Comparative Effect of Epidural Administration of Xylazine or Dexmedetomidine on Echocardiographic Dimensions and Cardiac Indices in Clinically Healthy Donkeys (Equus asinus)

Journal Pre-proof Comparative effect of epidural administration of xylazine or dexmedetomidine on echocardiographic dimensions and cardiac indices in clinically healthy donkeys (Equus asinus) Hussam M.M. Ibrahim, Khaled S. Abouelnasr, Mohamed A. Hamed, Rasha Eltayesh, Sabry A. El-khodery PII:

S0737-0806(19)30631-8

DOI:

https://doi.org/10.1016/j.jevs.2019.102882

Reference:

YJEVS 102882

To appear in:

Journal of Equine Veterinary Science

Received Date: 3 July 2019 Revised Date:

28 November 2019

Accepted Date: 2 December 2019

Please cite this article as: Ibrahim HMM, Abouelnasr KS, Hamed MA, Eltayesh R, El-khodery SA, Comparative effect of epidural administration of xylazine or dexmedetomidine on echocardiographic dimensions and cardiac indices in clinically healthy donkeys (Equus asinus), Journal of Equine Veterinary Science (2020), doi: https://doi.org/10.1016/j.jevs.2019.102882. This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2019 Elsevier Inc. All rights reserved.

Comparative effect of epidural administration of xylazine or dexmedetomidine on

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echocardiographic dimensions and cardiac indices in clinically healthy donkeys

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(Equus asinus)

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Hussam M. M. Ibrahim1*, Khaled S. Abouelnasr2, Mohamed A. Hamed3, Rasha

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Eltayesh4, Sabry A. El-khodery1

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Department of Internal Medicine and Infectious Diseases, Faculty of Veterinary

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Medicine, Mansoura University, Mansoura 35516, Egypt

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2

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Department of Surgery, Anesthesiology and Radiology, Faculty of Veterinary

Medicine, Mansoura University, Mansoura 35516, Egypt

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3

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Department of Surgery, Anesthesiology and Radiology, Faculty of Veterinary

Medicine, Aswan University, Egypt

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4

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Department of Pharmacology, Faculty of Veterinary Medicine, Mansoura University,

Mansoura 35516, Egypt

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*Correspondence: Hussam M. M. Ibrahim, Department of Internal Medicine, Infectious

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and Fish Diseases, Faculty of Veterinary Medicine, Mansoura University, Mansoura

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35516, Egypt, E-mail: [email protected]

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Abstract

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The aim of the current study was to assess and compare the changes of the

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echocardiographic dimensions and cardiac function indices following epidural injection

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of xylazine or dexmedetomidine in clinically healthy donkeys. In an experimental

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prospective randomized cross-over study, ten healthy adult donkeys were injected with

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saline solution, xylazine (0.20 mg kg-1), and dexmedetomidine (0.005 mg kg1) into the

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epidural space between the 2nd and 3rd coccygeal vertebrae. Echocardiographic

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measurements were assessed using a 2 – 3.9 MHz sector transducer, at the left para-

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costal ultrasonographic window, at zero, 15, 30, 60, 90, 120 and 180 minutes post-

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administration. Epidural injection of xylazine or dexmedetomidine produced moderate

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sedation, complete bilateral perineal analgesia, and mild ataxia. There was a significant

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(p < 0.05) decrease in the inter ventricular septum thickness at end systole (IVSTs) 60

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minutes, stroke volume (SV) 30 to 120 minutes, fractional shortening (FS) 120 minutes,

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and ejection fraction (EF) 90 to 120 minutes after administration of xylazine or

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dexmedetomidine when compared with saline solution. Left ventricular end diastolic

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volume (EDV) was significantly (p < 0.05) increased 60 minutes after epidural injection

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of dexmedetomidine compared with xylazine and saline solution. There was a

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significant (p < 0.05) increase in the left ventricular internal diameter at end diastole

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(LVIDd) 90 to 120 minutes and left ventricular end systolic volume (ESV) 60 to 180

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minutes after administration of xylazine or dexmedetomidine in comparison with saline

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solution. In conclusion, epidural use of xylazine or dexmedetomidine in donkeys

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induced mild and transient effect on echocardiographic dimensions as well as cardiac

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function. Therefore, care should be taken when such medications are to be administered

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into the epidural space in donkeys with a pre-anesthetic cardiovascular compromise.

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Keywords: Xylazine; Dexmedetomidine; Epidural Route; Echocardiography; Donkeys. 2

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1. Introduction

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Caudal epidural analgesia has been developed in large animals for diagnostic and

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surgical purposes in the perineal region in standing animals. It provides complete loss of

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sensory and motor function of the tail and perineum in standing horses, and avoids many

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of the risks of general anesthesia and recumbency. Its use provides a long duration of

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anesthesia and analgesia which will be more suitable for procedures that require a longer

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period [1].

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Alpha-2 agonist medications are labeled for use in equine and are given IV, IM, and

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epidurally for their systemic and analgesic effects with minimal cardio-respiratory

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adverse impact. Their cardiovascular effects include initiation of transient hypertension

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followed by delayed hypotension, second degree atrioventricular block, bradycardia, and

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diminished cardiac output [2,3], while their respiratory effects include decreased

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respiratory rate with a variable influence on tidal volume [2]. Epidural use of xylazine in

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horses (0.2 mg kg-1) [4–5] and in donkeys (0.17 mg kg-1) [6] isn't associated with any

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cardiopulmonary changes. In dogs, epidural use of xylazine (0.1 – 0.4 mg Kg-1) or

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dexmedetomidine (0.003 – 0.006 mg Kg-1) induces transient bradycardia and elevation

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of blood pressure [7]. In buffalo-calves and cows, epidural xylazine (0.05 mg kg-1)

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induced significant decrease in mean arterial pressure as reported previously by Singh et

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al [8] and St Jean et al. [9], respectively. Therefore, epidural use of xylazine should be

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avoided in cattle with cardiac disease and/or pulmonary disease, because of its potent

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cardiopulmonary depressant effect [9]. In sheep, dexmedetomidine reduces blood

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pressure after intrathecal or epidural injection within 1 minute without effect on the

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heart rate, but not after intravenous injection [10].

