Case 2 - Asthma - Progress Test Revision Flashcards
What type of reaction is asthma?
Type 1 hypersensitivity
What immune cell is over active in asthma?
IgE
Risk factors for asthma
Personal / family history of atopy. Antenatal factors: maternal smoking, viral infection during preganacy (especially RSV). Low birth weight. Not being breastfed. Maternal smoking around child. Exposure to high concentrations of allergens. Air pollution. Hygiene hypothesis.
Related IgE conditions
Atopic dermatitis (eczema). Allergic rhinitis (hay fever)
What medication are some patients with asthma sensitive to?
Aspirin
What are some examples of occupational triggers for asthma?
Isocyanates (eg. spray painting, foam moulding using adhesives)
Flour
What time of day is an asthmatic cough often worst?
Night
What are the signs of asthma
Expiratory wheeze on auscultation.
Reduced PEFR.
Spirometry results in asthma
FEV1 = significantly reduced FVC = normal FEV1/FVC = < 70%
What other tests can be used to diagnose asthma?
Fractional exhaled nitric oxide
shows level of inflammation
What is the 1st line medication for asthma?
SABA (eg. salbutamol)
What are side effects of a SABA?
Tremor
2nd line medication for asthma?
SABA + ICS (eg. beclamethasone, dipropionate, fluticason, propionate)
What are side effects of ICS?
Oral candidiasis
Stunted growth in children
4th line medication for asthma?
SABA + ICS + LABA (eg. salmeterol) +/- LTRA
3rd line medication for asthma?
SABA + ICS + Leukotriene receptor antagonist (eg. monteleukast) PO
What medications are in a MART inhaler?
ICS + LABA
5th line medication for asthma
SABA +/- LTRA + MART
What is a positive FeNO result for asthma?
> 40 parts per billion
What is a postive spirometry result for asthma?
< 70%
obstructive
What is a positive reversibility testing result for asthma?
Improvement in FEV1 of >= 12%
+
Increase in volume of >= 200ml
What is classified as moderate acute asthma?
PEFR 50-75% best or predicted
Speech normal
RR < 25 / min
Pulse < 110 bpm
What is classified as severe acute asthma?
PEFR 33-50% best or predicted
Can’t complete sentences
RR > 25 / min
Pulse > 110 bpm
What is classified as life-threatening asthma?
PEFR < 33% best or predicted
O2 sats < 92%
Normal pCO2 (exhaustion)
Silent chest, cyanosis or feeble respiratory effort
Bradycardia, dysrhythmia or hypotension
Exhaustion, confusion or coma
Who should be admitted to hospital in acute asthma?
All patients with life-threatening asthma
Patients with severe asthma who don’t respond to initial treatment
Patients with a previous near fatal attack
Pregnant patients
An attack in patients on oral corticosteroids
Patients presenting at night
What is the management of acute asthma?
O2 - 15L non-rebreathe
SABA (eg. salbutamol / terbutaline)
Oral prednisolone 40-50mg - for at least 5 days or until recovered
Ipratropium bromide
IV magnesium sulphate
IV aminophylline (requires senior consultation)
Referal to ITU/HDU for intubation and ventilation / ECMO
What is the criteria for discharge after acute asthma?
Stable on discharge medication for 12 - 24 hrs
Inhaler technique checked and recorded
PEF > 75% best or predicted
What are the stages of asthma pathogenesis?
- Sensitisation
- Early phase reaction
- Late phase reaction
What happens during the sensitisation stage of asthma pathogenesis?
- Exposure to inhaled allergen.
- Stimulates induction of Th2 cells.
- Th2 cells secrete cytokines and stimulate B cells to produce IgE.
- The cytokines induce IL-4 (which increases IgE production), IL-5 (which activates eosinophils) and IL-3 (which activates mucus secretion).
- IgE coats mast cells and repeated allergen exposure triggers mast cells to release granule contents and produce cytokines
What is involved in the early phase reaction of asthma?
- Bronchoconstriction.
- Increased mucus production.
- Variable degrees of vasodilation with increased vascular permeability.
What is involved in the late phase reaction in asthma
- Inflammation.
- Chemokine release from mast cells, epithelial cells and T cells.
- Recruitment of leucocytes (especially eosinophils, neutrophils and T cells).
What enzyme does aspirin block, causing it to be a trigger in asthma?
Cyclo-oxygenase
reducing production of prostaglandins
What is the pharmacology of SABA / LABA
Agonists of B2 adenoceptors on bronchiole smooth muscle - causing relaxation
What is the pharmacology of theophylline?
- Phosphodiesterase (PDE) inhibitor (triggers activation of PKA and muscle relaxation).
- Adenosine receptor antagonist.
What is the pharmacology of ipratropium?
- Muscarinic receptor antagonist.
muscarinic receptors are triggered in asthma by binding of ACh, causing smooth muscle contraction
What is the pharmacology of monteleukast?
- Leukotriene receptor antagonist.
- Prevents activation of the leukotriene receptor (which causes broncoconstriction) and promotes production of prostaglandins (which cause bronchodilation).
- Act at cysteinyl-leukotriene receptors on bronchiole smooth muscle cells preventing action of LTC4 and LTD4 (which cause bronchial spasm and stimulate mucus secretion)
What is the pharmacology of glucocorticoids?
Reduce production of cytokines, spasmogens (LTC4 and LTD4) and leucocyte chemotaxins (LTB4, PAF).
- Hence reduced bronchospasm and recruitment and activation of inflammatory cells
What receptors do glucocorticoids bind to?
GR alpha and GR beta
Causing induction of lipocortin and repression of IL-3
