Blood flow in horses refers to the movement of blood through the cardiovascular system, which includes the heart, arteries, veins, and capillaries. This process is essential for delivering oxygen and nutrients to tissues and organs, as well as for removing waste products from the body. Blood flow dynamics in horses are influenced by various factors, including heart rate, blood volume, and vascular resistance. The study of equine blood flow encompasses areas such as circulatory physiology, vascular health, and the impact of exercise on cardiovascular function. This page compiles peer-reviewed research studies and scholarly articles that explore the mechanisms, regulation, and implications of blood flow in equine health and performance.
Stadler P, Weinberger T, Deegen E.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...
Eades SC, Moore JN.Stimulation of alpha 2 adrenergic receptors inhibits colonic motility and may constrict some peripheral vascular beds. Endotoxemia elicits release of sympathetic neurotransmitters and increases sympathetic nerve activity, which may result in stimulation of alpha 2 adrenergic receptors. The objective of this study was to determine whether blockade of alpha 2 adrenergic receptors would restore cecal motility and blood flow during endotoxemia in horses. Strain-gauge force transducers and ultrasonic flow probes were used to measure cecal and colonic mechanical activity and lateral cecal arterial b...
Armstrong RB, Essén-Gustavsson B, Hoppeler H, Jones JH, Kayar SR, Laughlin MH, Lindholm A, Longworth KE, Taylor CR, Weibel ER.The purpose of this study was to describe the relationships between 16 physiological, biochemical, and morphological variables presumed to relate to the oxidative capacity in quadriceps muscles or muscle parts in Standardbred horses. The variables included O2 delivery (blood flow) and mean capillary transit time (MTT) during treadmill locomotion at whole animal maximal O2 consumption (VO2max, 134 +/- 2 ml.min-1 x kg-1), capillary density and capillary-to-fiber ratio, myoglobin concentration, oxidative enzyme activities, glycolytic enzyme activities, fiber type populations, and fiber size. Thes...
Boatwright RB, Williams DO, Rugh KS, Sarazan RD, Ross CR, Garner HE, Griggs DM.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...
Traub-Dargatz JL, Schultheiss PC, Kiper ML, Stashak TS, Wrigley R, Schlipf J, Applehans FM.Fibrosis of the small intestine led to recurrent colic and weight loss in 2 ponies and 5 horses. There was a reduction in the length of the small intestine to one-half normal in horses 4 to 7. Histologic examination revealed substantial small intestinal submucosal fibrosis and arteriole sclerosis. The cause was not determined, but an environmental factor was suspected because 3 horses were from the same farm and the other animals were from within a 10-mile radius of the farm. The submucosal fibrosis appeared to be secondary to sclerosis of arterioles in the submucosa and mesentery, with low bl...
Porter JK, Thompson FN.Fescue toxicosis in livestock is due to ingestion of endophyte (Acremonium coenophialum) -infected tall fescue. Understanding mechanisms responsible for decreased calving and growth rates, delayed onset of puberty, and impaired function of corpora lutea in heifers at puberty consuming endophyte-infected fescue is an emerging field in reproductive toxicology. The condition decreases overall productivity through a reduction in reproductive efficiency, reduced weight gains, and lowered milk production. Reproduction in cattle may be further compromised by winter coat retention, increased susceptib...
Deumer J, de Haan F, Tulp MT, van den Hoven R.The effects of an oral isoxsuprine-resin preparation on the blood flow in the thoracic limb of seven horses was determined by thermography. Treatment with the oral resin preparation resulted in increased skin temperatures compared with the non-medicated controls. The maximal temperature differences, 2.2 degrees C for the horses treated with 0.9 mg/kg and 1.8 degrees C for the horses treated with 1.2 mg/kg, occurred four hours after dosing. Plasma total isoxsuprine, determined in three horses, was detectable two hours after oral dosing and maximal eight hours after dosing, but free isoxsuprine ...
