And down the stretch they come! With the track announcer's call, each pair of eyes turns toward the head of the stretch. The crowd roars in anticipation as the big chestnut, the favorite, lies just behind the front runners. His jockey moves him to the outside and asks for that quick burst of speed. The horse responds and in a few strides has drawn even. Suddenly, inexplicably, his stride shortens and the rest of the field closes the gap until first one horse passes him, then another.

The fans leave, puzzled.

The chart for the race in the paper the next morning gives the explanation. Two words say all--Bled significantly.
This type of incident is not uncommon in the racing industry--Thoroughbred, Quarter Horse, or Standardbred. Exercise-induced pulmonary hemorrhage (EIPH) is a given part of the vocabulary around racetracks and is a common cause of poor performance in horses. It even is thought that EIPH is not limited merely to racing horses, and that bleeding to some degree occurs in other breeds and disciplines. However, it is believed that more than 75% of racing Thoroughbred horses have experienced EIPH. Some researchers believe that figure to be 100%. The range of bleeding runs from mild to severe.

Whatever the figure, EIPH presents a serious compromise to a horse's performance ability, enough to prompt studies for finding solutions and drugs for treating or at least minimizing the severity of the condition.

EIPH results when the small blood vessels (the capillaries) within the lungs' alveoli (air sacs) rupture. During racing, the blood pressure in the lungs of horses becomes extremely high (pulmonary hypertension), even to the levels that one might find in humans in intensive care sections of the hospital. When the force being exerted across the capillaries becomes greater than the capillaries can withstand, they rupture and blood empties into the lungs.
Almost 95% of the horses which go to the track are on a treatment regime to prevent them from bleeding. Current treatment for this condition involves furosemide (Lasix), a diuretic.

Furosemide works on the principle that it alleviates the edema (water in the lungs). As the vessels under high blood pressure grow bigger and bigger, they stretch open. The first thing that comes out of the gaps is the water part of the blood (pulmonary edema). When the gaps became large enough, then blood also can seep into the lungs. Treatment with a diuretic supposedly draws the water away from the lungs by increasing urinary output. Theoretically, if horses are given furosemide, the drug draws the water away from the lungs and keeps the blood pressure from getting too high, thus preventing the gaps in the vessels and the blood from getting into the lungs.
Whether furosemide really works to prevent bleeding, and how it works if it does, is under constant debate; however, almost every racing jurisdiction in North America allows the use of furosemide on horses which are certified bleeders, i.e. horses which have been scoped by veterinarians and found to have bled.

Also arguable is how much Lasix to administer. A paper presented at the 1998 AAEP Convention tried to shed more light on that subject. Thomas E. Goetz, DVM, and Murli Manohar, BVSc, PhD, of the University of Illinois, conducted a study on Furosemide Dosage: The Effect of Sequential Administration of Two Doses of Furosemide on Exercise-Induced Pulmonary Hypertension of Thoroughbred Horses.

The basic principle of the study was "if one is good, two are better." They wanted to know if the administration of two sequential intravenous (IV) doses of furosemide caused a reduction of exercise-induced pulmonary hypertension in Thoroughbred horses exercising at maximal heart rate compared with a typical single dose. The two doses were administered four hours and two hours before exercise, while the single dose of 250 mg was administered intravenously four hours before exercise.

It is believed that furosemide reduces the plasma volume greatest 15 to 30 minutes after an IV administration of the drug. After it has reached this point, the amount of fluid begins to increase again. By two hours, it has returned to 2% of the original volumn, and by four hours it has returned to 5% of the original volume. In theory, if giving furosemide does decrease the amount of pulmonary hypertension in horses at work by eliminating plasma volume, then a second dose of furosemide administered as the plasma volume begins to recover (two hours or four hours later) might be better in decreasing the amount of hypertension in the lungs' capillaries, causing the severity of the bleeding to be less.

The study was conducted on seven healthy, sound Thoroughbreds on four occasions. One occasion was the control study (received no doses of furosemide), one was the single dose study (received 250 mg of IV furosemide four hours before exercising), one was the low double dose study (received a second dose of 250 mg of IV furosemide two hours after the first and two hours before exercise), and one the high double dose study (received a 2mg/kg dose of furosemide four hours pre-exercise and a second dose of 250 mg two hours after the first and two hours before exercise).

The results of the test showed that when endoscoped, five out of seven horses in the control group experienced EIPH, four out of seven in the single dose group, seven out of seven in the low double dose group, and three out of seven in the high double dose group.

Data also revealed that there were no significant differences in the pulmonary capillary blood pressures, pulmonary arterial pressures, or pulmonary venous pressures of any of the groups compared to the control group.
The study results showed that the administration of a second dose of furosemide two hour or four hours after the first dose and as plasma volume begins to recover does not reduce the incidence of EIPH in horses during exercise.

Wound Management Panel

Peter Fretz, VMD, Mike Martin, DVM, Ted Stashak, DVM, Mike Major, DVM, and Bill Stone, DVM, made up the Wound Management Panel, which was moderated by James Blackford, DVM. The panel began by discussing antibiotics in wound management. According to panel members, antibiotics are not always necessary when treating wounds if you have good debridement of the wound. When antibiotics are used, they need to be chosen meticulously since not all antibiotics perform the same.

The panel discussed some ways to deal with wounds. According to the panel, it's a good idea to wet the hair around the area to be clipped to prevent loose, dry hair from flying around and landing in the open wound. By wetting the hair, the chatter of the clippers also is diminished, which will aid in keeping the horse calm. After clipping the hair from around the wound, the wound should be prepped.

There are a number of good products available to scrub the surface of the wound. By scrubbing the wound, you reduce contaminants that might have taken up residence in the wound area. The wound especially needs to be scrubbed if it is noticeably contaminated. Sterile saline is available, and many of the panel members recommend its use. Panel members also mentioned that if saline is not available, then distilled water with salt added can be used for cleaning the wound. For large wounds, water is a good way to remove surface contaminants. You will need to maintain a certain PSI (pounds per square inch) pressure of water to remove contaminants effectively from the wound.

The panel noted that some products used to lavage (rinse) the wound actually can delay the healing process. In some cases, the wound is best left alone. The reason cited is that there is an electromagnetic field around wounds that might be disturbed by washing it.

The panel also touched upon the use of skin grafts when treating wounds. According to the panel, grafts should be stable at 10 days. Problems with grafts arise when the bandages are taken off and the graft hasn't healed properly. In those cases, the grafted skin often will come off with the bandages.--By Timothy C. Brockhoff

About the Author

Tom Hall

Tom Hall is a former English professor with a BA from Georgetown College, a JD from the University of Kentucky School of Law, and an MA in English from Western Kentucky University. He is an assistant editor for Eclipse Press.

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