Hemodynamics in horses refers to the study of blood flow and the forces involved in circulation within the equine cardiovascular system. It encompasses the examination of heart function, blood pressure, and the distribution of blood to various tissues and organs. Key parameters in equine hemodynamics include cardiac output, vascular resistance, and blood volume. These factors are integral to understanding how horses respond to exercise, stress, and various health conditions. This page aggregates peer-reviewed research studies and scholarly articles that explore the mechanisms, measurement techniques, and clinical implications of hemodynamic processes in equine physiology and veterinary medicine.
Vigani A, Shih A, Queiroz P, Pariaut R, Gabrielli A, Thuramalla N, Bandt C.New volumetric variables of preload, such as total end-diastolic volume index (TEDVI) and active circulation volume index (ACVI) and central blood volume index (CBVI), may represent good indicators of preload and predictors of fluid responsiveness. During acute changes of intravascular volume these variables would allow a more accurate intervention. Objective: The aim of the present study was to investigate the changes in TEDVI, ACVI, CBVI in a juvenile model of hemorrhagic shock and resuscitation. Methods: Twelve anaesthetized ponies (3-8 months of age) were studied at normovolaemia (BASE), a...
Hatazoe T, Kubota C, Fujiki M, Misumi K.To evaluate the influence of mating behavior on cardiac function, changes in heart rate (HR), electrocardiogram (ECG), hematocrit (Hct) and serum concentration of alpha-atrial natriuretic peptide (alpha-ANP) were evaluated in 10 clinically sound Thoroughbred stallions before and after mating behavior. The stallions were submitted twice to experimental pseudomating in the same month in 2009 and 2010. Measurements and blood samples were collected at a stable before mating (baseline) and at a covering yard before and after mating. ECG was recorded by a Holter-ECG system. Arrhythmias were detected...
Tam K, Rezende M, Boscan P.To compare and correlate right atrial pressure, which represents central venous pressure (CVP) to jugular vein pressure (JVP) in laterally recumbent horses under anesthesia. Methods: Retrospective clinical trial. Methods: Seven adult healthy horses (411 ± 8.7 kg). Methods: Horses were sedated with IV xylazine and anesthesia was obtained with IV ketamine and diazepam. Anesthesia was maintained with sevoflurane in oxygen. All horses were positioned in left lateral recumbency. An 8F catheter introducer was inserted into the right jugular vein to measure JVP. An 8F catheter introducer was i...
Bailey CS, Sper RB, Schewmaker JL, Buchanan CN, Beachler TM, Pozor MA, Whitacre MD.The objective of this study was to use Doppler ultrasound technology to determine whether pentoxifylline administration increased uterine blood flow in normal pregnant pony mares. Thirteen pregnant pony mares between 18 and 190 d of gestation (mean ± SEM, 101 ± 55) were utilized for the study during two trial periods. In each trial, pentoxifylline (17 mg/kg by mouth every 12h, diluted in syrup) was administered to half of the mares for 3 d, while the other mares were treated with syrup only. Doppler measurements were obtained from the right and left uterine arteries from each mare for 2 d pr...
Kruger K, Stegmann GF, Becker PJ.To characterize the cardiorespiratory and electrocardiographic effects of the combined administration of phenylbutazone and romifidine. Methods: Prospective four-period, four-treatment, blinded, randomized, crossover trial. Methods: Five, healthy, mixed breed horses. Methods: Prior to treatment administration, a catheter was introduced into the intra-thoracic cranial vena cava via the jugular vein and a subcutaneously located carotid artery was catheterised. All treatments were administered intravenously (IV) and consisted of saline placebo (PLC), phenylbutazone (PBZ, 4.4 mg kg(-1) ) romifidin...
Slack J, Boston R, Driessen B, Reef V.To evaluate the effect of general anesthesia on plasma cTnI concentrations in horses. Methods: Thirty-two horses undergoing general anesthesia and either elective surgery or MRI without surgery were prospectively studied. Twenty-nine horses (22 surgical, 7 imaging) completed the study. Plasma cTnI concentrations were determined prior to anesthesia and at 6, 12 and 24 h following discontinuation of the inhalant anesthetic. Results: All horses had cTnI values within the reference range at all time points. Six horses (21%) developed detectable cTnI 6 or 12 h following anesthesia. Risk factors f...
