Function In Horses Research Articles

0817 Optimizing nutrition to improve immune function in horses

0817 Optimizing nutrition to improve immune function in horses

The cardiovascular status of isoflurane-anaesthetized horses with and without dexmedetomidine constant rate infusion evaluated at equivalent depths of anaesthesia

ObjectiveTo compare cardiac index and oxygen extraction at equivalent depths of anaesthesia between isoflurane-anaesthetized horses and horses anesthetized with isoflurane and dexmedetomidine CRI. Study designSequential, blinded, randomized, balanced, crossover study. AnimalsEight horses weighing a mean ± standard deviation of 478 ± 58 kg. MethodsHorses were premedicated with 0.03 mg kg−1 acepromazine intramuscularly (IM) and 8 μg kg−1 dexmedetomidine intravenously (IV). Anaesthesia was induced with 2.5 mg kg−1 ketamine and 0.1 mg kg−1 midazolam IV and maintained with isoflurane in oxygen and air. Horses were mechanically ventilated. Fractional concentration of end-tidal isoflurane (Fe’Iso) was stabilized at 1.7% with a CRI of 0.9% NaCl (IsoNaCl), or at 1.1% with 1.75 μg kg−1 hour−1 dexmedetomidine (IsoDex). Mean arterial blood pressure was maintained above 60 mmHg by dobutamine infusion. Following nociceptive electrical stimulation, Fe’Iso was stabilized at a 0.1% lower concentration and nociceptive stimulation was repeated. This procedure was continued until the horse moved. Fe’Iso values prior to the concentration at which movement occurred were considered to indicate equivalent depths of anaesthesia between treatments. Cardiac index and oxygen extraction were compared at equivalent depths of anaesthesia using a paired Student’s t-test. ResultsCardiac index differed between IsoNaCl at 61 ± 12 mL kg−1 minute−1 and IsoDex at 48 ± 10 mL kg−1 minute−1 (p = 0.047). In addition, oxygen extraction differed between IsoNaCl at 3.4 ± 0.8 mL kg−1 minute−1 and IsoDex at 4.5 ± 0.5 mL kg−1 minute−1 (p = 0.0042). Two horses receiving IsoNaCl were administered dobutamine at equivalent depths of anaesthesia (7.0 and 28.8 μg kg−1 hour−1, respectively). Conclusions and clinical relevanceCardiovascular function in horses receiving isoflurane and 1.75 μg kg−1 minute−1 dexmedetomidine is more compromised than in horses receiving a higher concentration of isoflurane and 0.9% NaCl CRI.

Echocardiographic Assessment of Left Atrial Size and Function in Warmblood Horses: Reference Intervals, Allometric Scaling, and Agreement of Different Echocardiographic Variables.

BackgroundEchocardiographic assessment of left atrial (LA) size and function in horses is not standardized.ObjectivesThe aim of this study was to establish reference intervals for echocardiographic indices of LA size and function in Warmblood horses and to provide proof of concept for allometric scaling of variables and for the clinical use of area‐based indices.AnimalsThirty‐one healthy Warmblood horses and 91 Warmblood horses with a primary diagnosis of mitral regurgitation (MR) or aortic regurgitation (AR).MethodsRetrospective study. Echocardiographic indices of LA size and function were measured and scaled to body weight (BWT). Reference intervals were calculated, the influence of BWT, age, and valvular regurgitation on LA size and function was investigated and agreement between different measurements of LA size was assessed.ResultsAllometric scaling of variables of LA size allowed for correction of differences in BWT. Indices of LA size documented LA enlargement with moderate and severe MR and AR, whereas most indices of LA mechanical function were not significantly altered by valvular regurgitation. Different indices of LA size were in fair to good agreement but still lead to discordant conclusions with regard to assessment of LA enlargement in individual horses.Conclusions and Clinical ImportanceAllometric scaling of echocardiographic variables of LA size is advised to correct for differences in BWT among Warmblood horses. Assessment of LA dimensions should be based on an integrative approach combining subjective evaluation and assessment of multiple measurements, including area‐based variables. The clinical relevance of indices of LA mechanical function remains unclear when used in horses with mitral or aortic regurgitation.

