Comparison of sedation scores and propofol induction doses in dogs after intramuscular administration of dexmedetomidine alone or in combination with methadone, midazolam, or methadone plus midazolam

Anaesthetic-sparing effect of the anxiolytic drug tasipimidine in Beagle dogs

OBJECTIVE

To evaluate the effect of oral tasipimidine on dog handling, ease of catheter placement and propofol and isoflurane requirements for anaesthesia.

STUDY DESIGN

Placebo-controlled, randomized, blinded, experimental trial.

ANIMALS

A group of seven adult Beagle dogs weighing (mean ± standard deviation) 13.1 ± 2.7 kg with a mean age of 18.6 ± 1 months.

METHODS

The dogs underwent four treatments before induction of anaesthesia with propofol. PP: placebo orally (PO) 60 minutes before induction of anaesthesia followed by placebo (NaCl 0.9%) intravenously (IV). TP: tasipimidine 30 μg kg-1 (PO) 60 minutes before induction of anaesthesia followed by placebo (NaCl 0.9%) IV. TMP: tasipimidine 30 μg kg-1 PO 60 minutes before induction of anaesthesia followed by methadone 0.2 mg kg-1 IV. TMPD: tasipimidine 30 μg kg-1 PO 60 minutes before induction of anaesthesia followed by methadone 0.2 mg kg-1 and dexmedetomidine 1 μg kg-1 IV followed by a dexmedetomidine constant rate infusion of 1 μg kg-1 hour-1. Sedation, response to catheter placement, intubation quality, time to loss of consciousness, time to intubation, required dose of propofol and minimum alveolar isoflurane concentration preventing motor movement (MACNM) were determined. A mixed-model analysis or the Friedman and Mann-Whitney test were used; p-value < 0.05.

RESULTS

Response to catheter placement did not differ between treatments. Tasipimidine alone reduced the propofol dose by 30%. Addition of methadone or methadone and dexmedetomidine reduced the propofol dose by 48% and 50%, respectively. Isoflurane MACNM was reduced by 19% in tasipimidine-medicated dogs, whereas in combination with methadone or methadone and dexmedetomidine, isoflurane MACNM was reduced by 35%.

CONCLUSIONS AND CLINICAL RELEVANCE

An anxiolytic dose of tasipimidine induced mild signs of sedation in dogs and reduced propofol and isoflurane requirements to induce and maintain anaesthesia, which needs to be considered in an anaesthetic plan.

Clinical evaluation of the sedative, antinociceptive and cardiorespiratory effects of intranasal dexmedetomidine combined with methadone in healthy dogs

In this prospective, randomised, blinded clinical study, we compared the sedative, antinociceptive and cardiorespiratory effects of intranasal (IN) dexmedetomidine at 5 μg/kg (diluted with 0.03 mL/kg NaCl 0.9%, DEX) with or without methadone (0.3 mg/kg; DEXMET), through a mucosal atomization device to one nostril in twenty healthy client-owned dogs. At 5-min intervals over 45 min, sedation score, onset, cardiopulmonary variables, mechanical nociceptive thresholds (MNTs) were assessed, also ease of administration, adverse effects, and response to IV catheterization. Statistical analysis employed t-test, the Mann-Whitney U, repeated measures ANOVA and Chi-square tests as appropriate (P < 0.05). Higher sedation ocurred in DEXMET (7 [5-10]) compared to DEX (5 [2-7]) from 15 to 30 min (P < 0.01, median [interquartile range]). Heart rate was lower in DEXMET (P < 0.01; 65% reduction vs. 41% in DEX, P = 0.001). The MNTs were higher in DEXMET than DEX from 15 to 45 min (P < 0.01), peaking at T30 (17.1 ± 3.8, DEXMET and 8.5 ± 5.4 N, DEX). No differences were observed in mean arterial blood pressure and respiratory rate. Intranasal administration was considered easy for 8 dogs per group. Reverse sneezing (8 dogs; P < 0.001), sialorrhea and retching (4 and 2 dogs, respectively) occurred in DEXMET. Response to catheterisation was lower in DEXMET than DEX (P = 0.039; 2 and 7 dogs, respectively). In conclusion, intranasal methadone (0.3 mg/kg) increased the sedative and antinociceptive effects produced by dexmedetomidine (5 μg/kg) in healthy dogs and resulted in lower heart rate.

