Aorto-cardiac fistulas in seven horses

This report describes the history, clinical, electrocardiographic and echocardiographic findings, treatment, outcome and post-mortem findings in seven horses with aorto-cardiac fistula. Affected horses included 5 stallions, one gelding and one mare; 2 each of the Thoroughbred, Arabian and Standardbred breeds and one Thoroughbred-cross with a mean +/- s.d. age of 12 +/- 4 years, range 6-18 years. The presenting signs were acute distress (four horses), exercise intolerance (two horses) and the lesion was detected during a routine examination in one horse. Five horses had monomorphic ventricular tachycardia on admission and one other had a history of this arrhythmia. Five horses had a characteristic continuous murmur loudest in the right fourth intercostal space. Echocardiography (six horses) and/or post-mortem examination (four horses) revealed the horses had aorto-cardiac fistulas arising from the right aortic sinus in all five horses in which the site was recorded. Two horses had ruptured aneurysmal dilatations of the aortic wall at this site. Fistulas extended into the right ventricle in four horses; the right atrium in two horses, the left ventricle in one horse, and five horses had dissecting tracts in the septal myocardium. Horses survived for periods ranging from 24 h to 4 years. Aorto-cardiac fistula should be considered in the differential diagnosis for horses presenting with acute distress, bounding arterial pulse, a right-sided continuous murmur and/or monomorphic ventricular tachycardia, particularly in middle-aged or older stallions. Echocardiography is the technique of choice for confirming the diagnosis and demonstrating accompanying cardiac changes.

Exercise-related alterations in crimp morphology in the central regions of superficial digital flexor tendons from young thoroughbreds: a controlled study

Injury to the core of the mid-metacarpal region of the superficial digital flexor tendon in Thoroughbred racehorses is a very frequent but poorly understood condition. It has been suggested that subclinical changes induced by galloping exercise weaken the collagen in this region of the tendon, predisposing it to rupture. The longitudinally arranged collagen fibrils in tendon follow a planar waveform, termed the crimp. Fibril bundles with a smaller crimp angle fail at a lower level of strain than those with a larger crimp angle. This study tested the hypothesis that a specific 18 month exercise programme would result in significant reduction of collagen fibril crimp angle and period length in the core region of the superficial digital flexor tendon of young Thoroughbreds (21 +/- 1 months), compared to the normal change in these parameters with age. Central region crimp angle and length were significantly lower in exercised horses than in control horses (P < 0.05). The crimp angle was significantly lower in this central region than in the peripheral region of the tendon in 4 of the 5 exercised horses, as was the crimp length in 3 of the 4 horses. The crimp angle in the peripheral region was significantly greater in exercised horses than in the controls (P < 0.05), which may indicate functional adaptation due to differing mechanical environment between the 2 tendon regions. The results of this study supported previous evidence that galloping exercise modifies normal age-related changes in crimp morphology in the core of the superficial digital flexor tendon. Such changes are indicative of microtrauma and would be detrimental to tendon strength.

Clinical similarities and close genetic relationship of human and animal Borna disease virus

Borna disease virus (BDV) is the prototype genus of a new family, Bornaviridae, within the order Mononegavirales. BDV naturally infects animals and man. The symptomatology in animals ranges from subclinical infection to rare cases of encephalitis. Asymptomatic infection seemed more frequent than expected, based on antibody data from 100 healthy horses derived from different stables with a history of diseased cases (30-40% carriers). Likewise, phasic episodes of a neurobehavioral syndrome followed by recovery were much more common than fatal neurologic disease. They were paralleled by expression of BDV antigens (N-protein p40, P-protein p24) and RNA transcripts in peripheral blood mononuclear cells, indicating viral activation. Representative longitudinal studies showed that episodes of depressive illness in humans as well as apathetic phases in infected horses were accompanied by antigen expression and followed a similar clinical course. After recovery, BDV antigen disappeared. This temporal congruence, together with the recent isolation of infectious BDV from such patients, points to a contributory role of this virus in human affective disorders. Successful amelioration of BDV-induced neurobehavioral disease in horses with antidepressants applied in psychiatry, supported a common viral pathomechanism, involving reversible disturbances of the neurotransmitter network in the limbic system. Sequences of genetic material amplified from infected animal tissue and human PBMCs revealed a close interspecies relationship and high sequence conservation of the BDV genome. In human BDV isolates, however, single unique mutations were prominent in four genes. This finding supports the hypothesis that despite of high genomic conservation, species-specific genotypes may be definable, provided the sequences are derived from RNA of infectious virus.