Conformation Traits and Gaits in the Icelandic Horse are Associated with Genetic Variants in Myostatin (MSTN).

Many genes are known to have an influence on conformation and performance traits; however, the role of one gene, Myostatin (MSTN), has been highlighted in recent studies on horses. Myostatin acts as a repressor in the development and regulation of differentiation and proliferative growth of skeletal muscle. Several studies have examined the link between MSTN, conformation, and performance in racing breeds, but no studies have investigated the relationship in Icelandic horses. Icelandic horses, a highly unique breed, are known both for their robust and compact conformation as well as their additional gaits tölt and pace. Three SNPs (g.65868604G>T [PR8604], g.66493737C>T [PR3737], and g.66495826A>G [PR5826]) flanking or within equine MSTN were genotyped in 195 Icelandic horses. The SNPs and haplotypes were analyzed for association with official estimated breeding values (EBV) for conformation traits (n = 11) and gaits (n = 5). The EBV for neck, withers, and shoulders was significantly associated with both PR8604 and PR3737 (P < 0.05). PR8604 was also associated with EBV for total conformation (P = 0.05). These associations were all supported by the haplotype analysis. However, while SNP PR5826 showed a significant association with EBVs for leg stance and hooves (P < 0.05), haplotype analyses for these traits failed to fully support these associations. This study demonstrates the possible role of MSTN on both the form and function of horses from non-racing breeds. Further analysis of Icelandic horses as well as other non-racing breeds would be beneficial and likely help to completely understand the influence of MSTN on conformation and performance in horses.

Hematological changes and resistance of erythrocytes of crimean horses in response to 32 km races

Aim. The aim of the present study was to investigate the alterations of some hematological parameters (hae- matocrit (HCT), haemoglobin concentration (HGB), the count of red blood cells (RBC), mean corpuscular hemoglobin concentration (MCHC), mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), red cell distribution width (RDW), as well as resistance of erythrocytes to urea and hydrogen peroxide in horses after 32 km endurance race. Methods. Seven horses from Crimea region (Bilohirsk, Crimean region) were involved in this study. Haematological parameters (haematocrit (HCT), haemoglobin concentration (HGB), the count of red blood cells (RBC), mean corpuscular hemoglobin concentration (MCHC), mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), red cell distribution width (RDW)) were determined with use of hematological and biochemical methods. Blood samples have been investigated by centrifugation at 3,000 g for 15 min. The peroxide and osmotic resistance of erythrocytes were determined spectrophoto- metrically at 540 nm by monitoring the rate of erythrocytes disintegration by hydrogen peroxide. Endurance h orses used in this study are trained and conditioned to perform over long distances at moderate speeds. The prolonged exercises were used in endurance race. The walk about 3 km/h for 20 min, the trot about 7 km/h for 15 min, and the canter about 5 km/h for 15 min) and the walk about 1 km were repeated for 1 h (phase I); rest in an outdoor paddock without access to water for 30 min. And phase II: the walk about 3 km/h for 20 min, the trot about 7 km/h for 15 min, and the canter about 5 km/h for 15 min) and the walk about 1 km was repeated for 1 h. Results. The results of the present study showed that adequate endurance race of low intensity could im- prove oxygen-dependent respiratory function in horses from Crimean region. Furthermore, the non-signifi cant increase of red blood cells indices in endurance horses indicate about good athletic level after 32 km endur- ance ride. Statistically signifi cant differences in the percentage of hemolyzed erythrocytes between pre- and post-ride period were observed and thereby signifying an oxidative stress-dependent impairment of erythrocyte stability. Conclusions. The haematological changes caused by various physical efforts refl ect changes in the functions of different systems and can be used for health control and diagnosis of diseases. It also allow the evaluating the level of sport performance, the accuracy of training, and physiological condition of horses.

