Heart rate in horses is a physiological parameter that reflects the number of heartbeats per minute. It is an important indicator of cardiovascular function and can be influenced by factors such as exercise, stress, excitement, and health status. Monitoring heart rate provides valuable insights into the horse's physical condition and can aid in assessing fitness levels or detecting potential health issues. In equine practice, heart rate is often measured using stethoscopes, heart rate monitors, or electrocardiograms. This page compiles peer-reviewed research studies and scholarly articles that explore the determinants, measurement techniques, and implications of heart rate variations in equine health and performance.
McConaghy FF, Hales JR, Hodgson DR.Heat-induced increases in skin blood flow (BF) are well known to be reduced if exercise is superimposed.' However, whether exercise-induced increases in muscle BF are compromised by superimposed heat stress remains a controversial issuc. The horse has now been studied because of its human-like thermoregulatory mechanisms and good exercise capacity.
Yamaya Y, Kubo K, Amada A, Sato K.The atrioventricular (AV) conductive functions were investigated before and after the pharmacological autonomic nervous blockade (PAB) through the electrophysiological study on six horses (AV block group) in which the dropped beats occurred more frequently (over 200 beats/24 hr) and on five horses (control group) in which the dropped beats occurred sporadically (under 200 beats/24 hr) or in which the arrhythmias were not recognized at all on the long-term electrocardiogram. As a result, AV conductivity, conduction time and refractoriness in the AV block group were lower, longer and higher, res...
Holcombe SJ, Derksen FJ, Stick JA, Robinson NE.To determine the effect of bilateral tenectomy of the tensor veli palatini muscle on soft palate and nasopharyngeal function in exercising horses. Methods: 5 Standardbreds. Methods: Treadmill videoendoscopy was performed on 5 Standardbreds exercising at 50, 75, and 100% of the speed that produced maximum heart rate; tracheal and pharyngeal pressures were measured before and after surgery. Tenectomy of the tensor veli palatini muscle was performed bilaterally on each horse while under general anesthesia, using a transoral approach. Results: Peak inspiratory tracheal pressures were significantly...
Thayer JF, Hahn AW, Pearson MA, Sollers JJ, Johnson PJ, Loch WE.High heart rate variability (HRV) has been associated with more efficient autonomic control, allowing more responsivity and sensitivity to changing environmental demands. Previous results from spectral analysis of interbeat intervals of equine heart rate (HR) indicated increased HRV, reflecting more effective vagal control of the heart. This study focuses on characterizing equine HR and HRV during increasing then decreasing physical demand. A non-invasive ambulatory monitoring system continuously records HR and HRV as horses exercise on a high speed equine treadmill at increasing then decreasi...
Feige K, Steiger R, Graf U, Schöberl M.Clinical signs of horses with peritonitis were colic (67.4%), elevated heart rate (53.2%), altered mucous membranes (75.8%), reduced intestinal motility (63.2%), increased tension of the abdominal wall (69.9%) and pyrexia (45.1%). The amount of obtained peritoneal fluid was increased in 62.3% of the horses. Colour and translucency of the peritoneal fluid were abnormal in 98.8% of the patients. The nucleated cell count was 83.5 (10-595) x 10(3)/microliter, protein content 35.6 g/l (+/-14.2), specific gravity 1027.3 (+/-7.4) and the relative amount of neutrophils was 87.8% (+/-11). The physical ...
Carroll GL, Matthews NS, Hartsfield SM, Slater MR, Champney TH, Erickson SW.Six ponies were used to investigate the effect of tolazoline antagonism of detomidine on physiological responses, behavior, epinephrine, norepinephrine, cortisol, glucose, and free fatty acids in awake ponies. Each pony had a catheter inserted into a jugular vein 1 hour before beginning the study. Awake ponies were administered detomidine (0.04 mg/kg intravenously [i.v.]) followed 20 minutes later by either tolazoline (4.0 mg/kg i.v.) or saline. Blood samples were drawn from the catheter 5 minutes before detomidine administration (baseline), 5 minutes after detomidine administration, 20 minute...
Thayer JF, Hahn AW, Sollers JJ, van Doornen L, Johnson PJ.Using a microprocessor controlled Ambulatory Monitoring System (AMS) developed by one of us (LvD), we have been studying the changes in and control of heart rate in the resting horse. The system provides us with InterBeat Intervals (IBI in milliseconds), motion sensing, and a time domain measure (mean successive differences: MSD) of heart rate variability for periods up to 72 hours. Thoracic impedance is also available but parameters for the equine chest are not currently available. The system is completely noninvasive, small, and carried on a surcingle worn by the subject. The equine subject ...
