What is the recommended supportive management for influenza A infection?

Supportive Management for Influenza A

The cornerstone of supportive management for influenza A includes oxygen therapy targeting SaO₂ >92%, intravenous fluid resuscitation for volume depletion, cardiac monitoring, nutritional support in severe cases, and close vital sign monitoring using an Early Warning Score system.

Oxygen Therapy and Respiratory Support

• Administer oxygen therapy to maintain PaO₂ >8 kPa and SaO₂ >92% in all hypoxic patients, with high concentrations (≥35%) safely used in uncomplicated cases 1
• For patients with pre-existing COPD, initiate lower oxygen concentrations (24-28%) and titrate based on repeated arterial blood gas measurements, targeting SaO₂ >90% without dropping arterial pH below 7.35 1
• Non-invasive ventilation (NIV) may serve as a bridge to invasive ventilation in patients without COPD who develop respiratory failure, particularly when ICU beds are limited, though this must be balanced against infection control risks 1
• NIV is beneficial for COPD patients in acute hypercapnic respiratory failure 1

Fluid Management and Cardiovascular Support

• Assess all patients for volume depletion and provide intravenous fluids as clinically indicated 1, 2, 3
• Monitor for cardiac complications including exacerbation of pre-existing cardiac disease, primary myocarditis, heart failure, and arrhythmias 1, 2
• In patients with elevated cardiac biomarkers, obtain ECG immediately and check troponin levels to confirm myocardial injury 2
• Consider ICU transfer for patients with cardiogenic shock, persistent hypotension, or severe cardiac dysfunction on echocardiography 2

Vital Sign Monitoring

• Monitor temperature, respiratory rate, pulse, blood pressure, mental status, oxygen saturation, and inspired oxygen concentration at least twice daily, using an Early Warning Score system 1
• Increase monitoring frequency for patients with severe illness or requiring continuous oxygen therapy 1
• Failure to improve within 48 hours warrants full clinical reassessment, and lack of improvement over 4 days indicates need for repeat chest radiograph 1

Nutritional and Adjunctive Support

• Provide nutritional support (enteral, parenteral, or nasogastric feeding) in severe or prolonged illness 1
• Physiotherapy may benefit selected patients with excess bronchial secretions, particularly those with concurrent COPD 1

Symptomatic Treatment

• Use oral antipyretics (paracetamol or NSAIDs) with adequate oral hydration for uncomplicated influenza 3
• Avoid aspirin in children due to risk of Reye's syndrome 1

Discharge Criteria and Follow-up

Patients should have fewer than two of the following unstable factors before discharge 1:

• Temperature >37.8°C
• Heart rate >100/min
• Respiratory rate >24/min
• Systolic blood pressure <90 mmHg
• Oxygen saturation <90%

Patients should seek immediate medical attention for shortness of breath, bloody sputum, drowsiness/confusion, fever persisting 4-5 days, or recurrence of high fever after initial improvement 3

Common Pitfalls

• Do not delay oxygen therapy while awaiting blood gas results in obviously hypoxic patients 1
• Avoid high-flow oxygen in COPD patients without arterial blood gas monitoring, as this may worsen hypercapnia 1
• Remember that immunocompromised and elderly patients may not mount adequate febrile response despite severe illness 1
• Volume depletion is commonly overlooked but critical to address early 1, 3