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Le trasladamos su inquietud al Dr. Federico Contreras, de TIASA, quien nos
responde: ". Con relación a la estabilidad de la carboxihemoglobina a altas
temperaturas depende de lo que entienda por "alta temperatura" quien formula la
pregunta, ya que al tratarse de proteínas son termolábiles y no tiene mucho
sentido investigarlas en un cuerpo carbonizado o que haya estado sometido a un
calor intenso. Les envío por las dudas un extracto sobre carboxihemoglobina de
un artículo muy bueno con métodos sencillos y económicos para toxicología de
urgencia (si les interesa puedo mandarles el artículo completo)."
Carbon
Monoxide (Carboxyhemoglobin, Chery-Red Blood)
Dilute 1 or 2 drops of blood
with about 15 ml. of water in a test tube so that the solution is now faint
pink. If the pink color is more than faint, add a little more water. This
variance depends upon the hemoglobin concentration in the blood.
Simultaneously have prepared a positive control, a normal blank, and the
unknown specimen; to each one add about 5 drops of 25 per cent sodium hydroxide.
Quickly cap and shake and observe if the original faint pink persists for a
while or if it immediately changes to straw yellow.
If the blood is negative
or contains less than 20 per cent carboxyhemoglobin, the pink color will
immediately turn a straw yellow. If the pink color persists for several seconds
or more, this indicates the presence of carbon monoxide in excess of 20 per
cent. However, even with high concentration of carbon monoxide this also (within
60 seconds or so) will eventually turn a straw yellow color. The intensity of
the pink color and its persistence before turning yellow will give a rough
approximation of the concentration. This test is specific for carboxyhemoglobin;
only fetal blood behaves similarly.
Evaluation: Below 10 per cent is normal;
10 to 20 per cent is subclinical; 20 per cent and above may be toxic; 40 per
cent and above is lethal.
For another rapid and more sensitive test (5 per
cent), use the Conway-Feldstein-Klendshoj microdiffusion technique. This test
uses 1 ml. of blood plus 1 ml. of 10 per cent sulfuric acid as expellant, and 2
ml. of palladium chloride (11 gm. Per 25 ml. 0.01 N hydrochloric acid) as
reactant. The reaction time is 1 hour at room temperature. A positive reaction
consists of a black film of palladium, the intensity of which is proportional to
the carbon monoxide concentration.
Kaye, S. Bedside Toxicology. School of
Medicine, University of Puerto Rico |
