What is the best course of action for a 16-year-old female with a past medical history (PMH) of Postural Orthostatic Tachycardia Syndrome (POTS) who presents to the Emergency Department (ED) with weakness, fatigue, and an episode of nausea, dizziness, and lightheadedness after receiving intravenous (IV) fluids with vitamins at a high rate?

Management of Infusion Reaction in POTS Patient

Stop the IV infusion immediately, switch to normal saline at keep-vein-open (KVO) rate, and monitor for 15 minutes—this patient is experiencing a mild infusion reaction likely triggered by rapid fluid administration in the setting of POTS. 1

Immediate Actions

Stop the current infusion and maintain IV access:

• Discontinue the vitamin-containing IV fluid immediately 1
• Switch the IV line to normal saline at KVO rate to maintain venous access 1
• Monitor vital signs closely including blood pressure, pulse, respiratory rate, oxygen saturation, and temperature until stable 1

Classify the reaction severity:

• This presentation (nausea, dizziness, lightheadedness without hypotension, urticaria, or respiratory symptoms) represents a mild infusion reaction 1
• Mild reactions include pruritus, flushing, urticaria, chest tightness, back pain, and joint pain without hypotension or respiratory compromise 1

Symptom Management

Treat nausea specifically:

• Administer ondansetron 4-8 mg IV for nausea 1
• Avoid first-generation antihistamines (diphenhydramine) as they can exacerbate hypotension, tachycardia, and worsen symptoms in POTS patients 1

Monitor for 15 minutes:

• Most mild infusion reactions are self-limiting and resolve spontaneously 1
• Continue monitoring until complete resolution of symptoms 1
• If symptoms do not improve or worsen after 15 minutes, consider IV hydrocortisone 100-200 mg 1

POTS-Specific Considerations

Recognize the underlying pathophysiology:

• POTS patients have hypovolemia, peripheral denervation, and impaired orthostatic tolerance as core features 2, 3
• Rapid IV fluid administration can trigger symptoms through complement activation-related pseudoallergy (CARPA) or volume shifts 1
• The high infusion rate likely precipitated symptoms in a patient already predisposed to autonomic instability 2, 4

Adjust fluid administration strategy:

• Once symptoms resolve after 15 minutes, consider restarting IV fluids at 50% of the initial infusion rate 1
• Use isotonic crystalloid (normal saline or lactated Ringer's) without additives 5
• Increase rate slowly after 15 minutes if well tolerated 1
• Stop immediately if symptoms recur 1

Ongoing Management in ED

Optimize volume status carefully:

• POTS patients benefit from volume expansion, but administration must be gradual 5, 2, 3
• Target adequate hydration with isotonic fluids administered at slower rates 5
• Monitor for signs of fluid overload (though rare in young POTS patients): increased jugular venous pressure, pulmonary crackles 1

Address the presenting symptoms:

• Weakness and fatigue in POTS are often related to hypovolemia and deconditioning 2, 3, 4
• Once acute symptoms resolve, continue IV hydration at appropriate rate to address underlying volume depletion 5
• Assess for orthostatic vital signs once patient is stable 2, 4

Critical Pitfalls to Avoid

Do not use vasopressors or first-generation antihistamines:

• These medications can convert minor reactions into hemodynamically significant events 1
• First-generation antihistamines cause hypotension, tachycardia, diaphoresis, sedation, and potential shock 1
• Even second-generation antihistamines can cause flushing, palpitations, and dizziness 1

Do not restart fluids at the same rapid rate:

• The initial high infusion rate likely triggered this reaction 1
• Rechallenge must be at 50% of initial rate with gradual titration 1

Do not assume this is anaphylaxis:

• True anaphylaxis requires sudden onset, rapid intensification, hypotension (SBP drop ≥30 mmHg or SBP ≤90 mmHg), angioedema, or multi-organ involvement 1
• This patient's presentation is consistent with mild infusion reaction, not anaphylaxis 1

Disposition Planning

Educate the patient before discharge:

• Inform about possible delayed reactions (flu-like symptoms, arthralgias, myalgias, fever) that can occur hours to days after infusion 1
• These delayed symptoms last up to 24 hours and are managed with NSAIDs 1
• Symptoms lasting more than a few days require provider evaluation 1

Provide POTS-specific recommendations:

• Emphasize high salt intake (5-10 g/day) and fluid loading (3 liters daily) for ongoing management 1, 2, 3
• Recommend compression stockings (waist-high) and elevation of head of bed 4-6 inches 1
• Avoid dehydration triggers: alcohol, caffeine, large meals, excessive heat 1