What is the appropriate management for a 16-year-old patient with acute onset of nausea, vomiting, generalized weakness, dyspnea, and abdominal cramping, and no significant past medical or surgical history?

Management of a 16-Year-Old with Acute Nausea, Vomiting, Weakness, Dyspnea, and Abdominal Cramping

This patient requires immediate evaluation for life-threatening metabolic emergencies, particularly diabetic ketoacidosis (DKA), and potential surgical causes before initiating symptomatic antiemetic therapy.

Immediate Diagnostic Priorities

Critical Laboratory Testing

• Obtain stat comprehensive metabolic panel, complete blood count, venous or arterial blood gas, serum glucose, lipase, and urinalysis to identify metabolic acidosis, electrolyte abnormalities (particularly hypokalemia and hypochloremia from vomiting), hyperglycemia, and ketonemia 1, 2, 3.
• Check serum lactate and liver function tests to assess for tissue hypoperfusion and hepatic involvement 4, 2.
• The combination of dyspnea with nausea/vomiting and weakness in an adolescent strongly suggests metabolic acidosis with compensatory hyperventilation, most commonly from DKA in this age group 3, 5.

Imaging Considerations

• Obtain upright abdominal radiography or CT abdomen/pelvis if peritoneal signs are present to exclude bowel obstruction, perforation, or appendicitis 4, 2.
• Abdominal cramping with vomiting warrants evaluation for surgical causes, though the absence of localized tenderness makes obstruction less likely 4.
• Do not delay imaging if there are signs of acute abdomen (rebound tenderness, guarding, absent bowel sounds) 4, 2.

Initial Stabilization

Fluid Resuscitation

• Administer isotonic intravenous fluids (lactated Ringer's or normal saline) immediately for presumed severe dehydration given the constellation of weakness, vomiting, and dyspnea 1.
• In patients with ketonemia (suspected DKA), intravenous hydration is essential before oral intake can be tolerated 1.
• Correct electrolyte abnormalities, particularly hypokalemia and hypomagnesemia, which commonly result from prolonged vomiting 1.

Antiemetic Therapy Algorithm

Step 1: First-Line Dopamine Antagonist

• Initiate metoclopramide 10 mg IV every 6 hours as first-line therapy, which is particularly effective for gastric stasis and has high-quality evidence supporting its use 6, 7.
• Alternative first-line options include prochlorperazine 10 mg IV every 6-8 hours or haloperidol 0.5-1 mg IV every 4-6 hours 6, 7.
• Administer antiemetics on a scheduled basis rather than PRN, as prevention is easier than treating established vomiting 7.
• Monitor closely for extrapyramidal symptoms (akathisia, dystonia), particularly in young males, and treat with diphenhydramine 50 mg IV if they develop 1, 7, 8.

Step 2: Add 5-HT3 Antagonist if Symptoms Persist

• Add ondansetron 4-8 mg IV 2-3 times daily rather than replacing the dopamine antagonist, as this targets different receptor pathways for synergistic effect 6, 7.
• Monitor for QTc prolongation when using ondansetron, especially if combined with other QT-prolonging agents 1, 7.
• Note that ondansetron may increase stool volume if diarrhea is present 1.

Step 3: Consider Corticosteroids for Refractory Symptoms

• Add dexamethasone 10-20 mg IV if symptoms persist despite dopamine antagonist plus ondansetron, as this combination represents category 1 evidence 7.
• The combination of ondansetron with dexamethasone is superior to either agent alone 7.

Critical Underlying Causes to Exclude

Metabolic Emergencies

• Diabetic ketoacidosis is the most likely diagnosis given age, acute onset, dyspnea (Kussmaul respirations), weakness, and GI symptoms 3, 5.
• Addison's disease should be considered if hypotension, hyponatremia, and hyperkalemia are present 4, 2.
• Hypercalcemia can present with nausea, vomiting, and weakness 1, 2.

Gastrointestinal Causes

• Small bowel obstruction must be excluded given abdominal cramping, though the acute onset and lack of prior surgery make adhesions less likely 4.
• Acute gastroenteritis is common but typically does not cause dyspnea unless severe dehydration is present 2, 9.
• Appendicitis or other surgical abdomen should be considered if localized tenderness develops 4, 2.

Toxicologic Considerations

• Cannabis hyperemesis syndrome is critical to consider in this age group and requires specific questioning about cannabis use 1.
• Medication or toxin ingestion should be evaluated with history and potentially urine drug screen 2, 3.

Critical Pitfalls to Avoid

• Never initiate antiemetics if mechanical bowel obstruction is suspected, as this can mask progressive ileus and gastric distension 1, 7.
• Do not attribute symptoms to gastroenteritis without excluding metabolic acidosis, particularly DKA in an adolescent with dyspnea 3, 5.
• Avoid repeated imaging unless new symptoms develop once obstruction is excluded 1.
• Do not delay fluid resuscitation while awaiting laboratory results in a patient with signs of severe dehydration 1.
• Monitor for extrapyramidal symptoms with dopamine antagonists, which occur more frequently in young males 1, 7, 8.

Route of Administration

• Use intravenous route initially given active vomiting and inability to tolerate oral medications 7.
• Consider rectal suppositories or sublingual formulations if IV access is difficult 7.

Supportive Care

• Ensure adequate fluid intake of at least 1.5 L/day once oral intake is tolerated 1.
• Provide thiamin supplementation to prevent Wernicke's encephalopathy if prolonged vomiting continues 1.
• Small, frequent meals should be offered once vomiting is controlled 1.