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.
Shirer HW, Erichsen DF, Orr JA.Previous reports indicate that intravenous infusion of HCl can alter breathing and blood pressure even if reductions in systemic arterial pH are prevented. To extend these findings, as well as to determine whether other acids elicit comparable results, this report compares the cardiopulmonary response between right atrial infusion of lactic acid and HCl in awake ponies. Lactic acid, infused at a dose of 1.5 mmol/kg over 18 min, lowered systemic and pulmonary arterial pH 0.062 and 0.092 U, respectively, and increased pulmonary arterial pressure (delta Ppa, 4 mmHg), heart rate (HR, 4/min), and t...
Hildebrand SV, Arpin D.Neuromuscular and cardiovascular effects of atracurium, a nondepolarizing neuromuscular blocking agent, were evaluated in 10 halothane-anesthetized adult horses. Hind limb digital extensor tension (hoof twitch) was measured with a strain gauge to quantitate the muscle relaxant effects of atracurium. Response of facial muscles was compared with hoof twitch. Five injections of atracurium were given. Initial mean (+/- SEM) dosage of 0.07 +/- 0.01 mg of atracurium/kg of body weight caused 98.6 +/- 0.8% reduction of the preinjection hoof twitch. Subsequent dosages of 0.04 +/- 0.003 mg/kg induced a ...
Bertone JJ.Six standing awake adult horses were instrumented for measurement of mean arterial, central venous, and pulmonary arterial blood pressures (mm of Hg), thermodilution cardiac output (ml/kg/min), and pulmonary arterial blood temperature (C). Total peripheral resistance was calculated from these values. Base-line data were accumulated, and a single dose of hydralazine HCl (0.5 mg/kg) was administered IV. Horses were monitored for 420 minutes after hydralazine administration. Mean arterial and central venous blood pressures did not change from the base-line values. Cardiac output and heart rate we...
Clark ES, Thompson SA, Becht JL, Moore JN.Mechanical activity of the cecal body, lateral cecal arterial blood flow, carotid arterial pressure, and heart rate were measured in 6 conscious healthy horses 30 minutes before and for 120 minutes after IV administration of xylazine at dosages of 1.1 mg/kg of body weight, 0.55 mg/kg, and 0.275 mg/kg. Xylazine at a dosage of 1.1 mg/kg reduced the mean motility index (the product of the mean amplitude of contractions and the total duration of contractile activity divided by the recording time) of the circular and longitudinal muscle layers for the first, second, third, and fourth 30-minute peri...
Evans DL, Rose RJ.A rapid incremental treadmill exercise test was used to determine the repeatability of the following measurements in exercising horses: maximal oxygen consumption (VO2max), maximal heart rate (HRmax), velocity at a heart rate of 200 beats/min (V-200), oxygen consumption at a heart rate of 200 beats/min (VO2-200), oxygen consumption at HRmax (VO2-HRmax), work rate at a heart rate of 200 beats/min (W-200), work rate at HRmax (W-HRmax) and treadmill velocity at HRmax (V-HRmax). Six Standardbred geldings were exercised on three separate occasions on a treadmill set at an inclination of 6 degrees. ...
Evans DL, Rose RJ.Cardiovascular and respiratory responses to submaximal exercise training were investigated in 6 thoroughbred racehorses. Oxygen uptake, heart rate (HR) and arteriovenous oxygen content difference were measured during incremental treadmill exercise tests, before and after 7 weeks of treadmill training. Cardiac output during exercise was calculated by the direct Fick technique. Maximal oxygen uptake (VO2max) was increased by 23% after training, from 129.7 ml/kg/min to 160.0 ml/kg/min. The treadmill speed at which VO2max was attained increased by 19%. The increased aerobic power after training wa...
Evans DL, Rose RJ.The effects of a respiratory gas collection mask on arterial blood gases, acid base values, oxygen content, respiratory frequency and heart rate, were investigated in standardbred horses during treadmill exercise at speeds up to 10 m sec-1 and a treadmill slope of 10 per cent. The mask had no significant effect on heart rates during exercise, but respiratory frequency was lower when the mask was used. The increase in respiratory frequency as treadmill velocity increased was also significantly slower with the mask operative. Arterial carbon dioxide tensions were significantly higher during exer...
