Exercising Blood Gas Analysis, Dynamic Upper Respiratory Tract Obstruction, and Postexercising Bronchoalveolar Lavage Cytology—A Comparative Study in Poor Performing Horses

Respiratory abnormalities are common causes of decreased performance in horses presumably because of impaired pulmonary gas exchange. The objectives of the present study were to describe respiratory abnormalities in poorly performing horses and to investigate the relationships between dynamic upper respiratory tract (URT) videoendoscopy, postexercising bronchoalveolar lavage (BAL) cytology, and exercising arterial blood gas analysis. Medical records of 93 horses with exercise intolerance, which presented for treadmill evaluation, were reviewed. Relationships between horse demographics, treadmill endoscopic findings, exercising blood gas values, and BAL cytology results were examined. A total of 25 (27%) horses had a URT obstruction and 91 (98%) horses had abnormal BAL cytology; 73 (78%) had evidence of inflammatory airway disease (IAD) and 83 (89%) had exercise-induced pulmonary hemorrhage (EIPH). In all, 39 (42%) horses had abnormal blood gas values. Dynamic URT obstruction was significantly associated with exercising hypoxemia (P = .036). There were no significant relationships between gas exchange and IAD or between EIPH. Out of 24 (26%) horses with combined URT obstruction and abnormal BAL, horses with URT obstruction and EIPH were more likely to be hypoxic during exercise (P = .037). It was concluded that horses with dynamic URT abnormalities are likely to have exercising hypoxemia. Although IAD and EIPH were commonly indentified in poor performers, they were not significantly associated with abnormal exercising blood gas analysis.     

Pharmacokinetics of furosemide administered 4 and 24 hours prior to high‐speed exercise in horses

Furosemide is a diuretic agent used commonly in racehorses to attenuate the bleeding associated with exercise‐induced pulmonary hemorrhage (EIPH). The current study describes serum and urine concentrations and the pharmacokinetics of furosemide following administration at 4 and 24 hrs prior to maximal exercise. Eight exercised adult Thoroughbred horses received a single IV administration of 250 mg of furosemide at 4 and 24 hrs prior to maximal exercise on a high‐speed treadmill. Blood and urine samples were collected at time 0 and at various times for up to 72 hrs and furosemide concentrations determined using liquid chromatography–tandem mass spectrometry. Serum furosemide concentrations remained above the LOQ (0.05 ng/ml) for 36 hrs in 3/8 and 1/8 horses in the 4‐ and 24‐hrs groups, respectively. Serum concentration data were best fit by a two‐compartment model. There was not a significant difference in the volume of distribution at steady‐state (0.594 ± 0.178 [4 hrs] and 0.648 ± 0.147 [24 hrs] L/kg) or systemic clearance (0.541 ± 0.094 [4 hrs] and 0.617 ± 0.114 [24 hrs] L/hrs/kg) between horses that were exercised at 4‐ and 24 hrs postdrug administration. The mean ± SD elimination half‐life was 3.12 ± 0.387 and 3.23 ± 0.407 hrs following administration at 4 and 24 hrs prior to exercise, respectively.     

Effect of furosemide and furosemide–carbazochrome combination on exercise-induced pulmonary hemorrhage in Standardbred racehorses

The objective was to quantify the effect of furosemide and carbazochrome on exercise-induced pulmonary hemorrhage (EIPH) in Standardbred horses using red blood cell count and hemoglobin concentration in bronchoalveolar lavage (BAL) fluid. Six healthy Standardbred horses with prior evidence of EIPH performed a standardized treadmill test 4 h after administration of placebo, furosemide, or furosemide–carbazochrome combination. Red blood cell (RBC) counts and hemoglobin concentrations were determined on the BAL fluid. The RBC count in BAL ranges were (2903–26 025 cells/μL), (45–24 060 cells/μL), and (905–3045 cells/μL) for placebo, furosemide, and furosemide–carbazochrome, respectively. Hemoglobin concentration ranges were (0.03–0.59 mg/mL), (0.01–0.55 mg/mL), and (0.007–0.16 mg/mL) for placebo, furosemide, and furosemide– carbazochrome groups, respectively. No significant differences were detected among treatments. However, there was great variability among horses, suggesting that a larger sample size or better selection of horses was needed.     

