Adult Warmblood Horses Research Articles

How important is the familiarity of a human’s voice in teaching horses a novel word?

The aim of the study was to determine whether adult horses can learn to recognise a novel word and how important the familiarity of a human’s voice uttering the taught word is. In the study, 18 adult warmblood horses were the subjects: nine mares and nine geldings. At the beginning, the horses were habituated to voices heard from loudspeakers located near boxes for three days. The horses were listening to two familiar people (A and B) and one unfamiliar person (C) whose voices were recorded in the playback individually. Next, each horse was taught to positively associate a novel word with receiving a titbit for 10 days, 15 times daily: 12 times by the person who uttered the word and 3 times when the word was heard from playback. The same three people were engaged during the teaching. Finally, the horses were tested whether they had learned the word. The word was uttered by one familiar person (A), the initially unfamiliar person (C) and a totally unknown person (D). The voices of these people were played solely from the loudspeaker three times daily. The horses’ response was evaluated by nine kinds of behaviour recorded. The first test with the three people’s voices was repeated for up to five three-day cycles, dependent on manifesting by the horses a minimum number of behaviours per day. Apart from each tested horse, one companion horse remaining in a neighbouring box and taught another word with a titbit was studied to compare the response. The results show that horses perceived differences between single words, and associated a taught word with receiving a titbit. The companion horses did not respond to this word. The responses to familiar or unfamiliar people’s voices were similar. It was concluded that horses are capable of discriminating a taught word and, simultaneously, generalise familiar and unfamiliar human voices uttering the word. These findings show that teaching horses single words is effective. Simultaneously, the results highlight the need to consistently use chosen words when teaching horses.

Morphological evidence of a potential arrhythmogenic substrate in the caudal and cranial vena cava in horses.

Three-dimensional electro-anatomical mapping, previously performed in horses with atrial arrhythmias, has demonstrated the medial region of the caudal vena cava (CaVC), 1-8 cm caudal to the fossa ovalis, as an anatomical predilection site for atrial tachycardia associated with areas of slow conduction and conduction block. Slow conduction has also been recorded in the cranial vena cava (CrVC). To investigate the morphological characteristics of the myocardial sleeves (MS) in the CaVC and CrVC, in order to identify a potential substrate of right sided atrial arrhythmias. Cross sectional. Post-mortem dissection of 37 hearts from adult warmblood horses without known cardiovascular disease. Macroscopic examination of the myocardial distribution, evaluated the MS area, length, width, and shape in the CaVC and the CrVC. At least 2 samples from each vena cava MS were histologically examined using Masson's trichrome staining. Myocardial sleeves into the medial CaVC and into the CrVC were observed in all horses and showed variations in distribution, shape, and size between horses. Their mean ± standard deviation length from the limbus into the CaVC reached 5.7 ± 1.0 cm (maximum 8.3 cm), and from the azygos vein into the CrVC 5.3 ± 1.6 cm (maximum 8.6 cm). Myocardium-free islands were observed in the CaVC and CrVC in 30% and 6% of horses, respectively. Histologically, MS showed a non-uniform myocardial fibre arrangement, with presence of fibroadipose tissue, features known to result in slow conduction and pro-arrhythmia. Study only included horses without history of atrial arrhythmia. Myocardial sleeves are present in both CaVC and CrVC, showing anatomical variations between horses. Tissue characteristics known to favour re-entry were identified indicating that these venae cavae MS are a potential substrate for atrial tachyarrhythmias and a target for treatment by ablation.

CT is a feasible imaging technique for detecting lesions in horses with elbow lameness: A study of 139 elbows in 99 horses

