What is the best course of action for a 20-week pregnant woman with symptoms of diarrhea, vomiting, and significant weight loss, who is at risk for dehydration and can only tolerate 8 ounces of fluid?

Immediate Hospitalization for Intravenous Rehydration

This 20-week pregnant woman requires immediate hospitalization for intravenous fluid resuscitation—she has severe dehydration with hyperemesis gravidarum and cannot maintain adequate oral hydration.

Severity Assessment

This patient meets criteria for severe dehydration and hyperemesis gravidarum based on:

• Acute 5-pound weight loss in 24 hours (approximately 3-5% body weight loss, indicating at least moderate to severe dehydration) 1, 2
• Inability to maintain oral hydration (only tolerating 8 ounces of fluid, far below the 2-4 liters needed for rehydration) 1
• Persistent vomiting preventing adequate intake (characteristic of hyperemesis gravidarum requiring hospitalization) 3, 4
• Ongoing diarrhea with vomiting (dual fluid losses exceeding replacement capacity) 1

Immediate Management Protocol

Intravenous Fluid Resuscitation

Administer isotonic crystalloid (lactated Ringer's or normal saline) intravenously as boluses until clinical improvement occurs 1, 2. For severe dehydration, give up to 20 mL/kg body weight until pulse, perfusion, and mental status normalize 1.

• Add potassium chloride (20 mEq/L) to maintenance fluids after initial resuscitation, guided by daily electrolyte monitoring 1, 5
• Normal saline (0.9% NaCl) with additional potassium is the most appropriate intravenous hydration 5

Critical Thiamine Supplementation

Administer thiamine (vitamin B1) immediately before any dextrose-containing fluids or parenteral nutrition 3, 5. Give either:

• Intravenous vitamin B complex (Pabrinex®), OR
• Oral thiamine 100 mg three times daily 5

This prevents Wernicke's encephalopathy, central pontine myelinolysis, and death—life-threatening complications of severe hyperemesis 3.

Antiemetic Therapy

Once intravenous access is established, initiate combination antiemetic therapy 5:

First-line options:

• Ondansetron (safe and effective in pregnancy, with only minimal absolute risk increase for orofacial clefting that is outweighed by risks of untreated hyperemesis) 5
• Antihistamines (H1 blockers) or phenothiazines 5
• Doxylamine/pyridoxine combination 6, 5

Second-line if first-line fails:

• Metoclopramide (administer by slow IV bolus over at least 3 minutes to minimize extrapyramidal effects) 5
• Combination therapy with multiple antiemetics if single agents fail 5

Electrolyte Monitoring and Correction

Monitor daily for 3, 4:

• Hyponatremia and hypokalaemia
• Metabolic hypochloraemic alkalosis
• Ketonuria (though this does NOT indicate dehydration severity) 5
• Elevated hematocrit and urine specific gravity
• Liver function abnormalities
• Thyroid function (biochemical hyperthyroidism may occur with elevated hCG) 3

Replacement of Ongoing Losses

After initial resuscitation, replace ongoing losses 1:

• For each diarrheal stool: 120-240 mL of oral rehydration solution (ORS) when able to tolerate oral intake
• For each vomiting episode: 2 mL/kg of ORS
• Total maintenance: Up to 2 L/day as tolerated

When Oral Rehydration Alone Would Be Appropriate

Oral rehydration therapy is first-line only for mild to moderate dehydration (50-100 mL/kg ORS over 3-4 hours) 1, 2. This patient has exceeded that threshold by:

• Losing 5 pounds in one day (severe acute dehydration)
• Failing to maintain even minimal oral intake (only 8 ounces tolerated)
• Having dual fluid losses (vomiting AND diarrhea) 1

Critical Pitfalls to Avoid

• Never delay IV rehydration in a pregnant woman who cannot maintain oral intake with ongoing losses—this risks maternal and fetal compromise 1, 2
• Never give dextrose-containing fluids before thiamine supplementation—this precipitates Wernicke's encephalopathy 3, 5
• Do not use antimotility agents (loperamide) for the diarrhea—these are contraindicated and potentially harmful 1
• Do not withhold ondansetron due to cleft concerns—the absolute risk increase is minimal and far outweighed by risks of severe hyperemesis 5
• Do not rely on ketonuria to assess dehydration severity—it is not a valid indicator 5

Nutritional Management During Recovery

Once rehydration begins and vomiting improves 1:

• Resume age-appropriate usual diet immediately after rehydration
• Do not restrict diet—early feeding improves outcomes
• Continue throughout recovery without prolonged fasting periods

Indications for Continued Hospitalization

Keep hospitalized until 3, 4, 5:

• Able to maintain oral hydration (at least 1-2 liters daily)
• Vomiting controlled with oral antiemetics
• Electrolytes normalized
• Weight stabilized or improving
• No ketonuria or metabolic derangements