The Effectiveness of Immunotherapy in Treating Exercise-Induced Pulmonary Hemorrhage

Inflammatory airway disease has been linked to exercise-induced pulmonary hemorrhage (EIPH), and consequently, we hypothesized that immunomodulation via concentrated equine serum (CES) treatment would reduce EIPH as evidenced by red blood cell (RBC) concentrations in bronchoalveolar lavage fluid (BALF). Separate trials were conducted on Thoroughbred horses treated with either CES (n = 6) or placebo (0.9% saline; n = 4). All horses completed pre-treatment and post-treatment (2 and 4 weeks after initiating treatment) maximal exercise tests on a 10% inclined treadmill (1 m/s/min increments to fatigue) over a 10-week period (2−3 weeks between tests), with bronchoalveolar lavage (BAL) performed 30 minutes after exercise. Treatment ensued 10 days after the pre-treatment exercise test, with horses receiving a series of five CES or placebo injections 24 hours apart (20 mL intratracheal and 10 mL intravenously), with subsequent weekly injections for 5 weeks thereafter. After CES treatment, both EIPH (RBC in BALF) and inflammation (white blood cell concentration [WBC] in BALF) were significantly diminished by the 4-week posttreatment run, demonstrating 46 ± 12% and 24 ± 11% decreases, respectively (P < 0.05). In contrast, EIPH was elevated significantly at the 4-week time point, and inflammation remained constant in the placebo trial. In conclusion, these preliminary data suggest that therapeutic intervention involving immunomodulation may represent a viable approach to reducing the severity of EIPH.     

Clenbuterol administration does not enhance the efficacy of furosemide in attenuating the exercise-induced pulmonary capillary hypertension in Thoroughbred horses

The stimulation of pulmonary beta2-adrenergic receptors causes a decrease in vascular resistance. Thus, the present study was carried out to examine whether concomitant administration of clenbuterol-a beta2-adrenergic receptor agonist, to horses premedicated with furosemide would attenuate the exercise-induced pulmonary capillary hypertension to a greater extent than furosemide alone, and in turn, affect the occurrence of exercise-induced pulmonary hemorrhage (EIPH). Experiments were carried out on six healthy, sound, exercise-trained Thoroughbred horses. All horses were studied in the control (no medications), furosemide (250 mg i.v., 4 h pre-exercise)-control, and furosemide (250 mg i.v., 4 h pre-exercise)+clenbuterol (0.8 microg/kg i.v., 11 min pre-exercise) experiments. The sequence of these treatments was randomized for every horse, and 7 days were allowed between them. Using catheter-tip-transducers whose in-vivo signals were referenced at the point of the left shoulder, pulmonary vascular pressures were determined at rest, sub-maximal exercise, and during galloping at 14.2 m/s on a 3.5% uphill grade--a workload that elicited maximal heart rate. In the control study, incremental exercise resulted in progressive significant (P<0.05) increments in heart rate, right atrial as well as pulmonary arterial, capillary and venous (wedge) pressures, and all horses experienced EIPH. Furosemide administration caused a significant (P<0.05) reduction in mean right atrial as well as pulmonary capillary and venous pressures of standing horses. Although exercise in the furosemide-control experiments also caused right atrial and pulmonary vascular pressures to increase significantly (P<0.05), the increment in mean pulmonary capillary and wedge pressures was significantly (P<0.05) attenuated in comparison with the control study, but all horses experienced EIPH. Clenbuterol administration to standing horses premedicated with furosemide caused tachycardia, but significant changes in right atrial or pulmonary vascular pressures were not discerned at rest. During exercise in the furosemide+clenbuterol experiments, heart rate, mean right atrial as well as pulmonary arterial, capillary and wedge pressures increased significantly (P<0.05), but these data were not different from the furosemide-control experiments, and all horses experienced EIPH as well. Thus, it was concluded that clenbuterol administration is ineffective in modifying the pulmonary hemodynamic effects of furosemide in standing or exercising horses. Because the intravascular force exerted onto the blood-gas barrier of horses premedicated with furosemide remained unaffected by clenbuterol administration, it is believed that concomitant clenbuterol administration is unlikely to offer additional benefit to healthy horses experiencing EIPH.     