McCarthy RN, Hutchins DR.A retrospective analysis of 74 cases that underwent surgery for colic was undertaken to determine short and long term survival rates and the incidence of post-operative complications. In 28 cases colic was related to small intestinal lesions and in 46 cases to large intestinal lesions. Pre-operative packed cell volume and heart rate were found to be inversely related to short-term survival. Twenty-five horses (34%) recovered from surgery and were discharged. Of 18 of these cases with available histories, 6 subsequently had one or more episodes of colic since surgery of which 5 eventually died ...
MacHarg MA, Foerner JJ, Phillips TN, Barclay WP.The medical management of three horses with simple and strangulating small intestinal obstructions was unsuccessful and was therefore supported by surgical bypasses. Jejunocecostomies were used to treat horses with postoperative paralytic ileus that was unresponsive to medical management. These horses had abdominal pain, gastric distention, heart rate elevations greater than 60/minute, and small intestinal distention on rectal palpation. Two horses experienced weight loss which responded to bypass removal. The bypass effectively decreased the need for intravenous fluid administration and repea...
Evans DL, Rose RJ.Six Standardbred horses were used to evaluate the time course of pulmonary gas exchange, ventilation, heart rate (HR) and acid base balance during different intensities of constant-load treadmill exercise. Horses were exercised at approximately 50%, 75% and 100% maximum oxygen uptake (VO2 max) for 5 min and measurements taken every 30 s throughout exercise. At all work rates, the minute ventilation, respiratory frequency and tidal volume reached steady state values by 60 s of exercise. At 100% VO2 max, the oxygen consumption (VO2) increased to mean values of approximately 130 ml/kg.min, which ...
Landgren GL, Gillespie JR, Fedde MR, Jones BW, Pieschl RL, Wagner PD.We studied mechanisms of O2 transport in 6 adult (2-5 year old) horses at rest and during steady-state exercise on a treadmill (0% slope) at 12 m/s (a submaximal gallop). Oxygen consumption was measured using an open-flow system. Arterial and mixed venous blood samples were simultaneously obtained for measurement of O2 content and hemoglobin concentration. VO2 increased from 1.5 +/- 0.2 L/min at rest to 46.2 +/- 4.8 L/min during exercise. HR increased from a resting value of 36.9 +/- 2.5 bpm to 196.5 +/- 10.9 bpm and the arterio-venous O2 content difference (a-v O2) increased from 4.2 +/- 0.8 ...
Art T, Lekeux P.Exercise-induced variations in their ventilatory mechanics were studied in 8 healthy ponies 4.2 +/- 1.4 years old and weighing 282 +/- 11 kg. Airflow (V), tidal volume (VT), esophageal pressure, mask pressure and electrocardiogram were simultaneously recorded before, during and after a treadmill (incline 8.3 degrees) exercise which consisted of 2 min walking (1.5 m.sec-1), 3 min slow trotting (3.0 m.sec-1) and 3 min fast trotting (3.5 m.sec-1). The results of three consecutive daily measurements were averaged for each pony. Heart rate, minute volume (Ve), respiratory frequency (f) and peak ins...
Littlejohn A, Snow DH.These studies investigated circulatory, respiratory and metabolic responses in four Thoroughbred geldings during the first 400 metres of galloping (mean speed 14.4 +/- 0.38 m.s-1), cantering (mean speed 10.0 +/- 0.61 m.s-1) and walking (mean speed 1.58 +/- 0.05 m.s-1) from a standing start. A radio-controlled device which collected blood samples anaerobically during each 100 m section of the exercise track allowed analyses of changes in and functional relationships of the variables measured. During the 400 m gallop, the mean heart rate (HR) increased from 125 to 201 beats.min-1 and the haemato...
Yang JM, Woods WE, Weckman TJ, Wood TW, Chang SL, Blake JW, Tobin T.1. Drug administration studies using diisopropylamine dichloroacetate (DADA) and diisopropylamine (DIPA) were conducted in Thoroughbred and Standardbred horses to assess physiological effects and develop detection methods. 2. Four horses received 0.08 mg DADA/kg body wt and showed no changes in heart and respiratory rates or body temperature as measured over a 1-hr period after administration. A transient diuretic effect was found to occur in 2 mares dosed with 0.80 mg DADA/kg body wt. 3. A qualitative detection method using thin-layer chromatography was developed to detect DIPA, the major met...