Held JP, Daniel GB.The effect of flunixin meglumine on renal function was studied in 6 healthy horses by use of nonimaging nuclear medicine techniques. Effective renal plasma flow (ERPF) and effective renal blood flow (ERBF) were determined by plasma clearance of 131I-orthoiodohippuric acid before and after administration of flunixin meglumine. Mean ERPF and ERBF was 6.03 ml/min/kg and 10.7 ml/min/kg, respectively, before treatment and was 5.7 ml/min/kg and 9.7 ml/min/kg, respectively, after treatment. Although ERPF and ERBF decreased after flunixin meglumine administration, the difference was not statistically ...
Sarazan RD, Krause GF, Franklin D, Garner HE, Griggs DM.Coronary reactive hyperemia duration (RHD) and coronary blood flow debt repayment (BFDR) were compared in conscious dogs and ponies instrumented with coronary artery Doppler flow probes and pneumatic occluders. Additional ponies were instrumented with pacing electrodes. With the use of a Latin square design, eight animals of each species were subjected to a randomized series of nine coronary occlusions ranging from 5 s to 2 min in duration. In both species, postocclusion blood flow velocity rose rapidly and plateaued at similar peak levels relative to control, but in ponies this plateau lasted...
Elliott AR, Steffey EP, Jarvis KA, Marshall BE.The hypoxic pulmonary vasoconstrictor response to unilateral hypoxia was analyzed in pentobarbital anesthetized dogs (n = 5), miniature swine (n = 5), and ponies (n = 5). The left and right lungs (LL, RL) were separately ventilated with the LL exposed to inspired oxygen concentrations (CIO2) of 100%, 12%, 8% or 4%, while the RL always received a CIO2 = 100%. Pulmonary blood flow distribution was measured using 15 microns radioactive microspheres. LL PAO2, and percent pulmonary blood flow diversion (%FD) were calculated at each CIO2. At CIO2 of 4% there were significant differences (P greater t...
Wagner AE, Bednarski RM, Muir WW.The hemodynamic effects of high arterial carbon dioxide pressure (PaCO2) during anesthesia in horses were studied. Eight horses were anesthetized with xylazine, guaifenesin, and thiamylal, and were maintained with halothane in oxygen (end-tidal halothane concentration = 1.15%). Baseline data were collected while the horses were breathing spontaneously; then the horses were subjected to intermittent positive-pressure ventilation, and data were collected during normocapnia (PaCO2, 35 to 45 mm of Hg), moderate hypercapnia (PaCO2, 60 to 70 mm of Hg), and severe hypercapnia (PaCO2, 75 to 85 mm of H...
Manohar M.Regional distribution of diaphragmatic blood flow (Q; 15-microns-diam radionuclide-labeled microspheres) was studied in normal (n = 7) and laryngeal hemiplegic (LH; n = 7) ponies to determine whether the added stress of inspiratory resistive breathing during maximal exercise may cause 1) redistribution of diaphragmatic Q and 2) crural diaphragmatic Q to exceed that in maximally exercising normal ponies. LH-induced augmentation of already high exertional work of breathing resulted in diminished locomotor exercise capacity so that maximal exercise in LH ponies occurred at 25 km/h compared with 3...
Sarazan RD, Starke WA, Krause GF, Garner HE.The cardiovascular effects of detomidine and xylazine were compared in six chronically instrumented, conscious ponies. Ponies were instrumented with a micromanometer in the left ventricular chamber, a Doppler flow probe on a coronary artery and sonomicrometer crystals in the left ventricular free wall. Heart rate, ventricular systolic pressure, stroke work, dP/dtmax, minute work and coronary blood flow were measured for 4 h following intravenous injection of detomidine at several doses or xylazine at 1.1 mg/kg. Both drugs caused a profound hypertensive response at 15 s post-injection. The magn...
Clark ES, Moore JN.The effects of slow intravenous (i.v.) infusion of a very low dosage of endotoxin (a cumulative dosage of 0.03 microgram/kg bodyweight [bwt] infused over 60 mins) were evaluated in six conscious healthy horses. Duodenal, right ventral colon, and caecal contractions were detected with strain gauge force transducers. Lateral caecal arterial blood flow was measured using transit time ultrasonic blood flow probes. Duodenal contractile activity was not significantly altered by infusion of endotoxin. In contrast, the contractile activity of the right ventral colon 90 and 270 mins after infusion of e...
