acute severe asthma

An exacerbation of asthma that has not been controlled by the use of standard medication

Aetiology

Could be triggered by any of the typical asthma triggers, such as infection, exercise or cold weather

Clinical features

Moderate	Severe	Life threatening
Peak flow > 50% predicted	Peak flow < 50% predicted	Peak flow < 33% predicted
Normal speech	Saturations > 92%	Saturations < 92%
No features listed across	Unable to complete sentences in one breath	Exhaustion and poor respiratory effort
	Signs of respiratory distress	Hypotension
	Respiratory rate:

40 in 1-5 years 30 in > 5 years | Silent chest | | | Heart rate: 140 in 1-5 years 125 in > 5 years | Cyanosis | | | | Altered consciousness/confusion |

A normal PaCO2 suggests that the patient has life-threatening asthma, as it would be initially low due to hyperventilation
- As the patient tires, they become normocapnic then hypercapnic

Investigations

Monitor patient with ABGs and pulse oximetry
Features suggesting very severe life-threatening attacks are:
- A high PaCO2 of >6 kPa
- Severe hypoxaemia: PaO2 <8 kPa despite treatment with oxygen
- Low and/or falling arterial pH
CXR to exclude pneumothorax

Management

100% O2 (non-rebreathing mask) with the patient sat upright in bed
Nebulisers: give 5mg salbutamol with 0.5mg ipratropium bromide via nebulizer on 100% O2
Steroids: 50mg prednisolone orally or IV hydrocortisone 100mg IV (if severe)
- Both can be given both if very unwell
- The BNF advises that patients should take 40-50mg prednisolone for ≥ 5days following an acute asthma episode - can reduce risk of relapse
  - The first dose can be given in A&E
If asthma is severe treatment decisions such as aminophylline, IV salbutamol and IV magnesium sulphate are normally under senior guidance
Intubation in worst cases - however this decision should be made early because it is very difficult to intubate with severe bronchoconstriction
For a patient to be discharged from hospital following an asthma attack they must be stable on their regular asthma regime for 12-24 hours

Complications

Tension pneumothorax