Correlation of Atmospheric and Inhaled Blood Cyanide Levels in Miniature Pigs

The LCT50 (exposure time and atmospheric concentration needed to produce 50% lethality) has been commonly used to quantify the toxicity of a gas such as hydrogen cyanide (HCN). Few studies have been performed in which blood cyanide concentrations were measured simultaneously in animals at known exposure concentrations and time. This study was an attempt to correlate which blood cyanide levels would cause lethality in miniature pigs when exposed to hydrogen cyanide (HCN) for a fixed time. An automated microdistillation assay (1) was used to continuously monitor arterial blood cyanide before, during and after the exposures to a HCN/air mixture. Seven animals were exposed to a HCN/air mixture for two minutes each, four to 1176 ±SD 70 mg/m 3, and three animals to 2125 ±SD 91 mg/m 3 . Two of the three animals exposed to the high HCN/air mixture died with a peak blood cyanide concentration of about 4.1 ±SD 0.38 µg/mL. Four animals exposed to the low HCN/air mixture had a peak blood cyanide concentration of 2.94 ±SD 0.71 µg/mL. All four survived for a 24-hour post-exposure observation period before they were sacrificed. Several physiological parameters were also monitored.