What is the management approach for a patient with vomiting?

Management of Vomiting in a Patient

Start with ondansetron 8 mg orally (or 4 mg IV if unable to tolerate oral) as first-line therapy, ensure adequate hydration, and assess for underlying causes requiring specific intervention. 1, 2

Immediate Assessment and Stabilization

Identify red flag signs requiring urgent intervention:

• Bilious or bloody vomiting (suggests obstruction or GI bleeding) 3
• Altered mental status or toxic appearance 3
• Severe dehydration with hemodynamic instability 3
• Abdominal distention or concern for bowel obstruction 4

Assess hydration status clinically:

• Check for dry mucous membranes, decreased skin turgor, tachycardia, and orthostatic hypotension 1
• Obtain vital signs and assess for signs of shock 3

Initial Diagnostic Workup

Order targeted laboratory tests to identify reversible causes:

• Complete blood count, serum electrolytes (particularly potassium and magnesium), glucose, liver function tests, lipase, and urinalysis 1
• Consider hypercalcemia, thyroid function, and cortisol if clinically indicated 1, 5
• Urine drug screen to assess for cannabis use, especially in younger patients 1

Obtain imaging only when clinically indicated:

• Upper GI imaging or esophagogastroduodenoscopy if obstruction suspected 1
• Avoid repeated endoscopy unless new symptoms develop 1

Fluid and Electrolyte Management

Initiate rehydration based on severity:

• For mild dehydration: oral rehydration with small, frequent sips of electrolyte-rich fluids 2
• For moderate-severe dehydration: IV normal saline or lactated Ringer's with 500-1000 mL bolus, then maintenance rate 2
• Add dextrose to IV fluids if prolonged fasting or hypoglycemia concern 2
• Correct hypokalemia and hypomagnesemia as these are common with persistent vomiting 1

Pharmacologic Management Algorithm

First-line antiemetic therapy:

• Ondansetron 8 mg orally (or 4 mg IV if actively vomiting), with sublingual formulation potentially improving absorption 2, 6
• Administer on a scheduled basis rather than PRN, as prevention is easier than treating established vomiting 4, 1

If vomiting persists after initial ondansetron dose, add dopamine antagonist:

• Metoclopramide 10 mg IV/IM (particularly effective for gastric stasis) 4, 1
• OR prochlorperazine 10 mg IV/IM or 25 mg rectal suppository 4, 2
• OR promethazine 12.5-25 mg IV/IM/rectal 2

For refractory vomiting despite combination therapy:

• Add dexamethasone 10-20 mg IV, as this combination is superior to either agent alone 1
• Consider haloperidol 0.5-2 mg IV every 4 hours as alternative dopamine antagonist with different receptor profile 1
• Add lorazepam 0.5-1 mg IV or sublingual for anxiety-related component 4, 2

Alternative routes if oral not feasible:

• Use rectal, sublingual, or IV administration when ongoing vomiting prevents oral intake 4, 1
• Multiple concurrent agents from different drug classes may be necessary, given at alternating schedules 4

Treatment of Specific Underlying Causes

For gastroparesis or gastritis:

• Continue metoclopramide as it promotes gastric emptying 4, 5
• Add proton pump inhibitor or H2 receptor antagonist 4

For metabolic abnormalities:

• Correct hypercalcemia and treat dehydration 4, 5
• Address electrolyte imbalances identified on laboratory testing 4, 1

For Cannabis Hyperemesis Syndrome (if suspected):

• Offer abortive therapy with sumatriptan (nasal spray or subcutaneous) + ondansetron + benzodiazepine 2
• Provide sedation with promethazine or lorazepam in quiet, dark environment 2
• Do not stigmatize; treatments can still be effective even with ongoing cannabis use 1, 5

For medication-induced vomiting:

• Discontinue unnecessary medications 4
• If opioid-related, consider opioid rotation or adding non-nauseating coanalgesics 4

Critical Pitfalls to Avoid

Never use antiemetics in suspected mechanical bowel obstruction:

• This can mask progressive ileus and gastric distension 4, 5
• If bilious vomiting present, stop oral intake and decompress stomach with nasogastric tube 3

Monitor for QT prolongation with ondansetron:

• Especially when combined with other QT-prolonging agents 1, 6
• Avoid in patients with congenital long QT syndrome 6

Watch for extrapyramidal symptoms with dopamine antagonists:

• Particularly in young males receiving metoclopramide, prochlorperazine, or haloperidol 1
• Treat with diphenhydramine 50 mg IV if symptoms develop 1

Consider dyspepsia mimicking nausea:

• Patients may confuse heartburn with nausea 4
• Add H2 blocker or proton pump inhibitor if dyspepsia suspected 4, 1

Refractory Cases

For persistent symptoms despite maximal therapy:

• Consider dronabinol 2.5-7.5 mg PO every 4 hours (FDA-approved cannabinoid for refractory nausea) 4, 1
• Add scopolamine transdermal patch as anticholinergic agent 4
• Consider continuous IV or subcutaneous infusion of antiemetics 4
• Reassess for non-obvious causes: brain metastases, bowel infiltration, other comorbidities 4