Goetz TE, Manohar M, Nganwa D, Gustafson R.The effects of 1.1, 1.5 and 1.8 MAC (minimum alveolar concentration) isoflurane-02 anaesthesia on skeletal muscle blood flow, 02 delivery and vascular resistance were studied in the non-dependent region of seven healthy normothermic, isocapnoeic ponies. Muscle blood flow was determined with 15 microns diameter radionuclide labelled microspheres that were injected into the left ventricle. Muscle blood flow during anaesthesia was compared to unanaesthetised (control) measurements. Isoflurane administration caused a dose dependent decrease in mean aortic pressure, and skeletal muscle (temporalis,...
Trim CM, Moore JN, Clark ES.An ultrasonic flow probe was implanted around a branch of the left renal artery in five horses. The effects of dopamine were studied in the unsedated horses 10 days after surgery. Three experiments, separated by at least two days, were performed in random order on each horse. In two experiments, dopamine was infused intravenously for 60 mins at either 2.5 and 5.0 micrograms/kg bodyweight (bwt)/min. Saline was infused for 60 mins before and after each infusion, and for 180 mins in the third experiment as a control. Renal blood flow increased during administration of dopamine at both dose rates ...
Reef VB, Lalezari K, De Boo J, van der Belt AJ, Spencer PA, Dik KJ.Pulsed-wave Doppler echocardiography was performed on 30 clinically normal 1- to 6-year-old racing Standardbreds. There were 13 females, 13 geldings, and 4 stallions. Cardiac disease was not detected with M-mode, 2-dimensional real-time or pulsed-wave Doppler echocardiography. Normal flow velocities for right and left atrial outflow, right and left ventricular outflow, the aorta, and pulmonary artery were determined. Peak flow velocities for right and left atrial outflow occurred during the rapid filling phase and were higher toward the mitral valve (mean, 0.70 +/- 0.24 m/s) than toward the tr...
Manohar M.The present study was carried out 1) to compare blood flow in the costal and crural regions of the equine diaphragm during quiet breathing at rest and during graded exercise and 2) to determine the fraction of cardiac output needed to perfuse the diaphragm during near-maximal exercise. By the use of radionuclide-labeled 15-micron-diam microspheres injected into the left atrium, diaphragmatic and intercostal muscle blood flow was studied in 10 healthy ponies at rest and during three levels of exercise (moderate: 12 mph, heavy: 15 mph, and near-maximal: 19-20 mph) performed on a treadmill. At re...
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...
Allen D, Korthuis RJ, Clark S.A pump-perfused extracorporeal digital preparation was used to evaluate blood flow, arterial pressure, venous pressure, isogravimetric capillary filtration coefficient, capillary pressure, and vascular compliance in six normal horses. From these data, pre- and postcapillary resistances and pre- and postcapillary resistance ratios were determined. Vascular and tissue oncotic pressures were estimated from plasma and lymph protein concentrations, respectively. By use of the collected and calculated data, tissue pressure in the digit was calculated using the Starling equation. In the isolated equi...
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...
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% ...
Stewart RH.Traumatic injury to the central nervous system causes immediate damage and sets in motion a complex series of pathophysiologic events that result in further neuronal injury. This secondary damage seems to be related to changes in blood flow and pressure on a systemic, regional, and microvascular level. Currently, there is evidence that these changes are, in part, mediated by endogenous opioids and arachidonic acid metabolites, namely thromboxane A2. Medical management is generally designed to intervene at one or more stages in this secondary cascade of events. Further research should lead us t...
Stewart JH, Young IH, Rose RJ, Costas L, Barko AM.The distributions of ventilation-perfusion ratios, and the effects of 100% oxygen administration on the distributions, were studied in 3 foals from 4h to 9 days of age, using the multiple inert gas elimination technique. The distributions were calculated from the pulmonary clearance of 6 inert gases following infusion into a peripheral vein of a solution containing the inert gases. The results from a total of 8 studies showed several consistent features. The major findings were (i) the absence of low ventilation-perfusion ratios, i.e. regions where blood flow was greatly in excess of ventilati...