Field examination of the equine patient with nasal discharge

This article describes the field investigation of horses with nasal discharge (serous, purulent, blood and feed). Flow charts on how to evaluate affected horses, and photographs of the examination procedures and of horses affected with nasal discharge are included.

Poor performance and field evaluation of the respiratory system

A thorough examination of the respiratory system is an important part of the work-up for poor performance in horses. This article provides a systematic approach to field evaluation of horses with poor performance due to respiratory system dysfunction. The information is organized to help the reader evaluate pertinent historical and physical examination findings so that a list of differential diagnoses can be generated. Also, pertinent ancillary diagnostic modalities that can help further characterize and localize causes for respiratory dysfunction in horses presented for poor performance are discussed.

Evaluation of platelet activation and platelet-neutrophil aggregates in ponies with alimentary laminitis

OBJECTIVES

To determine whether platelets are hyperaggregable or form platelet-neutrophil aggregates during the prodromal stages of acute laminitis of ponies.

ANIMALS

Healthy adult ponies: 8 experimental and 6 control.

PROCEDURES

Acute laminitis was induced by oral administration of corn starch and wood flour to 8 ponies, and indices of platelet activation were evaluated. Blood samples were collected before and at 4, 8, 12, 24, 28, and 32 hours after carbohydrate administration, and PCV, total plasma protein concentration, platelet count, activated clotting time, whole blood recalcification time, spontaneous platelet aggregation, ex vivo platelet aggregation responses, and platelet-neutrophil aggregates were determined. When lameness was first detected, ponies were euthanatized and arteriography and histologic examination of hooves were performed.

RESULTS

Carbohydrate overload was associated with hyperaggregability of platelets throughout the prodromal stages of laminitis and increased numbers of platelet-neutrophil aggregates. Reduction of blood supply to affected hooves was variable, and blood clots were found in 6 of 11 laminitis-affected hooves.

CONCLUSIONS

Platelets were hyperaggregable throughout the prodromal stages of carbohydrate-induced laminitis and formed platelet-neutrophil aggregates. Platelet-neutrophil aggregates may initiate or contribute to development of acute laminitis.

CLINICAL RELEVANCE

Anti-platelet therapy may be useful for treatment of acute alimentary laminitis in horses.

Comparison of alveolar ventilation, oxygenation, pressure support, and respiratory system resistance in response to noninvasive versus conventional mechanical ventilation in foals

OBJECTIVE

To compare the efficacy of positive pressure ventilation applied through a mask versus an endotracheal tube, using anesthetized/paralyzed foals as a model for foals with hypoventilation.

ANIMALS

Six 1-month-old foals.

PROCEDURE

A crossover design was used to compare the physiologic response of foals to 2 ventilatory techniques, noninvasive mask mechanical ventilation (NIMV) versus endotracheal mechanical ventilation (ETMV), during a single period of anesthesia and paralysis. Arterial pH, PaO2, PaCO2, oxygen saturation, end-tidal CO2 tension, airway pressures, total respiratory system resistance, resistance across the upper airways (proximal to the midtracheal region), and positive end-expiratory pressures (PEEP) were measured. Only tidal volume (VT; 10, 12.5, and 15 ml/kg of body weight) or PEEP (7 cm of H2O) varied.

RESULTS

Compared with ETMV, use of NIMV at equivalent VT resulted in PaCO2 and pH values that were significantly higher, but PaO2 was only slightly lower. Between the 2 methods, peak airway pressure was similar, but peak expiratory flow was significantly lower and total respiratory resistance higher at each VT for NIMV. Delivery of PEEP (7 cm of H2O) was slightly better for ETMV (7.1 +/- 1.3 cm of H2O) than for NIMV (5.6 +/- 0.6 cm of H2O).