Effects of a long-day light programme on the motility and membrane integrity of cooled-stored and cyropreserved semen in Shetland pony stallions

Increasing day length in spring stimulates reproductive functions in horses. In this study, we have analysed the effect of artificial long days on the quality of cooled-stored and cryopreserved semen in Shetland stallions. Stallions of the treatment group (AL, n=8) were exposed to 16h light and 8h darkness from 15th December to 20th March while control stallions (CON, n=7) were kept under natural photoperiod. Semen was collected once weekly and processed for cooled-storage and cryopreservation once per month. Total and progressive motility and percentage of membrane intact spermatozoa were analysed at 24, 48 and 72h of cooled-storage and after freezing-thawing, respectively. Total and progressive motility and membrane integrity decreased during cooled-storage for 72h in each month and both groups (p<0.001). All these parameters were lower in CON versus AL stallions (p<0.05) and the decrease was more pronounced in group CON (storage time x group p<0.05). Differences between groups decreased throughout the observation period from January (p<0.05 between groups) to July (e.g. total motility after 72h of cooled-storage in January for group AL 80±3 and group CON 49±12%, respective values in July, 83±2 and 72±6%). Neither total and progressive motility nor percentage of membrane-intact and morphologically defect spermatozoa in frozen–thawed semen differed between groups and months. In conclusion, motility of cooled-stored semen was reduced in January and increased in stallions kept under a long day light programme for at least 30 days.

Neurologic Deficits Including Auditory Loss and Recovery of Function in Horses with Temporohyoid Osteoarthropathy.

BackgroundAuditory loss is a common deficit in horses with temporohyoid osteoarthropathy (THO), however, recovery of function is unknown.Hypothesis/ObjectivesTo investigate neurologic function with emphasis in audition in horses with THO after treatment. To describe anatomical alterations of the petrous temporal bone that might result in auditory loss.AnimalsTwenty‐four horses with a clinical diagnosis of THO.MethodsProspective study. A brainstem auditory evoked response (BAER) study was done as part of the criteria for inclusion in horses with a clinical diagnosis of THO from the years of 2005 to 2014. Physical and neurologic status and BAER findings were recorded. Brainstem auditory evoked response variables were compared by using Wilcoxon sign test. Fisher's exact test was also used. Significance was set at P < 0.05.ResultsThe most common signs included auditory loss (100% of horses), vestibular and facial nerve dysfunction (83%), and exposure ulcerative keratitis (71%). Concurrent left laryngeal hemiparesis was observed in 61% of horses through endoscopy. Auditory dysfunction was bilateral in 50% of the cases (complete and partial), and unilateral affecting more commonly the right ear (R = 8, L = 4). Short‐ and long‐term follow‐up revealed persistent auditory loss in all horses based on abnormal response to sound, and further confirmed through a BAER in 8 horses.Conclusions and Clinical ImportanceAuditory dysfunction appears to be a permanent neurologic deficit in horses diagnosed with THO despite overall neurologic improvement.

Evaluation of platelet function in horses undergoing colic surgery using the PFA-100 platelet function analyser

Acute colic in horses, especially presentations requiring surgical correction, such as large colon volvulus, very often involves defective or excess platelet activation. The PFA-100 is a new point-of-care analyser that evaluates platelet function by measuring closure time (CT) in the whole blood of healthy horses in a stan - dardised manner. However, there are no reports on platelet function in horses with colic measured by the PFA-100. The aim of the present study was to investigate platelet function in a group of horses suffering ascending colon displacement (ACD) and who underwent surgery compared to a group of control (C) horses. Thirty ACD cases and twenty untreated clinically healthy control horses were included. Blood samples were collected from the ACD horses prior to and 24, 48 and 72 h after laparotomy. Red blood cell count (RBC), haematocrit (HCT), hae - moglobin (Hb) concentration, white blood cell count (WBC), total plasma protein (TP) concentration, platelet count (PLT), platelet volume (MPV) and ADP closure time (CT-ADP) were measured. CT was determined on a PFA-100® device using collagen/ADP cartridges. There were no significant differences in RBC, PLT and MPV between C and ACD horses pre-operatively. Reduced PLT was observed in the post-operative period. The mean CT-ADP of C horses was 96.43 ± 12.53 and 91.43 ± 2.51 seconds in the ACD group prior to surgery. CT-ADP was changed after surgery whereby CT-ADP time was more than doubled. We conclude that the PFA-100 ® can be used to detect platelet function defects in horses.

