The impact of vatinoxan on microcirculation after intramuscular coadministration with medetomidine in Beagle dogs – a blinded cross-over study

Equivalence in intradermal reactions to histamine and compound 48/80 in dogs before and after sedation with dexmedetomidine or a 1:20 combination of medetomidine and vatinoxan

BACKGROUND

Intradermal allergen testing (IDAT) is commonly used to formulate allergen-specific immunotherapy, a pillar treatment for canine atopic dermatitis. Many sedatives have shown histaminergic or anti-histaminergic effects and thus been deemed unsuitable for IDAT.

OBJECTIVE

The goal of this study was to determine whether, in healthy dogs, dexmedetomidine (Dexdomitor) or a 1:20 combination of medetomidine and vatinoxan (Zenalpha) will affect intradermal reactions compared to unsedated dogs.

ANIMALS

Ten privately owned healthy dogs were enrolled in this equivalence study.

MATERIALS AND METHODS

Wheal formation was subjectively and objectively assessed in conscious then sedated dogs. Dogs were randomly sedated with either Dexdomitor (dexmedetomidine [0.5 mg/m2]) or Zenalpha (medetomidine [1 mg/m2/vatinoxan] 20 mg/m2) intramuscularly. Once sedated, five 10-fold histamine (100-0.01 μg/mL) and compound 48/80 (200-0.02 μg/mL) dilutions were intradermally injected into the lateral thorax. The study was repeated on the opposite side with the alternative sedation 1 week later. Quality of sedation, cardiorespiratory function and rectal temperature were recorded every 5 min.

RESULTS

There was no difference in the median values of the reactions with either sedative when compared to unsedated dogs. Dexdomitor and Zenalpha achieved an equivalence in both subjective and objective scoring systems for all concentrations tested. A faster median time to sedation (10 vs. 18 min, p = 0.013) was seen with Zenalpha compared to Dexdomitor. Although both sedatives depressed the cardiovascular function, such parameters were less affected by Zenalpha than by Dexdomitor (p ≤ 0.001).

CONCLUSIONS AND CLINICAL RELEVANCE

Owing to the lack of effects on wheal formation, both sedatives are appropriate for sedating dogs undergoing IDAT. Although, such results should be validated in allergic dogs. Zenalpha may induce more rapid and reliable sedation than Dexdomitor.

CARDIORESPIRATORY EFFECTS OF VATINOXAN IN BLESBOK (DAMALISCUS PYGARGUS PHILLIPSI) IMMOBILIZED WITH THIAFENTANIL-MEDETOMIDINE

Combinations of a low dose of opioid, such as thiafentanil, and a high dose of medetomidine, are increasingly being used for immobilization of African ungulates. Both drugs can have undesirable cardiorespiratory effects. In this study we assessed whether vatinoxan, a peripherally acting alpha2-adrenergic receptor antagonist, can be used to alleviate some of these effects without affecting the immobilization quality. Eight healthy, female, boma-confined blesbok (Damaliscus pygargus phillipsi), weighing a mean (SDtion) of 56.8 (4.4) kg, were immobilized twice in a randomized cross-over study with a 2-wk washout period using (1) 0.5 mg thiafentanil + 1.5 mg medetomidine (TM), (2) TM + vatinoxan: 0.5 mg thiafentanil + 1.5 mg medetomidine + 15 mg vatinoxan per milligram medetomidine (total of 22.5 mg, administered intramuscularly at 10 min post recumbency). Heart rate, respiratory rate, rectal temperature, oxygen saturation (SpO2), arterial blood pressure, and sedation scores from 1 to 5 (1 = limited effect; 5 = excessively deep) were measured every 5 min. Arterial blood gases (PaO2 and PaCO2) were measured at 10, 15, 25, and 35 min postrecumbency and the alveolar--arterial oxygen gradient (P[A-a]O2) was calculated. Induction times and immobilization quality did not differ between groups. The heart rate was significantly higher and the mean arterial pressure significantly lower in blesbok after receiving vatinoxan. All animals were hypoxemic and there were no significant differences in the respiratory rates, PaO2, PaCO2, SpO2, or P(A-a)O2 gradients at any time point. Although vatinoxan did not improve respiratory variables and blood oxygenation in these animals, the change in cardiovascular variables may suggest that it improves tissue perfusion, a positive outcome that requires further investigation.