AbstractComputed tomography (CT)is increasingly available in veterinary referral practices; however, published studies describing CT lesions of the equine elbow are currently lacking. In this single‐center, retrospective, observational study, horses undergoing elbow CT at Equitom between July 2015 and October 2018 were reviewed. Subchondral bone sclerosis; resorption of the radius, ulna, and humerus; osteophyte; and enthesophyte lesions were graded. One hundred thirty‐nine elbows of 99 horses (16 with elbow pain and 123 control elbows) were included (median age, 9 years). Osseous cyst‐like lesions (n = 13), only seen in the proximomedial radius and medial humerus, were the most common cause of lameness in horses with elbow pain (n = 16), with significantly higher grades of bone resorption (including osseous cyst‐like lesions) in this group. One elbow had an avulsion fracture of the lateral epicondyle, two others showed signs of osteoarthritis. Significantly higher grades of sclerosis in the proximomedial radius were seen in horses with elbow pain; however, mild to moderate subchondral bone sclerosis was seen in all horses at the medial aspect of the joint. Osteochondral fragmentation lesions of the weight‐bearing surface of the medial radius (2/16 vs 1/123; P = .0025) and intra‐articular gas (4/16 vs 2/123; P < .0001) were significantly more common in horses with elbow pain compared to control horses. Mild linear resorptive subchondral bone lesions were often not clinically relevant (32/123 vs 5/16 in medial humerus; 19/123 vs 2/16 in medial radius). In conclusion, elbow CT is a feasible method for detecting clinically relevant lesions in adult Warmblood horses with elbow pain.

Manganese concentrations in whole blood, plasma and serum of adult warmblood horses from 3 locations in Germany

This study aimed to establish reference intervals for Mn in whole blood, plasma and serum of healthy, adult warmblood horses with known dietary Mn intake and to compare 2 methods of analysis. Between May 2018 and November 2019 a single blood sample was taken from a total of 270 clinically healthy horses (age: 3-25 years) in 3 stud farms. In lithium-heparin (LH) whole blood, LH plasma and serum Mn concentrations were analyzed by means of atomic absorption spectrometry (AAS) and inductively coupled plasma mass spectrometry (ICP-MS). The reference intervals were calculated according to the recommendations of the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) and the Clinical and Laboratory Standards Institute (CLSI) comprising the range between 2.5 and 97.5 percentile of the analyzed Mn concentrations. Concurrent to blood sampling feed samples were taken and analyzed in order to determine the Mn content of the corresponding feeding ration. The horses' whole-blood Mn levels were significantly (p < 0.0001) higher with a median Mn concentration of 12.4 μg/l (reference interval: 4.99-25.1 μg/l [AAS]; 5.99-25.3 μg/l [ICP-MS]) than in the corresponding serum (median: 1.65 μg/l, reference interval: 0.60-3.50 μg/l [AAS]; 1.11-2.96 μg/l [ICP-MS]) or LH plasma (median: 1.35 μg/l, reference interval: 0.22-2.68 μg/l [AAS]; 0.59-2.45 μg/l [ICP-MS]). In the comparison of methods, there were statistically significant differences in the Mn determinations for LH plasma and serum between AAS and ICP-MS, whereas they yielded comparable results for whole blood. Whole blood shows an average of 10-fold higher Mn concentrations than serum or LH plasma. When evaluating blood Mn concentrations, consideration must be granted to the sample material under analysis as well as to which method is employed since relevant differences were found between AAS and ICP-MS in serum and LH plasma.

The contribution of the middle cerebral artery and callosal artery to the vascularisation of the Facies convexa of the brain in horses with reference to the equine-specific cartographic pattern of the neopallium.

The extremely complex surface architecture of the equine brain does not allow a uniform transfer of anatomical data from other mammalian species, e.g., dog or cat. Rather, a special approach is required to elucidate the equine-specific patterns of cerebral vascular ramifications. Therefore, a novel cartographic system was applied. Prior attention was paid to the A. cerebri media (MCA) and to the A. corporis callosi (CA), as they spread over the widest part of the neopallium's Facies convexa (i.e. the lateral and dorsal surface), thus being of particular interest in terms of surgical treatment of trauma of the skull and brain. The brains of 17 adult warmblood horses were studied. The neopallium's Facies convexa was subdivided into 15 sectors clearly delineated by the primary sulci and by related auxiliary lines. The courses and destinations of main branches (= branches of 1st or 2nd order, with a minimum calibre of 0.75 mm) of MCA and CA were topographically analysed by means of superimposed graphical sketches. The MCA had six main branches (numbered in rostrocaudal direction); the CA had seven main branches. The main branches of the MCA spread over the widest part of the Facies convexa, but never reached the rostral pole and the caudal pole of the neopallium. Clearly, the main branches of CA proceeded from the hemisphere's medial side across the Margo dorsalis cerebri, thus supplying rostrodorsal and dorsal sectors of the Facies convexa. The topographical analysis of the vascular ramification patterns (regions of residence) in combination with the cartographic system of sectors of the neopallium respected the equine-specific surface architecture. It highlighted the distinct vascular supply areas and the particular multiple-supply situations especially in sectors presumably related to the equine area motorica.