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Intravenous administration of alpha-2 agonists in horses, including xylazine and

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romifidine affects the cardiovascular system promoting a reduction of the diastolic

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arterial blood pressure, heart rate, cardiac contractility, EF%, and FS% with reduced

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cardiac output [11,12]. Moreover, echocardiographic examination of sedated horses with

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intravenous injection of detomidine (0.01 mg kg-1) or romifidine (0.04 mg kg-1) revealed

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their pronounced effect on the cardiac function as well as systolic cardiac dimensions

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[13]. In dogs, intravenous administration of dexmedetomidine increases the left

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ventricular internal diameter at end diastole (LVIDd) and at end systole (LVIDs), left

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ventricular end diastolic volume (EDV), and left ventricular end systolic volume (ESV).

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Meanwhile, it reduces ejection fraction (EF), fractional shortening (FS) and cardiac

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output [14].

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In equine practice, for a reliable assessment of cardiovascular structure and

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function, as well as to verify the effect of various medicaments on heart size and

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performance, echocardiography is a safe validated non-invasive technique that is

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routinely used [15,16]. Thus, echocardiography is able to detect the drugs-induced

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cardiovascular effects and to evaluate the compromised degree of cardiac function,

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providing a signal about the efficacy, safety, and viability of such drugs and the potential

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risks of their use.

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Some studies have suggested that anaesthetic agents administered in the caudal

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epidural space can diffuse cranially toward the thoracic region with a resultant mild

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cardiopulmonary depression [17,18]. Furthermore, epidural injection of analgesics may

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provide a systemic effect following its absorption to the systemic circulation through the

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epidural vein and lymphatic [19,20]. Accordingly, our hypothesis is that epidural

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injection of xylazine or dexmedetomidine may alter the echocardiographic dimensions

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and cardiac function indices. Therefore, the aim of the current investigation was to

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assess and compare the changes of the echocardiographic dimensions and cardiac

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function indices following epidural injection of xylazine or dexmedetomidine in

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clinically healthy donkeys. The analgesic impacts of the used medicaments in the

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current study have been detailed previously by Hamed et al. [21].

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2. Materials and methods

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2.1. Animals

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Ten adult healthy donkeys (Equus asinus) (five mares and five geldings) aged

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(Mean ± SD) 8.5 ± 1.3 years old and weighed (Mean ± SD) 210.0 ± 27.45 kg were

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selected randomly for this study. To certify that all donkeys are fit and free from any

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cardiovascular illnesses prior to the trials, they were clinically examined and were

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exposed to cardiac check, including the heart rate and rhythm, intensity of the heart

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sounds, and abnormal heart sounds [22]. A non-invasive echocardiographic examination

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was performed for each animal and all the echocardiographic dimensions and cardiac

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function indices were assessed to be compatible as zero time. The exclusion criteria

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were any systemic illness, tachycardia, arrhythmia, audible heart murmurs, and any

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cardiac abnormality detected during echocardiography. Donkeys were kept in the animal

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house of the Veterinary Teaching Hospital, Faculty of veterinary Medicine, Mansoura

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University, Mansoura, Egypt. All donkeys were sustained on a maintenance balanced

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mixed ration containing cleaved wheat straw adlibitum, 2.5 kg of grain and 2.5 kg of

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pulverized corn with adlibitum water get to. Organization and national rules for the

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utilization and care of the animals were taken as indicated by the Medical Research

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Ethics Committee, Mansoura University, Mansoura, Egypt, code No. R/12.

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2.2. Study Design

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In a randomized crossover study, each donkey was epidurally injected with saline

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solution, xylazine, and dexmedetomidine. The time between every treatment and the

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sequential one was one week. Before the experimental procedure, all donkeys were

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fasted for not less than six hours preceding the trial and there is neither food nor water

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was given amid the examination period. Through raising the tail here and there, the

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second inter-coccygeal space (C2– C3) was distinguished and then the overlying skin

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was handled in aseptic manner. A 5 cm length and 18 gauge thickness hypodermic

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needle was presented on a middle plane at an angle of 30° to 45° until it reached the

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epidural space. The correct needle site in the space was affirmed by evidence of negative

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pressure, absence of the resistance during injection, and hanging drop technique. One

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trained investigator performed all epidural treatments. Treatment trials were conducted

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by epidural injection of saline solution (0.9 %, 12 ml; Sodium Chloride 0.9 % - Normal

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Saline, Egypt Otsuka Pharmaceutical Co., S.A.E., 10th of Ramadan City, Egypt),

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xylazine hydrochloride (0.20 mg kg-1; Xyla-Ject Injectable Solution 20 mg / ml,

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ADWIA Pharmaceuticals Co., 1st Industrial area, Al-Obour City, Cairo, Egypt ), and

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dexmedetomidine hydrochloride (0.005 mg kg-1; Precedex Injection, 100 Mcg / ml,

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Lakeforest, USA) [5,21,23]. After calculating the exact dose of xylazine and

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dexmedetomidine for each donkey, the used medicaments were adjusted to be a 12 ml

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final volume by adding water for injection (a sterile, non-pyrogenic, solute-free

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preparation of distilled water for injection, FIPCO, Borg Al-Arab, Forth Industrial Zone,

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Block No.3, Alexandria, Egypt) as necessary and were injected slowly into the epidural

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space over a period of approximately 2 minutes. Perineal analgesia was evaluated

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through absence of response to pin-prick techniques of the skin and deep muscles of the

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tail base, perineum, anus, and upper hind limb with a needle size of 22 gauge and 2.5 cm

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long. Adequate pressure on the perineal region, the root of the tail, the anus, and the

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upper hind limb has been verified. The active pain response was noticed as strong

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movement of the animal head, neck, trunk, limbs, and tail. The time of the onset and end

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of perineal analgesia, sedation and ataxia was recorded. The degree of perineal

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analgesia, sedation, and ataxia were rated according to modified simple descriptive scale

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described by Hamed et al. [21]. Tail flaccidity was evaluated and confirmed when the

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tail fleshy part was easily moved from one side to another. Heart rate (beats/min),

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respiratory rate (respiratory cycle/min), and body temperature (oC) were examined. The

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evaluation process of the analgesia was carried out by a single investigator who was

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blinded to the treatments the animals received.