Young LE, Blissitt KJ, Bartram DH, Clutton RE, Molony V, Jones RS.In order to determine if transoesophageal Doppler echocardiography could be used to estimate cardiac output in anaesthetized horses, we have compared the technique with estimations of cardiac output by thermodilution in eight healthy adult thoroughbreds. Measurements of aortic blood flow velocity were made by high pulse repetition frequency (HPRF) and continuous wave (CW) Doppler echocardiography from a 3.5-MHz transoesophageal probe. Cardiac output was increased during the study by administration of dobutamine, providing a range of cardiac output measurements by thermodilution from 15.0 to 64...
Gottlieb-Vedi M, Essén-Gustavsson B, Lindholm A.Five Standardbred trotters performed treadmill exercise with incrementally increasing trotting velocities for 2 min intervals in three different tests until fatigue. Each test was performed with draught loads of either 10, 20 or 30 kilopond (kp). Each trotting interval was followed by 2 min periods at a walk without draught load. Recordings were made of heart rate (HR), respiratory rate (RR), plasma lactate (PLA) and stride frequency (SF) at the end of each trotting interval. The HR increased to average values of 191 +/- 10,203 +/- 10 and 214 +/- 7 bpm and PLA increased to 3.8 +/- 0.7, 7.3 +/-...
van Duijkeren E, Sloet van Oldruitenborgh-Oosterbaan MM, Breukink HJ, Vulto AG, van Miert AS.Twenty horses, ponies, and foals referred with acute diarrhoea were divided at random into two treatment groups. One group was treated intravenously with trimethoprim/ sulfadiazine and the other group with ampicillin/gentamicin. Both groups were given the same standardized symptomatic therapy. All animals were evaluated clinically and 5 variables (general impression, heart rate, rectal temperature, appetite, and consistency of the faeces) were estimated on a five point scale (0-4). Jugular blood samples were taken at admittance and at regular intervals for routine screening. Three blood variab...
Still J, Serteyn D, van der Merwe CA.Anaesthesia was induced in horses (n = 6) with a mixture of thiopentone and guaiphenesin and maintained by mechanical ventilation with a mixture of oxygen, air and isoflurane. Inspiratory and end-expiratory concentrations of oxygen, carbon dioxide and isoflurane were measured. Electrocardiography was used to evaluate heart rate and rhythm. Mean systemic arterial pressure (SAPm), pulmonary artery pressure (PAPm), right atrial pressure (RAPm) and pulmonary capillary wedge pressure (PCWP) were measured directly. Cardiac output was determined using the thermodilution method. Microcirculation in th...
Singh S, McDonell WN, Young SS, Dyson DH.To assess the usefulness of glycopyrrolate (GLY) in preventing the decrease in cardiac index (CI) usually caused by xylazine (XYL)/ketamine (KET)-induced anesthesia in horses. Methods: 6 healthy horses. Methods: Horses were treated with saline solution or 2.5 micrograms of GLY/kg of body weight, administered i.v. 15 minutes later, XYL (1 mg/kg) was administered i.v., followed 5 minutes later by KET (2 mg/kg) administration. The horses were positioned in left lateral recumbency, insufflated with 15 L of oxygen/min, and maintained for 30 minutes on the infusion of 0.05 mg of XYL and 0.1 mg of KE...
Grubb TL, Foreman JH, Benson GJ, Thurmon JC, Tranquilli WJ, Constable PD, Olson WO, Davis LE.Calcium gluconate was administered to conscious horses at 3 different rates (0.1, 0.2, and 0.4 mg/kg/min for 15 minutes each). Serum calcium concentrations and parameters of cardiovascular function were evaluated. All 3 calcium administration rates caused marked increases in both ionized and total calcium concentrations, cardiac index, stroke index, and cardiac contractility (dP/dtmax). Mean arterial pressure and right atrial pressure were unchanged; heart rate decreased markedly during calcium administration. Ionized calcium concentration remained between 54% and 57% of total calcium concentr...
Tetens J, Derksen FJ, Stick JA, Lloyd JW, Robinson NE.To evaluate the efficacy of prosthetic laryngoplasty with and without bilateral ventriculocordectomy for treatment of experimentally induced left laryngeal hemiplegia (LLH). Methods: 15 adult Standardbreds. Methods: Horses were allotted to 3 equal groups. Sham operation (group 1), prosthetic laryngoplasty (group 2), or prosthetic laryngoplasty with bilateral ventriculocordectomy (group 3) was performed after induction of LLH. Upper airway function testing was performed prior to left recurrent laryngeal neurectomy (LRLN), 14 days after LRLN, and 60 and 180 days after surgical treatment. Measure...
Chaffin MK, Matthews NS, Cohen ND, Carter GK.A commercially available pulse oximeter was evaluated in anaesthetised foals to determine its accuracy for estimating arterial haemoglobin saturation (SaO2). Five different transducer/transducer attachment site (TTAS) combinations were evaluated; 1-3) a fingertip transmission transducer attached to the foal's ear, lip and tongue, 4) an adhesive transmission transducer positioned on the foal's ear and 5) a forehead reflectance transducer placed on the ventral aspect of the foal's tail-base. Eight normal, Quarter Horse foals (age 5-10 days) were studied while under general anaesthesia. Alteratio...
