Acute asthma

PIC Endorsed

Key points

If unsure if anaphylaxis or asthma, treat as anaphylaxis. Treatment of both is critical
Children <12 months of age presenting with wheeze are likely to have bronchiolitis
Preschoolers should only be given steroids for wheeze that is bronchodilator responsive and requires admission

Background

Asthma is a chronic inflammatory disease of the airways characterised by reversible airways obstruction and bronchospasm
Exacerbations in children are often precipitated by a viral infection

Assessment

History

Duration and nature of symptoms
Treatments used (relievers, preventers), treatment adherence and effectiveness
Trigger factors (including upper respiratory tract infection, passive smoking, exercise, cold air, aero-allergen exposure). Sudden onset of symptoms after insect sting or ingestion of food/medication may suggest anaphylaxis, and not just asthma
Pattern and course of previous episodes (eg frequency, utilisation of health services, need for hospitalisation, IV treatment or ICU admission)
Parental understanding of how to provide asthma treatments via metered dose inhaler (MDI) +/- spacer, the presence and use of an asthma action plan
Presence of interval symptoms, school attendance and performance, participation in physical activity (see Long term asthma control in Additional notes below)

Risk factors for severe disease include

Previous ICU admission
Poor adherence to asthma treatment
Poor control (significant interval symptoms)
Past history of anaphylaxis

Examination

Wheeze is not a good marker of severity
The best measures of severity are general appearance, mental state and work of breathing (accessory muscle use, recession)
Wheeze intensity, pulsus paradoxus, and peak expiratory flow rate are NOT reliable. A silent chest with no wheeze may herald imminent respiratory collapse
Initial SpO₂ in air, heart rate and ability to talk are helpful but less reliable additional features
Tachycardia can be a sign of severity but is also a side effect of beta agonists such as salbutamol
Asymmetry on auscultation is often found due to mucus plugging, but persistent asymmetry may indicate other causes such as inhaled foreign body or pneumothorax

Management

Investigation

Chest x-ray is not required in asthma, but persistent asymmetry may indicate other causes such as foreign body. Also consider in critical asthma or severe asthma that does not respond to initial treatment

Bloods are rarely performed

Blood gases are distressing and can cause a child with respiratory compromise to deteriorate further. They are not usually required and the child's clinical state is more important in guiding treatment
Electrolytes for potassium levels may be indicated when there has been prolonged or frequent salbutamol use. Hypokalaemia rapidly corrects when salbutamol dosing reduces (see Other management considerations listed below)

Spirometry is not usually required in the assessment of acute asthma in children. It cannot be reliably performed in children under 6 years old

