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Poisonings may be caused by any kind of chemical compounds or liquids for technical used adopted in technique, agriculture and household. Medicines may cause poisonings too. All poisonings are divided into professional, household and medical ones. We are going to overview the first aid in cases of medical poisonings. But they are effective in other cases too.
Most frequent medical poisons are sleeping pills, analgesics, neuroleptics, antiseptics, cardiac glycosides, anti-cholinesterase agents etc. The pattern and severity of poisoning depends on its agent action. Thus, anti-cholinesterase agents poisoning (caused by phosphoorganic compounds) is characterized by cholinergic system enhanced symptoms. Alcohol, sleeping pills and drug intoxications are characterized by deep CNS depression.
Organism conditions and the way of poison entrance (oral, inhalation, skin, and mucous coat absorption) determine the severity of symptoms as well as the way of first aid. Children and elderly people are extremely sensitive to poisons and demonstrate the cases of the most severe poisonings. Environmental factors like temperature, humidity and atmospheric pressure influence the poison activity too.
There are general and specific first aid means. They are designed to achieve the following results.
• Prevention of further poisons absorption
• Chemical neutralizing of the absorbed poison or its elimination with a specific antidote
• Enhanced poisons extraction
• Normalizing of organisms function by symptomatic therapy
The sooner you begin the first aid, the more chances of success you have. Each case may need the adjustment of therapeutic pattern depending on the type and severity of poisoning. Thus, abrupt respiratory depression claims urgent restoring of the gas exchange system functions.
In the treatment of poisonings an important place is engaged by antidote. Antidote is an agent that neutralizes a poison or counteracts its effects. There are a few types of antidotes. Chemical antidote is a substance that unites with a poison to form an innocuous chemical compound (unithiol, chelating compounds). Mechanical antidote is a substance that prevents the absorption of a poison (activated carbon). Physiologic antidote is an agent that produces systemic effects contrary to those of a given poison.
Prevention of poisons absorption
The pattern of these actions depends on the way the poison entrance into the organism. Inhalation poisonings (caused by carbon monoxide, nitric oxide, insecticides aerosols, petroleum evaporations) claim immediate removal of patient from the danger zone. Poisons should be removed or washed away from skin and mucous coats. Oral intake of poisons is managed by stomach rinsing (lavage). The early it is done, the more effective it is. Repeated rinsing help in cases of poisoning with hard-soluble powders and tablets that stay in stomach for a couple of hours.
Inactivation and binding of the poison in the stomach should be performed simultaneously to rinsing. Potassium permanganate, tannin, activated carbon, egg whites and milk are used for these purposes.
Potassium permanganate causes the oxidation of organic poisons. However it is unable to react with inorganic compounds. Its water solution ratio is from 1:5000 to 1:10000. It should be removed from stomach right after the rinsing due to its irritating properties.
Activated carbon (charcoal) is a universal adsorbent. Water suspension, containing 20-30 g of activated carbon, is to be poured into the stomach. After the interaction with poison the suspension should be quickly evacuated with the help of laxatives due to possible release of poison.
Tannin sediments various poisons especially alkaloids. 0.5% solution of tannin is usually used. Removal of the suspension due to possible poison release is necessary also.
Eggs white form insoluble complex with poisons. Milk acts in the same way but it is contradicted in case of poisonings by fat-soluble agents.
Vomiting agents may be used in cases of impossibility of the gastric rinsing. Apomorphine hydrochloride (0.5-1 ml of 0.5-1% injected subcutaneously) is used most frequently. It is contradicted in case of patients unconsciousness.
Salt laxatives (sodium and magnesium sulfate) are used for poison removal from intestines. Sodium sulfate is better then magnesium sulfate, because the latter causes CNS depression.
Chemical neutralization of the absorbed poison and usage of specific antidotes
There are certain compounds capable for neutralization of poison toxicity by chemical binding or functional antagonism. They act by chemical or functional interaction with poisons. Unithiol, sodium thiosulfate, complexones, methemoglobin-formers and demethemoglobin-formers are the examples of chemical concurrence interaction.