Sysel AM, Pleasant RS, Jacobson JD, Moll HD, Modransky PD, Warnick LD, Sponenberg DP, Eyre P.Amphotericin B-induced synovitis of the left tarsocrural joint was used to create a grade 3 of 4 lameness in 11 horses. Caudal epidural catheters were placed and advanced to the lumbosacral region. Baseline heart and respiratory rates were recorded and horses were videotaped at a walk and trot. Morphine sulphate (0.2 mg/kg) and detomidine hydrochloride (30 micrograms/kg) were administered to treated horses (n = 8) through the epidural catheter; an equivalent volume of physiologic saline solution was administered to control horses (n = 3) through the catheter. At hourly intervals after epidural...
England GC, Clarke KW.In recent years the usefulness of the alpha 2 adrenoceptor agonist drugs has been recognized in equine practice. Several agents have become available and are now licensed for use in a number of countries. The principle actions of all alpha 2 adrenoceptor agonists are similar, in that they produce a reduction in heart rate and alteration of heart rhythm, an initial hypertension followed by a prolonged hypotension, a decrease in the cardiac output and respiratory depression. For clinical purposes, these agents produce sedation and analgesia, they are useful for premedication and markedly potenti...
Smith BL, Jones JH, Hornof WJ, Miles JA, Longworth KE, Willits NH.Stress associated with road transport is believed to be a significant contributor to the pathogenesis of post transport respiratory disease in horses. To determine the effects of road transport on pulmonary function, pulmonary aerosol clearance rates were measured in 4 horses 24 h before, and immediately after, 24 h of road transport by delivering aerosolised 99mtechnetium-labelled diethylenetriaminepentacetate (99mTc-DTPA) to the lungs and monitoring its washout. Each horse was transported twice, once while the trailer was equipped with a leaf-spring suspension and bias-ply tyres (trailer's o...
Manohar M, Goetz TE.Exercise-induced pulmonary hemorrhage (EIPH) is a common occurrence in racehorses. The objective of this study was to compare pulmonary vascular pressures of healthy Thoroughbred horses with and without postexertion endoscopically detectable fresh blood in the trachea. The nasopharynx, larynx, and trachea (down to the carina) of horses were examined weekly with an endoscope 55-60 min postexertion, and the diagnosis of EIPH was confirmed by the presence of fresh blood in the trachea. Measurements of heart rate and right atrial, pulmonary arterial, and pulmonary arterial wedge pressures were mad...
Kerr CL, McDonell WN, Young SS.The purpose of this study was to compare and evaluate sedation with intravenous xylazine (1.1 mg/kg bodyweight [BW]) versus intravenous romifidine (100 micrograms/kg BW) followed by induction of anesthesia with intravenous diazepam (0.04 mg/kg BW) and ketamine (2.2 mg/kg BW). Twelve healthy horses were used in a blinded, randomized, cross-over design. Heart rate, presence of 2nd degree atrioventricular heart blocks (2 degrees AVB), respiratory rate, arterial blood pressures, blood gases, packed cell volume, total serum proteins, and duration of anesthesia and recumbency were recorded. Inductio...
Bettschart-Wolfensberger R, Taylor PM, Sear JW, Bloomfield MR, Rentsch K, Dawling S.To examine the physiologic and pharmacokinetic effects of a technique of total intravenous anesthesia in ponies. Methods: 6 healthy ponies. Methods: Ponies were premedicated with acepromazine (0.03 mg/kg of body weight, IV) and xylazine (1.0 mg/kg, IV). Two minutes later, anesthesia was induced with ketamine (2.0 mg/kg, IV) followed by climazolam (0.2 mg/kg, IV). Anesthesia was maintained for 120 minutes by an infusion of climazolam (0.4 mg/kg/h) and ketamine (6.0 mg/kg/h). Oxygen (5 L/min) was supplemented. 20 minutes after the infusion was stopped sarmazenil (0.04 mg/kg, IV) was administered...
The Journal of physiologySeptember 15, 1996
Volume 495 ( Pt 3), Issue Pt 3 863-874 doi: 10.1113/jphysiol.1996.sp021638
Mills PC, Marlin DJ, Demoncheaux E, Scott C, Casas I, Smith NC, Higenbottam T.1. The effects of exercise on the production rate of nitric oxide (NO) in exhaled air (VNO) and the effects of inhaled NO (80 p.p.m.) on cardiovascular and respiratory parameters were investigated in five Throughbred horses. 2. The concentration of NO ([NO]) in exhaled air collected from within the nasal opening was lower when collected at a high flow rate of 80 l min-1 than at a low flow rate of 20 l min-1: when trotting at 3.7 m s-1 the values were 0.78 +/- 0.15 and 1.23 +/- 9.14 p.p.b., respectively, and when cantering at 9 m s-1 the values were 1.69 +/- 0.31 and 2.25 +/- 0.32 p.p.b., respe...
