Asthma Flashcards
Triggers
- cold air
- dust mites
- pollen/animal fur/dust mites
- smoke/fumes/pollution
- NSAIDs
- emotion e.g. stress/laughter
Pathology of asthma
immune condition mediated by IgE
IgE formed in response to a trigger.
Re-exposure to the allergen casues this specific IgE on mast cells, causing an inflammatory response:
-Histamine, prostaglandins, leukotrienes and eosinophils infiltrate the airway
-goblet cells over-produce mucous
-T lymphocytes produce cytokines that potentiates the inflammatory response
-This cascade causes bronchospasm - hyper-responsive smooth muscle on airway to narrow
Diagnosis of asthma
- No single test can diagnose asthma
- Combination of history, examination, tests to access the probability of asthma
- Diagnosis is through lung function testing and reversibility tests with either a SABA or an corticosteroid
Lung function tests to help diagnose asthma
-FVC
-FEV1
-FEV1:FVC ratio
-PEFR
FeNo
Define FVC
Forced vital capacity
Total volume expelled by the lungs
Define FEV1
Forced expiratory volume exhaled in first second of FVC
FEV1:FVC ratio normal values
improvement?
Normal 0.7
Below this indicates obstruction
Obstruction is reversible in asthmatic patients whom should see an increase of 400ml to lung capacity after taking salbutamol
PEFR
Peak expiratory flow rate
Done via peak flow meter
Maximum rate of airflow which can be achieved during a sudden forced expiration from a position of full inspiration
What do you do with the spirometry results?
Compare against predicted values for those patients that took it
Based on: age, height, race and sex
Uncontrolled asthma has what spirometry test results?
What happens after administration of salbuatmol?
Decrease if PEF and FEV1 in uncontrolled asthma
400mL increase in lung capacity after salbutamol administration
FeNO
Functional exhaled nitric oxide
indicates airway inflammation
elevated levels in asthma patients
Other non-spirometry tests
Blood eosinophils - inflammation
allergies
IgE levels
Presentation of asthma
wheezing
shortness of breath (dysponea
coughing - particularly at night and on waking
triggers from allergens
if severe - cyanosis, drowsiness, difficulty speaking full sentences
aims of asthma treatment
- control symptoms, including nocturnal and exercise-induced exacerbations
- Reduce reliance on rescue therapy
- Prevent exacerbations
- Achieve best possible lung function: FEV1 and/or PEF >80% predicted or best
- minimising side effects of medication
“Control” of asthma is defined as
- no daytime symptoms
- no nighttime symptoms
- no need for rescue medication
- no limitations on activity, including exercise
- no exacerbations
- normal lung function: FEV1 and/or PEF >80% predicted or best
- minimal side effects of treatment
Non-pharmacological management of asthma
- Avoiding triggers
- stop smoking
- lose weight if obese
- avoid exercise in cold air
- minimise occupational stimuli
- avoid NSAIDs and Beta-blockers (including eye drops)
- Hollistic remedies (immunotherapy, Buteytco breathing technique)
- Breast feeding
- -air ionisers
Treatment of chronic ashtma
- inhaled (with spacer/nebuliser) and oral routes of administration
- this makes side effects and ADRs more common due to the route being more systemic
Reliever
SABA e.g. salbutamol
produces quick symptomatic relief
Normally PRN
Preventer
Corticosteroids i.e. beclomethasone
Act on underlying inflammation
Usually PRN
Controller
:LABA e.g. salmeterol
Slow onset, long-acting, usually BD
Nebulisers
Vaporise aqueous solution of drug (normally salbutamol or ipratropium) to mist for inhalation through a mask or mouthpiece
They offer high dose delivery and are particularly useful in acte or chronic/severe asthma as
co-ordination not needed
Often used in hospitals
B2-agonists
Caause smooth muscle relaxation and enhance mucociliary clearance
- SABA
- LABA
- 3rd line controllers
SABAs
2 examples
onset and duration
Salbutamol and terbutaline
Onset 1-5minutes
Duration 4-6 hours
1st line relievers offer quick symptomatic relief
LABAs
2 examples
onset and duration
Salmeterol
- onset 10-20 minutes
- duration 12hours
Formoterol
-onset 1-3 minutes
duration 12 hours
B2 agonists ADRS
- fine tremor
- nervous tension
- headache
- peripheral vasodilation
- tachycardia
- hypokalaemia
Corticosteroids
2nd line preventers
Anti-inflammatory reducing bronchial hyper-response
ICS
3 examples
Inhaled corticosteroids Beclomethasone Budesonide Ciclesonide Available in combination with LABA ICS are classed as either low, medium or high doses
Oral corticosteroids
Prenisolone
Usually 40-50mg for 5 days for acute attacks
40-50mg =minimum effective dose in step 5
IV corticosteroid
Hydrocortisone
used in acute severe situations
suppresses inflammatory processes
When are corticosteroids indicated?
