Bleeding from one nostril or both during or immediately following exercise is referred to as “Exercise Induced Pulmonary Hemorrhage (EIPH) or more commonly called a “bleeder”. Studies have shown that 90% of racehorses bleed to varying degrees in the lungs while only 2% will actually bleed through their nostrils. That means that the remaining 98% are “hidden bleeders” without exhibiting any external signs.
The severity of bleeding is related to exercise levels with the greatest risk being during times of excess exertion. In racehorses, bleeding most commonly occurs in the final stages of the race when maximal speed and exertion occurs.
What is it?
There are number of theories to explain the underlying causes of lung capillary hemorrhaging. Recent research has shown that the pulmonary artery blood pressure increases dramatically during excessive exercise, this blood pressure can reach maximum pressures that are 3 times greater than a competing human athlete. In the horse, high blood flow rates are essential to deliver oxygen to rapidly contracting muscles. The pressure generated by this blood flow in the small, thin-walled pulmonary arteries result in a rupture and/or hemorrhage. Once a few vessels burst, the coating of blood in the air sacs reduces surface tension, and the more likely it is that high-pressure capillaries will rupture.
Although it is a theory that links high blood pressure with pulmonary artery rupture, medications to reduce blood pressures and/or strengthening the lung capillary wall structure help to decrease the occurrence or likelihood of a rupture.
Since 98% are hidden bleeders, we need to look for the signs or symptoms. One sign is a horse that has once been very competitive begins to exhibit a decrease in his/her performance. The bleeding impairs the horse’s ability to obtain oxygen and gives the animal a feeling of choking. Once a horse has bled they will tend to “play it safe” in the competitions due to the fear of choking. They will not run as hard or perform to 100% of their ability. Choking or deep, heavy coughing after a performance or on the final stretch of a race are signs of a horse that is short of breath due to the blood is draining into their lungs. In addition, a horse may exhibit signs of restlessness, unwillingness to eat and repeated swallowing if they are a bleeder. Remember, only 2% will bleed through their nose and therefore is the most obvious, but uncommon sign.
To confirm if your horse is a bleeder, your veterinarian can “scope” your horse, which is a simple procedure of passing an endoscope into the windpipe within 2 hours of heavy competition. The endoscope will be used to see if there is blood present in the upper airways, as well as in the throat. A lung wash is also another diagnostic tool, which involves flushing the air sacs with a saline solution and sampling the fluid to measure the possibility of a reduced red blood cell count.
Some points to consider when managing a horse that has the tendency to bleed:
• Consult your veterinarian for treatment of any other respiratory infections or throat conditions.
• Reduce air borne dust by watering stall shavings and dampening dusty feed and/or hay.
• Prevent training in dusty arenas or tracks.
• Warm up at least 10 minutes prior to competition and preferably in warmer air temperatures.
• Medications referred by your veterinarian that reduce blood.
• Nutritionally, Vitamin C and E, as well as specific amino acids can aid in the health and strength of capillaries.
• Calm warm-ups will help to reduce your horses blood pressure prior to competition in turn reducing the unnecessary capillary strain, consider using calming nutritional products as well.
It is virtually impossible to prevent EIPH completely in high performance horses, but it can be controlled through management, medications and supplementation.
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