Oxygen Reserve Index as a Tool to Monitor Four Techniques of Oxygen Supplementation at Different Flow Rates in Dogs Sedated with Dexmedetomidine and an Opioid

Respiratory dysfunction often decreases arterial oxygen content. Four common oxygen delivery techniques-flow-by, nasal prongs, a tight-vented mask, and a tight mask connected to a Venturi valve-were evaluated for their effectiveness in increasing the oxygen reserve index (ORi), a dimensionless index of oxygen content that provides additional information compared to traditional pulse oximetry (SpO2) during hyperoxia (PaO2 100-200 mmHg), and that ranges from 0 to 1. Thirty-two dogs sedated with dexmedetomidine and an opioid were evenly divided into four groups based on the technique for oxygen administration. Each dog received oxygen at 1, 2, and 3 L/min by a single technique, and the amount of inhaled oxygen (FiO2) was measured at the level of the cervical trachea. At each flow rate, ORi and SpO2 were recorded. The flow-by method minimally increased the FiO2, and ORi reached its highest value only in 3 out of 8 dogs at the maximum flow rate. Other methods exhibited direct correlations between the oxygen flow rate and ORi (p < 0.001). These methods effectively increased FiO2 and ORi, with over half of the values exceeding 40% and 0.4, respectively. The tight-vented mask showed variable increases in FiO2, ranging between 22 and 90%. Despite method-dependent variations, all devices increased SpO2 > 98% as the FiO2 increased (p = 0.002). In conclusion, nasal prongs and the mask connected to the Venturi valve showed the highest correlation between the oxygen flow rate and the ORi. These results suggest that using these two techniques in conjunction with ORI can help in optimizing oxygen therapy.

The effect of age on the induction dose of propofol for general anesthesia in dogs

OBJECTIVE

In people, the dose of propofol (DOP) required for procedural sedation and anesthesia decreases significantly with age. The objective of this study was to determine if the DOP required to perform endotracheal intubation decreases with age in dogs.

STUDY DESIGN

Retrospective case series.

ANIMALS

1397 dogs.

METHODS

Data from dogs anesthetized at referral center (2017-2020) were analyzed with three multivariate linear regression models with backward elimination using a combination of either absolute age, physiologic age, or life expectancy (ratio between age at the time of anesthetic event and expected age of death for each breed obtained from previous literature) as well as other factors as independent variables, and DOP as the dependent variable. The DOP for each quartile of life expectancy (<25%, 25-50%, 50-75%, 75-100%, >100%) was compared using one-way ANOVA. Significance was set at alpha = 0.025.

RESULTS

Mean age was 7.2 ± 4.1 years, life expectancy 59.8 ± 33%, weight 19 ± 14 kg, and DOP 3.76 ± 1.8 mg kg-1. Among age models, only life expectancy was a predictor of DOP (-0.37 mg kg-1; P = 0.013) but of minimal clinical importance. The DOP by life age expectancy quartile was 3.9 ± 2.3, 3.8 ± 1.8, 3.6 ± 1.8, 3.7 ± 1.7, and 3.4 ± 1.6 mg kg-1, respectively (P = 0.20). Yorkshire Terrier, Chihuahua, Maltese, mixed breed dogs under 10 kg, and Shih Tzu required higher DOP. Status of neutered male, ASA E, and Boxer, Labrador and Golden Retriever breeds decreased DOP, along with certain premedication drugs.

CONCLUSIONS AND CLINICAL RELEVANCE

In contrast to what is observed in people, an age cut-off predictive of DOP does not exist. Percentage of elapsed life expectancy along with other factors such as breed, premedication drug, emergency procedure, and reproductive status significantly alter DOP. In older dogs, the dose of propofol can be adjusted based on their elapsed life expectancy.

