buprenorphine, butorphanol or diazepam for canine hip radiography

OBJECTIVES

To investigate the usefulness of dexmedetomidine for restraint and sedation during hip radiographic examination of hip-extended or stress-radiography views when combined with either buprenorphine, butorphanol or diazepam.

METHODS

One hundred and twenty-seven client-owned clinically healthy golden retrievers or rottweilers were enrolled in a clinical trial that compared hip-extended and PennHIP methods for diagnosing hip dysplasia and were randomly allocated to receive dexmedetomidine or medetomidine in combination with buprenorphine, butorphanol or diazepam. Subjective assessments were made for response to pain, response to noise, palpebral reflex, muscle tone and overall quality of sedation; non-invasive physiological variables were also recorded.

RESULTS

Overall quality of sedation was graded as good or excellent for dogs administered with a combination of butorphanol or diazepam. However, more dogs that received a combination involving buprenorphine had overall a relatively poorer quality of sedation and required additional administration of buprenorphine before the radiographic procedure could commence. Once sedated, clinically sufficient muscle relaxation accompanied by a very low proportion of dogs responding to pain or noise stimuli were observed in all treatment groups. Heart and respiratory rate, and procedure and recovery times were similar for all treatment groups, and no adverse events were observed during the study.

CLINICAL SIGNIFICANCE

Dexmedetomidine sedative protocols, particularly in combination with butorphanol and diazepam, can be used effectively and safely in dogs for radiographic procedures.

Effects of medetomidine-midazolam, acepromazine-butorphanol, and midazolam-butorphanol on induction dose of thiopental and propofol and on cardiopulmonary changes in dogs

OBJECTIVE

To evaluate dose-sparing effects of medetomidine-midazolam (MM), acepromazine-butorphanol (AB), and midazolam-butorphanol (MB) on the induction dose of thiopental and propofol and to examine cardiopulmonary changes in dogs.

ANIMALS

23 healthy Beagles.

PROCEDURE

Dogs were administered MM, AB, MB, or physiologic saline (0.9% NaCI) solution (PS) IM, and anesthesia was induced with thiopental or propofol. Cardiopulmonary measurements were obtained before and after administration of medication and 0, 5, 10, and 15 minutes after endotracheal intubation.

RESULTS

Induction doses were reduced significantly by preanesthetic administration of MM, AB, and MB (thiopental, 20, 45, and 46% after administration of PS; propofol, 42, 58, and 74% after administration of PS, respectively). Recovery time in dogs administered MM-thiopental or MM-propofol and AB-propofol were significantly prolonged, compared with recovery time in dogs administered PS-thiopental or PS-propofol. Relatively large cardiovascular changes were induced by administration of MM, which were sustained even after the induction of anesthesia. Administration of AB and MB induced cardiovascular changes during and immediately after endotracheal intubation that were significantly decreased by induction with thiopental or propofol. However, mild hypotension developed with AB-propofol. Apnea was observed in dogs administered MM during induction of anesthesia, but most respiratory variables did not change significantly.

CONCLUSIONS AND CLINICAL RELEVANCE

Preanesthetic medication with MM greatly reduced the anesthesia induction dose of thiopental and propofol but caused noticeable cardiopulmonary changes. Preanesthetic medication with AB and MB moderately reduced the induction dose of thiopental and propofol and amelio rated cardiovascular changes induced by these anesthetics, although AB caused mild hypotension.

Effects of medetomidine-midazolam, midazolambutorphanol, or acepromazine-butorphanol as premedicants for mask induction of anesthesia with sevoflurane in dogs

OBJECTIVE

To characterize the effects of medetomidine-midazolam, midazolam-butorphanol, or acepromazine-butorphanol as premedicants for mask induction of anesthesia with sevoflurane in dogs.

ANIMALS

10 healthy Beagles.

