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Child Health Guideline Identifier

Asthma - life threatening

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Recognition of Life-threatening Asthma

  • Respiratory - silent chest, exhaustion, cyanosis, increasing hypoxia
  • Neurological - agitation, confusion, drowsiness 
  • Cardiovascular - marked tachycardia, bradycardia

Consider diagnoses other than asthma if not responding to treatment.

No infant (< 1 year) should be started on intravenous bronchodilators without discussion with a consultant. 

Management

If the patient's condition is improving therapy can be de-escalated at any stage - see Asthma - Management of Acute Guideline.

  1. Call for help - request urgent review with CED Senior / PICU 
  2. OXYGEN - use high flow oxygen via mask (e.g. 15L/min)
  3. Consider IM adrenaline 0.01 ml/kg (10 micrograms/kg) of 1:1000 solution (minimum dose 0.1 ml, maximum dose 0.5ml) in the following situations:
    1. Peri-arrest. Call a Code Blue (777)
    2. Anaphylaxis is suspected
    3. Delay in obtaining intravenous access
  4. IV access 
  5. Continuous nebulised salbutamol 5 mg/dose for all ages, including while receiving intravenous therapy
  6. Nebulised ipratropium bromide 0.25 mg/dose for all ages, add to salbutamol nebuliser. Repeat ipratropium every 20 minutes for 3 doses, then every 4 hours
  7. Hydrocortisone 4 mg/kg IV
  8. IV salbutamol bolus 10 micrograms/kg (single dose maximum 500 micrograms)
    1. IV salbutamol bolus may not be required if the patient has received at least 3x salbutamol nebulisers
    2. Give 10 micrograms/kg over 2 minutes. Dilute to a minimum volume of 5ml with 0.9% Saline.
    3. Consider repeating dose at 10 minutes if not improving
    4. Non-life threatening side effects can occur with both inhaled and IV therapy: tachycardia/ arrhythmias, tachypnoea, metabolic acidosis, high lactate, hypokalaemia
  9. IV magnesium sulphate bolus
    1. Dose = 0.2mmol/kg (max dose = 10mmol) - in Starship prescribe in mmol
    2. Give over 20 minutes
    3. Dilute to 50ml with sodium chloride 0.9% and infuse via syringe driver
    4. Starship currently uses magnesium sulphate 49.3% (493mg/ml or 2mmol/ml) - using this strength the dose = 0.1ml/kg
  10.  IV aminophylline bolus 10mg/kg (maximum dose 500 mg)
    1. Give 10 mg/kg IV over 1 hour
    2. Dilute to 50mL with sodium chloride 0.9%, glucose 5% or glucose 10%, and infuse via syringe driver
    3. If the child is already on oral theophylline, do not give IV aminophylline unless you have obtained a baseline serum level and can calculate a reduced loading dose. If patient is on any other medications you must check for potential interactions and adjust dose accordingly (see below).
    4. Non-life threatening side effects include vomiting, palpitations, dizziness, headache
  11.  If there is an inadequate response to bolus therapies PICU should be consulted. These patients require HDU/ PICU level care.
  12.  Start an aminophylline infusion (see below) and/or a salbutamol infusion (see below) in consultation with PICU.
  13.  There is a role for non invasive ventilation (CPAP or high-flow) in life threatening asthma and this should be considered as an additional treatment modality

Remember if child is improving therapy can be de- escalated at any stage

Salbutamol Infusion

Dose
5 -10 microgram/kg/min for 1 hour then reduce to 1 - 2 microgram/kg/min

If Patient Weight < 16kg
Add 3 mg/kg of IV salbutamol solution (1 mg/ml) to a 50 ml syringe and make up to 50 ml with 5% glucose
Then 1 ml/hr = 1 microgram/kg/min

If Patient Weight > 16kg
Draw up neat IV salbutamol solution (1 mg/ml) into a 50ml syringe (i.e. not diluted)
Then rate (ml/hr) = 0.06 x weight (kg) x dose (microgram/kg/min)
For example if you have a 20 kg child and want to infuse salbutamol at 5 microgram/kg/min then set rate at 0.06 x 20 x 5 = 6 ml/hr

