Methodologic considerations in the interpretation of postmortem carboxyhemoglobin concentrations

The interpretation of postmortem carboxyhemoglobin (COHb) concentrations can have major implications even when COHb is not the direct cause of death. Much litigation may hinge on the length of time an individual was alive during the fire. Therefore, the reliability of an analytical method to measure COHb, ranging from low to sub-lethal levels, is critical to the proper interpretation of results. This study used 40 blood specimens from fire deaths and 15 blood specimens from non-fire deaths to compare COHb levels obtained from a spectrophotometric method (IL 482 CO-Oximeter; CO-Ox) with a reference gas chromatographic method (GC). Since spectrophotometric methods are influenced by the amount of total hemoglobin (Hb) present in the blood, multiple saline dilutions of specimens were performed to yield Hb as low as 1g/dl. For GC COHb concentrations < 5% and Hb > or = 4g/dl, the average and median ratios of CO-Ox COHb to GC COHb concentrations were 2.8 and 2.6 respectively. These ratios were 8.0 and 6.8 respectively when Hb < 4g/dl. At GC COHb levels ranging from 5 to 40% and Hb > or = 4g/dl, the average and median ratios were 1.6 and 1.0 respectively. These ratios were correspondingly 2.1 and 1.9 when Hb < 4 g/dl. These data clearly indicate COHb can be influenced by the analytical methods used.

Gas chromatographic procedures for determination of ethanol in postmortem blood using t-butanol and methyl ethyl ketone as internal standards

Three gas chromatographic procedures for the determination of ethanol in postmortem blood using alternative internal standards to n-propanol are presented: a direct injection procedure using t-butanol, and two headspace methods using t-butanol and methyl ethyl ketone. t-Butanol and methyl ethyl ketone were well resolved from ethanol, acetone, methanol and other commonly observed putrefactive volatiles using direct injection or headspace analysis. CVs for the direct injection method were below 5% for ethanol and below 10% for the other volatiles. The lower limits of detection (LOD) were 25-50 mg/L. The CVs for the headspace methods were below 5% for ethanol and below 6% for the other volatiles. The LODs were 10 mg/L using either t-butanol or methyl ethyl ketone as internal standards. The use of t-butanol or methyl ethyl ketone as alternatives to n-propanol avoids the possibility of error in the quantitation of ethanol due to the presence of n-propanol and allows for the identification of other volatiles that may aid in distinguishing antemortem ingestion from postmortem production of ethanol.

Mefloquine distribution in postmortem cases

Mefloquine is currently the drug-of-choice for malaria prophylaxis among military personnel. Four active duty military personnel receiving 250 mg mefloquine per week were killed in the line of duty under combat conditions. Samples of blood, bile, liver, kidney, muscle, brain, spleen and lung were submitted to the Division of Forensic Toxicology, Office of the Armed Forces Medical Examiner, for routine toxicologic analysis. Qualitative screening revealed only the presence of ethanol (< 25 mg/dl, probably attributable to postmortem formation) and mefloquine. Quantitation of mefloquine was performed using an HP 5880 gas chromatograph equipped with a nitrogen/phosphorus detector. The column was an HP-5 cross-linked 5% phenyl methyl silicone fused silica capillary column (15 m x 0.25 mm i.d. x 0.25 microns film thickness). The temperature program began at 110 degrees C, was held for 1 min and ramped at 20 degrees C/min to 200 degrees C, held for 1 min and then ramped at 10 degrees C/min to 280 degrees C and held for 10 min. Mefloquine elutes with a relative retention time similar to that of the tricyclic antidepressants. No postmortem data concerning mefloquine concentrations or tissue distribution was available. Quantitated blood concentrations in the presented cases were greater than the expected therapeutic values indicating the possibility of postmortem redistribution of this drug. No mefloquine overdoses were identified in the literature making comparison to the postmortem therapeutic concentrations impossible at this time.