What to check in a patient who continues to vomit?

What to Check in a Patient Who Continues to Vomit

Immediately obtain a complete blood count, comprehensive metabolic panel (including electrolytes, glucose, liver and renal function), serum lipase, and urinalysis to assess for metabolic derangements, dehydration, infection, and organ dysfunction. 1, 2

Essential Initial Laboratory Tests

• Complete blood count (CBC) to identify infection, anemia, leukopenia, or other hematologic abnormalities that may indicate serious underlying pathology 1, 2
• Serum electrolytes and glucose are critical as persistent vomiting causes hyponatremia, hypokalemia, hypochloremia, and metabolic alkalosis; severe electrolyte disturbances can cause seizures and cardiac arrhythmias 1, 2, 3
• Liver function tests to exclude hepatic causes of vomiting and assess for medication toxicity 1, 2
• Serum lipase to rule out pancreatitis as a cause of persistent vomiting 1, 2
• Renal function tests (BUN/creatinine) to assess degree of dehydration and kidney function 2
• Urinalysis to evaluate hydration status and exclude urinary tract causes 1, 2

Critical Monitoring Parameters

• Blood gas analysis for base excess and lactate levels to evaluate acid-base status and tissue perfusion; serum bicarbonate ≤13 mEq/L predicts failure of outpatient management and need for admission 2, 4
• Hydration status assessment through physical examination (skin turgor, mucous membranes, vital signs including orthostatic changes) and urine output monitoring 5
• Monitor for electrolyte abnormalities particularly in patients with severe or prolonged vomiting; check and correct deficiencies before they cause complications 5, 3

Special Considerations Based on Clinical Context

Post-Bariatric Surgery Patients

• Thiamin supplementation (200-300 mg daily) is essential in cases of persistent vomiting to prevent Wernicke's encephalopathy 5, 1
• Monitor for dehydration with target fluid intake ≥1.5 L/day 5
• Check blood electrolytes regularly in persistent vomiting 5

Suspected Cyclic Vomiting Syndrome or Cannabinoid Hyperemesis

• Obtain detailed cannabis use history (frequency, duration, timing relative to symptom onset); prolonged use >1 year at >4 times weekly suggests cannabinoid hyperemesis syndrome rather than cyclic vomiting syndrome 5, 1
• Consider workup for Addison's disease, hypothyroidism, and hepatic porphyria which can mimic cyclic vomiting syndrome 5, 1
• Brain imaging and neurological referral if any localizing neurologic symptoms are present 5, 1

Chemotherapy-Related Vomiting

• Reassess for non-chemotherapy causes including brain metastases, electrolyte abnormalities, tumor infiltration of bowel, or other gastrointestinal abnormalities before next cycle 5
• Ensure adequate hydration and correct electrolyte abnormalities 5

Imaging Studies When Indicated

• One-time esophagogastroduodenoscopy or upper GI imaging to exclude obstructive lesions in persistent unexplained vomiting; avoid repeated studies 5, 1
• Abdominal CT scan when complications such as bowel obstruction, perforation, or abscess are suspected 1, 2
• Plain radiographs may identify radiopaque foreign bodies, obstruction, or perforation 2

Common Pitfalls to Avoid

• Do not routinely order gastric emptying scans in vomiting patients, especially those using cannabis or opiates, as results are uninterpretable during acute episodes 5
• Recognize epiphenomena of recent vomiting on endoscopy (mild gastritis, Mallory-Weiss tears, esophagitis) as effects rather than causes 5
• Do not delay treatment while awaiting test results in severely dehydrated patients; initiate IV fluid resuscitation immediately 1, 4
• Beware of rapid sodium overcorrection in hyponatremic patients once vomiting is controlled with antiemetics, as this can trigger unpredictable free water diuresis; monitor sodium closely and correct at 2-3 mmol/L daily 6
• Patients sometimes confuse heartburn with nausea; consider proton pump inhibitors or H2 blockers if dyspepsia is present 5

Treatment Considerations While Evaluating

• Ondansetron 8 mg sublingual/oral every 4-6 hours is first-line antiemetic therapy 1, 7
• Intravenous crystalloid resuscitation for dehydration and electrolyte replacement 1, 2
• Around-the-clock antiemetic dosing is superior to PRN dosing for preventing breakthrough vomiting 5
• Use rectal or IV routes when oral administration is not feasible due to ongoing vomiting 5