Asthma

• Affects 5% of the population
• Reversible airways disease characterised by episodes of dyspnoea, cough and wheeze
• Caused by;
  • Bronchial smooth muscle contraction
  • Mucosal swelling/inflammation
  • Increased mucus production

• Ask patient about;
  • Precipitants – exercise, cold weather, allergens, infections, drugs (aspirin, NSAIDs, ?-blockers)
  • Diurnal variation
  • Exercise tolerance
  • Disturbed sleep – quantify as nights per week (this is a sign of severe asthma)
  • Acid reflux – known association with asthma
  • Other atopic disease
  • Specifics about the home – pets, carpets, feather pillows
  • Occupation
  • Days off a week from work or school

Signs

• Tachypnoea, audible wheeze, hyperinflated chest, hyperresonant percussion note, diminished air entry, widespread polyphonic wheeze
• Severe attack
  • Inability to complete sentences
  • Pulse >110
  • Respiratory rate >25
  • PEF 33-50% of predicted
• Life threatening
  • Silent chest
  • Bradycardia or hypotension
  • Exhaustion
  • PEF <33% predicted
  • Confusion
  • Poor respiratory effort
  • ABG normal/high PaCO2, PaO2 <8kPa, acidotic

Tests

• Acute attack
  • PEF, sputum culture, FBC, U&Es, CRP, blood cultures, ABG (if PaCO2 is raised transfer to ITU), CXR (to exclude infection or pneumothorax)
• Chronic asthma
  • PEF monitoring
  • Spirometry – obstructive defect
  • CXR – hyperinflation
  • Skin prick tests may help identify allergens
  • Aspergillus serology

DDX

• Pulmonary oedema
• COPD
• Large airway obstruction
• SVC obstruction
• Pneumothorax
• PE
  Bronchiectasis
• Obliterative bronchiolitis (suspect if elderly)

Associated diseases

• Acid reflux
• PAN
• Churg-Strauss syndrome
• ABPA

Management of chronic asthma

• Get patient to stop smoking
• Check inhaler technique
• Get patient to check PEF twice a day

British thoracic society guidelines

• Start at the step most appropriate for severity, moving up or down as needed until control is good for >3mth
• Rescue courses of prednisolone may be used at any time
  • Step 1
    • Occasional short acting ?2- agonist as required for symptom relief e.g. salbutamol (SE – tachycardia, reduced K+, tremor, anxiety
  • Step 2
    • Add standard dose short acting inhaled steroid e.g. beclomethasone or fluticasone
  • Step 3
    • Add long acting ?2- agonist e.g. salmeterol. If this benefits but there is still insufficient control increase dose of beclamethasone
  • Step 4
    • Consider trials of higher doses of beclamethasone, theophylline, modified release oral ?2- agonist or leukotriene receptor antagonist
  • Step 5
    • Add regular oral prednisolone

Aminophylline

• Metabolised to theophylline
• May act by inhibiting phosphodiesterase and thus decreasing bronchoconstriction by increasing cAMP
• Stick to one brand name (bioavailability variable)
• Narrow therapeutic range
• Check levels and do ECG monitoring after 24hr if IV therapy has been used
• Factors that may necessitate a reduction in dose;
  • Cardiac or liver failure, drugs which may increase the t1/2 e.g. cimetidine, ciprofloxacin, erythromycin, contraceptive steroids
• Factors which may require an increase in dose;
  • Smoking, drugs which shorten t1/2 e.g. phenytoin, carbamazepine, barbiturates, rifampicin

Anticholinergics

• Ipratropium, tiotropium may decrease muscle spasm but aren’t recommended under current asthma guideline (apart from sometimes under acute management)
• Useful in COPD

Leukotriene receptor antagonists

• Montelukast and zafirlukast

Anti-IgE monoclonal antibody

• Omalizumab may be of use in highly selected patients with persistent allergic asthma

Management of acute severe asthma

• Be calm
• History
  • Ask about usual and recent treatment
  • Previous acute episodes and their severity
  • Best PEF
  • Have they ever been admitted to ITU

Differential

• Acute infective exacerbation of COPD
• Pulmonary oedema
• URTI
• PE
• Anaphylaxis

Immediate management

• Sit patient up and give high dose O2
• Give salbutamol 5mg (or terbutaline 10mg) plus ipratropium bromide 0.5mg nebulised with O2
• Hydrocortisone 100mg IV or prednisolone 40-50mg PO or both if very unwell
• CXR to exclude pneumothorax
• If there are features of life-threatening disease present;
  • Inform ITU/seniors
  • Add magnesium suphate 1.2-2g IV over 20mins (only do this once)
  • Give salbutamol nebulisers every 15mins or 10mg continuously over 1hr

Further management

• If patient is improving;
  • 40-60% O2
  • prednisolone 40-50mg/24hr PO
  • Nebulised salbutamol every 4hr
  • Monitor peak flows and O2 sats
• If patient not improving after 15-30mins
  • Continue 100% O2 and steroids
  • Hydrocortisone 100mg IV or prednisolone 30mg if not already given
  • Give salbutamol nebulisers every 15mins of 10mg continuously for 1hr
  • Continue ipratropium 0.5mg every 4-6hr
• If patient is still not improving;
  • Discuss with seniors and ITU
  • Repeat salbutamol nebuliser every 15mins
  • Magnesium sulphate 1.2-2g over 20mins unless already given
  • Consider aminophylline – if not already on theophylline load with 5mg/kg IVI over 20mins, then 500?g/kg/hr where kg is ideal body weight
  • Do levels if infusion lasts more than 24hr
  • Alternatively give salbutamol IVI 3-20?g/min

Monitor effects of treatment

• Repeat PEF 15-30mins after initiating treatment
• Pulse ox monitoring – keep sats >92%
• Check ABG within 2hr
• Record PEF pre and post ?2- agonist in hospital at least 4 times

Once patient is improving

• Wean down and stop aminophylline over 12-24hr
• Reduce nebulised salbutamol and switch to inhaled ?2- agonist
• Initiate inhaled steroids and stop oral steroids if possible
• Continue to monitor PEF
• Look for the cause of the exacerbation

Discharge

• Before discharge patients must have;
• Been on discharge mediation for 24hr
• Have inhaler technique checked
• Have a peak flow >75% predicted or best with diurnal variation of <25%
• Steroid and bronchodilator therapy
• Own a PEF meter and have management plan
• GP appointment within 1 week
• Respiratory clinic within 4 weeks