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:

  1. Bronchospasm
  2. Airway inflammation
  3. 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

ParameterMildModerateSevere/Life-Threatening
ConsciousnessNormalNormalAltered
Respiratory effortNormalIncreasedMarked ± paradoxical movement
SpeechSentencesPhrasesWords or unable to speak
Pulse rate (bpm)<100100–120>120 (Bradycardia = impending arrest)
Breath soundsModerate wheezeLoud wheezeSilent chest / poor air entry
PEFR (% predicted)>75%50–75%<50% or <100 L/min
FEV1 (% predicted)>75%50–75%<50% or <1 L
CyanosisNoNoYes
SpO₂>95%92–95%<92%
ABGs (if done)NormalPaCO₂ >40 = concernPaCO₂ >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

TestPurpose/Notes
FBC, CRPRule out infection
U&Es, glucoseMonitor for salbutamol-induced hypokalaemia
ABG/VBGPaCO₂ >45 mmHg = late/severe sign
CXRIf severe, poor response, or diagnosis unclear (e.g. PTX, pneumonia)
ECGIf unwell, to assess for arrhythmias/ischemia
Sputum M&CIf infection suspected

Management

1. Oxygen

  • Aim SpO₂ ≥ 90%
  • Use high-flow O₂ as needed

2. Bronchodilators

DrugRoute/Dose
Salbutamol5 mg neb PRN or continuously; use O₂-driven nebs
Ipratropium500 mcg neb every 20 mins for 1 hour (up to 3 doses), then hourly as needed

3. Corticosteroids

RouteIndicationExamples
OralMild exacerbationsPrednisone
IVModerate/severeDexamethasone 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

SettingTarget
FiO₂100% initially
Vt≤6 mL/kg IBW (↓ to 3–4 mL/kg in severe cases)
Rate (f)6–8/min
PEEPOff
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

  1. LUCAS device: consider prolonged resus — asthma is reversible
  2. IV Fluids: treat hypovolaemia (1–2L crystalloids)
  3. IV Salbutamol / Aminophylline / Adrenaline infusion
  4. Bilateral finger thoracostomy (if tension PTX suspected)
  5. Manual chest compression during ETT disconnection
  6. Correct hypokalaemia
  7. Ultrasound: assess for cardiac activity, pericardial effusion, PTX
  8. 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

Resources

Fellowship Notes

Dr James Hayes LITFL Author Medical Educator

Educator, magister, munus exemplar, dicata in agro subitis medicina et discrimine cura | FFS |

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