DEXMEDETOMIDINE ALONE OR COMBINED WITH MORPHINE FOR EPIDURAL ANESTHESIA IN BITCHES UNDERGOING ELECTIVE OVARIOHYSTERECTOMY

The purpose of this study was to assess perioperative analgesia provided by the combination of epidural dexmedetomidine and morphine in bitches undergoing elective ovariohysterectomy. Twenty-four bitches were included in the study and allocated into three groups: GM, morphine 0.1 mg/kg; GD, dexmedetomidine 2 µg/kg; and GDM, dexmedetomidine and morphine at the same doses. All solutions were diluted in saline to a total of 0.36 mL/kg. Heart rate (HR), respiratory rate (FR) and systolic blood pressure (SAP) were recorded prior to epidural analgesia (TB), immediately following epidural analgesia (TEA), at surgical incision (TSI), at the first ovarian pedicle clamping (TOP1), at the second pedicle clamping (TOP2), at uterine stump clamping (TUC), at the start of abdominal cavity closure (TSC) and at the end of skin closure (TEC). Rescue analgesia with fentanyl was administered at 2 µg/kg IV if nociception corresponding to a 20% increase of any cardiorespiratory variables was noted. Postoperative pain assessment was performed using a modified composite Glasgow pain scale along the first 6 hours following the end of surgery. Numeric data were compared using ANOVA for repeated measures followed by Tukey test and ovarian ligament relaxation was analyzed using chi-square test under 5% significance. No differences were found on FR among times or groups, although HR showed significant differences between GM and GD at TSI, TOP1, TOP2, TSC and TEC and between GM and GDM at TEA and TSI (significantly lower HR values recorded in dexmedetomidine groups). Differences among time points were found on HR between TB and TEA in GD and on PAS between TOP1 and TSC in GM and between TOP1 and TUC in GDM (p<0.05). Ovarian ligament relaxation was significantly more present in groups using dexmedetomidine, although the number of rescue analgesia administrations did not differ among groups. Kaplan-Meyer analysis failed to show significant differences on time of rescue analgesia administration among groups (p>0.05). In conclusion, the combination of epidural dexmedetomidine and morphine is a more interesting choice for elective ovariohysterectomy in bitches for producing analgesia comparable to that of each drug alone, with noticeable relaxation of ovarian ligaments and lesser cardiovascular consequences.

Sedative effects and changes in cardiac rhythm with intravenous premedication of medetomidine, butorphanol and ketamine in dogs

OBJECTIVE

To determine the sedative effects and characteristics of cardiac rhythm with intravenous (IV) premedication of medetomidine, butorphanol and ketamine in dogs.

STUDY DESIGN

Prospective, blinded, randomized clinical trial.

ANIMALS

A total of 116 client-owned healthy dogs undergoing elective surgery.

METHODS

Dogs were randomly allocated one of four groups: group M, medetomidine 5 μg kg^-1; group B, butorphanol 0.2 mg kg^-1; group MB, medetomidine 5 μg kg^-1 and butorphanol 0.2 mg kg^-1; or group MBK, medetomidine 5 μg kg^-1, butorphanol 0.2 mg kg^-1 and ketamine 1 mg kg^-1 IV. Sedation was assessed using a numerical descriptive scale. Heart rate (HR) and rhythm were monitored; propofol dose (mg kg^-1 IV) to allow orotracheal intubation was documented. Data were analysed using anova, accounting for multiple testing with the Tukey honest significant difference test.

