How should acute gastroenteritis be assessed and managed, including rehydration, antiemetic use, antibiotic indications, and criteria for hospital admission?

Acute Gastroenteritis Management

Assessment of Dehydration Severity

Classify dehydration by clinical signs to determine the entire treatment pathway: mild (3–5% fluid deficit), moderate (6–9% deficit), or severe (≥10% deficit). 1, 2

• Mild dehydration (3–5%): Increased thirst, slightly dry mucous membranes, normal mental status 1, 2
• Moderate dehydration (6–9%): Loss of skin turgor with tenting when pinched, dry mucous membranes, reduced urine output 1, 2
• Severe dehydration (≥10%): Severe lethargy or altered consciousness, prolonged skin tenting >2 seconds, cool and poorly perfused extremities, decreased capillary refill, rapid deep breathing (indicating acidosis) 1, 2

The most reliable clinical predictors are abnormal capillary refill time, prolonged skin retraction time, and rapid deep breathing—these correlate better with actual fluid deficit than sunken fontanelle or absent tears. 1, 3

Obtain an accurate body weight immediately; acute weight change is the most precise measure of fluid deficit when premorbid weight is known. 1, 2

Rehydration Protocol

Mild Dehydration (3–5% deficit)

Administer oral rehydration solution (ORS) containing 50–90 mEq/L sodium at 50 mL/kg over 2–4 hours. 1, 2

• Use a teaspoon, syringe, or medicine dropper to give small volumes (5–10 mL) every 1–2 minutes, gradually increasing as tolerated 1, 2
• Critical technique point: Never allow the patient to drink large volumes rapidly from a cup—this provokes vomiting and falsely suggests oral rehydration has failed 2
• Replace ongoing losses with 10 mL/kg ORS for each watery stool and 2 mL/kg for each vomiting episode 1, 2
• Reassess hydration status after 2–4 hours; if still dehydrated, reestimate deficit and restart rehydration 1, 2

Moderate Dehydration (6–9% deficit)

Administer 100 mL/kg ORS over 2–4 hours using the same small-volume technique. 1, 2

• If oral intake fails despite proper technique, consider nasogastric administration of ORS 2, 4
• Continue replacing ongoing losses as above 1, 2
• Success rates exceed 90% when the small-volume, slow-administration method is used correctly 2

Severe Dehydration (≥10% deficit)

This constitutes a medical emergency requiring immediate intravenous rehydration. 1, 2

• Administer 20 mL/kg boluses of Ringer's lactate or normal saline IV until pulse, perfusion, and mental status normalize 1, 2
• May require two IV lines or alternative access (intraosseous, femoral vein, venous cutdown) 1, 2
• Once mental status improves, transition to ORS to replace the remaining fluid deficit 1, 2
• Hospitalization is mandatory for severe dehydration. 2, 4

Nutritional Management

Resume age-appropriate normal diet immediately during or after rehydration—do not withhold food or enforce fasting. 1, 2

• Continue breastfeeding throughout the illness in infants 1, 2
• Offer starches, cereals, yogurt, fruits, and vegetables 2, 4
• Early refeeding reduces intestinal permeability, shortens illness duration, and improves nutritional outcomes 2, 4
• Avoid foods high in simple sugars (soft drinks, undiluted fruit juice), high-fat items, and caffeinated beverages. 2, 4

Antiemetic Use

Ondansetron may be administered to children >4 years when vomiting significantly hinders oral rehydration. 2, 4

• Reduces vomiting, improves ORS tolerance, and decreases need for IV fluids and hospitalization 2, 5, 6
• Use only after adequate hydration assessment; possible side effect is increased stool volume 4
• A single oral dose has been shown effective in facilitating ORT without significant adverse events 6

Metoclopramide should never be used in gastroenteritis—it is explicitly contraindicated and has no role in management. 2

Antibiotic Indications

Antibiotics are NOT routinely indicated because viral agents cause the majority of acute gastroenteritis. 1, 2

Consider antibiotics only when:

• Bloody diarrhea (dysentery) with high fever and systemic toxicity 1, 2, 7
• Watery diarrhea persisting >5 days 2, 4
• Stool culture identifies a treatable bacterial pathogen (Shigella, Salmonella, Campylobacter) 1, 2
• Patient is immunocompromised 2, 4

Obtain stool culture before initiating antibiotics when dysentery is present. 1, 7

Avoid antibiotics if Shiga-toxin-producing E. coli (STEC) O157 is suspected due to risk of hemolytic uremic syndrome. 4

Medications to Avoid

Loperamide and all antimotility agents are absolutely contraindicated in children <18 years—serious adverse events including ileus, respiratory depression, and deaths have been reported. 2, 7, 4

• Never use in bloody diarrhea regardless of age 7, 4
• Loperamide may be given to immunocompetent adults with acute watery diarrhea once adequately hydrated 2

Adsorbents, antisecretory drugs, and toxin binders should not be used—they are ineffective and shift focus away from appropriate fluid and nutritional therapy. 1, 2, 7

Hospital Admission Criteria

Admit patients with:

• Severe dehydration (≥10% fluid deficit) or signs of shock 1, 2
• Failure of oral rehydration therapy despite proper technique and antiemetic use 2, 4
• Altered mental status or severe lethargy 1, 2
• Intractable vomiting despite ondansetron 2
• Infants <3 months (lower threshold due to higher risk of complications) 2
• Bloody diarrhea with fever and systemic toxicity requiring monitoring for hemolytic uremic syndrome 2
• Significant comorbidities or immunocompromised state 2

Lower thresholds for admission in elderly patients (≥65 years) due to higher morbidity and mortality risk. 2

Infection Control Measures

Practice strict hand hygiene after toilet use, diaper changes, before food preparation, and before eating. 2, 7

• Use gloves and gowns when caring for patients with diarrhea 2, 7
• Clean and disinfect contaminated surfaces promptly 2
• Separate ill persons from well persons until at least 2 days after symptom resolution 2

Critical Red Flags Requiring Immediate Evaluation

• Bilious (green) vomiting suggests intestinal obstruction—requires emergency surgical evaluation 2
• Bloody stools with high fever indicate possible bacterial dysentery 1, 2
• Absent bowel sounds on auscultation—absolute contraindication to oral rehydration 2
• Persistent tachycardia or hypotension despite initial fluid resuscitation 2

Common Pitfalls to Avoid

Do not delay rehydration while awaiting diagnostic testing—initiate treatment promptly based on clinical assessment. 1, 2

Do not use sports drinks, apple juice, or soft drinks as primary rehydration fluids—they lack appropriate electrolyte balance and contain excess simple sugars that worsen diarrhea through osmotic effects. 2

Do not underestimate dehydration in elderly patients who may not manifest classic signs. 2

Stool cultures are rarely needed for typical watery diarrhea in immunocompetent patients—reserve for dysentery or prolonged symptoms. 1, 2