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Assigning a level of significance to cyanide concentrations found in the blood of fire victims is often hampered by the fact that cyanide is inherently unstable in cadavers and in stored blood samples. A few researchers have proposed that sodium fluoride can be used to minimize the instability of cyanide in blood samples; however, controlled studies have not been performed to support validation of this hypothesis. To test the sodium fluoride hypothesis, both treated and control blood samples from 14 autopsied fire victims were tested over a 25-30 day period. A 2% concentration of sodium fluoride was added to the blood samples at the start of testing and the samples were refrigerated between testing intervals. Cyanide concentrations in the treated and control samples were measured between 9 and 11 days post treatment and between 25 and 30 days post treatment. A statistically significant difference was not present between blood cyanide concentrations in treated and control samples between 9 and 11 days. During this time period, although there were small statistically significant increases in both treated and untreated samples the fluctuations were minor. Since the treated and control samples did not exhibit instability between 9 and 11 days, it is not surprising that the sodium fluoride appeared to have no effect. However, a statistically significant difference between blood cyanide concentrations in treated and control samples was observed between 25 and 30 days. Those samples treated with sodium fluoride showed a reduction in blood cyanide variability with virtually no overall change, over a 25-30 day period when compared to control samples, while unconditioned samples showed a significant, average increase of 35%. Based on the findings of this study, it is recommended that 2% sodium fluoride be added to blood samples obtained from fire victims to reduce cyanide instability due to bacteriological activity., (Copyright © 2010 Elsevier Ireland Ltd. All rights reserved.)

The toxicological and postmortem analysis of fire victims' blood and tissue can disclose the type and quantity of toxic species, such as carbon monoxide or hydrogen cyanide, that they inhaled prior to death. For fire cases, these toxicological data can reveal objective data about the nature and circumstances of a fire, and thus assist both the Medical Examiner and the Fire Investigator in their investigations. Assigning a level of significance to cyanide concentrations found in the blood and tissue of fire victims is often hampered by the fact that cyanide is inherently unstable in cadavers and in stored tissue samples. Numerous researchers have provided insight into and characterized the stability of cyanide in the body and in collected biological specimens. Based on studies by these researchers, the rate of transformation of cyanide in blood and tissue specimens is dependent on the initial cyanide concentration in the sample at time of death, the length of time that a sample remains in the cadaver, the length of time that a sample remains in storage, and the preservation (e.g., addition of sodium fluoride to sample) and storage conditions (e.g., temperature) of the sample.