Milne EM, Doxey DL, Woodman MP, Cí·¯ord D, Pearson RA.A clinical trial was carried out to determine the effect of cisapride on rate of passage of digesta and clinical parameters in horses with chronic grass sickness. Sixteen horses were given intramuscular cisapride (0.1 mg kg-1 three times daily) (group I), and 15 received oral cisapride (0.8 mg kg-1 three times daily) (group O). A liquid-phase marker (cobalt-EDTA) and a solid-phase marker (polystyrene pellets) were given by stomach tube at the beginning of each of three consecutive 7 day periods, i.e., before, during and after cisapride therapy. Seven horses in each group completed the rate of ...
Manohar M, Goetz TE, Griffin R, Sullivan E.To determine the effects of phenylbutazone administration on heart rate and right atrial and pulmonary vascular pressures in Thoroughbreds during rest and during exercise performed at maximal heart rate. Methods: 7 healthy, exercise-conditioned Thoroughbreds. Methods: Horses were studied on 3 occasions: without medication [control], after i.v. administration of phenylbutazone (4.4 mg/kg of body weight) at 12-hour intervals for 2 days and a final dose given 1 hour before exercise, and after i.v. administration of phenylbutazone for 2 days in the same manner, but with the final dose given 24 hou...
Holcombe SJ, Derksen FJ, Stick JA, Robinson NE, Boehler DA.To compare tracheal and pharyngeal inspiratory and expiratory pressures achieved during 60 seconds of nasal occlusion in standing horses with pressures achieved in horses during intense exercise. Methods: 5 Standardbreds. Methods: Tracheal and pharyngeal inspiratory and expiratory pressures were obtained from 5 horses during 60 seconds of nasal occlusion and compared with tracheal and pharyngeal pressures achieved during incremental treadmill exercise tests in which horses ran at 50, 75, and 100% of the speed that resulted in maximal heart rate (HRmax). Results: Significant difference was not ...
Fairbairn SM, Marr KA, Lees P, Cunningham FM, Page CP.Antigen challenge is known to cause the recruitment of neutrophils to the lungs of horses with chronic obstructive pulmonary disease (COPD). To evaluate a possible role of platelet activating factor (PAF) in this process, the effects of PAF on the distribution of radiolabelled neutrophils were compared in normal horses and asymptomatic horses with COPD. Changes in lung function, heart rate and the distribution of platelets and eosinophils were also measured. PAF (5 ng kg-1 intravenously) caused immediate but transient increases in the number of radiolabelled neutrophils in the lungs and a conc...
Kuwahara M, Hashimoto S, Ishii K, Yagi Y, Hada T, Hiraga A, Kai M, Kubo K, Oki H, Tsubone H, Sugano S.We studied power spectral analysis of heart rate (HR) variability in the horse, with the hypothesis that the quantitative information provided by the spectral analysis of HR variability reflects the interaction between sympathetic and parasympathetic regulatory activities. For this purpose, electrocardiogram, blood pressure (BP) and respiratory (Resp) waveform were simultaneously recorded from Thoroughbred horses (3-5 years old) and analyzed by power spectrum. There were two major spectral components at low-frequency (LF) and high-frequency (HF) bands for HR variability. The peak of Resp varia...
Clarke KW, Song DY, Alibhai HI, Lee YH.Cardiopulmonary parameters were measured in 12 ponies (small horses) before anaesthesia and, following induction with xylazine and ketamine, during maintenance of anaesthesia with desflurane. In six of the ponies (group A) anaesthesia was maintained for three hours with desflurane at an end-tidal concentration of 7.4 per cent. In the other six ponies (group B), anaesthesia was maintained in the same way for one hour and then the effects of end-tidal desflurane concentrations of 7.4 per cent and 9.6 per cent with and without artificial ventilation were investigated. In group A ponies the arteri...
Luna SP, Taylor PM, Wheeler MJ.Six Welsh gelding ponies (weight 246 +/- 6 kg) were premedicated with 0.03 mg/kg of acepromazine intravenously (i.v.) followed by 0.02 mg/kg of detomidine i.v. Anaesthesia was induced with 2 mg/kg of ketamine i.v. Ponies were intubated and lay in left lateral recumbency. On one occasion anaesthesia was maintained for 2 h using 1.2% halothane in oxygen. The same group of ponies were anaesthetized 1 month later using the same induction regime and anaesthesia was maintained with a combination of detomidine, ketamine and guaiphenesin, while the ponies breathed oxygen-enriched air. Electrocardiogra...
