Dehydration:

• According to WHO, dehydration denotes loss of water and dissolved salts from body.
• It may be due to water and electrolyte deprivation or loss of body fluids.

Etiology:

There are 2 major causes of dehydration; inadequate water intake and excessive water loss

Inadequate water intake:

This may be due to:

• Deprivation of water
• Lack of thirst due to toxaemia
• Inability to drink water as in case of esophageal obstruction
• Depressed and comatose condition
• Paralysis of muscle of deglutition

Excessive loss of water:

It may occur due to:

• Diarrhoea
• Acute gastroenteritis
• Malabsorption
• Vomiting
• Loss of water through skin injury
• Lactic acidosis in ruminant
• Abomasal displacement
• Impactive colic in horse
• Salt wasting nephritis
• Pyometra
• Ascites
• Diffuse peritonitis
• Purgative, diuretic and corticosteroid therapy

Pathogenesis:

Types of dehydration:

Clinically dehydration is classified into 3 types:

1. Isotonic dehydration
2. Hypotonic dehydration
3. Hypertonic dehydration

1. Isotonic dehydration:

• In this type of dehydration there is iso-osmolarity loss of water and salt.
• It reduces extracellular fluid volume
• It occurs mainly due to acute gastroenteritis, fluid and food deprivation, repeated paracentesis in ascites and profuse sweating.
• It is manifested as mild dehydration with hyponatremia.

2. Hypotonic dehydration:

• There is loss of salt in excess of water.
• It is manifested as severe dehydration with severe hyponatremia
• It results from GI disorders, acute dilatation of stomach, pyloric stenosis, intestinal obstruction.

3. Hypertonic dehydration:

• There is deprivation of water without sodium loss.
• It is induced by insufficient water intake in case of GI disorders and diabetes insipidus.

Clinical Signs:

• Most and important findings in dehydration is drying and wrinkling of skin, giving body and face a shrunken appearance.
• Eyes recedes into socket and skin subsides slowly after being picked up into fold
• In calves, severe dehydration is associated with mental depression
• Rapid loss of body weight and muscular weakness.
• Inappetance or anorexia

Clinical Pathology:

• Increase in packed cell volume
• Increased total serum protein concentration
• Hyponatremia, hypokalemia, hypchloremia depending on cause.

Assessment of degree of dehydration in animals:

Degree of dehydration is assessed through recession of eyeball into orbit, time taken by folded skin to subside. For skin tenting test, skin of neck and lateral thorax are pinched between fingers, rotating the skin fold 90° and time required to disappear skin fold is noted. Normally time should be <2s.

Treatment:

• Fluid therapy is appropriate measures to correct dehydration.
• In case of isotonic dehydration, NS or Ringer’s lactate should be administered to improve renal function.
• 5% glucose is preferred to make up deficit from gastro-intestinal loss @30ml/kg, b.wt.
• In case of hypotonic dehydration, salt should be added to diet of animals. 0.9% NaCl should be administered for rapid restoration of plasma volume and renal circulation.
• In case of hypertonic dehydration, water and fluid should be administered orally. D5 administered IV followed by saline or Ringer’s solution in vomiting and comatosed animals.
• Water deficiency may be corrected by administering glucose 5% parenterally supplemented with electrolyte and Vitamin-B complex.
• ORS solution should be administered orally to correct electrolyte imbalances due to dehydration resulting from diarrhoea and vomiting.