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Topic:Blood Vessels
Blood vessels in horses are integral components of the circulatory system, responsible for the transportation of blood throughout the body. They consist of arteries, veins, and capillaries, each serving distinct functions in maintaining circulatory efficiency. Arteries carry oxygen-rich blood away from the heart to various tissues, while veins return deoxygenated blood back to the heart. Capillaries facilitate the exchange of nutrients, gases, and waste products between blood and tissues. The structure and function of equine blood vessels are subjects of study due to their role in health and disease, including conditions such as laminitis and equine metabolic syndrome. This page compiles peer-reviewed research studies and scholarly articles that explore the anatomy, physiology, and pathophysiology of blood vessels in horses.
Unusual internal carotid artery branching that prevented arterial occlusion with a balloon-tipped catheter in a horse. A mare with hemorrhage caused by guttural pouch mycosis was treated by insertion of a balloon-tipped catheter into the left internal carotid artery. During recovery from general anesthesia, the mare had profuse epistaxis, and was anesthetized again to determine the site of hemorrhage. The affected guttural pouch was opened to confirm that hemorrhage was from the left internal carotid artery. The mare was euthanatized, and, at necropsy, the balloon catheter was found in an aberrant branch that arose from the internal carotid artery and joined the basilar artery. The mycotic plaque was on the le...
[Pulsed Doppler echocardiography measurement in healthy warmblood horses]. Twenty adult warm blooded horses (body weight 585 +/- 59 kg) were evaluated with pulsed doppler echocardiography. Locations for the transducer and the sample volume were determined to get typical blood flow tracings of the equine heart. Angle of doppler beam was between 37 degrees and 40 degrees in right heart atrioventricular flow tract and between 44 degrees and 47 degrees in left heart atrioventricular flow tract. Peak blood flow velocity (angle corrected) was 0.71 +/- 0.17 m/s in tricuspid valve and 0.92 +/- 0.22 in mitral valve. In right and left atrioventricular flow tracts in all sample...
Ultrasonographically detected changes in equine superficial digital flexor tendons during the first months of race training. The forelimb superficial digital flexor (SDF) tendons of 6 Thoroughbreds were examined clinically and ultrasonographically during the first 4 months of race training. Sonograms were interpreted clinically and by use of computer-aided analysis. Tendon tissue from all horses was examined histologically at the end of the study. Computer-aided analysis of sonograms of the SDF tendons revealed trends toward an increase in mean cross-sectional area and a decrease in mean echogenicity over time with training. An inverse relation was found between increase in cross-sectional area and decrease in mean ...
Evaluation of the microcirculation of the equine small intestine after intraluminal distention and subsequent decompression. Effects of intraluminal distention (25 cm of H2O, 120 minutes) and subsequent decompression (60 minutes) on intramural vascular patterns of the small intestine was evaluated in 7 anesthetized horses. Intraluminal distention (25 cm of H2O, 120 minutes) was created in 2 jejunal segments in each horse. Experimental and control segments were removed either immediately after the experimental period or after 60 minutes of decompression. The vascular system of experimental and control jejunal segments was lavaged with NaCl, then was injected with a blue-colored radiopaque medium for microangiography ...
Evaluation of the microcirculation of the equine jejunum and ascending colon after ischemia and reperfusion. Intramural vascular patterns of the jejunum and colon were evaluated during ischemic strangulation obstruction (ISO, 70 minutes) and subsequent reperfusion (60 minutes) in 7 adult anesthetized horses. Microvasculature of experimental and control segments was described by comparison of results from microangiography, light microscopy, and scanning electron microscopy of vascular replicas. Experimental and control segments with isolated vascular arcades were removed either immediately after the experimental period or after 60 minutes of reperfusion. Blood was flushed from the vascular system by u...
Stress failure of pulmonary capillaries in racehorses with exercise-induced pulmonary hemorrhage. Bleeding into the lungs in thoroughbreds is extremely common; there is evidence that it occurs in essentially all horses in training. However, the mechanism is unknown. We tested the hypothesis that exercise-induced pulmonary hemorrhage (EIPH) is caused by stress failure of pulmonary capillaries. Three thoroughbreds with known EIPH were galloped on a treadmill, and after the horses were killed with intravenous barbiturate the lungs were removed, inflated, and fixed for electron microscopy. Ultrastructural studies showed evidence of stress failure of pulmonary capillaries, including disruptions...
Cardiovascular effects of thoracic compression in horses subjected to euthanasia. Six horses scheduled for euthanasia were instrumented for the measurement of blood flow by thermodilution, pulmonary arterial, right atrial and arterial blood pressures and collection of arterial blood for pH and blood gas analysis. The horses were anaesthetised with intravenous (iv) thiamylal sodium (10 mg/kg) and placed in right lateral recumbency. After euthanasia with an overdose of pentobarbitone sodium (100 mg/kg, iv) and loss of the electrocardiogram and arterial pulse pressure, thoracic compression at rates of 40, 60 and 80 compressions/min was instituted. Thoracic compression was acco...
