The cardiopulmonary effects of a peripheral alpha-2-adrenoceptor antagonist, MK-467, in dogs sedated with a combination of medetomidine and butorphanol

The impact of intravenous medetomidine and vatinoxan on echocardiographic evaluation of dogs with stage B1 mitral valve disease

INTRODUCTION/OBJECTIVE

The purpose of this study was to investigate the echocardiographic effects of intravenous medetomidine and vatinoxan in dogs with stage B1 mitral valve disease. We hypothesised medetomidine-vatinoxan would reduce the need for manual restraint during echocardiography without producing detrimental cardiovascular effects or echocardiographic changes.

ANIMALS

Twelve client-owned dogs with stage B1 mitral valve disease.

METHODS

A transthoracic echocardiographic examination was performed before and after sedation with intravenous medetomidine (10 μg/kg) and vatinoxan (200 μg/kg). Vital parameters were also recorded, and the level of sedation was assessed subjectively. The data were analysed with Student's t-tests with an alpha level of <0.05.

RESULTS

End-systolic volume and left ventricular systolic diameter increased (from 0.89 ± 0.19 mL/kg to 1.13 ± 0.29 mL/kg and 0.96 ± 0.12 cm to 1.10 ± 0.10 cm, respectively) and ejection fraction (from 66.33 ± 4.0% to 56.23 ± 9.54%) and fractional shortening (from 36.13 ± 5.42% to 27.24 ± 5.6%) decreased significantly after sedation. End diastolic volume, left ventricular diastolic diameter, and left atrial size remained statistically unchanged, while aortic (from 1.34 ± 0.2 m/s to 0.99 ± 0.14 m/s) and pulmonic (from 0.94 ± 0.16 m/s to 0.66 ± 0.15 m/s) velocities decreased significantly. No dogs had a mean arterial pressure below 65 mmHg. Sedation enabled echocardiographic examination without manual restraint. No adverse effects were observed with the dose studied.

CONCLUSIONS

Echocardiographic parameters were not completely comparable with the baseline values, which should be taken into consideration when evaluating dogs sedated with intravenous medetomidine-vatinoxan.

Effects of vatinoxan in rats sedated with a combination of medetomidine, midazolam and fentanyl

BACKGROUND

Alpha2-adrenoceptor agonists (α2-agonists) are widely used in animals as sedatives and for pre-anaesthetic medication. Medetomidine has often been given subcutaneously (SC) to rats, although its absorption rate is slow and the individual variation in serum drug concentrations is high via this route. In addition, α2-agonists have various effects on metabolic and endocrine functions such as hypoinsulinaemia, hyperglycaemia and diuresis. Vatinoxan is a peripherally acting α2-adrenoceptor antagonist that, as a hydrophilic molecule, does not cross the blood-brain barrier in significant quantities and thus alleviates peripheral cardiovascular effects and adverse metabolic effects of α2-agonists. Aim of this study was to evaluate the effects of vatinoxan on sedation, blood glucose concentration, voiding and heart and respiratory rates and arterial oxygen saturation in rats sedated with subcutaneous medetomidine, midazolam and fentanyl.

RESULTS

Onset of sedation and loss of righting reflex occurred significantly faster with vatinoxan [5.35 ± 1.08 (mean ± SD) versus 12.97 ± 6.18 min and 6.53 ± 2.18 versus 14.47 ± 7.28 min, respectively]. No significant differences were detected in heart and respiratory rates and arterial oxygen saturation between treatments. Blood glucose concentration (18.3 ± 3.6 versus 11.8 ± 1.2 mmol/L) and spontaneous urinary voiding [35.9 (15.1-41.6), range (median) versus 0.9 (0-8.0) mL /kg/min] were significantly higher without vatinoxan.

CONCLUSIONS

Acceleration of induction of sedation, alleviation of hyperglycaemia and prevention of profuse diuresis by vatinoxan may be beneficial when sedating rats for clinical and experimental purposes with subcutaneous medetomidine, midazolam and fentanyl.

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.

