United States Department of Transportation
i
In Vitro Absorption of Atmospheric Carbon Monoxide and Hydrogen Cyanide in Undisturbed Pooled Blood
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2012-09-01
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[PDF-436.83 KB]
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Edition:Final report.
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Abstract:Biological samples from victims of aircraft accidents are analyzed for carboxyhemoglobin (COHb) and cyanide ion
(CN¯) in blood. Such victims quite often suffer large open wounds near the autopsy blood collection sites. Many
aircraft crashes result in fires that fill the victim’s atmosphere with smoke rich in carbon monoxide (CO) and
hydrogen cyanide (HCN). It is important to determine whether pooled blood in those open wounds may have
absorbed CO and HCN after death, which could lead one to erroneously conclude that the presence of COHb and
CN¯ in blood was the result of breathing in these combustion gases. A chamber was designed from a laboratory
desiccator to establish whether CO and HCN may be absorbed in undisturbed, pooled whole human blood. A
magnetic stirring bar was placed at the bottom of the chamber to facilitate air movement. A ceramic plate with
concentric rows of holes was above the stirring bar to support a shallow open dish containing 4 mL of heparinized
blood. Gas syringes (100-cc) were used to evacuate air from and add pure CO into the chamber. The chamber
volume was 9038 cc. The blood was exposed to three concentrations of CO each for two different periods of time.
For HCN exposures, an extra dish containing a 5-mL beaker, which contained sodium cyanide (NaCN), was used.
Four mL of heparin-treated blood was used in the second dish. One mL of concentrated sulfuric acid was added to
the beaker containing NaCN through the lid opening. The volume of the HCN chamber was 8981 cc. Blood COHb
and CN¯ concentrations were determined spectrophotometrically. COHb levels of 4.3-11.0% were detected in blood
after its exposure to CO at 5532, 8298, 11064, 22129, and 33193 ppm for 30- and 60-min. CN¯ concentrations
(1.43-5.01μg/mL) in blood increased with exposure to HCN at 100 and 200 ppm each at 15, 30, 45, and 60 min.
Increases in the COHb levels observed in these experiments do not exclude the possibility for higher levels of COHb
in blood exposed to highly CO-rich atmospheres from actual fires. It was clearly evident that there is a strong
potential for CN¯ levels to increase by the absorption of atmospheric HCN. This selective absorption is consistent
with the insolubility of CO and solubility of HCN in water. Thus, postmortem COHb and CN¯ levels should be
carefully interpreted.
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