Non‐surgical manual reduction of indirect inguinal hernias in 89 adult stallions

SummaryBackgroundIndirect inguinal hernia (IIH) is the most commonly reported acquired hernia in adult horses. Outcomes following surgical intervention comprising of immediate ventral midline laparotomy (IVML) and simultaneous castration are well known. The outcome following reduction of IIH utilising a noninvasive manual reduction (MR) technique in a large number of horses has not been previously reported.ObjectivesTo describe a nonsurgical MR technique developed by the authors and to report our long‐term experiences and clinical outcome.Study designRetrospective study.MethodsMedical records of 89 stallions presenting with IIH and treated with MR were reviewed. Extensive patient data was collected, with cases grouped based on outcome of the MR procedure and whether or not laparotomy was performed. Data on short‐ and long‐term outcome was obtained.ResultsManual reduction was successful in 80 of 89 (90%) horses. Fifty of 89 (56%) horses were treated with MR only and without exploratory laparotomy. In total 29 of 89 (33%) horses underwent IVML and 10 of 89 (11%) delayed ventral midline laparotomy (DVML). Resections were performed in 6 of 89 (8%) horses. Concurrent small intestinal volvulus was diagnosed in 8 of 89 (9%) horses. Horses undergoing DVML following a successful MR had the highest mortality rates during hospitalisation (4/10, 40%). Short‐term survival was 92% (82/89). Ipsilateral reoccurrence of IIH post‐hospital discharge was recorded in 7 of 47 (15%) horses. Overall long‐term survival with a median of 12 years was 72% (34/47).Main limitationsThese include the retrospective nature of data collection, lack of standardised pre‐ and post‐MR clinical assessments and a biased Warmblood population.ConclusionsManual reduction appears to be a feasible nonsurgical technique to reduce IIH in adult Warmblood horses, with favourable survival rates. Individual case assessment is crucial, as delayed laparotomy may increase mortality rates. Suspicion of concurrent small intestinal volvulus or devitalised small intestine always warrants immediate laparotomy following MR.

Antinociceptive effects of levomethadone in standing horses sedated with romifidine

ObjectiveTo evaluate the antinociceptive effect of a bolus of intravenous levomethadone administered to horses during romifidine constant rate infusion (CRI). Study designProspective, randomized, masked, crossover experimental study. AnimalsA group of eight adult Warmblood horses (seven geldings, one mare) aged 6.6 ± 4.4 years, weighing 548 ± 52 kg [mean ± standard deviation (SD)]. MethodsLevomethadone 0.1 mg kg–1 or an equivalent volume of saline (control) was administered intravenously to standing horses 60 minutes after starting a romifidine CRI. Blood samples to quantify romifidine and levomethadone plasma concentrations by capillary electrophoresis were collected up to 150 minutes after levomethadone administration. The nociceptive withdrawal reflex threshold (NWRT) was determined continuously using an automated threshold tracking device. Sedation and cardiopulmonary variables were assessed at regular intervals. A pharmacokinetic-pharmacodynamic (PK-PD) model was elaborated. Data are presented as mean ± SD or median (interquartile range, 25%–75%) where appropriate. Differences between groups were considered statistically significant for p < 0.05. ResultsHorses exhibited higher NWRTs after levomethadone administration than after saline (123 ± 9% versus 101 ± 9% relative to baseline, p < 0.05). The PK-PD model identified a contribution of levomethadone to the NWRT increase. Effect size was variable among individuals. No adverse reactions to levomethadone administration were observed. A slight effect of levomethadone on sedation scores was evident for the 60 minutes following its administration. Conclusions and Clinical RelevanceA single injection of levomethadone has the potential to increase the NWRT during romifidine CRI in horses and can be administered in combination with α2-adrencoceptor agonists to enhance antinociception in horses. However, individual variation is marked.

Reference values for 2-dimensional and M-mode echocardiography in Friesian and Warmblood horses.

