Oral rehydration therapy

INTRODUCTION — Globally, diarrheal disease remains one of the leading causes of childhood mortality and morbidity. Loss of intestinal fluid caused by gastroenteritis may lead to severe hypovolemia, shock, and death, particularly in children younger than five years of age in areas of the world with limited resources. In resource-abundant settings, such as the United States, diarrhea caused by gastroenteritis remains a major cause of hospitalizations.

Although the total number of deaths globally from diarrheal diseases from gastroenteritis remains high, the overall mortality rate has steadily declined over the last few decades. This decline, especially in resource-limited countries, is largely due to the early and appropriate use of oral rehydration therapy (ORT), improved nutrition and water sanitation measures, and effective vaccination for rotavirus. (See "Approach to the child with acute diarrhea in resource-limited settings", section on 'Prevention'.)

The composition of oral rehydration solutions (ORS) and the clinical application of ORT in patients with diarrhea due to gastroenteritis are discussed in this topic review. Related content is available in these topic reviews:

●(See "Clinical assessment of hypovolemia (dehydration) in children".)

●(See "Treatment of hypovolemia (dehydration) in children in resource-abundant settings".)

●(See "Acute viral gastroenteritis in children in resource-abundant countries: Management and prevention".)

Material focused on children in resource-limited settings includes:

●(See "Approach to the child with acute diarrhea in resource-limited settings".)

●(See "Management of complicated severe acute malnutrition in children in resource-limited settings", section on 'Dehydration'.)

DEFINITIONS OF HYPOVOLEMIA AND DEHYDRATION — The terms volume depletion (hypovolemia) and dehydration often are used interchangeably. However, these terms differentiate physiologic conditions resulting from different types of fluid loss. Much of the clinical literature does not differentiate between the two terms and uses them interchangeably. Thus, we will follow this convention and use the terms hypovolemia, volume depletion, and dehydration interchangeably as referring to all types of fluid deficits. (See "General principles of disorders of water balance (hyponatremia and hypernatremia) and sodium balance (hypovolemia and edema)".)

PHYSIOLOGIC BASIS

Normal mechanisms for water absorption — The following three principal mechanisms are responsible for passive intestinal water absorption (see "Pathogenesis of acute diarrhea in children", section on 'Molecular mechanisms'):

●Sodium/hydrogen (Na/H) exchangers

●Electrochemical gradient

●Sodium-coupled transport with carrier organic solutes (eg, glucose)

Disruption of any of the above processes can result in diarrhea. However, in children with diarrhea due to gastroenteritis, the sodium-coupled co-transport with glucose and other carrier organic solutes remains intact [1,2].

Oral rehydration solution properties for water absorption — Successful oral rehydration solutions (ORS) take advantage of the preserved co-transport of glucose and sodium in patients with acute infectious diarrhea for water absorption. Studies from the 1960s reported that isotonic ORS formulations with equimolar concentrations of glucose and sodium are as effective as intravenous (IV) hydration in treating hypovolemia in patients with cholera [1,2]. Subsequent formulations have been designed based on this initial formulation (table 1).

Recommended composition — The following properties for ORS are recommended by the World Health Organization (WHO) [3]:

●Total osmolarity 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

Fluids with a molar ratio of glucose in excess of sodium (eg, fruit juices, soda, or sports beverages) have the theoretical potential of increasing diarrheal losses because the higher unabsorbed glucose load will increase the osmolarity in the lumen, resulting in decreased water absorption.

Fluids with excess sodium concentration compared with glucose (eg, chicken broth) may also increase diarrheal losses as there is no organic solute to facilitate the transport of sodium. On the other hand, fluids with excessively high sodium concentration may result in hypernatremia.

Osmolarity — Several clinical trials and meta-analyses have demonstrated that the administration of solutions with lower osmolarity can reduce stool volume and the duration of diarrhea [4,5]. These findings led the WHO to reduce the recommended ORS formulation in 2002 from an osmolarity of 311 mOsm/L to 245 mOsm/L, as well as the concentrations of glucose from 20 g/L (111 mmol/L) to 13.5 g/L (75 mmol/L) and sodium from 90 to 75 mEq/L. The new formulation preserved the molar 1:1 ratio of sodium and glucose and is the only ORS used globally by the WHO.

Although there were concerns initially that the reduced-osmolarity ORS may result in hyponatremia for patients with cholera who often have diarrheal losses of sodium concentration of 90 to 120 mEq/L, a large observational study in Bangladesh reported that the incidence of symptomatic hyponatremia was rare in both children and adults [6]. Thus, reduced-osmolarity ORS is safe and can be used to treat most patients with acute diarrhea.