- exacerbation of asthma in last 2 years
- using inhaled B2 agnoist >3times/week
- symptomatic >3times/week
- waking one night a week due to symptoms
Inahled corticocosteroid ADRs
and solutions
-hoarseness or dysphonia (difficulty speaking)
if this happens, use spacer/dry powder
- oral candidiasis -rinse mouth after use or use spacer
- adrenal suppression - only in sustained doses >1500mcg Beclomethasone daily
Oral corticosteroid ADRs
-hypertension
-osteoporosis
-skin thinning
-hyperglycaemia
-adrenal suppression
-moon face
-acne
which is why for oral corticosteroids, we use the lowest dose that will control symptoms for the shortest time possible
Leukotriene antagonists
examples
- 3rd/4th line controller/preventer
- oral montelukast and zafirlukast
- antagonise bronchoconstriction, airway oedema and mucous production
ADRs for leukotriene antagonists
- abdominal pain
- headache
- thirst
- rash
- sleep disturbances/CNS effects
Cromones
Necocromil - preventer in 5-12 year olds
-mast cell stabilisers, inhibits mediator (histamine) release from mast cells
Cromones ADRs
- nausea and vomiting
- bitter taste
- dispepsia
Immunosuppressants
-Methotrexate
-ciclosporin
-gold
specialist use - used rarely
Methylxanthines - how they work
Think INTERACTIONS and ADRs!
phosphodiesterase inhibitors that inhibit leukotriene synthesis and therefore inhibit inflammation and bronchoconstriction
3rd/4th line controller/preventer therapy
Methylxanthine examples
- oral: theophylline
- IV/oral - aminophylline (salt of theophylline)
- Narrow therapeutic index
- SR preparations available to give predictable effect
- Brand MUST remain constant
Therapeutic range for methylxanthines
10-20mg/L
Side effects of methylxanthines dependent on plasma concentrations
- <20mg/L - nausea, diarrhoea, nervousness, headache
- > 20mg/L vomiting, insomnia, arrhythmias
- > 35mg/L - hyperglycaemi, arrhythmias, convulsions, death
Methylxanthine clearance affected by
CYP450 metabolism
- CCF (congestive heart failure)
- liver disease
- obesity
How to work out methylxanthine dose
by IBW (ideal body weight)
Methylxanthine interactions
1) enzyme inhibitors - these interactions can lead to toxicity
e. g.
- cimetidine
- erythromycin
- allopurinol
- ciprofloxacin
2) enzyme induction - these interactions can lead to sub-therapeutic doses
e. g.
