The use of low doses of acepromazine as an aid for lameness diagnosis in horses: An accelerometric evaluation

Correlation between kinematic parameters, ataxia and ground-to-lip distance in detomidine sedated horses

BACKGROUND

An accurate evaluation of the degree of sedation is mandatory to adjust the dosage of sedative drugs.

OBJECTIVES

To determine the correlation between head height above the ground and ataxia degree in horses sedated with detomidine and the correlation existing between accelerometric variables and both parameters.

STUDY DESIGN

In vivo experiment.

METHODS

Twelve horses were given 0.01 mg/kg of detomidine hydrochloride iv. Measured accelerometric parameters, with one accelerometer positioned between both sacral tuberosities, included speed, stride frequency and length, regularity, dorsoventral, longitudinal, mediolateral and total accelerometric activities, relative force index and dorsoventral, longitudinal and mediolateral parts of the accelerometric activities. Head height above the ground (cm) and subjective ataxia degree were also measured. Baseline values (-15 min) and values measured 5 and 15 min after the injection and then every 15 min for a period of 2 h were obtained.

RESULTS

There was a negative and strong correlation between head height above the ground and ataxia degree (Pearson r = -0.78, p < 0.001), particularly during the first 45 min. A significant correlation was found between head height above the ground and almost all accelerometric parameters. This correlation was very strong with stride frequency, regularity and dorsoventral and total accelerometric activities in both cases, but for ataxia, also with total accelerometric activity.

MAIN LIMITATIONS

Experimental conditions may not represent real clinical situations.

CONCLUSIONS

Stride frequency and regularity are the most reliable parameters to determine degree of sedation and are related to the sedation produced. Ataxia should not be considered a separate property of sedation and does not need to be assessed separately to the depth of sedation.

Inertial Sensor Technologies-Their Role in Equine Gait Analysis, a Review

Objective gait analysis provides valuable information about the locomotion characteristics of sound and lame horses. Due to their high accuracy and sensitivity, inertial measurement units (IMUs) have gained popularity over objective measurement techniques such as force plates and optical motion capture (OMC) systems. IMUs are wearable sensors that measure acceleration forces and angular velocities, providing the possibility of a non-invasive and continuous monitoring of horse gait during walk, trot, or canter during field conditions. The present narrative review aimed to describe the inertial sensor technologies and summarize their role in equine gait analysis. The literature was searched using general terms related to inertial sensors and their applicability, gait analysis methods, and lameness evaluation. The efficacy and performance of IMU-based methods for the assessment of normal gait, detection of lameness, analysis of horse-rider interaction, as well as the influence of sedative drugs, are discussed and compared with force plate and OMC techniques. The collected evidence indicated that IMU-based sensor systems can monitor and quantify horse locomotion with high accuracy and precision, having comparable or superior performance to objective measurement techniques. IMUs are reliable tools for the evaluation of horse-rider interactions. The observed efficacy and performance of IMU systems in equine gait analysis warrant further research in this population, with special focus on the potential implementation of novel techniques described and validated in humans.

Morphine with or without Acepromazine in Horses: A Kinematic Evaluation

The objective was to demonstrate walking locomotor pattern alterations after co-administration of acepromazine and morphine in horses. Six mature horses receiving four different treatments were used. Treatments consisted of a single dose of saline solution, 0.2 mg/kg bwt of morphine hydrochloride, 0.02 mg/kg bwt of acepromazine maleate, and a combination of 0.2 mg/kg bwt of morphine hydrochloride with 0.02 mg/kg bwt of acepromazine maleate. A three-dimensional accelerometric device was used to collect data. Walking tests were performed 10 min prior to injection, and then at 5, 10, 15, and 20 min after the injection, and then every 10 min for 3 h. Eight variables were calculated including stride kinematic, coordination, and energetic parameters; moreover ground-to-lip distance (GLD), as a tranquilization parameter, was also measured. A significant interaction was observed in all the variables studied but regularity, mediolateral power, the propulsive part of the power, and the GLD. An evident counteraction of the effects caused by both, opioids and phenothiazines, in the gait pattern was observed. The co-administration of acepromazine and morphine could allow a safe opiate administration while minimizing the possible central nervous system (CNS) excitation and reducing potential locomotor adverse effects.

