Asthma Flashcards
Briefly describe the pathophysiology of asthma
(Reversible) narrowing of the airway due to:
- Smooth muscle contraction (bronchoconstriction)
- Mucosal inflammation
- Increased mucus production
Describe the clinical features of asthma (in terms of the symptoms and their pattern)
Symptoms:
- Cough (dry)
- Wheeze
- SOB
Pattern:
- Episodic
- Diurnal variation
Asthma is associated with with which other conditions?
Eczema and hayfever (atopic triad)
Describe some of the typical asthma triggers
NICE guidelines:
- Exercise
- Infection
- Exposure to cold air or allergens (e.g. dust/pollen)
Which classes of drugs may be contraindicated in asthmatic patients?
- NSAIDs
- Beta blockers
Which investigations are recommended by NICE for diagnosis of asthma?
First line:
- Fractional exhaled nitric oxide (FENO)
- Spirometry (with bronchodilator reversibility)
If there is still diagnostic uncertainty, these tests can be followed up with:
- Peak flow variability (diary)
- Direct bronchial challenge test (with histamine or metacholine)
Describe the first three steps in the pharmacological management of asthma (according to NICE guidelines)
- SABA, e.g. salbutamol
- Low dose ICS, e.g. beclomethasone
- LTRA, e.g. montelukast
Which class of drug does salbutamol belong to?
Describe the mechanism of action
Short-acting beta-2 agonist (SABA)
Activation of beta-2 receptors in airways causes smooth muscle relaxation and airway dilatation (short duration of action)
Which class of drug does salmeterol belong to?
Describe the mechanism of action
Long-acting beta-2 agonist (LABA)
Activation of beta-2 receptors in airways causes smooth muscle relaxation and airway dilatation (long duration of action)
Which class of drug does beclomethasone belong to?
Describe the mechanism of action
Inhaled corticosteroids (ICS)
Reduce inflammation and reactivity of the airways
Which class of drug does montelukast belong to?
Describe the mechanism of action
Leukotriene receptor antagonist (LTRA)
Leukotrienes are produced by the immune system and cause inflammation, bronchoconstriction and mucus production. LTRAs block the effects of leukotrienes.
Describe the mechanism of action of theophylline
What is important to remember about theophylline?
Relaxes bronchial smooth muscle and reduces inflammation
IMPORTANT: theophylline has a narrow therapeutic window and requires plasma level monitoring
What is MART?
MART stands for Maintenance and Reliever Therapy
This is a combination inhaler containing both an ICS and a fast-acting LABA - this replaces all other inhalers and the patient uses this inhaler as both a “preventer” and a “reliever”
Describe the conservative management of asthma
- Smoking cessation
- Avoid allergens, e.g. dust/pollen
Describe the classification of acute asthma exacerbation (NICE guidelines)
- Moderate
- Severe
- Life threatening
What are the criteria for a moderate asthma exacerbation?
All of the following:
- Reduced PEFR (50-75% of best/predicted)
- Normal speech
- No features of severe or life threatening exacerbation
What are the criteria for an acute severe asthma exacerbation?
One of the following:
- Reduced PEFR (33-50% of best/predicted)
- Tachypnoea
- Tachycardia
- Inability to complete sentence in one breath, or use of accessory muscles of respiration
- Reduced sats (but still >92%)
What are the criteria for a life threatening asthma exacerbation?
One of the following:
- Reduced PEFR (< 33% of best/predicted)
- Oxygen sats < 92%
- Altered consciousness/confusion
- Exhaustion
- Cyanosis
- Silent chest
Describe the initial management of an acute asthma exacerbation
ABCDE approach
OSHITME:
- Oxygen
- Salbutamol (nebs)
- Hydrocortisone
- Ipratropium (nebs)
- Theophylline
- Magnesium sulfate
- Early senior involvement
What may you discover on an ABG in a patient having an acute asthma exacerbation?
- Initially, patients may have a respiratory alkalosis (as tachypnoea means blowing off more CO2)
- Hypoxia and normal CO2 are worrying signs as these suggest the patient is tiring
- High CO2 (and therefore respiratory acidosis) is a VERY worrying sign
When giving back-to-back salbutamol, which side effects should you be wary of?
- Hypokalaemia
- Tachycardia
Describe the algorithm for management of hypokalaemia
If serum potassium 3.0-3.5:
- Oral replacement (potassium chloride, also known as Sando-K)
If serum potassium 2.5-3.0:
- Symptoms? Existing cardiac disease? ECG changes?
- If no to above, give oral replacement
- If yes to above, give IV replacement (see below)
If serum potassium < 2.5:
- IV replacement (potassium chloride)
When giving IV potassium replacement, what is the maximum:
a) concentration of infusion
b) rate of infusion
a) 40 mmol/L
b) 10 mmol/hour
What is the normal serum potassium level?
3.5 - 5.0
