Exercise Induced Pulmonary Hemorrhage (EIPH)

A certain amount of pulmonary hemorrhage, which is bleeding in the lungs, can occur in any horse engaged in fast or intense exercise. The amount of bleeding can range from just a few red blood cells, detectable only by sensitive tests such as a bronchoalveolar lavage (BAL), to the much more obvious nosebleed. The greater the severity of EIPH, the more the horse’s health is affected. Blood in the lungs acts as an irritant resulting in inflammation, and also creates an ideal breeding ground for bacteria.

The most widely accepted theory about the cause of EIPH is that the high blood pressure from heavy exercise coupled with vacuum-like effects that occur during a deep inhalation causes the capillaries to rupture. The only gap in this theory is that it does not explain why almost all of the bleeding occurs in the upper back lobes of the lungs rather than uniformly throughout.

Another theory that helps to explain the location of the bleeding focuses on the anatomy of the running horse. Since a horse’s forelegs are not attached to the spine with any bony structures, the action of running causes the shoulders to compress the ribcage. This wave of pressure then spreads outwards causing a shearing force on the tissue in the upper back of the lungs, resulting in bleeding. This type of hemorrhage is similar to the bleeding that occurs from a blunt trauma to the front of the chest or head—that is, the bleeding does not occur at the location of the trauma but on the opposite side of the body. This theory might explain why some horses are more likely to bleed after running on a hard surface, and why some “bleeders” do not respond to Lasix (furosemide).

I have my own additional theory as to why horses bleed. I feel that EIPH occurs because of weakened capillaries secondary to inadequate nutrition. Just as some people bruise easily, some horses bleed easily. The bleeding in horses, however, does not go into the tissues but moves instead into the airways. Many horses also have thick, toxic, and poorly oxygenated blood due to repeated exposure to chemicals and drugs, causing the heart to work harder and the blood pressure to rise. This increased arterial blood pressure, with or without weakened capillary walls, sets the stage for EIPH.

To definitively diagnose and determine the severity of EIPH it is best to do an endoscopic exam 30 minutes to one hour following intense exercise. A sample scoring system for diagnosing EIPH might include the following grades:

Grade 1: Flecks of blood in the trachea.

Grade 2: More blood than Grade 1, but less than a continuous stream.

Grade 3: A continuous stream smaller than half the tracheal width.

Grade 4: A continuous stream greater than half the tracheal width.

Grade 5: Airways awash with blood.

Treatment and Prevention of EIPH

For many horses, 250 to 500 milligrams of Lasix (a potent diuretic) given one to four hours before a race will reduce blood pressure and prevent bleeding. For a significant number of other horses, however, Lasix is ineffective. In these cases it may be worth looking into the concussion theory as a cause of bleeding. While hard ground is certainly a factor in these cases, I suspect that many of these horses also run with a greater percentage of their weight on the forehand rather than working off the hindquarters.

Another factor to consider is upper airway resistance caused by the combination of blood pressure and inhalation vacuum pressure. Conditions such as laryngeal hemiplegia (a whistling or roaring that can be heard when the horse is breathing deeply from exertion), dorsal displacement of the soft palate, nasal, pharyngeal (at the back of the throat) or tracheal collapse, guttural pouch disease, excessive head flexion, or pharyngeal inflammation could cause an increase of the pressure in the lungs during inhalation . Treating any of these conditions would remove the underlying cause and may remedy the bleeding.

Herbal supplements can be useful in preventing EIPH. Many herbal supplements contain vitamin C and bioflavonoids, both of which support capillary integrity. Also useful are supplements that have mullein, yarrow, and lungwort, which reduce inflammation and strengthen weakened tissue, and shepherd’s purse, which has coagulant factors. While I do not believe that a primary deficiency of clotting factors is the cause of EIPH, these clotting factors can be depleted by frequent bleeding episodes.

You can keep your horse’s blood clean and well oxygenated with careful management that includes:

Feeding whole food nutrition that includes supplements such as probiotics, antioxidants, and blue- green algae.

Avoiding drugs, excessive vaccination, and chemicals.

Lasix is the most effective preventative for EIPH for horses that respond to it, but it is still important to explore all the possible factors that might cause your horse to bleed. Make every effort to keep your horse as healthy as possible, but do not risk a severe episode of bleeding by withholding Lasix if you know it to be effective for your horse. In order to receive the full benefit of the diuretic action of Lasix, water must be withheld between giving the dose and the time of intense exertion. Therefore, as soon as possible afterward, replenish your horse’s electrolytes and offer plenty of fresh, free-choice water to combat dehydration. Some research suggests that smaller doses given closer to the actual run (250 mg. one hour before a race) can be effective.