Dr. Cliff Honnas, DVM, shares the basics of EIPH, a condition that affects many barrel horses.

Dr. Cliff Honnas, DVM, shares the basics of EIPH, a condition that affects many barrel horses and causes them to bleed after exercise.
It is not uncommon for horses operating at maximal effort to experience EIPH. Photo by Abigail Boatwright

When a horse finishes a race and afterward, blood starts dripping from its nostrils, it’s natural to feel concerned. Why did this happen? How can it be treated? How can it be prevented? Dr. Cliff Honnas DVM, DACVS, of Texas Equine Hospital in Bryan, Texas, shares valuable insight on exercise-induced pulmonary hemorrhage (EIPH), an unfortunately common occurrence in barrel horses.

What Causes a Horse to Bleed?

While there are different theories about what causes a horse to bleed post-exertion, Honnas says when a horse is giving maximum effort, they are sucking in as much air as possible to oxygenate their blood. That affects the pressure inside its thoracic cavity.

“When you take a breath, the negative pressure in your check cavity is what helps draw the air into your lungs,” Honnas said. “So when that negative pressure is maximal, at maximum exercise, then the capillaries and lung tissue are under such pressure that those capillaries can burst.”

If these capillaries burst, the blood flows into the alveoli, which Honnas says are the air sacs where the adjacent blood vessels transfer oxygen to the arteries.

“That blood in the alveoli then goes down into the bronchioles, and then to the bronchii, and then into the trachea, and if there’s enough bleeding, then the blood can come out the nose,” Honnas said. “It’s an overwhelming bleed that bled with enough pressure and force to fill all of those structures till the blood comes out the nose.”

Dr. Cliff Honnas, DVM, shares the basics of EIPH, a condition that affects many barrel horses and causes them to bleed after exercise.
If your horse is suspected to have exercise-induced pulmonary hemorrhage, a veterinarian will use an endoscope to look for evidence of blood in your horse’s respiratory system. Photo by Abigail Boatwright

Unfortunately, EIPH is a fairly common disease for barrel horses, says Honnas. Racehorses and ropers have also experienced this condition.

“Really, any athlete that is maximally exercising and trying to get as much air in their lungs as they can to sustain that exercise is at risk,” Honnas said.


When your horse’s nose is dripping blood, that’s an obvious symptom. But Honnas says not every bleeder has external evidence.

“One of the more common things we see is a horse that’s lost performance—they’re not doing their job like they had been,” Honnas said.

In those cases, a client may bring the horse in to the clinic, give the vet its history and then the veterinarian will conduct a lameness exam. Honnas says sometimes they’ll find accompanying lameness, but not always.

“That’s a way to get off on a rabbit trail and think lameness is what’s affecting the horse’s performance,” Honnas said. “When in fact, actually, they’re a bleeder that just hasn’t bled out of the nasal passages. So you can’t assess that unless you examine them fairly close to when they bled, before the body reabsorbs the blood.”


If you bring your horse to the veterinarian shortly after a barrel race to check for EIPH, Honnas says he’d give the horse a mild sedation and then will run an endoscope through the nostril, through the back of the throat, and then down the trachea into the bottom of the trachea and look for evidence of blood.

“My general rule of thumb is to try to scope them within 24 to 36 hours of maximal exercise,” Honnas said. “You can see telltale signs in the airway within 24 hours in most cases.”

Dr. Cliff Honnas, DVM, shares the basics of EIPH, a condition that affects many barrel horses and causes them to bleed after exercise.
An endoscope is passed through the nose and down into the trachea. Photo courtesy Dr. Honnas
The lower trachea where it branches into each lung. This is where blood is often seen on an endoscopy. Photo courtesy Dr. Honnas

If it’s been longer than 48 hours since the event and there’s still a concern that bleeding occurred, or if he sees signs of bleeding on the endoscope examination, Honnas will do a bronchoalveolar lavage, which consists of inserting a tube through the nostril down through one of the branches of the trachea, into the lungs, then flushing sterile fluid into the lung.

“We withdraw that fluid and send it to a lab, where they can see evidence of blood in some of the cells that eat those blood cells and try to clean up the airway,” Honnas said.


Once a horse bleeds, Honnas says the horse needs to be allowed to rest 10 days to two weeks to allow the capillaries time to heal.

Dr. Cliff Honnas, DVM, shares the basics of EIPH, a condition that affects many barrel horses and causes them to bleed after exercise.
If a veterinarian sees signs of bleeding on an endoscope examination, they may perform
a bronchoalveolar lavage, using this tool to flush fluid into your horse’s lungs and extract it. The resulting cells will be sent to a lab to look for evidence of blood. Photo by Abigail Boatwright

“If you run them back right away, the capillaries are like a cut on your skin where you have a scab,” Honnas said. “If you keep knocking the scab off, they’ll have a bit of a bleed there. Some horses, even at two weeks, they’re going to be prone to bleed. They could need an extended time off—three, four, five weeks or longer.”

If the horse bled extensively, that could foster a perfect medium for bacterial growth, so Honnas will typically put a horse with this condition on antibiotics for a week to 10 days.

Can Bleeding Be Prevented?

Right now, Honnas says the best method for EIPH prevention is to administer furosemide—brand name Lasix—2-4 hours before exercise. This diuretic drug increases urine output and thus reduces blood volume. In this way, Honnas says Lasix has been shown to reduce pulmonary capirllary blood pressure, decreasing the possibility of capillary rupture during maximal exercise.

“Depending on the veterinarian and depending on the horse, we will typically give them three to four CCs (millileters) two hours prior to the race,” Honnas said.

Some veterinarians, including Honnas, will suggest administering clenbuterol (Ventipulmin) to dilate the horse’s bronchial tubes so they can get more air flow and better gas exchanges for less negative pressure.

Honnas says some compounded medications can also be beneficial. “We start simple with Lasix, and hopefully get a good response,” Honnas said. “That’s typically going to be the main stage of treatment. We’ll add other things if the horse needs it.”

Although EIPH seems worrisome, Honnas says it’s not as concerning as you might think.
“It’s typically not life-threatening—it’s an exceedingly common disease in horses at the top of their game,” he said. Honnas says keeping your horse as fit as possible can help reduce its occurrence.

“Fitness is the key to prevent this from happening. Really ride and keep your horse fit throughout the week. If you’re not able to do that but you have the finances to afford it, take him to a rehab facility and let them AquaTread them to keep the lung capacity good and their muscles toned up so they don’t fatigue as much,” Honnas said. “Fitness is probably the best thing you can do to stay ahead of it.”

This article was originally published in the January 2022 issue of Barrel Horse News.


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