Accelerometric Evaluation of the Locomotor Pattern After Administration of Morphine in Conscious Healthy Horses

The objective of the present study was to compare, using accelerometry, the gait changes produced after administration of a dose of 0.2 mg/kg of morphine at the walk in healthy horses. Six mature horses were used, and all animals received two different treatments with, at least, two weeks interval in between. Treatments administered consisted of a single dose of 10 ml of saline solution or a total of 0.2 mg/kg of morphine diluted in 10 ml of saline solution. A three-dimensional accelerometric device was used to collect data continuously while horses were walking. The walking test was performed 10 min prior to injection, and then at 5, 10, 15 and 20 min after injection and then every 10 min for 3 h. Eight variables were calculated including stride kinematic, coordination and energetic parameters. Additionally, the force of acceleration and three components of the power were calculated. Significant interaction was only observed for stride length, propulsion power and the propulsive part of the total power with a reduction in values after morphine administration. Compared to baseline values, stride length values were significantly reduced for 80 min and again 110 min after injection of the opioid and at 5, 15, 20, 30 and 40 min in the case of propulsion power values. For the propulsion component of power, these differences were observed for 20 min when compared to baseline values. The administration of 0.2 mg/kg of morphine to conscious healthy horses produces limited effects on the gait pattern of horses and the effects on locomotor activity are minimal at this dose, not being an important concern for the administration of analgesia in a clinical setting.

Tranquilizer effect on the Lyapunov exponents of lame horses

Tranquilization of horses with acepromazine has been used to suppress erratic head movements and increase the accuracy of a lameness examination. Some equine clinicians believe that tranquilization with acepromazine will make lameness more evident by causing the horse to focus on adjusting its gait to avoid limb pain rather than its surroundings. The aim of this study was to investigate the effect of acepromazine on the Lyapunov exponents of lame horses. Ten lame horses were trotted in a straight line for a minimum of 25 strides. Kinematic data created by head movement were analyzed. Nonlinear analysis methods were applied to lame horse locomotion. The effect of acepromazine on the largest Lyapunov exponents of the lame horses were investigated. There was no statistically significant effect of acepromazine on the maximum value of Lyapunov exponents. The nonlinear dynamic methods can be used to analyze the gait in horses. Local stability of horse gait remains unchanged after the administration of acepromazine.

Effects of acepromazine and xylazine on subjective and objective assessments of forelimb lameness

BACKGROUND

To facilitate lameness evaluation, sedatives such as xylazine and acepromazine are regularly used in the clinical setting, despite concerns that they may confound lameness assessment.

OBJECTIVES

The objective of this study was to determine the effect of low doses of acepromazine and xylazine on subjective and objective lameness assessment.

STUDY DESIGN

Randomised, blinded, crossover study.

METHODS

Six horses with experimentally induced solar pain were evaluated over a 1-hour period after treatment with intravenous xylazine (0.1 or 0.2 mg/kg), intravenous acepromazine (0.02 or 0.04 mg/kg), intravenous saline (1 mL) or local analgesia (4 mL 2% mepivacaine administered subcutaneously). Lameness was assessed objectively with inertial sensors and subjectively on a scale from 0 to 5. Lameness assessments were compared with logistic regression analysis to account for the repeated measures and cross-over study design (P < .05).

RESULTS

Xylazine (0.1 and 0.2 mg/kg) or acepromazine (0.02 and 0.04 mg/kg) did not result in significant differences in objective lameness assessment (vector sum) or average subjective lameness grade. Local analgesia was associated with a decrease in subjective lameness grade (OR 0.32 [0.11-0.92], P = .03). Objective measures of lameness (vector sum) were significantly decreased 45 minutes (vector sum 41.8, P = .04) and 60 minutes (vector sum 47.3, P = .03) following local analgesia administration compared with baseline (vector sum 121.4).

MAIN LIMITATIONS

Extrapolation of the experimental model of moderate lameness used in this study to broad range of clinical lameness situations should be performed carefully.

