Poison in the blood

The study of the distribution of a poison, post mortem, presents a complex problem. The estimation of the poison in the blood presents a complex problem due to the putrefactive changes in blood and the minute quantity available for analysis. Distribution of insecticidal poisons from the blood to the tissues and body fluids takes place with some recirculation to the blood(lJ. 

Peritoneal dialysis involves instilling appropriate fluid into the peritoneal cavity. Poison in the blood diffuses into the dialysis fluid down the concentration gradient. The fluid is then drained and replaced. The technique requires little equipment but is one-half to one-third as effective as haemodialysis it may be worth using for lithium and methanol poisoning. 

Hemodialysis or hemoperfusion usually has limited use in the treatment of intoxication with chemicals. However, under certain circumstances, such procedures can be lifesaving. The utility of dialysis depends on the amount of poison in the blood relative to the total-body burden. Thus, if a poison has a large volume of distribution, as is the case for the tricyclic antidepressants, the plasma will contain too little of the compound for effective removal by dialysis. Extensive binding of the compound to plasma proteins impairs dialysis greatly. The elimination of a toxicant by dialysis also depends on dissociation of the compound from binding sites in tissues for some chemicals, this rate may be slow and limiting. 

Many poisons that are absorbed into the bloodstream are broken down by enzymes within the body s organs. The concentration of the poison in the blood then falls from its peak value. Figure 23.2 illustrates two cases where the fall in concentration is first order (as with paracetamol) and zeroth-order (as with ethanol). 

A diseased condition resulting from the presence of pathogenic bacteria and their associated poisons in the blood. 

Septicemia is generally a serious illness caused by the presence of bacteria and/or bacterial toxins in the blood (blood poisoning). 

In the case of life-threatening hydrogen sulfide poisoning, measurements of blood sulfide or urinary thiosulfate levels may be used to confirm exposure. However, samples need to be taken within two hours of exposure in order to be useful. The tests for measuring sulfide in the blood or thiosulfate in the urine are described in Section 2.7.1. 

Baker EL Jr, Landrigan PJ, Barbour AG, et al. 1979. Occupational lead poisoning in the United States Clinical and biochemical findings related to blood lead levels. Br J Ind Med 36 314-322. 

In animals, deaths from acrylonitrile have been reported in several species following inhalation, oral or dermal exposure. In most species, death appears to be related to cyanide poisoning. That the cyanide moiety is involved in human toxicity of acrylonitrile has been reported in a case study in which a human male was sprayed with acrylonitrile when a valve burst (Vogel and Kirkendall 1984). This individual suffered symptoms characteristic of cyanide poisoning, and treatments designed to reduce cyanide levels in the blood were required in order to save his life. 

The types of medical data that help accident investigations include (1) type and level of toxic or abusive substances in the blood, (2) location and magnitude of injuries, (3) type of poisoning (carbon monoxide, toluene, etc.), (4) signs of suffocation, (5) signs of heat exposure or heat exhaustion, and (6) signs of eye irritation. 

In that test tube, he now saw, the poison uric acid could exist in solution or as a precipitate. Its condition depended on pH and temperature, just as in an ordinary test tube, and in either event, whether in the blood or tissues, it produced disease. That deposits in the tissues would cause irritation was obvious enough, but the mechanism by which dissolved uric acid worked its havoc required some logical analysis. Since his migraine pain was aggravated by stooping and alleviated by applying pressure to the arteries of the neck, Haig deduced the immediate cause of the headache had to be elevated blood pressure. 

Nitrites may be used as an antidote for cyanide poisoning if given rapidly. They convert hemoglobin to methemoglobin, which binds cyanide in the blood before reaching the tissues. Oxygen is also given if possible. 

Aminolevulinate now leaves the mitochondria. In the cytoplasm, two molecules condense to form porphobilinogen, a compound that already contains the pyrrole ring. Porphobilinogen synthase is inhibited by lead ions. This is why acute lead poisoning is associated with increased concentrations of ALA in the blood and urine. 

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