BackgroundEchocardiographic reference intervals for Friesian horses are poorly described.ObjectivesTo obtain reference intervals for echocardiographic measurements in Friesians and compare these with Warmbloods.AnimalsOne hundred healthy adult Friesians and 100 healthy adult Warmblood horses.MethodsCross‐sectional study. Two‐dimensional and M‐mode echocardiographic images were obtained. Echocardiographic measurements, including size, area, and volumetric measurements of left atrium, left and right ventricle, aorta, and pulmonary artery, were performed. Measurements were compared between the 2 breeds using an independent samples t test with Bonferroni correction for multiple comparisons.ResultsReference ranges for standard echocardiographic measurements in Friesians were obtained. Several left ventricular measurements were significantly smaller in Friesians compared to Warmbloods, such as the left ventricular end‐diastolic volume using the 4‐chamber modified Simpsons' method (99.85% confidence interval for the difference [CI] = −245 to −63). Also the right ventricular end‐diastolic and peak‐systolic internal diameter were smaller in Friesians (99.85% CI = −1.33 to −0.6 and 99.85% CI = −1.54 to −0.76, respectively). Fractional shortening (99.85% CI = 0.61‐6) and ejection fraction (99.85% CI = 0.21‐4.6) were significantly larger. No structural effects of systemic hypertension, such as concentric hypertrophy, were detected.Conclusions and Clinical ImportanceOur study provides reference intervals for echocardiographic measurements in Friesians useful in a clinical setting. In general, the left ventricular dimensions in Friesians were significantly smaller compared to Warmbloods, emphasizing the need for breed‐specific reference intervals.

Scientific abstracts of the 29th Annual Scientific Meeting of the ECVS. The 29th Annual Scientific is cancelled due to COVID-19. Abstracts submitted for presentation at the meeting are published with authors' permission. The only abstracts presented are those of the ECVS Resident's Forum, scheduled as a Virtual Session on Thursday, 2 July 2020.

Introduction: Interpretation of transverse hypoechoic lines seen during ultrasonography of medial menisci is challenging as their cause is not fully understood. The aim of this study was to characterize the normal acoustic anatomy of the medial equine meniscus. Materials and Methods: Ten non-lame adult warmblood horses without anamnestic, clinical, radiographic and ultrasonographic signs of lameness associated to the stifle were euthanized for reasons unrelated to the current study. Prior to death medial femorotibial joints were examined with ultrasound in a coronal plane where the medial collateral ligament adheres to the meniscus. Post mortem photographs of corresponding coronal meniscal sections were made. Hypoechoic areas were labelled on digital ultrasound images and laid over corresponding coronal images of menisci specimen. Correlation of hypoechoic regions with structural elements of the menisci was evaluated. Results: On most ultrasound images 2-3 larger, wedge or club-shaped hypoechoic regions were detected distally in the meniscus, increasing in width from medial to lateral. Their medial, narrow origin mostly correlated to prominent T-shaped junctions between the fibrous meniscal capsule and radially orientated tie-fibers formed by loose connective tissue. More laterally anechoic areas became wider than the tie-fibers and did not correlate to their shape. Discussion/Conclusion: Direct comparisons between normal anatomic structures of equine menisci and corresponding ultrasound images have not been made to date. Anechoic linear areas in normal menisci interpreted as artifacts are potentially caused by refraction of ultrasound at the interface between meniscal capsule and radially orientated tie-fibers. Histology is essential to further characterize causative structures.

Effects of feeding alfalfa hay in comparison to meadow hay on the gastric mucosa in adult Warmblood horses

Effects of feeding alfalfa hay in comparison to meadow hay on the gastric mucosa in adult Warmblood horses

Aortic, common carotid and external iliac artery arterial wall stiffness parameters in horses: Inter-day and inter-observer and intra-observer measurement variability.

