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Topic:Arteries
Arteries in horses are blood vessels responsible for carrying oxygenated blood away from the heart to various tissues and organs throughout the body. These vessels are integral to the circulatory system, facilitating the delivery of essential nutrients and oxygen to maintain cellular function and overall health. The structure of equine arteries includes a thick muscular wall that accommodates the high pressure of blood flow, allowing for efficient transport. Research on equine arteries often focuses on their anatomical characteristics, physiological functions, and potential disorders that may affect them, such as atherosclerosis or aneurysms. This page compiles peer-reviewed research studies and scholarly articles that examine the anatomy, physiology, and pathophysiology of arteries in horses.
An evaluation of pulse oximeters in dogs, cats and horses. Evaluation of five pulse oximeters in dogs, cats and horses with sensors placed at five sites and hemoglobin saturation at three plateaus. Methods: Prospective randomized multispecies experimental trial. Methods: Five healthy dogs, cats and horses. Methods: Animals were anesthetized and instrumented with ECG leads and arterial catheters. Five pulse oximeters (Nellcor Puritan Bennett-395, NPB-190, NPB-290, NPB-40 and Surgi-Vet V3304) with sensors at five sites were studied in a 5 x 5 Latin square design. Ten readings (SpO2) were taken at each of three hemoglobin saturation plateaus (98, 85 and ...
The cardiopulmonary effects of severe blood loss in anesthetized horses. To characterize the acute cardiopulmonary effects of severe hemorrhage in anesthetized horses. Methods: Prospective experimental study. Methods: Three geldings and six mares, aged 14.4 +/- 2.7 years, weighing 486 +/- 41 kg (range: 425-550 kg). Methods: Horses were anesthetized using xylazine, guaifenesin, ketamine and halothane or isoflurane. Cardiovascular variables, hematocrit, total solids, capillary refill time (CRT) and color of mucous membranes were measured as blood was collected from the carotid artery into sterile plastic bags. Arterial blood gas analysis was also performed. Results: ...
Echo-Doppler findings of a carotid-jugular fistula in a foal. A seven-month-old male Standardbred was referred with a 4-month history of left jugular groove distension. On physical examination severely dilated left maxillary, linguofacial and jugular veins were appreciable. Blood gas analysis results indicated higher degree of oxygenation in the left jugular vein. Bi-directional flow signals, with normal systolic and early diastolic flow, and late diastolic retrograde flow, were noted on pulsed-wave Doppler interrogation and color flow mapping of the left jugular blood flow. A systolic-diastolic signal with spectral broadening was detected when positioni...
[The occurrence of hemodynamic effective elements in the intestinal blood vessel system]. Arterioles, precapillary sphincters, capillary endothelium, and pericytes probably regulate the blood flow in the intestinal microvascular bed similar to other regions of the body because of their equipment with contractile filaments. Only throttle veins with their arrangement of pools and their characteristics probably exert influence on the hemodynamic qualities of the blood flow in the intestinal mucosa.
Spasmogenic action of endothelin-1 on isolated equine pulmonary artery and bronchus. There is currently little published information about the effects of endothelin-1 (ET-1), a potent endogenous spasmogen of vascular and airway smooth muscle, on pulmonary vasculature and airways or which ET receptor subtypes mediate ET-1-induced vasoconstrictive and bronchoconstrictive action in the horse. Objective: To investigate the effect of endothelin-1 (ET-1) on smooth muscle from isolated equine pulmonary artery and bronchus. In addition, the roles of ETA and ETB receptors in ET-1 mediated contraction in these tissues were assessed. Methods: The force generation of ring segments from pu...
Arterial hypoxemia in exercising thoroughbreds is not affected by pre-exercise nedocromil sodium inhalation. It has been reported that pulmonary injury (i.e. capillary stress failure) evoked histamine release from airway inflammatory/mast cells contributes to exercise-induced arterial hypoxemia (EIAH) and that pre-exercise inhalation of nedocromil sodium mitigated EIAH in human subjects 'Med. Sci. Sports Exercise 29, (1997) 10-16'. Because exercise-induced pulmonary hemorrhage due to capillary stress failure is routinely observed in racehorses, we examined whether nedocromil inhalation would similarly benefit EIAH and desaturation of hemoglobin in horses. Two sets of experiments, namely, placebo stud...
Dynamic upper airway changes and arterial blood gas parameters during treadmill exercise. The primary goal was to investigate the relationship between dynamic upper airway abnormalities and arterial blood gas tensions during exercise. Horses that completed a high-speed treadmill examination consisting of upper-airway videoendoscopy, blood gas evaluation and electrocardiogams and, postexercise, echocardiograms and tracheal washes, were included. An age-matched group of fit, healthy Thoroughbreds, trained to run on a high-speed treadmill, served as controls for blood gas values at specific exercise speeds. One hundred and nineteen horses completed the treadmill examination. Sixty (50...
