The Breeders’ Cup Forum: Lasix – A Racetrack Practitioner’s Perspective
Dr. Don Shields has been a Southern California racetrack practitioner for more than 25 years since his graduation from the University of California-Davis School of Veterinary Medicine in 1987.
While he has specialty training in diagnostic ultrasound and has performed numerous stem-cell and platelet rich plasma treatments to injured tendons and ligaments of horse, Dr. Shields is a staunch advocate for the use of furosemide, or Lasix, to treat exercise-induced pulmonary hemorrhage in horses.
He provided the following answers via email to questions on EIPH and methods to control it.
From your perspective as a racetrack equine practitioner, why do you think furosemide is the best way to treat exercise-induced pulmonary hemorrhage?
As with all professional sports, horse racing is a very strenuous activity. Exercise induced pulmonary hemorrhage (EIPH), or bleeding, is a common occurrence caused by the stresses encountered by our magnificent equine athletes during training and racing. Furosemide is currently the only medication which has been scientifically proven to decrease both the incidence and severity of EIPH. This beneficial effect of furosemide was clearly demonstrated in the landmark 2009 study by Drs. Hinchcliff, Morley and Guthrie.
While rest may allow the damaged lung time to heal the acute injury caused during EIPH, it has never been demonstrated to prevent future episodes of EIPH.
There are a number of adjunct medications that have been utilized in conjunction with furosemide in an attempt to further reduce EIPH. These adjuncts include medications such as conjugated estrogens, aminocaproic acid, tranexamic acid and carbazochrome. While numerous trainers and veterinarians believe they have seen a clinical effect with some of these adjuncts, none of these medications has yet been scientifically proven to be efficacious at decreasing EIPH. This fact does not mean these medications do not work. It must be noted that no adjunct medication has ever been tested in the same manner and utilizing the same study design that was employed by Drs. Hinchcliff, Morley and Guthrie, which clearly proved the efficacy of furosemide.
Hypothetically, if furosemide is banned on race-day, what would the possible results be?
We do not need to guess at what the possible impact to our equine athletes might be. The study by Drs. Hinchcliff, Morley and Guthrie clearly demonstrates that more horses will bleed more severely without the administration of furosemide. In this study, twice as many horses did not bleed at all when they were treated with furosemide. There were also no EIPH grades of 3 or 4 “bad bleeders” when horses were treated with furosemide; however, without furosemide bad bleeding (grades 3 & 4) occurred in about 12% of the horses.
Here is a chart demonstrating the grades of EIPH encountered during this study when horses raced with and without furosemide. The same 152 horses were examined endoscopically after racing once with furosemide and once without the administration of furosemide. The study is available online.
EIPH in furosemide treated horses EIPH in non-treated horses
GRADE Horses % GRADE Horses %
Grade 0 65 43 Grade 0 32 21
Grade 1 75 49 Grade 1 67 44
Grade 2 12 8 Grade 2 35 23
Grade 3 0 0 Grade 3 16 11
Grade 4 0 0 Grade 4 2 1
Studies have demonstrated that approximately 60% of the sudden deaths during racing have been attributed to pulmonary hemorrhage, EIPH grades of 2 or more have been shown to adversely affect racing performance, and EIPH is believed to adversely affect the overall health of racehorses. We know that EIPH is pathology, an injury to the lung of the horse, and that this injury causes further lung pathology. In his presentation to the participants at the International Summit on Race Day Medications, Dr. Robinson discussed the pathology caused by EIPH including interstitial fibrosis, septal wall thickening, venous wall remodeling and the infiltration of new blood vessels into the lung tissue. Studies have also shown that horses with EIPH have more severe exercise-induced hypoxemia (an inadequate level of oxygen in the blood) as compared to normal horses, suggesting that horses with EIPH have impaired lung function.