In human medicine, local and regional arterial wall stiffness (AWS) parameters are routinely used to assess the vascular health. In horses, information regarding reproducibility of ultrasonographically derived AWS parameters is lacking. To evaluate the inter-day and inter-observer and intra-observer measurement variability of both local and regional AWS parameters in horses. Experimental study. In 10 healthy, adult Warmblood horses, B-, M-mode and pulsed-wave Doppler ultrasound images were collected on two different days from aorta, cranial and caudal common carotid arteries and external iliac artery. Heart rate and noninvasive blood pressure were recorded simultaneously. From blinded data, diastolic and systolic vessel lumen areas and diameters were measured from B/M-mode images and the velocity of the pressure wave was determined by pulsed-wave Doppler spectra. From each horse, one examination was measured again by the same observer and by a second, independent observer. Local and regional AWS parameters were calculated and inter-day and inter-observer and intra-observer measurement coefficient of variation (CV) were assessed. Low CV was found for both arterial diameter and lumen area measurements. Moderate to high CV was found for local AWS parameters, while regional AWS parameters had low CV. The number of horses investigated was too low to obtain reference values. The inter-operator variability was not evaluated. Our results show good reproducibility of aortic, carotid and external iliac artery diameter and area measurements using both B- and M-mode ultrasonography. Nevertheless, the variability of the derived local AWS parameters was relatively high. Therefore, local AWS parameters might be less suitable for follow-up studies, although they might be useful for population studies. On the other hand, regional AWS parameters showed low CV, making them valuable for both follow-up and population studies.

Pharmacokinetic–pharmacodynamic modelling of the antinociceptive effect of a romifidine infusion in standing horses

ObjectiveTo evaluate the effect of a romifidine infusion on antinociception and sedation, and to investigate its relationship with plasma concentration. Study designProspective, experimental, nonrandomized trial. AnimalsA total of 10 healthy adult warmblood horses. MethodsRomifidine (loading dose: 0.08 mg kg–1, infusion: 0.03 mg kg–1 hour–1) was administered intravenously over 120 minutes. Romifidine plasma concentrations were determined by capillary electrophoresis. Sedation quality and nociceptive thresholds were evaluated at regular time points before, during and after romifidine administration. The nociceptive withdrawal reflex was elicited by electrical stimulation at the thoracic limb using a dedicated threshold tracking algorithm and recorded by electromyography at the deltoid muscle. A pharmacokinetic–pharmacodynamic model was established and correlation between romifidine plasma concentration and main output variables tested. ResultsA two compartmental model best described the romifidine pharmacokinetic profile. The nociceptive thresholds increased compared with baseline in all horses from 10 to 146 minutes after romifidine administration (p < 0.001). Peak effect reached 5.7 ± 2.3 times the baseline threshold (mean ± standard deviation). The effect/concentration relationship followed a counter-clockwise hysteresis loop. The mean plasma concentration was weakly correlated to nociceptive thresholds (p < 0.0071, r = 0.392). The sedative effects were significant until 160 minutes but variable, not correlated to plasma concentration (p = 0.067), and weakly correlated to nociceptive thresholds (p < 0.0001, r = 0.33). Conclusions and clinical relevanceRomifidine elicited a marked antinociceptive effect. Romifidine-induced antinociception appeared with a delayed onset and lasted longer than sedation after discontinuing its administration.

Langetermijnresultaat van artrodese van het proximale interfalangeale gewricht bij twee volwassen warmbloedpaarden gebruikmakend van een “locking” compressieplaat en vier trekschroeven

Twee volwassen warmbloedpaarden met een voorgeschiedenis van chronisch manken aan het achterbeen uitgaande van het proximale interfalangeale gewricht (kroongewricht) werden aangeboden op de dierenkliniek De Bosdreef (België) tussen 2016 en 2017. Op basis van de anamnese en het orthopedisch onderzoek werd chronische osteoartrose (OA) van het kroongewricht gediagnosticeerd bij beide paarden. Een gemodificeerde chirurgische artrodese van het kroongericht werd uitgevoerd gebruik makend van een centrale, dorsale driegaten proximale interfalangeale “locking”-compressieplaat (PIP plaat) en vier 5,5 mm transarticulaire, corticale trekschroeven. Dit resulteerde in een snelle botfusie van het kroongewricht en een terugkeer naar het oorspronkelijk werk binnen de tien maanden na operatie.