Exercise-induced pulmonary hemorrhage in exercising Thoroughbreds: preliminary results with pre-exercise medication

Thoroughbreds with a confirmed history of exercise-induced pulmonary hemorrhage (EIPH) were treated pre-exercise with atropine sulfate, cromolyn, ipratropium or furosemide. Atropine prevented EIPH in 3 of 3 trials in 1 horse, while having no significant effect on bleeding status in the other 2 horses. Pre-exercise treatment with cromolyn had no significant effects in the 3 horses. Pre-exercise treatment of ipratropium was apparently responsible for preventing EIPH in 17 out of 18 trials in 2 horses. The pharmacologic properties of ipratropium in the horse have not been studied, but based on human investigation it seems most probable that its bronchodilator effects are responsible for preventing EIPH in the 2 horses. Furosemide administered in different dosages and time intervals prior to exercise did not prevent EIPH in these 3 horses.     

Equine bronchoalveolar lavage cytology: survey of Thoroughbred racehorses in training

SUMMARY Sixty-two Thoroughbred horses aged between 1 and 7 years in training in Sydney had bronchoalveolar lavage (BAL) samples collected for cytological examination. All horses, except the yearlings and those with a cough, had raced at the time of the examination and the trainers reported satisfactory performance. Free erythrocytes were found In 73% of samples and haemoslderophages In 90% of the samples, Indicating Immediate or past occurrences of exercise-Induced pulmonary haemorrhage (EIPH). Bronchoalveolar fluid from the yearlings contained significantly less (P / 0.05) erythrocytes and haemosiderophages than samples from horses In other age groups. In the older horses, there was also more haemosiderln within the macrophages. No differences In BAL cytology could be attributed to gender, and there was no relationship between BAL cytology and racing performance. The main cytological findings were (mean ± sd): total nucleated cells - 832 ± 578/μL with the main cell types being: macrophages - 59 ± 10% (haemosiderophages - 20 ± 24%); neutrophlls - 9 ± 6%; lymphocytes - 31 ± 9%. The erythrocyte count was 10.3 ± 17.7% of the total cell count. Horses with chronic coughing had a higher proportion of macrophages and a lower proportion of lymphocytes in the leucocytes obtained from BAL. There was a higher occurrence of EIPH detected In BAL findings than that previously reported when endoscopic examination has been used to diagnose EIPH. The occurrence and severity of EIPH as Indicated by the BAL findings was found to be related to exercise Intensity. The cytological findings were similar to those reported in horses in the northern hemisphere. We conclude that BAL cytology may be useful In the diagnosis of various lower respiratory tract disorders and that exercise-induced pulmonary haemorrhage occurs In virtually all horses In race training.     

Clinical, radiographic, endoscopic, bronchoalveolar lavage and lung biopsy findings in horses with exercise-induced pulmonary hemorrhage

A clinical study was performed to determine whether clinical, endoscopic, radiographic, bronchoalveolar lavage (BAL) cytological, and pulmonary biopsy findings could be correlated in horses with exercise-induced pulmonary hemorrhage (EIPH) compared with controls. Racing standardbred horses were selected as either EIPH (n = 10) or control (n = 10), based on repeated postexertional endoscopy of the lower airways. Complete physical and respiratory examinations were performed and blood samples were submitted for arterial blood gas analysis, hematologic study, and fibrinogen determination. Bilateral chest radiographs were taken with the horse standing, and a BAL sample was obtained for cytological examination. Lung was biopsied transcutaneously. Weighted scores were calculated for clinical, radiographic, and pulmonary biopsy findings. The conclusion was that only routine physical examination may help the clinician when EIPH is suspected in horses, especially when there are abnormal findings on percussion of the caudodorsal areas of the chest.     