Design and Optimization of a Novel Method for Assessment of the Motor Function of the Spinal Cord by Multipulse Transcranial Electrical Stimulation in Horses

Compared to transcranial magnetic stimulation (TMS), transcranial electrical stimulation (TES) more specifically assesses the motor function of the spinal cord and excludes reproducibility errors from coil repositioning. Objective: to assess the applicability of multipulse TES in horses and retrieve optimal TES parameters to elicit muscular motor-evoked potentials in the m. extensor carpi radialis (ECR) and the m. tibialis cranialis (TC) in a scouting study. This is a prospective observational study in five healthy horses based on TES as a novel alternative to TMS to assess the motor function of the spinal cord for clinical diagnosis in search for optimal settings of stimulation parameters. After sedation, a subcutaneous anesthetic ring block was placed on the forehead around bilateral TES needle electrodes. In each step of a specific parameter optimizing protocol, one parameter was varied while leaving others at default values: TES motor threshold +30 V, n = 3 pulses/train (ppt), interpulse interval (ipi) = 1.3 ms, and 0.1 ms/phase biphasic pulses. Variable parameters were TES voltage (0–200 V), n (1–5 ppt), and ipi (0.5–4.5 ms). A multipulse facilitation factor (MPFF) quantified the motor neuron recruitment gain by multipulse stimulation. Mean latency times, MPFF, optimal ipi, and n for the ECR muscles were, respectively, 18.6 (1.26) (mean[SD]) ms, 7.1 (3.4), 1.25 (0.21) ms, 3.0 (1.4) ppt (left) and 18.4 (1.10) ms, 4.3 (1.4), 1.9 (0.7) ms, 3.5 (1.3) ppt (right) and for the TC muscles, respectively, 34.5 (0.96) ms, 5.3 (2.4), 1.2 (0.28) ms, 3.3 (1.0) ppt (left) and 33.4 (1.52) ms, 17.5 (21.2), 1.3 (0,17) ms, 3.3 (0.5) ppt (right). Optimal multipulse TES parameters were n = 3 ppt and ipi = 1.2 to 1.3 ms. Multipulse TES is well tolerated and an attractive alternative to TMS. Transcranial electrical stimulation is expected to be a more robust technique than TMS for evaluation of spinal motor function in horses. A better reproducibility of repeated stimulations is expected due to fixed electrodes, and a reduced sensitivity to hyperpolarizing effects of sedatives is expected.

Glucocorticoid receptor density and binding affinity in healthy horses and horses with systemic inflammatory response syndrome.

BackgroundDysregulation of the hypothalamic‐pituitary‐adrenal (HPA) axis occurs in horses with systemic inflammatory response syndrome (SIRS). Peripheral resistance to glucocorticoids has not been investigated in horses.ObjectiveTo determine if glucocorticoid receptor (GR) function in horses can be measured using flow cytometry, and to use this information to evaluate HPA axis dynamics.AnimalsEleven healthy adult horses in parts 1 and 2. Ten horses with SIRS and 10 age and sex matched controls in part 3.MethodsFlow cytometry was used to evaluate GR density and binding affinity (BA) in 3 healthy horses in part 1. In part 2, exogenous ACTH was administered to eight healthy horses. Their cortisol response and GR properties were measured. In part 3, CBC, serum biochemistry, cortisol and ACTH, and GR properties were compared between controls without SIRS (n = 10) and horses with SIRS (n = 10), and between survivors and nonsurvivors (n = 4 and n = 6 respectively).ResultsFlow cytometry can be used to measure GR properties in equine PBMCs. No correlation was observed between plasma cortisol concentration and GR density or BA in healthy horses (r = −0.145, P = .428 and r = 0.046, P = .802 respectively). Nonsurvivors with SIRS had significantly decreased GR BA (P = .008). Horses with triglyceride concentration > 28.5 mg/dL had increased odds of nonsurvival (OR=117; 95% CI, 1.94–7,060). GR BA <35.79% was associated with nonsurvival (OR = 30.33; 95% CI, 0.96–960.5).Conclusions and Clinical ImportanceTissue resistance to glucocorticoids contributes to HPA axis dysfunction in adult horses with SIRS. These horses might benefit from treatment with exogenous glucocorticoids.