RESULTS

Sedation scores varied significantly between all groups at all time points, except between groups MB and MBK at four time points. HR decreased in all groups: most in groups M and MB, least in group B. HR was initially higher in group MBK than in groups M and MB. Arrhythmias occurred in all groups: group B showed second-degree atrioventricular blocks occasionally, all other groups showed additionally ventricular escape complexes and bundle branch blocks. Dose of propofol required for orotracheal intubation was significantly higher in group B (5.0 ± 2.0 mg kg^-1) than in group M (2.6 ± 0.6 mg kg^-1). Although no difference could be demonstrated between groups MB (1.4 ± 0.6 mg kg^-1) and MBK (0.9 ± 0.8 mg kg^-1), both groups required significantly less propofol than group M.

CONCLUSION AND CLINICAL RELEVANCE

Medetomidine-based premedication protocols led to various bradyarrhythmias. Addition of subanaesthetic doses of ketamine to medetomidine-based protocols resulted in higher HRs, fewer bradyarrhythmias and fewer animals that required propofol for intubation without causing side effects in healthy dogs.

Comparison of the sedative and analgesic effects of butorphanol with acepromazine, midazolam, or dexmedetomidine following propofol induction and isoflurane maintenance in canines

Adequate sedation and excellent depth of analgesia were recorded in all the four groups after induction to the end of surgical procedure, however, significantly higher sedation score and depth of analgesia were observed in group D and significantly lower was observed in group A in comparison to other groups. Butorphanol with acepromazine, midazolam, or dexmedetomidine provides adequate sedation and analgesia in the dogs, before induction with propofol, so it made handling of the animals proper and safe before induction. Dexmedetomidine produces most profound sedation and analgesia followed by midazolam and acepromazine along with butorphanol.

Scoping review of quality of anesthetic induction and recovery scales used for dogs

OBJECTIVE

To compare, describe and assess the level of validation of all instruments measuring quality of induction and recovery from anesthesia in dogs.

DATABASES USED

A search was performed using the electronic database PubMed to find articles containing an induction quality scale, a recovery quality scale or both in dogs. Articles not directly accessible through PubMed were obtained through the Auburn University Library website and Google Scholar. The phrases 'induction scoring systems dogs', 'recovery scoring systems dogs', 'anesthetic induction score dogs', and 'anesthetic recovery score dogs' were used for searches using the 'best match search' function. The time frame searched was from 1980 to May 2020. The search was conducted from March 2020 to May 2020.

CONCLUSIONS

A thoroughly tested and validated scale for measuring the quality of induction and recovery does not exist in the current veterinary literature. A large disagreement exists between studies on the use of induction and recovery scales, and many have reported inconsistent results with current instruments. It is recommended that an induction and recovery scale intended for wide-scale use be constructed and tested extensively for psychometric validation and reliability.

Sedative and analgesic effects of two subanaesthetic doses of ketamine in combination with methadone and a low dose of dexmedetomidine in healthy dogs

OBJECTIVE

To evaluate the sedative, analgesic and recovery characteristics of two subanaesthetic ketamine doses in combination with dexmedetomidine and methadone for intramuscular sedation in healthy Beagles.

STUDY DESIGN

Randomized, blinded, crossover, experimental study.

ANIMALS

Six healthy adult Beagles.

METHODS

Dogs were randomly given three treatments: dexmedetomidine (3 μg kg^-1) and methadone (0.3 mg kg^-1) combined with ketamine at 1 and 2 mg kg^-1 (K1 and K2, respectively) or saline (K0), intramuscularly. Sedation score, response to tail clamping and rectal temperature were recorded at baseline, 5, 15, 25, 35, and 45 minutes posttreatment. Pulse rate (PR), respiratory rate, oxygen haemoglobin saturation and noninvasive blood pressure were also recorded at baseline and every 5 minutes until 45 minutes posttreatment. Onset and duration of recumbency, response to venous catheterization and recovery quality were also assessed. Sedation and physiological variables were compared between treatments and within treatments compared to baseline (analysis of variance). Nonparametric data were analysed with the Friedman and Cochran's Q tests; p < 0.050.