Evans DL, Rose RJ.Six detrained Thoroughbred horses performed incremental treadmill tests. Maximal oxygen uptake (VO2max) was measured during exercise by analysis of expired gas. The relationships between oxygen consumption (VO2) and work rate, heart rate (HR), cardiac output (Q), stroke volume (SV) and arteriovenous oxygen content difference [C(a-v)O2] were examined during submaximal and maximal exercise. The relative contributions of blood flow and extraction of oxygen from muscle capillaries were assessed during exercise at VO2max. Mean VO2max was 129.7 +/- 2.9 (mean +/- S.E.M.) ml kg-1 min-1, which occurred...
Reef VB, Levitan CW, Spencer PA.Sixty-seven horses presented with atrial fibrillation (AF) from January 1, 1980 to August 1, 1986. All horses were evaluated for the type and severity of the underlying cardiac disease and the probable duration of the arrhythmia. Fifty-two (78%) of the horses were treated with quinidine sulfate and/or digoxin. The response to treatment was assessed in each horse. Horses were followed for periods extending from 8 months to 7 years. Standardbreds, young horses, and males predominated in the study group. There were more male horses (stallions and geldings) than mares. Most horses with AF had no e...
Weber JM, Dobson GP, Parkhouse WS, Wheeldon D, Harman JC, Snow DH, Hochachka PW.This study characterizes the effects of exercise on the cardiac output (Q) and the metabolic rate (VO2) of trained Thoroughbred racehorses. Heart rate, Q, and arteriovenous (a-v)O2 difference were measured at rest and at three levels of submaximal treadmill exercise (1.6 m/s walk and 3-4 m/s trot at 6% incline, and 6.5 m/s horizontal canter). Heart rate and (a-v)O2 difference were also measured during maximal exercise (12.5 m/s gallop, 5% incline) to obtain an estimate of maximum O2 uptake (VO2max). The walk, trot, and canter represented 25, 45, and 55% VO2max. Mean heart rate went from 48.9 (...
Bertone JJ, Paull KS, Wingfield WE, Boon JA.M-mode echocardiographic structures, and cardiac function indices, PCV, and total plasma protein values were determined for 34 endurance equine athletes before (base line) and after (after race) a 161-km endurance competition and were compared. The PCV (base-line mean, 37%; after-race mean, 46%) and total plasma protein value (base-line mean, 6.9 g/dl; after-race mean, 7.5 g/dl) increased. Compared with base-line echocardiography, after-race echocardiography indicated an increase in heart rate, as determined from the simultaneous ECG recorded on the echocardiograph (base-line mean, 41 beats/mi...
Steffey EP, Hodgson DS, Dunlop CI, Miller MF, Woliner MJ, Heath RB, Grandy J.Hemodynamic and respiratory effects of 5 h of unvarying 1.57%, end-tidal (1.2 MAC) isoflurane in O2 anesthesia were characterized in ten left laterally recumbent horses. Compared to base line values at 30 min of constant dose isoflurane, cardiac output, hematocrit, total plasma solids, PaCO2, and peak inspired gas flow progressively and significantly (P less than 0.05) increased over the course of study. Arterial blood pressure increased (P less than 0.05) during the first 2 h of constant dose of isoflurane then decreased and remained near base line values. Inspiratory time progressively decre...
Karimi A.Two methods of anaesthesia were evaluated in the horse for their effects on the cardiovascular and respiratory systems and on the acid-base status of the animal. In addition the effect of the position—dorsal and lateral recumbency—of the anaesthetized horse on these systems was evaluated.
Rugh KS, Garner HE, Hatfield DG, Miramonti JR.The response of coronary collaterals in nine ponies subjected to repeated reversible occlusions (2 min duration, 30 min interval) of the left anterior descending coronary artery was studied at rest. Each pony was instrumented with a Doppler flowmeter and hydraulic cuff occluder around the left anterior descending coronary artery, left ventricular subendocardial sonomicrometers, and a left ventricular micromanometer. Initial occlusions increased end diastolic myocardial segment length by 3% and decreased segment systolic shortening, stroke work, and velocity of shortening by 103%, 95%, and 79% ...