PROCEDURE

The following premedicants were administered intramuscularly: medetomidine-midazolam (20 microg/kg and 0.3 mg/kg, respectively), midazolam-butorphanol (0.1 and 0.2 mg/kg, respectively), and acepromazine-butorphanol (0.05 and 0.2 mg/kg, respectively). Saline (0.9% NaCI) solution (0.1 ml/kg) was administered intramuscularly as a control. Anesthesia was induced in each dog with sevoflurane in a 100% O2 at a flow rate of 4 L/min developed by a facemask. Vaporizer settings were increased by 0.8% at 15-second intervals until the value corresponding to 4.8% sevoflurane was achieved. Time to onset and cessation of involuntary movements, loss of the palpebral reflex, negative response to tail-clamp stimulation, and endotracheal intubation were recorded, and the cardiopulmonary variables were measured.

RESULTS

Mask induction with sevoflurane in dogs that received each premedicant resulted in a shorter induction time and milder changes in heart rate, mean arterial blood pressure, cardiac output, and respiratory rate, compared with mask induction without premedicants. Treatment with medetomidine-midazolam resulted in a shorter and smoother induction, compared with acepromazine-butorphanol or midazolam-butorphanol treatment, whereas the cardiovascular changes were greater. Cardiopulmonary variables of dogs during induction following treatment with acepromazine-butorphanol or midazolam-butorphanol were maintained close to the anesthetic maintenance values for sevoflurane, with the exception of mild hypotension that was observed in dogs following acepromazine-butorphanol treatment.

CONCLUSION AND CLINICAL RELEVANCE

In dogs use of premedicants provides a smoother and better quality mask induction with sevoflurane.

Anaesthetic and cardiopulmonary effects of balanced anaesthesia with medetomidine-midazolam and butorphanol in dogs

The anaesthetic and cardiopulmonary effects of combinations of medetomidine (Me), midazolam (Mi) and butorphanol (Bu) were evaluated in dogs. The characterization of anaesthetic effects was assessed using a scoring system. The combinations tested were 20 or 40 micrograms/kg Me and 0.5 mg/kg Mi (20Me-Mi or 40Me-Mi) followed by either an intravenous injection of physiological saline solution (PSS) or Bu (0.1 or 0.3 mg/kg). The mixture of Me and Mi was injected intramuscularly, followed 15 min later by an intravenous injection of Bu or PSS in all six groups. The combined Me-Mi induced deep sedation but not profound anaesthesia. The effect of the subsequent Bu administration was observed in the scores related to its analgesic effect. There were no significant differences between the two doses of Bu, following either 20Me-Mi or 40Me-Mi in the duration of anaesthesia, heart and respiratory rates, rectal temperature, and anaesthetic and analgesic scores except for palpebral reflex, and interdigital web clamping scores. Therefore, we concluded that the addition of 0.1 mg/kg Bu to Me-Mi elicits adequate anaesthesia with adequate analgesic effect, and side-effects such as bradycardia, hypertension, and slight respiratory acidosis in some dogs.

Sedative and cardiorespiratory effects of medetomidine, medetomidine-butorphanol, and medetomidine-ketamine in dogs

OBJECTIVE

To determine sedative and cardiorespiratory effects of i.m. administration of medetomidine alone and in combination with butorphanol or ketamine in dogs.

DESIGN

Randomized, crossover study.

ANIMALS

6 healthy adult dogs.

PROCEDURES

Dogs were given medetomidine alone (30 micrograms/kg [13.6 micrograms/lb] of body weight, i.m.), a combination of medetomidine (30 micrograms/kg, i.m.) and butorphanol (0.2 mg/kg [0.09 mg/lb], i.m.), or a combination of medetomidine (30 micrograms/kg, i.m.) and ketamine (3 mg/kg [1.36 mg/lb], i.m.). Treatments were administered in random order with a minimum of 1 week between treatments. Glycopyrrolate was given at the same time. Atipamezole (150 micrograms/kg [68 micrograms/lb], i.m.) was given 40 minutes after administration of medetomidine.

RESULTS

All but 1 dog (given medetomidine alone) assumed lateral recumbency within 6 minutes after drug administration. Endotracheal intubation was significantly more difficult when dogs were given medetomidine alone than when given medetomidine and butorphanol. At all evaluation times, percentages of dogs with positive responses to tail clamping or to needle pricks in the cervical region, shoulder region, abdominal region, or hindquarters were not significantly different among drug treatments. The Paco2 was significantly higher and the arterial pH and Pao2 were significantly lower when dogs were given medetomidine and butorphanol or medetomidine and ketamine than when they were given medetomidine alone. Recovery quality following atipamezole administration was unsatisfactory in 1 dog when given medetomidine and ketamine.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggested that a combination of medetomidine with butorphanol or ketamine resulted in more reliable and uniform sedation in dogs than did medetomidine alone.

