Basic Concepts of Fluid and Electrolyte Therapy

6. Methods of Fluid Administration
Oral or enteral
The use of oral rehydration solutions to treat diarrhoeal disease in
both children and adults is one of the most commonly used treatments
worldwide, particularly in developing countries. They can also
be useful in the management of short bowel or inflammatory bowel
disease in hospital or at home.
These preparations are based on the principle that salt absorption in
the small bowel is linked to that of carbohydrate and is, therefore,
enhanced by glucose, glucose polymers and starch (e.g. rice water).
Some preparations also contain K + and an alkalising agent to counter
acidosis. In developing countries, they can be made using locally
available materials, with simple measuring devices to ensure the correct
proportions of salt, sugar or rice starch, and boiled water. In the
UK commercial preparations are available (see British National Formulary),
5 sachets of Dioralyte, for example, reconstituted in 1 litre of
water, give Na + 50 mmol, K + 20 mmol, Cl – 50 mmol, citrate 10 mmol,
and glucose 99 mmol. The WHO formula contains 75 mmol Na + . These
are suitable for diarrhoeal diseases in children and most adults,
although, in short bowel syndrome or inflammatory bowel disease in
adults, a more concentrated solution may be required and can be
obtained mixing more sachets per litre.
These solutions may also be administered via enteral tubes where oral
administration is difficult. Monitoring of oral or enteral fluid treatment
follows the same general principles as outlined in Chapter 3.
One of the advantages of oral and enteral administration is that it is
difficult to give excess fluid owing to limited tolerance. With intravenous
fluids it is only too easy to give excess salt and water with
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