CONCLUSION

These data suggest that use of NIMV induces similar physiologic effects as ETMV, but the nasal cavities and mask contribute greater dead space, manifesting in hypercapnia. Increasing the VT used on a per kilogram of body weight basis, or the use of pressure-cycled ventilation might reduce hypercapnia during NIMV.

CLINICAL RELEVANCE

Use of NIMV might be applicable in selected foals, such as those with hypoventilation and minimal changes in lung compliance, during weaning from endotracheal mechanical ventilation, or for short-term ventilation in weak foals.

Endometritis, salpingitis and fertilisation rates after mating mares with a history of intrauterine lumenal fluid accumulation

The occurrence of uterine and oviductal inflammation, and fertilisation rates, were measured on Day 3 post ovulation in inseminated mares that had either exhibited intrauterine lumenal fluid during a previous dioestrus (Experiment 1) or had acute endometritis induced by intrauterine infusion of 1% glycogen (Experiment 2). Endometritis was assessed by uterine cytology and histology whereas oviductal inflammation was measured histologically. Fertilisation rates were calculated from the percentage of cleaved ova recovered by retrograde flushing of the oviducts. Mares with or without pre-existing uterine fluid during dioestrus that were inseminated showed a higher incidence of endometritis than control mares without pre-existing uterine fluid that were not inseminated (n = 7 mares/group). However, inseminated mares with uterine fluid did not show a higher incidence of endometritis than inseminated mares without uterine fluid. Mares with or without pre-existing uterine fluid showed a higher incidence of endometritis than salpingitis and these 2 groups of mares showed equivalent rates of fertilisation and oviductal oocyte recovery. Mares inseminated with semen alone or semen following 1% glycogen treatment had a higher incidence of endometritis than control noninseminated mares (n = 17 mares/group) but mares that received semen plus 1% glycogen did not show a higher incidence of endometritis than mares that received semen alone. Both these groups of mares showed a higher incidence of endometritis than salpingitis and those that received semen plus 1% glycogen showed an equal recovery rate of recently ovulated ova but a lower fertilisation rate than the mares that received semen alone.

Intrinsic, management, and nutritional factors associated with equine motor neuron disease

OBJECTIVE

To identify intrinsic, management, nutritional, and environmental risk factors associated with equine motor neuron disease (EMND) and to determine whether epidemiologic evidence supports oxidative stress as a risk factor for developing EMND.

DESIGN

Case-control study.

ANIMALS

87 horses with EMND and 259 control horses.

PROCEDURE

Information concerning each horse's history of exposure to multiple environmental factors prior to developing EMND was obtained by means of a questionnaire or personal interview. Exposure histories of horses with EMND and control horses were compared, and the association of each risk factor with EMND was evaluated, using logistic regression analysis.

RESULTS

Factors significantly associated with risk of developing EMND included age, breed of horse, duration of residence at the farm, not vaccinating against rabies, and certain feeding practices. Horses that were exercised on green pasture or in grass paddocks were less likely to develop EMND, compared with horses that were exercised in dirt pad-docks. Feeding complete pelleted feed as the only source of concentrate or combined with sweet feed was associated with a significant increase in the risk of EMND. Supplementary feeding of vitamin and mineral mixtures not formulated to provide vitamin E or selenium was associated with increased risk of EMND. Horses with a history of cribbing or coprophagia were also at higher risk of developing EMND.

CLINICAL IMPLICATIONS

Several husbandry practices and intrinsic characteristics of horses appear to modify the risk of EMND. The relationship of specific nutritional factors to EMND supports the hypothesis that a deficiency of vitamin E contributes to the disease.

[Equine recurrent uveitis]

Equine recurrent uveitis is an important ocular disease and the most common cause for blindness in horses and mules worldwide. The anatomy, physiology, immunology and inflammatory reactions of the uveal tract are discussed. Possible etiologies and the clinical signs are described. A detailed description of possible therapies is given and the prognosis is discussed.