Moore RM, Charalambous AC, Masty J.To measure colonic arterial (CA) and colonic venous (CV) plasma neuropeptide concentrations during low-flow ischemia and reperfusion of the large colon in horses. Methods: 10 adult horses. Methods: CA and CV plasma samples collected from anesthetized horses during experimentally induced low-flow colonic ischemia and reperfusion were assayed for vasoactive intestinal polypeptide (VIP), calcitonin gene-related peptide (CGRP), and substance P (SP), using radioimmunoassays. In 6 anesthetized horses, colonic ischemia (20% of baseline (BL]) was maintained for 3 hours, then blood flow was restored an...
Lee YL, Clarke KW, Alibhai HI, Song DY.To evaluate the effect of ephedrine on intramuscular blood flow and hemodynamic parameters during equine anesthesia. Methods: Prospective experimental study. Methods: Six healthy adult Welsh Mountain ponies (five males, one female, mean weight: 267 kg, range: 213-347 kg). Methods: Halothane-anesthetized ponies received an IV bolus of ephedrine (0.1 mg kg), followed 30 minutes later by a second IV ephedrine injection (0.2 mg kg). Changes in intramuscular blood flows (IMBF) in upper and lower triceps brachii were measured by laser Doppler flowmetry. Cardiopulmonary measurements were made at inte...
Cable CS, Ducharme NG, Hackett RP, Erb HN, Mitchell LM, Soderholm LV.To investigate whether upper airway sounds of horses exercising with laryngeal hemiplegia and alar fold paralysis have distinct sound characteristics, compared with unaffected horses. Methods: 6 mature horses. Methods: Upper airway sounds were recorded in horses exercising on a high-speed treadmill at maximum heart rate (HR(MAX)) under 3 treatment conditions (ie, normal upper airway function [control condition], and after induction of left laryngeal hemiplegia or bilateral alar fold paralysis) in a randomized crossover design. Fundamental frequency, spectrograms using Gabor transform, and inte...
Rutkowski JA, Eades SC, Moore JN.A chronic model with an ultrasonic transit time blood flow probe and strain gauge force transducers implanted on the cecum was used to evaluate cecal mechanical activity and cecal arterial blood flow in 4 conscious adult horses. Intravenous administration of xylazine (1.1 mg/kg of body weight) significantly decreased heart rate and cardiac output, but significantly increased diastolic pulmonary arterial pressure, mean pulmonary arterial pressure, carotid arterial pressure, and central venous pressure. Lateral cecal arterial blood flow after xylazine administration was decreased substantially m...
Miller PJ, Holmes JR.Observations on seven cases of mitral insufficiency are described. Three of the horses had recent histories of cardiac failure and formed a separate group in which there were marked haemodynamic changes which varied in relation to heart rate but were associated with pulmonary hypertension, elevated right ventricular pressure and low peak left ventricular pressure. In the other four horses the heart appeared to be compensating at rest but to be unable to cope with severe exertion. On auscultation, a widespread pansystolic murmur and a prominent third heart sound were characteristic of the left ...
Minero M, Canali E, Ferrante V, Verga M, Odberg FO.The heart rate and behaviour of 14 adult saddle horses, eight crib-biters and six normal controls, were investigated. Initially, the relationship between crib-biting and heart rate was investigated while the horses were undisturbed. The horses were tested when restrained with a lip twitch, and assessed when they were exposed suddenly to the rapid inflation of a balloon. The heart rate of the crib-biters during crib-biting was lower than during other behaviours. The crib-biters had a higher overall mean heart rate (P<0.05) suggesting that they may have had a higher basal sympathetic activity...
Robinson MA, Guan F, McDonnell S, Uboh CE, Soma LR.Dermorphin is a μ-opioid receptor-binding peptide that causes both central and peripheral effects following intravenous administration to rats, dogs, and humans and has been identified in postrace horse samples. Ten horses were intravenously and/or intramuscularly administered dermorphin (9.3 ± 1.0 μg/kg), and plasma concentration vs. time data were evaluated using compartmental and noncompartmental analyses. Data from intravenous administrations fit a 2-compartment model best with distribution and elimination half-lives (harmonic mean ± pseudo SD) of 0.09 ± 0.02 and 0.76 ± 0.22 h, respe...
Sampson SN, Tucker RL, Bayly WM.We evaluated the relationships of heart score (HS) and echocardiographic measures to maximal oxygen consumption (VO2max), maximal cardiac output (Qmax), and maximal stroke volume (SVmax). Six fit, mature Thoroughbred horses weighing (mean +/- s.e.) 487 +/- 11 kg were run 4 times on an inclined (10%) treadmill. Each run consisted of a 3 min warm-up at 4 m/s followed by completion of an incremental exercise test in which each horse ran until VO2max was reached. Arterial and mixed venous blood was collected to determine arteriovenous oxygen content difference C(a-v)O2[ in the last 15 s of exercis...