Manohar M, Gustafson R, Goetz TE, Nganwa D.Effects of 1.1, 1.5, and 1.8 minimal alveolar concentration (MAC) isoflurane-O2 (1.45%, 1.96%, and 2.39% end-tidal isoflurane, respectively) anesthesia on cardiac output, blood pressure, and blood flow to the brain, thyroid glands, adrenal glands, kidneys, and splanchnic organs were examined in 9 healthy isocapnic adult ponies. Tissue blood flows were studied using 15-micron diameter radionuclide-labeled microspheres that were injected into the left ventricle, and comparisons were made with data obtained from ponies in the conscious state. Isoflurane anesthesia caused dose-related reduction in...
Bayly WM, Schultz DA, Hodgson DR, Gollnick PD.Experiments were undertaken to determine whether respiratory masks worn by horses exercising strenuously on a treadmill may interfere with normal gas exchange. Four collection systems, two flow-through systems and two incorporating one-way valve systems with subject-generated airflow were studied. Six horses performed standard treadmill exercise tests consisting of a 2-min warm up followed by galloping 1 min each at 8,9, and 10 m/s. Each horse exercised six times while wearing each of the four respiratory masks. Each flow-through system was used twice with flow rates of 2,360 and 3,840 l/min f...
Dunlop CI, Steffey EP, Miller MF, Woliner MJ.Cardiopulmonary function was monitored in 6 non-medicated, healthy male horses, anesthetized with halothane or isoflurane in O2 at a constant dose (1.2 times the minimum alveolar concentration). Horses were exposed once to each anesthetic agent, and a minimum of 2 weeks separated anesthetic exposures. All horses were studied in left lateral recumbency, and ventilation was mechanically controlled to induce a PaCO2 of 35 to 45 mm of Hg and an inspiratory peak airway pressure of 18 to 22 cm of H2O. After 1 hour of horse preparation, constant conditions were begun. With duration of anesthesia, car...
Robertson SA.Three different anaesthetic techniques were studied in normal, healthy Thoroughbred or Thoroughbred type horses. These were (a) acepromazine, thiopentone and suxamethonium; (b) acepromazine, glyceryl guaiacolate and a 'half-dose' of thiopentone; and (c) xylazine and ketamine. Anaesthesia was maintained with halothane vaporized in oxygen and nitrous oxide. All horses underwent either laryngeal or body surface surgery. Heart rate, packed cell volume, blood glucose and lactate, plasma non-esterified fatty acids, insulin and cortisol were measured before, during and after surgery. The greatest met...
Steffey EP, Kelly AB, Woliner MJ.Cardiovascular and respiratory functions were serially evaluated in ten healthy, fasting, spontaneously breathing, laterally recumbent adult horses during five hours of constant 1.06% alveolar halothane (equivalent to 1.2 times the minimum alveolar concentration for horses). Mean carotid arterial pressure was about 25% higher after one hour of constant-dose halothane than after 30 minutes of constant-dose (P less than 0.05), and remained increased throughout the study. Mean carotid arterial pressure peaked after 90 minutes, and was about 30% higher than at 30 minutes. Total peripheral vascular...
Youket RJ, Carnevale JM, Houpt KA, Houpt TR.The effect of meal frequency on body fluid, glucose, triiodothyronine (T3), heart rate and behavior was measured in 10 ponies. A simple reversal design was used in which each pony received one meal/day (1X) for 2 wk and six meals/day (6X) for 2 wk. The total intake/day was held constant. Feeding was followed by a rise in plasma levels of glucose, T3, protein and osmolality. One large meal was followed by significantly greater changes in all of the variables than was a meal one-sixth the size. Plasma T3 rose from 41 +/- 5 (SE) ng/liter before feeding to 43 +/- 5 ng/liter following a small meal,...
Couroucé A, Corde R, Valette JP, Cassiat G, Hodgson DR, Rose RJ.The purpose of this study was to determine the optimal treadmill slope for trotters to produce the same heart rate and blood lactate responses as on the track during a standardized exercise test. Nine 2-year-old French trotters performed exercise tests on a training track and on a treadmill set at an incline of 0, 2 or 4%. For all horses, track testing was performed on day 1 and then on the treadmill according to a Latin-square design. The track test utilized three steps each of 3 min at speeds of 470, 530, 590 m/min and the same speeds were used on the treadmill. Derived physiological variabl...