RESULTS

Increased sedation was found at 15 (K0 and K1), 25 (all treatments) and 35 (K1) minutes compared with baseline. Sedation score, onset (3-12 minutes) and duration of recumbency (29-51 minutes) were similar between treatments. Recovery quality was considered acceptable in all cases. Response to tail clamping was inconsistent within treatments with no differences between them. None of the dogs responded to venous catheterization. There were no differences between treatments in physiological variables, except for PR which was higher in K2 than in K0. Oxygen supplementation was required in five and three dogs administered saline and ketamine, respectively.

CONCLUSIONS AND CLINICAL RELEVANCE

The addition of 1 or 2 mg kg^-1 of ketamine to methadone and dexmedetomidine combination did not enhance sedation or antinociception in healthy dogs. Recovery quality was unaffected.

Postoperative evaluation of analgesia promoted by the use of dexmedetomidine alone and associated with morphine as an intramuscular pre-anesthetic medication in bitches submitted for ovariohysterectomy

Abstract This study aimed to evaluate the postoperative analgesic efficacy of dexmedetomidine alone and when associated with morphine in patients under general inhalational anesthesia with isoflurane and undergoing elective ovariohysterectomy (OH). Twenty healthy bitches were selected via physical and laboratory examinations. Prior to the study, they underwent a 24-h period of adaptation to the environment and observers. They were then randomly divided into two groups: the dexmedetomidine group receiving a dose of 10 μg/kg, and dexmedetomidine group (10 μg/kg) associated with morphine receiving a dose of 0.3 mg/kg, administered via the intramuscular route. Thereafter, patients were induced with propofol and maintained with isoflurane diluted in 100% oxygen administered through a calibrated vaporizer. To verify postoperative analgesia, pain assessments were performed using the modified Glasgow (EGM) and Melbourne (EM) scales. For sedation assessment, the Dobbins scale was used at different times: before the administration of pre-anesthetic medication (T0) and at another six times in the postoperative period, 1 (T1), 2 (T2), 4 (T3), 8 (T4), 12 (T5), and 24 (T6) h after orotracheal extubation. No statistical differences were observed between groups in the scales according to Dunn’s Kruskal-Wallis post hoc test, and between the times a statistical difference was noticed by the Friedman test (p<0.05) for the EGM and EM scale scores, but there was no need for analgesic rescue. Therefore, we found that isolated dexmedetomidine and morphine produced adequate analgesic effects in the postoperative period of bitches submitted for OH.

Oral Transmucosal or Intramuscular Administration of Dexmedetomidine-Methadone Combination in Dogs: Sedative and Physiological Effects

Simple Summary

During the last decade, new alternative non-invasive administration routes for drug delivery have gained interest in veterinary medicine. The administration of drugs via the oral transmucosal route is non-invasive, painless, easy to perform, and generally well tolerated. Furthermore, it avoids gastric acid degradation typical of oral administration. All these characteristics contribute to make this administration route very attractive, especially for veterinary patients who are difficult to inject, fearful, or anxious. In contrast, intramuscular injection is associated with pain and requires more invasive restraint, potentially incrementing patients’ discomfort. The aim of this study was to assess and compare the sedative and clinical effects of a dexmedetomidine–methadone combination following either oral transmucosal and intramuscular administration in healthy dogs and to record any possible adverse effects following each administration route. The present study suggests that oral transmucosal administration of dexmedetomidine and methadone combination provided a satisfactory level of sedation, allowing safe handling of the patients with less pronounced cardiorespiratory effects. Indeed, thanks to the lesser impact on the cardiac function, it could be considered as a useful option for those patients difficult to restrain in which cardiovascular stability should be preserved.