Matthews NS, Hartsfield SM, Sanders EA, Light GS, Slater MS.All 43 horses anaesthetised for colic surgery were premedicated with xylazine or diazepam. Anaesthesia was induced with guaifenesin and ketamine, horses were placed in dorsal recumbency and anaesthesia was maintained with isoflurane in oxygen and mechanical ventilation. Haemoglobin saturation readings (SpO2) were taken with a pulse oximeter and compared with computed haemoglobin saturation (SaO2) from arterial blood samples. Readings were taken over a range of SaO2 of 78-100%, mean arterial blood pressure ranged from 24 to 108 mmHg and PaO2 ranged from 53 to 490 mmHg. Analysis of 107 readings ...
Gehlen H, Bubeck K, Stadler P.In 12 healthy warmblood horses and 10 horses with mitral valve insufficiencies (MVI) of various degrees heart rate and pulmonary artery wedge pressure (PWP) was measured at rest and during standardised exercise on a high speed treadmill. There was a significant increase in PWP with each change in speed of the treadmill (p < 0.01). The PWP of horses with mild mitral valve regurgitation under working conditions was not significantly different compared to the healthy horses. The horses with moderate mitral valve regurgitation showed a significant higher pulmonary artery wedge pressure at rest and...
Afonso T, Giguère S, Brown SA, Barton MH, Rapoport G, Barba M, Dembek KA, Toribio RE, Coleman AE.Despite the paucity of data available, orally administered angiotensin-converting enzyme (ACE) inhibitors are empirically used in horses with valvular regurgitation. Objective: Evaluate the echocardiographic and hormonal changes in response to oral benazepril in horses with left-sided valvular regurgitation. Methods: Prospective, randomised double-blind, placebo-controlled trial. Methods: Horses with mitral valve (MR) and/or aortic valve regurgitation (AR) received oral benazepril (n = 6) at a dosage of 1 mg/kg q 12 h or a placebo (n = 5) for 28 days. Echocardiography was performed before drug...
Neudeck S, Kästner SBR, Wittenberg-Voges L, Rohn K, Hopster K.OBJECTIVE To determine global and peripheral perfusion and oxygenation during anesthesia with equipotent doses of desflurane and propofol combined with a constant rate infusion of dexmedetomidine in horses. ANIMALS 6 warmblood horses. PROCEDURES Horses were premedicated with dexmedetomidine (3.5 μg•kg, IV). Anesthesia was induced with propofol or ketamine and maintained with desflurane or propofol (complete crossover design) combined with a constant rate infusion of dexmedetomidine (7 μg•kg •h). Microperfusion and oxygenation of the rectal, oral, and esophageal mucosa were measured bef...
McKiernan BC, Koritz GD, Scott JS, Berney C, Robinson NE.Six ponies with recurrent obstructive lung disease were studied during two separate 60 min periods while receiving constant equal volume infusions of either aminophylline or sterile water. Dynamic lung compliance, pulmonary resistance, respiratory rate, tidal volume, blood gas tensions and heart rate were measured. Plasma samples were obtained for determination of theophylline concentrations before, and at 10 min intervals during, the infusion period. Excitability was assessed subjectively at these same time periods. The plasma theophylline concentrations in ponies were well predicted by a pre...
Gehlen H, Stadler P.Clinical, electrocardiographic and echocardiographic examinations were conducted before therapy and 4 days after conversion to normal sinus rhythm in 15 horses with a history of atrial fibrillation of 2-6 months duration. Seven horses showed no other signs of cardiac disease. Four horses suffered additionally from mitral valve insufficiency, while six horses had aortic valve insufficiency, including two of the four horses with mitral valve insufficiency, but none had signs of congestive heart failure. Doppler echocardiographic estimates of various variables were made for assessment of systolic...
Hyyppä S, Saastamoinen M, Pösö AR.Nine adult riding horses performed on a treadmill a competition exercise test (CET) and 24 h later a standardised exercise test (SET) at mean temperature 28 degrees C and relative humidity 58%. Each horse performed the tests 5 times at 2 week intervals. The horses were given isotonic glucose-electrolyte solution via a nasogastric tube 30 min after the CET, except after the last trial when water was given. Blood lactate, plasma concentration of aldosterone, arginine vasopressin, protein, sodium, potassium, chloride, magnesium and calcium were measured. Heart rate at blood lactate concentration ...
Art T, Lekeux P.A preliminary study attempted to assess the influence of atmospheric conditions on the breathing pattern of ponies. The respiratory airflow, tidal volume, breathing frequency, minute volume, total pulmonary resistance and heart rate of five ponies (257 +/- 9 kg and three to five years old) were measured by a standardised procedure. Data were collected at rest, during a nine minute period of treadmill exercise and during a five minute recovery period. The ambient temperature (degrees C) and relative humidity (%) were recorded at the time of each investigation and the respiratory parameters were...