Testa M, Raffe MR, Robinson EP.Twenty-five percent, 50%, and 67% nitrous oxide was administered to 12 horses anesthetized with halothane and oxygen. Compared to halothane-oxygen alone, there was no significant difference in heart rate, systolic, diastolic, or mean blood pressure values, arterial pH, PaCO2, or plasma bicarbonate values when nitrous oxide was included. A significant linear reduction in PaO2 values could be correlated with N2O:O2 concentrations. The halothane level required to maintain surgical anesthesia was reduced when nitrous oxide was administered, but it was not affected by changing the nitrous oxide con...
La Rosa L, Twele L, Duchateau L, Gasthuys F, Kästner SB, Schauvliege S.To study the antinociceptive properties of epidural magnesium sulphate (MgSO) in standing horses Experimental, placebo-controlled, masked, cross-over A group of six healthy horses Through an epidural catheter, 1 mg kg MgSO (treatment Mg) diluted to a volume of 15 mL or the same volume of saline (treatment S) was administered over 15 minutes. Electrical, thermal and mechanical nociceptive thresholds were determined on the pelvic limb before and 20, 40, 60, 80, 100, 120, 140, 160 and 180 minutes after the start of the injection. Heart rate (HR) and respiratory frequency (f) were recorded every ...
Hoffmann KL, Wood AK, Griffiths KA, Evans DL, Gill RW, Kirby AC.The effects of feeding on blood flow to the equine foot are poorly understood. In a temperature-controlled room, duplex Doppler ultrasonographic observations were made pre- and postprandially of the lateral proper palmar digital artery of 5 horses, randomly assigned to twice and 4 times daily feeding in an unbalanced 2 period crossover design. Arterial diameter and blood velocity were measured over 4 h and additional observations made of heart rate, blood pressure, total plasma protein, packed cell volume, plasma glucose and insulin. There was no effect of the feeding regimen on any variable. ...
Art T, Lekeux P.Exercise-induced variations in their ventilatory mechanics were studied in 8 healthy ponies 4.2 +/- 1.4 years old and weighing 282 +/- 11 kg. Airflow (V), tidal volume (VT), esophageal pressure, mask pressure and electrocardiogram were simultaneously recorded before, during and after a treadmill (incline 8.3 degrees) exercise which consisted of 2 min walking (1.5 m.sec-1), 3 min slow trotting (3.0 m.sec-1) and 3 min fast trotting (3.5 m.sec-1). The results of three consecutive daily measurements were averaged for each pony. Heart rate, minute volume (Ve), respiratory frequency (f) and peak ins...
Dunlop CI, Hodgson DS, Chapman PL, Grandy JL, Waldron RD.The purpose of this study was to compare the thermodilution technique for estimation of cardiac output with the indocyanine green dye dilution technique at flows between 10 and 39 L/min in halothane-anesthetized horses. The estimation of area of dye dilution cardiac output curves was made by using the fore-'n-aft (FA) triangle method. This shorthand technique was compared with logarithmic exponential extrapolation and summation (extrapolated area), using 64 cardiac output curves. Then, 256 simultaneous thermodilution measurements were compared with dye dilution measurements calculated by use o...
Natalini CC, Alves SD, Guedes AG, Polydoro AS, Brondani JT, Bopp S.To evaluate the analgesic, physiologic, and behavioral effects of the epidural administration of tiletamine/zolazepam in horses. Methods: Prospective, double-blind, randomized experimental study. Methods: Five adult, healthy horses aged 10-16 years and weighing (mean +/- SD) 400 +/- 98 kg. Methods: The horses were sedated with 1.0 mg kg(-1) intravenous (IV) xylazine, and an epidural catheter was placed into the first intercoccygeal intervertebral space. After a 48-hour resting period, epidural tiletamine/zolazepam, 0.5 mg kg(-1) (treatment I) or 1.0 mg kg(-1) (treatment II), diluted up to 5 mL...