Rehydration Solution for Malnutrition (ReSoMal), which has a lower sodium and higher potassium content than traditional WHO ORS, was developed specifically for use in severely malnourished children. Its composition and use are discussed separately. (See "Management of complicated severe acute malnutrition in children in resource-limited settings", section on 'Dehydration'.)

Carrier organic solute

●Glucose – The WHO ORS formulation uses glucose as the carrier organic solute for sodium-coupled transport (table 1). Although other alternative solutes have been studied (eg, zinc, prebiotics, glucose polymers, L-isoleucine) with some promising results, there are not conclusive data that they are more effective than glucose. Consequently, use of the WHO formulation containing 75 mEq/L of sodium and 75 mmol/L of glucose with an osmolarity of 245 mOsm/L water is still recommended.

●Polymer-based formulations – Polymer-based ORS uses rice, wheat, and sorghum as a source of starch rather than glucose. Starch is broken down slowly into glucose molecules by amylase in the small intestine. A systematic review showed that the polymer-based ORS is more effective than high-osmolarity, glucose-based ORS (≥310 mOsm/L) in reducing stool volume and duration of diarrhea for patients with acute watery diarrhea due to cholera or other causes [7]. However, data were insufficient to show that polymer-based ORS is superior to glucose-based ORS with lower osmolarity (≤270 mOsm/L water).

Until further data are available, we do not recommend initial use of polymer-based ORS either in resource-limited or resource-abundant settings, consistent with medical society guidance [8]. These formulations are not more effective than the standard WHO or commercial ORS, which are more readily available and less costly.

●Other carrier solutes – Formulations that use maltodextrins or rice, or add amino acids (glycine, alanine, and glutamine) to glucose, are also not more effective than standard ORS and are more costly [9-11]. These formulations should not be routinely used.

EFFICACY — ORT reduces childhood mortality from diarrheal disease [12-14]. This was best illustrated in a 2010 meta-analysis that included three low-quality studies showing diarrhea-specific mortality was lower in communities in which oral rehydration solution (ORS) was promoted compared with control communities without ORS promotion [14].

In addition, clinical trials and meta-analyses have shown that ORT is as effective as intravenous (IV) rehydration therapy in treating hypovolemia from diarrheal illness due to gastroenteritis [15-23]. ORT was also associated with a shorter length of hospitalization, lower costs, and fewer complications (eg, phlebitis).

CLINICAL MANAGEMENT — ORT is the preferred first-line treatment of fluid and electrolyte losses caused by diarrhea due to gastroenteritis in children with mild to moderate dehydration [15-23]. It is used to treat hypovolemia caused by gastroenteritis independent of age, causative agent, or initial sodium values [24]. Advantages of ORT compared with intravenous (IV) hydration include that it is lower cost, easier to administer, a less invasive intervention that can be performed at home, and associated with a lower rate of revisits to the emergency department (ED) [25]. (See 'Efficacy' above.)

Setting — ORT can be given either at home or in a medically supervised setting.

●Home – If parents or caregivers are properly instructed to recognize the appropriate clinical signs of dehydration, ORT can be given at home, leading to fewer outpatient and ED visits [26]. A standard commercially prepared and premixed oral rehydration solution (ORS) is recommended for use in nonmedical settings because major errors can occur when homemade solutions using sugar and sodium are administered (table 1) [27]. Parents and caregivers need to be educated on how to perform ORT and how to recognize signs of illness or treatment failure requiring medical attention [28]. Assessment of the patient at home with gastroenteritis is discussed elsewhere.

●Medically supervised setting – Prior to initiation of ORT, the child who presents to a medical clinician's office, ED, or urgent care facility with diarrhea should be evaluated to determine the underlying etiology of diarrhea and whether further diagnostic testing and/or intervention is necessary. (See "Diagnostic approach to diarrhea in children in resource-abundant settings".)

If there is evidence that rehydration is appropriate, ORT using a standard commercial formulation should be initiated if the patient has mild to moderate hypovolemia and there are no contraindications to enteral therapy.