Barrey E, Galloux P, Valette JP, Auvinet B, Wolter R.The purpose of this study was to define the most suitable treadmill slope for reproducing the same heart rate response as in horses being ridden on a track. Seven French saddle horses were exercised first on a level turf track and then on a treadmill. On the track the exercise test consisted of four periods of three minutes of increasing speeds at the trot and the gallop (96 to 600 m/minute). The treadmill exercise tests consisted of seven steps of increasing slope (0 to 9.6 per cent) at the trot (252 m/minute), followed, after an active recovery period at the walk with a 0 per cent slope, by ...
Jones DL.The effectiveness of detomidine with or without atropine sulfate premedication in producing sedation and analgesia for arthrocentesis was studied in 12 horses. The effects were evaluated by monitoring heart and respiratory rates, borborygmi, distance from the lower lip to the floor, systolic blood pressure, and response to needle insertion. Either atropine or saline (as a placebo) was administered immediately prior to detomidine. All drugs were administered intravenously. Measurements were taken prior to drug injection and at 1, 5, 10, 15, 20, 25, 30, 40, 50, 60, 120, 180 and 240 minutes posti...
Miller PJ, Holmes JR.Beat-to-beat variation in the amplitude of the QRS waveform from 13 horses with second degree partial atrioventricular block was examined using an orthogonal lead (X,Y,Z) system. The peak positive deflections (XR, YR and ZR) and peak negative deflections (XQS, YS and ZQ) were regressed against PR and RR intervals. XQS was used to indicate that the peak negative deflection in X could have been a Q or S wave. XR and YR were directly related to PR (P less than 0.001) and XQS and YS were inversely related to PR (P less than 0.001). YR was also directly related to RR (P less than 0.001) but not so ...
Manohar M, Goetz TE, Griffin R, Sullivan E.To determine the effects of phenylbutazone administration on heart rate and right atrial and pulmonary vascular pressures in Thoroughbreds during rest and during exercise performed at maximal heart rate. Methods: 7 healthy, exercise-conditioned Thoroughbreds. Methods: Horses were studied on 3 occasions: without medication [control], after i.v. administration of phenylbutazone (4.4 mg/kg of body weight) at 12-hour intervals for 2 days and a final dose given 1 hour before exercise, and after i.v. administration of phenylbutazone for 2 days in the same manner, but with the final dose given 24 hou...
Razavizadeh AT, Mashhadi AG, Paphan AA.An observational field study was performed on a well-know purebred horses in Iran (Khozestan-Arab horse). The study was conducted on 105 apparently healthy horses. To find the prevalence of cardiac dysrhythmias in different sexes and ages, the horses were divided into 2 sexes (63 females and 42 males) and three age groups (0-4, 4-8, > 8 years old). After taking the history and performing clinical examination, ECG was obtained on a base apex lead system with the paper speed of 25 mm sec(-1) and sensitivity of 10 or 5 mm mv(-1) at rest. The electrocardiograms were evaluated according to the crit...
Jenny JCA, Hopster K, Hurcombe SD.To compare the accuracy and precision of cardiac output (CO) measurements derived from 4 thermodilution protocols that used different injectate temperatures and volumes in healthy adult horses. Methods: 8 healthy adult horses. Methods: Horses were anesthetized and instrumented with Swan-Ganz catheters. The CO was derived from each of 4 thermodilution protocols (IV injection of physiologic saline [0.9% NaCl] solution chilled to < 5 °C at volumes of 1 mL/15 kg of body weight [protocol A; control], 1 mL/25 kg [protocol B], and 1 mL/35 kg [protocol C] or maintained at 17 °C at a volume of 1 m...
Pradella GD, Taschetto PM, Duarte CA, da Silva Azevedo M, Góss GC.Adverse drug reactions in horses are rare. The antimicrobials are in the list of the most common drugs associated with reaction in horses. The aim of this report is to describe the clinical presentation of an adverse drug reaction after the intramuscular administration of ceftiofur hydrochloride. A 5-year-old crioulo broodmare at one day postpartum presented signs of difficulty to walk, positive pulse in the four limbs, and heart rate of 80 beats per minute (bpm), with a history of fighting with another mare. The clinical suspicions were rhabdomyolysis and laminitis. Initially a dose of flunix...
Murray JK, Senior JM, Singer ER.Short format 3-day events were introduced in 2004. Anecdotal reports suggested that horses were more tired on completion of the cross-country phase of short format events when compared with horses completing the cross-country phase of long format competitions, despite the absence of Phases A, B and C. Objective: To compare the physiological parameters and haematological parameters of horses that had completed the cross-country phase of a short format (SF) and a long format (LF) CCI 2* competition. Methods: During a CCI 2* competition 69 competitors took part in the short format and 74 in the l...
