What are the likely causes and acute management of dizziness and syncope in a patient with influenza infection?

Dizziness and Syncope with Influenza: Causes and Acute Management

Direct Answer

In patients with influenza presenting with dizziness and syncope, immediately assess for cardiac complications (myocarditis, arrhythmia, heart failure) and neurological complications, obtain an ECG and troponin, check for orthostatic hypotension and volume depletion, and initiate oseltamivir 75 mg twice daily regardless of symptom duration if cardiac involvement is suspected. 1, 2

Likely Causes of Dizziness and Syncope in Influenza

Cardiac Complications (Most Critical)

• Cardiac involvement is a recognized complication requiring immediate evaluation, including exacerbation of pre-existing cardiac disease with heart failure and/or arrhythmia, and primary myocarditis. 1
• Severe cardiac dysfunction can be the leading clinical symptom of influenza A(H1N1) infection, presenting as acute heart failure, cardiogenic shock, or even cardiac arrest due to ventricular fibrillation. 3
• Syncope occurs in approximately 2.2% of influenza patients, with patients experiencing frequent dizziness before syncope, and longer duration of loss of consciousness observed in those with high fever or positive orthostatic blood pressure drop. 4

Volume Depletion and Orthostatic Hypotension

• Orthostatic blood pressure changes are a key mechanism, as patients with positive orthostatic BP drop experience more prolonged loss of consciousness during influenza-associated syncope. 4
• Volume depletion should be assessed in all influenza patients with dizziness or syncope, even in the absence of severe cough, low blood pressure, or obvious dehydration. 1, 4

Neurological Complications

• Neurological complications are recognized causes of admission and can manifest as altered consciousness, encephalopathy, or other central nervous system involvement. 1
• Meningococcal disease risk increases following influenza infection, which must be considered when altered level of consciousness or irritability is present. 5

Acute Management Algorithm

Immediate Assessment (First 15 Minutes)

• Obtain vital signs including orthostatic blood pressure measurements to identify postural hypotension as a contributor to syncope. 4
• Perform ECG immediately to assess for ST-segment changes, Q waves, low-voltage QRS complexes with electrical alternans, or conduction abnormalities like complete left bundle branch block. 2
• Check oxygen saturation by pulse oximetry while breathing room air; those with SaO2 < 92% require arterial blood gas measurements. 1

Laboratory Investigations

• Check troponin levels in addition to CPK-MB to confirm myocardial injury in patients with suspected cardiac involvement. 2
• Obtain full blood count, urea, creatinine, electrolytes, and liver function tests as part of the initial assessment. 2
• Consider blood cultures if severe illness is present or bacterial superinfection is suspected. 1

Imaging Studies

• Obtain chest radiograph in all influenza patients admitted with abnormal cardiorespiratory symptoms and signs. 1

Immediate Therapeutic Interventions

• Initiate oseltamivir 75 mg orally twice daily for 5 days immediately when cardiac complications are present, regardless of symptom duration. 2
• Adjust oseltamivir dose to 75 mg once daily if creatinine clearance is less than 30 mL/min. 2
• Assess for volume depletion and provide intravenous fluids as clinically indicated to address orthostatic hypotension and maintain hemodynamic stability. 1, 2
• Provide oxygen therapy if hypoxic, targeting PaO2 > 8 kPa and SaO2 ≥ 92%. 1, 2
• Use high concentration oxygen (35% or greater) unless complicated by severe COPD with ventilatory failure. 1

Ongoing Monitoring

• Monitor vital signs at least twice daily in influenza patients with cardiac involvement or syncope. 2
• Continuous oxygen therapy is indicated for patients with PaO2 < 8 kPa, hypotension with systolic blood pressure < 100 mmHg, metabolic acidosis with bicarbonate < 18 mmol/L, or respiratory distress with respiratory rate > 30/min. 1

Transfer to ICU/HDU Criteria

• Transfer to intensive care should be considered for patients with cardiogenic shock or persistent hypotension, severe cardiac dysfunction on echocardiography with clinical decompensation, or CURB-65 score of 4 or 5 if concurrent pneumonia is present. 2

Critical Pitfalls to Avoid

Do Not Assume Benign Vasovagal Syncope

• Syncope in influenza patients can indicate serious cardiac complications including myocarditis and arrhythmias, not just simple vasovagal episodes. 3
• None of the patients with influenza-associated syncope had severe cough or obvious dehydration, making it easy to miss the diagnosis if not specifically evaluated. 4

Do Not Delay Antiviral Therapy

• Oseltamivir should be initiated immediately when cardiac complications are suspected, regardless of the 48-hour window typically recommended for uncomplicated influenza. 2

Do Not Miss Bacterial Superinfection

• Fever persisting beyond 4 days or worsening after initial improvement strongly suggests bacterial superinfection, particularly pneumonia. 5
• Secondary bacterial pneumonia occurs in 20-38% of severe influenza cases requiring intensive care. 5

Do Not Overlook Meningococcal Disease

• The risk of invasive meningococcal disease rises after influenza infection, and altered consciousness should prompt consideration of this diagnosis. 5