The administration of furosemide greatly reduces both the incidence and severity of significant bleeding. Significant bleeding is considered to occur with EIPH of grades of 2, 3 or 4 because these grades of EIPH negatively affect performance. Grade 1 EIPH has not been shown to have any negative effect on performance.
Do you have any estimates on the percentage of horses you endoscopically examine post-race (treated with furosemide) that show some signs of EIPH?
Lung function seems to be minimally affected or unaffected by small quantities of blood; however, quantities of blood above this low level negatively affect both lung function and racing performance as well as create lung pathology. It is far more accurate to discuss the levels of bleeding, the actual severity or grades of EIPH found post-race, rather than chatting about whether horses show some signs of EIPH. The fact that some signs of EIPH may still be evident in a large percentage of the horses treated with furosemide is meaningless without discussing the actual grades of the EIPH detected.
As is stated above, grade 1 EIPH has not been demonstrated to impact performance; however, EIPH of grades 2, 3 and 4 have been proven to negatively impact performance. Thus it is more important and accurate to discuss significant bleeding (EIPH grades 2 – 4) rather than any and all signs of EIPH no matter how miniscule. Using the data from the study, it is apparent that 53 of the 152 (35%) horses racing without furosemide bled significantly – a grade 2, 3 or 4. However, only 12 of the 152 (8%) horses bled a grade 2 when furosemide was administered prior to racing (there were NO grade 3 or 4 bad bleeders following furosemide treatment).
One single dose of furosemide reduced significant, race-affecting EIPH by 77%! This single administration of furosemide also doubled the number of horses that demonstrated no bleeding whatsoever from 32 of 152 horses (21%) without furosemide to 65 (43%) with it.
If we simply looked at any signs of post-race EIPH (grades 1 – 4), the study showed that 79% of horses racing without furosemide had evidence of EIPH and yet with furosemide 57% still had some evidence of EIPH. However, of that 57% that were treated with furosemide and still demonstrated some signs of EIPH, 86% of these bled a grade 1 and thus were likely unaffected by this low level of bleeding. This is why we need to be clear about what we are discussing and should focus on the grades of EIPH that have been shown to injure our equine athletes and affect their performance.
Have you found any difference in the percentage of Thoroughbreds that exhibit EIPH among top-class stakes horses and lower-level claiming horses?
I currently do not have enough of these top-class horses in my practice to provide statistics on this issue. If these class horses are worked and raced less often, their lungs may be less affected by previous bleeding episodes. Many other variables may also affect this statistic. The general veterinary care for these horses may be better, works may be longer but at a slower speed, furosemide may have been utilized preventatively more often, etc. Comparisons like these must take numerous variables into account to provide valid results.
In Europe and elsewhere, horses may train on furosemide but there is a withdrawal time and it is not permitted on race-day. Do you think that would work in the United States?
There are those who state that furosemide enhances performance, while others state that no amount of furosemide will allow a horse to run above its capabilities. It has been my experience that people training on furosemide are not trying to enhance the performance of their horse during a workout. Furosemide is being utilized because it has been proven to decrease both the incidence and severity of EIPH and thus to decrease or prevent injury to the lungs of the training horses. I must assume this fact is why horses may train on furosemide elsewhere.
If furosemide is medically beneficial to a horse during training, is it not just as medically beneficial during racing? Why is it morally, ethically and medically justifiable to allow injury to occur to our magnificent equine athletes when we know how to significantly lessen or prevent that injury? Millions of Americans take blood pressure medications daily and millions more take low-dose aspirin tablets to lessen or prevent the occurrence of numerous health issues including heart attacks and strokes. Medically speaking, it is far better to prevent injury and pathology than to try to heal it. We know how to greatly reduce the incidence and severity of EIPH and the attendant injury it causes. I believe it is unconscionable to allow injury to increase in incidence and severity when we know how to prevent this from happening.
