Asthma Management

Management of Acute Severe Asthma (esp. of a child)

Note the child’s:

• Colour
• Position
• Level of Consciousness

Look specifically for/at:

• is the child fatigued?
• are they working hard to breathe? (in which case they will become fatigued if not already)
• count the respiratory rate
• number of words able to speak without stopping: i.e. words, phrases, or sentences
• air entry ± wheeze
• heart rate
• blood pressure ± pulsus paradoxus

Immediate interventions:

• Oxygen: aim for oxygen saturation > 94%
• 3 x q 20min salbutamol + ipratropium
• 1 mg/kg oral prednisone
• IV access 

Take a directed history:

• Determine the events leading to the episode
• recent and current treatment(s)
• previous history, including severity (ICU / intubation)
• allergies, h/o anaphylaxis, FHx atopy or asthma

Continuous nebulised salbutamol with 8L/min O2

• hydrocortisone 4 mg/kg
• 2/3 maintenance fluids: 0.9% Normal Saline 1L + 20 mmol KCl
• 50% magnesium sulphate: 2 mmol/mL
  • 0.2 mmol (0.1 mL) / kg solution over 20 min diluted with 0.9% saline at least 1:1 (max 8 mmol)
  • ± 0.12 mmol (0.06 mL) / kg per hour infusion 
• aminophylline
  • 5 mg / kg loading dose over 30 min, then
  • 0.9 mg / kg per hour infusion (< 9 years old) or 0.7 mg / kg per hours infusion (> 9 years old)
• salbutamol IV (adrenaline)
  • start infusion at lower end of 1-5 mcg / kg per min and titrate
    • draw up 50 mL of 5 mg / 5 mL salbutamol intravenous solution
    • weight (kg) x 0.06 mL per hour (1 mcg / kg per min) – max 40 kg
• NIV: CPAP
• intubation

Watch for:

• tachycardia
• arrhythmia: tachyarrhythmia, including SVT (esp. HR > 200)
• hypotension
• vomiting
• metabolic acidosis
• hypokalaemia: check serum K+ q 6-8H

Note: The benefit of intravenous magnesium sulphate in acute (severe) asthma in children has been demonstrated in two meta-analyses.

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Acute Management of Non-severe Asthma

Dyspnoea seen only with activity (i.e. PEF > 70%) is usually managed at home, as prompt relief is obtained with inhaled bronchodilators (± ICS).

• dyspnoea limits activity: PEF 40-70% – usually seen in office / ED
  • frequent SABAs + oral steroids
• dyspnoeic at rest: PEF < 40% – usually admitted
  • frequent SABAs + Ipratropium q 20 min (or cont. for 1 hour)
  • oral steroids
  • ± supplemental oxygen (Sats > 90%)
• unable to speak:
  • minimal / no relief from frequent inhaled SABAs
  • intravenous corticosteroids
  • supplemental Oxygen
  • ± magnesium sulfate
  • ± parenteral beta-agonists
  • ± CPAP
  • ± intubation

Longer-term Asthma Control

Base-line control of asthma is achieved in primary care, including treatment adjustments incorporating, if need be, new therapies, followed by treatment escalation to a respiratory physician, if required.

Regular assessment of symptoms is imperative. Afterward, don’t overlook non-pharmacological approaches to management. Then consider optimising adherence and technique. Finally, consider step-down when stable or, conversely, step-up and referral if difficulty stabilising.

Statistics

• 300 million people worldwide
• + 100 million within five years (2025)
• prevalence high in Australia (and NZ), where 1 in 9 have asthma
• GPs routinely overestimate  control achieved in patients
  • suspect sub-optimal control for 6% of their patients
  • compared to 32% of patients who feel they are uncontrolled

Practical Strategies: “Asthma Control”

1. Achieve control defined by symptoms, activity, reliever use, lung function.
2. Reduce future risk predicted by instability/worsening, exacerbations, loss of lung function, adverse medication effects.

• Well controlled with no preventer (40%): follow-up at least yearly
• Well controlled with good preventer adherence (15%): consider down-titration
• Uncontrolled despite good preventer adherence (20%): confirm adherence and check inhaler technique; treat comorbidities
• Under-treated (25%): start preventer or improve adherence

Recurring themes:

• Other diagnoses / complicating comorbidities:
  • COPD: if FEV1 bronchodilator response 400 mL or fully reversible, treat as asthma
  • allergic rhinitis
  • GORD
  • cardiac disease
• Poor adherence to inhaled corticosteroid (ICS) or poor inhaler technique: always check technique before step-up; only 10% people use their inhaler correctly
• Triggers
  • smoking: higher ICS doses may be needed
  • allergens
    • animal dander
    • mould
  • occupational exposures

Global Initiative for Asthma (GINA) Guidelines suggest a continuous cycle of assess, adjust, and review response.

Asthma Action Plan

1. usual asthma and allergen medicines
2. clear instructions on how to change medication
3. when and how to get medical care, including emergency situations

Tiotropium

• long-acting muscarinic antagonist (“anti-bronchoconstrictor”)
  • attach to M3-muscarinic receptors: most important for contraction of airway smooth muscle and for mucus secretion
  • block acetylcholine signalling: maintain airway in open position
• safe and effective add-on to ICS / LABA regimen
  • ↓ risk severe exacerbation
  • improved asthma control
  • improves lung function
• caution with
  • narrow-angle glaucoma
  • prostatic hyperplasia or bladder-outlet obstruction

In Australia, for PBS subsidy, need to be on medium-high dose LABA/ICS and an episode requiring oral corticosteroids in the last year.

Further, often specialist, testing:

• Pulmonary function tests
• Bronchial provocation
• blood / sputum eosinophil level
• IgE
• fractional exhaled nitric oxide (FeNO)

Remember that asthma is a heterogenous phenotype that might require specialist characterisation and for which biological therapies for allergic / atopic phenotypes with high levels TH2 immunity: mepolizumab; omalizumab.

• severe asthma with high IgE / eosinophil counts
• typically early onset
• atopic / allergic history
• It is for this group that corticosteroids are also most effective

Omalizumab is an anti-IgE monoclonal antibody given by fortnightly or monthly sci for > 12 years old with moderate-severe allergic asthma (raised IgE) not controlled on ICS.

Mepolizumab is an anti-IL5 monoclonal antibody given by monthly sci for > 12 year olds with severe, refractory eosinophilic asthma.

PBS restricts these biologicals to patients seeing a respiratory specialist for at least 12 months.

By contrast, non-atopic asthma (low TH2) is a neutrophilic inflammation typically adult-onset in obese smokers.

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References:

1. The Pediatric Emergency Medicine Resource. 5th Edn. AAP/ACEP. Burlington, MA: Jones & Bartlett, 2011.
2. Lee, Philip. “Asthma.” Lecture. Sydney General Practice Day  Aug 26, 2017.
3. Asthma in Neonates and Children. NETS.

Further Reading:

• Mepolizumab for asthma, Australian Prescriber
• National Asthma Council