Liquid Nitrogen has many medical uses including cryosurgery. Commonly used to freeze benign growths, precancers and skin cancers. Also used in Fertility treatments such as freezing reproductive tissue and cells.
Entonox (50% Oxygen 50% Nitrous Oxide) is a widely used base as a anaesthetic generally supplemented with potent volatile or intravenous anaesthetic agents. Also used widely in birthing units and even dentists.