Olsen SC, Coyne CP, Lowe BS, Pelletier N, Raub EM, Erickson HH.Furosemide, which commonly is used as a prophylactic treatment for exercise-induced pulmonary hemorrhage in horses, may mediate hemodynamic changes during exercise by altering prostaglandin metabolism. To determine if furosemide's hemodynamic effects during exercise in horses could be reversed, cyclooxygenase inhibitors were administered with furosemide. Four treatments were administered 4 hours prior to treadmill exercise at 9 and 13 m/s. They included a control treatment (10 ml of 0.9% NaCl solution, IV), furosemide (1 mg/kg of body weight, IV) administered alone, and furosemide in combinati...
Gehlen H, Haubold A, Rohn K, Stadler P.In the present study we examined, if in Icelandic horses an increase in heart and/ or breathing rate is physiological and breed dependend or a sign of a pulmonary or cardiac disease. Therefore we examined 37 Icelandic horses with the prereport of being healthy. During clinical lung examination four horses showed symptoms of a pulmonary disease like increased breathing rate and enforced breathing at rest. These horses were excluded from the study. The other 33 horses were clinically normal. 17 of these horses were unridden (untrained) and 16 horses were regularly worked (trained). After clinica...
Gehlen H, Groner U, Rohn K, Stadler P.In the present study, a right heart catheterisation was carried out on three consecutive days in 17 healthy horses to evaluate the day-to-day variability of cardiac pressure values. Cardiac pressure values were measured in the right atrium, the right ventricle, the pulmonary artery, and the pulmonary capillaries (pulmonary artery wedge pressure). Additionally it was examined wether the cardiac pressure variability was influenced by the heart rate and if there are differences between trained and untrained horses. Beside the coefficient of variances, statistical analysis with assessment of varia...
Miller PJ, Holmes JR.Systolic time intervals (STIs), isovolumic contraction time (ICT) and left ventricular ejection time (LVET) were recorded from seven horses with supraventricular arrhythmia. The STIs were measured over a number of beats (33 to 100) directly from the left ventricular (LV) and aortic (Ao) pressure contours which were recorded simultaneously using two catheter-mounted transducers. ICT was significantly (P less than 0.01) and directly related to beat-by-beat heart rate (HR = 60/pulse interval) and LVET was significantly (P less than 0.01) and inversely related to heart rate in each of five horses....
Gasthuys F, De Moor A, Parmentier D.The influence of digoxin (0.01 mg/kg) given as an intravenous bolus followed by dopamine at different infusion rates (1.25, 2.5 and 5.0 micrograms/kg/min) on the cardiovascular depression during a standard halothane anaesthesia was studied in dorsally recumbent ventilated ponies. Preanaesthetic digitalization induced no clear positive cardiovascular effects over 30 minutes, except for non-significant increases in mean pulmonary artery pressure and total pulmonary resistance. These changes were probably time-related. No specific side-effects related to the fast intravenous digitalization were n...
Poulsen L, Henriksson FV, Dahl M, Honoré ML, Olsen SN, Leifsson PS, Staerk-Østergaard J, Jacobsen S, Pihl TH.Horses with non-strangulating intestinal infarction (NSII) are often misdiagnosed with idiopathic peritonitis or acute colitis. Early diagnosis is essential to ensure early surgical intervention and improve survival. Clinical and laboratory data from horses admitted to the University of Copenhagen Large Animal Teaching Hospital with NSII, idiopathic peritonitis or acute colitis between 2009 and 2018 were used for univariate comparisons and a multivariable logistic regression model for prediction of NSII. Two hundred and thirty-one horses were included. A multivariable model for the prediction ...
Reginato GM, Xavier NV, Alonso BB, Lima DP, Pereira Sirqueira TC, Carregaro AB.The study evaluated the effect of a 1/10 dose of flunixin meglumine administered into the governing vessel 1 (GV1) acupoint in horses that underwent castration. Twenty animals received 0.02 mg/kg detomidine intravenously, followed by 2.2 mg/kg ketamine and 0.1 mg/kg diazepam by the same route, and also a local anesthesia with 30 mL lidocaine. As postoperative analgesia, the animals received 1.1 mg/kg flunixin meglumine IV (FIV) or 0.11 mg/kg flunixin meglumine into the GV1 acupoint (FGV). Behavioral parameters were assessed 12 hours before the procedure (baseline) and at 4, 6, 12, and 2...