Use of Laryngeal Computed Tomography for Noninvasive Assessment of Laryngeal Function in Horses with Recurrent Laryngeal Neuropathy

Reasons for performing studyRecurrent laryngeal neuropathy (RLN) is a common equine distal axonopathy associated with neurogenic atrophy of intrinsic laryngeal muscles (particularly the left) causing laryngeal paresis and poor performance. An objective, reliable method of assessing changes in structure that correlates with laryngeal muscle function in vivo is necessary to determine response to novel treatments, including functional electrical stimulation. This study aimed to determine whether laryngeal muscle and nerve morphology (determined by CT and histopathology) correlated with laryngeal function.Study designProspective cohort study.MethodsResting (grades 1–4) and exercising (grades A–C) laryngeal function was graded in adult Thoroughbred horses. Standing CT of the larynx was performed to compare volume, cross‐sectional area (XSA) and tissue density between left and right cricoarytenoideus dorsalis (CAD) muscles in 22 horses. CAD muscles and recurrent laryngeal nerves were collected in a subgroup of 10 horses and analysed for fibrosis, fat infiltration and nerve fibre density (axons/μm2).ResultsHorses with grade C RLN on exercising endoscopy had significantly (P&lt;0.005) smaller left CAD muscles and reduced nerve fibre density than horses with grades A or B. Horses with grade 4 RLN on resting endoscopy had significantly (P&lt;0.005) smaller left CAD muscles than horses with grades 1 or 2. Left CAD muscles had significantly more collagen than the right in horses with grade C RLN. CT measurements of the CAD muscles were significantly associated with % collagen/fat and nerve fibre density (P&lt;0.05).ConclusionsLaryngeal CT results correlate with laryngeal function at rest and exercise in the horse and provide a noninvasive method of monitoring changes in CAD morphology in response to novel treatments. CAD CT appearance is dependent on % collagen and fat in the muscle and is associated with nerve fibre density.Ethical animal research: Horses destined for euthanasia were recruited for this study with approval of the Institutional Ethical Committee and under UK Home Office Licence. Sources of funding: Med‐El Elektro‐medizinische Geräte GmbH, Innsbruck, Austria. Competing interests: None.

Intrauterine growth enhancement and restriction are associated with alterations in term placenta morphology, morphometry and function in horses

Intrauterine growth enhancement and restriction are associated with alterations in term placenta morphology, morphometry and function in horses

Effects of meloxicam and phenylbutazone on renal responses to furosemide, dobutamine, and exercise in horses.

To compare the effects of 2 NSAIDs (phenylbutazone and meloxicam) on renal function in horses. 9 Thoroughbred or Standardbred mares (mean ± SD age, 5.22 ± 1.09 years [range, 2 to 12 years]; mean body weight, 470 ± 25 kg [range, 442 to 510 kg]). A randomized blinded placebo-controlled crossover study was conducted to examine the effects of treatment with phenylbutazone, meloxicam, or a placebo (control solution) on renal responses to the administration of furosemide, dobutamine, and exercise (15 minutes at 60% of maximum heart rate). Renal function was assessed by use of bilateral ureteral catheterization for simultaneous determination of creatinine clearance, sodium excretion, and urine flow rate. Both phenylbutazone and meloxicam attenuated diuresis and natriuresis and reduced glomerular filtration rate, compared with results for the control solution, when horses were treated with furosemide. Mean arterial blood pressure, urine flow rate, and glomerular filtration rate were increased during or after (or both) dobutamine infusion. Both NSAIDs reduced urine flow rate and sodium excretion associated with dobutamine infusion and exercise but had no effect on glomerular filtration rate. Responses to meloxicam, a cyclooxygenase (COX)-2 preferential agent, appeared comparable to those detected after phenylbutazone treatment, which suggested that COX-2 was the mediator of prostanoid-induced changes to renal function in horses and indicated that COX-2-preferential agents would be likely to have adverse renal effects similar to those for nonselective COX inhibitors in volume-depleted horses.