The Effects of Biannual Equine Influenza Vaccine on Performance in Adult Horses

&lt;p&gt;&lt;strong&gt;PICO question&lt;/strong&gt;&lt;/p&gt;&lt;p&gt;In three day event horses, does biannual routine influenza vaccination compared to annual routine influenza vaccination reduce performance levels?&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Clinical bottom line&lt;/strong&gt;&lt;strong&gt;&lt;br /&gt; &lt;/strong&gt;&lt;/p&gt;&lt;p&gt;There is no evidence that biannual equine influenza vaccination compared to annual booster vaccination in three day event horses is associated with reduced performance.&lt;/p&gt;&lt;p&gt;A group of five studies published over an 11 year period from one were evaluated. In adult warmblood horses there is weak evidence that exercise in the 28 day period post booster vaccination for equine influenza and equine herpes virus 1 and 4 (EHV1&amp;amp;4), is associated with changes in physical and clinical pathophysiological parameters including total red blood cell (RBC) count, neutrophil and lymphocyte count, fibrinogen concentration and serum proteins. These changes occurred at variable time points in the 14 days post exercise and values were not outside the published reference ranges for the reporting laboratories where published. Athletic performance of the horses was not evaluated.&lt;/p&gt;&lt;p&gt;No recommendations for equine influenza vaccination protocols in three day event horses can be made from the evidence.&lt;/p&gt;&lt;p&gt; &lt;/p&gt;&lt;p&gt;&lt;img src="https://www.veterinaryevidence.org/rcvskmod/icons/oa-icon.jpg" alt="Open Access" /&gt; &lt;img src="https://www.veterinaryevidence.org/rcvskmod/icons/pr-icon.jpg" alt="Peer Reviewed" /&gt;&lt;/p&gt;

Reproducibility of arterial diameter measurements using B‐ and M‐mode ultrasonography in standing Warmblood horses

Background: In human medicine, arterial wall stiffness (AWS) parameters are calculated from ultrasonographically measured diastolic (DD) and systolic arterial diameter (SD) in order to assess vascular health. In horses, information regarding reproducibility of ultrasonographic measurements of arterial diameters is lacking. Objectives: To evaluate the inter-day, inter-observer and intra-observer variability of ultrasonographic arterial diameter measurements in horses. Study Design: Prospective study. Methods: In ten healthy, adult Warmblood horses, ultrasound images were recorded on two different days from aorta (B-mode), common carotid and femoral artery (B-mode and M-mode). In addition, heart rate and non-invasive blood pressure were recorded simultaneously. From blinded data, DD and SD were measured over nine cardiac cycles from B/M-mode images of both days, and from each horse, one exam was measured again by the same observer and by a second, independent observer. Inter-day, inter-observer and intra-observer coefficients of variation were calculated. Carotid and femoral diameter measurements from M-mode were compared with diameters derived from measured areas on B-mode images using a paired t-test. Results: There was no significant difference in heart rate or blood pressure between both days. Mean B-mode DD and SD (±standard deviation) for aorta, carotid and femoral artery were 59.8±4.1mm and 66±4.4mm, 11.7±1.1mm and 12.3±1.2mm, and 12.8±1.1mm and 13.2±1.0mm, respectively. The latter were not significantly different from M-mode measurements. For DD and SD from M and B-mode images of all three arteries, inter-day (4-9%), inter-observer (1-3%) and intra-observer (1-2%) variability was low. Main Limitations: A larger group of healthy horses must be examined to define reference ranges for arterial diameters. Conclusions: Our results show good reproducibility of aortic, carotid and femoral diameter measurements using both B- and M-mode ultrasonography, suggesting these are potentially useful variables for assessing AWS in horses.

Use of a 3-Telsa magnet to perform delayed gadolinium-enhanced magnetic resonance imaging of the distal interphalangeal joint of horses with and without naturally occurring osteoarthritis.