Technical validation of a face mask adapted for dry powder inhalation in the equine species

Development of dry powder inhalation (DPI) for horses requires the use of an adapted face mask. In experiment I, 4 masks (A, B, C and D) were tested and factors influencing the delivery of the dry powder were determined. Mask A was one which is commercially available for metered-dose inhalation. Mask B had the same shape as Mask A but an airtight rubber seal was added for the connection between the mask and horse's head. Mask C was a prototype adapted for DPI with connection for the DPI device between the nostrils, airtight expiratory valves in front of each nostril and airtight rubber seal to attach the mask on the horse's head. Mask D was the same as Mask C but the airtight expiratory valve was situated in front of one nostril and the connection for the DPI device was placed in front of the other nostril. Inhalet emptying and peak inspiratory pressure were measured on 5 healthy horses with each face mask. Both Masks A and B gave a low rate of inhalet emptying. Inspiratory pressures created in Masks C and D were negative enough to ensure inhalet emptying rates of mean +/- s.d. 98.28 +/- 1.79% and 100% respectively. In experiment 2, the face masks giving the greatest inhalet emptying were used to test the therapeutic efficacy of ipratropium bromide DPI. This was tested on 6 horses suffering from acute exacerbation of chronic obstructive pulmonary disease (COPD). At a dose of 200 micrograms/100 kg bwt, ipratropium administered with Mask D improved significantly pulmonary function measurements compared to baseline values and placebo inhalation. With Mask C, a double dose of ipratropium (400 micrograms/100 kg bwt) was necessary to improve these parameters compared to baseline values. This indicated the importance of locating the DPI device in front of one nostril. It was concluded that inhalet emptying is correlated to inspiratory pressures measured in the face masks. Secondly, these pressures are in turn dependent on the air-tightness of the mask, i.e. air-tightness of the expiratory valve and close connection between the horse's head and the mask. Thirdly, position of the DPI device in front of a nostril allows bronchodilation at a dose half that required when the device is placed between the nostrils. Finally DPI using Mask D (EquiPoudre) is a rapid, effective and well tolerated inhalation treatment for COPD horses.

In vitro responses to noradrenaline of small intestine taken from normal and grass sickness-affected horses

Small intestine was taken from the caudal flexure of the duodenum and the terminal ileum proximal to the ileocaecal fold of 25 horses, 9 with acute grass sickness (AGS), 12 with subacute grass sickness (SAGS) and 12 with chronic grass sickness (CGS). The motility in the samples was measured isometrically either within 1 h of death or after storage for 24 h at 4 degree C. In control tissue, noradrenaline produced contractions of muscle strips which did not involve a muscarinic cholinergic mechanism and which were unaffected by the alpha 1 antagonist prazosin but were blocked by the alpha 2 antagonist yohimbine. Pretreatment with the alpha antagonist phentolamine prevented the contractile response to noradrenaline and the background contractions either continued at a reduced rate and amplitude or were abolished after a few minutes. Thus, following alpha blockade, noradrenaline reduced the background contraction rate by an effect on inhibitory beta adrenoceptors. The rate of background contractions in duodenal preparations was significantly greater than that in control ideal preparations. Although cold storage for 24 h caused a reduction in the background contraction rates of the control preparations, there was no effect on the contractile responses to noradrenaline, the associated pharmacology being similar to that of fresh tissue. This suggests that noradrenaline-evoked contraction was not dependent on enteric neural elements. The response to noradrenaline by grass sickness-affected tissue was generally similar to that of tissue from control horses, with an immediate contraction which was alpha 2 sensitive. The contractile response to noradrenaline after propranolol was significantly reduced in the CGS group and there were significant differences between the AGS, CGS and control groups. There was a significant difference between the ileal preparations from the control and SAGS groups in their response to noradrenaline following pretreatment with propranolol.

Effect of pentoxifylline, flunixin meglumine, and their combination on a model of endotoxemia in horses

OBJECTIVE

To compare effects of a single dose of pentoxifylline (PTX), flunixin meglumine (FM), and their combination (FM/PTX) in a model of equine endotoxemia.

ANIMALS

24 healthy horses, aged 2 to 15 years.