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2.3.Echocardiographic examination

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After competent restraint of donkeys, the left side of the chest was prepared

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thoroughly at the zone between 3rd and 5th intercostal space just caudal to the triceps

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muscle, and 3-5 cm underneath the olecranon technique to 5 – 10 cm above it. The

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examination area was thoroughly cleaned, and then a coupling gel was applied to

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enhance contact with the probe. All echocardiographic examinations were done in view

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of standard strategies [24 – 26]. Echocardiographic examination was performed using a

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2 – 3.9 MHz sector transducer (CHISON Digital Color Doppler Ultrasound, iVis 60

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EXPERT VET, China). The sector transducer was positioned at the fifth intercostal

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space at the level of olecranon or slightly dorsal to it, rotated, and directed slightly

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cranial to get the ideal picture. During echocardiography, two dimensional guided M-

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mode images were obtained using the left parasternal long axis five-chamber apical

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view. Once the ideal picture had been reached, both the echocardiographic dimensions

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list and the cardiac function indices were assessed using the Cube method and Teichholz

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method, respectively. Three cardiac cycles were measured and stored digitally on the

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ultrasound machine. Measurements were performed in the stored images in three non-

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consecutive cycles and an average value for the three cycles was obtained.

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2.4. Echocardiographic dimensions and cardiac function indices

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Two‐dimensional guided M‐mode echocardiography was used to assess the

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echocardiographic dimensions as well as the cardiac function indices as previously

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described in donkeys [24,25]. The echocardiographic dimensions were evaluated

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including interventricular septum thickness at end diastole (IVSTd), interventricular

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septum thickness at end systole (IVSTs), LVIDd, LVIDs, left ventricle posterior wall

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thickness at end diastole (LVPWd), and left ventricle posterior wall thickness at end

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systole (LVPWs) Using the cube method. Meanwhile, left ventricular EDV, left

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ventricular ESV, SV, FS and EF were estimated using Teichholz method.

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Echocardiographic parameters and cardiac indices were recorded for each donkey before

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administration of saline solution, xylazine and dexmedetomidine and at 15, 30, 60, 90,

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120 and 180 minutes post administration. In all echocardiographic examinations, the

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echocardiographic dimensions and cardiac function indices were assessed by the one

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trained examiner.

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2.5.Statistical Analysis

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Data analysis was achieved using a statistical software program (GraphPad prism

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for windows Version 8, GraphPad Software, San Diego, CA). Shapiro normality test

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was used to evaluate the normal distribution of the data. The scores of analgesia,

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sedation, and ataxia were presented as median (range). Meanwhile, parametric data were

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expressed as mean ± standard deviation. A Two-Way Repeated Measure ANOVA was

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conducted to study evidence of time × treatment interaction as well as the main effect of

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time and treatment. In the case of a statistical significant difference between groups,

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One-Way ANOVA with Tukey Post hoc Multiple Comparisons test was utilized to

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distinguish which group was statistically different from the rest. Differences between

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means at p < 0.05 were considered to be significant.

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3. Results

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In all studied donkeys, at the needle puncture site, there are no signs of infection or

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neurological injury following epidural injection of saline solution, xylazine, or

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dexmedetomidine were distinguished. Epidural administration of saline solution had no

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significant effect on analgesia score 0 (0 – 0), sedation score 0 (0 – 0), or ataxia score 0

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(0 – 0) as well as the echocardiographic dimensions and cardiac function indices.

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Epidural injection of xylazine or dexmedetomidine, in the studied donkeys, induced

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complete bilateral perineal analgesia with a recorded score 3 (3 – 3) for each, manifested

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by loss of sensation at perineum, tail flaccidity, loss of anal sphincter reflex, and vulva

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relaxation in females. The maximal analgesic effect of xylazine started at 15 ± 1.1

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minutes and continued until 140 ± 5.3 minutes post-administration. However, the

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maximal analgesic effect of dexmedetomidine started at 6 ± 2.1 minutes and lasted up to

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170 ± 10 minutes post-administration.

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Epidural use of xylazine or dexmedetomidine in donkeys induced moderate sedation

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score 2 (2 – 2) manifested by lethargy; intermittent response to external stimuli; and

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slight drop of the head, lips, and eyelids. In donkeys injected epidurally with xylazine,

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the sedation effect was started at 15 ± 6.1 minutes and continued till 102 ± 5.2 minutes

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post-administration. However, in donkeys injected epidurally with dexmedetomidine,

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the sedation effect was started at 15 ± 2.5 minutes and lasted up to 120 ± 5.0 minutes

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post-administration.

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Epidural injection of xylazine or dexmedetomidine in donkeys induced mild ataxia.

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In xylazine-treated donkeys, it started at 10 ± 1.1 minutes and continued till 132 ± 5.2

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minutes post-administration. Meanwhile, in dexmedetomidine-treated donkeys, it started

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at 10.5 ± 1.5 minutes and continued until 175 ± 5.1 minutes post-administration.

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The recorded heart rate, respiratory rate, and rectal temperature in donkeys

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epidurally injected with saline solution, xylazine, or dexmedetomidine remained within

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the normal range values all the time, 28–44 beat/minute, 10–24 respiratory cycle /

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minute, and 37–38.2 oC, respectively.

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The impact and length of epidural injection of xylazine and dexmedetomidine on

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echocardiographic parameters were variable. In the present study, there was a significant

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(p < 0.05) decrease of IVSTs at 60 minutes (Table 1), SV at 30 to 120 minutes (Table 5),

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FS at 120 minutes (Table 6), and EF at 90 to 120 minutes (Table 7) following epidural

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injection of xylazine or dexmedetomidine when compared with saline solution.