OBJECTIVE To characterize delayed gadolinium-enhanced MRI of cartilage (dGEMRIC) features of healthy hyaline cartilage of the distal interphalangeal joint (DIPJ) of horses, to determine whether dGEMRIC can be used to differentiate various stages of naturally occurring osteoarthritis of the DIPJ, and to correlate relaxation times determined by dGEMRIC with the glycosaminoglycan concentration, water content, and macroscopic and histologic findings of hyaline cartilage of DIPJs with and without osteoarthritis. SAMPLE 1 cadaveric forelimb DIPJ from each of 12 adult warmblood horses. PROCEDURES T1-weighted cartilage relaxation times were obtained for predetermined sites of the DIPJ before (T1preGd) and after (T1postGd) intra-articular gadolinium administration. Corresponding cartilage sites underwent macroscopic, histologic, and immunohistochemical evaluation, and cartilage glycosaminoglycan concentration and water content were determined. Median T1preGd and T1postGd were correlated with macroscopic, histologic, and biochemical data. Mixed generalized linear models were created to evaluate the effects of cartilage site, articular surface, and macroscopic and histologic scores on relaxation times. RESULTS 122 cartilage specimens were analyzed. Median T1postGd was lower than the median T1preGd for normal and diseased cartilage. Both T1preGd and T1postGd were correlated with macroscopic and histologic scores, whereby T1preGd increased and T1postGd decreased as osteoarthritis progressed. There was topographic variation of T1preGd and T1postGd within the DIPJ. Cartilage glycosaminoglycan concentration and water content were significantly correlated with T1preGd and macroscopic and histologic scores but were not correlated with T1postGd. CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that dGEMRIC relaxation times varied for DIPJs with various degrees of osteoarthritis. These findings may help facilitate early detection of osteoarthritis.

Effects of transdermal lidocaine or lidocaine with prilocaine or tetracaine on mechanical superficial sensation and nociceptive thermal thresholds in horses

ObjectiveTo evaluate the transdermal local anaesthetic effect of lidocaine or lidocaine combined with prilocaine or tetracaine in horses. Study designExperimental, randomized study. AnimalsA total of five healthy adult warmblood horses. MethodsHorses were clipped bilaterally at the withers, cranial saddle area and caudal saddle area. Baseline measurements for mechanical superficial sensation via von Frey filaments and nociceptive thermal thresholds were performed. A 5% lidocaine patch (12 hour exposure, treatment L), a lidocaine/prilocaine cream (each 2.5%, treatment LP) and a lidocaine/tetracaine cream (each 7%, treatment LT) were applied (both 2 hour exposure). The same product was applied at the same location bilaterally, but on the right side an epidermal micro-perforation (dermaroller, 1200 needles) was performed prior to application. A total of five more measurements were performed at each location, immediately at the end of exposure time followed by hourly measurements. Thermal thresholds normalized to thermal excursion were analysed. One- or two-way anova and the Wilcoxon signed-rank test were used for statistical analysis with p<0.05 considered significant. ResultsEpidermal micro-perforation had no enhancing effect. Treatments L, LP, and LT resulted in increased thermal excursion (%) immediately (84.7±12.9; 100.0±0.0; 100.0±0.0) and 1 hour (81.7±66; 86.0±17.7; 87.7±14.4) after the removal of the respective product compared to baseline (66.1±9.3; 69.9±8.3; 76.5±7.8). Superficial mechanical sensation was decreased by the lidocaine-and-tetracaine cream at all time points, and by the lidocaine patch and lidocaine-and-prilocaine cream for three measurements. Conclusions and clinical relevanceEutectic mixtures of lidocaine with either prilocaine or tetracaine led to a reduction in thermal nociception and mechanical sensation for up to 2 hours.

Clinical comparison of dexmedetomidine and medetomidine for isoflurane balanced anaesthesia in horses

ObjectiveTo compare the effects of two balanced anaesthetic protocols (isoflurane–dexmedetomidine versus medetomidine) on sedation, cardiopulmonary function and recovery in horses. Study designProspective, blinded, randomized clinical study. AnimalsSixty healthy adult warm blood horses undergoing elective surgery. MethodsThirty horses each were sedated with dexmedetomidine 3.5 μg kg−1 (group DEX) or medetomidine 7 μg kg−1 (group MED) intravenously. After assessing and supplementing sedation if necessary, anaesthesia was induced with ketamine/diazepam and maintained with isoflurane in oxygen/air and dexmedetomidine 1.75 μg kg−1 hour−1 or medetomidine 3.5 μg kg−1 hour−1. Ringer's lactate (7–10 mL kg−1 hour−1) and dobutamine were administered to maintain normotension. Controlled mechanical ventilation maintained end-tidal expired carbon dioxide pressures at 40–50 mmHg (5.3–6.7 kPa). Heart rate, invasive arterial blood pressure, inspired and expired gas composition and arterial blood gases were measured. Dexmedetomidine 1 μg kg−1 or medetomidine 2 μg kg−1 was administered for timed and scored recovery phase. Data were analysed using two-way repeated-measures analysis of variance and chi-square test. Significance was considered when p≤0.05. ResultsIn group DEX, significantly more horses (n=18) did not fulfil the sedation criteria prior to induction and received one or more supplemental doses, whereas in group MED only two horses needed one additional bolus. Median (range) total sedation doses were dexmedetomidine 4 (4–9) μg kg−1 or medetomidine 7 (7–9) μg kg−1. During general anaesthesia, cardiopulmonary parameters did not differ significantly between groups. Recovery scores in group DEX were significantly better than in group MED. Conclusions and clinical relevanceHorses administered dexmedetomidine required more than 50% of the medetomidine dose to reach equivalent sedation. During isoflurane anaesthesia, cardiopulmonary function was comparable between the two groups. Recovery scores following dexmedetomidine were better compared to medetomidine.

