|

Acute Asthma Exacerbation

Last updated:

Overview

Also known as status asthmaticus, an acute exacerbation of asthma is characterised by asthma that does not respond to usual treatment or asthma that is progressively worsening. Every emergency attendance for asthma should be regarded as acute severe asthma until proven otherwise.

Epidemiology

  • Around 75% of admissions for asthma are thought to be avoidable
  • Around 90% of deaths from asthma are thought to be preventable

Risk Factors

  • Previous near-fatal asthma
  • Previous admission for asthma, particularly if in the last year
  • Frequent emergency attendance for asthma, particularly in the last year
  • Asthma requiring 3 or more medications to manage
  • Increasing use of beta2-agonists
  • Having brittle asthma – this is asthma that is difficult to control and may unpredictably lead to life-threatening attacks
  • NSAID sensitivity
  • Smoking or passive smoking
  • Exposure to triggers/allergens such as animal fur
  • Pregnancy
  • Inadequately treated disease

Presentation

Overview

The British Thoracic Society (BTS) has guidelines that categorise patients into moderate, severe, life-threatening, and near-fatal asthma.

It should be noted that patients often initially present in respiratory alkalosis (high PaO2 and low PaCO2) as they are tachypnoeic. As the disease progresses, they can become exhausted and the PaO2 starts to decline and PaCO2 rises.

Moderate asthma

  • Peak expiratory flow rate (PEFR): 50-75% best (or predicted if best unknown)
  • Respiratory rate <25 /min
  • Pulse <100 bpm

Severe asthma

  • PEFR 33-50% best (or predicted if unknown)
  • Respiratory rate >25 /min
  • Pulse >110 bpm

Life-threatening asthma

  • PEFR <33% best (or predicted if unknown)
  • Oxygen saturations <92%
  • Signs of exhaustion:
    • PaO2 <8kPa
    • Normal PaCO2
  • Cyanosis
  • Silent chest
  • Poor respiratory effort
  • Arrhythmia
  • Hypotension
  • Exhaustion
  • Altered consciousness

Near-fatal asthma

  • PaCO2 raised

Investigations

In the community and hospital

  • Peak flow measurements – to help gauge severity
  • Pulse oximetry – to help gauge the severity

In hospital

  • Arterial blood gases – if patients show signs of life-threatening asthma
  • Consider a chest x-ray if there is suspicion of another condition such as pneumothorax

Management

Referral to hospital

The following patients should be referred to hospital:

  • All patients with life-threatening asthma
  • Severe asthma that is non-responsive to initial treatment
  • Previous near-fatal attack
  • The patient has brittle asthma
  • Presentation at night
  • Pregnancy
  • People under 18 years
  • Poor compliance
  • Person lives alone
  • Learning difficulties

All patients

  • 15L oxygen via non-rebreathe mask (aim for SpO2 94-98%) + short-acting beta2-agonists (SABA) + corticosteroids:
    • If patients have moderate/severe asthma, SABAs can be given through pressurised metered-dose inhalers (pMDI)
    • If patients have life-threatening/near-fatal asthma, nebulised SABAs are used
    • The corticosteroid should be continued for at least 5 days following the attack
  • Nebulised ipratropium bromide:
    • If patients have not responded to SABA + corticosteroid treatment or have a severe/life-threatening attack
  • IV magnesium sulfate
    • This is often given for severe/life-threatening asthma
  • IV aminophylline – must be started under specialist guidance
  • Escalate to intensive care and consider intubation and ventilation or extracorporeal membrane oxygenation (ECMO) 

Discharging from hospital

Patients should only be discharged following treatment provided all of the following apply:

  • They have been stable on their medication they are to be discharged with
  • Their inhaler technique has been checked and recorded
  • They have been given a personal asthma action plan
  • Their PEFR is >75% of their best (or predicted if best unknown)

Patient Advice

  • All patients with asthma should have regular reviews and a personal asthma action plan
  • Patients should be encouraged to self-monitor using peak expiratory flow rate (PEFR) measurements
  • Patients should minimise exposure to or avoid triggers where possible e.g. cigarette smoke, irritants, pollen, animal dander etc.
  • Patients should avoid NSAIDs and beta-blockers where necessary
    • These can precipitate asthma attacks

Complications

Author