Dias DP, Teixeira LG, Canola PA, Albernaz RM, Marques JA, Neto JC.The purpose of this investigation was to evaluate surgical catheter implantation in the facial artery of horses and the long-term maintenance of such arteries using heparin and ascorbic acid as filling solution. Nine horses were implanted with a polyurethane catheter. The catheters were flushed with a heparin/ascorbic acid solution every 8h and remained patent for 25 days. Arterial blood samples were collected twice a day, and one exercise test that included serial blood samples and arterial pressure recordings was performed on a treadmill. Polyurethane catheters surgically implanted in the fa...
Pozor MA, Muehlhaus J, King A, Macpherson ML, Troedsson MH, Bailey CS.The objective was to investigate the effects of pentoxifylline (PTX) on testicular perfusion and sperm production in stallions. In a preliminary study, six mature Miniature horse stallions were given 0, 8.5, or 17.0 mg/kg of PTX orally, twice daily, for 3 d. Total Arterial Blood Flow Rate (TABFR) was higher (P < 0.05) in all treated versus control stallions during and after treatment. Two months later (during the fall and winter), the same stallions received either 0 or 17 mg/kg of PTX orally, twice daily for 60 d. Resistance and pulsatility indices (RI and PI, respectively) decreased in PT...
Lindner A, Wäschle S, Sasse HH.The blood lactate concentration (LA) and heart rate (HR) of 10 horses exercising in water on a treadmill were examined. With the water at 10 and 50% of the withers height (WH), the blood LA increased up to mean values around 1.9 mm during the standardized exercise test (SET) until after step 3 of 5 (each step lasted 5 min, speed increasing step by step). Thereafter, blood LA of horses remained constant, while with the water at 80% of WH, the blood LA decreased from the mean peak of 2.16 ± 0.62 mm after the 4th step. The HR of the horses increased to 132 ± 14 beats/min until the 3rd step of S...
Villalba M, Santiago I, Gomez de Segura IA.Lidocaine and ketamine are administered to horses as a constant rate infusion (CRI) during inhalation anaesthesia to reduce anaesthetic requirements. Morphine decreases the minimum alveolar concentration (MAC) in some domestic animals; when administered as a CRI in horses, morphine does not promote haemodynamic and ventilatory changes and exerts a positive effect on recovery. Isoflurane-sparing effect of lidocaine, ketamine and morphine coadministration has been evaluated in small animals but not in horses. Objective: To determine the reduction in isoflurane MAC produced by a CRI of lidocaine ...
Norton JL, Nolen-Walston RD, Underwood C, Boston R, Slack J, Dallap BL.Central venous pressure (CVP) is a used as an estimation of intravascular volume status in various species. Techniques for measuring CVP in horses have been described, but the repeatability of these readings at a single time point or over time has not been established. Objective: That CVP measurements in healthy adult horses would be repeatable at each time point, that these readings would be reproducible over time, and that alteration in head position relative to the heart would alter CVP. Methods: Ten healthy adult research horses. Methods: In an experimental study, horses were instrumented ...
Norton JL, Nolen-Walston RD, Underwood C, Slack J, Boston R, Dallap BL.Central venous pressure (CVP) customarily has been measured in veterinary patients with water manometry. However, many institutions are now using stallside electronic monitors in both anesthesia and intensive care units for many aspects of patient monitoring. Objective: Electronic stall side monitoring devices will agree with water manometry for measurement of CVP in horses. Methods: Ten healthy adult horses from the university research herd. Methods: Central venous catheters were placed routinely, and measurements were obtained in triplicate with each of the 3 methods every 12 hours for 3 day...
Satué K, Domingo R.During pregnancy, the coordinated interaction of the components of the renin-angiotensin-aldosterone system (RAAS) plays a vital role in accommodating the cardiovascular, haemodynamic and haematological needs imposed by foetal development and the placenta. This significantly influences the birth weight of the neonate and foetal viability. Although the evolution of each of the components of this system has been widely described in various species, it has not yet been clarified in the mare. Thus, the objectives of the present research were: 1) to establish reference values for renin (REN), angio...