Suspected aspirin resistance in individual healthy adult warmblood horses.

The reasons for this prospective experimental study were to determine a dosing scheme with loading and maintenance dose of aspirin inducing inhibition of platelet function measured by whole blood impedance aggregometry. Ten horses received aspirin orally in the morning with one loading dose of 4.7-5mg/kg and maintenance doses of 1-1.3mg/kg daily the following 4days. Aggregometries (COLtest, ASPItest, ADPtest) and serum salicylic acid were measured. ASPItest showed significant difference in inhibition at 24 and 48hr (p<.05) and 96hr (p<.01). Significant change for ADPtest and COLtest couldn't be detected. Serum salicylic acid concentrations were significantly (p<.01) increased at 6 and 12hr. Despite this, three horses failed any inhibitory effect of platelet function, suspecting an aspirin resistance. Regarding the other seven horses platelet aggregation induced by ASPItest was reduced between 37% and 100% from baseline at 6 and 12hr and between 0 and 98% during the next 4days. Correlations of serum concentration of salicylic acid and aggregometries couldn't be detected. It can be presumed that equine platelets are less susceptible to aspirin what may compromise eventually the anticoagulatory effects and efficacy in preventing and treating diseases with increased platelet activation as endotoxaemia or laminitis.

Assessment of distribution of ventilation and regional lung compliance by electrical impedance tomography in anaesthetized horses undergoing alveolar recruitment manoeuvres

ObjectiveTo examine changes in the distribution of ventilation and regional lung compliances in anaesthetized horses during the alveolar recruitment manoeuvre (ARM). Study designExperimental study in which a series of treatments were administered in a fixed order on one occasion. AnimalsFive adult Warmblood horses. MethodsAnimals were anaesthetized (xylazine, midazolam–ketamine, isoflurane), placed in dorsal recumbency and ventilated with 100% oxygen using peak inspiratory pressure (PIP) and positive end-expiratory pressure (PEEP) of 20 cmH2O and 0 cmH2O, respectively. Thoracic electrical impedance tomography (EIT), spirometry and routine anaesthesia monitoring were performed. At 90 minutes after induction of anaesthesia, PIP and PEEP were increased in steps of 5 cmH2O to 50 cmH2O and 30 cmH2O, respectively, and then decreased to baseline values. Each step lasted 10 minutes. Data were recorded and functional EIT images were created using three breaths at the end of each step. Arterial blood samples were analysed. Values for left-to-right and sternal-to-dorsal centre of ventilation (COV), lung compliances and Bohr dead space were calculated. ResultsDistribution of ventilation drifted leftward and dorsally during recruitment. Mean±standard deviation (SD) values at baseline and highest airway pressures, respectively, were 49.9±0.7% and 48.0±0.6% for left-to-right COV (p=0.009), and 46.3±2.0% and 54.6±2.0% for sternal-to-dorsal COV (p=0.0001). Compliance of dependent lung regions and PaO2 increased, whereas compliance of non-dependent lung regions decreased during ARM and then returned to baseline (p<0.001). Bohr dead space decreased after ARM (p=0.007). Interestingly, PaO2 correlated to the compliance of the dependent lung (r2=0.71, p<0.001). Conclusions and clinical relevanceThe proportion of tidal volume distributed to dependent and left lung regions increased during ARM, presumably as a result of opening atelectasis. Monitoring compliance of the dependent lung with EIT may substitute PaO2 measurements during ARM to identify an optimal PEEP.