Asthma

Question 1

What is Asthma?

Answer 1

Asthma= a chronic inflammatory airways disease that causes variable airobstruction. The smooth muscle in the airways is hypersensitive to certain stimuli and respond by constricting causing airflow obstruction. This bronchoconstriction is reversible with bronchodilators.

An atopic type 1 hypersensitivity reaction

Question 2

Asthma: Symptoms

Answer 2

Symptoms are episodic and are of dirunal variability, they also vary in severity:
* dysponea
* wheeze
* cough (dry or productive)
* chest tightness

Asthmatics may have experienced similar symptoms in the past (HPC) and may have a PMH of other atopic conditions.

Question 3

Asthma: Aetiology/Triggers

Answer 3

Triggers vary between individuals:
* Nighttime or early morning
* Exercise
* Strong emotions
* Infection
* Cold, damp or dusty air
* Animals
* Beta-blocker and NSAIDs (asthmatics tend to be sensitive to aspirin and develop nasal polyps)
* Environmental conditions at work/school
* Smoking

Question 4

Asthma: Examination Signs

Answer 4

• tachyponea, tachycardia
• use of accessory muscles
• widespread polyphonic expiratory wheeze

Acute asthma
* reduced breath sounds
* silent chest (ie. no wheeze or breath sounds)

Question 5

Asthma: Investigations

Answer 5

• Oxygen Sats, RR, PR, BP, FBC, CRP, U+Es, LFTs, ABGS, CXR
• ABGs: respiratory alkalosis -> type 1 respiratory failure -> type 2 respiratory failure
• FeNO3 > 40ppb - unreliable with smokers as reduced
• Spirometry with BDR - FEV1:FEV < 70% shows obstructive pathology; FEV1 increase > 12% with BDR confirms asthma
• Peak flow diary - 2 times daily for 2-4 weeks. >20% variability
• Direct bronchial challenge test - PC20 at =/< 8mg/dl (20% reduction in of FEV) with histamine or metacholine

Tests are used to categorise patients into low, medium or high probability of asthma. Diagnosis is only confirmed after positive response to treatment.

Children < 17yrs: only do FeNO3 if spirometry+BDR doesn’t confirm asthma

Question 6

Asthma: Treatment

Answer 6

Stepwise ladder:

1. Short-acting beta-2 agonist inhaler(e.g.salbutamol) as required (move up if used >3x/week)
2. Inhaled corticosteroid(low dose) taken regularly
3. Inhaled corticosteroid(low dose) + Long-acting beta-2 agonists(e.g., salmeterol) ormaintenance and reliever therapy(MART)
   
   • Increase theinhaled corticosteroid(medium dose) -/+ LABA
   • Increase theinhaled corticosteroid(medium dose) +/- LTRA or theophylline
4. inhaled corticosteroideg.prednisolone (high dose) +/- LABA/LTRA/Theophylline
5. Refer to specialist management: oral corticosteroid(lowest possible dose) +/- inhaled corticosteroid*(lowest possible dose)
   ALWAYS CHECK INHALER TECHNIQUE AND ADHERANCE

• Antibiotics - if there is evidence of becterial infection

Refer to specialist if acute asthma =/> 2x in a year (12months)

Review at 4-8 weeks after adjusting treatment. Then, yearly when stable.

Question 7

Asthma: Pharmacology

Answer 7

• Beta-2 adrenergic receptor agonistsare bronchodilators. They act on adrenalin receptors to relax/dilate the bronchioles and reverse bronchoconstriction. They are used as relievers or rescue medication during acute worsening of asthma symptoms. Must monitor Serum potassiumas they cause increase cellular absorption of serum potassium -> hypokalaemia (K+ is needed for body cells, nerves and muscles to work properly) -> tachycardia and lactic acidosis (build up of lactic acid).
  