Nolen-Walston RD, Norton JL, Navas de Solis C, Underwood C, Boston R, Slack J, Dallap BL.Central venous pressure (CVP) is used in many species to monitor right-sided intravascular volume status, especially in critical care medicine. Objective: That hypohydration in adult horses is associated with a proportional reduction in CVP. Methods: Ten healthy adult horses from the university teaching herd. Methods: In this experimental study, horses underwent central venous catheter placement and CVP readings were obtained by water manometry. The horses were then deprived of water and administered furosemide (1 mg/kg IV q6h) for up to 36 hours. Weight, CVP, vital signs, PCV, total protein (...
Honnens A, Weisser S, Welter H, Einspanier R, Bollwein H.The objective of this study was to investigate the relationships between uterine perfusion and estrogen, progesterone and the uterine nitric oxide synthase (NOS) system in five trotter mares during the estrous cycle. Color Doppler sonography for measurement of uterine blood flow and collection of blood for determination of plasma estrogen and progesterone concentrations were performed on days 0 (= ovulation), 1, 5, 11 and 15 and daily during estrus (days -1 to -4) of one estrous cycle; endometrial biopsy collection for mRNA expression analysis of NOS and estrogen receptors was performed on day...
Canola PA, Perotta JH, Laskoski LM, Escobar A, Melo e Silva CA, Canola JC, Johnson PJ, Valadão CA.Standing surgical procedures are being employed to an ever-greater extent in horses. Pneumoperitoneum during abdominal surgery might adversely affect the work of breathing. Objective: To determine whether development of pneumoperitoneum during abdominal surgery adversely influences the work of breathing. Methods: Eight healthy mature horses were equipped with carotid artery and thoracic vena cava catheters and an intraluminal manometry system. The following measurements were obtained before and at +5, +10, +15 and +30 min following establishment of pneumoperitoneum by paralumbar puncture using...
Flores J, Corvera Poiré E, del Rio JA, López de Haro M.We consider a simple model to give a plausible mechanical explanation of what are the actual resting heart rates of mammals optimized for. We study what is the optimal frequency for a viscoelastic fluid circulating in a pulsatile way through a network of tubes and conclude that the heart rate is not optimized to transport blood through the whole net. Rather, actual resting heart rates of mammals happen at frequencies that optimize flow in vessels of radii that correspond to large arteries, which bring oxygenated blood rapidly far away from the heart, towards head and limbs. Our results for the...
Peiró JR, Barnabé PA, Cadioli FA, Cunha FQ, Lima VM, Mendonça VH, Santana AE, Malheiros EB, Perri SH, Valadão CA.The clinical efficacy of IV infusion of lidocaine for treatment of equine endotoxemia has not been studied. Objective: Lidocaine infusion after exposure to lipopolysaccharide (LPS) will inhibit the inflammatory response and have inhibitory effects on the hemodynamic and cytokine responses to endotoxemia. Methods: Twelve horses. Methods: Two equal groups (n=6): saline (GI) and lidocaine (GII). In all animals, endotoxin (500 ng/kg body weight [BW]) was injected intraperitoneally over 5 minutes. Twenty minutes later, animals received a bolus of GI or GII (1.3 mg/kg BW) over 5 minutes, followed by...
Marcilla MG, Schauvliege S, Duchateau L, Gasthuys F.To evaluate the cardiopulmonary effects of two different constant rate infusions (CRI) of dexmedetomidine (1 and 1.75 microg kg(-1 )hour(-1)) in experimental ponies. Methods: Six healthy ponies (mean 306 +/- SD 71 kg, 7.0 +/- 1.6 years). Methods: Prospective, randomized, experimental study. Methods: After premedication with intravenous (IV) dexmedetomidine (3.5 microg kg(-1)), anaesthesia was induced (T0) with ketamine (2.2 mg kg(-1) IV) and midazolam (0.06 mg kg(-1) IV) and maintained with isoflurane (Fe'ISO 1.50%) in 55% oxygen for 150 minutes. Normocapnia was maintained using artificial ven...