Effects of vatinoxan in dogs premedicated with medetomidine and butorphanol followed by sevoflurane anaesthesia: a randomized clinical study

OBJECTIVE

To investigate effects of vatinoxan in dogs, when administered as intravenous (IV) premedication with medetomidine and butorphanol before anaesthesia for surgical castration.

STUDY DESIGN

A randomized, controlled, blinded, clinical trial.

ANIMALS

A total of 28 client-owned dogs.

METHODS

Dogs were premedicated with medetomidine (0.125 mg m^-2) and butorphanol (0.2 mg kg^-1) (group MB; n = 14), or medetomidine (0.25 mg m^-2), butorphanol (0.2 mg kg^-1) and vatinoxan (5 mg m^-2) (group MB-VATI; n = 14). Anaesthesia was induced 15 minutes later with propofol and maintained with sevoflurane in oxygen (targeting 1.3%). Before surgical incision, lidocaine (2 mg kg^-1) was injected intratesticularly. At the end of the procedure, meloxicam (0.2 mg kg^-1) was administered IV. The level of sedation, the qualities of induction, intubation and recovery, and Glasgow Composite Pain Scale short form (GCPS-SF) were assessed. Heart rate (HR), respiratory rate (f_R), mean arterial pressure (MAP), end-tidal concentration of sevoflurane (Fe'Sevo) and carbon dioxide (Pe'CO₂) were recorded. Blood samples were collected at 10 and 30 minutes after premedication for plasma medetomidine and butorphanol concentrations.

RESULTS

At the beginning of surgery, HR was 61 ± 16 and 93 ± 23 beats minute^-1 (p = 0.001), and MAP was 78 ± 7 and 56 ± 7 mmHg (p = 0.001) in MB and MB-VATI groups, respectively. No differences were detected in f_R, Pe'CO₂, Fe'Sevo, the level of sedation, the qualities of induction, intubation and recovery, or in GCPS-SF. Plasma medetomidine concentrations were higher in group MB-VATI than in MB at 10 minutes (p = 0.002) and 30 minutes (p = 0.0001). Plasma butorphanol concentrations were not different between groups.

CONCLUSIONS AND CLINICAL RELEVANCE

In group MB, HR was significantly lower than in group MB-VATI. Hypotension detected in group MB-VATI during sevoflurane anaesthesia was clinically the most significant difference between groups.

Cardiovascular effects of intravenous vatinoxan in wild boars (Sus scrofa) anaesthetised with intramuscular medetomidine-tiletamine-zolazepam

BACKGROUND

The potent sedative medetomidine is a commonly used adjunct for the immobilisation of non-domestic mammals. However, its use is associated with pronounced cardiovascular side effects, such as bradycardia, vasoconstriction and decreased cardiac output. We investigated the effects of the peripherally-acting alpha-2-adrenoceptor antagonist vatinoxan on cardiovascular properties in medetomidine-tiletamine-zolazepam anaesthetised wild boar (Sus scrofa).

METHODS

Twelve wild boars, anaesthetised twice with medetomidine (0.1 mg/kg) and tiletamine/zolazepam (2.5 mg/kg) IM in a randomised, crossover study, were administered (0.1 mg/kg) vatinoxan or an equivalent volume of saline IV (control). Cardiovascular variables, including heart rate (HR), mean arterial blood pressure (MAP), pulmonary artery pressure (PAP), pulmonary artery occlusion pressure (PAOP) and cardiac output (CO), were assessed 5 min prior to vatinoxan/saline administration until the end of anaesthesia 30 min later.

RESULTS

MAP (p < 0.0001), MPAP (p < 0.001) and MPAOP (p < 0.0001) significantly decreased from baseline after vatinoxan until the end of anaesthesia. HR increased significantly (p < 0.0001) from baseline after vatinoxan administration. However, the effect on HR subsided 3 min after vatinoxan. All variables remained constant after saline injection. There was no significant effect of vatinoxan or saline on CO.

CONCLUSION

Vatinoxan significantly reduced systemic and pulmonary artery hypertension, induced by medetomidine in wild boar.

