Oral Rehydration Therapy

Over the past four decades, oral rehydration has been demonstrated to be quite effective in replacing diarrheal fluid losses. This therapy is best reserved for the child with mild or moderate dehydration.

The intestine (both the small bowel and colon) is remarkably efficient in its ability to absorb water. The small bowel absorbs the vast majority of the body's fluid needs.

Oral Rehydration Therapy (ORT) is accepted as the standard of care and first line treatment for the management of acute gastroenteritis with or without mild to moderate dehydration.

The following properties for ORT are recommended by the World Health Organization (WHO)

Total osmolality between 200 and 310 mOsm/L
Equimolar concentrations of glucose and sodium
Glucose concentration <20 g/L (111 mmol/L)
Sodium concentration between 60 and 90 mEq/L
Potassium concentration between 15 and 25 mEq/L
Citrate concentration between 8 and 12 mmol/L
Chloride concentration between 50 and 80 mEq/L

There are commercially available preparations that approximate these concentrations such as Pedialyte®, Enfalyte®, and Rehydralyte®.

Note: Patients with mild to moderate dehydration can be treated with ORT. Those with severe dehydration are not candidates and need IV infusions. Also, those patients with altered mental status who may be at risk for aspiration and those patients with intestinal diseases such as short gut or ileus are also not candidates. Vomiting is not a contraindication for ORT.

Phases of Oral Rehydration Therapy

ORT encompasses two phases of treatment

Rehydration phase. Water and electrolytes are administered as oral rehydration solution (ORS) to replace existing losses (the deficit is replaced quickly over 3-4 hours)
Maintenance phase: This includes both replacement of ongoing fluid and electrolyte losses and adequate dietary intake.

During both phases, fluid losses from vomiting and diarrhea are replaced in an ongoing manner. An age-appropriate, unrestricted diet should also be instituted after the dehydration is corrected. If the patient is breastfed, breastfeeding should continue during this phase as well as during the maintenance phase. Formula-fed infants should continue their usual formula immediately upon rehydration. Lactose-free or lactose-reduced formulas usually are unnecessary. The BRAT (banana-rice-applesauce-toast) diet is unnecessarily restrictive and can provide suboptimal nutrition.

How to Administer Oral Rehydration Therapy

ORS is administered in frequent, small amounts of fluid by spoon or syringe. A nasogastric tube can be used in the child who refuses to drink. Nasogastric (NG) feeding allows continuous administration of ORS at a slow, steady rate for patients with persistent vomiting. For those with vomiting, the majority can be rehydrated successfully with oral fluids if limited volumes of ORS (5 mL) are administered every 5 minutes, with a gradual increase in the amount consumed.

Mild to Moderate Dehydration

Rehydration phase: the dose is 50-100 ml/kg over 3-4 hours.

During both phases, ongoing losses from diarrhea and vomiting are replaced with ORS. If the losses can be measured accurately, 1 mL of ORS should be administered for each gram of diarrheal stool. Alternatively, 10 mL/kg of body weight of ORS should be administered for each watery or loose stool, and 2 mL/kg of body weight for each episode of emesis.

Severe Dehydration

Severe dehydration is a medical emergency, and requires emergent IV therapy with rapid infusion of 20 mL/kg of isotonic saline. As the patient's condition improves, therapy can be later changed to ORT.

Fluid and Electrolyte Therapy