Brainstem auditory evoked responses in an equine patient population: part I--adult horses.

BackgroundBrainstem auditory evoked response has been an underused diagnostic modality in horses as evidenced by few reports on the subject.Hypothesis/ObjectivesTo describe BAER findings, common clinical signs, and causes of hearing loss in adult horses.AnimalsStudy group, 76 horses; control group, 8 horses.MethodsRetrospective. BAER records from the Clinical Neurophysiology Laboratory were reviewed from the years of 1982 to 2013. Peak latencies, amplitudes, and interpeak intervals were measured when visible. Horses were grouped under disease categories. Descriptive statistics and a posthoc Bonferroni test were performed.ResultsFifty‐seven of 76 horses had BAER deficits. There was no breed or sex predisposition, with the exception of American Paint horses diagnosed with congenital sensorineural deafness. Eighty‐six percent (n = 49/57) of the horses were younger than 16 years of age. The most common causes of BAER abnormalities were temporohyoid osteoarthropathy (THO, n = 20/20; abnormalities/total), congenital sensorineural deafness in Paint horses (17/17), multifocal brain disease (13/16), and otitis media/interna (4/4). Auditory loss was bilateral and unilateral in 74% (n = 42/57) and 26% (n = 15/57) of the horses, respectively. The most common causes of bilateral auditory loss were sensorineural deafness, THO, and multifocal brain disease whereas THO and otitis were the most common causes of unilateral deficits.Conclusions and Clinical ImportanceAuditory deficits should be investigated in horses with altered behavior, THO, multifocal brain disease, otitis, and in horses with certain coat and eye color patterns. BAER testing is an objective and noninvasive diagnostic modality to assess auditory function in horses.

Prognostic value of echocardiographic and Doppler parameters in horses admitted for colic complicated by systemic inflammatory response syndrome

To assess the prognostic value of echocardiographic parameters of left ventricular (LV) function in horses with systemic inflammatory response syndrome (SIRS). Prospective observational study. Veterinary teaching hospital. Forty-one horses admitted for colic with clinical evidence of SIRS. All horses underwent Doppler echocardiographic examination on admission. LV echocardiographic parameters, including pulsed-wave tissue Doppler imaging parameters, were compared between nonsurvivors (n = 29) and horses that survived to discharge (n = 12). With comparable heart rate and LV preload estimate, LV stroke volume index, the velocity time integral, deceleration time, ejection time of Doppler aortic flow, and peak early diastolic myocardial velocity were lower in the nonsurviving than in the surviving horses, while pre-ejection period to ejection time ratio (PEP/ET) of Doppler aortic flow and the peak early diastolic filling velocity to peak early diastolic myocardial velocity ratio (E/Em) were higher (P < 0.05). A cut-off value of 0.26 for PEP/ET predicted mortality with 100% sensitivity and 42% specificity (area under the receiver operating characteristic curve: 0.71), whereas a cut-off value of 2.67 for E/Em predicted mortality with 100% sensitivity and 83% specificity (area under the receiver operating characteristic curve: 0.89). Echocardiography may provide prognostic information in colic horses with clinical evidence of SIRS. Especially, PEP/ET and E/Em could be useful markers of systolic and diastolic dysfunction, respectively, to detect horses with a high risk of death requiring more intensive cardiovascular monitoring as it has been reported in human patients with septic shock.

