Asthma in Emergency

Introduction

Most asthma deaths occur outside hospital and are:

• In patients with chronic severe disease
• In those receiving inadequate medical treatment
• In those who have been symptomatically deteriorating, and may have already sought medical help
• Associated with adverse behavioural and psychological factors

Asthma Assessment

Mild-Moderate (maybe admitted to hospital or more likely may improve and go home)

• SaO2 >95% room air
• Tachypnea <25
• Able to talk in sentences or phrases
• No accessory muscle use
• Alert
• Skin Colour: Normal
• Chest auscultation: Normal or Wheeze

Severe (admitted to hospital)

• SaO2 90- 95% room air
• Tachypnea >25bmp
• Mild to moderate tachycardia for age
• Can only speak a few words in one breath
• Mild-moderate use of accessory muscle
• Skin colour: Pallor
• Chest auscultation: Wheeze

Life-Threatening (Admitted to hospital possible transferred to a higher level faculty)

• SaO2 <90% room air
• Tachypnea >30
• Tachycardia or Bradycardia
• Able to talk in words or unable to speak or cry
• Moderate to severe accessory muscle use
• Agitation, drowsy or confused
• Skin colour: Cyanosis
• Chest auscultation: Silent chest or reduced air entry

Mild/Moderate Asthma

Mild (maybe admitted to hospital or more likely may improve and go home)

• SaO2 >95% room air
• Able to talk in sentences
• No accessory muscle use
• Alert

Management:

• Short-acting Beta2 receptor agonist (ie. Salbutamol with spacer)
  • Reassess, Repeat bronchodilator, Reassess, Repeat
• +/- Anticholinergic - Ipratobium bromide (if bronchodilator alone has poor response)
  • Reassess, Repeat Ipatropium bromide, Reassess, Repeat
• Oral prednisolone
  • Reassess at 1 hour after starting bronchodilator, monitor and continue discharge
• Continue to severe management if not improving

Discharge

• Discharge summary
• Discharge medication (+spacer)
• Educate
• Asthma action plan
• Follow up with GP

Acute Severe Asthma

Severe asthma defined as:

• PEFR 33-55% predicated or best
• RR >25
• HR >110
• SaO2 90- 95% room air
• Can only speak a few words in one breath
• Mild-moderate use of accessory muscle
• Skin colour: Pallor
• Chest auscultation: Wheeze

Management

• Oxygen
• Short-acting Beta2 receptor agonist (ie. Salbutamol with spacer)
  • Reassess, Repeat bronchodilator, Reassess, Repeat
• +/- Anticholinergic - Ipratobium bromide (if bronchodilator alone has poor response)
  • Reassess, Repeat Ipatropium bromide, Reassess, Repeat
• Oral prednisolone (the earlier given in an attack, the better the outcome) - or IV hydrocortisone if unable to tolerate oral
  • Reassess at 1 hour after starting bronchodilator
  • Monitor
  • Discharge
• +/- IV salbutamol
• +/- IV magnesium sulphate immediately if very severe
• +/- IV aminophylline some patients may respond, give if poor response to initial therapy
• IV fluids - patients are often dehydrated
• Antibiotics - if evidence of infection

Indications for invasive ventilation in asthma

• Coma
• Respiratory arrest
• Exhaustion
• Deteriorating ABG

Life-threatening Asthma

Life-threatening asthma any one of:

• PEFR <33%
• SaO2 <90%
• Silent chest (soft/absent breath sounds)
• Cyanosis
• Bradycardia/arrythmia/hypotension
• Exhaustion
• Confusion
• Coma

Management

• β-agonist (Salbutamol via continous nebulisation)
• Anticholinergic - Ippatropium Bromide
• Steroids (the earlier given in an attack, the better the outcome)
• IV salbutamol
• IV magnesium sulphate immediated if very severe
• IV aminophylline some patients may respons, give if poor response to intitial therapy
• +/- Intubation and ventilation
• IV fluids patients are often dehydrated
• Antibiotics only if an infection caused exacerbation

Indications for assisted ventilation in asthma

• Coma
• Respiratory arrest
• Exhaustion
• Deteriorating ABG

Image from Australian asthma handbook

Pathogenesis Asthma Exacerbations

Airway obstruction occurs due to a combination of:

• Inflammatory cell infiltration
• Mucus hypersecretion with mucus plug formation
• Smooth muscle contraction

Long-term uncontrolled asthma can lead to air trapping and asthma exacerbations through what is called dynamic hyperinflation.

• Airflow obstruction → Slow expiratory airflow and incomplete gas exhalation dynamic hyperinflation → Patient takes next breath → Gas becomes trapped in alveoli
• Gas becomes trapped in alveoli until the alveoli can not hold any more gas and exhaled volume = inhaled volume → Equilibrium

Mild asthma

• Only most severely obstructed airways collapse
• Collapsed airways with air trapping results in:
  • Decreased expiratory reserve volume
  • Increased residual volume

As asthma gets more severe

• Expiratory reserve diminishes and this results in profound dyspnoea

Complications of Asthma exacerbations

• Cardiac arrest
• Respiratory failure/arrest
• Hypoxaemia with CNS injury
• Pneumothorax
• Toxicity with medications
• Aspiration/pneumonia
• Nosocomial infection