CONCLUSIONS

These results support the use of low doses of xylazine or acepromazine to facilitate forelimb lameness evaluation up to 1 hour in duration.

Combined Effects of Water Depth and Velocity on the Accelerometric Parameters Measured in Horses Exercised on a Water Treadmill

Horse trainers often claim that exercise on a water treadmill (WT) leads to a greater muscle power and development compared to terrestrial locomotion, because of the greater viscosity of water compared to air. This research assesses locomotor changes measured with accelerometers fixed in the pectoral region and in the sacrum midline in six horses subjected to exercise sessions of 40 min duration on a WT without water (DT), and with water at the depth of fetlock (FET) and carpus (CAR) with velocities of 6 km/h and at the depth of stifle (STF) at 5 km/h. Another five horses performed the same exercise sessions but always with a velocity of 5 km/h. Total power increased from DT to FET and CAR, without significant differences between CAR and STF depths when the velocity was the same. However, a significant decrease was found when the velocity was reduced. The greater total power with water was distributed mainly to the dorsoventral axis, with significant increases in dorsoventral displacement and dorsoventral power. Both parameters were significantly affected by velocity and water depth. In conclusion, total and dorsoventral powers increased with velocity and water depth, leading to reduction in longitudinal and mediolateral power, during exercise on a WT.

Capacitive resistive electric transfer modifies gait pattern in horses exercised on a treadmill

Background

Capacitive resistive electric transfer (CRET), a radiofrequency at 448 kHz, resulted in increased superficial and deep temperature and hemoglobin saturation, faster elimination of metabolic and inflammatory products and enhanced sport performance in humans. This research aims to investigate whether the application of CRET affects the locomotor pattern in horses and to assess whether an accumulative effect appears when two CRET sessions are applied two consecutive days.

Methods

Nine horses were subjected to two CRET sessions applied in both right and left sides of neck, shoulder, back and croup. The horses were exercised on a treadmill, at walk and at trot, before CRET application and at 2, 6 and 12 h after. A second CRET session was applied next day, and the animals were evaluated again at the same times (i.e. at 26, 30 and 36 h after the first session). Between 5 and 7 days later, the same horses were subjected to a sham procedure and they were evaluated in the same times as in the CRET experiment. During treadmill exercise, locomotor parameters were measured with a triaxial accelerometer fixed in the pectoral region and in the sacrum midline.

Results

The sham procedure did not affect any of the accelerometric variables studied. CRET applications resulted in greater total powers, which resulted in absolute increased dorsoventral, mediolateral and longitudinal powers. However, a reduction in dorsoventral power expressed as a percentage of total power was found. Stride regularity increased. The greater total power resulted in longer stride length and because the velocity was kept fixed on the treadmill, stride frequency decreased. An accumulative effect of CRET application was only found in stride length and frequency.

Conclusions

It appears that CRET is a useful technique to enhance power and to elongate the stride at defined walk and trot velocities. The effect of these changes on performance should be studied for horses competing in different sport disciplines.

Evaluation of the effects of commonly used α2-adrenergic receptor agonists alone and in combination with butorphanol tartrate on objective measurements of lameness in horses

OBJECTIVE

To determine the effects of 3 α₂-adrenergic receptor agonists (α₂-ARAs), alone or in combination with butorphanol tartrate, on objective measurements of lameness in horses.

ANIMALS

17 adult polo horses with naturally occurring forelimb or hind limb lameness (or both).

PROCEDURES

In a crossover design, each horse received each protocol (saline [0.09% NaCl] solution [2 mL, IV] or xylazine hydrochloride [0.33 mg/kg, IV], detomidine hydrochloride [0.007 mg/kg, IV], or romifidine hydrochloride [0.033 mg/kg, IV] alone or in combination with butorphanol [0.007 mg/kg, IV]) in random order, with a washout period (≥ 7 days) between protocols. Horses were assessed immediately prior to (baseline) and 10, 15, 20, 30, and 40 minutes after administration of each protocol for degree of sedation, mechanical nociceptive threshold (MNT), and objective lameness measurements.