Treatment

Children with respiratory distress should have minimal handling

Severity	Signs of severity	Management
Mild	Normal mental state Subtle or no increased work of breathing Able to talk normally	Salbutamol by MDI/spacer - give one dose (see dosing below) and review after 20 mins. Ensure device / technique appropriate. Nebulised salbutamol (5 mg) may be considered in children with severe asthma who cannot coordinate MDI use Good response: Discharge on short acting B2-agonist as needed Provide an Asthma Action Plan (see Resources section below). Consider overall control and family's knowledge. Arrange follow-up as appropriate Poor response: Treat as Moderate Consider oral prednisolone (see below)
Moderate	Normal mental state Some increased work of breathing Tachycardia Some limitation of ability to talk	Oxygen (humidified) if SpO₂ persistently <90% Ongoing need for oxygen should be reassessed regularly Oxygen may be required for low saturations. DO NOT give oxygen for wheeze or increased work of breathing. (See Additional notes: SpO₂) Salbutamol by MDI/spacer - 1 dose every 20 min for 1 hr; review 10-20 min after 3rd dose to decide on timing of next dose Ipratropium by MDI/spacer - 1 dose every 20 min for 1 hr only Consider oral prednisolone (see below)
Severe	Agitated/distressed Moderate-marked increased work of breathing, accessory muscle use/recession Tachycardia Marked limitation of ability to talk Note: wheeze is a poor predictor of severity Other signs of Anaphylaxis	Involve senior staff Oxygen (humidified) as above Salbutamol by MDI/spacer - 1 dose (see below) every 20 min for 1 hr; review ongoing requirements 10-20 min after 3rd dose. If improving, reduce frequency. If no change, continue 20 minutely Nebulised salbutamol (5 mg doses) may be considered in children requiring oxygen If deteriorating at any stage, treat as critical Ipratropium by MDI/spacer - 1 dose every 20 minutes for 1 hour only Oral prednisolone (see below) If vomiting, give IV corticosteroid Methylprednisolone 1 mg/kg (max 60 mg) 6 hourly Hydrocortisone 4 mg/kg (max 100 mg) 6 hourly If poor response to the above treatment give: *Magnesium sulfate 50% (500 mg/mL = 2 mmol/mL)** Dilute to 0.8 mmol/mL (by adding 1.5 mL of sodium chloride 0.9% to each 1 mL of magnesium sulfate) for intravenous administration 0.2 mmol/kg over 20 mins (maximum 8 mmol) If going to ICU, this may be continued with 0.12 mmol/kg/hour by infusion Magnesium sulfate 49.3% (493 mg/mL) is used in some areas Be careful with dosage, volumes and concentrations. See Additional notes below Aminophylline* Loading dose 1-18 years: 10mg/kg (maximum 500mg) over 30-60 minutes Unless markedly improved following loading dose, give continuous infusion (usually in ICU), or 6 hourly dosing (usually in ward) Consider Adrenaline 10 microg/kg or 0.01 mL/kg of 1:1000 (maximum 0.5 mL) IM, into lateral thigh which should be repeated after 5 min if the child is not improving Arrange admission after initial assessment
Critical	Confused/drowsy Maximal work of breathing, accessory muscle use/recession Exhaustion Marked tachycardia Unable to talk SILENT CHEST: wheeze may be absent if there is poor air entry Other signs of Anaphylaxis	Involve senior staff and consider transfer to an appropriate children's facility/PICU Oxygen (humidified) Continuous nebulised salbutamol: Place 2 nebules into nebuliser chamber and give via continuous nebulisation. 6 months – 6 years, use 2.5 mg nebules ≥6 years, use 5 mg nebules Monitor for hypokalaemia and toxicity as discussed below Nebulised ipratropium added to salbutamol, every 20 minutes for 3 doses only <6 years old: 250 microg ≥6 years old: 500 microg Methylprednisolone 1 mg/kg (max 60 mg) IV 6 hourly Magnesium sulfate as above Aminophylline as above May also consider IV salbutamol. Limited evidence for benefit. 5-15 microg/kg (max 300 microg) over 10 minutes Repeat dose if required or follow with IV infusion 1-2 microg/kg/min (max 200 microg/min) Adjust infusion according to response and heart rate, increase if necessary, up to 5 microg/kg/min (max 200 microg/min) Alternatively, can give the IV infusion as initial treatment Aminophylline, magnesium and salbutamol must be given via separate IV lines Consider Adrenaline 10 microg/kg or 0.01 mL/kg of 1:1000 (max 0.5 mL) IM, into lateral thigh which should be repeated after 5 minutes if the child is not improving Intensive care admission for respiratory support (face mask CPAP, BiPAP, or intubation/IPPV) may be needed

Doses:

Salbutamol (100 mcg/puff) dose:

<6 years old: 6 puffs MDI
6 years or older: 12 puffs MDI

Ipratropium bromide (21 mcg/puff) dose:

<6 years old: 4 puffs MDI
6 years or older: 8 puffs MDI

Oral prednisolone

2 mg/kg (max 60 mg) initially, only continuing with 1 mg/kg daily for further 1-2 days if there is ongoing need for regular salbutamol

Other management considerations:

If there is any concern about anaphylaxis give adrenaline. See Anaphylaxis

Beware salbutamol toxicity: tachycardia, tachypnoea, metabolic acidosis. Can occur with both IV and inhaled treatment. Lactate levels are commonly high. Consider stopping/reducing salbutamol as a trial, if you think this may be the problem

Beware severe hypokalaemia: can occur with frequent Salbutamol use, as this draws potassium into cells. Consider monitoring potassium levels. If the child is on IV fluids, consider adding 20-40 mmol of potassium chloride to prevent hypokalaemia in children likely to require frequent salbutamol
Careful salbutamol dosing

Consider consultation with local paediatric team when

Moderate or severe asthma
Poor response to inhaled salbutamol
Oxygen requirement

Consider transfer when

Severe or critical asthma requiring intravenous treatment or respiratory support
Children with escalating O₂ requirement
Children poorly salbutamol responsive or unable to wean salbutamol requirement
Children requiring care above the level of comfort of the local hospital

For emergency advice and paediatric or neonatal ICU transfers, see Retrieval Services

Consider discharge from Emergency Department when

One hour after initial assessment, if mild presentation and no risk factors for severe disease
Adequate oxygenation: mild hypoxia (SpO₂ 90-94) should not preclude discharge if child is clinically well and has responded well to treatment
Adequate parental education and ability to administer salbutamol via spacer
Adequate oral intake

Discharge requirements:

Observe inhaler and spacer technique
Give a written action plan with education on reliever use. This can be generated using the action plan generator
Organise follow-up with a GP and/or paediatrician
Advise parents to seek further medical attention (preferably from their GP) should the child's condition deteriorate or if there is no significant improvement within 48 hours
Give carers written information (see Parent information), including advice regarding maximising adherence, reducing exposure to asthma triggers (eg avoidance of tobacco smoke) and immunisation. Patient and carer education tips can be found in the Australian Asthma Handbook

