The British Thoracic Society (BTS) classify patients with acute asthma into moderate, severe or life-threatening categories.

Note that a patient having any one of the life-threatening features should be treated as having a life-threatening attack.

A fourth category, 'Near-fatal asthma', is also recognised characterised by a raised pCO2 and/or requiring mechanical ventilation with raised inflation pressures.

Further assessment

• the BTS guidelines recommend arterial blood gases for patients with oxygen sats < 92%
• a chest x-ray is not routinely recommended, unless:
  • life-threatening asthma
  • suspected pneumothorax
  • failure to respond to treatment

Management

• admission
  • all patients with life-threatening should be admitted in hospital
  • patients with features of severe acute asthma should also be admitted if they fail to respond to initial treatment.
  • other admission criteria include a previous near-fatal asthma attack, pregnancy, an attack occurring despite already using oral corticosteroid and presentation at night
• oxygen
  • if patients are hypoxaemic, it is important to start them on supplemental oxygen therapy
  • if patients are acutely unwell they should be started on 15L of supplemental via a non-rebreathe mask, which can then be titrated down to a flow rate where they are able to maintain a SpO‚‚ 94-98%.
• bronchodilation with short-acting beta‚‚-agonists (SABA)
  • high-dose inhaled SABA e.g. salbutamol, terbutaline
  • in patients without features of life-threatening or near-fatal asthma, this can be given by a standard pressurised metered-dose inhaler (pMDI) or by an oxygen-driven nebulizer
  • in patients with features of a life-threatening exacerbation of asthma, nebulised SABA is recommended
• corticosteroid
  • all patients should be given 40-50mg of prednisolone orally (PO) daily, which should be continued for at least five days or until the patient recovers from the attack
  • during this time, patients should continue their normal medication routine including inhaled corticosteroids.
• ipratropium bromide: in patients with severe or life-threatening asthma, or in patients who have not responded to beta‚‚-agonist and corticosteroid treatment, nebulised ipratropium bromide, a short-acting muscarinic antagonist
• IV magnesium sulphate
  • the BTS notes that the evidence base is mixed for this treatment that is now commonly given for severe/life-threatening asthma
• IV aminophylline may be considered following consultation with senior medical staff
• patients who fail to respond require senior critical care support and should be treated in an appropriate ITU/HDU setting. Treatment options include:
  • intubation and ventilation
  • extracorporeal membrane oxygenation (ECMO)

Criteria for discharge

• been stable on their discharge medication (i.e. no nebulisers or oxygen) for 12-24 hours
• inhaler technique checked and recorded