Different contractile effects of alpha1- and alpha2-adrenergic agonists on horse isolated common digital artery smooth muscle ring preparations in vitro. Despite assays on ring preparations in vitro confirmed that the vasoconstrictor sympathetic control in the horse common digital artery mainly depends on alpha(1)-adrenoceptors stimulation, selective alpha(2)-adrenoceptor agonists were investigated under the same experimental conditions. Both detomidine (DET) and UK 14304 differed from noradrenaline (NA) and phenylephrine (PHE) in provoking contractile effects which were slowly onsetting, concentrations-unrelated and unremovable by repeated washings. While prazosin (PRA) clearly antagonized the effects of NA and PHE, neither pre- nor post-treat...
Equine endotoxemia: pathomorphological aspects of endotoxin-induced damage in equine mesenteric arteries. To evaluate the effects of endotoxin on the morphology of the equine mesenteric vasculature, each of two thoroughbred horses were given two intravenous injections (24 h apart) of a sublethal dose of endotoxin (10 microg/kg). Each injection produced results similar to those of clinical cases of equine colic with obstructive nature of the loop of bowel: diarrhoea within 2 h after administration, followed by cessation of both faecal excretion and sounds of intestinal peristalsis. The most prominent morphological change was the development of moniliform appearance of small mesenteric arteries, in ...
H1-receptor antagonist, tripelennamine, does not affect arterial hypoxemia in exercising Thoroughbreds. It has been suggested that pulmonary injury and inflammation-induced histamine release from airway mast cells may contribute to exercise-induced arterial hypoxemia (EIAH). Because stress failure of pulmonary capillaries and EIAH are routinely observed in exercising horses, we examined whether preexercise administration of an H1-receptor antagonist may mitigate EIAH. Two sets of experiments, placebo (saline) and antihistaminic (tripelennamine HCl at 1.10 mg/kg iv, 15 min preexercise) studies, were carried out on seven healthy, exercise-trained Thoroughbred horses in random order 7 days apart. A...
In vitro responses of equine colonic arterial and venous rings to adenosine triphosphate. To evaluate the in vitro effects of adenosine tryphosphate (ATP) on vasomotor tone of equine colonic vasculature. Methods: Arteries and veins from the left ventral colon of 14 mixed-breed horses euthanatized for reasons unrelated to cardiovascular or gastrointestinal tract disease. Methods: Endothelium-intact and -denuded arterial and venous rings were precontracted with 10(-7) and 1.8 x 10(-8) M endothelin-1, respectively. In 1 trial, endothelium-intact rings were also incubated with 10(-4) M N omega-nitro-L-arginine methyl ester (L-NAME) to inhibit nitric oxide (NO) production. Adenosine tri...
Doppler sonographic measurements of arterial blood flow and their repeatability in the equine foot during weight bearing and non-weight bearing. In six normal adult horses, pulsed-wave Doppler sonographic inspections were made of the left and right lateral palmar proper digital artery (LPPDA) of each thoracic limb. Using a two-period, crossover design with repeated measures, each LPPDA was inspected on four occasions throughout the day over a 7 hour period and, on each occasion, with the limb weight bearing and non-weight bearing. In comparison with the observations made during weight bearing, there were significant increases (P<0.001) in blood-flow velocities when the limb was non-weight bearing. There was no relationship between b...
Nitric oxide synthase inhibition does not affect the exercise-induced arterial hypoxemia in Thoroughbred horses. Because sensitivity of equine pulmonary vasculature to endogenous as well as exogenous nitric oxide (NO) has been demonstrated, we examined whether endogenous NO production plays a role in exercise-induced arterial hypoxemia. We hypothesized that inhibition of NO synthase may alter the distribution of ventilation-perfusion mismatching, which may affect the exercise-induced arterial hypoxemia. Arterial blood-gas variables were examined in seven healthy, sound Thoroughbred horses at rest and during incremental exercise protocol leading to galloping at maximal heart rate without (control; placebo...
Alterations in systemic and local colonic hemodynamic variables associated with intravenous infusion of ATP-MgCl2 in healthy anesthetized horses. To characterize alterations in systemic and local colonic hemodynamic variables associated with IV infusion of ATP-MgCl2 in healthy anesthetized horses. Methods: 12 adult horses. Methods: Six horses were given ATP-MgCl2, IV, beginning at a rate of 0.1 mg of ATP/kg of body weight/min with incremental increases until a rate of 1.0 mg/kg/min was achieved. The remaining 6 horses were given an equivalent volume of saline (0.9% NaCl) solution over the same time period. Colonic and systemic hemodynamic variables and colonic plasma nitric oxide (NO) concentrations were determined before, during, and a...
