Rehydration
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Rehydration is the replenishment of water and electrolytes lost through dehydration. It can be performed by mouth (oral rehydration) or by adding fluid and electrolytes directly into the blood stream (intravenous rehydration).
As oral rehydration is less painful, less invasive, less expensive, and easier to provide, it is the treatment of choice for mild dehydration from infectious gastroenteritis. Because severe dehydration can rapidly cause permanent injury or even death, intravenous rehydration is the initial treatment of choice for that condition.
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Symptoms of dehydration
Symptoms of mild dehydration include thirst, decreased urine volume, urine that is darker than usual, tiredness, lack of tears when crying, headache, dry mouth, and dizziness when standing due to orthostatic hypotension.
In moderate to severe dehydration, there may be no urine output at all. Other symptoms in these states include lethargy or extreme sleepiness, seizures, sunken fontanel (soft spot) in infants, fainting, and sunken eyes.
Treatment
If someone is sufficiently dehydrated that he or she exhibits the signs of moderate to severe dehydration listed above, medical attention should be sought.
Oral rehydration can be accomplished by drinking frequent small amounts of an oral rehydration salt solution. One standard remedy is the WHO/UNICEF glucose-based Oral Rehydration Salts (ORS) solution, which contains 75 mEq/l of sodium, 75 mmol/l of glucose, 65 mEq/l chloride, 20 mEq/l potassium, and 10 mEq/l citrate, with a total osmolarity of 245 mOsm/l.
It is important to rehydrate with solutions that contain electrolytes, especially sodium and potassium, so that electrolyte disturbances may be avoided. Sugar is important to improve absorption of electrolytes and water, but if too much is present in ORS solutions, diarrhea can be worsened. Oral rehydration does not stop diarrhea, but keeps the body hydrated and healthy until the diarrhea passes.
There are several commercially available products but an inexpensive home-made solution consists of 8 level teaspoons of sugar and 1 level teaspoon of table salt mixed in 1 liter of water. A half cup of orange juice or half of a mashed banana can be added to each liter both to add potassium and to improve taste. If commercial solutions are used, true rehydration solutions should be used and sports drinks should be avoided (especially in younger children) as these solutions contain too much sugar and not enough electrolytes.
The amount of rehydration that is needed depends on the size of the individual and the degree of dehydration. Rehydration is generally adequate when the person no longer feels thirsty and has a normal urine output. A rough guide to the amount of ORS solution needed in the first 4-6 hours of treatment for a mildly dehydrated person is:
- Up to 5 kg (11 lb): 200 – 400 ml
- 5-10 kg (11-22 lb): 400 – 600 ml
- 10-15 kg (22-33 lb): 600 – 800 ml
- 15-20 kg (33–44 lb): 800 – 1000 ml
- 20-30 kg (44-66 lb: 1000 – 1500 ml
- 30-40 kg (66-88 lb): 1500 – 2000 ml
- 40 plus kg (88 lb): 2000-4000 ml
Technique
Adults and children with dehydration who are not vomiting can be allowed to drink these solutions in addition to their normal diet. People who are vomiting should be fed small frequent amounts of ORS solution until dehydration is resolved. Once they are rehydrated, they may resume eating normal foods when nausea passes.
Vomiting itself does not mean that oral rehydration cannot be given. As long as more fluid enters than exits, rehydration will be accomplished. It is only when the volume of fluid and electrolyte loss in vomit and stool exceeds what is taken in that dehydration will continue. When vomiting occurs, rest the stomach for ten minutes and then offer small amounts of ORS solution. Start with a teaspoonful every five minutes in children and a tablespoonful every five minutes in older children and adults. If output exceeds intake or signs of moderate to severe dehydration occur, medical assistance should be sought.