What is the recommended treatment regimen for a patient with acute gastroenteritis?

Prescription for Acute Gastroenteritis

Primary Treatment: Oral Rehydration Solution (ORS)

The cornerstone of acute gastroenteritis management is oral rehydration solution administered in small, frequent volumes, which successfully rehydrates over 90% of patients without requiring antiemetic medication. 1, 2

Rehydration Protocol Based on Dehydration Severity

Mild Dehydration (3-5% fluid deficit):

• Administer ORS at 50 mL/kg over 2-4 hours 1
• Replace ongoing losses: 10 mL/kg ORS for each watery stool and 2 mL/kg for each vomiting episode 1
• Use low-osmolarity ORS formulations, not sports drinks or juices 1

Moderate Dehydration (6-9% fluid deficit):

• Administer ORS at 100 mL/kg over 2-4 hours 1, 2
• Start with small volumes (5-10 mL every 1-2 minutes) using a spoon or syringe to prevent triggering vomiting 1, 2
• Gradually increase volume as tolerated 1
• Reassess hydration status after 2-4 hours 1

Severe Dehydration (≥10% fluid deficit):

• Requires intravenous rehydration with isotonic fluids (lactated Ringer's or normal saline) 1
• Continue IV fluids until pulse, perfusion, and mental status normalize 1
• Transition to ORS once patient improves 1

Pharmacological Management

Antiemetic Therapy

For children >4 years and adolescents with significant vomiting:

• Ondansetron 0.15 mg/kg intramuscularly or intravenously (maximum 16 mg/dose) 2, 3
• Use only when vomiting interferes with oral rehydration attempts 3
• Exercise special caution in children with heart disease due to QT interval prolongation risk 2, 3
• Avoid in patients with bloody diarrhea, fever suggesting bacterial infection, or suspected inflammatory diarrhea 2, 3

For children <4 years:

• Focus exclusively on proper ORS administration technique (5-10 mL every 1-2 minutes) 3
• Ondansetron is not recommended as first-line therapy in this age group 3

For adults:

• Ondansetron may be given after adequate hydration is achieved 2

Antimotility Agents

Loperamide:

• Never give to children <18 years with acute diarrhea 1, 2
• May be given to immunocompetent adults with acute watery diarrhea once adequately hydrated 1
• Avoid in bloody diarrhea or suspected bacterial infection 1

Adjunctive Therapies

Probiotics:

• May reduce symptom severity and duration in both adults and children 1

Zinc supplementation:

• Reduces diarrhea duration in children 6 months to 5 years in areas with high zinc deficiency prevalence or in malnourished children 1

Nutritional Management

Resume feeding immediately:

• Continue breastfeeding in infants throughout the episode 1
• Resume age-appropriate diet during or immediately after rehydration begins 1, 2
• Early refeeding is recommended rather than fasting or restrictive diets 1

Avoid:

• Foods high in simple sugars (soft drinks, undiluted apple juice) as they exacerbate diarrhea through osmotic effects 1
• Caffeinated beverages (coffee, tea, energy drinks) as they worsen symptoms through intestinal motility stimulation 1
• High-fat foods 1

Antimicrobial Therapy

Antimicrobials have limited usefulness since viral agents are the predominant cause 1

Consider antimicrobial therapy only in specific cases:

• Bloody diarrhea 1
• Recent antibiotic use (test for Clostridioides difficile) 1, 4
• Recent foreign travel 1
• Immunodeficiency 1
• Severe symptoms with confirmed bacterial pathogen 4

Medications to AVOID

Do not prescribe:

• Adsorbents, antisecretory drugs, or toxin binders (no demonstrated effectiveness) 1, 2
• Metoclopramide (counterproductive in diarrheal illness, accelerates transit) 1
• Antimotility agents in children <18 years (serious adverse events including ileus and deaths reported) 1, 2

Infection Control Measures

Implement strict precautions:

• Hand hygiene after toilet use, diaper changes, before food preparation and eating 1
• Use gloves and gowns when caring for patients with diarrhea 1
• Clean and disinfect contaminated surfaces promptly 1
• Separate ill persons from well persons until at least 2 days after symptom resolution 1

Indications for Hospitalization

Admit patients with:

• Severe dehydration (≥10% fluid deficit) 1
• Signs of shock or altered mental status 1
• Failure of oral rehydration therapy despite ondansetron 1
• Intractable vomiting 1
• Absent bowel sounds (ileus) 1
• Significant comorbidities or immunocompromised state 1
• Infants <3 months with moderate to severe dehydration 1

Critical Pitfalls to Avoid

• Do not delay rehydration while awaiting diagnostic testing 1
• Do not use sports drinks or apple juice as primary rehydration solutions for moderate to severe dehydration 1
• Do not unnecessarily restrict diet during or after rehydration 1
• Do not prescribe ondansetron without ensuring proper ORS administration technique 3
• Do not underestimate dehydration in elderly patients who may not manifest classic signs 1