Catecholaminergic innervation of the equine ureter. The aim of the present study was to determine the distribution and density of catecholaminergic nerve fibres and cells in the equine ureter by using immunohistochemical techniques to localise the enzyme tyrosine-hydroxylase (TH). TH-immunoreactive (TH-IR) nerve fibres entered the wall of the ureter as adventitial nerve trunks accompanying the blood vessels. These trunks repeatedly branched as they coursed through the muscular layer towards the epithelium, forming muscular, perivascular and subepithelial nerve plexuses. TH-IR nerve fibres were especially numerous in the pelvic and intravesical ...
Hemorrhage into the guttural pouch (auditory tube diverticulum) associated with rupture of the longus capitis muscle in three horses. Three horses were determined to have hemorrhage into a guttural pouch unassociated with mycosis, empyema, neoplasia, or foreign body. The source of the hemorrhage appeared to be the rupture of the longus capitis muscle and its associated vascular supply.
Dissipation of metabolic heat in the horse during exercise. Horses were exercised at 40, 65, and 90% of their maximum O2 uptake (VO2max) until moderately fatigued (approximately 38, 15, and 9 min, respectively) to assess heat loss through different routes. Approximately 4,232, 3,195, and 2,333 kcal of heat were generated in response to exercise at these intensities. Of this, approximately 7, 16, and 20% remained as stored heat 30 min postexercise. Respiratory heat loss, estimated from the temperature difference between blood in the pulmonary and carotid arteries and the cardiac output, was estimated to be 30, 19, and 23% of the heat produced during exe...
[Charcot and claudicatio intermittens – a footnote to the history of vascular surgery]. Jean Martin Charcot was the first to give a detailed description of intermittent claudication, and a correct interpretation of the mechanism behind the symptoms. He borrowed the name of the syndrome from the veterinarian literature, where it had been described to occur in horses, and caused by inflammatory changes in aorta at the origin of the large vessels to the extremities. The case presented by Charcot was a man with a traumatic pseudoaneurysm in his common iliac artery. He had in addition an arterio-enteric fistula, a condition which probably had not been described before.
Pulmonary artery wedge pressure increases with high-intensity exercise in horses. Using catheter mounted microtip manometers, right atrial, pulmonary artery, and pulmonary artery wedge pressures were studied in 8 horses while they were standing quietly (rest), and during galloping at treadmill speeds of 8, 10, and 13 m/s. At rest, mean (+/- SEM) heart rate, mean right atrial pressure, mean pulmonary artery pressure, and mean pulmonary artery wedge pressure were 37 (+/- 2) beats/min, 8 (+/- 2) mm of Hg, 31 (+/- 2) mm of Hg, and 18 (+/- 2) mm of Hg, respectively. Exercise at treadmill belt speed of 8 m/s resulted in significant (P < 0.05) increments in heart rate, right at...
Antagonism of a specific dopaminergic receptor agonist with metoclopramide in horses. 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...
Nutrient utilisation by the hindlimb of thoroughbred horses at rest. Nutrient uptake by the hindlimb was investigated utilising the arteriovenous difference technique in 5 Thoroughbred horses fed to maintenance a diet of 100% roughage or 52% oat grain and 48% roughage. Arterial blood was obtained from a catheter inserted into the carotid artery while venous blood was simultaneously collected from a catheter placed into the iliac vein via the medial saphenous vein. The arteriovenous difference for glucose was significant and represented a mean extraction of 10 +/- 1% with no effect of diet. If fully oxidised, glucose uptake (corrected for lactate and pyruvate ar...
Specialized veins in the submucosa of the equine ileocecal junction. Spirally arranged bundles of sub-endothelial smooth muscle enfold the small to medium-sized submucosal veins in the equine ileocecal junction. The muscle bundles, accompanied by the endothelial lining, bulge into the lumen of the vessels, partly occluding the latter. Transmission electron microscopy of the muscle cells reveals features consistent with vascular smooth muscle ultrastructure. It is proposed that the throttling effect of the muscle bundles causes engorgement of the submucosal venous plexus, which then assists in the closing of the ileocecal orifice.
Effects of furosemide and pentoxifylline on blood flow properties in horses. The effects of furosemide and pentoxifylline on blood flow properties in horses were investigated. Hematologic and rheologic changes were examined in 4 horses before and 3 minutes after administration of epinephrine (1 mg, IV). The next day, hemorheologic changes were determined before and 3 hours after administration of furosemide (1 mg/kg of body weight, IM), and after administration of epinephrine at the sampling at 3 hours. Hematologic and rheologic changes were evaluated weekly in 3 horses given pentoxifylline (8.5 mg/kg, q 12 h, PO) for 28 days. In addition, hemorheologic responses to ep...
Measurement of muscle surface capillary blood flow by laser Doppler flowmetry. Muscle surface capillary blood flow was measured in the biceps femoris and lateral head of the triceps brachii muscles in six horses before and during halothane anesthesia by using laser Doppler flowmetry. During 90 minutes of anesthesia, muscle surface capillary blood flow was reduced to 20% to 40% of preanesthetic values. Muscle surface capillary blood flow tended to be lower in dependent muscles than in nondependent muscles, and this disparity was greater in the forelimbs than in the hind limbs.