Oral rehydration therapy based on degree of dehydration

Assessment of dehydration — Once the decision is made to begin hydration therapy, clinical assessment of the patient's hydration status is necessary as it guides clinical decisions in the use of ORT. The goal of hydration assessment for patients with diarrhea is to determine the fluid management approach for individuals, as follows:

●Identify patients who are not dehydrated and can be safely sent home with ORT maintenance

●Identify patients who are mildly to moderately dehydrated, in whom ORT is the preferred therapy for rehydration

●Identify patients who are severely dehydrated and require IV rehydration

Traditionally, attempts have been made to differentiate between mild and moderate hypovolemia (table 2). However, in the clinical setting, it is difficult to distinguish between the two degrees of dehydration because the signs or symptoms overlap and encompass a relatively wide range of fluid deficits (ie, from 3 to 9 percent volume depletion) [29]. As a result, experts, including the author, group patients with mild to moderate dehydration together as "some" dehydration and manage them similarly. (See "Clinical assessment of hypovolemia (dehydration) in children", section on 'Estimating degree of hypovolemia'.)

The following sections outline recommendations for ORT based on guidelines from the Centers of Disease Control and Prevention (CDC), American Academy of Pediatrics (AAP), European Society for Paediatric Gastroenterology, Hepatology and Nutrition, and European Society for Paediatric Infectious Diseases [8,28]. These guidelines are based on data acquired from efficacy trials conducted in both resource-limited and resource-abundant settings.

Treatment is divided into two phases:

●Rehydration phase – The fluid deficit is replaced quickly over three to four hours, returning the patient to a euvolemic state. ORS is administered in frequent, small amounts by spoon or syringe. A nasogastric tube can be used in the child who refuses to drink [28,30-32]. Each aliquot given must be small enough to avoid accumulation of a large amount of fluid in the stomach that might trigger vomiting. Five mL (one teaspoon), administered every one to two minute, allows as much as 150 to 300 mL/hour to be given. If the patient is breastfed, breastfeeding continues during this phase as well as during the maintenance phase.

●Maintenance phase – Maintenance calories and fluids are administered. Rapid realimentation begins after completion of the rehydration phase, with the goal to return the patient to an age-appropriate unrestricted diet. (See "Maintenance intravenous fluid therapy in children".)

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.

No dehydration — For patients with diarrhea but no evidence of dehydration, ORT is used to maintain hydration by replacement of stool losses, as outlined above. If the stool output is minimal, ORS may not be required. Regardless of stool output, age-appropriate feeding (including breastfeeding) should be continued along with supplemental fluids. (See 'Common household beverages and fluids' below.)

Mild to moderate (some) dehydration — While some individuals with lesser degrees of dehydration can be cared for at home once proper oral rehydration techniques have been taught, the care of patients with greater degrees of dehydration is best provided in a medically supervised setting.

●Repletion phase – Hydration should be restored by administering ORS at a volume of 50 to 100 mL/kg over four hours. Additional ORS is given to replace ongoing gastrointestinal losses (eg, stool or emesis). Reassessment of the patient's hydration status and replacement of ongoing losses should occur hourly.

●Maintenance phase – Once repletion is completed, feeding and fluids should be started as discussed previously. ORT is continued for ongoing gastrointestinal losses. The patient's hydration status and ongoing stool and emesis losses should be calculated, with the total hourly loss added to the amount to be given over the next hour.

Severe dehydration — Severe dehydration is defined as 10 percent or greater volume loss.

●Repletion phase – Severe dehydration is a medical emergency and requires emergent IV therapy with rapid infusion of 20 mL/kg of an isotonic solution (eg, 0.9% NaCl, Plasmalyte, or lactated Ringer). A more complete discussion regarding treatment of severe dehydration can be found in a separate topic review. (See "Treatment of hypovolemia (dehydration) in children in resource-abundant settings", section on 'Emergency fluid repletion phase'.)

As the patient's clinical condition stabilizes and their level of consciousness returns to normal, therapy can be changed to ORT. A nasogastric tube can be used in patients who have a normal mental status but may be too weak to adequately drink the necessary volume of fluid. The IV line should remain in place until it is certain that there is successful transition to ORT. ORS is started at a volume of 100 mL/kg over four hours or 25 mL/kg per hour. Additional ORS is given to replace ongoing gastrointestinal losses, as previously outlined. At the end of each hour, the patient's hydration status and continuing stool and emesis losses should be calculated, with the total hourly loss added to the amount to be given over the next hour.

●Maintenance phase – Once repletion is completed, feeding and fluids should be started, as discussed previously. ORT is continued for ongoing gastrointestinal losses [4-6,9-11,21,33-45].

Discharge from medical setting and return to home management — Patients can be discharged from a medical setting and returned to home ORT management when the following endpoints are achieved [28]:

●A reasonable amount of ORT for the degree of dehydration has been successfully administered. Sufficient intake is reflected by normalization of vital signs, improved level of consciousness and activity, urine output (if there has been none for a prolonged period of time), and resolution of signs of dehydration. In addition, there is no evidence of intractable vomiting or ORS refusal.

