Potential for error when assessing blood cyanide concentrations in fire victims

The present study explores toxicologic significance of blood cyanide concen trations in fire victims. Headspace ps chromatography was used for cyanide detection. Analysis of blood samples from ten fire victims (postmortem inte rval = 8 h to 3 to 5 d) detected zero to 11.9 mg/L of cyanide and a large d ifference in cyanide concentrations among victims. Carboxyhemoglobin (COHb) saturation was in the range of 24.9 to 84.2%. To examine the effects of me themoglobinemia and postmortem interval on blood cyanide concentrations in fire victims, an experiment was carried out using rabbits as the animal mod el. The rabbits were sacrificed by intramuscular injection of 1 mL/kg 2% po tassium cyanide 5 min after intravenous injection of 0.33 mL/kg of 3% sodiu m nitrite (Group A, n = 3) or physiological saline (Group B, n = 6). Averag e methemoglobin contents immediately before potassium cyanide administratio n were 6.9 and 0.8% in Groups A and B, respectively. Average cyanide concen trations in cardiac blood at the time of death were 47.4 and 3.56 mg/L, res pectively. When blood-containing hearts of the rabbits (n = 3 for Group B) were left at 46 degreesC for the first 1 h, at 20 to 25 degreesC for the ne xt 23 h and then at 4 degreesC for 48 h, approximately 85 and 46% of the or iginal amounts of blood cyanide disappeared within 24 h in Groups A and B, respectively. After the 72-h storage period, 37 and 10%, respectively, of t he original amounts of cyanide remained in the blood. When the other three hearts in Group B were left at 20 to 25 degreesC for the last 48 h without refrigeration, cyanide had disappeared almost completely by the end of the experiment. The present results, and those published in the literature demo nstrate that the toxic effects of cyanide on fire victims should not be eva luated based solely on the concentration in blood.