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Moreover, left ventricular EDV was significantly (p < 0.05) increased at 60 minutes

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after epidural administration of dexmedetomidine compared with both xylazine and

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saline solution (Table 3). However, there was a significant (p < 0.05) increase of LVIDd

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at 90 to 120 minutes (Table 2) and left ventricular ESV at 60 to 180 minutes following

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epidural administration of xylazine or dexmedetomidine when compared with saline

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solution (Table 5). IVSTd, LVIDs, LVPWd, and LVPWs were not significantly altered

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in all three treatments.

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4. Discussion

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The use of epidural space for administration of analgesic drugs has become fairly

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common in horses to assist with a variety of issues, including surgery of the rectum,

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vagina, perineum, bladder, and urethra. In such cases, to avoid general anesthesia and to

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reduce surgical stress, the epidural analgesia was required to provide a longer duration

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of analgesia [6, 27]. In equine medicine, it is routinely to use alpha-2 adrenergic agonists

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for their effects analgesic and sedative effects. These medicaments have historically

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been reported to possess arrhythmogenic and cardio-toxic side effects which are major

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determinants for its selection as analgesic agent. The results of this study highlight

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changes in echocardiographic dimensions and cardiac function indices following

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epidural injection of xylazine or dexmedetomidine using echocardiography.

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Xylazine (0.20 mg kg-1) and dexmedetomidine (0.005 mg kg-1) induced transient

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alteration of echocardiographic dimensions as well as cardiac function indices in

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donkeys, suggesting liability of donkeys to show mild cardiac adverse effects after

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epidural administration of these medications. Following epidural use of these

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medications, the cardiovascular adverse effects may be observed due to their spread to

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the upper four thoracic segments and to the low right-sided cardiac filling pressure [7].

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Alpha-2 adrenoceptor agonists provide a local drug depot at the level of the spinal

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cord which is released slowly over a longer period of time [28]. Xylazine is a lipophilic

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medication with low molecular weight, encouraging its meningeal entrance when

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administered epidurally and penetrates the blood brain barrier with a subsequent

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fundamental systemic impact leading to a decrease in neurotransmission of

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norepinephrine and dopamine in the central nervous system [5, 9]. In sheep, epidural

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dexmedetomidine injection produces rapid antinociception and hypotension due to its

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rapid onset in cerebrospinal fluid with activation of spinal alpha-2 adrenoceptor in the

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superficial dorsal horn and surrounding preganglionic sympathetic neurons [10].

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Dexmedetomidine exerts its effect via postsynaptic activation of alpha-2 adrenoceptors

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in the central nervous system, inhibiting sympathetic activity with eventual decreased

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blood pressure and heart rate [29]. In dogs, dexmedetomidine seems to have systemic

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and coronary hemodynamic effects, including decreased heart rate, cardiac output, and

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coronary blood flow, and increased mean arterial pressure, left ventricular end-diastolic

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pressure and systemic and coronary vascular resistance [30].

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In the existing study, the LVIDd was increased, without changes in the left ventricle

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wall thickness, after epidural injection of xylazine or dexmedetomidine, as described

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previously in horses [13], dogs [14] and cats [31], suggesting increased ventricular

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afterload with subsequent decreased SV and increased left ventricular ESV. Intra-

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muscular injection of medetomidine in cats induces a significant decrease in heart rate,

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cardiac output, and stroke volume [32]. Moreover, in human, intravenous infusion of

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high doses of dexmedetomidine increases systemic vascular resistance leading to

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systemic hypertension, increased both afterload and left ventricular ESV, and reduced

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stroke volume with concomitant decreased heart rate, which normalizes within 15

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minutes [2,33]. The increased left ventricular ESV, however, leads to a secondary

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increase in left ventricular EDV because more blood is left inside the ventricle following

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ejection and this extra blood is added to the venous return, thereby increasing ventricular

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filling, which stretches the muscle fibers thereby increasing their preload. The secondary

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increased preload enables the ventricle to contract with greater force, which partially

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offsets the reduction in SV caused by the initial increase in afterload [34].

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Epidural administration of dexmedetomidine resulted in increased left ventricular

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EDV due to increased ventricular filling time and filling pressure, which occurs when

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the compliance of the ventricle falls [35, 36]. Therefore, the cardiac muscle fibers

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expand and increase in size in an attempt to improve contractility, thereby decreasing the

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ability to relax during diastole. Wall thickness actually may be decreased post-sedation

297

when the left ventricular dimension increased, as an indicator of a left ventricular

298

volume function [37].

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After epidural administration of xylazine or dexmedetomidine, the IVSTs was

300

significantly decreased, while the left ventricular ESV was significantly increased,

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proposing a condition of systolic failure, which appeared to be due to the impaired

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cardiac contractility and/or cardiac pumping capacity. In horses, the increased left

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ventricular ESV was explained by a reduction in the systolic left ventricular

304

performance [38]. The same results were previously reported in horses sedated with

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detomidine or romifidine [13] and xylazine [39]. Meanwhile, in healthy cats sedated

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with dexmedetomidine and butorphanol, there were no significant changes in the

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echocardiographic dimensions (IVSTd, IVSTs, LVPWd and LVPWs) [31]. Increased

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left ventricular ESV is associated with increased diastolic load as well as increased left

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ventricular cavity size, which indicates worse prognosis and affects the racing

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performance of the horse [40]. Fortunately, the recorded effect in our study is transient,

311

suggesting that there is no evidence of myocardial infarction. In human, ventricular

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dilation may be an early marker of disease in patients with dilated cardiomyopathy [41]

313

or those undergoing follow-up treatment with cardiotoxic therapy [42]. Increased left

314

ventricular ESV and left ventricular EDV with a subsequent increase in wall stress,

315

which in turn may act as a stimulus for cardiac hypertrophy has been found to occur

316

with cardiac infarction [43].

317

The SV, FS, and EF were decreased following epidural injection of xylazine or

318

dexmedetomidine, indicating a reduced left ventricular performance which constitutes

319

an important pathophysiological mechanism for occurrence of heart failure. The

320

recorded decrease of SV, FS, and EF may be attributed to the myocardial depressant

321

effect of alpha-2 agonists and therefore leads to ineffective cardiac contraction [13, 32].

