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Asthma - life threatening

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Recognition of Life-threatening Asthma

  • Deterioration despite maximal therapy on severe asthma pathway 
  • Respiratory - cyanosis/exhaustion 
  • Neurological - confusion/drowsiness. 
  • Cardiovascular - pulsus paradoxus 
  • Consider diagnoses other than asthma, especially in infants with poorly responsive respiratory distress. 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 assistance - request urgent review with PICU/CED Senior 
  2. OXYGEN - use high flow oxygen via mask (e.g. 15L/min). 
  3. IV access 
  4. Give Hydrocortisone 4 mg/kg IV as soon as possible. 
  5. Nebulised bronchodilators - Continuous nebulised salbutamol 5 mg/dose for all ages. Add ipratropium bromide 0.25 mg to the second nebuliser, if there is inadequate response to the first salbutamol nebule. Repeat ipratropium every 20 minutes for 3 doses, then every 4 hours. 
  6. IV salbutamol bolus Give 10 micrograms/kg (single dose maximum 500 micrograms). Over 2 minutes. Give in a minimum volume of 5ml (can be diluted with 0.9% Saline). Repeat dose at 10 minutes if still not improving 
  7. IV magnesium sulphate bolus. Use magnesium sulphate 49.3% (493mg/ml). Give 0.1 ml/kg (approx 50mg/kg) over 20 minutes (dilute to 20mls with normal saline and infuse via syringe driver). Maximum dose 5 mls (2.5 g). 
  8. IV aminophylline bolus. Give 10 mg/kg IV (maximum dose 500 mg) over 1 hour (dilute to 1mg/ml - the total volume will be 10ml/kg, compatible with fluid containing Sodium chloride and/or Dextrose and/or Potassium). 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). 
  9. If inadequate response to bolus therapy then start further IV therapy in form of salbutamol +/- aminophylline infusion(s). These children require admission to PICU.

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% dextrose
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% dextrose   
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% dextrose  
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

British Guideline on the Management of Asthma (http://www.sign.ac.uk/guidelines/published/support/guideline63/download.html)

Advanced Paediatric Life Support, BMJ Book - Third Edition

Browne GJ, Trieu L, Van Asperen P. Randomized, double blind, placebo-controlled trial of intravenous salbutamol and nebulized ipratropium bromide in early management of severe acute asthma in children presenting to an emergency department. Crit Care Med 2002 Feb; 30(2): 448-53

Cheuk DKL, Chau TCH, Lee SL. A meta-analysis on intravenous magnesium sulphate for treating acute asthma. Arch Dis Child 2005; 90: 74-77

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Document Control

  • Date last published: 01 April 2007
  • Document type: Clinical Guideline
  • Services responsible: Children’s Emergency Department
  • Author(s): Fran Settle
  • Editor: Greg Williams
  • Review frequency: 2 years

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