How should acute gastroenteritis be managed regarding hydration assessment, oral rehydration solution (ORS) dosing, intravenous (IV) fluid therapy, antiemetic use, antidiarrheal therapy, antibiotic indications, stool testing, probiotic use, dietary advice, warning signs, and criteria for hospital admission?

Management of Acute Gastroenteritis

Oral rehydration solution (ORS) is the first-line treatment for mild-to-moderate dehydration, while severe dehydration requires immediate intravenous resuscitation with 20 mL/kg boluses of isotonic crystalloid until hemodynamic stability is achieved. 1, 2

Assessment of Dehydration Severity

Classify dehydration by clinical examination into three categories that determine all subsequent management 2, 3:

• Mild dehydration (3–5% fluid deficit): increased thirst, slightly dry mucous membranes 2
• Moderate dehydration (6–9% fluid deficit): loss of skin turgor with skin tenting when pinched, dry mucous membranes 2, 3
• Severe dehydration (≥10% fluid deficit): severe lethargy or altered consciousness, prolonged skin tenting >2 seconds, cool poorly perfused extremities, delayed capillary refill, rapid deep breathing indicating acidosis 2, 3

The most reliable clinical predictors of significant dehydration are abnormal capillary refill time, prolonged skin retraction, and decreased peripheral perfusion—more reliable than sunken fontanelle or absent tears. 2, 4

Obtain body weight immediately to calculate fluid deficit accurately and establish a baseline for monitoring. 2, 3

Oral Rehydration Therapy

Dosing by Dehydration Severity

• Mild dehydration: Administer 50 mL/kg of reduced-osmolarity ORS (containing 50–90 mEq/L sodium) over 2–4 hours 1, 2
• Moderate dehydration: Administer 100 mL/kg of ORS over 2–4 hours 1, 2, 5

Administration Technique

Initiate ORS with very small volumes (approximately 5 mL or 1 teaspoon) every 1–2 minutes using a spoon, syringe, or dropper, then gradually increase as vomiting diminishes. 2, 5 A common error is allowing a thirsty child to drink large volumes ad libitum, which worsens vomiting. 5

If oral intake fails despite small-volume technique, consider nasogastric administration of ORS in patients with normal mental status who are too weak or refuse to drink. 1, 2

Replacement of Ongoing Losses

After initial rehydration, replace ongoing losses with 1, 2, 5:

• 10 mL/kg of ORS for each watery or loose stool
• 2 mL/kg of ORS for each vomiting episode
• Continue maintenance fluids until diarrhea and vomiting resolve

Reassess hydration status after 2–4 hours; if rehydrated, transition to maintenance therapy, otherwise recalculate deficit and restart ORS. 2, 3

Intravenous Fluid Therapy

Indications for IV Rehydration

Severe dehydration (≥10% deficit), shock, altered mental status, or failure of oral rehydration constitutes a medical emergency requiring immediate IV therapy. 1, 2

IV Resuscitation Protocol

Administer 20 mL/kg boluses of lactated Ringer's or normal saline rapidly until pulse, perfusion, and mental status normalize. 1, 2, 3 Multiple boluses may be required; two IV lines or alternative access (intraosseous, femoral vein, venous cut-down) may be necessary for rapid resuscitation. 2

Once consciousness returns and the patient can tolerate oral intake without ileus, switch to ORS to replace the remaining deficit. 1, 2 In patients with ketonemia, an initial course of IV hydration may be needed to enable tolerance of oral rehydration. 1

Standard-volume IV rehydration (20 mL/kg/hour) is sufficient for most children; large-volume rapid rehydration (60 mL/kg/hour) has not demonstrated superiority and may be associated with longer time-to-discharge. 6

Antiemetic Use

Ondansetron may be administered to children >4 years of age and adolescents with significant vomiting to facilitate oral rehydration, but only after attempting small-volume ORS dosing. 1, 2, 5 Ondansetron increases ORT success rates, reduces need for IV therapy, and decreases hospitalization. 5, 4

Antiemetics do not replace fluid and electrolyte therapy and should only be used once adequate hydration is achieved. 1, 2

Metoclopramide has no role in gastroenteritis management and should not be used. 2

Antidiarrheal Therapy

Antimotility drugs (loperamide) are absolutely contraindicated in all children <18 years of age due to risk of respiratory depression, serious cardiac adverse reactions, ileus, and death. 1, 2, 5, 3

