What are the initial steps for managing a patient with chronic vomiting for approximately 1 year?

Initial Management of Chronic Vomiting (1 Year Duration)

Begin with a basic diagnostic workup including complete blood count, serum electrolytes and glucose, liver function tests, lipase, and urinalysis, followed by one-time esophagogastroduodenoscopy to exclude obstructive lesions, then initiate prophylactic therapy with amitriptyline 25 mg at bedtime (titrating to 75-150 mg) while screening for cannabis use to differentiate cyclic vomiting syndrome from cannabinoid hyperemesis syndrome. 1

Immediate Diagnostic Priorities

Essential Laboratory Testing

• Obtain complete blood count, serum electrolytes (particularly potassium and magnesium), glucose, liver function tests, lipase, and urinalysis to identify metabolic causes, dehydration, and electrolyte abnormalities that perpetuate the vomiting cycle 1, 2
• Prolonged vomiting causes hypokalemia, hypochloremia, and metabolic alkalosis that must be corrected 2
• Check for hypercalcemia, hypothyroidism, and adrenal insufficiency if clinically indicated 2

Critical Cannabis Screening

• Screen all patients for cannabis use patterns before proceeding with diagnosis, as use >4 times weekly for >1 year suggests cannabinoid hyperemesis syndrome (CHS) rather than cyclic vomiting syndrome (CVS) 1, 3
• CHS requires 6 months of cannabis cessation (or at least 3 typical cycle lengths) to retrospectively diagnose 1
• Hot water bathing is not pathognomonic for CHS, as it occurs in 48% of CVS patients who don't use cannabis 4
• Patients with ongoing cannabis use should still be offered prophylactic and abortive therapy, as these can be effective even with continued use 1

Structural Evaluation

• Perform one-time esophagogastroduodenoscopy or upper gastrointestinal imaging to exclude obstructive lesions, peptic ulcer disease, or malignancy 1, 2
• If performed soon after a vomiting episode, recognize epiphenomena (mild gastritis, erythematous streaking, Mallory-Weiss tear, esophagitis) as not being causal 1
• Avoid repeated endoscopy or imaging studies unless new symptoms develop 1, 2

Determining the Pattern: CVS vs Other Causes

Cyclic Vomiting Syndrome Diagnostic Features

CVS should be strongly suspected if the patient has: 1, 3

• Stereotypical episodes of acute-onset vomiting lasting <7 days
• At least 3 discrete episodes in the past year, with 2 occurring in the prior 6 months
• Episodes separated by at least 1 week of baseline health (though milder symptoms like nausea may persist)

Key Clinical Clues Supporting CVS

• Approximately 65% of CVS patients experience prodromal symptoms (median 1 hour duration) including impending sense of doom, panic, fatigue, mental fog, restlessness, anxiety, headache, bowel urgency, diaphoresis, or flushing 1, 3
• Each patient has a stereotypical cluster of symptoms that occur in the same order with each episode 1
• Most episodes occur in early morning hours 1
• Abdominal pain is present in most patients during episodes and should not preclude diagnosis 1
• Personal or family history of migraine headaches supports the diagnosis (present in 20-30% of patients) 3

Common Triggers to Identify

• Stress (psychological or physiological) triggers episodes in 70-80% of patients, including both negative stress (death, conflicts) and positive events (birthdays, vacations) 1
• Sleep deprivation, hormonal fluctuations during menstrual cycle, travel, motion sickness, acute infections, surgery, prolonged fasting, or intense exercise 1

Initial Therapeutic Approach

Prophylactic Therapy (First-Line)

For patients with moderate-severe CVS (≥4 episodes/year lasting >2 days with ED visits or hospitalizations), initiate amitriptyline as first-line prophylactic therapy: 1, 3

• Start 25 mg at bedtime
• Titrate weekly to goal dose of 75-150 mg nightly (1-1.5 mg/kg)
• Response rate is 67-75% 3
• Obtain baseline ECG due to QTc prolongation risk 3