Efficacy of furosemide in the treatment of exercise-induced pulmonary hemorrhage in Thoroughbred racehorses

The repeatability of endoscopic observations of exercise-induced pulmonary hemorrhage (EIPH) and the efficacy of furosemide as a prophylactic treatment of horses with EIPH were studied in Thoroughbred race horses after consecutive breezes (at or near maximum speed, approx 16 m/s). Of 56 horses examined greater than or equal to 2 times, 21 (38%) had identical EIPH scores, whereas 26 (46%) and 9 (16%) had scores that differed by greater than or equal to 1 grade. In 56 nontreated horses, there was good agreement between 2 consecutive observations (K = 0.59, Z = 4.54, P less than 0.001). Similar comparisons after placebo (saline solution) treatment of 21 horses yielded fair to good agreement, whereas poorer agreement was seen after furosemide treatment of 23 horses. Comparison of average and maximum EIPH scores of 44 horses with a minimum of 4 observations (2 nontreated, 1 saline-treated, and 1 furosemide-treated) indicated that although furosemide did not stop EIPH, it did reduce the EIPH score in 28 (64%) horses.     

Influence of furosemide on hemodynamic responses during exercise in horses.

Four hours prior to exercise on a high-speed treadmill, 4 dosages of furosemide (0.25, 0.50, 1.0, and 2.0 mg/kg of body weight) and a control treatment (10 ml of 0.9% NaCl) were administered IV to 6 horses. Carotid arterial pressure (CAP), pulmonary arterial pressure (PAP), and heart rate were not different in resting horses before and 4 hours after furosemide administration. Furosemide at dosage of 2 mg/kg reduced resting right atrial pressure (RAP) 4 hours after furosemide injection. During exercise, increases in treadmill speed were associated with increases in RAP, CAP, PAP, and heart rate. Furosemide (0.25 to 2 mg/kg), administered 4 hours before exercise, reduced RAP and PAP during exercise in dose-dependent manner, but did not influence heart rate. Mean CAP was reduced by the 2-mg/kg furosemide dosage during exercise at 9 and 11 m/s, but not at 13 m/s. During recovery, only RAP was decreased by furosemide administration. Plasma lactate concentration was not significantly influenced by furosemide administration. Furosemide did not influence PCV or hemoglobin concentration at rest prior to exercise, but did increase both variables in dose-dependent manner during exercise and recovery. However, the magnitude of the changes in PCV and hemoglobin concentration were small in comparison with changes in RAP and PAP, and indicate that furosemide has other properties in addition to its diuretic activities. Furosemide may mediate some of its cardiopulmonary effects by vasodilatory activities that directly lower pulmonary arterial pressure, but also increase venous capacitance, thereby reducing venous return to the atria and cardiac filling.     