●No concern for other possible illnesses that might complicate the clinical course.

●No social or logistical concerns that might prevent return evaluation, if necessary.

●Caregivers have been sufficiently educated regarding the use of ORT at home and the criteria for return or need for further medical advice (eg, signs of dehydration).

Contraindications to oral rehydration therapy — There are clinical settings when ORT should not be used. These include in children with the following conditions:

●Altered mental status with concern for aspiration

●Abdominal ileus

●Underlying disorder that limits intestinal absorption of ORT (eg, short gut, carbohydrate malabsorption)

●Severe dehydration (see 'Severe dehydration' above)

Once ORT has been initiated, intervention with IV hydration is indicated:

●If stool output continues to be excessive and ORT is unable to adequately rehydrate the child

●If there is severe and persistent vomiting and inadequate intake of ORS

Commercial and standard oral rehydration solutions — Either the standard World Health Organization (WHO) or a commercially available ORS should be used for ORT. These solutions have equimolar concentration of glucose and sodium with osmolarity between 200 and 310 mOsm/L; the precise composition varies slightly, as summarized in the table (table 1). Based on the available data, differences in the composition of commercially available products and the 2002 WHO ORS do not appear to be clinically significant when administered to children with diarrhea in resource-abundant settings.

All commercial ORS contain 2 to 3 percent carbohydrate as glucose, rice, or other cereal; this amount is sufficient to promote intestinal water absorption while avoiding a large osmotic load in the intestinal lumen. Studies in the United States demonstrated successful treatment with commonly used commercial ORS in children with mild to moderate dehydration [21,36]. In children between 5 and 10 years of age, sucralose-sweetened ORS solutions (eg, Pedialyte and Pediatric Electrolyte) appear to be more palatable than comparable rice-based solutions (eg, Enfalyte) and are appropriate ORS options [46]. (See 'Oral rehydration solution properties for water absorption' above.)

Other therapeutic measures

Common household beverages and fluids — Commonly used household fluids for children with gastroenteritis include gelatin, tea, fruit juice, sports drinks, and soft drinks. These fluids have much lower sodium concentration, and nearly all have a much higher carbohydrate and osmolarity content than commercial and standard ORS (table 1). As a result, they have not been recommended as an alternative to commercial standard ORS for rehydration in children with gastroenteritis, because of concerns that they could induce osmotic diarrhea, resulting in hyponatremia. However, a Canadian clinical trial in children between 6 to 60 months of age with mild gastroenteritis and no clinical signs of dehydration demonstrated that half-strength apple juice (diluted 1:1 apple juice:water) compared with apple-flavored commercial standard ORS resulted in fewer episodes of treatment failure (17 versus 25 percent) [47]. In this single-center study, treatment failure was defined as any of the following events occurring within seven days of enrollment: IV rehydration, hospitalization, subsequent unscheduled clinician encounter, protracted symptoms, crossover to the other fluid, and 3 percent or more weight loss or signs of significant dehydration based on an in-person follow-up visit. Following ED discharge, the group assigned to half-strength apple juice were allowed to consume whatever fluids the children desired to replace ongoing losses and the ORS group continued with electrolyte maintenance solution. These results show that diluted apple juice followed by a permissive approach to fluids consumption can be used to maintain hydration in young children with mild gastroenteritis and minimal dehydration in high-income countries.

On the other hand, chicken soup, which has a high sodium concentration, may result in hypernatremia and should be avoided as a rehydration fluid source [28].

Zinc — Zinc supplementation should be administered to children older than six months of age with diarrhea in resource-limited countries where there is a high prevalence of zinc deficiency [48]. Zinc supplementation in these settings is discussed in greater detail elsewhere. (See "Approach to the child with acute diarrhea in resource-limited settings", section on 'Vitamins and minerals'.)

Antiemetic therapy — In patients with clinically significant vomiting, the use of the antiemetic ondansetron has facilitated the administration of ORT by reducing vomiting [49]. (See "Acute viral gastroenteritis in children in resource-abundant countries: Management and prevention", section on 'Antiemetic agents'.)

Barriers to the use of oral rehydration therapy in resource-abundant settings — Despite its universal success in low- and middle-income countries, ORT remains underutilized in many high-income countries, particularly in the United States. In a comparative analysis that included children with similarly severe episodes of acute gastroenteritis seeking ED care in the United States or Canada, revisit rates were similar despite lower rates of IV rehydration and hospitalization in Canadian EDs [50]. These findings demonstrate that there is likely room to further promote ORT in the United States.