Sedacca CD, Bright JM, Boon J.Univentricular atrioventricular (AV) connections are rare and complex congenital cardiac anomalies in which both AV valves communicate into a large, common (single) receiving chamber. The common chamber can be of left, right, or mixed ventricular morphology. Although well documented in people, reports of the double-inlet ventricle malformation are rare in the veterinary literature. This report provides description of an Arabian horse with a double-inlet univentricular connection of left ventricular type, a hypoplastic subpulmonary right ventricle, two muscular ventricular septal defects, and a...
Brosnan RJ, Steffey EP, Esteller-Vico A, Vaughan B, Liu IK.Digital perfusion pressure (DPP) equals mean arterial pressure (MAP) at the hoof coronet minus digital interstitial pressure (DIP) within the hoof. To test whether lamellar blood flow (LBF) changes proportionately to DPP, anesthesia was induced and maintained with isoflurane in six horses to target a MAP of 60 mmHg. Arterial, venous, and hoof interstitial pressures were measured in each pelvic limb. LBF was measured using fluorescent microspheres during dobutamine infusions targeting either 60 (low), 80 (medium), or 100 (high) mmHg MAP. Following euthanasia, hoof lamina was collected for micro...
Valverde A, Rickey E, Sinclair M, Rioja E, Pedernera J, Hathway A, Cruz A.The effects of lidocaine combined with medetomidine or lidocaine alone on cardiovascular function during anaesthesia and their effects on recovery have not been thoroughly investigated in isoflurane-anaesthetised horses. Objective: To determine the effects of an intraoperative i.v. constant rate infusion of lidocaine combined with medetomidine (Group 1) or lidocaine (Group 2) alone on cardiovascular function and on the quality of recovery in 12 isoflurane-anaesthetised horses undergoing arthroscopy. Objective: The combination would depress cardiovascular function but improve the quality of rec...
Kruger K, Stegmann GF.A partial intravenous protocol was used successfully to maintain anaesthesia in 5 healthy horses. Horses were premedicated with acepromazine, romifidine and butorphanol, induced with guaifenesin and ketamine and maintained on a constant rate infusion of lidocaine, ketamine and medetomidine together with halothane inhalation anaesthesia. Mean end-tidal halothane concentration to maintain a surgical plane of anaesthesia was 0.8 +/- 0.2%. Mean dobutamine requirement to maintain mean arterial pressure above 9.31 kPa was 0.42 +/- 0.3 microg/kg/min. The administration of relatively low doses of lido...
Ohta M, Wakuno A, Okada J, Kodaira K, Nagata S, Ito M, Oku K.To evaluate the effects of IV fentanyl administration on the end-tidal sevoflurane concentration (ET(SEVO)) in thoroughbred racehorses, the ET(SEVO) required for internal fixation of longitudinal fractures was compared between horses anesthetized with sevoflurane-fentanyl (Group SF; n=9) and those anesthetized with sevoflurane alone (Group S; n=9). The loading dose of fentanyl (5.0 µg/kg) was administered over 15 min followed by a maintenance dose of fentanyl (0.1 µg/kg/min) throughout the operation in Group SF. The mean ET(SEVO) during the operation in Group SF (2.6 ± 0.2%) was significant...
Caure S, Cousty M, Tricaud C.Three groups of horses scheduled for arthroscopic surgery were premedicated with 0.025 mg/kg acepromazine, 88 microg/kg romifidine and 25 mg/kg guaifenesin, and anaesthesia was induced with 2.2 mg/kg ketamine. In group 1 (14 horses), anaesthesia was maintained by halothane vaporised in oxygen, with supplementary doses of 20 microg/kg romifidine and 0.5 mg/kg ketamine every 20 minutes. The 17 horses in group 2 were maintained as for group 1; however, an additional dose of 0.05 mg/kg butorphanol was administered before the first incision. The 14 horses in group 3 were maintained as for group 2, ...
Schauvliege S, Gozalo Marcilla M, Duchateau L, Martens A, Vlaminck L, Pille F, Declercq J, Levet T, Gasthuys F.No studies have been reported on the effects of enoximone in anaesthetised colic horses. Objective: To examine whether enoximone improves cardiovascular function and reduces dobutamine requirement in anaesthetised colic horses. Methods: Forty-eight mature colic horses were enrolled in this prospective, randomised clinical trial. After sedation (xylazine 0.7 mg/kg bwt) and induction (midazolam 0.06 mg/kg bwt, ketamine 2.2 mg/kg bwt), anaesthesia was maintained with isoflurane in oxygen and a lidocaine constant rate infusion (15 mg/kg bwt, 2 mg/kg/h). Horses were ventilated (PaCO2 < 8.00 kPa)...
