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Frequently Asked Questions

What is dehydration?

During diarrhoea there is an increased loss of water and electrolytes (sodium, chloride, potassium, and bicarbonate) in the liquid stool. Water and electrolytes are also lost through vomit, sweat, urine and breathing. Dehydration occurs when these losses are not replaced adequately and a deficit of water and electrolytes develops.

The volume of fluid lost through the stools in 24 hours can vary from 5 ml/kg (near normal) to 200 ml/kg, or more. The concentrations and amounts of electrolytes lost also vary. The total body sodium deficit in young children with severe dehydration due to diarrhoea is usually about 70110 millimoles per litre of water deficit. Potassium and chloride losses are in a similar range. Deficits of this magnitude can occur with acute diarrhoea of any etiology. The most common causes of dehydration are rotavirus, enterotoxigenic Escherichia coli (ETEC) and, during epidemics, Vibrio cholerae O1 or O139.

The degree of dehydration is graded according to signs and symptoms that reflect the amount of fluid lost:

  • In the early stages of dehydration, there are no signs or symptoms.
  • As dehydration increases, signs and symptoms develop. These include: thirst, restless or irritable behaviour, decreased skin turgor, dry mucous membranes, sunken eyes, sunken fontanelle (in infants), and absence of tears when crying vigorously.
  • In severe dehydration, these effects become more pronounced and the patient may develop evidence of hypovolaemic shock, including: diminished consciousness, lack of urine output, cool moist extremities, a rapid and feeble pulse (the radial pulse may be undetectable), low or undetectable blood pressure, and peripheral cyanosis.

Death follows soon if rehydration is not started quickly. Dehydration is the loss of water and body salts through diarrhoea. The human body needs water to maintain enough blood and other fluids to function properly. If your body loses substantially more fluids than you are drinking, you become dehydrated. You may lose fluids in a variety of ways:

  • when urinating
  • when you vomit or have diarrhoea
  • when sweating
  • from the lungs during normal breathing.

Along with the fluids, your body also loses electrolytes, which are salts normally found in blood, other fluids, and cells.

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updated: 23 August, 2019