Asthma Flashcards
Asthma Definition
A chronic, reversible, episodic respiratory condition caused by oedema, mucus plugging, and smooth muscle spasm of bronchioles. Characterised by SOB, wheeze and cough. Triggered by hypersensitivity of the bronchioles in response to allergen.
Early-phase Asthma Pathophysiology
- Allergen exposure triggers IgE receptors on mast cells, resulting in release of histamine and inflammatory mediations.
- Bronchoconstriction is therefore precipitated by histamine (H1 receptors) and ACh (cholinergic receptors) - further causing bronchial smooth muscle contraction.
- Oedema occurs due to increased permeability of bronchial capillaries, leading to bronchial oedema and mucus production.
- Gas trapping causes hyperinflation and increased intrathoracis pressure > decreased venus return due to collapse > decreased preload and CO = VQ mismatch = hyperaemia = respiratory acidosis and decreased cerebral perfusion.
Late-phase asthma pathophysiology
- Late phase is characterised by further bronchoconstriction, oedema and mucous plugging due to the recruitment of further inflammatory markers - basophils, eosinophils and neutrophils.
- These mediators cause damage to epithelium of the airway resulting in further exocytosis of mast cells and basophils, causing an acute airway hyper-responsiveness.
- Damage exposes to nerves which cause cough, increased mucus production and oedema.
- Further impairment of mucociliary escalator resulting in widespread mucous plugging (increased production, decreased clearance)
Asthma signs & symptoms
- Expiratory wheeze and/or inspiratory wheeze
- Chest tightness
- Decreases SpO2
- SOB
- Cough
- Prolonged expiratory phase
- Tachypnoea
- Tachycardia
- Hypercapnia
- Hypoxia
Why 1 min of apnoea in asthmatic arrest patients?
- Allow passive gas exchange and expiration air/gases
- Reduce hyperinflation and decrease intrathoracic pressure
High-risk asthmatic patients
- Initial moderate or severe / life threatening presentation
- Previous episode requiring intubation / ICU admission
- History of heart failure
- Bilateral crepitations on auscultation
- Pregnancy
- No improvement in PEFR and / or symptomatic post-treatment
- No previous diagnosis of asthma or airways disorder.
Asthma red flags
Dyspnoea
Cannot speak in sentences
SpO2 <94%
Increased RR
Increased WOB
Accessory muscle use
Silent chest
Worsening wheeze, cough or chest tightness
Reliever is not helping
Drowsy, confused or exhausted
Pale, clammy and/or cyanotic
Causes of cardiac arrest in asthmatics
- Mucous plugging and oedema preventing gas exchange
- Hyperinflation, increasing intrathoracic pressure
- Cardiac arrythmias due to hypoxia or electrolyte abnormality
- Tension Pneumothorax
Asthma management for adults: mild/moderate
- adult: Salbutamol 12 puffs Q20mins
- Ipratropium 8 puffs every 20mins MAX. 3
Asthma management for adults: Severe
- As mild/moderate by increase salbutamol frequency to 5-10 mins
- Neb if MDI not tolerated: 10mg salbutamol, then 5mg at 5min intervals; ipratoprium 500mcg every 5 mins for 3.
- Dexamethasone 8mg PO/IV/IM
- MgSO4
Asthma management for adults: Life-threatening
- First line: Adrenaline 500mcg every 5 mins
- Nebulised salbutamol and ipratropium
- NaCl up to 20mg/kg
- Dexamethasone
- MgSO4
Asthma management for adults: unconscious or loss of CO
- 1 min period of apnoea
- IPPV with 100% O2: ventilate 5-8/min to allow for prolonged expiratory phase.
Asthma management for paediatrics: Mild/moderate
- 1-6 years: salbutamol 6 puffs Q20mins
- > 6 years 12 puffs
Asthma management for paediatrics: Severe
- Salbutamol as Mild.moderate increasing frequency to Q5-10mins.
- Ipratropium: 1-6 years - 4 puffs every 20mins (max. 3); >6 years - 8 puffs
- Use neb if MDI unavilable
- Dexamethasone 600mcg/kg max. 8mg
Asthma management for paediatrics: life-threatening
- Adrenaline 10mcg.kg (max. 500mcg)
- Salbutamol and ipratropium nebs
- NaCl up to 20ml/kg
- Dexamethasone
