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Acute asthma

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    Asthma resources
    Asthma puffers and spacers photoboard  

    Key points

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


    • 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



    • 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


    • 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



    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


    Children with respiratory distress should have minimal handling


    Signs of severity 



    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) 


    Normal mental state 
    Some increased work of breathing


    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)



    Moderate-marked increased work of breathing, accessory muscle use/recession 


    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


    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



    Maximal work of breathing, accessory muscle use/recession 


    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


    • 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:

    1. Observe inhaler and spacer technique
    2. Give a written action plan with education on reliever use. This can be generated using the action plan generator
    3. Organise follow-up with a GP and/or paediatrician
    4. 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
    5. 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


    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)
    • = 1250 mg of MgSO4 50%
      = 2.5 mL of MgSO4 50%

    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


    • 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

    1. Australia NA. Australian asthma handbook, version 1.3. Melbourne: National Asthma Council Australia. 2017.
    2. 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.
    3. 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).
    4. 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.
    5. 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.
    6. Griffiths B, Kew KM. Intravenous magnesium sulfate for treating children with acute asthma in the emergency department. Cochrane Database Syst Rev 2016; 4:CD011050.
    7. 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.
    8. 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.
    9. 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.