322

Furthermore, EF was decreased in case of systolic dysfunction, thus raising the blood

323

volume in the left ventricle with subsequent reduced contraction force of the

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myocardium due to ventricular overload [37]. The same results were previously

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recorded following intravenous injection of dexmedetomidine in healthy horses [13] and

326

healthy dogs [14]. In contrast, Canola et al. [11] and Linardi et al. [12] didn't record any

327

statistical differences in the values of cardiac function indices (FE and FS) in horses,

328

following intravenous administration of romifidine and xylazine, respectively. The

329

authors attributed their findings to the unnoticeable parasympathetic stimulus in the

330

cardiac inotropism due to its limited ventricular innervations

331

[15, 44] even with

predominant vagal activity under alpha-2 agonists action [45].

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The shortcoming of this study should be acknowledged. First, the shortage of

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pharmacokinetic investigations of dexmedetomidine and xylazine in donkeys may

334

disallow full clarification of the outcomes. Second, the lack of data collected for blood

335

pressure and its possible correlation with the observed echocardiographic changes.

336

Third, the present results were based on experimental study in healthy donkeys, which

337

may not reflect the real condition of diseased ones. In this manner, further surveys are

338

13

required to get genuine decisions about the cardiac impact of these medications in

339

clinical cases with full thought of the weaknesses of past investigations.

340 341

5. Conclusion

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Although the results of the present investigation demonstrated that epidural injection of

343

xylazine (0.20 mg kg-1) or dexmedetomidine (0.005 mg kg-1) in donkeys have the same

344

effect that cause transient and short-term changes of echocardiographic dimensions

345

(IVSTs and LVIDd), and compromise the cardiac function indices (left ventricular ESV,

346

SV, FS, and EF), dexmedetomidine had a significant effect on the left ventricular EDV

347

when compared with xylazine. The potential for cardiovascular compromise should be

348

considered when such medicaments are to be administered into the epidural space.

349

Therefore, care should be taken during epidural use of xylazine or dexmedetomidine in

350

donkeys with a pre-anesthetic cardiovascular compromise as both medications affect the

351

cardiac function indices that are clinically relevant and should always be considered.

352 353

Declaration: All authors gave their informed consent prior to their inclusion in the

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study.

355 356

Conflict of Interest statement: The authors declare that they have no conflict of

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interest.

358 359

Ethical approval: All applicable international, national, and/or institutional guidelines

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for the care and use of animals were followed.

361 362 363 364

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6. References

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[1] Robinson EP, Natalini CC. Epidural anesthesia and analgesia in horses. Vet Clin

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North Am Equine Pract 2002;18:61-82. [2] Giovannitti Jr JA, Thoms SM, Crawford JJ. Alpha-2 adrenergic receptor agonists: a review of current clinical applications. Anesth Prog 2015;62:31-9. [3] Lizarraga I, Janovyak E. Comparison of the mechanical hypoalgesic effects of five α2-adrenoceptor agonists in donkeys. Vet Rec 2013;173:294. [4] De Rossi R, Segura IAG. Analgesic, haemodynamic and respiratory effects of caudal epidural xylazine in equines. Hora Vet 2001;120:49-53.

367 368 369 370 371 372 373

[5] Dória RG, Valadão CA, Duque JC, Farias A, Almeida RM, Netto AC. Comparative

374

study of epidural xylazine or clonidine in horses. Vet Anaesth Analg 2008;35:166-

375

72.

376

[6] Sarafzadeh RF, Rezazadeh F, Behfar M. Comparison of caudal epidural

377

administration of lidocaine and xylazine to xylazine / ketamine combination in

378

donkey(equus asinus). Iran J Vet Surg 2007;5:1-7.

379

[7] Steagall PVM, Simon BT, Teixeira Neto FJ, Luna SPL. An Update on Drugs Used

380

for Lumbosacral Epidural Anesthesia and Analgesia in Dogs. Front Vet Sci

381

2017;4:68.

382

[8] Singh P, Pratap K, Amarpal P, Kinjavdekar P, Aithal HP, Singh GR. Haemodynamic

383

and electrocardiographic effects of xylazine, ketamine, lidocaine and their

384

combinations after lumbar epidural administration in healthy buffalo calves. J Appl

385

Anim Res 2005; 28:101-6.

386

[9] St Jean G, Skarda RT, Muir WW, Hoffsis GF. Caudal epidural analgesia induced by xylazine administration in cows. Am J Vet Res 1990;51:1232-6.

15

387 388

[10] Eisenach JC, Shafer SL, Bucklin BA, Jackson C, Kallio A. Pharmacokinetics and

389

pharmacodynamics of intraspinal dexmedetomidine in sheep. Anesthesiology

390

1994;80:1349-59.

391

[11] Canola J, Cardenas J, Canola P. Efeito da romifidina sobre as dimensões

392

ecocardiográficas e sobre índices da função cardíaca em eqüinos / Effects of

393

romifidine on echocardiographic measurements of cardiac dimensions as indices of

394

cardiac function in horses). Ars Veterinaria, Jaboticabal, SP 2002;18:231-7.

395

[12] Linardi R, Canola J, Valadão C. Cardiovascular assessment in horses sedated with xylazine or amitraz. Arq Bras Med Vet Zoo 2008;60:329-34.

396 397

[13] Buhl R, Ersbøll AK, Larsen NH, Eriksen L, Koch J. The effects of detomidine,

398

romifidine or acepromazine on echocardiographic measurements and cardiac

399

function in normal horses. Vet Anaesth Analg 2007;34:1-8.

400

[14] Wang HC, Hung CT, Lee WM, Chang KM, Chen KS. Effects of intravenous

401

dexmedetomidine on cardiac characteristics measured using radiography and

402

echocardiography in six healthy dogs. Vet Radiol Ultrasound 2016;57:8-15.

403

[15] Patteson M. Equine cardiology. oxford: Black well Science. 1996.

404

[16] Pipers F, Hamlin R. Echocardiography in the horse. J Am Vet Med Assoc

405

1977;70:815-9.