Review of furosemide in horse racing: its effects and regulation

Furosemide has been used empirically and has been legally approved for many years by the US racing industry for the control of exercise-induced pulmonary haemorrhage (EIPH) or bleeding. Its use in horses for this purpose is highly controversial and has been criticized by organizations outside and inside of the racing industry. This review concentrates on its renal and extra-renal actions and the possible relationship of these actions to the modification of EIPH and changes in performance of horses. The existing literature references suggest that furosemide has the potential of increasing performance in horses without significantly changing the bleeding status. The pulmonary capillary transmural pressure in the exercising horse is estimated to be over 100 mmHg. The pressure reduction produced by the administration of furosemide is not of sufficient magnitude to reduce transmural pressures within the capillaries to a level where pressures resulting in rupture of the capillaries, and thus haemorrhage, would be completely prevented. This is substantiated by clinical observations that the administration of furosemide to horses with EIPH may reduce haemorrhage but does not completely stop it. The unanswered question is whether the improvement of racing times which have been shown in a number of studies are due to the reduction in bleeding or to other actions of furosemide. This review also discusses the difficulties encountered in furosemide regulation, in view of its diuretic actions and potential for the reduction in the ability of forensic laboratories to detect drugs and medications administered to a horse within days or hours before a race. Interactions between nonsteroidal anti-inflammatory drugs (NSAIDs) and furosemide have also been examined, and the results suggest that the effects of prior administration of NSAID may partially mitigate the renal and extra-renal effects which may contribute to the effects of furosemide on EIPH.     

Pulmonary vascular pressures of strenuously exercising Thoroughbreds after administration of varying doses of frusemide

The frusemide dose-response for attenuation of exercise-induced pulmonary capillary hypertension was studied in 7 healthy, exercise-conditioned Thoroughbred horses using previously described haemodynamic procedures. Four different doses of frusemide were tested: 250 mg regardless of bodyweight (amounting to 0.56 +/- 0.03 mg/kg bwt), 1.0 mg/kg bwt, 1.5 mg/kg bwt and 2.0 mg/kg bwt. Frusemide was administered i.v., 4 h before exercise. Haemodynamic data were obtained at rest and during treadmill exercise performed at 14.2 m/s on a 3.5% uphill grade; this workload elicited maximal heart rate of horses. Airway endoscopy was performed post exercise to detect exercise-induced pulmonary haemorrhage (EIPH). In standing horses, frusemide administration resulted in a significant (P<0.05) decrease in mean pulmonary arterial, pulmonary capillary and pulmonary artery wedge pressures, but significant differences among the various frusemide doses were not observed. In the control experiments, exercise caused significant increments in the right atrial as well as pulmonary arterial, wedge, and capillary pressures, and all horses experienced EIPH. Following frusemide administration, the exercise-induced rise in right atrial and pulmonary vascular pressures was significantly attenuated, but significant differences between the frusemide doses of 250 mg, 1.0 mg/kg, and 1.5 mg/kg were not discerned and all horses remained positive for EIPH. Although a further significant (P<0.05) attenuation of the exercise-induced rise in pulmonary capillary blood pressure occurred when frusemide dose increased from 250 mg to 2.0 mg/kg bwt, all horses still experienced EIPH. It is concluded that a linear response to increasing frusemide dosage in terms of attenuation of the pulmonary capillary hypertension does not exist in strenuously exercising Thoroughbred horses.     

Bronchoalveolar lavage findings in horses with exercise intolerance.

Significant differences were detected by bronchoalveolar lavage (BAL) between horses racing successfully and those showing exercise intolerance. Neutrophil percentage, haemosiderophage percentage and total bacterial numbers were significantly elevated in horses with exercise intolerance. BAL provided a more accurate indication of the incidence and extent of exercise induced pulmonary haemorrhage (EIPH) than visual inspection.     

Effects of an external nasal strip and frusemide on pulmonary haemorrhage in Thoroughbreds following high-intensity exercise.

