When to Take a Patient with Flu to the Emergency Room
Patients with influenza require emergency department evaluation if they have severe pneumonia indicators (CRB-65 score ≥3, bilateral chest signs, or respiratory failure signs), or if they exhibit critical warning signs including persistent hypoxia, confusion, respiratory rate ≥30/min, blood pressure <90/60 mmHg, or oxygen saturation <90% on room air. 1
Primary Criteria for Immediate ER Referral
Severe Pneumonia Indicators
CRB-65 score of 3 or 4 mandates urgent hospital referral 2, 1
Bilateral chest signs on examination require immediate ER referral regardless of CRB-65 score, as this suggests primary viral pneumonia with a rapid, fulminant course 2, 1
Critical Respiratory Failure Signs
- Oxygen saturation <90% on room air 1
- Persistent hypoxia with PaO₂ <8 kPa despite supplemental oxygen 2, 1
- Progressive hypercapnia (rising CO₂ levels) 2, 1
- Severe acidosis with pH <7.26 2, 1
Hemodynamic Instability
- Septic shock (systolic BP <90 mmHg with signs of organ dysfunction) 2, 1
- New or worsening confusion, which signals severe illness 2, 1
Secondary Criteria Requiring ER Evaluation
Multiple Unstable Clinical Factors
Patients with 2 or more of the following should seek ER care: 1
- Temperature >37.8°C
- Heart rate >100/min
- Respiratory rate >24/min
- Systolic blood pressure <90 mmHg
- Oxygen saturation <90%
- Inability to maintain oral intake
- Abnormal mental status
Moderate Risk Pneumonia (CRB-65 Score of 2)
- These patients are at increased risk of death and should be considered for short-stay inpatient treatment or hospital-supervised outpatient treatment 2
- Clinical judgment is essential—err on the side of hospital evaluation for frail patients or those with significant comorbidities 1
Special Populations Requiring Lower Threshold for ER Referral
High-Risk Adults
The threshold for ER referral should be lower for: 1
- Patients with COPD, heart disease, or diabetes
- Frail or elderly patients
- Immunocompromised individuals
- Pregnant women
Children with Influenza
Children require urgent ER referral if they have any of the following: 2, 1
- Breathing difficulties
- Severe earache
- Vomiting for more than 24 hours
- Drowsiness or altered consciousness
- Inability to maintain oral intake
Clinical Pitfalls to Avoid
- Do not wait for chest X-ray results before referring patients with bilateral chest signs—clinical examination findings alone warrant immediate ER referral 2, 1
- Do not underestimate risk in patients who lack fever but have other severe features, particularly elderly or immunocompromised patients 3
- Do not delay ER referral for patients with worsening symptoms after initial improvement, as this may indicate secondary bacterial pneumonia, particularly with Staphylococcus aureus 4, 5
- Shortness of breath is the key distinguishing symptom that separates patients with pneumonia from those with uncomplicated upper respiratory illness 5
Patients Who Can Be Managed at Home
Patients with CRB-65 score of 0-1 are at low risk of death and can typically be treated at home, provided they have no other concerning features 2
Uncomplicated influenza without pneumonia does not require hospital care—the illness usually resolves in 7 days, though cough and malaise may persist for weeks 2, 3