Abstract

The aim of this study was to compare the sedative and physiological effects following either oral transmucosal (OTM) or intramuscular administration of dexmedetomidine–methadone combination in healthy dogs. Thirty dogs were randomly assigned to receive a dexmedetomidine–methadone combination either by the OTM (n = 15) or intramuscular (n = 15) route. Sedation was scored 10, 20, and 30 min after drugs administration. Heart rate (HR), non-invasive blood pressure (NIBP), respiratory rate (f_R), and body rectal temperature were recorded before drugs administration and then every 10 min for 30 min. Propofol dose required for orotracheal intubation was recorded. Sedation scores increased over time within both groups with higher values in intramuscular group (p < 0.05). Within each group, HR decreased significantly compared with baseline (p < 0.001) and was significantly lower in intramuscular group compared with the OTM group (p < 0.001). In both groups, NIBP increased significantly compared with baseline (p < 0.05). In the intramuscular group, f_R was lower compared with the OTM group at all the observational time points (p < 0.001). Propofol dose was lower in the intramuscular group (p < 0.05). Compared to intramuscular dexmedetomidine–methadone, OTM combination produced lower but effective sedation in healthy dogs.

Efeitos cardiovasculares da medetomidina e cetamina em Puma concolor e tempo de recuperação após aplicação de ioimbina ou atipamezole

RESUMO O objetivo deste estudo foi avaliar as alterações cardiorrespiratórias causadas pela medetomidina associada à cetamina, e o tempo de recuperação após aplicação intramuscular de atipamezole ou ioimbina em Puma concolor. Para isso, foi realizada a aplicação de medetomidina (100µg/kg) associada à cetamina (5mg/kg) em 11 onças-pardas, sendo os parâmetros cardiorrespiratórios registrados a cada 15 minutos, durante 90 minutos de avaliação. Em seguida, a anestesia foi revertida com aplicação intramuscular de ioimbina (0,4mg/kg; n=5) ou atipamezole (0,25mg/kg; n=6), sendo analisado o tempo até a recuperação. Dos parâmetros cardiorrespiratórios avaliados, houve diferença apenas na frequência respiratória (entre os momentos 60 e 90 minutos), estando esta, todavia, dentro do intervalo de referência para a espécie. Além disso, verificou-se tempo para decúbito esternal significativamente menor nos animais do grupo atipamezole (18±7 minutos), quando comparado ao grupo ioimbina (36±17 minutos), entretanto o tempo de recuperação completa foi estatisticamente igual entre os dois reversores analisados. Assim, a associação anestésica promoveu anestesia eficiente, segura e de rápida indução em onças-pardas, permitindo a imobilização dos animais durante os 90 minutos de avaliação, sem a ocorrência de complicações. Ao se comparar a reversão anestésica com atipamezole e ioimbina, observou-se equivalência dos fármacos no tempo de recuperação completa dos animais.

Sedative effects of two doses of alfaxalone in combination with methadone and a low dose of dexmedetomidine in healthy Beagles

OBJECTIVE

To evaluate the sedative effects of two doses of alfaxalone when added to a combination of dexmedetomidine and methadone injected intramuscularly (IM) in healthy Beagles.

STUDY DESIGN

Randomized, blinded, crossover, experimental study.

ANIMALS

A group of six adult Beagles.

METHODS

Dogs were sedated on three different occasions with IM dexmedetomidine (3 μg kg^-1) and methadone (0.3 mg kg^-1) combined with two doses of alfaxalone (0.5 and 1 mg kg^-1; A0.5 and A1, respectively) or saline (A0). Quality of sedation, response to tail clamping and rectal temperature were recorded at baseline, 5, 15, 25, 35 and 45 minutes. Pulse and respiratory rates, oxygen saturation of haemoglobin (SpO₂) and noninvasive blood pressure (NIBP) were recorded every 5 minutes. Onset of sedation and duration of recumbency, response to venous catheterization and recovery quality were assessed. Physiological variables (analysis of variance) were analysed between treatments and within treatments compared with baseline (Student t test). Nonparametric data were analysed using Friedman and Cochran's Q tests. Significance was p < 0.05.

RESULTS

Sedation scores were significantly higher when alfaxalone was co-administered (area under the curve; p = 0.024, A0.5; p = 0.019, A1), with no differences between doses. Onset of sedation was similar, but duration of recumbency was longer in A0.5 than in A0 [median (minimum-maximum), 43 (35-54) versus 30 (20-47) minutes, p = 0.018], but not in A1. Response to venous catheterization and tail clamping, and quality of recovery (acceptable) presented no differences between treatments. A decrease in all physiological variables (compared with baseline) was observed, except for NIBP, with no differences between treatments. All dogs required oxygen supplementation due to reduced SpO₂.