The impact of vatinoxan on medetomidine-ketamine-midazolam immobilization in Patagonian maras (Dolichotis patagonum)

OBJECTIVE

To compare cardiovascular and ventilatory effects, immobilization quality and effects on tissue perfusion of a medetomidine-ketamine-midazolam combination with or without vatinoxan (MK-467), a peripherally acting α₂-adrenoceptor antagonist.

STUDY DESIGN

Randomized, blinded, crossover study.

ANIMALS

A group of nine healthy Patagonian maras (Dolichotis patagonum).

METHODS

Maras were immobilized twice with: 1) medetomidine hydrochloride (0.1 mg kg^-1) + ketamine (5 mg kg^-1) + midazolam (0.1 mg kg^-1) (MKM) + saline or 2) MKM + vatinoxan hydrochloride (0.8 mg kg^-1), administered intramuscularly. Drugs were mixed in the same syringe. At 20, 30 and 40 minutes after injection, invasive blood pressure, heart rate, respiration rate, end-tidal CO₂, haemoglobin oxygen saturation, and muscle oxygenation were measured, arteriovenous oxygen content difference was calculated. Muscle tone, jaw tone, spontaneous blinking and palpebral reflex were evaluated. Times to initial effect, recumbency, initial arousal and control of the head were recorded. Paired t test, Wilcoxon matched-pairs signed rank test and analysis of variance were used to compare protocols; (p < 0.05).

RESULTS

Vatinoxan significantly reduced systolic (p = 0.0002), mean (MAP; p < 0.0001) and diastolic (p < 0.0001) arterial blood pressures between 20 and 40 minutes. MAPs at 30 minutes (mean ± standard deviation) with MKM and MKM + vatinoxan were 105 ± 12 and 71 ± 14 mmHg, respectively. Without vatinoxan, four animals were hypertensive (MAP > 120 mmHg), whereas with vatinoxan, four animals were hypotensive (MAP < 60 mmHg). Muscle and jaw tone were significantly more frequently present with MKM (both p = 0.039). Other measurements did not significantly differ between protocols.

CONCLUSIONS AND CLINICAL RELEVANCE

In Patagonian maras, vatinoxan attenuated the increase in blood pressure induced by medetomidine. Muscle and jaw tone were more frequently present with MKM, indicating that quality of immobilization with vatinoxan was more profound.

Effects of intramuscular vatinoxan (MK-467), co-administered with medetomidine and butorphanol, on cardiopulmonary and anaesthetic effects of intravenous ketamine in dogs

OBJECTIVE

To investigate the impact of intramuscular (IM) co-administration of the peripheral α₂-adrenoceptor agonist vatinoxan (MK-467) with medetomidine and butorphanol prior to intravenous (IV) ketamine on the cardiopulmonary and anaesthetic effects in dogs, followed by atipamezole reversal.

STUDY DESIGN

Randomized, masked crossover study.

ANIMALS

A total of eight purpose-bred Beagle dogs aged 3 years.

METHODS

Each dog was instrumented and administered two treatments 2 weeks apart: medetomidine (20 μg kg^-1) and butorphanol (100 μg kg^-1) premedication with vatinoxan (500 μg kg^-1; treatment MVB) or without vatinoxan (treatment MB) IM 20 minutes before IV ketamine (4 mg kg^-1). Atipamezole (100 μg kg^-1) was administered IM 60 minutes after ketamine. Heart rate (HR), mean arterial (MAP) and central venous (CVP) pressures and cardiac output (CO) were measured; cardiac (CI) and systemic vascular resistance (SVRI) indices were calculated before and 10 minutes after MVB or MB, and 10, 25, 40, 55, 70 and 100 minutes after ketamine. Data were analysed with repeated measures analysis of covariance models. A p-value <0.05 was considered statistically significant. Sedation, induction, intubation and recovery scores were assessed.

RESULTS

At most time points, HR and CI were significantly higher, and SVRI and CVP significantly lower with MVB than with MB. With both treatments, SVRI and MAP decreased after ketamine, whereas HR and CI increased. MAP was significantly lower with MVB than with MB; mild hypotension (57-59 mmHg) was recorded in two dogs with MVB prior to atipamezole administration. Sedation, induction, intubation and recovery scores were not different between treatments, but intolerance to the endotracheal tube was observed earlier with MVB.

