From: Fourways Equine Clinic
Your Trainer says “Your horse bleeds!”
An explanation – Exercised Induced Pulmonary Haemorrhage.
By Dr. Willem LF van Wyk BSc, BVSc
Exercise induced pulmonary haemorrhage (EIPH) is a common condition seen often in race
horses where the horse bleeds into the airways following/during work. Horses suffering
from this condition are simply referred to as "bleeders". Scientific investigations have found
that up to 95% of race horses suffer from this condition to a greater or lesser degree. It
can have a profound effect on their performance, especially sprinting race horses.
The exact mechanism by which EIPH occurs is not exactly clear, and in many cases multiple
Signs of EIPH
underlying conditions may play a role. Although the blood is usually seen at the nose and in
the trachea, it originates in the small blood vessels in the lungs. The physiology of the
horse is unique in many ways, and the respiratory system in particular has evolved to
include a number of unique features to increase athletic performance. Horses have
exceptionally high blood pressure in the small blood vessels of the lungs. They also have a
much thinner blood-gas barrier than most other animals between the air in the lungs and
the blood vessels. During peak exertion, the lungs are exposed to concussion by the
movement of the abdominal organs as the horse gallops, which may damage the small
blood vessels. The air pressure in the lungs also fluctuates greatly as the horse breathes in
and out, putting great physical strain on the blood-gas barrier. All these factors contribute
to make horses prone to developing small bleeds in the lungs. Inflammatory conditions in
the lungs such as pneumonia and Inflammatory Airway Disease (IAD) make the blood-gas
barrier more fragile and can exacerbate the condition. Any narrowing or obstruction in the
airways increases the changes in air pressure in the lungs and can also contribute to EIPH.
Bacteria can grow very easily in the blood and mucous present in the airways of bleeders.
Ask Your Veterinarian
A bacterial infection can worsen the condition because of the resulting inflammation, which
in turn delays the resolution of the condition and makes the horse more prone to bleeding
during subsequent training sessions.
The most obvious sign of EIPH is the presence of blood at the nostrils after strenuous
exercise, but less than 10% of horses are affected severely enough for this to happen. In
most cases a sub-optimal performance at high intensity work is the most commonly seen
symptom. Race horses tend to suddenly fade at the end of a race or fast sprint, and may
In order to definitively diagnose a bleeder, a veterinarian would typically do one of two
Flair Nasal Strips
tests, namely an endotracheal endoscopy, or a broncho-alveolar lavage.
and Michigan State University’sveterinary schools, researchers noted
An endoscope is inserted through the nose and passed into the trachea in order to visualize
any blood that may be collecting there. This method is the most commonly used, and can
reduction in EIPH. One group ofresearchers at Calder Race Course
give a very accurate indication of how severe the problem is. It has to be performed shortly
after hard work, especially in less severe cases. If a horse does not have any blood or
blood-tinged mucous in the trachea an hour after hard work, moderate to severe EIPH can
be excluded fairly confidently. Endoscopies are typically graded from 0 to 5 to indicate the
approximately 50% of total airwayresistance in exercising horses…
horses had decreased airwayresistance and less negative
2: More than flecks, but less than a continuous stream of
exercise when wearing the nasalstrip."
3: Small continuous stream of blood less than half of the trachea width
4: Bloodstream more than half the tracheal width
A broncho-alveolar lavage is performed by injecting a small volume of fluid into one of the
large airways in the lung, and collecting the fluid again. The fluid is then analyzed under
the microscope to determine what cells are present in the airways. This method can
diagnose “bleeders” days or even weeks after an episode, as the blood and blood
breakdown products can be detected for a long time after the bleeding actually took place.
This method is more invasive and expensive and does not provide such a clear indication of
Treatment is typically aimed at reducing blood pressure and inflammation in the lungs. The
diuretic furosemide (Salix / Lasix) can be used to decrease the blood pressure and oedema
in the lungs, and thereby decrease the incidence and severity of EIPH. Ammonium chloride
is used for the same reason, and because it is a salt that occurs naturally in the body, it
will not result in a positive drug test in performance horses. Cortisone formulations can be
used to decrease inflammation in the lungs and airways, but their use is prohibited by
racing and competition bodies. Nebulisation and homeopathic remedies have shown
anecdotal evidence of working, and are used by many owners and trainers.
Measures to decrease airway resistance can also be useful in the prevention and treatment.
These include nasal flair strips and surgically correcting conditions such as laryngeal
hemiplegia. Antibiotics are also often used to minimise the effects of bacterial infections in
the airways. Sulphonamide formulations such as trimethoprim/sulphonamide
(Amphoprim/Trivetrin/Norotrim) are most commonly used.
Of all the remedies mentioned here, only furosemide and nasal flair strips have been
empirically proven to work, although anecdotal evidence suggests that the other remedies
may also be useful. Considering how pervasive the condition is, it is prudent to ask your
veterinarian for advice if you suspect your horse may be suffering from EIPH.
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