Human Bone Marrow Biochemical Function and Megaloblastic Hematopoiesis after Nitrous Oxide Anesthesia

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Abstract
Prolonged exposure to N2O inhibits bone marrow function. The duration of exposure to N2O necessary to induce these changes and their permanence is unknown. The possible prophylactic effect of prior treatment with folinic acid was not examined previously. Bone marrow function in patients receiving N2O was asssessed by the deoxyuridine (dU) suppression test. Morphologic changes in the bone marrow were also studied. Three groups of patients undergoing cardiac surgery were studied. One group was exposed for < 6 h, the next for 12-24 h and a control group received no N2O. The control group and the short-exposure group showed no abnormality of bone marrow function. The long-exposure group had abnormal dU suppression tests and a megaloblastic hematopoiesis. The changes observed in this group resolved 12 h after discontinuance of the anesthetic. The changes were prevented by the preoperative administration of folinic acid. The absence of morphologic or dU suppression test abnormalities following N2O anesthesia for periods of < 6 h confirmed the safety of this anesthetic for the majority of operations. Prolonged exposure to the gas caused impaired marrow function which was of a temporary nature and prevented by the prior administration of folinic acid.