The effect of sepsis and short-term exposure to nitrous oxide on the bone marrow and the metabolism of vitamin B12 and folate.

It is recognised that prolonged anaesthesia with nitrous oxide (N2O) induces megaloblastic anaemia by oxidising vitamin B12. To determine whether sepsis aggravates the effect of N2O on haemopoiesis 5 patients with severe sepsis, who required surgery and were exposed to short-term (45-105 minutes) N2O anaesthesia, were studied. None had evidence of pre-operative vitamin B12 or folate deficiency. The effect of the combination of N2O anaesthesia and sepsis on DNA synthesis in bone marrow cells was assessed morphologically, and by the deoxyuridine suppression test. In 3 patients exposed to the longest duration (75-105 minutes) of N2O, addition of folinic acid and vitamin B12 partially improved the utilisation of deoxyuridine in vitro. No patient had evidence of megaloblastic haemopoiesis as judged by bone marrow morphology. It is concluded that prolonged N2O anaesthesia in patients with severe sepsis may adversely affect DNA synthesis. Although this effect did not manifest as overt megaloblastic erythropoiesis, it may be prudent to avoid N2O in such patients.