It must also be acknowledged that diagnosing the incidence or severity of EIPH by looking for blood at the nostrils (epistaxis) is malpractice. The incidence of blood at the nostrils post-race has been published and is generally considered to be less than 1% of the racing population. As you would expect, the vast majority of horses suffering EIPH that results in epistaxis have bled badly (EIPH grades 3 or 4). According to the study above, roughly 12% of horses racing without furosemide will bleed badly (a grade 3 or 4). That means that looking for epistaxis to determine if a horse bled badly detects only 8% of the horses that actually did bleed badly, and yet this is often how regulatory sanctions are dispensed. Looking for epistaxis is simply an unfair way to dispense mandated rest and is never a medically sound way to diagnose the incidence or severity of EIPH.
As far as the betting public is concerned, working horses on furosemide and then racing without it may be providing very misleading information. If the study statistics hold, only 8% of horses racing on furosemide will suffer performance-affecting EIPH (grades 2 – 4) while 35% will race off-form due to significant EIPH when racing without furosemide. Which horses will bleed significantly and suffer form reversals in a particular race is anyone's guess, but referencing data from works with furosemide will further confuse the issue when racing without it.
Has your practice evolved philosophically regarding furosemide (i.e., initially prescribing furosemide to horses that scoped with some signs of EIPH in training, evolving to using it as a preventative medicine)? If so, why?
I have always believed that furosemide should be employed preventatively. We know that the vast majority of horses will suffer EIPH to some degree during their careers. In fact, the prevalence of EIPH in Thoroughbred and Standardbred racehorses approaches 80 – 100%. Although evidence of EIPH is not present following every race, when horses are scoped successively following several races, most have evidence of some level of pulmonary hemorrhage. We simply do not know which horses will bleed or how badly they'll bleed during any given race.
I firmly believe that it is medically sound and ethically preferable to lessen or prevent the injury to the horse's lungs caused by EIPH by administering furosemide.
What do you think may be the biggest misperception about furosemide?
Perhaps the biggest misconception is what continues to drive this entire issue. Is there really a medical question that still needs to be answered? I have spent quite some time providing you and your readers with scientific facts and medical knowledge regarding furosemide usage. What I have provided are exactly that, facts. The debate over whether furosemide greatly lessens the incidence and severity of EIPH and the attendant lung injury it causes has been settled. We have proof that furosemide works and works very well…and yet the controversy continues.
By administering furosemide to working and racing equine athletes we are lessening or preventing injury to their lungs. Is there a moral, ethical or medical debate over whether lessening or preventing injury to our equine athletes is the right thing to do? Can horses work and race without furosemide? Of course they can, they'll just suffer more injury and pathology than they would have if furosemide had been administered. People certainly can also stop taking low-dose aspirin and their blood pressure medications. The result in humans will also be an increase in injury and pathology. The utilization of therapeutic medications in a preventative fashion is intended to lessen or prevent injury and pathology. The pre-work/race administration of furosemide does exactly this by decreasing the incidence and severity of EIPH.
According to the study, horses racing without furosemide are likely to suffer performance-affecting EIPH roughly 35% of the time. Providing data from workouts utilizing furosemide while preventing its administration for racing should certainly further increase the number of horses racing off-form during any particular race. Thus furosemide administration is not only in the best interest of the horse as concerns its health, but its use also provides a consistency to the data provided to the betting public.
So if the medical questions of the efficacy of furosemide as well as its use in preventing or decreasing injuries sustained by our equine athletes have been definitively answered, then what is this controversy about? Perhaps it all boils down to money? There are those who believe that European and other world buyers will pay significantly higher prices for our horses if they are not running on furosemide. Is it moral, ethical, medically sound or even a good business practice to trade increased pulmonary injury and pathology to the lungs of our racehorses for the imagined increased profits to be reaped in the sales ring?
We certainly can race without furosemide, as long as we don't mind mandating an increase in the injury and pathology to be suffered by our equine athletes. For the record, I do mind and don't believe this course of action would be in the best interest of the horse.