Oral rehydration in adults

Adults with clinical features of mild to moderate dehydration (see Assessing clinical and laboratory features of dehydration in adults) can often be adequately rehydrated with oral rehydration. Water and salt continue to be absorbed by active sodium-glucose–coupled transport in the small intestine, even in patients with severe diarrhoea.

Oral rehydration using proprietary oral rehydration solutions, fruit juice, sports drinks, soup, salty crackers, and water is adequate to treat dehydration in most adults with acute gastroenteritisRiddle, 2016. For patients with risk factors for dehydration or electrolyte abnormality or patients with an intellectual disability, a proprietary oral rehydration solution is preferred—these patients should also be under close observation.

The exact quantity of oral rehydration required depends on the volume of losses, the degree of dehydration and presence of comorbidities.

Several proprietary oral rehydration solutions are available in Australia. These products contain a balanced quantity of sodium and glucose, and have the advantage of also containing other electrolytes such as potassium and chloride. They all have a similar composition, with a sodium concentration of 45 to 60 mmol/L, glucose concentration of 80 to 120 mmol/L and total osmolarity of about 240 mOsm/L.

If proprietary oral rehydration formulations are unavailable, a homemade rehydration solution may be used (see the International Federation of Red Cross and Red Crescent Societies website for instructions).

Oral rehydration solutions should be made up exactly according to instructions, because incorrect preparation can worsen dehydration. Solutions should be refrigerated and replaced every 24 hours. Small volumes taken frequently (eg 50 mL every 15 to 30 minutes) may improve tolerability, and chilling the solution can improve its palatability. Intermittent vomiting does not preclude use of oral rehydration.