Clenbuterol administration does not attenuate the exercise-induced pulmonary arterial, capillary or venous hypertension in strenuously exercising Thoroughbred horses

Inhibiting IL-6 in medicine: a new twist to sustain inhibition of his cytokine tin the therapy of Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is a chronic, progressive disease characterized by an increase in blood pressure in the lungs' arteries. It can occur in a variety of species, including humans, dogs, cats, and horses. To date, PAH has a high mortality rate in both veterinary and human medicine, often due to complications such as heart failure. The complex pathological mechanisms of PAH involve multiple cellular signalling pathways at various levels. IL-6 is a powerful pleiotropic cytokine that regulates several phases of immune response, inflammation, and tissue remodelling. The hypothesis of this study was that the use of an IL-6 antagonist in PAH could interrupt or mitigate the cascade of events that leads to the progression of the disease and the worsening of clinical outcome, as well as tissue remodelling. In this study, we used two pharmacological protocols with an IL-6 receptor antagonist in a monocrotaline-induced PAH model in rats. Our results showed that the use of an IL-6 receptor antagonist had a significant protective effect, ameliorating both haemodynamic parameters, lung and cardiac function, tissue remodelling, and the inflammation associated with PAH. The results of this study suggest that the inhibition IL-6 could be a useful pharmacological strategy in PAH, in both human and veterinary medicine.

Exercise-induced pulmonary hemorrhage in barrel racing horses in the Pacific Northwest region of the United States

Background

Exercise‐induced pulmonary hemorrhage (EIPH) refers to bleeding from the lungs in association with strenuous exercise. It has been documented in race horses but little information exists on EIPH in barrel racing horses.

Hypothesis/Objectives

Our goals were to evaluate the presence of EIPH in barrel racing horses and estimate its prevalence in the Pacific Northwest.

Animals

149 barrel racing horses enrolled at events in WA (11), ID (3), and MT (33).

Methods

Observational cross‐sectional study. Data collected included signalment, history of illness, respiratory disease, race division, and pre‐race medications. Endoscopy was performed and tracheobronchoscopic (TBE) EIPH score was assigned based on quantity of blood in the trachea (0 = no blood to 4 = abundance of blood within the trachea). After TBE, bronchoalveolar lavage (BAL) was performed. Erythrocyte (red blood cell, RBC) counts were obtained from bronchoalveolar lavage fluid (BALF). Statistical analysis included linear and logistic regression, Fisher's exact t test, and calculation of correlation coefficient. Significance was set at P < .05.

Results

The prevalence of EIPH based on TBE EIPH score was 54%. When based on BALF RBC count >1,000 cells, EIPH prevalence was 66%. Race time did not significantly affect the presence of EIPH. A significant (P < .0001) positive linear relationship between the TBE and BAL erythrocyte count was identified, but its strength was poor (r² = .15).

Conclusions and Clinical Importance

EIPH occurs in over 50% of barrel racing horses in the Pacific Northwest. Precise determination of the impact of EIPH on health of barrel racers requires further study.

Development of a technique for determination of pulmonary artery pulse wave velocity in horses

Calcification of the tunica media of the axial pulmonary arteries (PA) has been reported in a large proportion of racehorses. In humans, medial calcification is a significant cause of arterial stiffening and is implicated in the pathogenesis of cardiac, cerebral, and renal microvascular diseases. Pulse wave velocity (PWV) provides a measure of arterial stiffness. This study aimed to develop a technique to determine PA-PWV in horses and, secondarily, to investigate a potential association between PA-PWV and arterial fibro-calcification. A dual-pressure sensor catheter (PSC) was placed in the main PA of 10 sedated horses. The pressure waves were used to determine PWV along the PA, using the statistical phase offset method. Histological analysis of the PA was performed to investigate the presence of fibro-calcified lesions. The mean (±SD) PWV was 2.3 ± 0.7 m/s in the proximal PA trunk and 1.1 ± 0.1 m/s further distal (15 cm) in a main PA branch. The mean (±SD) of mean arterial pressures in the proximal PA trunk was 30.1 ± 5.2 mmHg, and 22.0 ± 6.0 mmHg further distal (15 cm) within the main PA branch. The mean (±SD) pulse pressure in the proximal PA trunk was 15.0 ± 4.7 mmHg, and 13.5 ± 3.3 mmHg further distal (15 cm) within the main PA branch. Moderate to severe lesions of the tunica media of the PAs were observed in seven horses, but a correlation with PWV could not be established yet. Pulmonary artery PWV may be determined in standing horses. The technique described may allow further investigation of the effect of calcification of large PAs in the pathogenesis of equine pulmonary circulatory disorders.NEW & NOTEWORTHY Pulmonary artery pulse wave velocity was determined safely in standing sedated horses. The technique described may allow further investigation of the effect of calcification of large pulmonary arteries in the pathogenesis of pulmonary circulatory disorders in horses.

