Acute Asthma Attack

An asthma attack is an acute exacerbation of symptoms caused by excessive bronchoconstriction and respiratory obstruction. This article discusses asthma attacks in adults.

Causes

• An environmental allergen
• Viral or bacterial infections
• Exercise
• Stress or emotional factors

Clinical Features

Patients will typically present with tachypnoea, dyspnoea, wheeze and tachycardia, and they may visibly be in respiratory distress e.g. sitting in the tripod position or using their accessory muscles to breathe. Auscultation may elicit audible wheeze.

Asthma attacks are classified into moderate, severe, life-threatening or near fatal based on various criteria.

PEFR = Peak expiratory flow rate

RR = Respiratory Rate

Differential Diagnosis

• Foreign body or airway obstruction: This can cause a localised wheeze
• COPD exacerbation
• Pulmonary embolism
• Anaphylaxis

Investigations

1. Oxygen Saturations: Aiming for saturations of 94-98%.
2. Arterial Blood Gas: This is repeated within an hour of starting treatment, particularly if the patient deteriorates.
3. PEFR: Monitored every 15-30 minutes since treatment has started
4. Chest X-ray: Not routinely performed but may be useful if considering an alternate diagnosis

Management

Patients with acute presentations are largely managed with the A-E approach i.e. Airway, Breathing, Circulation, Disability and Exposure. The following list outlines the basic principles of acute asthma attack therapy, as per BTS and SIGN guidelines.

1. O2: Supplementary oxygen to maintain oxygen saturations of 94-98% (or 88-92% in chronic carbon dioxide retainers)
2. Beta-2 Agonist: High dose inhaled beta-2 agonist is the first-line therapy for an acute asthma attack e.g. salbutamol. Note – nebulised salbutamol can cause or exacerbate a hypokalaemia so it is important to monitor this.
3. Steroids: Steroid treatment is given to all patients with acute asthma attacks – this is typically in the form of oral prednisolone although alternatives such as IM methylprednisolone or IV hydrocortisone may be used.
   1. Example dose: Prednisolone 40-50mg OD for at least 5 days
   2. Example dose: Hydrocortisone 400mg (100mg every 6 hours)
4. Ipratropium Bromide: Add nebulised ipratropium bromide to the beta-2 agonist if patient has had poor response to the initial dose of beta-2 agonist, or if the patient is having a severe or life-threatening asthma attack.
   1. Example dose: 0.5mg every 4-6 hours
5. Magnesium Sulfate: If initial therapy which bronchodilators has a poor response, patients with a PEFR <50% can be given IV magnesium sulfate, but a senior should be consulted prior to administrating this.
6. IV Aminophylline: This is not routinely used but may be used if patients have had poor response to the aforementioned therapy, but again, senior consultation is needed prior to initiation.
7. Non-Invasive Ventilation (NIV): NIV is indicated in patients with a type II respiratory failure secondary to their asthma attack, and such patients should be admitted to ITU.
8. Invasive Ventilation: If the patient is tiring despite treatment, a call to anaesthetics may be necessary for invasive ventilation.

Hospital Admission Criteria

As per NICE/BTS guidance, patients with the following criteria should be admitted to hospital:

• Life-threatening or near-fatal asthma attack
• Persistent features of a severe asthma attack despite initial treatment

ITU Admission Criteria

The following scenarios may indicate an admission for ITU or HDU:
 

• Worsening PEFR
• Hypercapnia
• Hypoxia which is worsening or failing to improve
• Altered consciousness
• Worsening acidosis on ABG

It's really important to always keep an ITU admission at the back of your mind when managing a patient with an acute asthma attack.

Discharge

It is important to deliver adequate patient education on discharge, which should include inhaler technique, personalised asthma action plan and PEFR diary. Patients with a PEFR >75% of best or predicted following an hour of treatment can be discharged. However, if such patients are pregnant, have a history of near-fatal asthma attacks, are socially isolated or there are concerns regarding compliance to treatment, hospital admission may be warranted.

References

https://www.brit-thoracic.org.uk/document-library/guidelines/asthma/btssign-guideline-for-the-management-of-asthma-2019/

https://bnf.nice.org.uk/treatment-summary/asthma-acute.html

https://acaai.org/asthma/symptoms/asthma-attack