N2O. A greenhouse gas and an analgesic.
Discovered by Humphrey Davy, a one-time medical student, whose other accomplishments eclipsed this.
N2O opposes vitamin B12 and thus if used for a prolonged period can produce the confusing signs of B12 deficiency - subacute combined degeneration affecting the brain and spinal cord. In people deficient in B12 this is at least a theoretical risk with relatively short exposures such as anaesthesia. A situation where this is relevant is in repeated use of Entonox (premixed 50% N2O: 50% Oxygen) for dressings to burns or abscesses. Dearlove and Briggs briefly discuss the chemistry and "suggest ... that the oxidation reaction only occurs in fluids such as blood and not in the liver so that oxidation of Vitamin B12 by nitrous oxide only becomes significant where there are no hepatic stores."
Pragmatically, giving B12 if a lot of Nitrous is to be used seems unlikely to cause harm.
- ↑ Letters to the editor: Nitrous oxide and vitamin B12
- ↑ Doran M, Rassam SS, Jones LM, Underhill S. Toxicity after intermittent inhalation of nitrous oxide for analgesia. BMJ. 2004 Jun 5;328(7452):1364-5 Available from bmj.com here.
- ↑ Rapid responses to above paper (Toxicity after intermittent inhalation of nitrous oxide for analgesia.)