What is the initial management for a patient presenting with gastroenteritis?

Initial Management of Gastroenteritis

The cornerstone of initial management for gastroenteritis is immediate oral rehydration therapy (ORT) using low-osmolarity oral rehydration solution (ORS), which should be started promptly without waiting for diagnostic testing, as this approach successfully rehydrates over 90% of patients and is as effective as intravenous therapy for mild to moderate dehydration. 1, 2, 3

Immediate Assessment and Hydration Status

Begin by rapidly assessing dehydration severity through specific clinical signs 2:

Mild dehydration (3-5% fluid deficit):

• Slightly dry mucous membranes
• Normal mental status
• Normal vital signs 2

Moderate dehydration (6-9% fluid deficit):

• Loss of skin turgor with tenting when pinched
• Dry mucous membranes
• Decreased urine output
• Mild tachycardia 2

Severe dehydration (≥10% fluid deficit):

• Severe lethargy or altered consciousness
• Prolonged skin tenting (>2 seconds)
• Cool, poorly perfused extremities
• Decreased capillary refill
• Rapid, deep breathing indicating acidosis 2

Rehydration Protocol Based on Severity

For Mild to Moderate Dehydration

Initiate ORS immediately using the following specific approach 1, 2, 3:

• Start with small, frequent volumes: 5-10 mL every 1-2 minutes using a spoon or syringe, especially if vomiting is present 2, 3
• Gradually increase volume as tolerated without triggering vomiting 2
• Total rehydration dose: 50-100 mL/kg ORS over 3-4 hours 2, 3
• Replace ongoing losses: 10 mL/kg (approximately 120-240 mL for children >10 kg) after each watery stool and 2 mL/kg after each vomiting episode 2

Use low-osmolarity ORS formulations approaching WHO-recommended concentrations (Na 90 mM, K 20 mM, Cl 80 mM, HCO3 30 mM, glucose 111 mM) rather than sports drinks, juices, or soft drinks which have inappropriate electrolyte content 1, 2, 3

Consider nasogastric ORS administration at 15 mL/kg/hour for patients who cannot tolerate oral intake adequately but are not in shock 2, 3

For Severe Dehydration

Administer intravenous isotonic fluids immediately (lactated Ringer's or normal saline) in 20 mL/kg boluses until pulse, perfusion, and mental status normalize 2, 4

Transition to ORS to replace remaining fluid deficit once the patient improves and can tolerate oral intake 2, 4

Nutritional Management

Resume age-appropriate diet during or immediately after rehydration rather than prolonged fasting or restrictive diets 1, 2, 4

Continue breastfeeding on demand throughout the illness in infants 1, 2

Avoid foods high in simple sugars (soft drinks, undiluted apple juice) as they can exacerbate diarrhea through osmotic effects 2

Pharmacological Considerations

Antiemetics

Ondansetron may be administered to children >4 years and adolescents with significant vomiting to facilitate oral rehydration and reduce hospitalization rates 2

This is particularly useful when vomiting interferes with ORS administration 5

Antimotility Agents

Loperamide is contraindicated in children <18 years with acute diarrhea due to risk of complications 2, 4, 6

For adults with watery diarrhea: Loperamide may be given once adequately hydrated, starting with 4 mg initially, then 2 mg after each unformed stool (maximum 16 mg/day) 1, 2, 6

Avoid loperamide if: bloody diarrhea, fever, or signs of inflammatory/invasive infection are present 2, 4

Antimicrobial Therapy

Do not routinely prescribe antibiotics for acute gastroenteritis, as viral agents are the predominant cause 2, 4

Consider antimicrobials only for specific indications 1, 4:

• Bloody diarrhea with fever and systemic toxicity
• Infants <3 months with suspected bacterial etiology
• Immunocompromised patients
• Recent antibiotic use (test for C. difficile)
• Recent foreign travel
• Positive stool culture for treatable bacterial pathogen

Diagnostic Testing

Stool testing is not needed for mild symptoms resolving within one week 1, 2

Obtain stool studies when 1, 2:

• Fever, tenesmus, or bloody stools present (suggesting inflammatory etiology)
• Symptoms persist >7 days
• Severe dehydration or systemic toxicity
• Recent antibiotic exposure
• Immunocompromised status

Screen for inflammatory markers (fecal lactoferrin or leukocytes) to guide culture decisions, as this increases yield for invasive pathogens (Salmonella, Shigella, Campylobacter) 1

Infection Control

Implement strict hand hygiene with vigorous handwashing using soap after toilet use, diaper changes, before food preparation, and before eating 1, 2

Use gloves and gowns when caring for patients with diarrhea 2

Clean and disinfect contaminated surfaces promptly, though note that many germicidal chemicals are ineffective against rotavirus; detergents should be used for laundering fecally contaminated items 1

Isolate ill persons from well persons until at least 2 days after symptom resolution 2

Critical Pitfalls to Avoid

Do not delay rehydration while awaiting diagnostic test results—begin ORS immediately 2, 4

Do not use inappropriate fluids (sports drinks, apple juice, sodas) as primary rehydration solutions for moderate to severe dehydration due to high osmolality and inappropriate electrolyte composition 2, 3

Do not unnecessarily restrict diet during or after rehydration, as early refeeding reduces illness severity and duration 1, 2

Do not underestimate dehydration in elderly patients, who may not manifest classic signs and have higher mortality risk 2

Do not give antimotility drugs to children or in cases of bloody diarrhea, as this increases risk of complications including toxic megacolon and hemolytic uremic syndrome 2, 4

Monitoring and Reassessment

Reassess hydration status after 2-4 hours of ORS therapy 2

If still dehydrated: Re-estimate fluid deficit and restart rehydration protocol 2

Monitor for warning signs requiring hospitalization 2:

• Failure of oral rehydration therapy
• Persistent altered mental status
• Intractable vomiting despite antiemetics
• Signs of severe dehydration despite treatment
• Absent bowel sounds (absolute contraindication to oral fluids)