Kentucky's ongoing attempt to end racing in state proceeds..

[Riot]

Originally Posted by Rupert Pupkin

I wasn't talking about microscopic bleeding. It may very well be true that 93% of racehorses have evidence of microscopic bleeding. Microscopic bleeding is not a big deal. We don't need lasix for microscopic bleeding. Microscopic bleeding isn't going to affect a horse's performance in the least bit.

Whoa, wrong, no, yes, it does. Microscopic bleeding is indeed the big deal. It causes small airway and alveoli scarring, impedes their breathing, sets them up for lung infections, pneumonia, fear of running. This is precisely why we use lasix in most horses! Not just to keep from looking at massive, uncontrolled bleeding which is only visible in the larger airways.

There are about 18 branching divisions looking down into the lungs, and the bronchoscope only goes down a few. If there is so much bleeding down in the lungs that it's bubbling up to be visible, that's not good!

Yes, it's true the horses are not approved for lasix use on the track until they have a visible episode of bleeding (bleeding so significant it's literally coming up out of their lungs into their bronchi), but we know that 93% have bleeding that isn't severe enough to see grossly on a scope. Yes, we want to protect their lungs, too! If your distal airways at the tiny microscopic aveolar sacs are filled with blood cells, you can't get oxygen exchange and you start to suffocate. A horse can and will pull up with this, and the horse can get scoped, and you might not see bleeding grossly in the larger airways. But if you do bronchoalveolar lavage (not done stallside at the track commonly to diagnose EIPH) yes, you find the cause.

This is why the AVMA and AAEP support lasix use in race horses.

Remember that 30 years ago, we didn't even have common stallside bronchoscopy right after races to diagnose bleeding. We only diagnosed it if blood came out the nostrils. Now, we know better, as more horses that don't bleed visibly out their nostrils still have blood in the larger airways. And we know that horses that still don't have blood in the larger airways still show evidence of EIPH by blood down in the smaller airways and alveoli (air sacs that exchange oxygen with the tiny blood capillaries). 93% of them do.

The end point is: we use lasix in the United States and South America, and it's a good thing for race horse lungs. We could eliminate our lasix use on race day, but it would still be used in the morning to prevent injury to horse lungs when they work at speed (just like other countries do now). Why? Because it protects horse lungs. Even if a race isn't on the line.

[RolloTomasi]

Originally Posted by Riot

Microscopic bleeding is indeed the big deal. It causes small airway and alveoli scarring, impedes their breathing, sets them up for lung infections, pneumonia, fear of running. This is precisely why we use lasix in most horses! Not just to keep from looking at massive, uncontrolled bleeding which is only visible in the larger airways.

Are you suggesting that furosemide stops microscopic bleeding?

[Riot]

Originally Posted by RolloTomasi

Are you suggesting that furosemide stops microscopic bleeding?

Yes. Research shows a decrease in red blood cells and hemosiderophages via transtracheal washes post lasix vs. without lasix.

Diagnosing EIPH gives vastly different incident percentages depending upon the method: visual assessment by laypeople vs visual assessment by vet vs. bronchoscopy vs. transtracheal wash (TTW) or bronchoalveolar levage (BAL).

The gold standard is something we don't do on the track, BAL or TTW.

We do use bronchoscopy, but it misses evidence of lower airway bleeding, only detecting visible blood that has been moved up into the upper airways.

[RolloTomasi]

Originally Posted by Riot

Yes. Research shows a decrease in red blood cells and hemosiderophages via transtracheal washes post lasix vs. without lasix.

Is decreasing the severity of bleeding the same as stopping bleeding?

[Riot]

Originally Posted by RolloTomasi

Is decreasing the severity of bleeding the same as stopping bleeding?

Not necessarily - sometimes lasix makes it less, sometimes it makes it stop completely, sometimes it doesn't do anything. Overall yes, lasix vastly reduces the incidence of detection of bleeding due to EIPH in horses, including stopping it in some horses.

Here's a cross section of lung (viewing it from the horses left side, the front of the horse is on the left) showing where bleeding occurs, the top (dorsal) back (caudal) part of the lung. We only detect blood when it comes out of the lungs up into the trachea. The trachea isn't shown here, it would be to the left of the lungs:





Here's a horse bleeding so bad blood is bubbling out of the lungs, up the trachea, and out the nose. Only 1 out of 20 will bleed so badly this is seen:



Here's a horse with a little blood in the trachea via bronchoscopy:

[RolloTomasi]

Originally Posted by Riot

Overall yes, lasix vastly reduces the incidence of detection of bleeding due to EIPH in horses, including stopping it in some horses.

So the majority of horses treated with lasix do not bleed?

[Riot]

Originally Posted by RolloTomasi

So the majority of horses treated with lasix do not bleed?

The majority have their previously documented level of bleeding markedly decreased or gone, as evidenced by bronchoscopy clinically and BAL/TTW in research. Lasix does not work in all horses, some are unaffected.

The origins and causes of EIPH are thought to be multifactorial. In the 1990's I worked on the research that first measured actual cardiopulmonary intravascular pressures in horses while galloping at racing speed both on and off lasix. Lasix decreases the exercise-induced increase in cardiac and pulmonary pressures. High blood pressure rupturing fragile capillaries in the lung has always been one suspected cause of EIPH.

Chronic airway inflammation predisposing to capillary failure is another. I'd love to study the lungs of horses that live year-round at Churchill Downs, bordered by highways and under airport plane exhaust.

Another is the physical pounding, and physics: the sheer forces created within the lung tissue as a horse gallops a long time over firm ground carrying weight.

Another is the huge variance in intrapulmonary airway pressures, upper vs lower, during massive air intake of exercise - why the Flair nasal strips which hold the upper airway open decrease EIPH as much as lasix in some horses.