406

[17] Grubb TL, Riebold TW, Crisman RO, Lamb LD. Comparison of lidocaine,

407

xylazine, and lidocaine-xylazine for caudal epidural analgesia in cattle. Vet Anaesth

408

Analg 2002;29:64-8.

409

[18] Meyer H, Kästner SB, Beyerbach M, Rehage J. Cardiopulmonary effects of dorsal

410

recumbency and high-volume caudal epidural anaesthesia with lidocaine or xylazine

411

in calves. Vet J 2010;186:316-22.

412

[19] Danghee L, Chunsik B. Effect of xylazine in cattle under rope restrained conditions. J of Vet Clinics 2001;18:189-94.

413 414

16

[20] Pathak R, Pratap K, Amarpal, Kinjavdekar P, Aithal, HP, Pankaj. Comparison of

415

bupivacaine, xylazine and buprenorphine with ketamine combination for spinal

416

analgesia in buffalo calves. Vet World 2012;5: 754-61.

417

[21] Hamed MA, Abouelnasr KS, Ibrahim HM, El-khodery SA. Comparative sedative

418

and analgesic effects of epidural dexmedetomidine and xylazine in donkeys (Equus

419

asinus). J Equine Vet Sci 2017; 59:104-9.

420

[22] Constable PD, Hinchcliff KW, Done SH, Grünberg W. Diseases of the

421

Cardiovascular System. In: Veterinary Medicine: A textbook of the diseases of

422

cattle, horses, sheep, pigs and goats, 11th ed, Missouri, United States: Elsevier Ltd;

423

2017, p. 657-715.

424

[23] Lizarraga I, Castillo-Alcala F, Robinson LS. Comparison of sedation and

425

mechanical antinociception induced by intravenous administration of acepromazine

426

and four dose rates of dexmedetomidine in donkeys. Vet Anaesth Analg

427

2017;44:509-17.

428

[24] Hassan EA, Torad FA. Two-dimensional and M-mode echocardiographic

429

measurements in the healthy donkey (Equus asinus). J Equine Vet Sci 2015;35:283-

430

9.

431

[25] Youssef MA, Ibrahim HM, Farag E-SM, El-Khodery SA. Effects of tilmicosin

432

phosphate administration on echocardiographic parameters in healthy donkeys

433

(Equus asinus): An experimental study. J Equine Vet Sci 2016;38:24-29.

434

[26] Schiller NB, Shah PM, Crawford M, DeMaria A, Devereux R, Feigenbaum H, et al.

435

Recommendations for quantitation of the left ventricle by two-dimensional

436

echocardiography. J Am Soc Echocardiogr 1989;2:358-67.

437

[27] LeBlanc P, Caron J, Patterson J, Brown M, Matta M. Epidural injection of xylazine for perineal analgesia in horses. J Am Vet Med Assoc 1988;193:1405-8.

17

438 439

[28] Singh P, Pratap K, Kinjavdekar P, Aithal H, Singh G, Pathak R. Xylazine, ketamine

440

and their combination for lumbar epidural analgesia in water buffalo calves

441

(Bubalus bubalis). Transbound Emerg Dis 2006;53:423-31.

442

[29] Gertler R, Brown HC, Mitchell DH, Silvius EN. Dexmedetomidine: a novel sedative-analgesic agent. Proc (Bayl Univ Med Cent) 2001;14:13-21.

443 444

[30] Roekaerts P, Lawrence C, Prinzen F, Lange Sd. Alleviation of the peripheral

445

hemodynamic effects of dexmedetomidine by the calcium channel blocker

446

isradipine. Acta Anaesth Scand 1997;41:364-70.

447

[31] Johard E, Tidholm A, Ljungvall I, Häggström J, Höglund K. Effects of sedation

448

with dexmedetomidine and buprenorphine on echocardiographic variables, blood

449

pressure and heart rate in healthy cats. J Feline Med Surg 2018; 20:554-62.

450

[32] Lamont LA, Bulmer BJ, Grimm KA, Tranquilli WJ, Sisson DD. Cardiopulmonary

451

evaluation of the use of medetomidine hydrochloride in cats. Am J Vet Res

452

2001;62:1745-62.

453

[33] Lee SH, Na S, Kim N, Ban MG, Shin SE, Oh YJ. The effects of dexmedetomidine

454

on myocardial function assessed by tissue doppler echocardiography during general

455

anesthesia in patients with diastolic dysfunction: a consort-prospective, randomized,

456

controlled trial. Medicine (Baltimore) 2016;95:e2805.

457

[34] Kumar A, Anel R, Bunnell E, Zanotti S, Habet K, Haery C, Marshall S, Cheang M,

458

Neumann A, Ali A, Kavinsky C, Parrillo JE. Preload-independent mechanisms

459

contribute to increased stroke volume following large volume saline infusion in

460

normal volunteers: a prospective interventional study. Crit Care 2004;8:R128-36.

461

[35] Boron WF, Boulpaep EL. Medical Physiology: a cellular and molecular approach.

462

2003 W.B. Saunders, USA.

463

[36] Noble MI. Whatever Happened to Measuring Ventricular Contractility in Heart Failure?. Card Fail Rev 2017;3:79-82.

464 465

18

[37] Kemp CD, Conte JV. The pathophysiology of heart failure. Cardiovasc Pathol 2012;21:365-71.

466 467

[38] Patteson M, GIBBS C, Wotton P, Cripps P. Effects of sedation with detomidine

468

hydrochloride on echocardiographic measurements of cardiac dimensions and

469

indices of cardiac function in horses. Equine Vet J 1995;27:33-7.

470

[39] Mircean M, Giurgiu G, Oana L, Mircean V, Scurtu I, Mureşan C. Ultrasound

471

evaluation of cardiac function following administration of sedatives in horses.

472

Bulletin UASVM, Veterinary Medicine 2010;67:171.

473

[40] Buhl R, Ersbøll AK, Eriksen L, Koch J. Changes over time in echocardiographic

474

measurements in young Standardbred racehorses undergoing training and racing and

475

association with racing performance. J Am Vet Med Assoc 2005;226:1881–7.

