A pre-hospital clinician is managing an entrapped patient in a vehicle. The patient has been receiving Entonox for analgesia for 30 minutes. What specific monitoring concern applies with prolonged Entonox use?AEntonox causes immediate liver toxicityBThere are no monitoring concerns with Entonox at any durationCProlonged use (>15-20 minutes) can cause megaloblastic changes due to nitrous oxide inactivating vitamin B12 - this is a theoretical concern for extended use but practically, the risk of oxygen dilution (Entonox delivers 50% O2) in a hypoxic patient is more immediately relevantDEntonox is addictive after a single useEProlonged Entonox causes permanent hearing lossCheck my answer