Saturday, 30 October 2010

MRCP revision battle 37.3: Asthma

Asthma is a condition characterised by periods of dyspnoea, cough and wheeze caused by reversible airways obstruction.

Asthma diagnosis

The table below (from the 2009 BTS/SIGN guidelines) lists the factors that increase or decrease the probability of the presentation being asthma:

If from history/examination you believe there is a:
  • high probability the patient has asthma --> being a trial of treatment
  • intermediate probability of asthma --> perform spirometry:
    • FEV1/FVC <0.7 - trial asthma treatment
    • FEV1/FVC >0.7 - refer to specialist

After a trial of treatment >400mls improvement in FEV1 or PEFR >15% is significant

In a peakflow diary, look for diurnal variation >25%

Treatment of asthma

Treatment of asthma follows a stepwise approach (BTS/SIGN guidelines):

  1. Mild intermittent asthma
    •  SABA (short-acting inhaled beta 2 agonist) PRN 
    • salamol, salbutamol
  2. Regular preventor therapy
    • corticosteroid 200-800mcg per day
    • beclometasone, fluticasone, budesonide
  3. Initial add-on therapy
    • LABA (long-acting inhaled beta 2 agonist (eg salmeterol))
    • if this doesn't work, stop and trial an oral therapy such as leukotriene receptor antagonist or theophylline
  4. Persistant poor control
    • increase steroid inhaler up to 2000mcg per day
    • add leukotriene receptor antagonist or theophylline
  5. Continuous or frequent oral steroids

If stable for 3 months, consider stepping down a step.

Severity of asthma

In acute asthma attacks, severity may be graded as follows:

  • unable to complete sentences
  • RR>25
  • PEFR<50% predicted or best
  • pulse >110

  • silent chest
  • PEFR <33% predicted or best
  • bradycardia
  • hypotension
  • normal or raised CO2
  • exhaustion

Management of acute severe asthma

Think 'O! sip Ma':
  • high flow oxygen
  • 5mg salbutamol neb
  • 500mcg ipratropium neb
  • 30mg prednisolone (or 100mg hydrocortisone IV)
  • magnesium 1.2g and aminophylline if still not improving
And make sure ITU know if things aren't going well....

Now for a battle with cor pulmonale...