Proceedings: Cryofibrinogenaemia and activation of the coagulation/lysis systems in accidental hypothermia of the elderly.

pathologists have experience of unexpectedly low carboxyhaemoglobin saturation levels in fatal carbon-monoxide poisoning. The textbooks give 60% as the minimum lethal concentration for healthy subjects. Why then should apparently fit persons, below the age of 70, die with saturation levels below 50% ? A series of 300 included 24 such cases, with values from 40 to 490o (palladium chloride analysis accurate to about 5 %). An explanation was provided by two cases in which subclavian blood gave unbelievably low readings, but femoral samples showed higher saturation levels. Vigorous artificial respiration had been given to both. An infant from a fire was also given intravenous saline at hospital where artificial respiration was continued for an hour. Subclavian blood showed only 150% saturation and femoral blood 31%, though hypostasis was characteristically pink. In a male suicide of 57 the values were 32 to 52%, respectively. Enquiries revealed that the local ambulance services give artificial respiration, with oxygen or Entonox, to all persons found dead, unless obviously inappropriate. Since blood with a high carboxyhaemoglobin content does not clot, vigorous artificial respiration moves blood into and out of the lungs of the cadaver. Dissociation of carboxyhaemoglobin occurs, assisted by high oxygen concentrations in the respired gas. Some mixing of the blood in veins near the lungs results, lowering their carboxyhaemoglobin content. Femoral blood from the thigh is much less affected. Circulation of the infant's blood was probably assisted by the intravenous infusion and by the prolongation of artificial respiration. When artificial respiration has been tried, carboxyhaemoglobin saturation levels will be falsely low in blood from sites near the lungs (heart, subclavian vein). Blood for analysis should be taken from more distant sites such as the thigh.