Toxicology of nitrous oxide

Since the first description of its anaesthetic effects by Horace Wells in 1844, nitrous oxide (N2O) or ‘laughing-gas’ was, for a long period, considered to be an inert gas. However, since Lassen, in 1956, published details of the occurrence of aplastic anaemia and septicaemia in patients after prolonged N2O-exposure, we know that there are toxicological effects. The majority of these secondary effects – haematopoietic toxicity, bone marrow depression, myeloneuropathy, neuropsychiatric abnormalities, DNA-synthesis inhibition, immunotoxic potential, malnutrition and drug interactions – can be explained by the interactions of N2O with vitamin B12metabolism. The reduced fertility and fetotoxicity can only partially be explained by the inhibition of DNA synthesis that is caused by B12-deficiency. The exact mechanism in humans is unknown. Diffusion hypoxia and asphyxia while under N2O-anaesthesia is discussed in Chapter 2.