Muir WW, Lerche P, Erichson D.Studies have demonstrated the clinical usefulness of propofol for anaesthesia in horses but the use of a concentrated solution requires further investigation. Objective: To determine the anaesthetic and cardiorespiratory responses to a bolus injection of 10% propofol solution in mature horses. Methods: Three randomised crossover experimental trials were completed. Trial 1: 6 horses were selected randomly to receive 10% propofol (2, 4 or 8 mg/kg bwt i.v.). Trial 2: 6 horses received 1.1 mg/kg bwt i.v. xylazine before being assigned at random to receive one of 5 different doses (1-5 mg/kg bwt) o...
Tearney CC, Guedes AG, Brosnan RJ.Accurate blood pressure measurement is essential for effective clinical assessment and appropriate interventions in anaesthetised horses. Information on the accuracy of oscillometry for blood pressure measurement on the appendages of mature horses is limited. Objective: To assess equivalence between invasive and oscillometric blood pressures at different anatomic locations in horses. Methods: Prospective experimental study using 6 healthy mature horses. Methods: Blood pressure was measured invasively in the right transverse facial artery and noninvasively by oscillometry in nondependent limbs ...
Corley KT.Successful treatment with inotropes and vasopressors depends on an understanding of the interplay of flow, pressure, and resistance in the cardiovascular system and an appreciation of the pathophysiologic mechanisms leading to inadequate tissue perfusion. Any treatment strategy is necessarily a compromise between the requirements of different vascular beds.Furthermore. the underlying hemodynamic derangements can change rapidly. Therefore. inotropes and vasopressors should be titrated to measures of improved hemodynamic status, and the treatments should be frequently reviewed.
DeRossi R, Módolo TJ, Maciel FB, Pagliosa RC.Short duration of analgesia is among the limitations of a single epidural injection with lidocaine in horses. Objective: To evaluate the effectiveness and safety of epidural lidocaine in combination with either tramadol or neostigmine for perineal analgesia in horses. Methods: Epidural catheters were placed in 6 saddle horses that then were given 3 treatments: 2% lidocaine (0.2 mg/kg bwt) alone, 2% lidocaine (0.2 mg/kg bwt) plus tramadol (0.5 mg/kg bwt), and 2% lidocaine (0.2 mg/kg bwt) plus neostigmine (1.0 μg/kg bwt). The order of treatments was randomised. Haemodynamic variables, respirato...
Ward DS, Fessler JF, Bottoms GD, Turek J.Ponies with electromagnetic blood flow transducers implanted around the main pulmonary and left main coronary arteries, were used to evaluate effects of chronic sublethal endotoxin on cardiac output (CO), stroke volume, and left coronary blood flow (LCBF). Plasma thromboxane (TX), as indicated by TXB2, prostacyclin as indicated by 6-keto-prostaglandin (PG) F1 alpha, and hematologic and blood chemical values also were evaluated. Over 24 hours, 2 groups of ponies were given progressively increasing IV and intraperitoneal doses of Escherichia coli lipopolysaccharide (LPS) at 0, 6, 12, and 18 hour...
Manohar M, Bisgard GE, Bullard V, Will JA, Anderson D, Rankin JH.Hemodynamics, myocardial function, and regional myocardial blood flow (MBF) were measured in 6 closed-chest ponies anesthetized with ketamine hydrochloride before (control) and after creation of acute right ventricular systolic hypertension (RVSH) during normoxia and isocapnic hypoxia. The right ventricular (RV) systolic pressure during each RVSH approached 90 mmHg. There were significant alterations in the pattern of total ventricular MBG distribution in favor of the RV. Because RV myocardium received proportionate increments to its endocardium as well as epicardium, it is concluded that auto...