PROCEDURE

4 groups (n = 6/group) received 30 ng of Escherichia coli O55:B5 endotoxin/kg of body weight, i.v., over 30 minutes, and 1 of the following preparations 15 minutes before and 8 hours after endotoxin infusion: FM, 1.1 mg/kg; PTX, 8 mg/kg; FM/PTX, 1.1 mg of FM and 8 mg of PTX/kg; and saline solution bolus (ENDO). Clinical and hematologic variables were measured over 24 hours.

RESULTS

Compared with ENDO, FM given before endotoxin significantly reduced TxB2, and 6-keto-PGF1 concentrations, pulse, rectal temperature, and attitude score. Pentoxifylline given before endotoxin resulted in significantly higher 6-keto-PGF1 concentration at 1.5 hours and significantly lower PAI-1 activity at 12 hours. Tumor necrosis factor and IL-6 activities in horses given PTX alone were not significantly different from values in those given the saline bolus. FM/PTX induced effects similar to those of FM alone on endotoxin-induced changes in temperature and TxB2 concentration, and 6-keto-PGF1 concentration was significantly lower than that in horses of the ENDO group at 1 hour. In horses of the FM group, 6-keto-PGF1 concentration was significantly lower than that in horses of the ENDO group, from 0.5 hour to 2 hours. Horses of the FM and FM/PTX groups had significantly higher IL-6 activity at 1.5 and 2 hours than did horses of the PTX and ENDO groups; those of the FM and FM/PTX groups had significantly lower WBC count than did those of the PTX and ENDO groups.

CONCLUSIONS

FM/PTX may help offset deleterious hemodynamic effects of endotoxin more effectively than does either FM or PTX alone.

Laryngoplasty with or without ventriculectomy for treatment of left laryngeal hemiplegia in 230 racehorses

OBJECTIVE

The purpose of this study was to examine the influence of laryngoplasty on racing performance and to determine if any of the following variables had a significant effect on outcome: breed (Thoroughbred v Standardbred), endoscopic grade of laryngeal function, ventriculectomy versus no ventriculectomy, type of prosthetic suture used, and number of prostheses placed.

STUDY DESIGN

Retrospective study of laryngoplasty with or without ventriculectomy for treatment of left laryngeal hemiplegia in racehorses between 1986 and 1993.

ANIMALS OR SAMPLE POPULATION

230 horses (174 Thoroughbreds, 56 Standardbreds).

METHODS

The medical records of racehorses or horses intended for racing were reviewed. Signalment, admitting complaints, physical examination findings, resting endoscopic grade of laryngeal function, type of prosthetic suture material used, number of prosthetic sutures placed, presence or absence of ventriculectomy, and postoperative complications were recorded.

RESULTS

Upper respiratory tract noise and exercise intolerance were the most common presenting complaints. Two horses had a laryngeal grade of 2, 109 horses a laryngeal grade of 3, and 119 horses a laryngeal grade of 4. Two double-strand braided polyester sutures were used in 147 horses, a single double-strand polyester suture was used in 49 horses, and a single double-strand nylon suture was used in 34 horses. Ventriculectomy was performed on 186 horses. The most common complication recognized during hospitalization was coughing in 50 horses. Telephone follow-up was obtained for 176 horses. For 168 horses, respiratory noise after surgery was decreased in 126 horses, the same in 28, and increased in 14. After hospital discharge, coughing occurred in 43 of 166 horses, and a nasal discharge occurred in 26 horses. Postoperative racing performance for 167 horses was subjectively evaluated by respondents as being improved in 69% of the horses. Overall owner satisfaction with the outcome after surgery was 81%. Of 230 horses, 178 raced at least one time after surgery. Overall, 117 horses raced three or more times before and after surgery, and 65 of these horses had improved performance index scores. None of the variables of surgical interest affected performance index scores.

CONCLUSIONS AND CLINICAL RELEVANCE

Laryngoplasty with or without ventriculectomy allowed 77% of the horses to race at least one time after surgery, improved racing performance in 56% of the horses that completed three races before and after surgery, and improved subjectively evaluated racing performance in 69% of the horses.

