What is the recommended evaluation and treatment for persistent gastroenteritis and vomiting lasting three days, accompanied by anorexia, dysphagia, and headaches?

Evaluation and Treatment of Acute Gastroenteritis with Persistent Vomiting

Adam requires immediate hydration assessment and oral rehydration therapy as the cornerstone of management, with ondansetron 8 mg orally to facilitate fluid tolerance if vomiting prevents adequate oral intake. 1, 2

Immediate Assessment Priorities

Assess hydration status first by examining for signs of dehydration including dry mucous membranes, decreased skin turgor, tachycardia, decreased urine output, and orthostatic vital signs. 1 The presence of headache with persistent vomiting and inability to drink raises concern for dehydration and potential electrolyte disturbances. 3

Rule out alarm features that would require urgent imaging or specialist consultation:

• Severe or persistent headache with altered mental status (concern for CNS pathology requiring lumbar puncture or head CT) 4
• Bilious vomiting or severe abdominal pain (concern for obstruction) 1
• Blood in vomit or stool 1
• Focal neurologic deficits 4

Diagnostic Evaluation

For a previously healthy patient with 3 days of gastroenteritis symptoms and no alarm features, acute viral gastroenteritis is the most likely diagnosis and requires minimal laboratory testing. 3, 5

Obtain basic laboratory studies only if:

• Signs of moderate-to-severe dehydration are present (comprehensive metabolic panel to assess electrolytes and renal function) 3
• Symptoms persist beyond 7 days (consider complete blood count, comprehensive metabolic panel, stool studies) 3, 5
• Alarm symptoms are present 3

Imaging is not indicated for uncomplicated acute gastroenteritis in the absence of alarm symptoms. 3, 5

Treatment Algorithm

Step 1: Fluid Repletion (Primary Treatment)

Begin oral rehydration solution (ORS) immediately with small, frequent volumes (5 mL every minute initially using a spoon or syringe), gradually increasing as tolerated. 1 This takes absolute precedence over antiemetic therapy. 1, 2

Replace ongoing losses by giving 10 mL/kg of ORS for each episode of vomiting or diarrhea. 1

Escalate to IV rehydration only if severe dehydration is present or oral intake remains impossible despite antiemetic therapy. 1

Step 2: Antiemetic Therapy (Adjunctive)

Administer ondansetron 8 mg orally once to facilitate oral rehydration tolerance. 2, 5 This can be repeated every 8-12 hours as needed for ongoing symptoms. 2

Critical caveat: Ondansetron is not a substitute for fluid repletion and should only be used as an adjunct to facilitate oral hydration. 2 It may increase stool volume/diarrhea as a side effect, but this does not outweigh its benefit in controlling vomiting. 1

Alternative antiemetics if ondansetron is unavailable or ineffective include prochlorperazine, metoclopramide, or haloperidol. 6

Step 3: Early Refeeding

Resume normal diet immediately once adequate hydration is achieved—do not delay solid foods for 24 hours. 1 Offer age-appropriate foods including starches, cereals, yogurt, fruits, and vegetables while avoiding foods high in simple sugars and fats. 1

Outpatient Management Plan

Prescribe ondansetron 8 mg tablets with instructions to take 1 tablet by mouth every 8 hours as needed for nausea/vomiting, emphasizing continued oral hydration with each dose. 2

Provide explicit return precautions:

• Increasing lethargy or difficulty arousing 1
• Decreased urine output 1
• Intractable or bilious vomiting 1
• Blood in vomit or stool 1
• Severe abdominal pain 1
• Worsening symptoms despite treatment 1

Common Pitfalls to Avoid

Do not withhold oral rehydration while waiting for antiemetic effect—small, frequent sips should begin immediately. 1

Do not assume gastroparesis or other chronic conditions in a patient with acute symptoms lasting only 3 days without prior episodes. 4, 7 Gastroparesis evaluation (gastric emptying scintigraphy) is reserved for chronic symptoms lasting 4 weeks or longer. 4, 7

Do not order extensive imaging or endoscopy for uncomplicated acute gastroenteritis in a young, previously healthy patient without alarm features. 4, 3

Recognize that headache is common in acute viral gastroenteritis (occurring in 21% of cases) and does not automatically warrant lumbar puncture unless it is severe, persistent, progressive, or accompanied by altered mental status or focal neurologic deficits. 4