RESULTS

Compared with baseline values, sedation scores and MNTs were significantly higher at all evaluated time points following administration of all sedation protocols except xylazine alone; following administration of xylazine alone, sedation scores and MNTs were significantly higher at ≤ 30 minutes and ≤ 20 minutes, respectively. Significant differences in objective forelimb lameness measurements were noted after administration of the 3 α₂-ARA-butorphanol combinations. Most significant differences in objective measurements of hind limb lameness were detected after administration of detomidine or romifidine, alone or in combination with butorphanol.

CONCLUSIONS AND CLINICAL RELEVANCE

In the study horses, xylazine alone had the least impact on objective lameness measurements. The administration of α₂-ARAs, particularly detomidine or romifidine, alone or in combination with butorphanol, resulted in small but significant effects on objective lameness measurements.

A kinematic comparison of the locomotor pattern of horses sedated with detomidine alone and in combination with low doses of butorphanol

BACKGROUND

Chemical restraint is often used to perform diagnostic and minor surgical procedures; α₂ -adrenoceptor agonists are the most commonly used drugs; however, the combination with an opiate can induce a profound sedation. There is a lack of kinematic studies examining the effects of the combination of these drugs on locomotor patterns.

OBJECTIVES

The objective of the study was to evaluate the duration of the effects of sedation with detomidine and detomidine combined with a low dose of butorphanol on the movement patterns of horses.

STUDY DESIGN

The study was a controlled, randomised, blinded and crossover experiment.

METHODS

Each of six horses was injected intravenously with saline (0.9%) solution (10 mL), detomidine diluted in saline solution (0.01 mg/kg bwt) or a combination of detomidine (0.01 mg/kg bwt) and butorphanol (0.02 mg/kg bwt) diluted in saline solution, in a random order. A single accelerometer positioned at the sacrum was used for gait assessment 15 min before (baseline) and 5, 15, 30, 45, 60, 75, 90, 105 and 120 min after each injection. Eight variables were measured, including speed, stride frequency, stride length, regularity, dorsoventral power, propulsive power, mediolateral power and total power; force of acceleration and the three components of power were calculated. The degree of sedation was measured by the ground-to-lip distance.

RESULTS

There were significant differences among groups, with shorter effects after the injection of the combination of drugs, for most parameters.

MAIN LIMITATIONS

A small number of horses were involved in the study.

CONCLUSIONS

The combination of detomidine and butorphanol produces a shorter effect on almost all accelerometric parameters, probably due to the excitement produced by the opioid drug causing a quicker return to normal values. Accelerometry offers a method of objectively monitoring gait abnormalities in walking sedated horses.

Acepromazine inhibits hERG potassium ion channels expressed in human embryonic kidney 293 cells

The effects of acepromazine on human ether-à-go-go-related gene (hERG) potassium channels were investigated using whole-cell voltage-clamp technique in human embryonic kidney (HEK293) cells transfected with hERG. The hERG currents were recorded with or without acepromazine, and the steady-state and peak tail currents were analyzed for the evaluating the drug effects. Acepromazine inhibited the hERG currents in a concentration-dependent manner with an IC₅₀ value of 1.5 µM and Hill coefficient of 1.1. Acepromazine blocked hERG currents in a voltage-dependent manner between –40 and +10 mV. Before and after application of acepromazine, the half activation potentials of hERG currents changed to hyperpolarizing direction. Acepromazine blocked both the steady-state hERG currents by depolarizing pulse and the peak tail currents by repolarizing pulse; however, the extent of blocking by acepromazine in the repolarizing pulse was more profound than that in the depolarizing pulse, indicating that acepromazine has a high affinity for the open state of the channels, with a relatively lower affinity for the closed state of hERG channels. A fast application of acepromazine during the tail currents inhibited the open state of hERG channels in a concentration-dependent. The steady-state inactivation of hERG currents shifted to the hyperpolarized direction by acepromazine. These results suggest that acepromazine inhibits the hERG channels probably by an open- and inactivated-channel blocking mechanism. Regarding to the fact that the hERG channels are the potential target of drug-induced long QT syndrome, our results suggest that acepromazine can possibly induce a cardiac arrhythmia through the inhibition of hERG channels.