Asthma Flashcards
Grading Acute Asthma
Moderate
PEFR 50 – 75% predicted
Severe
PEFR 33-50% predicted
Resp rate >25
Heart rate >110
Unable to complete sentences
Life-threatening
PEFR <33%
Sats <92%
Becoming tired
No wheeze. This occurs when the airways are so tight that there is no air entry at all. This is ominously described as a “silent chest”.
Haemodynamic instability (i.e. shock)
Treatment Acute Asthma
As a junior doctor you should not underestimate the danger of acute asthma. Patients can deteriorate quickly and it can be life threatening. Generally don’t hesitate to keep adding treatment and escalate early to seniors and HDU / ICU if not improving or there are signs of severe asthma.
If asthma is severe treatment decisions such as aminophylline, IV salbutamol and IV magnesium are normally under senior guidance.
Moderate:
Nebulised beta-2 agonists (i.e. salbutamol 5mg repeated as often as required)
Nebulised ipratropium bromide
Steroids. Oral prednisolone or IV hydrocortisone. These are continued for 5 days
Antibiotics if there is convincing evidence of bacterial infection
Severe:
Oxygen if required to maintain sats 94-98%
Aminophylline infusion
Consider IV salbutamol
Life threatening:
IV magnesium sulphate infusion
Admission to HDU / ICU
Intubation in worst cases – however this decision should be made early because it is very difficult to intubate with severe bronchoconstriction
ABGs in asthma:
Initially patients will have a respiratory alkalosis as tachypnoea causes a drop in CO2. A normal pCO2 or hypoxia is a concerning sign as it means they are tiring and indicates life threatening asthma. A respiratory acidosis due to high CO2 is a very bad sign in asthma.
Monitoring
To monitor the response to treatment you can use:
Respiratory rate
Respiratory effort
Peak flow
Oxygen saturations
Chest auscultation
Additional Notes on Treatment
Monitor serum potassium when on salbutamol as it causes potassium to be absorbed from the blood into the cells. Salbutamol also causes tachycardia (fast heart rate).
Optimise asthma control after an acute attack. Discharge patients with an “asthma action plan” that provides them with a clear plan for everything they need to know about their asthma in one place. Consider prescribing a “rescue pack” or steroids for the person to initiate in the future if they have another exacerbation of asthma. NICE suggest referral to a respiratory specialist after 2 attacks in 12 month
Presentation suggesting Asthma?
Episodic symptoms
Diurnal variability. Typically worse at night.
Dry cough with wheeze and shortness of breath
A history of other atopic conditions such as eczema, hayfever and food allergies
Family history
Bilateral widespread “polyphonic” wheeze heard by a healthcare professional
Treating Asthma
BTS/Sign Guidelines on Diagnosis
High probability of asthma clinically: Try treatment
Intermediate probability of asthma: Perform spirometry with reversibility testing
Low probability of asthma: Consider referral and investigating for other causes
NICE Guidelines on Diagnosis
NICE recommend assessment and testing at a “diagnostic hub” to establish a diagnosis. They specifically advise not to make a diagnosis clinically and require testing:
First line investigations:
Fractional exhaled nitric oxide
Spirometry with bronchodilator reversibility
If there is diagnostic uncertainty after first line investigations these can be followed up with further testing:
Peak flow variability measured by keeping a diary of peak flow measurements several times per day for 2 to 4 weeks
Direct bronchial challenge test with histamine or methacholine
Long Term Management
There are key treatments for long term management of asthma:
Short acting beta 2 adrenergic receptor agonists, for example salbutamol. These work quickly but the effect only lasts for an hour or two. Adrenalin acts on the smooth muscles of the airways to cause relaxation. This results in dilatation of the bronchioles and improves the bronchoconstriction present in asthma. They are used as “reliever” or “rescue” medication during acute exacerbations of asthma when the airways are constricting.
Inhaled corticosteroids (ICS), for example beclometasone. These reduce the inflammation and reactivity of the airways. These are used as “maintenance” or “preventer” medications and are taken regularly even when well.
Long-acting beta 2 agonists (LABA), for example salmeterol. These work in the same way as short acting beta 2 agonists but have a much longer action.
Long-acting muscarinic antagonists (LAMA), for example tiotropium. These block the acetylcholine receptors. Acetylecholine receptors are stimulated by the parasympathetic nervous system and cause contraction of the bronchial smooth muscles. Blocking these receptors leads to bronchodilation.
Leukotriene receptor antagonists, for example montelukast. Leukotrienes are produced by the immune system and cause inflammation, bronchoconstriction and mucus secretion in the airways. Leukotriene receptor antagonists work by blocking the effects of leukotrienes.
Theophylline. This works by relaxing bronchial smooth muscle and reducing inflammation. Unfortunately it has a narrow therapeutic window and can be toxic in excess so monitoring plasma theophylline levels in the blood is required. This is done 5 days after starting treatment and 3 days after each dose changes.
Maintenance and Reliever Therapy (MART). This is a combination inhaler containing a low dose inhaled corticosteroid and a fast acting LABA. This replaces all other inhalers and the patient uses this single inhaler both regularly as a “preventer” and also as a “reliever” when they have symptoms.