Microvascular permeability changes in ischemia/reperfusion injury in the ascending colon of horses. The normal microvascular permeability of the ascending colon in horses and the microvascular permeability of that segment after ischemia and reperfusion were investigated. Microvascular permeability was estimated by the ratio of lymphatic protein to plasma protein concentration (Cl/Cp) at high lymph flow rates in 8 adult horses in 2 equal groups: normal and ischemic (2-hour period). Lymphatic flow rates and lymph and plasma protein concentrations were determined. Intestinal biopsy specimens were obtained at the end of each experiment. Flow independent values were selected and compared by one-w...
Distribution of coronary collateral blood flow at different levels of collateral growth in conscious ponies. Coronary collateral growth was stimulated in chronically instrumented conscious ponies by a previously validated intermittent coronary occlusion method. Changes in regional myocardial function (sonomicrometry) and reactive hyperemia (Doppler method) were used to monitor collateral growth and to program measurements of regional myocardial blood flow (microsphere method). A serial analysis of the transmural and lateral distributions of collateral blood flow was performed at the native and three superimposed levels of collateral growth. Results in nine animals undergoing an average of 553 +/- 188...
Effect of hypertonic and isotonic saline solutions on plasma constituents of conscious horses. Blood constituents and vascular volume indices were determined in 5 standing horses by use of 2-period crossover experimental design. Horses were either administered hypertonic (2,400 mosm/kg of body weight, i.v.) or isotonic (300 mosm/kg, i.v.) saline solution. Each solution was administered at a dosage of 5 ml/kg (infusion rate, 80 ml/min). Samples for determination of PCV, plasma volume, blood volume, plasma osmolality, total amount of plasma protein and plasma concentrations of protein, Na, K, and Cl were collected at 0 hour (baseline, before fluid infusion) and 0.5 hour (at the end of flu...
Regional brain blood flow during prolonged submaximal exercise in ponies. Experiments were carried out on 8 healthy ponies to examine the effects of prolonged submaximal exercise on regional distribution of brain blood flow. Brain blood flow was ascertained by use of 15-microns-diameter radionuclide-labeled microspheres injected into the left ventricle. The reference blood was withdrawn from the thoracic aorta at a constant rate of 21.0 ml/min. Hemodynamic data were obtained with the ponies at rest (control), and at 5, 15, and 26 minutes of exercise performed at a speed setting of 13 mph on a treadmill with a fixed incline of 7%. Exercise lasted for 30 minutes and w...
Acetylsalicylic acid and blood coagulation in the horse. Equine blood may contain salicylic acid (SA) taken up as free acid or represents the metabolite of acetylsalicylic acid (ASA). To obtain information of SA in race horses we screened blood samples of trotting-horses routinely drawn to be analyzed for doping substances. The individual values determined followed a Gaussian distribution displaying a geometric mean of 19 ng SA per ml serum. A probit analysis revealed linear relationship (r = 0.995). Additional studies examined the antithrombotic efficacy of ASA in the horse. An oral dose of 300 mg ASA considerably elevated the bleeding time for mor...
Arteriovenous differences for glutamine in the equine gastrointestinal tract. Glutamine has been shown to be an important metabolic substrate of enterocytes in many animals, including cats, dogs, hamsters, human beings, monkeys, rabbits, rats, and sheep. To determine whether glutamine is important in the metabolism of cells of the equine gastrointestinal tract, we examined transintestinal differences in glutamine concentrations in the arterial and venous circulation, and measured activity of the major glutamine catabolizing enzyme, glutaminase. Arteriovenous differences provide an index of the amount of a given substrate removed by the tissue across which the measuremen...
Use of an ecraseur for ovariohysterectomy in mares. Ovariohysterectomy was performed in 20 mares at three stages of estrus. An ecraseur was used to severe the ovarian branch of the ovarian artery and vein and the ovarian suspensory ligament en masse. All other vessels supplying the ovaries and uterus were doubly ligated and transected. All mares survived. Complications were intraoperative hemorrhage in three mares, postoperative vaginal bleeding in two mares, and a hematoma in the remnant of the broad ligament in one mare. No adhesions between the uterine stump or remnants of the broad ligament and abdominal structures were detected by palpatio...
Intravenous catheterisation of foetus and mare in late pregnancy: management and respiratory, circulatory and metabolic effects. The uterine and umbilical vessels of 12 pregnant ponies were catheterised to study foetal metabolism. The effects of this procedure on maternal and foetal cardiovascular, respiratory, metabolic and adrenocortical activity were monitored during and after surgery. Premedication with acepromazine-butorphanol-detomidine was followed by induction of anaesthesia with detomidine and ketamine and maintenance, using mechanical ventilation, with halothane in oxygen and nitrous oxide. Mean maternal arterial blood pressure was greater than 70 mmHg during anaesthesia and arterial oxygen tension remained ov...
