A 27-year-old at 10 weeks’ gestation sits curled on the stretcher, lips cracked, ginger ale untouched at her feet. Every few minutes she dry-heaves into an emesis bag, then stares at the wall, dizzy when she tries to sit up. Her partner says she has not kept down food for days and the smell of coffee made her run to the bathroom. She is asking for “something safe for the baby,” but first you need to decide whether this is routine morning sickness or something much more dangerous.

— What’s your move? Read on.

Before you read
  • What dangerous mimics must be excluded before labeling this “just vomiting”?
  • Which antiemetics are reasonable in pregnancy, and when do you add thiamine, fluids, or admission?

When to Think of It

Think of this when a pregnant patient, especially in the first trimester, has persistent nausea/vomiting with inability to tolerate PO, weight loss, ketonuria, dehydration, orthostasis, or repeated ED visits. Escalate the concern if there is abdominal pain, fever, vaginal bleeding, focal peritoneal findings, or neurologic symptoms.

Sick or Not Sick

The key fork is well-appearing and tolerating fluids vs. dehydrated/ketotic/failed PO with electrolyte abnormalities or inability to protect nutrition. If she cannot keep down liquids, has significant dehydration, or you suspect another abdominal or obstetric process, she is not a discharge-from-triage patient.

The First Fifteen Minutes

  • Check vitals, orthostatics, bedside glucose, urine ketones, and fetal/obstetric status if appropriate gestational age/symptoms.
  • Normal saline 1–2 L IV bolus for dehydration/orthostasis, because volume repletion improves perfusion and reduces ketogenesis.
  • Dextrose-containing fluids only after thiamine if prolonged poor intake or concern for starvation; e.g., thiamine 100 mg IV now before dextrose, because it prevents precipitating Wernicke encephalopathy.
  • Pyridoxine (vitamin B6) 10–25 mg PO/IV every 8 hours for nausea, because it is safe and may reduce symptoms.
  • Doxylamine 12.5 mg PO every 6–8 hours or doxylamine-pyridoxine delayed release 10/10 mg PO (per product directions), because antihistamine antiemetic effect helps mild-to-moderate nausea.
  • Metoclopramide 10 mg IV/PO every 6 hours PRN for ongoing emesis, because dopamine antagonism improves gastric emptying and nausea.
  • Ondansetron 4–8 mg IV/PO every 6–8 hours PRN if symptoms persist, because 5-HT3 blockade is effective for refractory vomiting.
  • Prochlorperazine 5–10 mg IV/IM/PO every 6–8 hours PRN or promethazine 12.5–25 mg IV/IM/PO every 4–6 hours PRN if needed, because dopamine/antihistamine effects can control severe symptoms; monitor for sedation and dystonia.
  • Acetaminophen 650–1000 mg PO/IV if headache or discomfort is contributing, because pain worsens nausea; avoid NSAIDs in later pregnancy unless clearly indicated.

Definitive Care & Disposition

Treat reversible triggers: urinary infection, gastroenteritis, DKA, hepatitis, pancreatitis, appendicitis, ovarian pathology, or pregnancy complications. If she cannot tolerate PO after ED therapy, has electrolyte abnormalities, ketonuria with ongoing vomiting, weight loss, or recurrent visits, admit or place in observation for serial antiemetics, IV fluids, electrolyte correction, and nutrition support; severe refractory cases may need enteral feeding. OB involvement is appropriate for persistent hyperemesis, diagnostic uncertainty, or any concern for maternal-fetal compromise.

How This One Kills

The classic failure is anchoring on “morning sickness” and missing ectopic pregnancy, DKA, bowel obstruction, appendicitis, pyelonephritis, or cannabis hyperemesis — or giving dextrose before thiamine in a starved patient and triggering Wernicke injury.
The Differential — What Else Looks Like This
  • Cannabis Hyperemesis Syndrome — cyclic vomiting with chronic cannabis use, hot shower relief, and poor response to standard antiemetics; confusing it delays cessation counseling and symptom control.
  • Ectopic Pregnancy — pregnancy + abdominal pain, bleeding, syncope, or shoulder pain; missing it risks rupture and hemorrhagic shock.
  • Appendicitis — localized RLQ pain, fever, peritoneal signs; mislabeling it as hyperemesis delays surgery and increases perforation risk.
  • Pyelonephritis — fever, flank pain, urinary symptoms, CVA tenderness; confusing it with pregnancy vomiting misses sepsis and need for antibiotics.

The Second-Day Story

Hyperemesis does not always arrive as dramatic nonstop vomiting. Some patients are older, already partially treated, or have learned to sip just enough to avoid collapse, so the story becomes “can’t eat,” “everything tastes wrong,” or “I feel weak and dizzy when I stand.” Others present late with constipation, tachycardia, scant urine, or weight loss more than active emesis. The diagnosis is still clinical, but the warning lights are dehydration, ketones, and failure to function, not the volume of vomit on the floor.
Back to Our Patient
Back to our patient: the 27-year-old at 10 weeks with cracked lips, dry heaving, and dizziness is most consistent with hyperemesis gravidarum after you confirm no abdominal tenderness, fever, vaginal bleeding, or other red flags. She is risk-stratified as not safe for a quick discharge because she cannot tolerate PO and appears dehydrated, so you start IV fluids, give thiamine 100 mg IV before any dextrose, and add an antiemetic such as metoclopramide or ondansetron. If she improves, can drink, and labs are reassuring, she can go home with scheduled antiemetics and OB follow-up; if not, she needs observation or admission for ongoing IV therapy and electrolyte correction.
Patient Presentation to Attending
How you’d present this patient on the floor — tight, pertinent positives and negatives, no rambling
27-year-old G1P0 at 10 weeks by LMP with 4 days of persistent nausea and vomiting, unable to keep down food or liquids, here for dizziness and dehydration. She denies abdominal pain, vaginal bleeding, fever, diarrhea, dysuria, or focal neurologic symptoms, and she says this is worse than her baseline morning nausea. On exam she is tachycardic, dry-appearing, with benign abdomen and no peritoneal signs; urine shows ketones and her glucose is normal. I’m concerned for hyperemesis gravidarum versus a pregnancy-related or abdominal mimic, and I’d like IV fluids, thiamine before dextrose, antiemetics, electrolyte evaluation, and OB follow-up or observation if she can’t tolerate PO.

Study Directive

  • Memorize a stepwise ED algorithm for vomiting in pregnancy: confirm gestational age, screen for red flags, check hydration/ketones/glucose, treat with fluids + antiemetics, then decide discharge vs admit.
  • Write from memory the first-line pregnancy antiemetic options and their standard doses.
  • Practice a 30-second differential: hyperemesis, ectopic pregnancy, appendicitis, pyelonephritis, gastroenteritis, DKA, cannabis hyperemesis.
  • Review when to give thiamine and why dextrose can be dangerous in starvation.
  • Rehearse one oral presentation that includes obstetric, abdominal, urinary, and cannabis history without sounding scripted.

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