476

[41] Mahon NG, Murphy RT, MacRae CA, Caforio AL, Elliott PM, McKenna WJ.

477

Echocardiographic evaluation in asymptomatic relatives of patients with dilated

478

cardiomyopathy reveals preclinical disease. Ann Intern Med 2005;143:108-15.

479

[42] Jiji RS, Kramer CM, Salerno M. Non-invasive imaging and monitoring cardiotoxicity of cancer therapeutic drugs. J Nucl Cardiol 2012;19:377-88. [43] Yeap X-Y, Dehn S, Adelman J, Lipsitz J, Thorp EB. Quantitation of acute necrosis after experimental myocardial infarction. Methods Mol Biol2013:115-33. [44] Guyton AC, Hall J. Textbook of medical physiology. 11th ed. Philadelphia, PA, USA: Elsevier Inc; 2006, p. 103-57.

480 481 482 483 484 485

[45] Braunwald E. Heart failure. JACC Heart Fail 2013;1:1-20.

486 487 488

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Table 1. Inter-ventricular septal thickness at end-systole (IVSTs) (mm; mean ± standard deviation) after epidural injection of saline solution (12 ml/animal), xylazine (0.20 mg kg-1) and dexmedetomidine (0.005 mg kg-1) in donkeys (n = 10) Inter-ventricular septal thickness at end-systole (IVSTs) (mm)

T Zero

saline solution (n = 10) 4.08 ± 0.39

Xylazine (n = 10) 4.38 ± 0.25

Dexmedetomidine (n = 10) 3.99 ± 0.32

T 15 minutes

4.02 ± 0.42

4.19 ± 0.45

3.86 ± 0.34

T 30 minutes

4.09 ± 0.38

3.96 ± 0.50

3.70 ± 0.39

T 60 minutes

4.17 ± 0.36 a

3.77 ± 0.40 b

3.59 ± 0.19 b

T 90 minutes

4.19 ± 0.35

4.18 ± 0.55

3.62 ± 0.49

T 120 minutes

4.08 ± 0.36

4.10 ± 0.43

3.62 ± 0.47

T 180 minutes

4.11 ± 0.31

4.26 ± 0.41

3.82 ± 0.53

Time * Treatment interaction: P = 0.004. Time: P = 0.238. Treatment: P = 0.001. a,b

: Variables with different superscript letters in the same row are significantly different at P < 0.05.

Table 2. Left ventricular internal diameter at end-diastole (LVIDd) (mm; mean ± standard deviation) after epidural injection of Saline solution (12 ml/animal), xylazine (0.20 mg kg-1) and dexmedetomidine (0.005 mg kg-1) in donkeys (n = 10) Left ventricular internal diameter at end-diastole (LVIDd) (mm)

T Zero

Saline solution (n = 10) 4.82 ± 0.67

Xylazine (n = 10) 4.84 ± 0.63

Dexamedetomidine (n = 10) 4.81 ± 0.67

T 15 minutes

4.80 ± 0.67

5.07 ± 0.64

4.71 ± 0.61

T 30 minutes

4.85 ± 0.67

5.15 ± 0.55

4.66 ± 0.66

T 60 minutes

4.84 ± 0.65

5.01 ± 0.68

4.75 ± 0.62

T 90 minutes

4.82 ± 0.69 a

5.88 ± 0.67 b

5.89 ± 0.68 b

T 120 minutes

4.84 ± 0.65 a

5.84 ± 0.62 b

5.87 ± 0.66 b

T 180 minutes

4.88 ± 0.63

5.21 ± 0.41

5.21 ± 0.77

Time * Treatment interaction: P = 0.006. Time: P = 0.551. Treatment: P = 0.012. a,b

: Variables with different superscript letters in the same row are significantly different at P < 0.05.

Table 3. Left ventricular end diastolic volume (EDV) (ml; mean ± standard deviation) after epidural injection of Saline solution (12 ml/animal), xylazine (0.20 mg kg-1) and dexmedetomidine (0.005 mg kg-1) in donkeys (n = 10) Left ventricular end diastolic volume (EDV) (ml)

T Zero

Saline solution (n = 10) 216.3 ± 8.2

Xylazine (n = 10) 218.5 ± 8.7

Dexamedetomidine (n = 10) 215.7 ± 9.0

T 15 minutes

216.4 ± 8.9

215.3 ± 8.9

215.8 ± 7.3

T 30 minutes

216.6 ± 9.1

216.2 ± 8.6

220.3 ± 6.5

T 60 minutes

217.2 ± 9.4 a

217.2 ± 9.3 a

230.3 ± 6.7 b

T 90 minutes

218.7 ± 6.9

218.1 ± 8.3

218.8 ± 7.7

T 120 minutes

218.9 ± 6.8

215.7 ± 6.9

214.5 ± 5.9

T 180 minutes

219.5 ± 8.1

217.2 ± 7.6

216.7 ± 5.8

Time * Treatment interaction: P = 0.001. Time: P = 0.361. Treatment: P = 0.001. a,b

: Variables with different superscript letters in the same row are significantly different at P < 0.05.

Table 4. Left ventricular end systolic volume (ESV) (ml; mean ± standard deviation) after epidural injection of Saline solution (12 ml/animal), xylazine (0.20 mg kg-1) and dexmedetomidine (0.005 mg kg-1) in donkeys (n = 10) Left ventricular end systolic volume (ESV) (ml)

T Zero

Saline solution (n = 10) 67.2 ± 7.4

Xylazine (n = 10) 67.7 ± 6.5

Dexmedetomidine (n = 10) 66.3 ± 8.3

T 15 minutes

66.4 ± 7.5

64.7 ± 4.3

67.8 ± 4.8

T 30 minutes

67.3 ± 7.9

75.7 ± 5.4

69.3 ± 8.6

T 60 minutes

67.6 ± 6.9 a

83.8 ± 5.2 b

82.3 ± 3.5 b

T 90 minutes

66.9 ± 7.1 a

92.8 ± 5.4 b

90.8 ± 4.6 b

T 120 minutes

67.8 ± 7.7 a

91.2 ± 4.1 b

89.1 ± 3.7 b

T 180 minutes

67.7 ± 7.4 a

83.3 ± 6.4 b

80.5 ± 6.6 b

Time * Treatment interaction: P = 0.001. Time: P = 0.047. Treatment: P = 0.001. a,b,c

: Variables with different superscript letters in the same row are significantly different at P < 0.05.