Manohar M.1. Transmural distribution of myocardial blood flow was studied using 15 micron diameter radionuclide-labelled microspheres in six normal ponies and nine splenectomized ponies at rest, and during maximal exercise performed without as well as with adenosine infusion (3 microM kg-1 min-1). The splenectomized ponies were also studied during submaximal exercise performed at 75% of the workload. 2. Maximal exertion in normal ponies increased heart rate (348%), mean arterial blood pressure (40.9%), rate-pressure product (563%), arterial O2 content (43.2%), and mean pulmonary artery pressure (247%). ...
Serteyn D, Mottart E, Michaux C, Micheels J, Philippart C, Lavergne L, Guillon C, Lamy M.Muscular microcirculation was studied in seven halothane anaesthetised horses in lateral recumbency using a laser Doppler flowmeter. A significant difference between the dependent and the uppermost triceps brachii was recorded. In the dependent muscles, microflow at first decreased and then increased up to the starting value. In the uppermost muscles, a significant rise of the microflow was measured.
Manohar M.Systemic distribution of blood flow was studied in 11 healthy adult grade ponies, using radionuclide-labeled microspheres (15 micron diameter) that were injected into the left ventricle. Measurements were made at rest, during severe exercise (SE) without furosemide, as well as during SE at 10 minutes and 120 minutes after furosemide administration (1.0 mg/kg, IV). During SE, heart rate, cardiac output, mean aortic pressure, and whole body O2 consumption were 220 +/- 4 beats/min, 720 +/- 44 ml/min/kg, 169 +/- 4 mm of Hg, and 126 +/- 9 ml of O2/min/kg, respectively. With SE performed after furos...
Manohar M.Regional distribution of brain blood flow (radionuclide labelled 15 microns diameter microspheres) and O2 supply were studied in 11 healthy adult grade ponies at rest and during severe exercise (SE) performed on a treadmill (heart rate = 220 +/- 4 beats X min-1; VO2 = 126 +/- 9 ml X min-1 X kg-1). During SE, the mean aortic pressure increased to 169 +/- 4 mm Hg and the pHa, PaCO2 and PaO2 were 7.213 +/- 0.010, 30 +/- 1 mm Hg and 85 +/- 4 mm Hg, respectively. The hemoglobin concentration increased by 59.6% with SE. Whereas blood flow increased in the cerebellar gray matter (96%), pons (39.5%) a...
Manohar M, Goetz TE.Blood flow to the brain, kidneys, adrenal glands, pancreas, and small intestine was studied in 8 healthy ponies while awake (control) and during 1.0, 1.5, and 2.0 minimal alveolar concentrations (MAC) of anesthesia produced, using halothane vaporized in oxygen. During the anesthesia steps, intermittent positive-pressure ventilation was used to ensure isocapnia. Organ blood flow was determined with 15-micron (diameter) radionuclide-labeled microspheres, after allowing 30 minutes of equilibration at each of the 3 preestablished end-tidal halothane concentrations. The sequence of 1.0, 1.5, and 2....
Allen D, Korthuis RJ, Clark S.A pump-perfused extracorporeal digital preparation was used to evaluate blood flow, arterial pressure, venous pressure, isogravimetric capillary filtration coefficient, capillary pressure, and vascular compliance in six normal horses. From these data, pre- and postcapillary resistances and pre- and postcapillary resistance ratios were determined. Vascular and tissue oncotic pressures were estimated from plasma and lymph protein concentrations, respectively. By use of the collected and calculated data, tissue pressure in the digit was calculated using the Starling equation. In the isolated equi...
Sellers AF, Lowe JE, Cummings JF.Some support for both serotonin and substance P as biotransmitters in the equine large colon is presented. Close arterial injections of small quantities of each of these were effective, respectively, in stimulating marked increases in coordinated pressure peaks in the vicinity of the pelvic flexure, with modest (serotonin) or marked (substance P) increase in colon artery blood flow. Both the acaricide, amitraz, and the tranquilizer xylazine appeared to act on the equine large colon via yohimbine-sensitive alpha 2-adrenergic receptors.
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...
Tetens J, Eades SC, Hosgood G, Koch CE, Moore RM.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...
