Laboratory Tests and Treatments for Patients Presenting with Vomiting

Initial Laboratory Evaluation

The American Gastroenterological Association recommends a basic workup for patients presenting with vomiting, including complete blood count, serum electrolytes and glucose, liver function testing, lipase, and urinalysis, followed by appropriate antiemetic therapy based on severity and suspected etiology 1, 2
Complete blood count (CBC) is used to assess for infection, inflammation, or blood loss in patients with vomiting 1
Serum electrolytes and glucose are evaluated to assess for metabolic derangements and dehydration in patients with vomiting 1
Liver function tests are used to rule out hepatic causes of vomiting 1, 2
Serum lipase is used to assess for pancreatitis in patients with vomiting 1
Urinalysis is used to evaluate hydration status and rule out urinary causes of vomiting 1

One-time esophagogastroduodenoscopy or upper gastrointestinal imaging is recommended to exclude obstructive lesions in cases of persistent vomiting 1
Abdominal CT scan is recommended for suspected bowel obstruction or perforation, with higher sensitivity than ultrasound or X-ray 3, 4
Water-soluble contrast enema is recommended for suspected large bowel obstruction, with 96% sensitivity and 98% specificity 3
ECG baseline is recommended in patients receiving certain antiemetics, such as ondansetron, due to risk of QTc prolongation 1, 2
Brain imaging and neurological referral are recommended for patients with localizing neurologic symptoms 1

For prolonged vomiting, the American Gastroenterological Association recommends assessing for thiamine deficiency and considering thiamine supplementation (200-300 mg daily) 5
For suspected cyclic vomiting syndrome (CVS), the American Gastroenterological Association recommends considering cannabis use patterns, as prolonged use (>1 year) may indicate cannabinoid hyperemesis syndrome 1, 2
For vomiting with abdominal pain, the American Gastroenterological Association recommends considering workup for Addison's disease, hypothyroidism, and hepatic porphyria 1
For vomiting in post-surgical patients, the American Society of Anesthesiologists recommends assessing for postoperative complications and considering prophylactic antiemetics 6

The American Gastroenterological Association recommends ondansetron (5-HT3 receptor antagonist) as a first-line antiemetic, 8 mg sublingual/oral every 4-6 hours during episode 1, 2
The American Gastroenterological Association recommends promethazine (dopamine receptor antagonist with antihistaminergic effects) as a first-line antiemetic, 12.5-25 mg oral/rectal every 4-6 hours 1, 2
The American Gastroenterological Association recommends prochlorperazine (dopamine receptor antagonist) as a first-line antiemetic, 5-10 mg every 6-8 hours or 25 mg suppository every 12 hours 1, 2
The American Society of Anesthesiologists recommends haloperidol or droperidol for severe, refractory cases of nausea and vomiting 6
The American Society of Clinical Oncology recommends dexamethasone for chemotherapy-induced nausea and vomiting 8

The World Journal of Emergency Surgery recommends intravenous crystalloids for dehydration and electrolyte replacement in patients with vomiting 3, 4
The World Journal of Emergency Surgery recommends nasogastric suction for gastric decompression in cases of bowel obstruction or severe vomiting 3
The American Society of Anesthesiologists recommends monitoring urine output to assess hydration status in patients with vomiting 6

For acute gastroenteritis/food poisoning, the American Gastroenterological Association recommends fluid replacement and antiemetics (ondansetron preferred) 1
For medication-induced vomiting, the National Comprehensive Cancer Network recommends considering medication adjustment or rotation and symptomatic treatment with antiemetics 7
For cyclic vomiting syndrome, the American Gastroenterological Association recommends combination therapy with sumatriptan and antiemetics 9
For bowel obstruction, the World Journal of Emergency Surgery recommends nasogastric decompression, IV fluids, and surgical consultation 3, 4
For chemotherapy-induced nausea and vomiting, the American Society of Clinical Oncology recommends prophylactic antiemetics based on emetogenic potential of chemotherapy and 5-HT3 antagonists (ondansetron) plus dexamethasone for moderate to highly emetogenic regimens 8