Alternative Prophylactic Options (Second-Line)

If amitriptyline is not tolerated or effective: 3

• Topiramate: Start 25 mg daily, titrate to 100-150 mg daily in divided doses (monitor electrolytes and renal function twice yearly)
• Levetiracetam: Start 500 mg twice daily, titrate to 1000-2000 mg daily in divided doses (monitor CBC)
• Zonisamide: Start 100 mg daily, titrate to 200-400 mg daily (monitor electrolytes and renal function twice yearly)

Abortive Therapy Education

Educate patients to recognize their prodromal symptoms and take abortive medications immediately, as the probability of successfully aborting an episode is highest during the prodrome: 1, 3

• Sumatriptan 20 mg intranasal spray (can repeat once after 2 hours, maximum 2 doses per 24 hours)
• Ondansetron 8 mg sublingual every 4-6 hours 3, 5
• Patients must be "rehearsed" on this action plan 1

Acute Episode Management (If Presenting During Emetic Phase)

• Aggressive IV fluid replacement with dextrose-containing fluids for rehydration and metabolic support 3
• Correct electrolyte abnormalities, particularly hypokalemia and hypomagnesemia 2, 5
• Ondansetron 8 mg IV every 4-6 hours as first-line antiemetic 3, 5
• IV ketorolac as first-line non-narcotic analgesia for severe abdominal pain 3
• Avoid opioids due to worsening nausea and high addiction risk 1
• For refractory cases: droperidol or haloperidol, with benzodiazepines for sedation in quiet, dark room 3

Additional Diagnostic Considerations

When to Consider Gastroparesis

• Perform gastric emptying scintigraphy (2-4 hour study) if gastroparesis is suspected 2, 4
• Do not order gastric emptying scans routinely in CVS, as few patients have delayed emptying and results during an episode are uninterpretable 1
• Cannabis or opiate use complicates interpretation 1

Other Conditions to Exclude

Based on individual patient history, consider workup for: 1

• Addison's disease
• Hypothyroidism
• Hepatic porphyria (can mimic CVS)
• Brain imaging and neurology referral for any localizing neurologic symptoms 1

Essential Lifestyle Modifications and Comorbidity Management

Mandatory Lifestyle Interventions

All patients require: 1, 3

• Regular sleep schedule (avoid sleep deprivation)
• Avoid prolonged fasting
• Stress management techniques (cognitive behavioral therapy, mindfulness meditation)
• Identify and mitigate individual triggers

Psychiatric Comorbidity Screening

• Screen for anxiety, depression, and panic disorder, as these are present in 50-60% of CVS patients 3
• Treating underlying anxiety can decrease CVS episode frequency 3
• Refer to psychiatrist, psychologist, or counselor as needed 1

Allied Health Referrals

Consider referrals to: 1

• Neurologist (for migraine management)
• Sleep specialist (for sleep disorders)
• Substance use specialist (if cannabis or other substance use present)

Critical Pitfalls to Avoid

• Never use antiemetics if mechanical bowel obstruction is suspected (bilious vomiting requires urgent fluoroscopy upper GI series and surgical consultation) 2, 4
• Do not perform repeated endoscopy or imaging unless new symptoms develop 1, 2
• Monitor for QTc prolongation with ondansetron, especially in patients with electrolyte abnormalities (hypokalemia, hypomagnesemia), congestive heart failure, or bradyarrhythmias 5
• Monitor for extrapyramidal symptoms with dopamine antagonists (metoclopramide, prochlorperazine, haloperidol), particularly in young patients 2
• Provide thiamin supplementation to prevent Wernicke's encephalopathy in patients with persistent vomiting 2
• Do not stigmatize patients using cannabis—offer treatment regardless of ongoing use while encouraging cessation 1
• Missing the prodromal window dramatically reduces abortive therapy effectiveness—patient education is imperative 1, 3