Stadler P, Weinberger T, Deegen E.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...
Raisis AL.The objective of this review was to describe the methodology and limitations of techniques that have been used to measure skeletal muscle blood flow in anaesthetized horses. Methods: Pubmed, personal files. Conclusions: Numerous techniques have been used in horses to study skeletal muscle blood flow during anaesthesia and after the administration of vasoactive agents. Of the available techniques, blood flow measurements are limited to either microvascular flow (radioactive xenon, laser Doppler flowmetry) or total blood flow (radioactive microspheres, electromagnetic flowmetry, Doppler ultrason...
Manohar M, Goetz TE.To examine regional distribution of blood flow in the brain of horses at rest and during exercise. Methods: 9 clinically normal horses. Methods: Regional brain blood flow was measured using radionuclide-labeled 15-microns-diameter microspheres injected into the left ventricle, while reference blood samples were obtained from the aorta. Results: At rest, cerebral cortex and caudate nuclei received significantly higher blood flow, compared with cerebral white matter. A similar perfusion heterogeneity existed in the cerebellum. In the brain stem, a gradual tapering of blood flow from thalamus-hyp...
Ingle-Fehr JE, Baxter GM.To measure blood flow in the palmar digital artery and laminae corium, using ultrasonic and laser Doppler flowmetry, respectively. Methods: 6 healthy horses. Methods: Digital blood flow and laminar perfusion, respectively, were measured by placing a flow probe around the palmar digital artery and a laser Doppler flow probe in a hole in the dorsal aspect of the hoof wall. All horses were given saline (0.9% NaCl) solution (1 L, IV, during a 30-minute period). Seven days later, each horse was given endotoxin (0.1 microgram/kg of body weight, IV, in 1 L of saline solution, during a 30-minute perio...
Adair HS, Goble DO, Schmidhammer JL, Shires GM.To measure changes in laminar microvascular blood flow (LMBF) over time in healthy horses and horses in the prodromal stage of black walnut-induced laminitis and to determine the effects of glyceryl trinitrate application on LMBF in horses with acute laminitis. Methods: 10 healthy adult horses. Methods: Laser Doppler flowmetry was used to measure LMBF Baseline measurements were obtained, horses were given deionized water via a nasogastric tube, and measurements were obtained hourly for 12 hours. Twenty-four hours later, baseline measurements were again obtained, and horses were given black wal...
Manohar M.Regional distribution of brain blood flow (radionuclide labelled 15 microns diameter microspheres) and O2 supply were studied in 11 healthy adult grade ponies at rest and during severe exercise (SE) performed on a treadmill (heart rate = 220 +/- 4 beats X min-1; VO2 = 126 +/- 9 ml X min-1 X kg-1). During SE, the mean aortic pressure increased to 169 +/- 4 mm Hg and the pHa, PaCO2 and PaO2 were 7.213 +/- 0.010, 30 +/- 1 mm Hg and 85 +/- 4 mm Hg, respectively. The hemoglobin concentration increased by 59.6% with SE. Whereas blood flow increased in the cerebellar gray matter (96%), pons (39.5%) a...
Pietra M, Guglielmini C, Nardi S, Gandini G, Cipone M.To describe the pulsed-wave Doppler tracing of the equine lateral palmar digital artery and its modification in relation to standardized changes in posture. Methods: 17 healthy Saddlebred horses. Methods: Pulsed-wave Doppler examinations of left and right lateral palmar digital arteries of the horses were performed. The baseline examination was performed on each forelimb while horses were standing squarely with the body weight equally distributed among the 4 limbs (BED position). For each forelimb, the examination was repeated during 3 standardized modifications of the horse's posture (non-wei...
Verhaar N, Grages AM, Bienert-Zeit A, Schwieder A, Reineking W, Hewicker-Trautwein M, Kästner S, Geburek F.Ancillary diagnostic methods to enhance the accuracy of viability assessment have not been established for use in clinical practice. Objective: To assess intestinal microperfusion measured by Laser Doppler Flowmetry and Spectrophotometry (LDFS) in naturally occurring small intestinal strangulations of different origins and to compare this between viable and non-viable segments. Methods: Prospective clinical trial. Methods: Forty horses undergoing colic surgery for naturally occurring small intestinal strangulations were included. Tissue oxygen saturation (tSO), haemoglobin (tHB) and blood flow...
