How should I manage a previously healthy 19-year-old male with six hours of persistent nausea and vomiting and leukocytosis with neutrophil predominance?

Management of Acute Nausea and Vomiting with Leukocytosis in a 19-Year-Old Male

This previously healthy 19-year-old male with 6 hours of nausea/vomiting and leukocytosis (WBC 16.4, neutrophils 15.09) most likely has acute gastroenteritis or another self-limited viral syndrome and should receive symptomatic antiemetic therapy with ondansetron 8 mg IV plus fluid resuscitation, while ruling out surgical emergencies and metabolic causes. 1, 2

Initial Diagnostic Workup

Obtain immediate laboratory studies to exclude metabolic emergencies and assess hydration status:

• Complete metabolic panel (electrolytes, glucose, renal function) to identify hypokalemia, hypochloremia, metabolic alkalosis, or hypercalcemia 1
• Liver function tests and lipase to exclude hepatobiliary or pancreatic pathology 1
• Urinalysis and urine drug screen (specifically asking about cannabis use given age and presentation) 1
• Pregnancy test if applicable 2, 3

The leukocytosis pattern here (WBC 16.4 with neutrophil predominance) is consistent with acute infection or inflammation rather than paraneoplastic leukemoid reaction, which typically occurs with WBC >40,000 and metastatic solid tumors. 4

Critical Red Flags to Exclude Immediately

Perform focused abdominal examination looking specifically for:

• Peritoneal signs (rebound, guarding, rigidity) suggesting acute abdomen requiring surgical consultation 3, 5
• Right lower quadrant tenderness with fever suggesting appendicitis 2
• Severe dehydration (dry mucous membranes, tachycardia, orthostatic hypotension) requiring IV fluid resuscitation 1

Do not administer antiemetics if mechanical bowel obstruction is suspected, as this masks progressive ileus and gastric distension. 1, 6 If obstruction is a concern, obtain upright abdominal radiographs before antiemetic administration. 5

Immediate Pharmacologic Management

Administer ondansetron 8-16 mg IV as first-line antiemetic for acute nausea and vomiting in this setting. 1, 6 The FDA-approved ondansetron dosing is 0.15 mg/kg per dose (maximum 16 mg), infused over 15 minutes. 6

If ondansetron alone is insufficient, add metoclopramide 10 mg IV as it acts on different dopamine receptors and provides complementary antiemetic coverage. 1, 7 Metoclopramide is particularly effective for gastric stasis. 1

Monitor for extrapyramidal symptoms with metoclopramide, especially in young males who are at higher risk. 1 Treat with diphenhydramine 50 mg IV if dystonic reactions develop. 1

Fluid and Electrolyte Management

Administer isotonic IV fluids (lactated Ringer's or normal saline) if the patient shows signs of moderate-to-severe dehydration, cannot tolerate oral intake, or has significant electrolyte abnormalities. 1

Correct hypokalemia and hypomagnesemia aggressively, as prolonged vomiting causes these deficiencies which perpetuate nausea. 1 The American College of Physicians rates this recommendation as high-strength evidence. 1

If ketonemia is present, initial IV hydration may be necessary before transitioning to oral rehydration. 1

Cannabis Hyperemesis Syndrome Consideration

Obtain detailed cannabis use history, as Cannabis Hyperemesis Syndrome (CHS) is increasingly common in this age group and presents with cyclic vomiting. 1 CHS patients often report compulsive hot bathing for symptom relief. 1

Do not stigmatize patients with cannabis use—offer abortive therapy even with ongoing use, as antiemetics can still provide benefit. 1 Definitive diagnosis requires 6 months of cannabis cessation. 1

Disposition and Follow-Up

Most cases of acute gastroenteritis are self-limited and resolve within 24-48 hours with supportive care. 2, 3 Discharge home is appropriate if:

• Hemodynamically stable after IV fluids
• Tolerating oral intake
• No surgical abdomen
• No severe metabolic derangements
• Reliable follow-up available 2

Prescribe ondansetron 8 mg PO every 8 hours as needed for outpatient symptom control. 6 Advise small, frequent meals and avoidance of trigger foods. 2

Arrange follow-up within 48-72 hours if symptoms persist beyond expected timeframe for viral gastroenteritis. 2 If vomiting continues beyond 7 days, this transitions to chronic nausea/vomiting requiring broader differential consideration including gastroparesis, peptic ulcer disease, or functional disorders. 2, 3

Common Pitfalls

Avoid repeated imaging or endoscopy unless new symptoms develop or the clinical picture changes. 1 One-time upper GI imaging or EGD is sufficient to exclude obstruction if clinically indicated. 1

Do not use antimotility agents (loperamide) if inflammatory diarrhea or fever is present, as this can worsen outcomes in infectious colitis. 1

Monitor QTc interval if using ondansetron, especially if combining with other QT-prolonging medications, as dose-dependent QT prolongation and rare cases of Torsade de Pointes have been reported. 6