Endothelin in the equine hypoxic pulmonary vasoconstrictive response to acute hypoxia. Elevated concentrations of endothelin (ET), a potent endothelium-derived vasoactive peptide, have been reported in a number of pathophysiological conditions associated with pulmonary hypertension, both in the horse and other species. We have previously shown, both in vitro and in vivo, that the pulmonary and systemic vascular response to exogenous ET is mediated predominantly via ET(A) receptors. Our hypothesis in the present study was that ET is involved in the equine hypoxic pulmonary vasoconstrictive response to acute hypoxia. In this study, we investigated the effects of a selective ET(A) ...
Equine pulmonary and systemic haemodynamic responses to endothelin-1 and a selective ET(A) receptor antagonist. Based on previous in vitro studies, we hypothesised that endothelin (ET) would induce vasoconstriction in the pulmonary circululation of the horse and that this action would be mediated via ET(A) receptors. Pulmonary and systemic haemodynamic responses to endothelin-1 (ET-1), a potent vasoactive endogenous peptide, were investigated in 6 conscious, nonsedated horses at rest. Bolus i.v. injections of exogenous ET-1 (0.1, 0.2 and 0.4 microg/kg bwt) caused significant increases in pulmonary (PAP) and carotid (CAP) artery pressures, with peak increases of 79% and 51% for mean PAP and CAP, respecti...
Effect of prior high-intensity exercise on exercise-induced arterial hypoxemia in Thoroughbred horses. Strenuously exercising horses exhibit arterial hypoxemia and exercise-induced pulmonary hemorrhage (EIPH), the latter resulting from stress failure of pulmonary capillaries. The present study was carried out to examine whether the structural changes in the blood-gas barrier caused by a prior bout of high-intensity short-term exercise capable of inducing EIPH would affect the arterial hypoxemia induced during a successive bout of exercise performed at the same workload. Two sets of experiments, double- and single-exercise-bout experiments, were carried out on seven healthy, sound Thoroughbred h...
Postprandial arterial vasodilation in the equine distal thoracic limb. 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. ...
In vitro pharmacologic effect of two endothelin-1 antagonists on equine colonic arteries and veins. To evaluate the effectiveness of 2 potential endothelin (ET)-1 antagonists in blocking the contractile responses of equine colonic vessels to increasing concentrations of ET-1. Methods: Mesenteric vessels from 6 clinically healthy horses. Methods: Colonic vessels (arterial and venous rings) were placed in organ baths with oxygenated Tyrode solution at 37 C. Each was attached to a force transducer interfaced with a polygraph, and 2 g of tension was applied and equilibrated for 45 minutes. Then, B-1 (PD 142893) and B-2 (PD 145065) ET-1 antagonists were tested. One ring from each vessel type was ...
Characterization of cultured smooth muscle cells obtained from the palmar digital arteries of horses. To develop methods to isolate, culture, and characterize smooth muscle cells (SMC) from equine palmar digital arteries. Methods: Segments of the medial or lateral palmar digital arteries from the forelimbs of 6 horses. Methods: To obtain smooth muscle explants, arterial segments were incised longitudinally. The tunica intima was gently scraped from the underlying tunica media, and explants were obtained from the tunica media. Approximately 18 to 24 explants were obtained from each palmar digital arterial segment. A substrate-attached technique was used to initiate primary culture of SMCCulture...
Intravenous pentoxifylline does not affect the exercise-induced pulmonary arterial, capillary or venous hypertension in Thoroughbred horses. The present study was carried out to examine whether intravenously administered pentoxifylline-a phosphodiesterase inhibitor which increases red blood cell deformability and decreases blood viscosity-would attenuate the magnitude of exercise-induced pulmonary capillary hypertension in healthy, fit Thoroughbred horses and in turn, diminish the occurrence of exercise-induced pulmonary hemorrhage (EIPH). Experiments were carried out on six healthy, sound, exercise-trained Thoroughbred horses. Hemodynamic data were collected at rest, and during exercise performed at 8 and 14 m/sec on 3.5% uphill g...
Clenbuterol administration does not attenuate the exercise-induced pulmonary arterial, capillary or venous hypertension in strenuously exercising Thoroughbred horses. The present study was carried out to ascertain whether beta2-adrenergic receptor stimulation with clenbuterol would attenuate the pulmonary arterial, capillary and venous hypertension in horses performing high-intensity exercise and, in turn, modify the occurrence of exercise-induced pulmonary haemorrhage (EIPH). Experiments were carried out on 6 healthy, sound, exercise-trained Thoroughbred horses. All horses were studied in the control (no medications) and the clenbuterol (0.8 pg/kg bwt, i.v.) treatments. The sequence of these treatments was randomised for every horse, and 7 days were allowe...