CONCLUSIONS AND CLINICAL RELEVANCE

Adding alfaxalone to methadone and dexmedetomidine enhanced sedation and duration of recumbency. Although cardiopulmonary depression was limited, oxygen supplementation is advisable.

Evaluation of anesthesia produced by ketofol in acepromazine- or medetomidine-sedated dogs

Objective

A randomized, blinded clinical study was conducted to evaluate ketofol (Ketamine + Propofol combination) anesthesia in 12 entire male mongrel dogs sedated with either acepromazine (ACP) or medetomidine.

Materials and Methods

Group A (6) dogs were pre-medicated with ACP and Group B (6) dogs with medetomidine. Anesthesia was induced and maintained using ketofol (ketamine and propofol). Routine open pre-scrotal castration was performed. Sedation score and ease of arousal were assessed and recorded. Duration and depth of anesthesia were evaluated using apnea and the absence of palpebral and pedal reflexes, attempts to stand up, and muscle tremors and post-operative pain. Simple statistics were compared using Student t-test and Mann-Whitney test (p < 0.05).

Results

Medetomidine-sedated dogs had higher sedation scores compared to ACP-sedated dogs. Medetomidine-ketofol produced significantly (p < 0.05) longer duration of anesthesia (24.5 ± 3.1 min) compared to ACP-ketofol (10.0 ± 4.4 min). Sixty-seven percent of dogs anesthetized with ACP-ketofol required top up with ketofol to complete the castration. However, none of the Med-ketofol anesthetized dogs required top up. Med-ketofol produced a more profound depth of anesthesia and smoother recovery from anesthesia compared to ACP-ketofol. Med-ketofol (median score 6) attained better overall post-operative analgesia compared to ACP-ketofol (median score 7), though not statistically significant (p = 0.25). Although both protocols provided adequate anesthesia for castration, top up was required to complete the operation in more than half of ACP-ketofol anesthetized dogs, making Med-ketofol a better protocol.

Conclusion

The study recommends the use of Med-ketofol anesthesia for castration in a dog, and post-operative analgesia to be administered with either protocol, but more so in ACP-ketofol anesthetized dogs undergoing castration.

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.

Evaluation of injectable anaesthesia with five medetomidine-midazolam based combinations in Egyptian fruit bats (Rousettus aegyptiacus)

Egyptian fruit bats are increasingly used as model animals in neuroscience research. Our aim was to characterize suitable injectable anaesthesia for this species, possibly replacing inhalant anaesthesia, thus minimizing occupational health hazards. Eight bats were randomly assigned by a crossover design for subcutaneously administered combinations of medetomidine-midazolam with: saline (MM-Sal), ketamine (MM-Ket), fentanyl (MM-Fen), morphine (MM-Mor), or butorphanol (MM-But). The anaesthetic depth and vital signs were monitored at baseline and every 10 min until bats recovered. If after 180 min the bats did not recover, atipamezole was administered. Mean induction times were 7–11.5 min with all combinations. Twitching during induction was common. All combinations produced anaesthesia, with significantly decreased heart rate (from 400 to 200 bpm) and respiratory rate (from 120–140 to 36–65 rpm). Arrhythmia and irregular breathing patterns occurred. MM-Fen, MM-Mor, and MM-But depressed respiration significantly more than MM-Sal. Time to first movement with MM-Ket and MM-But lasted significantly longer than with MM-Sal. Recovery time was significantly shorter in the MM-Sal (88 min) in comparison to all other treatments, and it was significantly longer in the MM-But (159 min), with atipamezole administered to four of the eight bats. In conclusion, all five anaesthetic protocols are suitable for Egyptian fruit bats; MM-Ket produces long anaesthesia and minimal respiratory depression, but cannot be antagonized completely. MM-Fen, MM-Mor, and MM-But depress respiration, but are known to produce good analgesia, and can be fully antagonized. Administration of atipamezole following the use of MM-But in Egyptian fruit bats is recommended.