The purpose of this study was to examine the effects of an external nasal strip (NS), frusemide (FR) and a combination of the 2 treatments (NS + FR) on exercise-induced pulmonary haemorrhage (EIPH) in Thoroughbred horses. It was hypothesised that both the NS and FR would attenuate EIPH as assessed by red blood cell count in bronchoalveolar lavage fluid. In random order, 8 horses completed each of 4 sprint exercise tests on a treadmill: 1) NS; 2) FR (0.5 mg/kg bwt i.v., 4 h pre-exercise); 3) NS + FR; and 4) control (C; no treatment). After a 5 min warm-up (4.5 m/s), horses completed 2 min running at 120% maximum oxygen consumption (VO2max) with the treadmill set at 3 degrees incline. Mean +/- s.d. running speed was 14.2+/-0.2 m/s. In the FR and NS + FR trials, horses carried weight equal to that lost as a result of frusemide administration. During exercise at 120% Vo2max, oxygen consumption (Vo2) and carbon dioxide production (Vco2) were measured at 15 s intervals. Plasma lactate concentration was measured in samples collected before exercise, at the end of the sprint and after 5 min cool-down at the trot. Thirty minutes after the run, bronchoalveolar lavage (BAL) was performed and the red cell count in the fluid quantified. Vo2 and Vco2 were significantly lower in NS and NS + FR trials than in the C and FR trials at the end of the sprint exercise protocol. However, plasma lactate concentrations did not differ among treatments. Compared with the C trial (61.1+/-30.5 x 10(6) red blood cells/ml BAL fluid), pulmonary haemorrhage was significantly (P<0.05) decreased in both the NS (15.9+/-4.0 x 106 RBC/ml) and FR (12.2+/-5.8 x 10(6) RBC/ml) trials. EIPH in the NS + FR trial (7.9+/-1.0 x 10(6) RBC/ml) was further diminished (P<0.05) compared to the NS trial, but not different from the FR trial. We conclude that both the external nasal strip and frusemide attenuate pulmonary haemorrhage in Thoroughbred horses during high-speed sprint exercise. The external nasal strip appears to lower the metabolic cost of supramaximal exertion in horses. Given the purported ergogenic effects of frusemide, the external nasal strip is a valuable alternative for the attenuation of EIPH.     

Bronchoalveolar lavage cytology in cynomolgus monkeys and identification of cytologic alterations following sequential saline lavage

Total and differential cell counts were determined on cytolytic specimens obtained by fiberoptic bronchoscopy and bronchoalveolar lavage (BAL) of five normal cynomolgus monkeys. Total nucleated cell counts ranged from 100 to 430 cells/microliters. Macrophages were approximately 91% of total nucleated cells, while lymphocytes were 3%, neutrophils 4%, and eosinophils 2% of the initial BAL from each monkey. Less than 1% of the cells were mast cells and ciliated or nonciliated epithelial cells. The effects of repeated saline BAL on pulmonary cell populations were evaluated. Saline lavage of individual lung lobes resulted in a marked rise in circulating blood neutrophils at 4 hr after BAL; there was a similar rise in neutrophils in lavage fluids 24 hr after the initial lavage. Differential and total cell counts of both blood and lavage fluid returned to normal if subsequent lavages were spaced at 48-hr intervals. Lymphocytes were not present in saline-lavaged lung lobes, and protein levels of lavage fluids did not rise significantly. BAL produced a transient, reversible, intra-alveolar influx of neutrophils which was preceded by mobilization of bone marrow-stored neutrophils. Neutrophilia in the lavage fluid and blood was not detectable if lavage and blood sampling procedures were done at 48-hr intervals (which did not alter Ia antigen expression among BAL cells). These observations indicate that BAL is a valid method for sampling and assessing pulmonary cellular and fluid constituents if the procedures are done at intervals of at least 48 hr.     

