Reading Part A Text
Acute Exacerbation of Asthma: Texts
Asthma (reversible airway obstruction caused by bronchospasm, mucosal oedema and increased mucus secretion) may be triggered by a variety of stimuli. Acute exacerbations can be precipitated by:
- respiratory infections (viral or bacterial)
- allergen exposure (e.g. pollen, dust mites, animal dander)
- environmental irritants (e.g. cigarette smoke, air pollution)
- exercise or cold air
- non-adherence to preventer therapy
Clinically, exacerbations are classified as:
- mild, where symptoms are present but the patient can speak in full sentences and oxygen saturations remain ≥95%
- moderate, where there is increased work of breathing and SpO₂ is 91–94%
- severe or life-threatening, where the patient cannot complete sentences, SpO₂ is <90%, or a silent chest is noted on auscultation
Management of Acute Asthma Exacerbation
Immediate management:
- Sit the patient upright and provide supplemental oxygen to maintain SpO₂ 93–95%
- Administer a short-acting beta₂-agonist (SABA) via spacer or nebuliser
- Initiate systemic corticosteroids promptly
Clinical assessment:
- Obtain full patient history, including onset, duration and precipitating factors
- medication history – note current preventer and reliever inhalers, including dose and frequency
- Perform standard clinical observations. Examine and record:
- respiratory rate, heart rate, blood pressure and temperature
- oxygen saturation by pulse oximetry
- peak expiratory flow rate (PEFR) as a percentage of predicted
- Perform physical examination. Assess:
- use of accessory muscles
- presence of wheeze, chest tightness or cough
- air entry bilaterally
- signs of cyanosis or altered consciousness
Management:
- Repeat SABA every 20 minutes in the first hour if required
- Add ipratropium bromide nebuliser for moderate to severe exacerbations
- Administer systemic corticosteroids – prednisolone (preferable); if unable to take orally, use intravenous hydrocortisone
- Consider intravenous magnesium sulphate if response to initial bronchodilators is poor
- If in doubt about severity, treat as a severe exacerbation and reassess frequently
- Arrange chest X-ray if pneumothorax or consolidation is suspected
Drug Therapy Protocol:
Authorised Indigenous Health Worker (IHW) must consult Medical Officer (MO) or Nurse Practitioner (NP).
Scheduled Medicines Rural & Isolated Practice Registered Nurse may proceed.
| Drug | Form | Strength | Route | Recommended Dosage | Duration |
|---|---|---|---|---|---|
| Salbutamol (SABA) | MDI + Spacer | 100 mcg/actuation | Inhaled | Adult & child ≥6 yrs: 4–8 puffs; repeat every 20 min up to 3 doses in 1st hour | Stat; further doses on MO/NP order |
| Nebuliser solution | 5 mg/mL | Inhaled (nebulised) | Adult: 2.5–5 mg per dose; child: 0.15 mg/kg per dose (min 1.25 mg, max 5 mg) | Stat; further doses on MO/NP order | |
| Prednisolone | Tablet | 25 mg | Oral | Adult: 40–50 mg daily; child: 1 mg/kg/day (max 40 mg/day) | 5 days; further on MO/NP order |
| Hydrocortisone | Powder for injection | 100 mg/vial | IV (IHW may not administer IV) | Adult: 100–200 mg every 6 hours; child: 4 mg/kg every 6 hours (max 100 mg) | Further doses on MO/NP order |
Use lower end of dose ranges in patients ≥65 years or those with significant comorbidities.
Provide Consumer Medicine Information: advise salbutamol can cause tremor and tachycardia.
Hypokalaemia may occur with repeated high-dose salbutamol – monitor serum potassium if prolonged use.
Ipratropium bromide 0.5 mg nebulised may be added for severe exacerbations; administer together with salbutamol nebuliser.
Technique for nebulised salbutamol administration – the same principles apply when adding ipratropium bromide
- Check the patient’s prescribed dose and confirm the absence of known hypersensitivity to salbutamol.
- Draw up the calculated dose of salbutamol solution and dilute with normal saline to a total volume of 3–4 mL in the nebuliser chamber.
- Ensure any tight-fitting clothing or restrictive garments are loosened around the patient’s chest before commencing treatment.
- Attach the nebuliser mask securely, or use a mouthpiece if the patient is co-operative and able to breathe through the mouth. A mouthpiece is preferable as it delivers more drug to the lower airways.
- Set the driving gas flow rate to 6–8 litres per minute using oxygen or air, depending on the patient’s SpO₂ level. Use air as the driving gas if SpO₂ is ≥95% to avoid suppressing hypoxic drive in susceptible patients.
- Instruct the patient to breathe tidally through the device until the nebuliser begins to splutter, indicating the chamber is nearly empty. Average treatment duration is 8–10 minutes.
- Do not shake the nebuliser chamber during treatment, as this may disrupt aerosol generation.
- After completion, reassess the patient’s respiratory rate, SpO₂, PEFR and auscultate the chest to evaluate response.