Acute wheeze (asthma) in children



Background

  • According to the WHO, asthma is the most common chronic disease in children
  • Clinically it manifests as recurrent episodes of wheezing, dyspnoea, chest tightness and cough
  • Episodes are associated with variable airflow obstruction that is usually reversible
  • Children < 12 months of age presenting with wheeze are likely to have bronchiolitis, which will not respond to bronchodilators. See bronchiolitis guideline.

Clinical

History

  • duration of symptoms
  • chronic treatment (relievers, preventers) and treatment used thus far during this acute presentation
  • trigger factors (including URTI, allergy, exercise)
  • pattern and course of previous acute episodes e.g. hospital and/or ICU admissions.
  • parental understanding of the treatment of acute episodes – what is their action plan?
  • presence of interval symptoms
  • family history of asthma or atopy.
  • Previous ICU admissions

NB Consider differential diagnosis of acute wheeze:

  • bronchiolitis: < 1yr typically
  • aspiration: especially if known swallowing disorder (neurological); history of associated vomiting
  • foreign body: typically presents with unilateral signs, history of sudden onset
  • anaphylaxis
  • heart failure

Examination

  • Most important parameters in the assessment of the severity of acute childhood asthma are general appearance (mental state) and work of breathing (accessory muscle use), as indicated in the table below
  • SaO2 and heart rate are less reliable additional features
  • Wheeze intensity is not reliable
  • Asymmetry and/or focal signs on auscultation are often found due to mucous plugging, but warrants consideration of foreign body or pneumothorax, or less likely, pneumonia

Investigations

  • Chest x-ray is typically not required and often delays other important acute treatment (discuss with registrar/consultant if considering). It can be considered after the acute management if focal signs persist – but be aware that patchy infiltrates may be caused by mucous plugging of airways and can be misinterpreted as consolidation
  • Bacterial infection is rare and antibiotics are rarely needed in acute asthma
  • Blood gases are rarely required in the assessment of acute asthma
  • In the severe or critical episode, a venous blood gas may be useful. A normal venous pCO2 should be interpreted with caution – the child may still be severely ill

Management

Severity Signs of Severity Management
Mild
  • Normal mental state
  • Subtle or no accessory muscle use/recession
  • Able to talk normally

Salbutamol by Metered Dose Inhaler (MDI)/spacer every 20 minutes x 3: 6 puffs if < 6 years old, 12 puffs if ≥6 years old.

  • Ensure device / technique appropriate
  • Good response - discharge on oral steroid and β2-agonist as needed
  • Poor response - treat as moderate

Oral prednisolone (1 mg/kg daily (max 40mg/day) for 3 days OR single dose oral dexamethasone 0.3mg/kg (max 12mg) – only if there is an on going need for salbutamol. Preschool children with mild wheeze will often not require steroids.

Provide written advice on what to do if symptoms worsen. Consider overall control and family’s knowledge. Arrange follow-up as appropriate.

Moderate
  • Normal mental state
  • Some accessory muscle use/recession
  • Tachycardia
  • Some limitation of ability to talk

Titrate oxygen to keep SpO2 ≥92%.

Salbutamol by MDI/spacer (6 puffs if < 6 years old, 12 puffs if ≥ 6 years old) every 20 minutes x 3; review 20 minutes after 3rd dose to decide on referral for admission or trial of stretching in the ED.

Oral prednisolone (1 mg/kg daily (max 40mg/day) for 3 days) OR single dose oral dexamethasone 0.3mg/kg (max 12mg).

Preschool children (<5 years old) in ‘moderate’ category, with good response to inhaled therapy, and who are fit for discharge may not require steroids. Discuss with senior emergency doctor if in doubt.

Consider discharge if well for 1 hour after last salbutamol dose.

Arrange home treatment and follow-up as above.

Severe
  • Agitated, distressed
  • Moderate-marked accessory muscle use/recession
  • Tachycardia
  • Marked limitation of ability to talk

Note: wheeze is a poor predictor of severity

Involve senior emergency doctor, consider ICU review.

Oxygen: note that NPO2 can be given simultaneously with MDI

If sats ≥92%, administer Salbutamol by MDI/spacer (6 puffs if < 6yrs old, 12 puffs if ≥ 6 years old) every 20 minutes x 3. If sats < 92%, administer salbutamol by nebuliser (2.5mg < 6yrs old, 5mg if ≥6yrs old). Evaluate response 20 minutes after the third dose.

Ipratropium by MDI/spacer 1 dose every 20 minutes x 3, (4puffs if < 6 years old, 8 puffs if ≥ 6 years old).

