Introduction to hydration/dehydration

Dehydration occurs when you use or lose more fluid than you take in, and your body doesn’t have enough water and other fluids to carry out its normal functions. Anyone may become dehydrated, but the condition is especially dangerous for young children and older adults.


What is the normal level of hydration?

Water is the most abundant body constituent. It accounts for 75 – 80% of the birth weight in neonates (babies less than 30 days) and even higher in preterm babies, however this percentage decreases as the child grows such that by age one, water accounts for 60% of the total body weight – and this remains till adulthood. However, Total Body Water (TBW) decreases with increase in body fat, consequently obese children have reduced body water than slim children.

The simplest calculation for body water is to multiply 0.6 by the body weight (in kilograms) since water accounts for about 2/3rd of the body weight.

There are several methods for calculating the amount of water in the body ,the Watson and the Hume formular can be used, other   methods  specifically designed for children like the Mellits – Cheek formula is also very useful.

Hydration status can also be checked by comparing urine colour against a chart; normal urine is amber yellow in colour. Once a child’s hydration state reduces, urine becomes concentrated and the colour deepens to dark yellow or brown.

Specific gravity of urine can also be measured, sweat analysis gives an indication of the hydration status of a child as sweat is reduced when there is dehydration.


What level of dehydration can warrant ORT (oral rehydration therapy)?

Dehydration can be classified into three;

  • Mild dehydration
  • Moderate dehydration
  • Severe dehydration

These levels have their distinct features with the severe form being potentially  fatal.

Mild dehydration can be managed at home, usually resolving with administration of Oral Rehydration Solution and treatment of the cause.

However, moderate and severe forms of dehydration require hospital admission and monitoring as in these cases, dehydration might kill the child if care is not taken.

The following are tell tale signs of the degrees of dehydration;

Consciousness Alert Irritable Comatose
Eyes No changeSunken Very sunken
Tear No changeReduced Absent
Skin Normal Cold & paleCold & muffled
Pulse Normal/highWeak&fastVery weak & fast
Urine Reduced Very little None
Breathing Normal Fast Very fast
Fontanelle No changeSunken Very sunken

NOTE: The fontanelle is the space between the bones of your baby’s skull. They are usually two soft and depressible spots. The fontanelle at the back of the baby’s head (posterior fontanelle) closes often by 6 weeks while the fontanelle at the front of your baby’s head (anterior fontanelle) closes by 18 months.



What could cause a child to be dehydrated

  1. Diarrhoeal diseases are the commonest causes of dehydration in children especially in African countries.
  2. Vomiting
  3. Not drinking enough fluids
  4. Too much sweating due to hot weather
  5. Excessive urination probably due to undiagnosed or poorly treated diabetes mellitus or diabetes insipidus
  6. Fever from bacteria, viral or parasitic infections
  7. Burns
  8. Conditions like cystic fibrosis
  9. Cancers and their treatment.


Author: Editor

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