Adami C, Westwood-Hearn H, Bolt DM, Monticelli P.The objective of this study was to determine the prevalence of intraoperative electrolyte disturbances and risk factors associated with perianesthetic death in horses undergoing colic surgery. The files of 120 horses meeting the inclusion criteria were reviewed. Data retrieved from the medical records, including demographic data and the occurrence of electrolyte disturbances and other intraoperative complications, were analyzed with a two step-approach by univariate and multivariate logistic regression models. Hypocalcemia was the most represented electrolyte disturbance (52.5%), followed by h...
Sage AM, Keating SC, Lascola KM, Schaeffer DJ, Clark-Price SC.To evaluate cardiopulmonary and recovery characteristics of horses administered total intravenous anesthesia (TIVA) with xylazine and ketamine combined with midazolam or propofol. Methods: Randomized crossover study. Methods: A group of eight adult horses, aged 7-22 years, weighing 493-740 kg. Methods: Horses were administered xylazine (1 mg kg) intravenously (IV), and anesthesia was induced with ketamine (2.2 mg kg) IV. Anesthesia was maintained for 45 minutes via IV infusion of xylazine (0.016 mg kg minute) and ketamine (0.03 mg kg minute) combined with midazolam at 0.002 mg kg minute (MKX),...
Vengust M, Staempfli H, Viel L, Heigenhauser G.Horses develop high pulmonary pressures during exercise, which force fluid out of pulmonary capillaries. Specific airway diseases in horses, especially those associated with hypoxaemia, hypercapnoea and acidosis may influence pulmonary haemodynamics and pulmonary interstitial fluid equilibrium. Objective: This study was designed to determine fluid flux (J(V-A) l/min) across the lung in exercising horses treated chronically with acetazolamide. Methods: Six horses were exercised on a treadmill until fatigue without (Con) and with chronic carbonic anhydrase (CA) inhibition (AczTr) and associated ...
Nicholl TK, Fregin GF, Gerber NH.The literature on exercise physiology in the horse with special reference to swimming is briefly reviewed. The use of a pool for swimming horses is described and a technique discussed for the collection of haematologic and haemodynamic data using this form of exercise.
Watney GC, Norman WM, Schumacher JP, Beck E.The accuracy of a reflectance pulse oximeter was determined in 22 anesthetized horses. Oximetric blood oxygen saturation was measured with the pulse oximeter probe attached to the mucosa of the mandible. Arterial blood oxygen saturation (SaO2) was calculated from arterial blood gas values and the equine blood oxygen dissociation curve. The mean +/- SD difference between oximetric blood oxygen saturation and SaO2 was -1.3 +/- 3.1% for values of SaO2 ranging from 80 to 100%. The difference between oximetric blood oxygen saturation and SaO2 was influenced by SaO2, the mean arterial blood pressure...
Robertson JT, Muir WW.A xylazine and butorphanol drug combination produced minimal and transient hemodynamic effects and no significant respiratory depression when administered to 6 healthy horses. Combining xylazine and butorphanol produced a synergistic analgesic effect and provided good chemical restraint for a standing surgical procedure.
Young LE, Blissitt KJ, Bartram DH, Clutton RE, Molony V, Jones RS.In order to determine if transoesophageal Doppler echocardiography could be used to estimate cardiac output in anaesthetized horses, we have compared the technique with estimations of cardiac output by thermodilution in eight healthy adult thoroughbreds. Measurements of aortic blood flow velocity were made by high pulse repetition frequency (HPRF) and continuous wave (CW) Doppler echocardiography from a 3.5-MHz transoesophageal probe. Cardiac output was increased during the study by administration of dobutamine, providing a range of cardiac output measurements by thermodilution from 15.0 to 64...
Klein L, Sherman J.Central venous pressure (cvp) was recorded in horses before and after tranquilization and during halothane-maintained anesthesia in lateral or dorsal recumbency. The cvp was significantly decreased after administration of acetylpromazine, when compared with base line measurements and measurements taken after xylazine administration. After induction of anesthesia, cvp increased with time for 75 minutes, and values in lateral recumbency were significantly higher than those in dorsal recumbency.
