>Subj: [endurance] Metabolic alkalosis
>Date: 95-12-01 13:00:17 EST
>From: dowling@sask.usask.ca (Patricia Dowling DVM)
>Sender: owner-endurance@moscow.com
>To: endurance@moscow.com (endurance riding)
>
>Lynn: an excellent explanation of
>metabolic/alkalosis/acidosis. But I'll argue a few points.
>
>Our endurance horses, due to many factors including their
>rapid
>respiration rates are alkalotic.
>
>The mechanism of metabolic alkalosis in heavily sweating
>endurance horses and horses given the diuretic furosemide
>(Lasix) is believed to be due to reduction in the
>extracellular fluid volume (normally 60% of body weight)
>from loss of water, sodium and chloride (in sweat), without
>a matching loss in bicarbonate. The compensatory response to
>metabolic acidosis is a decrease in respiration. I agree
>with the other responders: the horses are panting
>(tachypnea) in an effort to dissipate heat from the
>respiratory tract. Cows don't sweat well - they do this all
>the time!
>
>
> If respiration rate increases further,
>such as in an inversion the alkalosis worsens and the
>foundation is laid
>for development of thumps (synchronous diaphragmatic
>flutter) and
>rhabdomyolysis (tying up).
>
>Thumps (synchronous diaphragmatic flutter) results from a
>combination of metabolic alkalosis, low blood calcium,
>potassium, and magnesium. Metabolic alkalosis alters the
>ratio of free to protein-bound calcium. Protein bound calcim
> is not avaible for cellular function. These derangements
>disrupt the normal functioning of the phrenic nerve that
>controls the diaphragm - making it fire with every heart
>beat.
>
>
>
>THe horse is blowing of CO2 to bring up blood pH--but
>you imply that endurance horses are alkalotic--how can this
>be when the
>major muscle product is LACTIC ACID, which is causing the
>problem? If the
>blood pH is low because of HLa, it only makes sense to me
>that the horse
>would blow of CO2 to raise his pH to counteract HLa.
>Am I missing something?
>
>Gwen: your thinking is logical, and actually, we accepted
>for years that tied up horses have lactic acidosis and
>therefore must be metabolically acidotic. This was said in a
>vet journal decades ago, and no one challenged it. Finally
>someone did a study (Journal of the American Vet Med Assoc,
>1983) and found that tied-up horses are metabolically
>alkalotic. Many studies since have documented this in
>exhausted endurance horses. As far as blood lactic acid
>goes, studies show horses with chronic exertional
>rhabdomyolysis have LOWER blood lactic acid concentrations
>in affected muscles than normal horses. The most recent
>studies suggest that muscle damage occurs due to problems in
>reglating calcium inside the muscle cell.
>
>
>
>Sometimes when a heart rate goes erratic it is a deficiency
>of calcium, but
>I'm so expert. We are all still learning, and frankly, I
>think we know more
>than most fo the vets!!
>
>This comment is not appropriate for this list. We can have
>discussions and exchange information without insulting
>anyone. No one knows everything, and veterinarians are
>highly educated, but are expected to know many things about
>many species. If you want veterinarians who are more
>educated about distance horses, support your nearest
>veterinary school's chapter of the American Association of
>Equine Practitioners.
>
>Trisha Dowling, DVM, MS, Diplomate ACVIM, ACVCP
>Associate Professor, Veterinary Clinical Pharmacology
>Western College of Veterinary Medicine
>
>
>
>
>
>
>
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>From owner-endurance@moscow.com Fri Dec 1 12:58:42 1995
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>Date: Fri, 01 Dec 1995 10:12:42 -0800 (PST)
>From: Patricia Dowling DVM <dowling@sask.usask.ca>
>Subject: [endurance] Metabolic alkalosis
>To: endurance riding <endurance@moscow.com>
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Sorry, no offense intended, but as an endurance rider who has seen 20 plus
years of rides under 100's of vets, I have come to the conclusion that it is
the RIDER who knows how his horse is doing. Veterinary advice and control is
certainly necessary. I believe it should always be a PARTNERSHIP when ti
comes to evaluating the stress our horses undergo on enduracne rides!!!
Teddy