Barriers to ORS utilization include:

●Lack of compliance and knowledge by clinicians – Surveys conducted over the past two decades showed that clinicians had insufficient knowledge regarding ORT and did not follow guidelines developed by the AAP or CDC on the appropriate use of ORT in patients with hypovolemia due to gastroenteritis [41-43]. In a 2011 survey, 44 of the 94 pediatric emergency clinicians from the United States (47 percent) reported using ORT as initial therapy in children with moderate dehydration compared with 103 of 136 Canadian clinicians (76 percent) [51]. This may reflect findings from an early report of American emergency clinicians who preferred IV hydration to ORT in treating moderate dehydration in children with gastroenteritis, even among those who indicated familiarity with the guidelines promoting ORT [40].

These results demonstrate the need for continued efforts to educate clinicians on the benefits of ORT over IV hydration.

●Expense – The cost of commercially available ORS may limit its use at home in low-socioeconomic families [44]. As noted above, diluted apple juice and other fluids routinely consumed by children are reasonable options for children with mild gastroenteritis and no clinical symptoms of dehydration. (See 'Common household beverages and fluids' above.)

●Public access to inaccurate information – There was one case report of a child whose care was compromised by following advice to use nonphysiologic fluids at a decreased rate from a hospital's internet site [45].

SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Fluid and electrolyte disorders in children".)

INFORMATION FOR PATIENTS — UpToDate offers two types of patient education materials, "The Basics" and "Beyond the Basics." The Basics patient education pieces are written in plain language, at the 5^th to 6^th grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are written at the 10^th to 12^th grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon.

Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on "patient info" and the keyword(s) of interest.)

●Basics topics (see "Patient education: Giving your child over-the-counter medicines (The Basics)" and "Patient education: Dehydration in children (The Basics)")

●Beyond the Basics topic (see "Patient education: Acute diarrhea in children (Beyond the Basics)")

SUMMARY AND RECOMMENDATIONS

●Benefits of oral rehydration therapy (ORT) – We recommend ORT as the initial treatment for most patients with mild to moderate (some) hypovolemia due to gastroenteritis (table 2) (Grade 1A). ORT is as effective as intravenous (IV) hydration to treat hypovolemia in patients with gastroenteritis but is less invasive and costly and easier to administer. (See 'Efficacy' above and 'Oral rehydration therapy based on degree of dehydration' above.)

●ORT formulations – We suggest that a standard, commercially prepared oral rehydration solution (ORS) or one available from the World Health Organization (WHO), which has equimolar concentrations of glucose and sodium and an osmolarity between 200 and 310 mOsm/L, be used for ORT in children with clinical signs of dehydration (table 1) (Grade 2B). However, for children with mild gastroenteritis and no clinical signs of dehydration, half-strength apple juice is a reasonable option for ORT. Homemade solutions that use sugar and sodium should not be used, because of the risk of major errors. (See 'Oral rehydration solution properties for water absorption' above and 'Setting' above and 'Common household beverages and fluids' above.)

●Contraindications to ORT – ORT is contraindicated in patients with impaired mental status at risk for aspiration, abdominal ileus or other conditions that preclude adequate fluid absorption from the intestinal tract, severe hypovolemia, or persistent vomiting. IV hydration should be administrated to patients with these conditions as well as to those with dehydration who fail ORT. In patients with severe dehydration, emergent IV therapy is required with rapid infusion of 20 mL/kg of isotonic saline or a balanced crystalloid solution. Once the patient is stable, ORT can be started. (See "Treatment of hypovolemia (dehydration) in children in resource-abundant settings".)

●Implementation – We recommend dividing ORT into rehydration and maintenance phases for patients with gastroenteritis and mild or moderate dehydration (Grade 1B). In both phases, ongoing losses from diarrhea and vomiting are replaced with ORS. (See 'Oral rehydration therapy based on degree of dehydration' above.)

•Rehydration – In patients with mild or moderate hypovolemia, ORS is administrated in frequent, small amounts, no more than 5 mL administered every one to two minutes by spoon or syringe, for a total volume of 50 to 100 mL/kg replaced quickly over three to four hours. If the patient is breastfed, breastfeeding is maintained during the rehydration phase and is continued into the maintenance phase.

•Maintenance – During the maintenance phase, maintenance calories and fluids are administered to replace ongoing losses. Rapid realimentation begins after completion of the rehydration phase, with the goal to return the patient to an age-appropriate, unrestricted diet.

ACKNOWLEDGMENT — The UpToDate editorial staff acknowledges Bonita Stanton, MD, Joshua B Evans, MD, and Bobby Batra, MD, who contributed to earlier versions of this topic review.