What is the initial workup and management for a patient presenting with nausea and vomiting?

Initial Workup and Management of Nausea and Vomiting

Immediate Assessment and Risk Stratification

Begin by determining if this is acute (≤7 days) or chronic (≥4 weeks) presentation, as this fundamentally changes your diagnostic and therapeutic approach. 1, 2

Key Historical Elements to Obtain

• Timing and duration: Acute onset suggests gastroenteritis, food poisoning, medication effect, or acute migraine; chronic suggests gastroparesis, functional disorders, or malignancy 3, 2
• Medication review: Recent initiation of opioids, chemotherapy, antibiotics, or antifungals is a common culprit 4, 3
• Associated symptoms requiring urgent evaluation: Severe headache (CNS pathology), acute abdominal pain (surgical abdomen), fever with altered mental status (infection/sepsis), or signs of dehydration 3, 2
• Metabolic red flags: Check for constipation, hypercalcemia, uremia, diabetic ketoacidosis, or electrolyte disturbances 4, 3
• Pregnancy status in women of childbearing age 3, 2

Physical Examination Priorities

• Hydration status: Assess mucous membranes, skin turgor, orthostatic vital signs, and mental status to determine need for IV fluids 5
• Abdominal examination: Look for peritoneal signs, distension, or masses suggesting obstruction or surgical pathology 3
• Neurologic examination: If headache or altered mental status present, evaluate for increased intracranial pressure or meningismus 3

Initial Laboratory and Imaging Workup

For Acute Nausea/Vomiting Without Alarm Features

• Minimal testing needed: Urine pregnancy test in women of childbearing age 3
• Consider basic metabolic panel only if: Severe or prolonged symptoms, concern for dehydration, or suspicion of metabolic cause 3

For Acute Nausea/Vomiting With Alarm Features or Moderate-Severe Symptoms

• Complete metabolic panel: To assess electrolytes, renal function, glucose, and calcium 3
• Complete blood count: To evaluate for infection or anemia 3
• Urinalysis: To assess for urinary tract infection or ketones 3
• Lipase/amylase: If epigastric pain suggests pancreatitis 3
• Thyroid-stimulating hormone: If chronic symptoms or other signs of thyroid disease 3
• Abdominal imaging: Plain radiographs for suspected obstruction; CT abdomen if acute abdomen or unclear diagnosis 3
• Head CT: If severe headache, altered mental status, or focal neurologic signs suggest intracranial pathology 3

For Chronic Nausea/Vomiting (≥4 weeks)

• Esophagogastroduodenoscopy (EGD): First-line test if alarm symptoms (weight loss, dysphagia, age >50 with new onset) or risk factors for gastric malignancy 3
• Gastric emptying study: If gastroparesis suspected (early satiety, postprandial fullness, diabetes) 3
• Consider: Small bowel imaging, metabolic workup, and psychiatric evaluation if initial testing unrevealing 3, 6

Pharmacologic Management

For Acute Vomiting (First-Line)

Ondansetron (5-HT3 antagonist) is the preferred initial agent, with sublingual formulation (4-8 mg every 8-12 hours) potentially improving absorption in actively vomiting patients. 5, 7

For Acute Vomiting (Alternative or Adjunctive Agents)

If ondansetron fails or is contraindicated, use dopamine antagonists on a fixed schedule rather than as-needed 8:

• Metoclopramide 10-20 mg PO/IV every 6 hours 8, 9
• Prochlorperazine 5-10 mg PO/IV every 6 hours or 25 mg rectal suppository 5, 8, 9
• Promethazine 12.5-25 mg PO/IV/rectal every 4-6 hours 5, 10

For Refractory or Intractable Vomiting

Immediately start a dopamine receptor antagonist on a fixed schedule (not as-needed) to maintain constant therapeutic levels, prioritizing metoclopramide 10-20 mg every 6 hours or haloperidol 0.5-2 mg every 4-6 hours. 8

If symptoms persist after 24-48 hours, escalate therapy by:

• Adding a 5-HT3 antagonist: Ondansetron 4-8 mg every 8-12 hours or granisetron 1-2 mg daily 8
• Adding corticosteroids: Dexamethasone 4-8 mg daily to potentiate antiemetic effect 4, 8
• Adding benzodiazepine for anxiety component: Lorazepam 0.5-1 mg IV/PO every 4-6 hours 5, 8

For truly refractory cases:

• Olanzapine 2.5-5 mg PO daily for persistent vomiting, especially effective in bowel obstruction 4, 8
• Cannabinoids: Dronabinol 2.5-7.5 mg every 4 hours as last resort 4, 8
• Haloperidol 0.5-2 mg IV with monitoring for QT prolongation 5

Important Medication Caveats

• Start with reduced doses in elderly or debilitated patients (e.g., olanzapine 2.5 mg, not 5 mg) 8
• Monitor for extrapyramidal symptoms with metoclopramide and prochlorperazine; have diphenhydramine 50 mg available for dystonic reactions 8
• Avoid metoclopramide in suspected bowel obstruction 4
• Use fixed scheduling for persistent symptoms, not as-needed dosing 8

Fluid and Electrolyte Management

For Mild Dehydration or Tolerating Oral Intake

Oral rehydration with small, frequent sips of electrolyte-rich fluids (sports drinks) is preferred. 5

For Moderate-Severe Dehydration or Unable to Tolerate Oral Intake

Initiate IV fluid therapy with balanced crystalloid solutions (lactated Ringer's preferred over normal saline to avoid hyperchloremic acidosis), starting with 500-1000 mL bolus followed by maintenance rate. 5

• Add dextrose-containing fluids if prolonged fasting, concern for hypoglycemia, or cyclic vomiting syndrome 5

Special Clinical Scenarios

Opioid-Induced Nausea/Vomiting

• Prophylactic antiemetics highly recommended if prior history of opioid-induced nausea 4
• First assess and treat constipation, as this is often the underlying cause 4
• Use phenothiazines (prochlorperazine) or dopamine antagonists (metoclopramide, haloperidol) as first-line 4
• Add 5-HT3 antagonists (ondansetron, granisetron) if nausea persists, as they have lower CNS side effects 4
• Consider opioid rotation if nausea persists beyond one week despite treatment 4

Chemotherapy-Induced Nausea/Vomiting

• Combine 5-HT3 antagonist + corticosteroid for moderate-high emetogenic chemotherapy 4
• Add aprepitant (neurokinin-1 antagonist) 125 mg day 1, then 80 mg days 2-3 for highly emetogenic regimens 4
• For delayed emesis: Continue corticosteroids twice daily for several days after chemotherapy 4

Cyclic Vomiting Syndrome

Use an abortive cocktail of sumatriptan (nasal spray or subcutaneous) + ondansetron + benzodiazepine, with sedation using promethazine or lorazepam in a quiet, dark environment. 5

• IV dextrose-containing fluids are essential in this population 5

Anticipatory Nausea/Vomiting

Lorazepam or similar benzodiazepines combined with behavioral techniques are most effective. 4

Reassessment and Follow-Up

• Reevaluate within 24-48 hours after initiating treatment to assess symptom control 8
• If nausea persists beyond one week, reassess for underlying causes including CNS pathology, hypercalcemia, bowel obstruction, or medication effects 4
• Before next chemotherapy cycle (if applicable), modify antiemetic regimen that failed to provide adequate protection 8