Pulmonary response to airway instillation of autologous blood in horses

REASONS FOR PERFORMING STUDY: Exercise-induced pulmonary haemorrhage (EIPH) occurs in the majority of horses performing strenuous exercise. Associated pulmonary lesions include alveolar and airway wall fibrosis, which may enhance the severity of EIPH. Further work is required to understand the pulmonary response to blood in the equine airways. OBJECTIVES: To confirm that a single instillation of autologous blood into horse airways is associated with alveolar wall fibrosis, and to determine if blood in the airways is also associated with peribronchiolar fibrosis. METHODS: Paired regions of each lung were inoculated with blood or saline at 14 and 7 days, and 48, 24 and 6 h before euthanasia. Resulting lesions were described histologically and alveolar and airway wall collagen was quantified. RESULTS: The main lesion observed on histology was hypertrophy and hyperplasia of type II pneumocytes at 7 days after blood instillation. This lesion was no longer present at 14 days. There were no significant effects of lung region, treatment (saline or autologous blood instillation), nor significant treatment-time interactions in the amount of collagen in the interstitium or in the peribronchial regions. CONCLUSION: A single instillation of autologous blood in lung regions is not associated with pulmonary fibrosis. POTENTIAL RELEVANCE: Pulmonary fibrosis and lung remodelling, characteristic of EIPH, are important because these lesions may enhance the severity of bleeding during exercise. A single instillation of autologous blood in the airspaces of the lung is not associated with pulmonary fibrosis. Therefore the pulmonary fibrosis described in EIPH must have other causes, such as repetitive bleeds, or the presence of blood in the pulmonary interstitium in addition to the airspaces. Prevention of pulmonary fibrosis through therapeutic intervention requires a better understanding of these mechanisms.     

Effects of extrathoracic airway obstruction on intrathoracic pressure and pulmonary artery pressure in exercising horses

OBJECTIVE: To determine whether dorsal displacement of the soft palate (DDSP) results in pulmonary artery hypertension and leads to increases in transmural pulmonary artery pressure (TPAP); to determine whether pulmonary hypertension can be prevented by prior administration of furosemide; and to determine whether tracheostomy reduces pulmonary hypertension. ANIMALS: 7 healthy horses. PROCEDURE: Horses were subjected to 3 conditions (control conditions, conditions after induction of DDSP, and conditions after tracheostomy). Horses were evaluated during exercise after being given saline (0.9% NaCl) solution or furosemide. RESULTS: Controlling for drug, horse, and speed of treadmill, DDSP-induced increase in intrathoracic pressure was associated with a significant increase in minimum (36 mm Hg), mean (82 mm Hg), and maximum (141 mm Hg) pulmonary artery pressure, compared with values for control horses (30, 75, and 132 mm Hg, respectively). Increases in pulmonary artery pressure did not induce concomitant increases in TPAP. Tracheostomy led to a significant reduction of minimum (53 mm Hg), and mean (79 mm Hg) TPAP pressure, compared with values for control horses (56 and 83 mm Hg, respectively). When adjusted for horse, speed of treadmill, and type of obstruction, all aspects of the pulmonary artery and TPAP curves were significantly decreased after administration of furosemide, compared with those for horses given saline (0.9% NaCl) solution. CONCLUSIONS: DDSP was associated with increases in pulmonary artery pressure but not with increases in TPAP. CLINICAL RELEVANCE: Expiratory obstructions such as DDSP are likely to result in pulmonary hypertension during strenuous exercise, but may not have a role in the pathogenesis of exercise-induced pulmonary hemorrhage.     

Effects of furosemide on the racing times of horses with exercise-induced pulmonary hemorrhage

In 3 groups of horses with exercise-induced pulmonary hemorrhage (EIPH), comparisons of racing times and finishing positions were made between the 5 races before the horses were given furosemide and 5 races after furosemide administration. The horses were grouped according to 3 methods used to diagnose EIPH: group 1, observation of hemorrhage at the nostrils within 1 hour after a workout or race; group 2, observation of pulmonary hemorrhage only by endoscopic examination after a race or workout; and group 3, observation of hemorrhage at the nostrils during a race or immediately after a race. Group 4 horses were randomly selected horses running during the study period and were not given furosemide. The statistical method was analysis of covariance and the dependent variable was horses' time per distance. The study compared the 4 groups of horses, using the estimated value of the horses (less than or equal to +10,000 or greater than +10,000), and the horses' interaction in races 1 through 5 before and races 6 through 10 after furosemide treatment. The horses' times were adjusted by the relevant covariates, distance, track variant, and winning time per distance. Significant changes in horses' time per distance were not noticed when comparing values from races 1 through 5 with those in races 6 through 10 in group 1 horses.(ABSTRACT TRUNCATED AT 250 WORDS)     