Verhaar N, Reineking W, Hewicker-Trautwein M, Grages AM, Kästner SBR, Geburek F.To evaluate the use of laser Doppler flowmetry and spectrophotometry (LDFS) for large intestinal viability assessment in horses with naturally occurring large intestinal strangulations. Methods: By use of LDFS, intestinal microperfusion was quantified as tissue oxygen saturation (tSo2), hemoglobin (tHB), and blood flow (tBF) in cases with large colon volvulus and small colon strangulations undergoing colic surgery (n = 17). Intestinal biopsies were taken from the pelvic flexure in all large colon cases and in small colon cases that underwent intraoperative euthanasia. Measurements were compare...
Manohar M.Systemic distribution of blood flow was studied in 11 healthy adult grade ponies, using radionuclide-labeled microspheres (15 micron diameter) that were injected into the left ventricle. Measurements were made at rest, during severe exercise (SE) without furosemide, as well as during SE at 10 minutes and 120 minutes after furosemide administration (1.0 mg/kg, IV). During SE, heart rate, cardiac output, mean aortic pressure, and whole body O2 consumption were 220 +/- 4 beats/min, 720 +/- 44 ml/min/kg, 169 +/- 4 mm of Hg, and 126 +/- 9 ml of O2/min/kg, respectively. With SE performed after furos...
Kenney DW, Elsner RW, Franklin DL.Bood flow was measured in the external iliac artery of the
horse during standing and walking. The Franklin Doppler
blood flow-telemetry system was used in this study. The transducer was placed on the external iliac artery using a retroperitoneal approach through the vaginal wall.
Clark ES, Moore JN.The effects of slow intravenous (i.v.) infusion of a very low dosage of endotoxin (a cumulative dosage of 0.03 microgram/kg bodyweight [bwt] infused over 60 mins) were evaluated in six conscious healthy horses. Duodenal, right ventral colon, and caecal contractions were detected with strain gauge force transducers. Lateral caecal arterial blood flow was measured using transit time ultrasonic blood flow probes. Duodenal contractile activity was not significantly altered by infusion of endotoxin. In contrast, the contractile activity of the right ventral colon 90 and 270 mins after infusion of e...
Reddy VK, Kammula RG, Randolph A, Graham TC, Srungaram SK.Studies on regional blood flow to the stomach and small intestine were performed in 9 anesthetized ponies. Carbonized microspheres (15 +/- 5 micron in diameter) labeled with 85Sr were injected into the left atrium to determine blood flow distribution. In 4 ponies, the regional flows to mucosal-submucosal layers of the stomach and the small intestine were also measured. The nonglandular region of the stomach received the least blood per 100 g of tissue, and the duodenum received the greatest. The regional blood flow to the duodenum was significantly higher than that to the glandular stomach reg...
Sandler GA, Scott EA.Vascular responses occurring with pneumatic tourniquet application were evaluated in the equine thoracic limb. Recordings of pressure (arterial and venous) and flow (arterial) distal to the tourniquet were made for 60 minutes. Reactive hyperemia was observed; however the increased flow was neither of a sufficient duration nor of a great enough volume for total repayment of flow loss.
Deumer J, de Haan F, Tulp MT, van den Hoven R.The effects of an oral isoxsuprine-resin preparation on the blood flow in the thoracic limb of seven horses was determined by thermography. Treatment with the oral resin preparation resulted in increased skin temperatures compared with the non-medicated controls. The maximal temperature differences, 2.2 degrees C for the horses treated with 0.9 mg/kg and 1.8 degrees C for the horses treated with 1.2 mg/kg, occurred four hours after dosing. Plasma total isoxsuprine, determined in three horses, was detectable two hours after oral dosing and maximal eight hours after dosing, but free isoxsuprine ...