Medetomidine-midazolam sedation in sheep

Seven sheep were sedated 3 times: with medetomidine (15 micrograms kg-1), with midazolam (0.1 mg kg-1) and with a combination of the drugs. All drugs were administered intravenously. Heart and respiratory rates were measured. Arterial blood samples were collected, and PaO2, PaCO2, pH, haemoglobin concentration and saturation, and base excess were determined. Systolic and mean arterial pressures were recorded before and after the treatment with medetomidine-midazolam. Midazolam increased the time of recumbency induced by medetomidine. After administration of midazolam alone, 4 of the 7 sheep were sedated and the other 3 were excited. Heart rate decreased after both medetomidine and medetomidine-midazolam. One sheep suffered a cardiac arrest after medetomidine-midazolam injection, and it required resuscitation. PaO2 and haemoglobin oxygen saturation decreased after medetomidine, and medetomidine-midazolam caused a marked hypoxaemia. PaCO2 increased after medetomidine, both alone and combined with midazolam, but arterial pH was within the reference values after all drug administrations. Systolic and mean arterial pressures decreased after medetomidine-midazolam. This study indicates that though in sheep midazolam potentiates the sedative effect of medetomidine, the combination of medetomidine and midazolam also reduces the in PaO2 and haemoglobin oxygen saturation more than medetomidine alone. The results indicate that a medetomidine-midazolam combination is unsafe for sheep at the doses studied.

Sedative and analgesic effects of medetomidine in beagle dogs infected and uninfected with heartworm

The sedative and analgesic effects of medetomidine were evaluated in heartworm-infected (HW+) and uninfected (HW-) beagle dogs by intravenous (IV) and intramuscular (IM) administration of 30 micrograms/kg and 40 micrograms/kg doses, respectively. Posture, response to noise and the pedal reflex were monitored. A procedure for mock radiographic positioning was performed to evaluate its overall clinical use. Observation times were 0, 15, 30, 60, 90, 120 and 180 min. In addition, the times from injection until the dog could not stand on its feet (down time), from lateral to sternal recumbency (sternal recumbency time), and from sternal recumbency to rising again (rising time) were also noted. Medetomidine produced rapid sedation and analgesia by both routes. Down times for the IM and IV routes were similar, which verified the manufacturer's recommended doses. The HW+ dogs had shorter down times, probably owing to increased blood flow to the brain caused by adrenergic alpha-2 activity. Sternal recumbency and rising times did not differ between the groups, suggesting a similar metabolism. Sedation and analgesia were adequate for performing the procedure in all dogs. HW- dogs showed less resistance to handling during the procedure than HW+ dogs. Overall, medetomidine seems to be a suitable agent for short-term chemical restraint in dogs, even with subclinical heartworm infestation.

A comparative study of medetomidine-butorphanol-ketamine and medetomidine-ketamine anaesthesia in dogs

The anaesthetic and cardiopulmonary effects of medetomidine (20 micrograms/kg)-butorphanol (0.1 mg/kg)-ketamine (MBK) (2.5, 5.0, 7.5 mg/kg) and medetomidine (40 micrograms/kg)-ketamine (5.0 mg/kg) (MK) were compared in dogs. The induction time (time from the initial injection of the sedative to lateral recumbency) by medetomidine-butorphanol (6.0 +/- 2.3 min) was significantly shorter than that by medetomidine alone (10.4 +/- 2.9 min). The duration of anaesthesia induced by MK was shorter than that by MBK2.5. The analgesic effects of MBK were more potent than those of MK. Mean arterial blood pressure increased significantly after administration of the sedatives, and then decreased to base-line value after the ketamine injection and remained stable throughout the experimental period. Respiratory rate decreased gradually after the administration of each sedative and was depressed until 60 min after the ketamine injection. MBK anaesthesia is effective and widely available for therapeutic procedures depending upon the selection of the ketamine dose.