Inclined running increases pulmonary haemorrhage in the Thoroughbred horse

REASONS FOR PERFORMING STUDY: Capillary stress failure-induced (exercise-induced) pulmonary haemorrhage (EIPH) during intense running in horses is thought to involve both intravascular (i.e. mean pulmonary arterial pressure [Ppa] > 100 mmHg) and extravascular (e.g. negative inspiratory pressure swings) mechanisms. HYPOTHESIS: That inclined running would reduce breathing frequency (coupled to stride frequency) and increase tidal volume thus increasing lung volume changes and intrapleural pressure swings resulting in more pronounced EIPH. METHODS: Six Thoroughbred horses were run to volitional fatigue (incremental step test) on a level (L) and inclined (I; 10%) treadmill in random order. Pulmonary minute ventilation, arterial blood gases and mean Ppa were obtained during each run while EIPH severity was quantified via bronchoalveolar lavage (BAL) 30 mins post run. RESULTS: Time to fatigue did not differ between trials (P > 0.05). At end-exercise, breathing frequency was reduced (L, 127.8 +/- 3.0; I, 122.6 +/- 2.1 breaths/min; P < 0.05) and tidal volume increased (L, 11.5 +/- 0.6; I, 13.1 +/- 0.5 L; P < 0.05) during inclined running. No differences existed in end-exercise plasma [lactate] between trials (L, 24.5 +/- 2.9; I, 26.2 +/- 3.4 mmol/l, P > 0.05); however, the mean peak Ppa was reduced during the inclined run (L, 105+5; I, 96 +/- 4 mmHg, P < 0.05). In the face of reduced Ppa, EIPH severity was increased significantly (P < 0.05) during the inclined vs. level run (L, 37.0 +/- 11.7; I, 49.6 +/- 17.0 x 10(6) red blood cells/ml BAL fluid). CONCLUSIONS: Although inclined running lowered peak Ppa, EIPH severity was increased. It is likely that this effect resulted, in part, from an altered ventilatory pattern (i.e. increased tidal volumes and associated intrapleural pressure changes). POTENTIAL RELEVANCE: This conclusion supports an important role for extravascular factors in the aetiology of EIPH.     

Association between exercise-induced pulmonary hemorrhage and performance in Thoroughbred racehorses

OBJECTIVE: To determine whether exercise-induced pulmonary hemorrhage (EIPH) was associated with racing performance inThoroughbred horses not medicated with furosemide and not using nasal dilator strips. DESIGN: Observational cross-sectional study. ANIMALS: 744 two- to 10-year-old Thoroughbred horses racing in Melbourne, Australia. PROCEDURE: Horses were enrolled prior to racing, and a tracheobronchoscopic examination was performed after 1 race. Examinations were recorded on videotape, and presence and severity (grade 0 to 4) of EIPH were subsequently determined by 3 observers blinded to the horses' identity. Race records were abstracted for each horse examined. RESULTS: Overall, 52.1% of horses eligible for participation in the study were examined, and horses that were examined did not differ from horses that were not examined in regard to age, sex distribution, or proportion of horses that won or finished in the first 3 positions. Horses with EIPH grades < 1 were 4.0 times as likely to win, 1.8 times as likely to finish in the first 3 positions, and 3.03 times as likely to be in the 90th percentile or higher for race earnings as were horses with grades > 2. Horses with EIPH grades > 1 finished significantly farther behind the winner than did horses without EIPH. However, odds that horses with grade 1 EIPH would win or finish in the first 3 positions were not significantly different from odds for horses without EIPH. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that EIPH is associated with impaired performance in Thoroughbred racehorses not medicated with furosemide and not using nasal dilator strips.