Hypocalcemia in Horses (Equis) | Vetlexicon
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Hypocalcemia

ISSN 2398-2977


Synonym(s): Synchronous diaphragmatic flutter, transit tetany, lactation tetany, eclampsia

Introduction

  • Cause: derangements in fluid and electrolyte balance including endurance exercise, hypocalcemia, hypoparathyroidism, digestive disturbances, lactation and administration of certain medications.
  • Signs: the diaphragm contracts in synchrony with atrial depolarization.
  • Diagnosis: serum total and ionized calcium concentrations.
  • Treatment: calcium supplementation, supportive care.
  • Prognosis: good with treatment; poor if seizures are present.

Presenting signs

  • A contraction or twitch in the flank area as the diaphragm contracts in synchrony with the heart.
  • If severe, this twitch can produce a thumping sound.
  • Dehydration.
  • Endurance horses associated with exhausted horse syndrome which includes inappropriate sweating, elevated body temperature, depression, anorexia.

Geographic incidence

  • Worldwide.

Breed/Species predisposition

  • Endurance horses.

Special risks

  • Calcium levels should always be evaluated in compromised patients prior to anesthesia.

Pathogenesis

Predisposing factors

General
  • Many various stimuli can result in hypocalcemia and therefore produce synchronous diaphragmatic flutter:
    • Prolonged exercise, especially in hot weather.
    • Lactation from 2 weeks prior to foaling up to a few days post-weaning.
    • Stress.
    • Transportation.
    • Cantharidin toxicosis.
    • Digestive tract dysfunction.
    • Furosemide therapy   Furosemide  .
    • Trauma.
    • Primary hypoparathyroidism   Endocrine: hypoparathyroidism  .
    • Acute or chronic renal failure   Kidney: renal failure  .
    • Endotoxemia   Endotoxemia: overview  .
    • Sepsis.
    • Dehydration.

Pathophysiology

  • Fluid, electrolyte, and acid-base derangements, especially hypocalcemia, decrease the threshold potential of the phrenic nerve, which innervates the diaphragm.
  • The phrenic nerve passes directly over the right atrium.
  • When the right atrium depolarizes, the phrenic nerve is stimulated resulting in a contraction of the diaphragm with each beat of the heart.
  • Clinically a rhythmic movement of the flank is seen as a result of diaphragmatic contractions that are synchronous with each heartbeat.

Diagnosis

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Treatment

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Prevention

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Outcomes

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Tejero E A, Estepa J C, Lopez I et al (2001) Plasma ionized calcium and parathyroid hormone concentrations in horses after endurance rides. JAVMA 219 (4), 488-490 PubMed.

Other sources of information

  • Valberg S & Carlson G (2009) Muscle Cramping. In: Large Animal Internal Medicine. Ed: Smith B. Elsevier, USA. pp 1398-1399.
  • Whiting J (2009) The Exhausted Horse. In: Therapy in Equine Medicine. Eds: Robinson N & Sprayberry K A. 6th edn. Elsevier, USA. pp 926-929.
  • Toribio R (2004) Disorders of the Endocrine System. In: Equine Internal Medicine. Eds: Reed S & Sellon D C. 2nd edn. Elsevier, USA. pp 1295-1327.