Table 5. Stroke volume (SV) (ml; mean ± standard deviation) after epidural injection of Saline solution (12 ml/animal), xylazine (0.20 mg kg-1) and dexmedetomidine (0.005 mg kg-1) in donkeys (n = 10) Stroke volume (SV) (ml)

T Zero

Saline solution (n = 10) 169.1 ± 5.5

Xylazine (n = 10) 170.1 ± 4.5

Dexmedetomidine (n = 10) 168.1 ± 5.9

T 15 minutes

169.2 ± 5.7

164.2 ± 3.5

166.3 ± 5.6

T 30 minutes

169.7 ± 5.3 a

162.8 ± 5.5 b

162.3 ± 5.3 b

T 60 minutes

169.3 ± 5.4 a

160.2 ± 3.2 b

161.7 ± 4.8 b

T 90 minutes

168.8 ± 5.6 a

158.3 ± 4.1 b

161.7 ± 5.1 b

T 120 minutes

168.3 ± 5.3 a

160.8 ± 3.9 b

159.3 ± 5.0 b

T 180 minutes

169.1 ± 5.4

169.1 ± 4.2

164.1 ± 4.9

Time * Treatment interaction: P = 0.001. Time: P = 0.102. Treatment: P = 0.001. a,b

: Variables with different superscript letters in the same row are significantly different at P < 0.05.

Table 6. Fractional shortening (FS) (%; mean ± standard deviation) after epidural injection of Saline solution (12 ml/animal), xylazine (0.20 mg kg-1) and dexmedetomidine (0.005 mg kg-1) in donkeys (n = 10) Fractional shortening (FS) (%) Saline solution (n = 10)

Xylazine (n = 10)

Dexmedetomidine (n = 10)

T Zero

48.3 ± 3.3

48.8 ± 4.9

47.7 ± 6.4

T 15 minutes

48.8 ± 3.8

46.5 ± 4.3

45.3 ± 6.4

T 30 minutes

49.4 ± 7.1

45.2 ± 4.2

45.3 ± 7.2

T 60 minutes

48.8 ± 5.8

46.3 ± 5.6

44.2 ± 6.7

T 90 minutes

48.6 ± 5.6

42.2 ± 6.1

42.8 ± 7.7

T 120 minutes

48.8 ± 5.5 a

41.2 ± 5.2 b

40.5 ± 7.7 b

T 180 minutes

49.2 ± 6.2

47.5 ± 4.3

45.2 ± 7.7

Time * Treatment interaction: P = 0.001. Time: P = 0.443. Treatment: P = 0.001. a,b

: Variables with different superscript in the same row are significantly different at P < 0.05.

Table 7. Ejection fraction (EF) (%; mean ± standard deviation) after epidural injection of Saline solution (12 ml/animal), xylazine (0.20 mg kg-1) and dexmedetomidine (0.005 mg kg-1) in donkeys (n = 10) Ejection fraction (EF) (%)

T Zero

Saline solution (n = 10) 90.3 ± 3.4

Xylazine (n = 10) 89.7 ± 3.4

Dexmedetomidine (n = 10) 89.1 ± 3.8

T 15 minutes

90.8 ± 3.2

89.8 ± 3.3

88.7 ± 4.2

T 30 minutes

91.1 ± 3.4

87.7 ± 3.4

88.5 ± 4.1

T 60 minutes

90.3 ± 3.3

86.7 ± 3.5

87.3 ± 2.6

T 90 minutes

91.5 ± 3.5 a

82.5 ± 2.8 b

84.5 ± 2.3 b

T 120 minutes

91.8 ± 3.2 a

84.5 ± 3.1 b

84.5 ± 3.5 b

T 180 minutes

90.3 ± 2.1

89.8 ± 3.6

89.7 ± 3.3

Time * Treatment interaction: P = 0.001. Time: P = 0.538. Treatment: P = 0.001. a,b

: Variables with different superscript in the same row are significantly different at P < 0.05.

Highlights •

• • •

Ten healthy donkeys were epidurally injected with xylazine or dexmedetomidine. Echocardiography was performed for each donkey at different time points following administration. Fractional shortening, ejection fraction, and stroke volume were reduced. The changes in the cardiac function indices were nearly identical for xylazine and dexmedetomidine.

Author statement

We affirm that the submission represents original work that has not been published previously and is not currently being considered by another journal. All other Authors have read the manuscript and have agreed to submit it in its current form for consideration for publication. We confirm that the legal and ethical requirements have been met with regards to the humane treatment of animals described in the study This manuscript is the first report that compares the effect of epidural administration of dexmedetomidine and xylazine on echocardiographic dimensions and cardiac indices in clinically healthy donkeys. The effect of both drugs is variable. Thank you for your cooperation and waiting for your response Kind regards Corresponding author Hussam M. M. Ibrahim

Author’s contributions: To qualify as an author one should 1) have made substantial contributions to conception and design, or acquisition of data, or analysis and interpretation of data; 2) have been involved in drafting the manuscript or revising it critically for important intellectual content; 3) have given final approval of the version to be published; and 4) agree to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. We suggest the following kind of format (please use initials to refer to each author's contribution): AB carried out the molecular genetic studies, participated in the sequence alignment and drafted the manuscript. JY carried out the immunoassays. MT participated in the sequence alignment. ES participated in the design of the study and performed the statistical analysis. FG conceived of the study, and participated in its design and coordination and helped to draft the manuscript. All authors read and approved the final manuscript. SE: Conceived and designed the experiments, analyzed the data, final revision and submission. MH: Conceived and designed the experiments, and helped to draft the manuscript HI: Performed the experiments, revised the data KA: Performed the experiments RE: drafting the paper Name and signature:

Conflict of Interest statement: The authors declare that they have no conflict of interest.