Megaloblastic bone marrow changes after repeated nitrous oxide anaesthesia. Reversal with folinic acid

A seriously ill patient was found to have megaloblastic changes in his bone marrow after a nitrous oxide anaesthesia which lasted for 105 min. After an interval of 7 h a second nitrous oxide anaesthetic was administered, during which the patient received 30 mg of folinic acid. His marrow was normal when assessed 4 h later.