By Michael Mahaffey. Read Part 1 of this article here.
Furosemide, better known by its brand name, Lasix (or Salix), is a powerful diuretic and is the most commonly used treatment in the U.S. and Canada. According to research studies, this can have a major effect on a horse, causing it to lose up to 2.4 percent of its total body weight through urine excretion, resulting in lower blood pressures in the horse’s system.
The research has shown that Lasix can help reduce the severity of the bleed, potentially as much as 70 percent, but it does not stop or prevent bleeding.
“In our lab, we found that it was effective, and it’s dependent on level of intensity of exercise,” says Dr. Tammi Epp, a researcher at Kansas State University. “At a lower level of intensity, it seems to be more effective than at a higher level of intensity. For example, we found it to be around 90 percent effective at just under maximal exercise, and only 50 percent effective at maximal exercise.”
Barrel racer Jolene Montgomery says she doesn’t treat her horses unless she suspects they are going to bleed or they have previously.
“The ones that have bled before, I don’t take any chances,” Montgomery says. “I always run them on Lasix. As long as they’re not showing any other symptoms, I don’t have them scoped again. If you’re running them on a low dose of Lasix, and you suspect that they may have bled through it, then you’d want to have them scoped again.
“My veterinarian tells me there’s no substitute for Lasix, really,” she says. “If they’re bad bleeders, Lasix is always going to work.”
Dr. Howard Erickson, a professor of physiology at Kansas State University, who has conducted many studies into the causes and treatment of EIPH, says the main concern most have about the use of Lasix is its potential to cause dehydration in horses, in the short term, as well as its potential to cause depletion of electrolytes.
Dr. Tom Hutchins, a veterinarian at Equine Sports Medicine and Surgery in Weatherford, Texas, says the key thing with the use of Lasix is to make sure that horses stay well hydrated to counteract the diuretic effect.
Montgomery says as long as her horses are drinking after racing, there really doesn’t seem to be a problem. She says she will give them some extra B12 occasionally, but as long as they’re eating good, high quality feed, and they get plenty of water, she hasn’t seen any side effects from using Lasix.
The use of nasal dilator strips is another treatment option available for those who do not like the idea of injecting their horses with Lasix or other medications.
Epp says because horses are obligate nasal breathers, they experience some level of nasal collapse during heavy exercise, resulting in a reduction in airway size and causing a horse to work harder to get oxygen.
Erickson says nasal strips don’t work on the vascular pressure as much as it works on the airway. He believes the nasal strip is a valuable alternative for attenuation of EIPH given the purported ergogenic effects of Lasix.
“There’s a part of the nasal passage that’s not supported by bone, and when a horse inhales, that constricts in,” he says. “That creates large negative airway pressures down within the pulmonary circulation, and that tends to cause rupture of the capillaries.
“We have confirmed the benefit in particularly heavy bleeders. Horses wearing the nasal strip returned quicker to competition than horses that did not.”
A study published in the November 2001 Equine Veterinary Journal conducted by Kentucky Equine Research, Inc., showed that the external nasal strip appears to lower metabolic cost of extreme exercise in horses.
“We found that it allows the horses to breathe the same amount of air,” Epp says, “but their respiratory muscles don’t need to work as hard to do that because of the dilation of the nasal passages, so that allows more oxygen to go to the working muscles.”
Results of a University of California at Davis study conducted by Sandra Valdez found that the heaviest bleeders showed the most improvement when using nasal strips.
“The nasal strip was kind of the opposite of Lasix,” Epp says. “It was about 33 percent effective at a lower level of exercise, and as the horses began to work harder, it became about 50 percent effective, so it became more effective as the horses worked harder.”
Concentrated Equine Serum, also called Seramune, is a product used to treat Failure of Passive Transfer in foals that many veterinarians are now using to treat EIPH, Erickson says. CES is a product taken from several draft horse donors that contains high levels of immunoglobins and other serum proteins.
CES resulted in a 53 percent reduction of red blood cells and a 32 percent reduction in white blood cells, according to BAL results, Erickson says.
Based on results of a study he conducted at Kansas State that CES may have an immuno-modulatory effect and anti-inflammatory effects that are beneficial in the reduction small airway disease, which could be one of the causes of EIPH. It may also improve the healing of lung tissue and reduce scar formation.
Epp says according to the study, CES reduces bleeding by about 50 percent, most likely through the reduction of inflammatory airway disease.
However, CES took between two to three months to have a measurable effect.
“We think there are some things internally that have to occur for that to be beneficial and take effect,” she says.
Hutchins says it’s the extended use of CES before any benefit is seen that likely makes it something that most people would choose not to use.
“It’s one of those things that sort of becomes an inconvenience issue because it takes a fairly large dose to try to be effective,” he says. “The volume that you need to administer and use, I think, can start to be a costly venture for one, and two can be a hassle.”