Schumacher SA, Toribio RE, Lakritz J, Bertone AL.The objective of this study was to characterize the pharmacokinetics and pharmacodynamics of intravenous administration of magnesium sulfate to horses using a novel radio-telemetry system for physiologic signal capture. Five Horses were surgically implanted with a radio-telemetric carotid catheter. Implants were paired with a non-invasive telemetric unit which acquired a six lead ECG and 3-axis acceleration to assess activity acquired wirelessly in real-time for future analysis. Horses were exposed to a new stall environment before (baseline) and after 60 mg/kg (30 mL) of magnesium sulfate (Mg...
Art T, Votion D, Lekeux P.The purpose of this study was 1) to measure and compare some physiological parameters in horses during a standardised treadmill exercise performed either in temperate atmospheric conditions (TC) (ambient temperature: 15 degrees C; relative humidity: 55%), or in hot and humid conditions (HHC) (ambient temperature: 30 degrees C; relative humidity: 75%) and 2) to follow the recovery of the same horses during 1 h after both tests. Five healthy fit Standardbred horses were investigated twice at 8 days interval, in TC and in HHC. Some measurements were made during a standardised treadmill exercise t...
Amado-Fuentes M, Gozalo M, Garcia-Gomez A, Barrios-Fernandez S.People with disabilities due to genetic origin often present high levels of stress: non-pharmacological interventions such as Equine-Assisted Interventions (EAI) may be a useful strategy. The objective of this pilot study was to evaluate stress levels in two participants with 22q11.2 deletion syndrome diagnosis, immediately after carrying out the EAI. A single case experimental design methodology was chosen due to the small sample size. Two participants with 22q11.2 Deletion Syndrome, a rare disease, with different comorbidities were included. The present study considered the EAI as the indepe...
Gittel C, Schulz-Kornas E, Sandbaumhüter FA, Theurillat R, Vervuert I, Larenza Menzies MP, Thormann W, Braun C.To evaluate the pharmacokinetics and selected pharmacodynamic effects of a commercially available l-methadone/fenpipramide combination administered to isoflurane anaesthetized ponies. Methods: Prospective single-group interventional study. Methods: A group of six healthy adult research ponies (four mares, two geldings). Methods: Ponies were sedated with intravenous (IV) detomidine (0.02 mg kg) and butorphanol (0.01 mg kg) for an unrelated study. Additional IV detomidine (0.004 mg kg) was administered 85 minutes later, followed by induction of anaesthesia using IV diazepam (0.05 mg kg) and keta...
Ellis EJ, Ravis WR, Malloy M, Duran SH, Smyth BG.Six horses were administered either 15 or 20 mg/kg body weight (b.w.) procainamide (PA) as an intravenous (i.v.) dose over 10 min. The plasma concentrations of PA and N-acetylprocainamide (NAPA) as well as the pharmacodynamic effect (prolongation of the QT interval) were monitored. The PA plasma concentrations could be described by a one-compartment model with a t1/2 of 3.49 +/- 0.61 h. The total body clearance of PA was 0.395 +/- 0.090 l/hr/kg and the volume of distribution was 1.93 +/- 0.27 l/kg. As observed after PA administration, NAPA (an active metabolite) had a t1/2 longer than PA of 6....
Mercer MA, Davis JL, McKenzie HC, Messenger KM, Schaefer E, Council-Troche RM, Werre SR.Acetaminophen has been evaluated in horses for treatment of musculoskeletal pain but not as an antipyretic. Objective: To determine the pharmacokinetics and efficacy of acetaminophen compared to placebo and flunixin meglumine in adult horses with experimentally induced endotoxemia. Methods: Eight university owned research horses with experimentally induced endotoxemia. Methods: Randomized placebo controlled crossover study. Horses were treated with acetaminophen (30 mg/kg PO; APAP), flunixin meglumine (1.1 mg/kg, PO; FLU), and placebo (PO; PLAC) 2 hours after administration of LPS. Plasma ...
Young LE, Blissitt KJ, Clutton RE, Molony V.To describe the haemodynamic effects of a 60 min infusion of dopamine 4 microg/kg bwt/min during halothane anaesthesia, 7 mature Thoroughbred horses were studied. The infusion began 1 h after induction of anaesthesia by romifidine (100 microg/kg) and ketamine (2.2 mg/kg bwt). Throughout the period of dopamine infusion and for 30 min after its discontinuation, the horses were ventilated by intermittent positive pressure to maintain PaCO2 between 4.6-5.4 KPa. Inspired halothane concentration was adjusted to maintain an end tidal halothane concentration of 0.9%. Haemodynamic variables were measur...