Comparison between dexmedetomidine and a combination of medetomidine-vatinoxan on muscle tissue saturation in privately-owned adult dogs undergoing intradermal testing

This double-blinded randomized cross-over study compared the muscle tissue oxygen saturation (StO2) measured at the sartorius muscle after intramuscular (IM) injection of dexmedetomidine hydrochloride (HCl) and co-administration of vatinoxan HCl, a peripheral α2-adrenoceptor antagonist, and medetomidine HCl in healthy privately-owned dogs undergoing intradermal testing (IDAT). After written owner consent, dogs received IM injections of either dexmedetomidine (0.5 mg/m2, DEX) or medetomidine (1 mg/m2) and vatinoxan (20 mg/m2) (MVX). Once sedated, intradermal injections were given on the lateral thorax of each dog, and the study was repeated with the alternative sedation on the opposite side one week later. At the end of the study, sedation was reversed with atipamezole (5 mg/m2). Depth of sedation, cardiopulmonary parameters, StO2, and rectal temperature were recorded and compared using mixed effect linear models (α ≤ 0.05). MVX achieved adequate sedation faster [median (interquartile range), 10 (8, 10) minutes] compared to DEX [18 (15, 22) minutes; hazard ratio = 7.44, p = 0.013), with higher scores at 10- and 15-min post-injection. StO2 was significantly reduced for 30 min after injection (p < 0.001), independently of the treatment (p = 0.68). Cardiopulmonary variables favored MVX. However, higher heart rate did not correlate with improved StO2. There was no difference in either subjective or objective assessment of the wheal size between sedations (p > 0.05). Both sedation protocols, MVX and DEX, were deemed suitable for IDAT in dogs, with mild reductions in StO2 measured at the sartorius muscle that were not significantly different between treatments.

Effects of tasipimidine premedication with and without methadone and dexmedetomidine on cardiovascular variables during propofol-isoflurane anaesthesia in Beagle dogs

OBJECTIVE

To evaluate cardiovascular effects of oral tasipimidine on propofol-isoflurane anaesthesia with or without methadone and dexmedetomidine at equianaesthetic levels.

STUDY DESIGN

Prospective, placebo-controlled, blinded, experimental trial.

ANIMALS

A group of seven adult Beagle dogs weighing (mean ± standard deviation) 12.4 ± 2.6 kg and a mean age of 20.6 ± 1 months.

METHODS

The dogs underwent four treatments 60 minutes before induction of anaesthesia with propofol. PP: placebo orally and placebo (NaCl 0.9%) intravenously (IV); TP: tasipimidine 30 μg kg-1 orally and placebo IV; TMP: tasipimidine 30 μg kg-1 orally and methadone 0.2 mg kg-1 IV; and TMPD: tasipimidine 30 μg kg-1 orally with methadone 0.2 mg kg-1 and dexmedetomidine 1 μg kg-1 IV followed by 1 μg kg-1 hour-1. Isoflurane in oxygen was maintained for 120 minutes at 1.2 individual minimum alveolar concentration preventing motor movement. Cardiac output (CO), tissue blood flow (tbf), tissue oxygen saturation (stO2) and relative haemoglobin content were determined. Arterial and mixed venous blood gases, arterial and pulmonary artery pressures and heart rate (HR) were measured at baseline; 60 minutes after oral premedication; 5 minutes after IV premedication; 15, 30, 60, 90 and 120 minutes after propofol injection; and 30 minutes after switching the vaporiser off. Data were analysed by two-way anova for repeated measures; p < 0.05.

RESULTS

Tasipimidine induced a significant 20-30% reduction in HR and CO with decreases in MAP (10-15%), tbf (40%) and stO2 (43%). Blood pressure and oxygenation variables were mainly influenced by propofol-isoflurane-oxygen anaesthesia, preceded by short-lived alterations related to IV methadone and dexmedetomidine.

CONCLUSIONS AND CLINICAL RELEVANCE

Tasipimidine induced mild to moderate cardiovascular depression. It can be incorporated into a common anaesthetic protocol without detrimental effects in healthy dogs, when anaesthetics are administered to effect and cardiorespiratory function is monitored.

Haemodynamic effects of labetalol in isoflurane-anaesthetized dogs that received dexmedetomidine: A randomized clinical trial

OBJECTIVE

To test whether labetalol improved cardiovascular function in anaesthetized dogs injected with dexmedetomidine.

STUDY DESIGN

Prospective, randomized, blinded, clinical trial.

ANIMALS

A group of 20 healthy client-owned dogs undergoing ovariohysterectomy.

METHODS

Each dog received dexmedetomidine (5 μg kg-1) and methadone (0.2 mg kg-1) intramuscularly. General anaesthesia was induced with propofol and maintained with isoflurane in oxygen. All dogs were mechanically ventilated, and epidural anaesthesia with lidocaine was performed. Standard anaesthetic monitoring, invasive blood pressure, oesophageal Doppler and near-infrared tissue perfusion/oxygenation were applied. Peak velocity (PV), mean acceleration and stroke distance (SD) from the oesophageal Doppler were recorded. Arterial elastance (Ea) was calculated. Tissue oxygenation (rStO2) was also recorded. Prior to surgery, animals received either 0.1 mg kg-1 of labetalol intravenously (IV) over 60 seconds or the equivalent volume of saline. Data were recorded for 20 minutes. Age, weight and propofol dose were compared with a Wilcoxon rank-sum test. The effects of time, treatment and their interaction with haemodynamic and perfusion variables were analysed with mixed-effect models and Tukey's post hoc tests.