Effects of pentoxifylline infusion on response of horses to in vivo challenge exposure with endotoxin

OBJECTIVE

To evaluate the effect of pentoxifylline on response of horses to in vivo challenge exposure with endotoxin.

ANIMALS

24 healthy horses in 3 treatment groups: pentoxifylline, endotoxin, or endotoxin and pentoxifylline.

PROCEDURE

Horses of the pentoxifylline group were given a bolus of pentoxifylline (7.5 mg/kg of body weight, i.v.), followed by an infusion (3 mg/kg/h) over 3 hours, and those of the endotoxin group were given 20 ng of endotoxin/kg i.v. over 30 minutes. Those of the combination group were given both of the aforementioned compounds; pentoxifylline was administered immediately after endotoxin. Clinical (rectal temperature, heart and respiratory rates, blood pressure) and hematologic (WBC count; whole blood recalcification time; plasma fibrinogen, thromboxane B2, and 6-keto-prostaglandin F1 alpha concentrations; plasma plasminogen activator inhibitor activity; and serum tumor necrosis factor and interleukin 6 activities) variables were evaluated over 24 hours.

RESULTS

Compared with baseline values, there were no significant changes in any variable over time in the horses receiving only pentoxifylline, with the exception of a significant increase in WBC count. Rectal temperature, heart rate, mean blood pressure, WBC count, whole blood recalcification time, fibrinogen concentration, plasminogen activator inhibitor activity, tumor necrosis factor and interleukin 6 activities, and plasma thromboxane B2 concentration changed significantly over time in horses of the endotoxin and endotoxin-pentoxifylline combination groups. Respiratory rate and plasma 6-keto-prostaglandin F1 alpha concentration changed significantly over time only in horses of the endotoxin group. Compared with values for the endotoxin group, rectal temperature and respiratory rate were significantly lower, and whole blood recalcification time was longer for the endotoxin/pentoxifylline group.

CONCLUSION

Beneficial effects of pentoxifylline are limited when it is administered i.v. to horses after in vivo challenge exposure with endotoxin.

Airborne dust and aeroallergen concentrations in different sources of feed and bedding for horses

Standardized methods were used to make quantitative and qualitative assessments of respirable dust and aeroallergens in feed and bedding for horses. Concentrations of airborne dust were measured by using a Rion particle counter, and levels of major aeroallergens implicated in chronic obstructive pulmonary disease were measured by using an Andersen sampler. Laboratory conditions allowed comparison of the different sources of forage, supplements, and bedding without external influences such as ventilation, external temperature and horse activity affecting the result. Grass silages of approximately 50% dry matter and alfalfa pellets appeared to be very good sources of forage with low levels of dust and aeroallergens. The studied good quality straw was significantly less dusty with fewer allergens than the wood shavings. Supplements, such as whole grains and molassed concentrates, contained many respirable particles and aeroallergens. Rolled grains were significantly more dusty than good hay.

Stress response to chronic inflammation in the horse

Five clinically healthy Thoroughbred geldings were injected with Freund's adjuvant 3 times to induce a chronic inflammatory response. Blood was collected at various times before and after adjuvant administration. Clinical responses (rectal temperature and general demeanor) were also monitored. Adjuvant injection induced increases in rectal temperature and plasma fibrinogen concentration (maximum levels measured were mean +/- s.d. 39.7 +/- 0.5 degrees C and 8.2 +/- 0.3 g/l, respectively), indicative of an inflammatory response. A mild clinical depression was also observed in the horses for 24 h after the first injection of adjuvant only. Plasma cortisol levels decreased significantly from control levels of mean +/- s.d. 187.7 +/- 24.3 nmol/l to a minimum of 80.2 +/- 22.1 nmol/l (P < 0.01) 9 days after the first injection of adjuvant. Conversely, plasma insulin levels increased after the first injection of adjuvant to a maximum (96.7 +/- 15.2 iu/ml; P < 0.01) 12 days later, while plasma glucose concentrations tended to decline. A control group of horses to rule out contemporary environmental influences on the physiological and biochemical indices measured was not included in this study. The results show that chronic inflammation in the horse depressed resting plasma cortisol concentrations.