Transarterial coil embolization of the internal and external carotid and maxillary arteries for prevention of hemorrhage from guttural pouch mycosis in horses. To develop a transarterial coil embolization technique for occlusion of the internal carotid artery (ICA), external carotid artery (ECA), and maxillary arteries (MA) in normal horses and to evaluate this technique for prevention of hemorrhage in horses affected with guttural pouch mycosis. Methods: Ten adult, normal horses and 4 horses with guttural pouch mycosis. Methods: All horses had transarterial coil embolization of the rostral and caudal ICA, caudal MA, and rostral ECA. In 1 affected horse, an aberrant actively bleeding branch of the ECA was also occluded. Normal horses had a premortem ...
Evidence of histamine receptor function in isolated horse penile dorsal arteries. The effect of histamine (10(-9)-10(-3) M) on horse penile dorsal artery was evaluated. Precontracted vessels showed a biphasic response (relaxation-contraction) to histamine, while at basal tone, histamine only induced a contractile effect. The H1 receptor agonist, 2-pyridylethylamine (PEA) (10(-9)-10(-3) M), induced concentration-dependent relaxation in precontracted rings and provoked vasoconstriction at basal tone. Mepyramine (10(-9)-10(8) M), an H1 receptor antagonist, competitively antagonized the relaxant response to histamine (pA2 = 9.7) and PEA (pA2 = 9.2). At basal tone, mepyramine (1...
Repeatability of Doppler ultrasound measurements of hindlimb blood flow in halothane anaesthetised horses. The purpose of this study was to determine the repeatability of femoral blood flow recorded using Doppler ultrasound in anaesthetised horses. Doppler ultrasound of the femoral artery and vein was performed in 6 horses anaesthetised with halothane and positioned in left lateral recumbency. Velocity spectra, recorded using low pulse repetition frequency, were used to calculate time-averaged mean velocity (TAV), velocity of component a (TaVa), velocity of component b (TaVb), volumetric flow, early diastolic deceleration slope (EDDS) and pulsatility index (PI). Within-patient variability was deter...
Laparoscopic intra-abdominal ligation of the testicular artery following castration in a horse. A 364-kg (800-lb) 1-year-old mixed-breed horse was admitted for treatment of uncontrolled bleeding after castration. Multiple attempts to ligate the testicular artery through the scrotal incisions prior to referral had been unsuccessful. Because of the owner's concerns about cost, an attempt was made to control the bleeding by applying pressure to the inguinal region and administering formalin IV. However, hemorrhage continued. A decision was made to use laparoscopy to ligate the testicular artery. The horse was anesthetized and positioned in dorsal recumbency, and a routine ventral laparoscop...
Affinity of isoxsuprine for adrenoreceptors in equine digital artery and implications for vasodilatory action. We used isolated equine digital arteries to study the vasodilatory mechanism of isoxsuprine, and fowl caecum preparations to investigate the affinity of the drug for beta-adrenoceptors. Isoxsuprine is a potent vasodilator of arterial smooth muscle that has been precontracted by an alpha-adrenoceptor agonist such as noradrenaline (log EC50 = -6.33 [-5.98; -6.68]). The present study indicates that its effect is due to alpha-adrenoceptor blockade since: (1) after a long lasting exposure to cumulative doses of isoxsuprine the vasoconstricting action of noradrenaline cannot be restored; (2) isoxsup...
The effect of changing the mode of ventilation on the arterial-to-end-tidal CO2 difference and physiological dead space in laterally and dorsally recumbent horses during halothane anesthesia. To evaluate the effect of changing the mode of ventilation from spontaneous to controlled on the arterial-to-end-tidal CO2 difference [P(a-ET)CO2] and physiological dead space (VD(phys)/VT) in laterally and dorsally recumbent halothane-anesthetized horses. STUDY DESIGN; Prospective, experimental, nonrandomized trial. Methods: Seven mixed breed adult horses (1 male and 6 female) weighing 320 +/- 11 kg. Methods: Horses were anesthetized in 2 positions-right lateral and dorsal recumbency-with a minimum interval of 1 month. Anesthesia was maintained with halothane in oxygen for 180 minutes. Sponta...
Detachable latex balloon occlusion of an internal carotid artery with an aberrant branch in a horse with guttural pouch (auditory tube diverticulum) mycosis. An aberrant branch of the internal carotid artery was detected by angiography in a horse with guttural pouch (auditory tube diverticulum) mycosis after the distal portion of the artery had been occluded by use of a detachable latex balloon. A second balloon was placed to eliminate retrograde hemorrhage from the aberrant branch. The horse recovered and returned to its previous activity. Vascular anomalies of the internal carotid artery my be more common than expected, and have resulted in fatal complications during and after surgical treatment in guttural pouch mycosis. Intraoperative identific...