Dunkle NJ, Bottoms GD, Fessler JF, Knox K, Roesel OF.A study was conducted to determine whether body fluids undergo a net shift from one compartment to another during endotoxin-induced shock in the pony, and whether flunixin meglumine alters these endotoxin-induced changes in the volumes of body fluid compartments. Total blood, RBC, and plasma volumes were determined, using 51Cr-labeled RBC and PCV that were corrected for trapped plasma. Total body water was measured by distribution of 3HOH. Arterial blood pressure was measured directly, using a blood pressure transducer. Treatment (flunixin meglumine, 1.1 mg/kg of body weight) was given to 6 of...
Geor RJ.Acute renal failure (ARF) in horses is usually prerenal or renal in origin and is most often caused by hemodynamic or nephrotoxic insults. The clinical management of patients that have ARF is largely supportive, including correction of fluid deficits and electrolyte and acid-base disturbances and treatment and reversal of the underlying cause. Use of dopamine and mannitol to promote renal blood flow and urine output is no longer recommended.
Ferreira JC, Gastal EL, Ginther OJ.Transrectal color and power Doppler ultrasonography was used to study uterine blood flow and perfusion in mares with and without uterine cysts. Vascular perfusion of the uterus and blood flow velocities, vascular perfusion, diameter, circumference, and area of a cross section of the mesometrial attachment were evaluated. To study the effect of internal cysts, two matched groups (cystic and control, n=21 mares/group) were used. Uterine vascular perfusion in mares with cysts was less (P<0.0001) in the cystic than the noncystic region and less (P<0.0009) than that for controls. Mares with c...
Marntell S, Nyman G, Funkquist P.The principal aim of this study was to evaluate dissociative anaesthesia for castration of colts during field conditions. Three dissociative anaesthetic protocols were evaluated during castration of colts in an animal hospital. The protocol considered to be the most suitable was thereafter evaluated during castration of colts under field conditions. Respiratory and haemodynamic parameters and the response to surgery were determined during anaesthesia. All horses breathed air spontaneously during anaesthesia. Under hospital conditions 26 colts were randomised to receive one of three anaesthetic...
Snyder JR, Pascoe JR, Holland M, Kurpershoek CJ.Measurements of jejunal, ileal, and large colon (pelvic flexure) surface O2 tension (PSO2) were made in halothane-anesthetized horses with a nonheated miniature oxygen polarographic electrode. Assisted ventilation with 100% O2 was used to maintain PaCO2 tension at 50 +/- 8 mm of Hg while mean arterial blood pressure was maintained greater than or equal to 70 mm of Hg. Mean +/- SD PSO2 for the intestinal segments were: jejunum (horses 1 to 4), 71 +/- 20 mm of Hg; ileum (horses 1 to 4), 61 +/- 8 mm of Hg; and pelvic flexure of the large colon (horses 1 to 10), 55 +/- 13 mm of Hg. The response of...
Skarda RT, Muir WW.To examine effects of 0.25 mg of xylazine/kg of body weight diluted to a total volume of 6 ml/450 kg with sterile 0.9% NaCl, administered into the epidural space of the sacrococcygeal joint on perineal analgesia, sedation, ataxia, and respiratory and cardiovascular function in standing mares. Methods: Randomized, blinded study, using xylazine (treatment) and 0.9% NaCl (controls). At least 2 weeks elapsed between the treatments. Methods: Eight healthy mares. Methods: Blood samples were drawn. Systemic hemodynamics were determined, including cardiac output and pulmonary arterial, systemic arteri...
Skarda RT, Tejwani GA, Muir WW.To determine cutaneous analgesia, hemodynamic and respiratory effects, and beta-endorphin concentration in spinal fluid and plasma of horses after acupuncture and electroacupuncture (EA). Methods: 8 healthy 10- to 20-year-old mares that weighed between 470 and 600 kg. Methods: Each horse received 2 hours of acupuncture and 2 hours of PAES at acupoints Bladder 18, 23, 25, and 28 on both sides of the vertebral column as well as sham needle placement (control treatment). Each treatment was administered in a random order. At least 7 days elapsed between treatments. Nociceptive cutaneous pain thres...
Freeman SL, Bowen IM, Bettschart-Wolfensberger R, Alibhai HI, England GC.The cardiovascular effects of romifidine, an alpha-2 adrenoreceptor agonist, were investigated in six horses using two doses (80 and 120 microg kg(-1)) in a cross-over study design. Cardiac index and mixed venous oxygenation were significantly decreased at 15 and 30 minutes after both doses of romifidine. Systemic vascular resistance was significantly increased with romifidine (120 microg kg(-1)). Arterial blood pressure increased initially and then gradually decreased; the doses of decrease was significant at 90 and 120 minutes with romifidine 80 and 120 microg kg(-1). There were minimal diff...
