Stabilization of Blood Cyanide

• Published in: Journal of analytical toxicology 1998-03, Vol.22 (2), p.176-178
• Main Authors: Vesey, C.J., Langford, R.M.
• Format: Article
• Language: English
• Subjects: Cyanides - blood; Drug Stability; Forensic Medicine - methods; Humans; Smoke Inhalation Injury - blood; Specimen Handling - methods
• ISSN: 0146-4760; 1945-2403
• DOI: 10.1093/jat/22.2.176

The measurement of blood cyanide is of clinical importance because, aside from the relatively few cases of accidental or self-induced poisoning, raised levels are found in patients receiving the hypotensive agent sodium nitroprusside (1), in victims of smoke inhalation injury (2), and in populations at risk of ataxic myelopathy in areas of high cassava consumption (3). However, very few hospital laboratories have the means of measuring cyanide, and blood samples may need to be transported to one offering the service. As losses of cyanide may occur (4,5) in transit, resulting in underestimation, a stabilizing technique would improve analytical accuracy. In one procedure, the blood is added to acidified silver sulfate. By subsequently increasing the acid concentration, the cyanide can be liberated from the silver cyanide and transferred to a small amount of sodium hydroxide solution with a stream of nitrogen (6). In another method, a small volume of sodium nitrite solution is added to the blood so that cyanide is retained as cyanmethemoglobin. It is possible then to separate the red cells, which contain all of the cyanide, and measure the cyanide in a protein-free extract without recourse to nitrogen aeration (7). A modification of the second procedure was adopted for a study of cyanide levels in patients with smoke inhalation injury admitted to casualty departments throughout the U.K. because blood samples were sent to the laboratory by mail.