asthma_paed

Mx of critically severe paediatric asthma

oxygen to maintain SaO2 > 92%
- use high flow intranasal oxygen if needed
contact senior staff ASAP and move patient to a resuscitation cubicle
continuous salbutamol nebulisers (0.5% undiluted) until infusions are commenced
nebulised ipratropium 20 minutely x 3 doses, added to salbutamol:
- <20kg: 250 mcg nebule/dose
- >20kg: 500 mcg nebule/dose
iv access x 2
take bloods for FBE, U&E, lactate and serial venous blood gas as needed
- arterial blood gases are usually not needed but if intubated, then consider via arterial line
methylprednisolone 1 mg/kg i.v. 6-hourly
- alternatively, can use iv hydrocortisone 4mg/kg 4-6hrly
portable CXR to exclude complications of asthma

if in extremis, may need to intubate then start infusions
if not a tertiary paediatric hospital, contact the tertiary hospital to arrange retrieval service and transfer

use 50ml obstetric salbutamol solution (1mg/ml) undiluted
determine base infusion rate for 1mcg/kg/min = wt x 0.06 ml/hr
for those over 40kg, calculate as if 40kg¹⁾
load dose is 5-10mcg/kg/min for 1 hour = 5-10 x the base infusion rate calculated above
- many give a load dose of 5mcg/kg over 10min²⁾ but this is nonsensical if they then advise initial maintenance infusion rate of 5mcg/kg/min, titrated to 1-10mcg/kg/min
maintenance rate is 1-2mcg/kg/min = 1-2 x the base infusion rate calculated above

use in addition to iv salbutamol, if inadequate response to iv salbutamol or child is in extremis
must be given in separate line to iv salbutamol (hence the 2nd iv access line)
set up infusion by adding 25mg/kg aminophylline to 5% dextrose to make total of 50mls = 0.5mg/kg/ml
if patient is NOT on aminophylline or theophylline then give a LOADING DOSE:
- 10mg/kg (max. 500mg) over 1 hour = 20ml/hr if weight < 50kg, otherwise 500mg/(0.5mg/kg x weight in kg) ml/hr
maintenance aminophylline infusion:
- age 1-9 years:
  - rate = 1.1mg/kg/hr = 2.2ml/hr if using 0.5mg/kg/ml infusion as above
- age 10 yrs and over:
  - rate = 0.7mg/kg/hr = 1.4ml/hr if using 0.5mg/kg/ml infusion as above

may be of benefit
load dose infusion 50mg/kg of magnesium sulphate infused over 20min:
- 0.1ml/kg of 50% magnesium sulphate diluted to 20ml with 0.9% saline and infuse at 1ml/min for 20min.
maintenance infusion:
- 0.12mmol/kg/hr (to max. 8mmol/hr) = 0.06ml/kg/hr (max. 4ml/hr) of 50% solution (2mmol/ml)
- aim for target serum magnesium level of 1.5-2.5mM

especially if poor response or becoming tired and rising PCO₂:
experienced staff - consider calling anaesthetics to assist
ensure equipment and medications checked and ready as per usual rapid sequence induction

maintenance neuromuscular relaxants
- eg. vecuronium 0.1mg/kg every 30min or so
maintenance sedation
- eg. morphine/midazolam infusion 1mg/ml of each, give at 20-80mcg/kg/hr
CXR post-intubation
care with ventilation (see below)
arterial line to monitor blood gases

the prime aims are to ensure:
- maintenance of oxygenation SaO2 > 92%
- maintenance of near-normal pCO₂ levels 35-45 mmHg
- minimise risk of iatrogenic pneumothorax
- minimise risk of iatrogenic air trapping and resultant impaired venous return which may result in hypotension and pulseless electrical activity (PEA)
aim for prolonged expiratory phase and lower respiratory rate than normal (eg 8-12/min for adolescent)

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