What is the initial treatment for vomiting in the Emergency Room (ER)?

Treatment of Vomiting in the Emergency Department

Ondansetron (4 mg IV over 2-5 minutes or 8 mg sublingual/oral) is the first-line antiemetic for acute vomiting in the ER, combined with immediate assessment of hydration status and intravenous fluid resuscitation with normal saline or lactated Ringer's for moderate-to-severe dehydration. 1, 2, 3

Initial Assessment and Stabilization

Assess for red flag signs immediately: bilious or bloody vomiting, altered mental status, severe dehydration (sunken eyes, decreased skin turgor, dry mucous membranes, tachycardia, hypotension), toxic appearance, or severe abdominal pain requiring urgent surgical evaluation. 4, 5

Evaluate hydration status systematically:

• Mild dehydration: Oral rehydration may be attempted with small, frequent sips of electrolyte-rich fluids 2
• Moderate-to-severe dehydration: Initiate IV fluid bolus of 500-1000 mL normal saline or lactated Ringer's, followed by maintenance rate 2
• Add dextrose-containing fluids if prolonged fasting or concern for hypoglycemia exists 2

Pharmacologic Management

First-line antiemetic therapy:

• Ondansetron 4 mg IV over 2-5 minutes (adults) or 8 mg sublingual/oral every 4-6 hours 1, 2, 3
• For pediatric patients >4 years: 0.1 mg/kg IV (maximum 4 mg) 3, 5
• Sublingual formulation may improve absorption in actively vomiting patients 2

Second-line options if ondansetron fails or is contraindicated:

• Metoclopramide 10-20 mg IV/IM (works through central and peripheral pathways) 1, 2
• Promethazine 12.5-25 mg IV/IM/rectal (more sedating but effective) 1, 2
• Prochlorperazine 10 mg IV/IM or 25 mg rectal suppository 1, 2

For refractory vomiting, consider combination therapy:

• Add benzodiazepine (lorazepam 0.5-1 mg IV or alprazolam 0.25-0.5 mg sublingual) plus haloperidol 0.5-2 mg IV 2
• Monitor for QT prolongation with ondansetron, haloperidol, and some dopamine antagonists, especially in patients with cardiac risk factors 1, 2

Special Clinical Scenarios

Cyclic vomiting syndrome (if suspected):

• Abortive cocktail: sumatriptan (nasal spray or subcutaneous) + ondansetron + benzodiazepine 2
• Sedation with promethazine or lorazepam in a quiet, dark environment 2
• IV dextrose-containing fluids are essential 2

Gastroenteritis with persistent vomiting:

• Ondansetron facilitates oral rehydration tolerance and reduces immediate hospitalization need 4, 5
• Note: Ondansetron may increase stool volume/diarrhea, but this does not outweigh vomiting control benefit 4
• Continue oral rehydration with small, frequent volumes (5 mL every minute initially) after antiemetic administration 4

Small bowel obstruction (if suspected):

• Bowel rest with nasogastric tube decompression for bilious vomiting 5, 6
• Correction of physiologic and electrolyte disturbances 6
• Urgent surgical consultation 5

Supportive Care Measures

Fluid and electrolyte management:

• Monitor and correct electrolyte abnormalities as needed 1
• Assess for thiamine deficiency and consider supplementation (200-300 mg daily) in cases of prolonged vomiting 1
• Balanced crystalloid solutions (lactated Ringer's) are preferred over 0.9% normal saline to avoid hyperchloremic acidosis 7

Dietary modifications after symptom control:

• Small, frequent meals with bland foods 1
• Avoid spicy, fatty, or trigger foods 1

Important Caveats

Avoid routine antiemetics in specific situations:

• Do not give prophylactic antiemetics in radiation exposure cases, as vomiting onset helps determine radiation dose 7
• Antiemetics like chlorpromazine should not be routinely used in gastroenteritis, as vomiting usually subsides with continued oral rehydration 8

Laboratory testing:

• Routine electrolytes, BUN, creatinine are not necessary for uncomplicated acute vomiting with mild-moderate dehydration 9
• Reserve laboratory testing for severe dehydration, red flag signs, or when specific etiologies (diabetic ketoacidosis, uremia, metabolic disorders) are suspected 5, 10

Nasogastric decompression:

• Required for bilious vomiting or suspected bowel obstruction 5, 6
• Avoid instrumentation of GI tract in radiation exposure cases due to friable mucosa 7