Estimation of carboxyhemoglobin concentrations in thermo-coagulated blood on a CO-oximeter system: an experimental study.

In order for forensic toxicological application of a CO-oximeter system to carboxyhemoglobin (CO-Hb) analysis of thermo-coagulated blood, an experimental study was performed. Blood samples containing varying concentrations of CO-Hb were gradually heated up to 70-80 degrees C in ca. 1-13 min, and the extracts (soluble fractions) were examined. CO-Hb contents in the extracts did not represent those in whole thermo-coagulated blood, showing a considerable increase especially for the samples with the initial CO-Hb levels of ca. 25-50%. Changes in CO-Hb % measurements depended little on the heating time but greatly on the final temperature of the blood. The apparent increase in CO-Hb measurements proved to be significantly related to the decrease in total soluble hemoglobin due to thermo-coagulation which depended on the CO-Hb contents, not due to CO-Hb formation by heat. Although gas chromatographic analysis of CO combined with appropriate measurement of total hemoglobin would be required for accurate CO-Hb determination of thermo-coagulated blood, a possible method for rough estimation (semiquantitative screening) of CO-Hb content in whole thermo-coagulated blood with the CO-oximeter was proposed on the basis of thermostability of CO-Hb. The estimated CO-Hb values correlated with the contents measured by a gas chromatographic method independently of the heating time or final temperature up to 80 degrees C.