Bennet ED, Hayes ME, Friend L, Parkin TDH.Endurance competitions over distances of 80-160 km are required by Fédération Equestre Internationale (FEI) rules to be divided into a number of stages between three and six. These stages are also known as "loops". Veterinary inspections, designed to ensure horse welfare, are conducted at the end of each loop, with details recorded on a separate "vet card" for each horse. Objective: To identify risk factors recorded on vet cards that were associated with elimination at subsequent loops. Methods: Retrospective cohort study. Methods: Data relating to 3213 horse starts worldwide in internation...
Cooley JL, Hinchcliff KW, McKeever KH, Lamb DR, Muir WW.Effects of furosemide administration on exertion-induced changes in plasma renin activity and plasma concentrations of atrial natriuretic peptide and aldosterone in horses during sustained submaximal exertion were examined. Furosemide (1 mg/kg of body weight) or heparinized saline solution was administered IV to each of 6 mares not conditioned to exercise, either 4 hours or 2 minutes before 60 minutes of sustained submaximal running on a treadmill. Horses ran at a speed that induced heart rate approximately 65% of maximal after saline treatment. After 15 minutes of running, furosemide suppress...
Eades SC, Moore JN.Changes in lateral cecal arterial blood flow, mean internal carotid arterial pressure, and heart rate caused by nasogastric administration of fenoldopam (3, 6, and 9 mg/kg of body weight), a selective agonist of dopaminergic receptors, were recorded in 7 healthy horses. Cecal arterial blood flow was significantly increased within 30 minutes after administration of fenoldopam at all 3 dosages, with the peak increases from baseline (67.8 +/- 17.5 ml/min) being 125 +/- 28, 120 +/- 22, and 153 +/- 32 ml/min for 3, 6, and 9 mg/kg, respectively. Although carotid arterial pressure did not change sign...
Muir WW, Sams RA, Ashcraft S.The haemodynamic, respiratory and behavioural effects and pharmacokinetics of methocarbamol were studied in eight healthy, adult horses after intravenous (i.v.) and oral administration of large dosages. Heart rate, cardiac output, mean pulmonary arterial blood pressure, systolic, diastolic and mean aortic blood pressure, respiratory rate and arterial blood gases did not change after either i.v. (30 mg/kg bodyweight [bwt]) or oral (50 and 100 mg/kg bwt) dosages of methocarbamol. Mild to moderate depression was observed in five of eight horses administered i.v. methocarbamol, and in all horses a...
La Rosa L, Twele L, Duchateau L, Gasthuys F, Kästner SB, Schauvliege S.A bolus of 50 mg kg MgSO (treatment Mg) or the same volume of saline (treatment S) was infused over 15 minutes in 5 adult healthy horses. T0 was the end of the infusion. Physiological parameters were recorded throughout the study period. Measurements of electrical, thermal, and mechanical nociceptive thresholds were performed at the pelvic limbs at baseline (before T0), and at specific timepoints. Blood samples were taken at fixed timepoints before, during and until 12 hours after the infusion. For statistical analysis, the 95% confidence intervals (CI's) for the differences in nociceptive th...
Cenani A, Brosnan RJ, Madigan S, Knych HK, Madigan JE.Propranolol has been suggested for anxiolysis in horses, but its sedation efficacy and side effects, both when administered alone and in combination with α-adrenoceptor agonists, remain undetermined. This study aimed to document the pharmacokinetics and pharmacodynamics of propranolol, romifidine and their combination. Methods: Randomized, crossover study. Methods: Six adult horses weighing 561 ± 48 kg. Methods: Propranolol (1 mg kg; treatment P), romifidine (0.1 mg kg; treatment R) or their combination (treatment PR) were administered intravenously with a minimum of 1 week between treatment...
Grubb TL, Constable PD, Benson GJ, Foreman JH, Olson WO, Thurmon JC, Tranquilli WJ, Davis LE.To determine the most repeatable method for evaluating right ventricular relaxation rate in horses and to determine and compare effects of isoflurane or halothane with and without the added influence of intravenously administered calcium gluconate on right ventricular relaxation rates in horses. Methods: 6 Thoroughbred horses from 2 to 4 years old. Methods: 6 models (2 for monoexponential decay with zero asymptote, 3 for monoexponential decay with variable asymptote, and 1 for biexponential decay) for determining right ventricular relaxation rate were assessed in conscious and anesthetized hor...