Oral prednisolone (1 mg/kg daily (max 40mg/day) for 3 days) OR single dose oral dexamethasone (0.3mg/kg (max 12mg)); if vomiting give IV hydrocortisone (4 mg/kg (max 160mg/dose)) every 6 hours.

Consider magnesium sulphate IV 50mg/kg: Magnesium sulphate 50% solution 0.1 ml/kg, diluted 1 in 5 with 0.9% Sodium Chloride and administered over 20 min). Cardiac monitoring is required.

Consider Aminophylline IV. Loading dose: 5mg/kg IV (maximum dose 500 mg) over 60 min. Cardiac monitoring is required. Unless markedly improved following loading dose, give continuous infusion (usually in ICU), or 6 hourly dosing (usually in ward).

Consider Adrenaline IMI 0.01mL/kg of 1:1000 (maximum 0.5mL) if there is a possibility of anaphylaxis or if the child is still not improving with above treatment. Dose can be repeated in 5 minutes.

Arrange admission after initial assessment for all these children.>/

Life Threatening
  • Confused/drowsy
  • Maximal accessory muscle use/recession
  • Poor respiratory effort (including bradypnoea)
  • Exhaustion
  • Silent chest
  • Cyanosis
  • Unable to talk
  • Pneumothorax

Call emergency consultant and ICU registrar/consultant to assess patient.

Titrate oxygen to SpO2 ≥92%.

Patient will require IV access. Magnesium, Aminophylline and Salbutamol must be given in separate lines.

Continuous nebulised salbutamol 10mg nebule undiluted.

Nebulised ipratropium 250mcg nebulised x 3 only.

Hydrocortisone 4 mg/kg (max 160mg/dose) IV 6-hourly.

Give bolus magnesium sulphate IV 50 mg/kg (Magnesium sulphate 50% solution 0.1 ml/kg, diluted 1 in 5 with 5% Dextrose or 0.9% Sodium Chloride and administered over 20 min).

Administer Aminophylline IV. Loading dose: 5 mg/kg IV (maximum dose 500 mg) over 60 min. Unless markedly improved following loading dose, give continuous infusion (usually in ICU), or 6 hourly dosing (usually in ward).

If poor response to IV aminophylline, consider IV Salbutamol. 5 microg/kg/min for one hour as a load, followed by 1-2 microg/kg/min.

Consider Adrenaline 0.01mL/kg of 1:1000 (maximum 0.5mL) intramuscular, into lateral thigh which should be repeated after 5 minutes if the child is not responding to treatment.

NOTE:

If persistent tachypnoea after salbutamol treatment without wheezing – the child may be salbutamol toxic. Venous blood gas is a useful indicator, which will show metabolic acidosis with high lactate. Treatment is to limit salbutamol and supportive therapy.

Also note hypokalaemia often complicates salbutamol treatment.


Admission

Admit to Hospital if:

  • Severe or critical episode
  • Moderate episode which fails to respond to Emergency Department treatment.
    • This is the commonest reason for admission
    • This generally means that the patient cannot stretch to longer than one hour between doses of salbutamol (either via spacer/MDI or nebuliser) after the intial treatment period has elapsed
  • Complicated episode (e.g. pneumothorax)
  • Previous episode that required ICU admission
  • Social reasons e.g. likely poor compliance with education measures aimed at reducing re-attendance/readmission

Admit to ICU if:

  • Impending respiratory failure (maximal accessory muscle use/recession, exhaustion, poor respiratory effort, cyanosis, silent chest)
  • Pneumothorax present
  • Requiring continuous nebulisers
  • Requiring salbutamol more frequently than every 20 minutes after 2 hours
  • Requiring salbutamol via spacer/MDI or nebuliser more frequently than hourly after 4 hours

Transition to ward care:

The weaning of salbutamol in the ED can be as follows:

  • Initial 3 doses 20 minutes apart
  • Review 20 minutes after 3rd dose
  • If patient improving then reassess and regularly administer further doses for increased work of breathing as required.

 Patients who are transferred from the ED to the ward should:

  • not require continuous nebulised salbutamol;
  • not require salbutamol more frequently than every 20 minutes after 2 hours;
  • not require salbutamol via spacer/MDI or nebuliser more frequently than hourly after 4 hours;
  • have a prescription for inhaled salbutamol prn 4hrly. Inhaled ipratropium prn 6hrly prescribed in severe cases.
  • have received an appropriate dose of steroid

Discharge checklist


References

  1. https://www.who.int/respiratory/asthma/en/

Content By: Dr Lizerie Jansen, Dr Rory O' Brien CUH 02/10/2019.