Manohar M, Bisgard GE, Bullard V, Rankin JH.To examine the effects of right ventricular (RV) hypertrophy on regional myocardial blood flow and coronary vascular reserve, hemodynamics and myocardial blood flow (15-micrometers radio-nuclide-labeled microspheres) were studied in 12 unanesthetized adult ponies before and during intravenous isoproterenol HCl infusion (1 microgram.kg-1.min-1). Six ponies served as controls, whereas in each of the others the main pulmonary artery (PA) had been banded 35-90 days prior to the study. Marked RV hypertrophy was present in PA-banded animals. In these ponies, there was a significant increase in RV sy...
Boutet BG, Gordon SG, De Solis CN, Lepiz MA, Saunders AB, Wesselowski S.Intracardiac echocardiography (ICE) is a method of obtaining echocardiographic images with a steerable ultrasound catheter placed within the heart via a venous or arterial approach. The objectives of this study were to assess the feasibility of a 5-10 MHz, 8 French, 90 cm ICE catheter to evaluate cardiac structures and function in standing, sedated horses, and describe standard views in this species. Methods: Ten apparently healthy horses weighing 458.1-618.2 kg from a university teaching herd. Methods: Each horse had a physical examination, transthoracic echocardiography, and ICE performe...
Wood SC, Fedde MR.Splenic contraction in racing horses increases the hematocrit (hct), thereby increasing blood viscosity. We tested as to whether racing also affects the elastic properties of blood. Mares and geldings were studied for thus purpose. After racing, there was: (i) an increased erythrocyte count independent of gender and race distance (0.32 to 1.7 km): (ii) an increased mean erythrocyte volume in both sexes; (iii) an increased heterogeneity of RBC size in both sexes; (iv) an increased plasma fibrinogen concentration and erythrocyte sedimentation rate in both sexes; and (v) an increased elastic yiel...
Gingold BM, Killos MB, Griffith E, Posner L.Maintaining adequate muscle tissue oxygenation is of paramount importance during equine general anesthesia. The objectives of this study were to assess the feasibility, reliability and repeatability of near-infrared spectroscopy (NIRS) muscle oximetry using the Inspectra m650 in conscious healthy adult horses. Methods: Prospective, observational study. Methods: A group of 30 healthy client-owned adult horses admitted to the equine hospital between July 2017 and July 2018. Methods: The probe of an Inspectra m650 NIRS tissue oximeter was placed on the hairless surface of five muscle sites (omotr...
Orr JA, Bisgard GE, Forster HV, Buss DD, Dempsey JA, Will JA.Unanesthetized adult female ponies were studied near sea level (250 m) and during sojourns to 3400 m (N=6) and 4300 m (N=7) altitude. The pH, PCO2, and PO2 of arterial blood and pH and PCO2 of cerebrospinal fluid (CSF) were measured under conditions of acute (1 hr) and chronic (1-45 days) hypoxia. Cerebrospinal fluid was sampled from the cisterna magna of the awake pony and arterial blood withdrawn from an indwelling arterial catheter. In both groups of animals, PaCO2 decreased slightly after 1 hr of hypoxia (delta PaCO2= - 0.6 mm Hg at 3400 m; - 3.9 mm Hg at 4300 m), decreased further after 1...
Hopster K, Ambrisko TD, Stahl J, Schramel JP, Kästner SB.Previous studies showed an influence of xylazine on the LiDCO sensor in vitro and in standing horses, but did not prove that this interaction caused error in LiDCO measurements. Therefore, agreement of cardiac output (CO) measurements by LiDCO and bolus-thermodilution (BTD) was determined in horses receiving xylazine infusions. Methods: Prospective, experimental study. Methods: Eight Warmblood horses. Methods: All horses were premedicated with xylazine. Anaesthesia was induced with midazolam and ketamine and was maintained with isoflurane in oxygen. During six hours of anaesthesia CO measureme...