- carbamazepine
- rifampicin
- phenytoin
- smoking
- alcohol
Anti IgE monoclonal antibodies
-Omalizumab
inhibits binding of IgE to mast cell receptors, therefore preventing inflammatory response to triggers
-licensed as add-on therapy in adults and children>12yrs for severe, persistent asthma
-S/C injection every 2-4 weeks
-only initiated by specialist centres
-patients must fulfil specific NICE criteria
-discontinue after 16 weeks if inadequate response (4-8 injections)
Outline the BTS/SIGN guidelines for adult management of acute+severe asthma
Patients should be reviewed every 3-6 months with a view of stepping down treatment
Steps
If asthma suspected, give SABA PRN
1) Monitored initiation of low dose ICS
↓
2) Add LABA (LABA+low dose ICS as combo inhaler)
↓
3)Additional add on therapies
-No response to LABA→stop LABA, consider ↑ICS dose
-Benefit from LABA but control still bad→continue LABA, ↑ICS to medium dose OR Continue LABA and ICS and consider a trial of a LTRA, SR Theophylline or LAMA
↓
4) High dose therapies
Refer to specialist care
Consider trials of:
-↑ICS up to high dose
-Adding on a 4th drug e.g. LTRA, SR theophylline, B2-agonist tablet, LAMA
↓
5) Continuous or frequent use of oral steroids
-refer to specialist care
-use daily steroid tablet in the lowest dose providing adequate control
-Maintain high dose ICS
-consider other treatments to minimise use of steroid
tablets
NB- SABA PRN is on ALL steps
Outline the management of chronic and acute asthma in children
Asthma suspected - consider very low dose→low dose ICS
1) Infrequent, short-lived wheeze. Asthma diagnosed
Regular preventer - very low (paediatric) dose ICS or LTRA <5 years
↓
2) continue v.low dose ICS plus
-children > or equal to 5yrs - add inhaled LABA
-children<5yrs- add LTRA
↓
3) Additional add-on therapies:
-no response to LABA→stop LABA and increase dose of ICS to low dose
-if benefit from LABA but still inadequate control, continue LABA and ↑ICS to low dose
-If benefit from LABA but control still inadequate, continue LABA and consider trial of a LTRA
↓
4) High dose therapies
-refer patient to specialist care
consider trials of:
-↑ICS to medium dose
-Addition of a 4th drug - SR theophylline
↓
5) Continuous or frequent use of inhaled steroids
-refer to specialist care
-use daily steroid tablet in the lowest dose providing adequate control
-maintain medium dose ICS
-consider use of other treatments to minimise use of steroid tablets
General advice for acute asthma in adults
- do not underestimate risk of death
- emergency admissions are avoidable
- patients who die have well-recognised risk factors which can be modified
- PEF<50% - severe
- PEF <33% - life-threatening
- RR>25/min
- HR>110/min
- O2 saturation <92%
Severe/life threatening exacerbations present with what symptoms?
- cyanosis
- difficulty speaking
- unconciousness
- tachycardia
- severe dysponea
If an asthma patient requires hospitalisation due to an asthma attack, what do you do?
immediate prescription
- oxygen at highest possible concentration 40-60% aiming for arterial oxygen saturation of 94-98%
- B2-agonist nebulised - 5mg QDS or multiple doses (2-10 puffs of sabutamol 100mcg at 10-20 minute intervals via spacer, depending on severity)
- corticosteroid: prednisolone 40-50mg oral at least 5 days OR IV hydrocortisone every 6 hours (hold ICS)
- Consider:
- Ipratropium nebules 500mcg 4-6 hourly
- single dose IV magnesium sulphate if PEF<50%
- IV theophylline/IV salbutamol
Magnesium sulphate
smooth muscle relaxant, T cell and mast cell stabiliser
Monitoring requirements if you’ve just admitted someone having an asthma attack
- PEF
- O2 saturation (aim 94-98%)
- arterial blood gases
- HR/RR - tachycardia/ponea
- CRP
- WCC if infection is suspected
- Theophylline levels (if continued >24h)
- serum K+ (nebulised SABA)
- glucose
- hydration
- Blood pH~7.4 (check for risk of acidosis)
When do you refer an asthma patient who is having an asthma attack to ITU?
- deteriorating PEF
- persistent hypoxia
- exhaustion, drowsiness
- coma, respiratory arrest
During hospitalisation, after attack is dealt with
- IV→nebuliser→inhaler
- oral steroid 40mg/50mg for 5 days at least, depending on severity
- restart steroid inhaler
- write and meet discharge criteria
- make action plan
- inhaler technique education
