A 24-year-old male who is a known asthmatic is admitted
with severe breathlessness.
His PEFR is 200 l/min
Blood gases on air show pH 7.5, pO2 9kPa, pCO2
3.3 kPa and bicarbonate 11 mmol/L
The patient is treated with steroids, oxygen and inhaled
He is reassessed a short while later and his blood gases
show pH 7.27, pO2 8kPa, pCO2 6.4 kPa, bicarbonate 16
In this patient which of the following investigations
would you arrange next?
Urine toxicology screen