Stewart RH.Traumatic injury to the central nervous system causes immediate damage and sets in motion a complex series of pathophysiologic events that result in further neuronal injury. This secondary damage seems to be related to changes in blood flow and pressure on a systemic, regional, and microvascular level. Currently, there is evidence that these changes are, in part, mediated by endogenous opioids and arachidonic acid metabolites, namely thromboxane A2. Medical management is generally designed to intervene at one or more stages in this secondary cascade of events. Further research should lead us t...
Paulussen E, Decloedt A, Vera L, Lefere L, van Loon G.Venous stenosis, a possible cause of jugular dilatation and congestion, is well known in human medicine but has poorly been described in horses. Objective: To report unilateral jugular vein stenosis as a cause of jugular vein dilatation in horses and describe treatment by percutaneous transluminal angioplasty (PTA). Methods: Case report. Methods: Details of horses diagnosed with unilateral jugular stenosis were retrieved from medical records. Results: Five horses were presented with a non-painful, unilateral dilatation of the jugular vein of which two horses showed headshaking during exercise....
Scott EA, Sandler GA.Blood flow (milliliter/minute) was measured in the medial palmar artery of 12 horses, using electromagnetic flow equipment. Extraluminal flow probes were surgically placed around the artery and base-line blood flows were recorded during surgical manipulation. After horses had recovered from anesthesia, blood flows were recorded each day for 11 days. According to mean average blood flows, horses were allotted to two groups: group 1--those with predominately normal flow characteristics, and group 2--those horses with predominately abnormal flow features. Average daily mean blood flows in the med...
Boatwright RB, Williams DO, Rugh KS, Sarazan RD, Ross CR, Garner HE, Griggs DM.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...
Raisis AL, Young LE, Meire H, Walsh K, Taylor PM, Lekeux P.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...
Harkins JD, Mundy GD, Stanley S, Woods WE, Sams RA, Richardson DR, Grambow SC, Tobin T.Isoxsuprine is reported to be a peripheral vasodilator used in human and veterinary medicine to treat ischaemic vascular disease. In horses, it is generally administered orally to treat navicular disease and other lower limb problems. To define the scope and duration of its pharmacological responses after oral administration, 6 horses were dosed with isoxsuprine HCl (1.2 mg/kg bwt) q. 12 h for 8 days and then tested to assess the duration and extent of pharmacological actions. There was no significant difference between isoxsuprine and control treatment values for heart rate, spontaneous activ...
Wagerle LC, Orr JA, Shirer HW, Kiorpes AL, Fraser DB, DeSoignie RC.The purpose of these studies was to examine the time course of the cerebrovascular response to acute hypoxia in unanesthetized ponies. An electromagnetic flow transducer chronically placed on the internal carotid artery of the pony allowed continuous recording of internal carotid artery blood flow (ICBF) which has been shown to be representative of cerebral blood flow (CBF). The ponies were subjected to three levels of acute isocapnic hypoxia (PaO2 = 62, 44, and 39 mm Hg for hypoxia level I, II, and III, respectively), and the temporal and steady-state cerebrovascular response was examined. IC...
Lee YH, Clarke KW, Alibhai HI.The effects on intramuscular blood flow and cardiopulmonary parameters of changing from anaesthesia with halothane to isoflurane and vice versa were investigated in six ponies (small horses). Anaesthesia was induced with xylazine, ketamine and diazepam, maintained for one hour with halothane at an end tidal concentration of 1 per cent and then with isoflurane at 1.5 per cent for a further hour (halo/iso). On another occasion the order in which the volatile agents were administered was reversed (iso/halo). After one hour of anaesthesia the mean (sd) arterial blood pressure (MAP) and cardiac out...
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. ...
Gilhooly MH, Eades SC, Stokes AM, Moore RM.To measure and compare palmar digital venous plasma nitric oxide (NO) concentrations and digital arterial blood flow after application of topical nitroglycerine (NTG). Methods: Experimental study. Methods: Healthy adult horses (n=8). Methods: Digital blood flow was measured by an ultrasonic Doppler flow probe surgically implanted around the medial palmar digital artery. Blood was collected from a catheter placed in the medial palmar digital vein for quantification of NO. NTG patches, NTG ointment or control patches were placed over the palmar digital vessels at the level of the fetlock. Two ho...