Taylor PM.The study investigated whether hypotension in halothane-anaesthetised ponies is the stimulus inducing an endocrine stress response by assessing the effect of maintenance of normotension with a dobutamine infusion. Groups of six ponies were studied. After premedication with acepromazine (0.04 mg/kg) anaesthesia was induced with thiopentone (10 mg/kg) and maintained for 120 min with halothane (group AN). Dobutamine was infused to effect (1.1-4.4 microg/kg/min) to maintain arterial pressure at pre anaesthetic levels. The conscious group (CON) were prepared as for AN and then received only dobutam...
Pedersoli WM, Ravis WR, Belmonte AA, McCullers RM.Digoxin (elixir, 0.022 mg/kg) was administered via stomach tube to healthy horses of mixed breeding and sexes. Serum digoxin concentrations reached a peak (2.21 +/- 0.6 ng/ml) at approximately 1 hour after dosing and had a half-life of 28.8 +/- 10.7 hours. Digoxin kinetics followed a triexponential curve, indicating that at least a 2 compartmental model is required to characterize the serum concentration-time curve after this route of administration. It was calculated that to achieve average serum concentrations of 1.1 ng/ml, an oral dose of 17.4 microgram of digoxin elixir/kg/day and an IV do...
Ingvast-Larsson C, Kallings P, Persson S, Appelgren LE, Wiese B.The pharmacokinetics of theophylline at rest and the effects on cardio-respiratory and blood lactate responses to exercise were investigated after repeated oral administrations in six healthy Standardbred horses. A dose of 5 mg/kg body weight was administered every 12 h. The binding of theophylline to plasma protein was also determined. There was good agreement between predicted and observed plasma concentrations of theophylline at steady state. The mean half-life of elimination was shown to be 17.0 +/- 2.5 h, the mean half life of absorption was 1.6 +/- 1.8 h, the apparent volume of distribut...
Schauvliege S, Van den Eede A, Duchateau L, Gasthuys F.Enoximone is a phosphodiesterase III inhibitor frequently used to improve cardiac output (CO) in man. As the use of enoximone has not been reported in horses, the effects of this inodilator were examined in isoflurane anaesthetized ponies. Methods: Prospective, randomised, experimental study. Methods: Six healthy ponies, weighing 286 (212-367) +/- 52 kg, aged 5.0 +/- 1.6 years (4-6.5). Methods: After sedation with romifidine [80 microg kg(-1) intravenously (IV)], general anaesthesia was induced with midazolam (0.06 mg kg(-1) IV) and ketamine (2.2 mg kg(-1) IV) and maintained with isoflurane in...
Brand A, Lindner A, Gerhards H, Valenchon M, Petit O.The objective of this study was to explore how the endurance of five-year-old horses, kept out on pasture all their life and ridden for the first time well into their fifth year of age, developed within one year and compared to that of six-year-old horses raised under the same conditions and to other horses. Horses were submitted to a standardized exercise test (SET) to calculate their v (velocity run under defined conditions inducing 4 mmol/L of blood lactate concentration (LA)) and v (velocity run under defined conditions inducing a heart rate of 180 beats/min). The test consisted of up to ...
Nardelli M, Lanata A, Valenza G, Sgorbini M, Baragli P, Scilingo EP.This paper reports on a novel real time index designed to assess the quality of electrocardiographic (ECG) traces recorded in a group of five horses during a submaximal treadmill test procedure. During the experimental protocol two ECG monitoring systems were simultaneously applied to the animals. The first system was equipped with textile electrodes while the second one with standard red-dot electrodes. The procedure comprised four phases with an increased treadmill velocity, specifically, Walk 1, Trot 1, Trot 2 and Gallop. Three signal quality levels have been fixed according to the amount o...
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...
Muir WW, Sams RA, Ashcraft S.The hemodynamic, respiratory, and behavioral effects, as well as the pharmacokinetic properties of methocarbamol, were determined in horses. Heart rate, cardiac output, arterial and venous blood pressures, respiratory rate, and arterial blood gases did not change after IV methocarbamol (4.4, 8.8, 17.6 mg/kg) administration. There were no signs of behavior modification or ataxia observed. Analysis of plasma concentration time data indicated that the disposition of methocarbamol may be dose-dependent. Clearance and steady-state volume of distribution decreased as the dose increased. Plasma conce...
