ALS MCQ – Carbon Monoxide Suicide Attempt

A 20 year – old man is brought to hospital having been found in a running car in shut garage.  On arrival he is ataxic and listless with a GCS of 11.  Haemodynamically stable with a RR of 30 bpm and SaO2 99%.  Arterial blood gas showed: PaO2 40 kPa (300 mmHg), PaCO2 3.6 kPa (27 mmHg), carboxyhaemoglobin 22%, lactate 11 (99 mg/dl).  Which of the following statements is/are correct?:
a) The patient has moderate carbon monoxide poisoning.
b) Treatment with hydroxocobalamin can interfere with the measurement of carboxyhemoglobin.
c) Raised lactate in this context is non – specific  of inhalational injury.
d) Carboxyhaemoglobin levels in this patient are an indication for hyperbaric therapy.