Perioperative management of the child with asthma.

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This educational review outlines the pathophysiology of asthma, key aspects of preoperative evaluation of children with asthma, and provides updates in asthma treatment from multinational guidelines, including recommendations for the treatment of bronchospasm under anaesthesia.

This review focuses on the ‘Th2’ or ‘atopic, aspirin exacerbated respiratory disease’ (AERD) endotype, as it is by far the most common in paediatric asthma, where sensitisation to aeroallergens results in CD4 activation and release of interleukins IL4, IL5 and IL13.

Preoperative evaluation:

Spirometry and peak expiratory flow rate (PEFR) cannot be reliably performed in children under 5 years, therefore history and examination findings may be more pragmatic in the perioperative setting.

Risk factors for perioperative respiratory adverse events (PRAEs) include age <5yrs, moderate to severe asthma, respiratory tract infection within last 4 weeks, previous exacerbations under GA, need for intubation and ventilation for an exacerbation. Anaesthetic/surgical risk factors include intubation (vs supraglottic airway or bag mask ventilation only), airway surgery, and prolonged operation. Additional components of preoperative evaluation should include frequency of symptoms, exercise limitation, frequency of short acting beta agonists or ‘reliever’ medication use, known triggers, recent exacerbations, and level of care required if hospitalised. The child should be examined for wheeze, increased work of breathing, and abnormal vital signs.

Stratification based on severity is recommended:

• Well controlled asthma (no need for reliever medication for last month, no exercise limitation, and symptom free): can proceed as a day case at a general or regional hospital
• Mild asthma (symptoms less than three times per week, and no limitation in activity): can proceed with elective cases as a day case at a general or regional hospital.
• Moderate asthma (daily or nightly symptoms, may have exercise limitation). Weighing risks vs benefits of elective surgery can be difficult. If the child is well, with a recent review by treating physician, and compliant with treatment, it is safe to proceed with elective cases.
• Severe asthma (persistent daily or nightly symptoms, requires high dose inhaled corticosteroids plus a second agent to achieve symptom control, or is uncontrolled despite therapy). Recommend review by respiratory physician to optimise control and plan for perioperative care, consider performing surgery in a centre with paediatric HDU or PICU facility.

Perioperative management recommendations:

• Ensure treatment compliance in the preceding month.
• Children on > 15mg/m² hydrocortisone equivalent for more than 1 month, are at risk of adrenal suppression, and perioperative steroid replacement should be considered.
• Administer short acting inhaled beta agonist via spacer or nebuliser preoperatively
• Ensure adequate depth of anaesthesia before instrumenting airway or painful stimuli
• Consider sevoflurane and ketamine use to promote bronchodilation (as well as magnesium)
• Consider choice of airway & bronchospasm risk: LMA < ETT
• Minimise histamine releasing drugs (e.g., synthetic opioids over morphine)

Management of severe bronchospasm under general anaesthesia

• Pharmacological agents:
  • First line: inhaled salbutamol via anaesthetic circuit
  • Deepen anaesthesia and consider changing to volatile if maintaining with TIVA
  • Second line: nebulised ipratropium, IV magnesium, IV salbutamol, hydrocortisone, and in extremis, IV adrenaline
  • Consider commencing infusions of salbutamol, aminophylline, adrenaline or ketamine
• Ventilation strategies are listed as suggestions without an in-depth discussion of supporting literature
  • Target oxygen saturation >90%, allow permissive hypercapnia with pH >7.2
  • Maintain full paralysis
  • Either pressure or volume control modes can be utilised- the authors recommend a mode that is most familiar to the treating clinician
  • Tidal volumes of 5-7 ml/kg
  • Target plateau pressure <30 cmH20, and PIP of <40 mmHg to avoid barotrauma
  • Consider low PEEP of 4-5 cmH2O
  • Increase expiratory time aiming I:E ratio 1:3-1:4
  • Monitor for breath stacking: ensure flow reaches baseline at end expiration, and that end tidal CO2 reaches a plateau
  • Refrain from manually decompressing the chest: can precipitate cardiac arrest

In summary, this review paper provides a refresher for clinicians in the risk stratification and perioperative management of children with asthma, based on international guidelines formed from available evidence and consensus expert opinion.

 

Reviewed by Dr Heather Patterson