What is the best management approach for a 25-year-old active duty male presenting with a one-day history of nausea and vomiting, tachycardia, and low-grade fever, with an unremarkable abdominal exam and normal orthostasis, after initiating IV fluids and laboratory tests including Complete Blood Count (CBC), Comprehensive Metabolic Panel (CMP), and lipase?

Management of 25-Year-Old with Acute Nausea/Vomiting, Tachycardia, and Low-Grade Fever

Your planned approach is appropriate for acute gastroenteritis, but you must ensure follow-up contact occurs within 24-48 hours and explicitly instruct the patient to return immediately if vomiting persists beyond 24 hours, fever worsens, or abdominal pain develops, as these could indicate evolving surgical pathology or metabolic decompensation. 1, 2

Critical Initial Assessment Completed

Your workup appropriately includes:

• CBC, CMP, and lipase to exclude metabolic causes (hypercalcemia, electrolyte abnormalities, hyperglycemia), assess for dehydration, and rule out pancreatitis 1, 3
• IV fluid resuscitation addresses the tachycardia, which likely reflects volume depletion rather than sepsis given normal orthostatics 1, 4
• Normal orthostatics make significant volume depletion less likely, though tachycardia suggests some degree of hypovolemia 4

Essential Additional History Before Discharge

Before discharging, you must specifically ask about:

• Cannabis use history - Cannabis Hyperemesis Syndrome (CHS) is extremely common in this demographic and requires 6 months of cessation for definitive diagnosis 1
• Medication and supplement use - Many drugs cause nausea/vomiting as adverse effects 3, 4
• Timing relative to meals - Vomiting within 1-2 hours of eating suggests gastroparesis or gastric outlet obstruction; immediate vomiting suggests psychogenic causes 5, 3
• Characteristics of vomitus - Bilious suggests small bowel obstruction; undigested food suggests gastroparesis 3, 6

Ondansetron Discharge Prescription

Ondansetron 8 mg orally every 8-12 hours as needed is appropriate for acute viral gastroenteritis, with a maximum of 24 mg per day 7. Consider prescribing the orally disintegrating tablet (ODT) formulation rather than standard tablets, as absorption is superior in actively vomiting patients 2. The typical discharge prescription should be for 3-5 days maximum 7, 4.

Important caveat: Ondansetron may increase stool volume/diarrhea in gastroenteritis, so warn the patient this is expected and not a reason to stop the medication 1.

Critical Red Flags Requiring Immediate Return

Explicitly instruct the patient to return immediately for:

• Vomiting persisting beyond 24 hours despite ondansetron - this warrants imaging to exclude obstruction and consideration of alternative diagnoses 1, 3
• Development or worsening of abdominal pain - could indicate appendicitis, cholecystitis, or other surgical pathology 3, 4
• Fever above 101°F (38.3°C) or persistent fever beyond 48 hours - suggests bacterial infection requiring antibiotics 4
• Inability to tolerate oral fluids - requires return for additional IV hydration 1, 4
• Signs of dehydration - decreased urination, dizziness, confusion 4, 6

Laboratory Result Follow-Up Protocol

You must personally review all laboratory results within 24 hours and contact the patient with any abnormalities, particularly:

• Elevated lipase (>3x upper limit of normal suggests pancreatitis requiring admission) 1
• Hypercalcemia (>12 mg/dL requires urgent treatment) 1, 2
• Severe electrolyte abnormalities - hypokalemia <3.0 mEq/L, hyponatremia <130 mEq/L, or metabolic alkalosis suggest significant vomiting and may require oral or IV electrolyte replacement 1, 2
• Elevated WBC with left shift - suggests bacterial infection 3
• Transaminitis - could indicate hepatitis or other hepatobiliary pathology 5

If Symptoms Persist Beyond 48-72 Hours

Should the patient contact you with persistent symptoms, the next steps are:

• Add metoclopramide 10 mg orally three times daily before meals - this is superior to ondansetron alone for gastroparesis and provides complementary dopamine receptor antagonism 1, 2
• Consider prochlorperazine 10 mg orally/rectally every 6-8 hours as an alternative dopamine antagonist if metoclopramide is contraindicated 1, 2
• Obtain abdominal imaging (CT or ultrasound) to exclude structural causes if not already done 1, 3
• Consider upper endoscopy if symptoms persist beyond 1 week to exclude gastritis, peptic ulcer disease, or gastric outlet obstruction 5, 1

Common Pitfalls to Avoid

• Never discharge without ensuring 24-48 hour follow-up contact - acute gastroenteritis can evolve into surgical emergencies 1, 3
• Do not assume viral gastroenteritis in the presence of severe abdominal pain - this requires imaging to exclude appendicitis, cholecystitis, or bowel obstruction 3, 4
• Monitor for extrapyramidal symptoms if you add metoclopramide or prochlorperazine, particularly in young males who are at higher risk 1, 2
• Avoid repeated antiemetic prescriptions without reassessment - chronic symptoms (>4 weeks) require comprehensive evaluation for underlying causes 3, 8