Influence of preoperative complete blood cell counts on surgical outcomes in healthy horses: 102 cases (1986-1996)

OBJECTIVE

To assess the value of CBC as a preoperative test in healthy horses undergoing cryptorchidectomy.

DESIGN

Retrospective study.

ANIMALS

117 horses.

PROCEDURE

Medical records were reviewed to identify horses that had had cryptorchidectomy. Of the 117 horses identified, 102 were found that did not have a known medical condition believed to adversely affect surgery. Preoperative CBC was assessed in terms of abnormalities detected and effects of these abnormalities on development of complications during and after surgery and patient management.

RESULTS

Of 102 CBC performed, 55 contained abnormalities. Mild neutrophilia was detected in 40 horses. Of the remaining 15 horses with abnormal CBC, 8 had abnormalities that were considered potentially important. Changes in patient management and development of surgical complications were not associated with these 8 horses. Surgical complications were defined as intraoperative changes in blood pressure, excessive blood loss, development of postanesthetic myopathies, and postoperative wound or respiratory tract infections. Surgical complications developed in 17 horses. Of these, 6 horses had an abnormal CBC that was indicative of mild neutrophilia. Positive and negative predictive values of preoperative CBC on development of perioperative complications were 0.11 and 0.77, respectively.

CLINICAL IMPLICATIONS

On the basis of findings in our study, determination of preoperative CBC does not predict development of complications during or after surgery and does not alter patient management.

Effects of intravenous administration of sodium hyaluronate on carpal joints in exercising horses after arthroscopic surgery and osteochondral fragmentation

OBJECTIVE

To evaluate the effects of arthroscopic surgery, osteochondral fragmentation, and treatment with IV administered hyaluronate on histologic, histochemical, and biochemical measurements within the carpal joints of horses.

ANIMALS

12 clinically normal horses, 2 to 7 years of age.

PROCEDURE

Horses had an osteochondral fragment created at the distal aspect of the radiocarpal bone of 1 randomly chosen middle carpal joint to simulate osteochondral fragmentation. Horses were treated with 40 mg of hyaluronate or saline solution (placebo) intravenously once a week for 3 consecutive weeks (days 13, 20, and 27 after surgery). Treadmill exercise proceeded 5 days per week beginning 15 days, and ending 72 days, after surgery. Clinical evaluations were performed at the beginning and end of the study. Synovial fluid samples were obtained aseptically from both middle carpal joints on days 0, 13, 20, 27, 34, and 72 after surgery, and total protein, inflammatory cell, hyaluronate, glycosaminoglycan, and prostaglandin E2 concentrations were measured in each sample. All horses were euthanatized on day 72. Synovial membrane and articular cartilage were obtained for histologic evaluation. Articular cartilage samples were also obtained aseptically for determining glycosaminoglycan content and chondrocyte synthetic rate for glycosaminoglycans.

RESULTS

Horses treated with hyaluronate intravenously had lower lameness scores (were less lame), significantly better synovial membrane histologic scores, and significantly lower concentrations of total protein and prostaglandin E2 within synovial fluid 72 days after surgery, compared with placebo-treated horses. Treatment with intravenously administered hyaluronate had no significant effects on glycosaminoglycan content, synthetic rate or morphologic scoring in articular cartilage, or other synovial fluid measurements.

CONCLUSION

Intravenously administered hyaluronate appears to alleviate signs of lameness by interacting with synoviocytes, and by decreasing production and release of inflammatory mediators.

Transient glucose malabsorption in two horses--fact or artefact?

Two horses, presented for investigation of chronic weight loss despite normal to increased feed intake, had flat oral glucose absorption curves, suggesting malabsorption. The cause of the apparent malabsorption was not evident grossly or on light microscopic examination of the intestinal tract. Both horses survived long term and at follow-up examination had regained weight and their capacity to absorb glucose. These cases illustrate that flat glucose absorption curves may occur in horses with no obvious intestinal lesions, that they may revert to normal and that the results of these tests should be interpreted with caution.