Sample pre-treatment for CO-oximetric determination of carboxyhaemoglobin in putrefied blood and cavity fluid

Blood or blood-containing cavity fluid samples recovered from decomposed bodies in suspected carbon monoxide (CO) poisoning cases often have low total haemoglobin (tHb) levels or contain significant amounts of oily droplets, methaemoglobin (MetHb) and sulphaemoglobin (SHb), all conditions which render the validity of the measurements of carboxyhaemoglobin (HbCO) by commercially available CO-oximeters doubtful. Two sample pre-treatment methods, namely, centrifugal evaporation and addition of a commercially available standard haemoglobin solution containing a known level of HbCO, were developed to render such putrefied samples amenable to analysis by CO-oximeters. The methods developed were validated with samples of various degrees of putrefaction and various HbCO levels. The relative uncertainty of the determined HbCO levels as compared to their corresponding reference levels for the centrifugal evaporation method was approximately 5% and that for the standard addition method was <20%.