What is the best course of action for an adult patient with no known medical history presenting with nausea, vomiting, and shortness of breath (SOB)?

Immediate Cardiac Evaluation is Mandatory

For any adult presenting with nausea, vomiting, and shortness of breath, you must obtain an ECG immediately to exclude acute coronary syndrome before considering any other diagnosis. This symptom triad represents a potentially atypical presentation of myocardial ischemia, particularly in women who more frequently experience nausea, vomiting, and left-sided pain (neck/jaw/ear) compared to men 1, 2.

Critical Initial Assessment

Rule Out Life-Threatening Causes First

• Cardiac ischemia: Obtain ECG within minutes of presentation, as nausea and vomiting frequently accompany acute coronary syndrome 1, 2
• Pulmonary embolism: Consider in patients with SOB, especially with risk factors (immobility, malignancy, recent surgery) 3
• Esophageal perforation/aortic dissection: Evaluate if severe chest pain, dysphagia, or hemodynamic instability present 1, 2
• Bowel obstruction: Assess for abdominal distension, absent bowel sounds, and peritoneal signs requiring urgent surgical evaluation 4, 2
• Increased intracranial pressure: Look for headache, altered mental status, or focal neurologic deficits 2, 3

Assess for Sepsis and Hemodynamic Stability

• Begin rapid IV fluid resuscitation immediately if hypotension, tachycardia, or signs of volume depletion are present 4
• For patients with septic shock, resuscitation should begin the moment hypotension is identified 4
• Even without overt shock, IV fluids should start once intra-abdominal infection is suspected, as volume depletion is common with nausea/vomiting 4

Diagnostic Workup After Excluding Emergencies

Essential Laboratory Testing

• Basic metabolic panel: Check for electrolyte abnormalities, uremia, acidosis 3, 5
• Complete blood count: Evaluate for infection or anemia 5
• Pregnancy test: Mandatory in all women of childbearing age 3, 6, 5
• Liver function tests and lipase: If abdominal pain present 5
• Thyroid-stimulating hormone: Consider if chronic symptoms 5

Imaging Studies

• CT scan is the imaging modality of choice for determining presence of intra-abdominal infection or obstruction in patients not requiring immediate laparotomy 4
• Chest X-ray or CT chest: Essential given SOB to evaluate for pneumonia, pleural effusion, or pulmonary pathology 3
• CT head: If altered mental status, severe headache, or neurologic deficits present 2, 5

Pharmacologic Management Algorithm

First-Line Antiemetic Therapy

Initiate dopamine receptor antagonists as first-line treatment once cardiac causes are excluded:

• Metoclopramide 10-20 mg IV/IM has the strongest evidence for non-chemotherapy-related nausea and vomiting 1, 7
• Alternative: Prochlorperazine 5-10 mg IV/IM or Haloperidol 0.5-2 mg IV/IM 1, 7
• Do not use ondansetron as monotherapy—dopamine antagonists have superior evidence as first-line agents for non-chemotherapy causes 1

Second-Line Therapy (If No Response Within 1-2 Hours)

• Add dexamethasone 2-8 mg IV/PO to the antiemetic regimen 1, 7
• Olanzapine 2.5-5 mg PO/sublingual is highly effective for breakthrough nausea, particularly if first-line agents fail 1, 7
• Lorazepam 0.5-2 mg can be added if anxiety component or vestibular symptoms present 1, 7

Third-Line Options for Refractory Symptoms

• NK1 receptor antagonist (aprepitant) works through different pathway than other agents 7
• Scopolamine transdermal patch for vestibular-mediated symptoms 1, 7
• Cannabinoids (dronabinol or nabilone) for persistent symptoms despite other therapies 4, 7

Antimicrobial Therapy Considerations

If intra-abdominal infection is suspected or diagnosed, antimicrobial therapy should be initiated immediately:

• For patients with septic shock, antibiotics must be administered as soon as possible 4
• For patients without septic shock, antimicrobials should start in the emergency department within 8 hours 4
• Maintain satisfactory drug levels during any source control intervention 4

Special Clinical Scenarios

Suspected Gastroparesis or Gastric Outlet Obstruction

• Metoclopramide 10-20 mg every 6 hours provides both antiemetic and prokinetic effects 4, 7
• Do not use prokinetic agents if bowel obstruction is suspected 7
• If known malignancy with early satiety or postprandial vomiting, perform endoscopic or fluoroscopic evaluation 1, 2

Opioid-Induced Symptoms

• Consider opioid rotation if patient is on chronic opioids and nausea persists 4, 7
• Treat with dopamine antagonists plus consider reducing opioid requirement with non-nauseating coanalgesics 4

Medication-Related Causes

• Review and discontinue any unnecessary medications that may cause nausea (NSAIDs, antibiotics, SSRIs, chemotherapy agents) 4, 2
• Check available blood levels of necessary medications (digoxin, phenytoin, carbamazepine) 4

Critical Pitfalls to Avoid

• Never assume benign gastroenteritis without obtaining an ECG in patients with nausea, vomiting, and SOB—this combination warrants cardiac evaluation 1, 2
• Do not delay surgical consultation if peritoneal signs, severe abdominal pain, or imaging suggests obstruction or perforation 4, 2
• Avoid using metoclopramide if bowel obstruction is suspected, as prokinetic effects can worsen obstruction 7
• Monitor for akathisia with prochlorperazine or metoclopramide—can develop any time within 48 hours and requires treatment with diphenhydramine 8
• Do not dismiss symptoms as simple viral illness without considering metabolic causes (hypercalcemia, uremia, adrenal insufficiency, thyroid disorders) 2, 3

Disposition and Follow-Up

• Hospitalize patients with suspected surgical causes, severe dehydration, metabolic abnormalities, sepsis, or inability to tolerate oral intake 2, 6
• Urgent intervention (within 24 hours) is appropriate for hemodynamically stable patients with suspected intra-abdominal pathology if antimicrobials are started and close monitoring provided 4
• Outpatient management is acceptable only after life-threatening causes excluded, adequate hydration achieved, and symptoms controlled with antiemetics 3, 6