What is the appropriate assessment and treatment for a 38‑year‑old woman with six days of persistent vomiting and inability to retain oral intake after recent travel, concerning dehydration and electrolyte abnormalities?

Assessment and Management of Post-Travel Persistent Vomiting

This 38-year-old woman requires immediate intravenous rehydration followed by comprehensive stool testing for infectious causes, with oral rehydration solution transition once vomiting is controlled, and empiric antibiotics should be withheld until pathogen identification unless she develops high fever or signs of sepsis. 1

Immediate Assessment and Stabilization

Hydration Status Evaluation

• Assess for signs of severe dehydration requiring IV fluids: increased heart rate, postural dizziness, decreased urine output, lethargy, confusion, muscle weakness, and low blood pressure 2
• Check for electrolyte derangement symptoms including muscle cramps, abdominal pain, and altered mental status 2
• After 6 days of inability to retain oral intake, this patient likely has severe dehydration necessitating immediate intravenous fluid resuscitation 1, 3

Initial Fluid Resuscitation

• Start immediate IV fluids (Ringer's lactate or 0.9% normal saline) until mental status and peripheral perfusion normalize 3
• Reserve IV fluids for severe dehydration, shock, altered mental status, or failure of oral rehydration—all of which apply after 6 days of complete oral intolerance 1
• Once nausea improves, transition to oral rehydration solution (ORS) containing 50-90 mEq/L sodium as first-line therapy 1

Laboratory Assessment

• Obtain serum electrolytes (sodium, potassium, magnesium), renal function (urea, creatinine), and complete blood count immediately 2
• Check random urinary sodium—levels <20 mmol/L indicate sodium depletion requiring aggressive replacement 2
• Measure C-reactive protein and basic metabolic panel to assess inflammation and acid-base status 3

Diagnostic Workup

Stool Testing (Critical Priority)

• Order comprehensive stool studies immediately: bacterial culture, multiplex PCR panel, and Shiga toxin testing given the travel history 1
• Bacterial cultures must include Salmonella, Shigella, Campylobacter, Yersinia, and Vibrio species (particularly relevant with travel) 1, 3
• Shiga toxin testing is mandatory before considering any antibiotics—STEC infections are an absolute contraindication to antimicrobials due to hemolytic uremic syndrome risk 1
• Parasitic evaluation for Giardia lamblia, Cryptosporidium, Cyclospora, Cystoisospora, and Entamoeba histolytica 3, 4
• Test for Clostridioides difficile toxin if any antibiotic exposure in the prior 8-12 weeks 3

Interpretation Considerations

• Traveler's diarrhea typically occurs 4-14 days after arrival and results from bacterial pathogens in >90% of cases 2
• Multiplex PCR may detect non-viable organisms; positive results should be followed by culture when antimicrobial susceptibility could influence management 3

Antibiotic Decision Algorithm

When to WITHHOLD Antibiotics (Current Situation)

• Empiric antibiotics are contraindicated in acute watery diarrhea without confirmed pathogen in immunocompetent patients (strong recommendation) 1, 3
• Wait for stool study results to guide pathogen-specific therapy rather than empiric treatment 3

When Antibiotics Become Indicated

Antibiotics are only appropriate if the patient develops:

• Fever ≥38.5°C with signs of sepsis 1
• Frank blood in stools 1
• Severe illness requiring hospitalization for reasons beyond dehydration 1
• Immunocompromised status 1, 3

Antibiotic Selection (If Indicated Later)

• First-line: Azithromycin 500 mg daily for 3 days (or single 1-gram dose)—NOT fluoroquinolones due to widespread resistance 1
• Alternative for uncomplicated traveler's diarrhea: rifaximin (though less appropriate with vomiting) 2
• Pathogen-specific therapy once culture results available 3

Symptomatic Management

Antiemetic Therapy

• Administer ondansetron to control nausea and facilitate oral rehydration tolerance 1
• This is essential to transition from IV to oral fluids 1

Antimotility Agents

• Loperamide is contraindicated until vomiting resolves and bloody stools are excluded 1, 3
• Once appropriate: loperamide 4 mg initially, then 2 mg after each unformed stool (maximum 16 mg/day) 1
• Must avoid if fever or bloody stools develop 1

Oral Rehydration Protocol (Once Vomiting Controlled)

• Use reduced osmolarity ORS (50-90 mEq/L sodium) as primary intervention 1
• Replace 10 mL/kg for each watery stool 1, 3
• Continue until diarrhea resolves and clinical dehydration is fully corrected 1
• Target random urinary sodium >20 mmol/L as treatment endpoint 2

Dietary Management

Immediate Phase

• Resume age-appropriate normal diet immediately once rehydration begins—early refeeding is recommended 1
• Avoid fatty, spicy foods and caffeine-containing beverages during acute phase 1
• No routine dietary restrictions except lactose if intolerance develops 3

Fluid Restrictions

• If high-output diarrhea persists, restrict hypotonic/hypertonic fluids to <1000 mL daily 2
• Remaining fluid requirements should be met by isotonic glucose-saline solution 2

Monitoring and Follow-Up

Short-Term Monitoring

• Reassess hydration status every 2-4 hours until stable 1
• Monitor for development of fever, bloody stools, or worsening symptoms that would change management 1
• Watch for signs requiring additional IV fluids: worsening tachycardia, postural dizziness, decreased urine output, altered mental status 1

Reassessment Triggers

• If no improvement within 48-72 hours or symptoms persist beyond 7 days, reassess for antibiotic resistance, non-infectious causes, or need for hospitalization 1
• Modify treatment once stool studies identify specific pathogen 1
• Consider non-infectious etiologies if diarrhea persists beyond 14 days with negative infectious workup 3

Critical Pitfalls to Avoid

• Do not delay rehydration while awaiting diagnostic results—dehydration poses the immediate threat after 6 days of no oral intake 3
• Never give empiric antibiotics before Shiga toxin results are available 1
• Do not use loperamide with ongoing vomiting, fever, or bloody diarrhea 1, 3
• Avoid over-interpreting positive multiplex PCR without clinical correlation 3
• Do not forget to check for recent antibiotic exposure and test for C. difficile if present 3