Resources

Parent Information

Kids Health Info

Additional notes

IV magnesium sulfate 50% dosing

Check doses carefully

0.1 mmol/kg = 25 mg/kg = 0.05 mL/kg
0.2 mmol/kg = 50 mg/kg = 0.1 mL/kg
0.4 mmol/kg = 100 mg/kg = 0.2 mL/kg

Check concentrations carefully

0.4 mmol/mL = 100 mg/mL
0.5 mmol/mL = 125 mg/mL

For IV MgSO4 50% 1 mL = 2 mmol = 500 mg
eg For a 25 kg child, the dose will be 25 kg x 50 mg/kg (0.1 mL/kg)

Thus, total volume = volume MgSO4 50% (mL) + volume of 0.9% sodium chloride (mL)
= 2.5 mL of MgSO4 + 3.75 mL 0.9% sodium chloride
= 6.25 mL

If going to ICU, Magnesium sulfate may be continued as a 0.12 mmol/kg/hour infusion. Aim to keep serum magnesium between 1.5 and 2.5 mmol/L

Long term asthma control

The frequency of acute episodes and any interval or persistent symptoms should be reviewed
Specific questions should be asked about sleep disturbance (due to asthma), early morning symptoms, exercise induced cough or wheeze, easy fatiguability, parental smoking and frequency of bronchodilator use
Higher body mass index (BMI) may be associated with increased asthma severity
See Asthma handbook for more information

Preventive Treatment

Consider preventive treatment if there are interval or persistent symptoms (more than one disturbed night per week, difficulty participating in physical activities, or bronchodilator use on more than one day per week). There is a limited role in children with viral induced asthma, even with frequent exacerbations
First line treatment: low dose inhaled corticosteroids or leukotriene inhibitors (montelukast). Combined steroids and long acting beta agonists (eg fluticasone/salmeterol) should NOT be first line treatment
Careful attention must be paid to the delivery system chosen

Spacers

A spacer device should be used for children of all ages whenever they use a MDI
Small volume spacers are suitable for children of all ages
Small volume spacers should be fitted with a well-sealing face mask for younger children who cannot reliably seal their lips around the mouthpiece. A mask is usually not needed in children older than 5 years
See Asthma handbook for more information

Oxygen Saturations

Oxygen saturation (SpO₂) may be reduced in the absence of significant airway obstruction due to factors such as atelectasis and mucous plugging of airways
SpO₂ is purely a measure of oxygenation, which may be preserved in the presence of deteriorating ventilation (with CO₂ retention)
Use humidified oxygen. Indiscriminate use of non-humidified oxygen may also lead to drying of the upper airways leading to worsening bronchoconstriction. The use of humidified O₂ might mitigate this

Last Updated December 2020

Reference List

Australia NA. Australian asthma handbook, version 1.3. Melbourne: National Asthma Council Australia. 2017.

Chang, Anne B., et al. "A 5‐versus 3‐day course of oral corticosteroids for children with asthma exacerbations who are not hospitalised: a randomised controlled trial." Medical Journal of Australia 189.6 (2008): 306-310.

Craig SS, Dalziel SR, Powell CV, Graudins A, Babl FE, Lunny C. Interventions for escalation of therapy for acute exacerbations of asthma in children: an overview of Cochrane Reviews. Cochrane Database of Systematic Reviews. 2020(8).

Foster, S. J., et al. "Oral prednisolone in preschool children with virus-associated wheeze: a prospective, randomised, double-blind, placebo-controlled trial." The Lancet Respiratory Medicine 6.2 (2018): 97-106.

Griffiths B, Ducharme FM. Combined inhaled anticholinergics and short-acting beta2-agonists for initial treatment of acute asthma in children. Cochrane Database Syst Rev 2013; :CD000060.

Griffiths B, Kew KM. Intravenous magnesium sulfate for treating children with acute asthma in the emergency department. Cochrane Database Syst Rev 2016; 4:CD011050.

Kayani, Sohail, and Daniel C. Shannon. "Adverse behavioral effects of treatment for acute exacerbation of asthma in children: a comparison of two doses of oral steroids." Chest122.2 (2002): 624-628.

Quinonez RA, Garber MD, Schroeder AR, et al. Choosing wisely in pediatric hospital medicine: five opportunities for improved healthcare value. J Hosp Med 2013; 8:479.

Smith M, Iqbal SMSI, Rowe BH, N'Diaye T. Corticosteroids for hospitalised children with acute asthma. Cochrane Database of Systematic Reviews 2003, Issue 1. Art. No.: CD002886. DOI: 10.1002/14651858.CD002886.

The Royal Children's Hospital Melbourne

Clinical Practice Guidelines