Confusingly the new NICE guidelines are slightly different to the SIGN/BTS guidelines. The medications they recommend are the same but they differ slightly in the stepwise ladder of which medications to introduce at what point. Most importantly they both start with a short acting beta 2 agonist followed by a low dose inhaled corticosteroid. The next step is then either a leukotriene receptor antagonist or an inhaled LABA.
They principles of using the stepwise ladder are to:
Start at the most appropriate step for the severity of the symptoms
Review at regular intervals based on severity
Step up and down the ladder based on symptoms
Aim to achieve no symptoms or exacerbations on the lowest dose and number of treatments. This is often difficult in practice.
Always check inhaler technique and adherence at review
BTS/SIGN Stepwise Ladder (adapted from 2016 guidelines)
Add short-acting beta 2 agonist inhaler (e.g. salbutamol) as required for infrequent wheezy episodes.
Add a regular low dose corticosteroid inhaler.
Add LABA inhaler (e.g. salmeterol). Continue the LABA only if the patient has a good response.
Consider a trial of an oral leukotriene receptor antagonist (i.e. montelukast), oral beta 2 agonist (i.e. oral salbutamol), oral theophylline or an inhaled LAMA (i.e. tiotropium).
Titrate inhaled corticosteroid up to “high dose”. Combine additional treatments from step 4. Refer to specialist.
Add oral steroids at the lowest dose possible to achieve good control.
NICE Guidelines (adapted from 2017 guidelines)
Add short-acting beta 2 agonist inhaler (e.g. salbutamol) as required for infrequent wheezy episodes.
Add a regular low dose inhaled corticosteroid.
Add an oral leukotriene receptor antagonist (i.e. montelukast).
Add LABA inhaler (e.g. salmeterol). Continue the LABA only if the patient has a good response.
Consider changing to a maintenance and reliever therapy (MART) regime.
Increase the inhaled corticosteroid to a “moderate dose”.
Consider increasing the inhaled corticosteroid dose to “high dose” or oral theophylline or an inhaled LAMA (e.g. tiotropium).
Refer to a specialist.
Diagnosing Asthma in Kids
There is no gold standard test or diagnostic criteria for asthma. A diagnosis is made clinically based on a typical history and examination. Children are usually not diagnosed with asthma until they are at least 2 to 3 years old. When there is a low probability of asthma and the child is symptomatic, consider referral to a specialist for diagnosis.
When there is an intermediate or high probability of asthma, a trial of treatment can be implemented and if the treatment improves symptoms a diagnosis can be made.
There are investigations that can be used where there is an intermediate probability of asthma or diagnostic doubt:
Spirometry with reversibility testing (in children aged over 5 years)
Direct bronchial challenge test with histamine or methacholine
Fractional exhaled nitric oxide (FeNO)
Peak flow variability measured by keeping a diary of peak flow measurements several times a day for 2 to 4 weeks
Treating Asthma in Kids
Medical Therapy in Under 5 Years
Start a short-acting beta-2 agonist inhaler (e.g. salbutamol) as required
Add a low dose corticosteroid inhaler or a leukotriene antagonist (i.e. oral montelukast)
Add the other option from step 2.
Refer to a specialist.
Medical Therapy Aged 5 – 12 Years
Start a short-acting beta-2 agonist inhaler (e.g. salbutamol) as required
Add a regular low dose corticosteroid inhaler
Add a long-acting beta-2 agonist inhaler (e.g. salmeterol). Continue salmeterol only if the patient has a good response.
Titrate up the corticosteroid inhaler to a medium dose. Consider adding:
Oral leukotriene receptor antagonist (e.g. montelukast)
Oral theophylline
Increase the dose of the inhaled corticosteroid to a high dose.
Referral to a specialist. They may require daily oral steroids.
Medical Therapy Aged Over 12 Years (Same as Adults)
Start a short-acting beta 2 agonist inhaler (e.g. salbutamol) as required
Add a regular low dose corticosteroid inhaler
Add a long-acting beta-2 agonist inhaler (e.g. salmeterol). Continue salmeterol only if the patient has a good response.
Titrate up the corticosteroid inhaler to a medium dose. Consider a trial of an oral leukotriene receptor antagonist (i.e. montelukast), oral theophylline or an inhaled LAMA (i.e. tiotropium).
Titrate the inhaled corticosteroid up to a high dose. Combine additional treatments from step 4, including the option of an oral beta 2 agonist (i.e. oral salbutamol). Refer to specialist.
Add oral steroids at the lowest dose possible to achieve good control under specialist guidance.
Inhaled Corticosteroids in Children
A potential exam scenario is discussing inhaled steroids with a parent that is worried about potential side effects. A common question is whether they slow growth. There is evidence that inhaled steroids can slightly reduce growth velocity and can cause a small reduction in final adult height of up to 1cm when used long term (for more than 12 months). This effect was dose-dependent, meaning it was less of a problem with smaller doses.
It is worth putting this in context for the parent by explaining that these are effective medications that work to prevent poorly controlled asthma and asthma attacks that could lead to higher doses of oral steroids being given. Poorly controlled asthma can lead to a more significant impact on growth and development. The child will also have regular asthma reviews to ensure they are growing well and on the minimal dose required to effectively control symptoms.