Intrauterine growth restriction is associated with strong alterations in placental structure and function in horses

In equids, placentation is diffuse and the nutrient supply to the fetus is determined by uterine size, which is correlated to maternal size and parity. That the size of the mare affects fetal development has previously been shown by embryo transfer (ET) between Ponies and Thoroughbreds [Allen WR, et al; Reproduction 2002;123:445-53.]. We enhanced or restricted fetal growth through ET using Pony (P), Saddlebred (S) and Draft (D) horses and investigated placental morphology, histology and function at term. Control pregnancies of P-P (n1⁄421), S-S (n1⁄428) and D-D (n1⁄48) were obtained by artificial insemination. Enhanced and restricted pregnancies were obtained by transferring P (P-D, n1⁄46) and S embryos (S-D, n1⁄48) into D mares or S embryos into P mares (S-P, n1⁄46), respectively. Placental weight and gross surface area were recorded at delivery. Samples were collected for stereology (quantitative histology) and RT-qPCR analysis of expression of genes involved in placental growth, vascularization and nutrient transport. Statistical analysis of data was performed by Kruskal-Wallis with Dunn’s posthoc test. Data are expressed as means SEM. Mean placental weight and gross surface area were higher in S-S and in D-D compared to P-P (p<0.05) whereas S-S and D-D were not different (4.6 0.17kg and 8046 176.1cm2 in S-S versus 4.9 0.41kg and 9229 596.2cm2 in D-D versus 2.5 0.14kg and 2940 111.7cm2 in P-P for placental weight and surface, respectively). No histological changes were observed among controls, but most genes had their expression decreased in P-P compared to S-S and D-D. P-D foals had a

Tissue Doppler Imaging and Two-dimensional Speckle Tracking of Left Ventricular Function in Horses Affected with Recurrent Airway Obstruction before and after Clenbuterol Treatment

Cardiac effects of the β2-adrenergic agent clenbuterol have been the focus of many studies, but effects on myocardial velocities and myocardial deformation parameters have not yet been evaluated in horses affected with recurrent airway obstruction (RAO) using tissue Doppler imaging (TDI) and two-dimensional speckle tracking (2DST). In our study, 7 horses affected by RAO were treated over 14 days with clenbuterol, 0.8 μg/kg every 12 hours. Standard echocardiographic, TDI (pulsed wave and color TDI), and 2DST examinations were performed before and after the treatment period. Myocardial function was recorded in the right parasternal short-axis view. Percent of fractional shortening and two-dimensional echocardiography (2DE) measurements did not show any significant changes after 2 weeks of treatment. Early diastolic velocity, E, increased significantly after clenbuterol in the left ventricular free wall (LVFW; P = .001). The E/late diastolic velocity (A) quotient (P = .003) and the isovolumetric contractility (P = .035) also increased significantly after treatment. Time parameters, particularly the time interval between the Q-wave in the echocardiograph and atrial release, the time of diastole and Tei index (parameter of global ventricular function), decreased significantly after clenbuterol administration in the LVFW (P = .014/P = .028/P = .015, respectively). The 2DE speckle tracking revealed a significant increase of the early diastolic systolic strain rate (P = .01) in the LVFW after therapy. In conclusion, 2 weeks of treatment with clenbuterol at a dosage of 0.8 μg/kg every 12 hours led to improved cardiac function in severely RAO-affected horses. This could be a sign of myocardial restoration (re-remodeling) after therapy.

In vitro effects of three formulations of hydroxyethyl starch solutions on coagulation and platelet function in horses

To investigate the in vitro effects of 3 hydroxyethyl starch (HES) solutions on viscoelastic coagulation testing and platelet function in horses. Blood samples collected from 7 healthy adult horses. Blood samples were diluted with various crystalloid and HES solutions to approximate the dilution of blood in vivo that occurs with administration of a 10 and 20 mL/kg fluid bolus to a horse (1:8 and 1:4 dilutions, respectively). Diluted samples were analyzed through optical platelet aggregometry, platelet function analysis, thromboelastography, and dynamic viscoelastic coagulometry. Colloid osmotic pressure and concentrations of von Willebrand factor and factor VIII:C were also determined for each sample. For all HES products, at both dilutions, the colloid osmotic pressure was significantly higher than that in the respective carrier solutions. At the 1:4 dilution, nearly all HES solutions resulted in significant alterations in platelet function as measured via the platelet function analyzer and dynamic viscoelastic coagulometer. Significant decreases in platelet aggregation and factor concentrations were also evident. Fewer HES-associated changes were identified at the 1:8 dilutions. Dilution of blood samples with all HES solutions resulted in changes in viscoelastic coagulation and platelet function that did not appear to be attributable to dilution alone. In vivo evaluations are necessary to understand the clinical impact of these in vitro changes.

