What is the recommended treatment approach for a patient with gastroenteritis, considering hydration status and potential underlying medical conditions?

Treatment of Gastroenteritis

Oral rehydration solution (ORS) is the first-line treatment for mild to moderate dehydration in gastroenteritis, regardless of age, and should be initiated immediately without waiting for diagnostic testing. 1

Assess Hydration Status First

Evaluate dehydration severity through specific clinical signs to guide treatment intensity 1, 2:

• Mild dehydration (3-5% fluid deficit): Slightly dry mucous membranes, normal mental status, adequate urine output 1
• Moderate dehydration (6-9% fluid deficit): Dry mucous membranes, decreased skin turgor, reduced urine output, mild tachycardia 1, 2
• Severe dehydration (≥10% fluid deficit): Altered mental status, prolonged capillary refill (>2 seconds), severe lethargy, signs of shock, absent tears, sunken eyes 1

The most accurate assessment is acute weight change if premorbid weight is known; prolonged skin retraction time and abnormal capillary refill are the most reliable clinical predictors when weight is unavailable 2.

Rehydration Protocol Based on Severity

Mild to Moderate Dehydration

Administer reduced osmolarity ORS as first-line therapy 1:

• Mild dehydration: Give 50 mL/kg ORS over 2-4 hours 1, 2
• Moderate dehydration: Give 100 mL/kg ORS over 2-4 hours 1
• Start with small volumes (5-10 mL every 1-2 minutes using a spoon or syringe) and gradually increase as tolerated 2, 3
• Replace ongoing losses: 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

Nasogastric ORS administration may be considered for patients with moderate dehydration who cannot tolerate oral intake or refuse to drink adequately 1.

Severe Dehydration

Initiate intravenous rehydration immediately 1:

• Administer isotonic fluids (lactated Ringer's or normal saline) in 20 mL/kg boluses until pulse, perfusion, and mental status normalize 1
• Continue IV therapy until the patient awakens, has no aspiration risk, and has no evidence of ileus 1
• Transition to ORS to replace remaining deficit once patient improves 1, 2
• In patients with ketonemia, initial IV hydration may be needed to enable tolerance of oral rehydration 1

Nutritional Management

Resume age-appropriate diet during or immediately after rehydration is completed 1:

• Continue breastfeeding throughout the diarrheal episode in infants 1
• For bottle-fed infants, provide full-strength formula immediately upon rehydration 1
• Early refeeding reduces severity and duration of illness 2
• Avoid foods high in simple sugars (soft drinks, undiluted apple juice) as they can exacerbate diarrhea through osmotic effects 2
• Limit or avoid caffeinated beverages as they stimulate intestinal motility and worsen diarrhea 2

Pharmacological Adjuncts (Once Adequately Hydrated)

Antiemetics

Ondansetron may be given to facilitate oral rehydration when vomiting is significant 1:

• Children >4 years and adolescents: 0.15 mg/kg (maximum 16 mg/dose) orally, intramuscularly, or intravenously 3
• Reduces vomiting, facilitates ORT, and decreases need for IV rehydration and hospitalization 4, 5, 6, 7
• Exercise caution in patients with cardiac conditions due to potential QT prolongation 3
• Avoid in bloody diarrhea with fever suggesting bacterial/inflammatory etiology 3

Antimotility Agents

Loperamide should NOT be given to children <18 years of age with acute diarrhea due to risk of serious adverse events including ileus and deaths 1, 8:

• Adults only: May give loperamide (4 mg initially, then 2 mg after each loose stool, maximum 16 mg/day) for acute watery diarrhea once adequately hydrated 1
• Avoid at any age in inflammatory diarrhea, bloody diarrhea with fever, or suspected toxic megacolon 1, 8
• Contraindicated in children <2 years due to risks of respiratory depression and cardiac adverse reactions 8

Probiotics

Probiotic preparations may be offered to reduce symptom severity and duration in immunocompetent adults and children 1.

Zinc Supplementation

Oral zinc reduces diarrhea duration in children 6 months to 5 years of age in areas with high zinc deficiency prevalence or in malnourished children 1.

Antimicrobial Therapy

Empiric antimicrobial therapy is NOT recommended in most patients with acute watery diarrhea without recent international travel 1:

• Exceptions: immunocompromised patients, young infants who are ill-appearing, or patients with dysentery (bloody diarrhea with fever and systemic toxicity) 1, 9
• Azithromycin is first-line for suspected Shigella or invasive bacterial pathogens (500 mg daily for 3 days or 1 gram single dose) 9
• Avoid antibiotics in STEC O157 and Shiga toxin 2-producing E. coli due to increased risk of hemolytic uremic syndrome 1, 9
• Modify or discontinue antimicrobials when a clinically plausible organism is identified 1

Critical Pitfalls to Avoid

• Do not delay rehydration while awaiting diagnostic testing; initiate ORS immediately 2
• Do not use sports drinks or apple juice as primary rehydration solutions for moderate to severe dehydration 2
• Never give loperamide to children or in cases of bloody diarrhea 1, 8
• Do not restrict diet unnecessarily during or after rehydration 1
• Do not use metoclopramide in gastroenteritis as it has no role and may worsen outcomes 2
• Do not start broad-spectrum antibiotics empirically when rehydration alone is indicated 9

Infection Control

Practice proper hand hygiene, use gloves and gowns when caring for patients with diarrhea, clean and disinfect contaminated surfaces promptly, and separate ill persons from well persons until at least 2 days after symptom resolution 2.

Hospitalization Criteria

Admit patients with severe dehydration (≥10% fluid deficit), signs of shock, failure of oral rehydration therapy, altered mental status, intractable vomiting despite antiemetics, or significant comorbidities that increase risk of complications 2.