RESULTS

Significant effects of the interaction between treatment and time were observed whereby heart rate (HR) was higher in dogs given labetalol (p = 0.01), whereas arterial blood pressure and Ea were lower (p < 0.01). Similarly, PV, SD and rStO2 were higher in the labetalol group, and significant effects were detected for the interaction between treatment and time (p < 0.01).

CONCLUSIONS AND CLINICAL RELEVANCE

Labetalol at a dose of 0.1 mg kg-1 IV in dogs under general anaesthesia and administered a pre-anaesthetic medication of dexmedetomidine produced mild vasodilation (reduction of Ea), resulting in an increase in HR and left ventricular outflow. Although labetalol could be an effective option to achieve haemodynamic optimization after dexmedetomidine-induced vasoconstriction, future studies are needed to assess long-term effects.

Evaluation of cardiovascular effects of intramuscular medetomidine and a medetomidine-vatinoxan combination in Beagle dogs: A randomized blinded crossover laboratory study

OBJECTIVE

To compare the cardiovascular effects of a combination of medetomidine and vatinoxan (MVX) versus medetomidine (MED) alone administered intramuscularly (IM) and to determine whether heart rate (HR) can be used as a surrogate for cardiac output (CO) after the use of medetomidine with or without vatinoxan.

STUDY DESIGN

A randomized, blinded, experimental, crossover study.

ANIMALS

A group of eight healthy Beagle dogs aged 4.6 (2.3-9.4) years and weighing 12.9 (9-14.7) kg, median (range).

METHODS

Each dog was injected with 1 mg m-2 medetomidine with or without 20 mg m-2 vatinoxan IM with a washout period of 7 days. Cardiovascular data and arterial and mixed venous blood gas samples were collected at baseline, 5, 10, 15, 20, 35, 45, 60, 90 and 120 minutes after treatment administration. CO was measured at all time points via thermodilution. Differences between treatments, period and sequence were evaluated with repeated measures analysis of covariance and the relationship between HR and CO was assessed with a repeated measures analysis of variance; p values < 0.05 were deemed significant.

RESULTS

The CO was 47-96% lower after MED than after MVX (p < 0.0001). Increases in systemic, pulmonary arterial and right atrial pressures and oxygen extraction ratio were significantly higher after MED than after MVX (all p < 0.0001). HR was significantly lower after MED and the linear relationship to CO was significant (p < 0.0001).

CONCLUSIONS AND CLINICAL RELEVANCE

Overall, MED affected the cardiovascular system more negatively than MVX, and the difference in cardiovascular function between the treatments can be considered clinically relevant. HR was linearly related to CO, and decreases in HR reflected cardiac performance for dogs sedated with medetomidine with or without vatinoxan.

Assessment of the microvascular perfusion using sidestream dark-field imaging in healthy newborn foals

BACKGROUND

Different methods to measure tissue perfusion are available in equine neonatology, but they are not representative of microvascular derangements.

OBJECTIVE

To evaluate the feasibility of the sidestream dark-field (SDF) capillaroscopy to visualize the capillary microvasculature in conscious newborn foals, the differences between two imaging sites and times of measurements, and the measurements' reproducibility.

METHODS

Seventeen healthy newborn foals were enrolled. Three sites at the upper and lower lip mucosa were assessed by SDF, using a hand-held capiscope, at 24 h and at 4-5 days after birth. Videos were assessed independently by two observers for quality and for semiquantitative calculation of microvascular parameters, including vascular density (VD), microvascular flow index (MFI), proportion of perfused vessels (PPV), and functional capillary density (FCD). Data were analyzed using unpaired and paired Student's T-tests to assess differences between sites and time-points. Bland-Altman plots and intraclass correlation coefficient (ICC) were used to assess measurement reproducibility.

RESULTS

Differences were found between the upper and the lower lip for VD at both 24 h and 4-5 days, and for FCD at 24 h, and between the two time-points for PPV at the lower lip. ICC for measurement reproducibility was good for all parameters (0.64-0.79) for the lower lip, and was good for VD and FCD (0,76-0,79) and fair to moderate for MFI and PPV (0.31-0.41) for the upper lip.

CONCLUSIONS

Measurement of the capillary microvasculature is feasible in the conscious newborn foal. The lower lip has the best measurement reproducibility. Further investigations are warranted in cardiovascularly compromised cases, particularly in septic foals.