A more affordable and readily available treatment that can potentially achieve the same effects as CES are feeds that are fortified with the proper concentrations of Omega-3 fatty acids.
“They tend to affect the vascular system, make vessels more flexible and easier for red blood cells to go through the capillaries, and so forth,” Erickson says. “And there’s some evidence that this product may help prevent EIPH, as well, so diet might be beneficial.”
There are several mechanisms through which Omega-3s may work. It may be by reducing inflammatory airway disease, or it may affect saturation of the membrane fluidity of not only the red cells, but maybe the vessels as well, to make them more elastic instead of more prone to tearing and rupture during high levels of exercise.
Erickson says it wasn’t known yet what combination of Omega-3s were most effective.
“You need a certain concentration and a certain ratio of those for it to be effective,” Epp says.
Hutchins says most commercially available feeds designed for performance horses are already rich in Omega-3s, and that blindly adding more is not necessarily the best thing an owner could do.
Epp is currently working with a feed company to produce a line of feed with the proper ratios of Omega-3’s to solve this problem.
“We found that with some concentrations and ratios, we did not have an effect, and with other ones we did,” Epp says, “so that’s why the concentration and ratio of the particular Omega-3 fatty acids is critical.”
Like CES, the Omega-3s take an extended period of time to have an effect. Epp says the anti-inflammatory treatments could potentially become a prophylactic use if people started horses on Omega-3s before they went into race training.
“Maybe we could reduce the level that these horses would bleed if they had not been put on these things,” she says.
After Lasix, Aminocaproic acid, also called Amicar, is one of the most widely used treatments for the reduction of EIPH.
It is an anti-fibrinolytic drug, Hutchins says, and the idea behind the use is if a horse does have an active bleed, the drug enhances the clotting factor, so horses don’t hemorrhage as much.
“It’s not really going to change the hemodynamics of the horse until they bleed,” he says, “and then it’s going to be effective.”
One major drawback to using Aminocaproic acid is its short half-life, Hutchins says. He has used it on several barrel horses, with no untoward side effects, but riders have to administer it almost every time they run.
Epp says when they studied Aminocaproic acid, they found that it does have anti-inflammatory properties, though it didn’t significantly decrease EIPH. There was only a slight reduction in bleeding, one much less significant that was achieved using Lasix or nasal strips.
“In fact, we had heard from track veterinarians that horses that run on Aminocaproic acid seem to not run as well, and that is what we found in our study,” she says.
They found that horses ran to a stage less, or they ran less time or not quite as fast as the horses on control, so they kind of confirmed what track veterinarians had suspected.
Erickson and Epp both say researchers believe the clotting and coagulation effects of Aminocaproic acid played a part in the slower times. Erickson says it also helped explain the trend toward earlier fatigue in horses using the drug.
“It’s been shown coagulation is not a factor in these exercising horses or in EIPH,” Epp says, “so if you’re enhancing coagulation, it could cause more problems.”
In the same study, Epp says they looked at Conjugated Equine Estrogens, commonly sold under the name Premarin, and found nearly identical results to Aminocaproic acid. The conjugated estrogens did reduce inflammation, though it didn’t decrease bleeding, and the expense of the conjugated estrogens, tended to make their use prohibitive.
“If you look in the literature on that,” Hutchins says, “they do think there is some benefit there to try to help with membrane permeability and to try to reduce those capillary beds from rupturing. We do use a fair amount of it on the racetrack, but not so much for the layperson.”
Another more controversial, and potentially dangerous, treatment is the use of nitric oxide gas inhalants.
Nitric oxide works as a vasodilator, giving blood vessels a larger circumference, and as a vascular smooth muscle relaxant. This allows vessels in the lungs to have the capacity to handle the increased pressures in a horse’s lungs during strenuous exercise, without the potential tearing or rupturing of capillaries in the lungs.
“We observed that even though the capillary pressure decreased a little bit, the bleeding actually increased,” Erickson says.
While Hutchins says his practice never uses nitric oxide, they do use other types of inhalant medications, but usually only to treat the most severe cases of bleeding once they have occurred. They also use inhalant steroids and bronchodilators. A short-acting bronchodilator, containing albuterol, is administered, and then immediately after, they administer inhalant corticosteroids.
“That way you’ve go the lung dilated,” he says. “You’ve got everything opened up, so the steroid can pass deep into the airway.”
Although the treatments are costly, from $225 to $300 per inhaler, if you had a horse that hemorrhaged significantly, and you wanted to try to get it cleared up quickly.
“Along with administration of antibiotics, those inhalant steroids and bronchodilators are a great tool because it gets the particle size of the medicine down to a small enough particle that it actually gets into those airsacs where a lot of other things don’t,” Hutchins says.
Michael Mahaffey is associate editor of Barrel Horse News. Send comments on this article to [email protected].