FFS: Asthma
Asthma is a common, potentially life-threatening chronic respiratory condition. While it is manageable, it is not curable. All ED presentations require:
- Consideration of past history for disposition planning
- Assessment of attack severity
Pathophysiology
Asthma is characterised by:
- Bronchospasm
- Airway inflammation
- Mucous plugging
Common Triggers
- Allergens (e.g. pollens)
- Viral respiratory infections
- Air pollutants
- Smoking
- Exercise
- Emotional stress
- Drugs: aspirin, NSAIDs, beta-blockers
Clinical Assessment
Key History
- Patient’s subjective severity rating
- Past admissions (ICU, intubation, NIV)
- Treatment history, frequency of reliever use
- Duration of current episode
Examination Priorities
- Ability to speak
- Consciousness
- Work of breathing
- Pulse rate
- Breath sounds
- Wheeze is unreliable — a silent chest in a distressed patient is a red flag
- Lung function tests (PEFR, FEV1)
- Cyanosis (late, life-threatening sign)
Severity Classification
Parameter | Mild | Moderate | Severe/Life-Threatening |
---|---|---|---|
Consciousness | Normal | Normal | Altered |
Respiratory effort | Normal | Increased | Marked ± paradoxical movement |
Speech | Sentences | Phrases | Words or unable to speak |
Pulse rate (bpm) | <100 | 100–120 | >120 (Bradycardia = impending arrest) |
Breath sounds | Moderate wheeze | Loud wheeze | Silent chest / poor air entry |
PEFR (% predicted) | >75% | 50–75% | <50% or <100 L/min |
FEV1 (% predicted) | >75% | 50–75% | <50% or <1 L |
Cyanosis | No | No | Yes |
SpO₂ | >95% | 92–95% | <92% |
ABGs (if done) | Normal | PaCO₂ >40 = concern | PaCO₂ >45 or PaO₂ <60 = respiratory failure |
Differential Diagnosis of Wheeze
- Upper airway obstruction (stridor)
- LVF (cardiac asthma)
- COPD
- Lymphangitic carcinomatosis
- Aspiration
- Multiple PEs (rare)
Investigations
Test | Purpose/Notes |
---|---|
FBC, CRP | Rule out infection |
U&Es, glucose | Monitor for salbutamol-induced hypokalaemia |
ABG/VBG | PaCO₂ >45 mmHg = late/severe sign |
CXR | If severe, poor response, or diagnosis unclear (e.g. PTX, pneumonia) |
ECG | If unwell, to assess for arrhythmias/ischemia |
Sputum M&C | If infection suspected |
Management
1. Oxygen
- Aim SpO₂ ≥ 90%
- Use high-flow O₂ as needed
2. Bronchodilators
Drug | Route/Dose |
---|---|
Salbutamol | 5 mg neb PRN or continuously; use O₂-driven nebs |
Ipratropium | 500 mcg neb every 20 mins for 1 hour (up to 3 doses), then hourly as needed |
3. Corticosteroids
Route | Indication | Examples |
---|---|---|
Oral | Mild exacerbations | Prednisone |
IV | Moderate/severe | Dexamethasone 10 mg stat, then 5 mg TDS or Hydrocortisone 100 mg QID |
4. Magnesium Sulphate
- For severe asthma
- 10 mmol (2.5 g) IV over 20 mins
5. CPAP (5 cm H₂O)
- Consider in severe cases to reduce WOB and prevent intubation
6. IV Beta Agonists
- Salbutamol IV infusion in unresponsive or agitated patients
7. Aminophylline
- Consider in select cases unresponsive to beta agonists
- Narrow therapeutic index; monitor levels closely
8. Adrenaline
- Use if anaphylaxis suspected
- Nebulised (4 x 1:1000 ampoules) or IV infusion
Intubation & Mechanical Ventilation
Indications
- Deterioration despite maximal therapy
- Reduced LOC
- Severe exhaustion
- Hypoxia/CO₂ retention
- Arrest or peri-arrest
Induction
- Ketamine 1–2 mg/kg IV
→ Bronchodilator and preserves reflexes - Suxamethonium 1.5 mg/kg IV
Ventilation Strategy: Permissive Hypercapnia
Setting | Target |
---|---|
FiO₂ | 100% initially |
Vt | ≤6 mL/kg IBW (↓ to 3–4 mL/kg in severe cases) |
Rate (f) | 6–8/min |
PEEP | Off |
I:E ratio | ≥1:4 (reduce insp time) |
pH tolerance | >7.1 (allow hypercapnia) |
Avoid increasing RR to correct CO₂ — may cause barotrauma.
Other Considerations
- Deep sedation ± paralytics
- Gastric decompression
- Dynamic hyperinflation: disconnect ETT for 20–30s
- Watch for pneumothorax (CXR/USS)
Asthma-Related Cardiac Arrest
- LUCAS device: consider prolonged resus — asthma is reversible
- IV Fluids: treat hypovolaemia (1–2L crystalloids)
- IV Salbutamol / Aminophylline / Adrenaline infusion
- Bilateral finger thoracostomy (if tension PTX suspected)
- Manual chest compression during ETT disconnection
- Correct hypokalaemia
- Ultrasound: assess for cardiac activity, pericardial effusion, PTX
- ECMO: consider if available in refractory cases
Disposition
Admit if:
- Severe presentation
- Moderate presentation + high-risk history
- Poor response to ED treatment
- Frequent presentations or poor social support
Discharge criteria (consider post-treatment PEFR):
PEFR (% predicted) | Disposition |
---|---|
>70% | Likely safe to discharge |
40–70% | SSU admission |
<40% | Admit ward/HDU |
Consider asthma educator referral for all patients.
References
FOAMed
- Nickson C. Acute Severe Asthma. CCC
- Nickson C. Non-invasive ventilation (NIV) and asthma. CCC
- Flower O. Severe asthma management. LITFL
- Guthrie K. Case of Acute Severe Asthma. LITFL
- Cadogan M. EMI 026 Acute Asthma Guidelines. LITFL
Resources
Fellowship Notes
Educator, magister, munus exemplar, dicata in agro subitis medicina et discrimine cura | FFS |