Exercise induced pulmonary hemorrhage in horses: American College of Veterinary Internal Medicine consensus statement

Background

Published studies of exercise‐induced pulmonary hemorrhage (EIPH), when assessed individually, often provide equivocal or conflicting results. Systematic reviews aggregate evidence from individual studies to provide a global assessment of the quality of evidence and to inform recommendations.

Objectives

Evaluate evidence to determine: if EIPH adversely affects the health, welfare or both of horses; if EIPH affects the athletic capacity of horses; the efficacy of prophylactic interventions for EIPH; and if furosemide affects the athletic capacity of horses.

Animals

None.

Materials and Methods

Systematic review. A panel of 7 experts was formed to assess evidence in the peer reviewed literature addressing each of the 4 objectives. Methodology followed that of the Grading of Recommendations, Assessment, Development, and Evaluation (GRADE). Publications were assessed for quality of evidence by working groups of the panel, and a summary of findings was presented in tables. Recommendations were based on quality of evidence and were determined by a vote of the panel.

Results

Much of the evidence was of low to very low quality. Experimental studies frequently lacked adequate statistical power. There was moderate to high quality evidence that EIPH is progressive, is associated with lung lesions, that it adversely affects racing performance, that severe EIPH (Grade 4) is associated with a shorter career duration, that furosemide is efficacious in decreasing the incidence and severity of EIPH, and that administration of furosemide is associated with superior race performance.

Conclusions and clinical significance

Strong recommendation that EIPH be considered a disease and a weak recommendation for use of furosemide in management of racehorses with EIPH.

The effect of sildenafil citrate administration on selected physiological parameters of exercising Thoroughbred horses

REASONS FOR PERFORMING STUDY

Sildenafil, a phosphodiesterase-5 inhibitor vasodilator, increases cGMP concentrations by inhibiting enzymatic degradation. Marketed to treat erectile dysfunction in men, it also reduces pulmonary arterial pressure (PAP). Because it reduces PAP, sildenafil may enhance performance and/or prevent exercise induced-pulmonary haemorrhage (EIPH).

OBJECTIVE

To determine if sildenafil citrate administration altered commonly measured indices of performance or reduced EIPH in exercised horses.

METHODS

Thirteen athletically conditioned Thoroughbred horses (2 mares and 11 geldings, age 3-12 years) were administered sildenafil citrate or placebo in 2 crossover design exercise testing studies. In a step-wise test to exhaustion, inspired/expired gas analysis, blood lactate, heart rate, runtime and bronchoalveolar lavage (BAL) cytology were measured. In a 13 m/s test to exhaustion, blood lactate, heart rate, runtime, BAL cytology and pulmonary arterial pressure were measured. Data were analysed with paired and unpaired t tests, one-way ANOVA and Tukey's pair-wise multiple comparison and Friedman repeated measure analysis of variance on ranks.

RESULTS

The administration of sildenafil did not alter mean inspired/expired gas measurements, plasma lactate concentrations or acute pulmonary haemorrhage in either exercise test or pulmonary arterial pressure measurement in the 13 m/s trial. Heart rates in both stress tests were significantly different at submaximal speeds and during the early recovery period. Run time was not affected by sildenafil administration in the step-wise trial (P = 0.622) or in the 13 m/s trial (P = 0.059).

CONCLUSIONS

Sildenafil did not alleviate pulmonary haemorrhage or enhance performance-related indices in these trials. Sildenafil administration altered cardiovascular adaptation to intense exercise as evidenced by altered heart rates at submaximal speeds and post exercise. The effect of these alterations on other performance perimeters was not evident.