Long‐term exercising video‐endoscopic examination of the upper airway following laryngoplasty surgery: A prospective cross‐sectional study of 41 horses

To investigate upper respiratory tract function in horses, previously undergoing laryngoplasty (LP), using exercising video-endoscopy. To evaluate arytenoid abduction and stability, diagnose any concurrent upper airway problems, and correlate these with the owners' perception of success. Horses undergoing LP during a 6-year period at one hospital were initially included. Those available for re-examination were exercised for a duration and intensity considered maximal for their discipline using an over-ground endoscope. Resting and exercising laryngeal and pharyngeal videos were analysed blindly. Multivariable analysis was used to test associations between resting and exercising endoscopic variables, and also between endoscopic variables and owner questionnaire findings. Forty-one horses were included and 78% had a form of upper airway collapse at exercise, with 41% having complex forms, despite 93% of owners reporting the surgery to have been beneficial. Horses with poor abduction (grades 4 or 5/5) were 6 times more likely to make respiratory noise compared with those with good (grades 2 or 3/5) abduction (P = 0.020; 95% confidence interval [CI] 1.3-27.0), and those not having a ventriculectomy were 4.9 times more likely to produce respiratory noise post operatively (P = 0.048; 95% CI 1.0-23.9). Palatal dysfunction was observed in 24% of horses at rest, and 56% at exercise, with the diagnosis at rest and exercise significantly associated (P = 0.001). Increasing severity of pharyngeal lymphoid hyperplasia (prevalence 61%) was significantly associated with increasing arytenoid abduction (P = 0.01). Thirty-four per cent of horses had aryepiglottic fold collapse and 22% of horses had vocal fold collapse. Many horses that had previously had LP were diagnosed with upper airway abnormalities, despite the procedure being considered as beneficial by most owners. When investigating cases of ongoing respiratory noise or poor performance following LP, exercising endoscopy must be considered. Continued respiratory noise may be associated with poor arytenoid abduction and not performing concurrent ventriculectomy.

Effects ofN‐Butylscopolammonium Bromide on Lung Function in Horses with Recurrent Airway Obstruction

Equine recurrent airway obstruction (RAO) is characterized by airway inflammation, bronchoconstriction, and increased mucus production in the airways. Anticholinergic drugs like atropine induce bronchodilatation and rapid improvement in lung function. N-butylscopolammonium bromide (NBB) is an anticholinergic drug used to relieve spasmodic colic in horses, but its effect on airway smooth muscle is unknown. To evaluate the effect of NBB on clinical signs and lung function of RAO-affected horses. Nine horses diagnosed with RAO. Double-blind, placebo-controlled, randomized crossover trial. Horses were challenged with moldy hay until a maximum change in transpulmonary pressure (∆P(L) (max) ) > 15 cm H(2) O was achieved. NBB (0.3 mg/kg) or placebo (0.9% saline) was administered IV. Clinical scores and lung function were recorded at baseline and then periodically after treatment administration. Horses were allowed a 6-week washout before administration of opposite treatments. Clinical score at 10 and 30 minutes (8.7 ± 2.8 and 8.7 ± 3.2, respectively) after NBB administration was significantly lower than baseline (10.8 ± 2.4). NBB administration resulted in a significant decrease in ∆P(L) (max) (baseline: 35.1 ± 6.9 cm H(2) O) starting 2 minutes after administration (16.3 ± 6.6 cmH(2) O) with a maximum decline observed at 10 minutes (13.5 ± 7.1 cm H(2) O). ∆P(L) (max) values between 60 and 120 minutes after NBB administration were not different from placebo. N-butylscopolammonium bromide is a potent bronchodilator, reaching maximum effect 10 minutes after intravenous administration. This effect dissipates within 1 hour of drug administration.