Intravenous pentoxifylline does not enhance the pulmonary haemodynamic efficacy of frusemide in strenuously exercising thoroughbred horses

Racetrack exercise vs treadmill exercise with respect to exercise-induced pulmonary haemorrhage (EIPH): implications for studies of putative treatments of EIPH

Multiple treadmill-based studies using low numbers of horses have evaluated potential prophylactic treatments for exercise-induced pulmonary haemorrhage (EIPH) and found no effect. However, the relevance of these findings to racing is unclear. Because severity of EIPH incurred on treadmills has not been compared to that following high-speed racetrack exercise in the same horses, we retrospectively performed this comparison using bronchoalveolar lavage fluid red cell numbers (BALFRBC) due to the relative insensitivity of tracheobronchoscopy. Six race-fit Thoroughbreds with recent tracheobronchoscopic EIPH scores ≥2 were exercised to fatigue on a treadmill at 115% V̇O2max (5% incline, 12.3-14.2 m/s), and maximally on a racetrack over 800 m and 1,100 m with average speeds ranging from 16.4-16.7 and 15.5-16.6 m/s, respectively. Run order varied but was not randomised. Bronchoalveolar lavage (BAL) was performed blindly using Bivona tubes 45-60 mins post-exercise. BALFRBC were determined using a haemocytometer. Data were expressed as median and interquartile range, and analysed using RM ANOVA with significance set at P<0.05. BALFRBC were greater after both racetrack runs than after treadmill exercise (P<0.05; treadmill: 10,305/μl (3,871-26,079); 800m: 25,000/μl (17,175-73,400); 1,100m: 19,500/μl (8,962-800,600). Treadmill exercise resulted in lower numbers and a narrower range in BALFRBC than racetrack exercise. Thus, when a small number of horses is used to study EIPH treatments on a treadmill, a lower BALFRBC would be anticipated following the baseline run than with a similar study using racetrack exercise, and might reduce the likelihood of demonstrating significant treatment effects. Results of this retrospective study raise concern regarding the advisability of extrapolating conclusions regarding efficacy of EIPH treatments from treadmill studies to racetrack scenarios.

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.

Equine sweating and anhidrosis Part 1 ? equine sweating

Sweating has a variety of functions in mammals including pheromone action, excretion of waste products and maintenance of the skin surface ecosystem. In a small number of mammalian species, which includes humans and the Equidae, it also has an important role in thermoregulation. This review is focused specifically on the thermoregulatory role of sweat in Equidae and the causes of sweating failure (anhidrosis). The first part describes the glandular appearance, sweat composition, and output rates; and considers the latest theories on the glandular control and secretory mechanisms. It is concluded that the glands are not directly innervated but are controlled by the interplay of neural, humoral and paracrine factors. The secretory mechanism is not as simple as previously thought and is mediated by the dynamic interaction of activating pathways, including autocrine control not only of the secretory process but probably also of secretory cell reproduction, growth, and death.