IV Salbutamol infusion chart for patients >16kg
 Wt(kg) 1 microgram/kg/min    2 microgram/kg/min 5 microgram/kg/min  10 microgram/kg/min 
16 1ml/hr 1.9ml/hr  4.8ml/hr  9.6ml/hr 
18 1.1ml/hr  2.2ml/hr 5.4ml/hr  10.8ml/hr 
20 1.2ml/hr  2.4ml/hr  6ml/hr  12ml/hr 
22 1.3ml/hr  2.6ml/hr  6.6ml/hr  13.2ml/hr 
24 1.4ml/hr  2.9ml/hr  7.2ml/hr 14.4ml/hr 
26  1.6ml/hr 3.1ml/hr  7.8ml/hr 15.6ml/hr 
28  1.7ml/hr  3.4ml/hr  8.4ml/hr 16.8ml/hr 
30  1.8ml/hr  3.6ml/hr 9ml/hr  18ml/hr 
35  2.1ml/hr  4.2ml/hr  10.5ml/hr  21ml/hr 
40  2.4ml/hr  4.8ml/hr  12ml/hr  24ml/hr 
45  2.7ml/hr  5.4ml/hr  13.5ml/hr  27ml/hr 
50  3ml/hr  6ml/hr 15ml/hr  30ml/hr
60  3.6ml/hr  7.2ml/hr  18ml/hr  36ml/hr 
70  4.2ml/hr  8.4ml/hr  21ml/hr  42ml/hr 

Aminophylline Infusion

Dose if patient aged 1 - 9 years
1.1 mg/kg/hour
Add 55 mg/kg of IV aminophylline solution (25 mg/ml) to a 50 ml syringe and make up to 50 ml with 5% glucose   
Then infuse at 1 ml/hr  
If weight between 23-30kg (50th centile for 9 year olds) then use neat IV aminophylline solution (25mg/ml) in a 50ml syringe and run at 1ml/hr. 
Dose if patient aged 10 - 15 years and weight < 35 kg 
0.7 mg/kg/hour
Add 35 mg/kg of IV aminophylline solution (25 mg/ml) to a 50 ml syringe and make up to 50 ml with 5% glucose  
Then infuse at 1 ml/hr  
Dose if patient aged 10 - 15 years and weight > 35 kg
0.7 mg/kg/hour  
Draw up neat IV Aminophylline solution (25 mg/ml) into a 50 ml syringe 
Then infuse at 0.028 ml/kg/hr 
For example if you have a 40 kg child then infusion rate will be 40 x 0.028 = 1.12 ml/hr 
Dose adjustment for obesity 
Use 50th percentile of expected weight for age
Factors increasing Aminophylline clearance 
Tobacco 
Phenytoin
Carbamazepine
Phenobarbitone
Factors decreasing Aminophylline clearance 
Influenza vaccination 
Pulmonary oedema 
Hepatic or renal dysfunction 
Cimetidine  
Erythromycin    
Ciprofloxacin

References

  • 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
  • Mitra AAD, Bassler D, Watts K, Lasserson TJ, Ducharme FM. Intravenous aminophylline for acute severe asthma in children over two years receiving inhaled bronchodilators. Cochrane Database of Systematic Reviews 2005, Issue 2. Art. No.: CD001276
  • Rossing TH, Fanta CH, Goldstein DH, et al. Emergency therapy of asthma: comparison of the acute effects of parenteral and inhaled sympathomimetics and infused aminophylline. Am Rev Respir Dis 1980; 122:365.
  • Melbourne Royal Children's Hospital acute asthma guideline
  • UpToDate

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Document Control

  • Date last published: 08 February 2017
  • Document type: Clinical Guideline
  • Services responsible: Children’s Emergency Department
  • Author(s): Sarah Dunlop
  • Editor: Greg Williams
  • Review frequency: 2 years

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