  • Short-acting beta-2 agonists(SABA), such assalbutamol, work quickly, but the effects last only a few hours.
  • Long-acting beta-2 agonists(LABA), such assalmeterol, are slower to act but last longer. Used with corticosterioids to prevent tolerance.
• Inhaled corticosteroids(ICS), such asbeclometasone, reduce the inflammation and reactivity of the airways. These are used asmaintenanceorpreventermedications to control symptoms long-term and are taken regularly, even when well.
• Maintenance and reliever therapy(MART) involves a combination inhaler containing aninhaled corticosteroidand afast and long-acting beta-agonist(e.g.,formoterol). This replaces all other inhalers, and the patient uses this single inhaler both regularly as apreventerand also as arelieverwhen they have symptoms.
• Long-acting muscarinic antagonists(LAMA), such astiotropium or ipatropium bromide, work by blockingparasympathetic ACh receptors . reversing bronchoconstriction.
• Leukotriene receptor antagonists(LTRA), such asmontelukast, work by blocking the effects ofleukotrienes produced by the immune system. It stopsinflammation,bronchoconstrictionandmucus secretionin the airways.
• Theophyllinedilates bronchioles and reduces inflammation. Must monitior serum theophylline as it has anarrow therapeutic windowand can be toxic in excess:
  
  • Toxic Effects incl.:
    
    • Vasodilation (hypotension)
    • Can contribute to pathophys long-term (hypoxia, ischaemia (hypoxic pulmonary vasoconstriction) or inflammation)
    • Cardiac muscle- arrhythmia
    • GI tract- anorexia, vomiting, nausea
    • CNS- sleep disturbances, tremor
• Magnesium sulphate - bronchodilator used in severe acute asthma

Question 8

Asthma: Treatment cont.

Answer 8

• Individual written asthma self-management plan
• Yearly asthma review when stable
• Yearly flu jab
• Regular exercise
• Avoid smoking (including passive smoke)
• Avoiding triggers where appropriate
• Occupational asthma…
• Oral steroids as rescue pack for acute asthma

Question 9

Acute Asthma: Management

Answer 9

Grading Acute Asthma

Moderateexacerbationfeatures:
- Peak flow 50 – 75% best or predicted

Severeexacerbationfeatures:
- Peak flow 33-50% best or predicted
- Respiratory rate above 25
- Heart rate above 110
- Unable to complete sentences

Life-threatening**exacerbationfeatures:
- Peak flow less than 33%
- Oxygen saturations less than 92%
- PaO2less than 8 kPa
- Becoming tired
- Confusion or agitation
- Silent Chest
- Haemodynamic instability (shock)

Management of Acute Asthma
Acute asthma is a medical emergency. Treatment decisions, particularlyintravenousaminophylline,salbutamolandmagnesium, should involve experienced seniors.

Mild exacerbationsmay be treated with:
- Inhaled beta-2 agonists(e.g., salbutamol) via aspacer - measure serum potassium levels
- Quadrupled doseof theirinhaled corticosteroid(for up to 2 weeks) or Oral steroids(prednisolone) if the higher ICS is inadequate
- Antibioticsonly if there is convincingevidence ofbacterialinfection
- Follow-upwithin 48 hours

Moderate exacerbationsmay additionally be treated with:
- Considerhospital admission
- Nebulisedbeta-2 agonists(e.g., salbutamol) - measure serum potassium levels
- Steroids(e.g., oral prednisolone or IV hydrocortisone)

Severe exacerbationsmay additionally be treated with: OSHITME
- Hospital admission
- O: Oxygento maintain sats 94-98%
- S: Salbutamol IV - measure serum potassium levels
- H: Hydrocortisone or prednisolone. steroids take a while to work so start as soon as possible.
- I: Ipratropium bromide nebulised
- T: theophylline IV or aminophylline
- M: IV magnesium sulphate - bronchodilator
- E: Escalate to senior/anaethetist and consider intubation and ventilation (BiPAP)

Life-threatening exacerbationsmay additionally be treated with:
- Admission to HDU or ICU
- Intubationandventilation (BiPAP)

Descision to intubate should be made as early as possible as it is very difficult to intubate with severe bronchoconstriction.