In adequately hydrated, immunocompetent adults with acute watery diarrhea, loperamide may be considered. 1 However, loperamide must be avoided at any age when diarrhea is inflammatory, bloody, or accompanied by fever due to risk of toxic megacolon. 1, 2, 5

Antibiotic Indications

Routine antibiotic therapy is not indicated for acute gastroenteritis, as the majority of cases are viral and self-limited. 1, 2, 5

Consider antibiotics only when 1, 2, 5:

• Dysentery (bloody diarrhea) with fever is present
• Watery diarrhea persists >5 days
• Stool cultures, microscopy, or epidemic setting identify a treatable pathogen
• Immunocompromised patients present with severe illness
• Clinical features of sepsis or suspected enteric fever

Azithromycin is the preferred empiric antibiotic for acute dysentery in both adults and children, given its activity against Shigella, Salmonella, and Campylobacter. 5

Critical contraindication: Never give antibiotics to patients infected with Shiga toxin-producing E. coli (STEC) O157, as therapy increases the risk of hemolytic-uremic syndrome. 5

When a clinically plausible organism is identified, modify or discontinue antimicrobial therapy to target the organism and reduce unnecessary antibiotic exposure. 1, 5

Stool Testing

Stool cultures are indicated for dysentery but are unnecessary for typical acute watery diarrhea in immunocompetent patients. 2, 5 Do not postpone rehydration while awaiting stool culture results; initiate ORS immediately based on clinical assessment. 2, 5

Blood cultures are indicated for patients who appear toxic or have signs of sepsis. 5

Probiotic Use

Probiotic preparations may be offered to immunocompetent adults and children to reduce symptom severity and duration in infectious or antimicrobial-associated diarrhea. 1, 2, 5 However, probiotic use remains uncommon in practice, with only 15% of pediatric emergency physicians routinely recommending them. 7

Dietary Management

Resume an age-appropriate usual diet during or immediately after rehydration is completed; feeding should not be delayed. 1, 2, 5

• Breastfeeding: Continue nursing on demand throughout the entire diarrheal episode without interruption 1, 2, 5, 3
• Bottle-fed infants: Resume full-strength formula immediately upon rehydration; lactose-free or lactose-reduced formula is preferred, but full-strength lactose-containing formula may be used under supervision 2, 5, 3
• Older children: Continue usual diet including starches, cereals, yogurt, fruits, and vegetables; avoid foods high in simple sugars and fats 1, 2, 5

Reduce or eliminate lactose only if true intolerance is evident (worsening diarrhea after lactose exposure), not based solely on low stool pH or reducing substances. 3

Adjunctive Therapies

Zinc supplementation (10–20 mg daily) reduces diarrhea duration in children 6 months to 5 years of age who reside in countries with high zinc deficiency prevalence or show signs of malnutrition. 1, 2, 5

Warning Signs Requiring Immediate Medical Attention

Instruct caregivers to return immediately if 2, 5, 3:

• Severe lethargy or altered consciousness
• Bloody diarrhea (dysentery)
• Intractable vomiting preventing oral rehydration
• High stool output (>10 mL/kg/hour)
• Decreased urine output (fewer than 3 wet diapers in 24 hours)
• Signs of worsening dehydration: sunken eyes, increased thirst, cool extremities
• High fever
• Signs of glucose malabsorption (increased stool output with ORS administration)

Criteria for Hospital Admission

Hospitalize patients with 2, 3:

• Severe dehydration (≥10% deficit) or signs of shock
• Failure of oral rehydration therapy after adequate trial
• Altered mental status
• Intractable vomiting despite antiemetic therapy
• Ileus
• Social concerns preventing safe outpatient management

Critical Pitfalls to Avoid

• Do not use sports drinks, fruit juices, or soft drinks for rehydration—they lack adequate sodium and contain excessive sugar that worsens diarrhea via osmotic effects 2, 5
• Do not delay feeding or impose restrictive diets—early refeeding reduces illness severity and duration 2, 5
• Do not give antimotility agents to children or to patients with bloody diarrhea or fever 1, 2, 5
• Do not withhold ORS while awaiting diagnostic testing—rehydration should begin immediately based on clinical assessment 2, 5
• Do not prescribe antibiotics empirically for non-bloody diarrhea in immunocompetent patients without travel history, as most cases are viral 5
• Do not treat asymptomatic contacts of people with acute diarrhea; instead, advise appropriate infection prevention and hand hygiene 1, 5