What is the best course of action for a 21-week pregnant woman with hyperemesis (excessive vomiting) and diarrhea for 14 hours, resulting in significant weight loss of 5 pounds?

Immediate Hospitalization for IV Fluid Resuscitation and Thiamine Supplementation

This 21-week pregnant woman requires immediate hospitalization for intravenous fluid resuscitation, electrolyte replacement, thiamine supplementation to prevent Wernicke's encephalopathy, and antiemetic therapy—the 5-pound weight loss over 14 hours with combined vomiting and diarrhea represents severe dehydration and meets criteria for hyperemesis gravidarum requiring urgent intervention. 1

Immediate Actions Upon Presentation

Stabilization Protocol

• Start aggressive IV fluid resuscitation immediately to correct dehydration, which often improves associated metabolic abnormalities 1
• Administer thiamine 200-300 mg IV daily for at least 3-5 days before any dextrose-containing fluids to prevent Wernicke's encephalopathy—pregnancy depletes thiamine stores rapidly, and with 14 hours of combined vomiting and diarrhea, this patient is at high risk 1
• Replace electrolytes with particular attention to potassium and magnesium levels, as these are commonly depleted in hyperemesis with diarrhea 1

Critical Diagnostic Workup

• Check electrolyte panel immediately looking for hyponatremia, hypokalemia, metabolic hypochloremic alkalosis 1, 2
• Obtain liver function tests, as approximately 50% of hyperemesis patients have abnormal AST and ALT 1
• Urinalysis for ketonuria to confirm severity 1
• Thyroid function tests, as hyperthyroidism is associated with hyperemesis and can cause diarrhea 1, 3
• Abdominal ultrasound to rule out hepatobiliary causes (gallstones/cholecystitis) and assess fetal growth 1

Antiemetic Management Algorithm

First-Line Therapy

• Doxylamine 10-20 mg combined with pyridoxine (vitamin B6) 10-20 mg every 8 hours is the preferred initial antiemetic throughout pregnancy 1
• Alternative first-line agents include promethazine or prochlorperazine if doxylamine-pyridoxine combination is insufficient 1

Second-Line Escalation

• Metoclopramide is the preferred second-line agent when first-line antihistamines fail, with less drowsiness and dystonia compared to promethazine 1
• Ondansetron can be used as second-line therapy at 21 weeks gestation without first-trimester concerns about congenital heart defects 1
• Switch from PRN to scheduled around-the-clock dosing rather than intermittent administration for better symptom control 1
• Monitor QT interval if using ondansetron, especially given likely electrolyte abnormalities 1

Third-Line for Refractory Cases

• Methylprednisolone 16 mg IV every 8 hours for up to 3 days, then taper over 2 weeks to lowest effective dose (maximum 6 weeks) if both ondansetron and metoclopramide fail 1
• At 21 weeks, the first-trimester cleft palate risk is not applicable 1

Nutritional Management

Refeeding Protocol

• Start with small, frequent meals using BRAT diet (bananas, rice, applesauce, toast) and advance slowly over days to prevent refeeding syndrome 1
• Continue thiamine supplementation throughout refeeding to prevent Wernicke's encephalopathy during nutritional restoration 1
• Monitor for refeeding syndrome with serial electrolytes, particularly phosphate, potassium, and magnesium 1

Escalation if Oral Intake Fails

• Consider nasojejunal feeding over nasogastric if unable to maintain 1000 kcal/day for several days despite maximal antiemetics and progressive weight loss continues 1
• Nasojejunal feeding is better tolerated than nasogastric and should be considered before total parenteral nutrition 1

Monitoring Requirements

Objective Markers of Improvement

• Weight stabilization or gain (not continued loss) is critical for demonstrating clinical improvement 1
• Resolution of ketonuria and normalization of electrolytes on laboratory reassessment 1
• Sustained oral intake and reduced vomiting frequency 1
• Serial PUQE (Pregnancy-Unique Quantification of Emesis) scores to track symptom severity over time 1

Fetal Monitoring

• Monthly fetal growth monitoring scans from viability in severe cases with insufficient gestational weight gain 1
• Untreated hyperemesis is associated with low birth weight, small for gestational age infants, and premature delivery 1

Critical Pitfalls to Avoid

• Never give dextrose-containing IV fluids before thiamine administration—this can precipitate Wernicke's encephalopathy 1
• Do not use PRN antiemetic dosing in severe cases—scheduled around-the-clock administration is essential for refractory symptoms 1
• Do not discharge until weight stabilizes and oral intake is sustained—intermittent IV treatments without continuous coverage lead to symptom worsening 1
• Withdraw phenothiazines or metoclopramide immediately if extrapyramidal symptoms develop 1

Multidisciplinary Involvement

Coordinate care involving maternal-fetal medicine, gastroenterology, nutrition services, and mental health professionals for this severe presentation, preferably at a tertiary care center experienced in high-risk pregnancies 1. Mental health support is important as anxiety and depression are common with severe hyperemesis 1.