Postinduction apnoea in dogs premedicated with acepromazine or dexmedetomidine and anaesthetized with alfaxalone or propofol

OBJECTIVE

To compare incidence and duration of postinduction apnoea in dogs after premedication with methadone and acepromazine (MA) or methadone and dexmedetomidine (MD) followed by induction with propofol (P) or alfaxalone (A).

STUDY DESIGN

Prospective, randomized clinical trial.

ANIMALS

A total of 32 American Society of Anesthesiologists class I dogs (15 females, 17 males), aged between 4 months and 4 years, weighing between 3 and 46 kg.

METHODS

Dogs were randomly allocated to be administered MA+P, MA+A, MD+P or MD+A (methadone 0.5 mg kg^-1 and acepromazine 0.05 mg kg^-1 or dexmedetomidine 5 μg kg^-1). Induction agents were administered intravenously via syringe driver (P at 4 mg kg^-1 minute^-1 or A at 2 mg kg^-1 minute^-1) until successful endotracheal intubation and the endotracheal tube connected to a circle system with oxygen flow at 2 L minute^-1. Oxygen saturation of haemoglobin (SpO₂), end tidal partial pressure of carbon dioxide and respiratory rate were monitored continuously. If apnoea (≥ 30 seconds without breathing) occurred, the duration until first spontaneous breath was measured. If SpO₂ decreased below 90% the experiment was stopped and manual ventilation initiated. Data were analysed with general linear models with significance set at p ≤ 0.05.

RESULTS

There was no statistical difference in the incidence (11 of 16 dogs in A groups and 12 of 16 dogs in P groups), or mean ± standard deviation duration (A groups 125 ± 113 seconds, P groups 119 ± 109 seconds) of apnoea. The SpO₂ of one dog in the MD+P group decreased below 90% during the apnoeic period.

CONCLUSIONS AND CLINICAL RELEVANCE

Propofol and alfaxalone both cause postinduction apnoea and the incidence and duration of apnoea is not influenced by the use of acepromazine or dexmedetomidine in premedication. Monitoring of respiration is recommended when using these premedication and induction agent combinations.

Effect of environmental noise and music on dexmedetomidine-induced sedation in dogs

Background

Previous studies in human patients suggest depth of sedation may be affected by environmental noise or music; however, related data in domestic animals is limited. The objective of the current study was to investigate the effect of noise and music on dexmedetomidine-induced (DM- 10 µg/kg, IM) sedation in 10 dogs.

Methods

In a crossover design, post-DM injection dogs were immediately subjected to recorded human voices at either 55–60 decibel (dB) (Noise 1) or 80–85 dB (Noise 2); classical music at 45–50 dB (Music); or background noise of 40–45 dB (Control+). Control− included IM saline injection and exposure to 40–45 dB background noise. Sedation was assessed via monitoring spontaneous behavior and accelerometry (delta-g) throughout three 20-min evaluation periods: baseline, noise exposure, and post-treatment. Sedation was further assessed during two restraint tests at 30 min (R1) and 40 min (R2) post-injection. A mixed model for crossover design was used to determine the effect of noise exposure and time on either spontaneous behavior scores or delta-g. The restraint scores were analyzed using a two-way repeated measures ANOVA.

Results

Spontaneous behavior scores indicated less sedation during Noise 2 compared to Control+ (P = 0.05). R2 restraint scores for all DM treatments except Noise 2 indicated significantly higher sedation than Control− [C+ (P = 0.003), M (P = 0.014) and N1 (P = 0.044)].

Discussion

Results suggest that the quality of sedation is negatively impacted by high-intensity noise conditions (80–85 dB), but exposure to music did not improve sedation in this population of research dogs.