CONCLUSIONS AND CLINICAL RELEVANCE

Haemodynamic performance was improved by vatinoxan co-administration with medetomidine-butorphanol, before and after ketamine administration. However, vatinoxan was associated with mild hypotension after ketamine with the dose used in this study. Vatinoxan shortened the duration of anaesthesia.

Diaphragmatic dysfunction in dogs with cervical spinal disorders before and after surgery using fluoroscopy, motion-mode ultrasound and radiography was not different than a group of control dogs

Cervical spinal disorders can lead to life-threatening respiratory complications. Diaphragmatic dysfunction is attributed to spinal cord morbidity secondary to cervical myelopathy or decompressive surgical intervention. The purpose of this observational case-control study was to determine the frequency of diaphragmatic dysfunction in dogs with cervical spinal disorders and a control group, the strength of association between cervical myelopathies and decompressive surgery with diaphragm paresis, and the agreement between and clinical usefulness of fluoroscopy, motion-mode ultrasonography, and radiography for diagnosing diaphragmatic dysfunction. Thirty-five client-owned dogs were recruited with 14 control dogs and 21 test dogs. Dogs were evaluated for the presence of diaphragmatic dysfunction using radiography, M-mode ultrasonography, and fluoroscopy before and after an anesthetic or surgical event. Diaphragmatic dysfunction was observed more frequently in dogs with cervical spinal disease prior to surgery (8/21; 38.1%) compared to control dogs (3/14; 21.4%) but was not statistically significant (P = .30). The occurrence of diaphragmatic dysfunction did not significantly increase following surgical decompression in either group. There was no to slight agreement between all imaging modalities. Most dogs with diaphragmatic dysfunction were asymptomatic. Diaphragmatic dysfunction was not statistically associated with cervical myelopathy or decompressive surgery. Ultrasonography and radiography were not useful diagnostic tests for determining diaphragmatic dysfunction in asymptomatic dogs when compared to fluoroscopy.

Cardiovascular effects of premedication with medetomidine alone and in combination with MK-467 or glycopyrrolate in dogs subsequently anesthetized with isoflurane

OBJECTIVE To compare cardiovascular effects of premedication with medetomidine alone and with each of 3 doses of MK-467 or after glycopyrrolate in dogs subsequently anesthetized with isoflurane. ANIMALS 8 healthy purpose-bred 5-year-old Beagles. PROCEDURES In a randomized crossover study, each dog received 5 premedication protocols (medetomidine [10 μg/kg, IV] alone [MED] and in combination with MK-467 at doses of 50 [MMK50], 100 [MMK100], and 150 [MMK150] μg/kg and 15 minutes after glycopyrrolate [10 μg/kg, SC; MGP]), with at least 14 days between treatments. Twenty minutes after medetomidine administration, anesthesia was induced with ketamine (0.5 mg/kg, IV) and midazolam (0.1 mg/kg, IV) increments given to effect and maintained with isoflurane (1.2%) for 50 minutes. Cardiovascular variables were recorded, and blood samples for determination of plasma dexmedetomidine, levomedetomidine, and MK-467 concentrations were collected at predetermined times. Variables were compared among the 5 treatments. RESULTS The mean arterial pressure and systemic vascular resistance index increased following the MED treatment, and those increases were augmented and obtunded following the MGP and MMK150 treatments, respectively. Mean cardiac index for the MMK100 and MMK150 treatments was significantly greater than that for the MGP treatment. The area under the time-concentration curve to the last sampling point for dexmedetomidine for the MMK150 treatment was significantly lower than that for the MED treatment. CONCLUSIONS AND CLINICAL RELEVANCE Results indicated concurrent administration of MK-467 with medetomidine alleviated medetomidine-induced hemodynamic changes in a dose-dependent manner prior to isoflurane anesthesia. Following MK-467 administration to healthy dogs, mean arterial pressure was sustained at acceptable levels during isoflurane anesthesia.