Unithiol (dimercaprol) can bind metal ions, metalloids and cardiac glycosides molecules due to it two sulfhydryl groups (-SH), which can donate electrons for coordination with the poison. Such bonding effectively prevents interaction of the metal with similar functional groups of enzymes, coenzymes, cellular nucleophiles, and membranes. Usually this medicine is used in cases of poisonings by arsenic, mercury and gold. It is less effective against bismuth, cobalt, cooper, zinc, nickel, polonium and cardiac glycosides. Complex of unithiol and poison is excreted by kidneys. Given intramuscularly, unithiol is readily absorbed, metabolized, and excreted by the kidney in complex with poison within 4-8 hours. Adverse effects include hypertension, tachycardia, vomiting, salivation, fever (particularly in children), and pain at the injection site.
Sodium thiosulfate is an antidote in arsenic, mercury, lead, and cyanide poisoning. Sodium thiosulfate forms with metals nontoxic sulfites and with cyanides less toxic substances. Its 30% solution is injected intravenously.
Complexons make chelate compounds with most of metal ions and radioactive isotopes. These substances have low toxicity and are being extracted by kidneys. Tetacine-calcium (EDTA, edetate calcium disodium), the calcium chelate of edetate (ethylenediaminetetraacetate) disodium, is a chelating agent (complexon). The calcium in calcium EDTA can be displaced by divalent and trivalent metals, particularly lead, to form stable soluble complexes which can then be excreted in urine. Administration of calcium EDTA chelates greatly increases the urinary excretion of zinc, cadmium, manganese, iron, and copper. The manufacturer recommends that calcium EDTA injection be diluted with 0.9% sodium chloride or 5% glucose injection for intravenous administration. Calcium EDTA is used for the reduction of blood and mobile depot lead in the treatment of acute and chronic lead poisoning and lead encephalopathy. Agent may also be beneficial in the treatment of poisoning from other heavy metals such as chromium, manganese, nickel, zinc, and possibly vanadium. The principal and most serious toxic effect of calcium EDTA is renal tubular necrosis, which tends to occur when the daily dose is excessive and may result in fatal nephrosis.
Penicillamine is a monothiol-chelating agent, which is a degradation product of penicillins. Penicillamine chelates copper, iron, mercury, and lead to form stable soluble complexes, which are readily excreted by the kidneys. Copper is chelated by the combination of 2 molecules of penicillamine with 1 atom of the metal. Penicillamine is readily absorbed from the GI tract. Penicillamine is used to promote excretion of copper in the treatment of Wilson's disease (hepatolenticular degeneration). Also it is used in the treatment of the active stage of rheumatoid arthritis. The mechanism of action of penicillamine in the treatment of rheumatoid arthritis is not known but may be related to inhibition of collagen formation. Adverse reactions include allergic reactions, nausea, leukopenia, and proteinuria.
Deferoxamine chelates iron by binding ferric ions to its molecule. Deferoxamine-iron complex is formed in many tissues, but mainly in plasma; this complex is stable, water soluble, and readily excreted by the kidneys. Deferoxamine appears to have a specific affinity for iron; this affinity is greater than that of other chelating agents for iron. Deferoxamine is used in the treatment of acute iron intoxication as well as chronic iron overload.
Demethemoglobin-formers are the substances capable of converting methemoglobin to hemoglobin. They are methylene blue (as a chromosmone medicine) and cystamine. Methylene blue reduces methemoglobin to hemoglobin. It is administered to patients who have been exposed to methemoglobin-forming compounds (e.g., aniline, nitrites, local anesthetics, sulfanilamides) and whose methemoglobin levels exceed 20 to 30%. However, in higher doses methylene blue promotes methemoglobin forming that can be used for the treatment of cyanide poisoning.
Physiologic antidote as it is mentioned above is an agent that produces systemic effects contrary to those of a given poison. Antidotes can concurrent with poison for the same substrate e.g., receptor, enzyme (functional antagonism). For example phosphoorganic substances inactivate an enzyme acetylcholinestarase that leads to exceed accumulation of acetylcholine. Cholinesterase reactivators (dipyroxime, isonitrosine) bind with phosphoorganic substances and release acetylcholinesterase. Cholinoblockers (atropine) remove cholinomimetics (muscarine, pilocarpine) on M-cholinoreceptors; thus atropine is useful during muscarine poisoning. The same concerns histamine and anti-histamine substances, adrenoblockers and adrenomimetics, morphine and nalorphine.
Enhanced poison extraction
That is achieved by organisms purifying. Large amounts of liquid and diuretics are to be taken (forced diuresis). It causes the dilution of poison in tissues and decreases its concentration while osmotic diuretics and furosemide enhances its renal excretion. Drinks are given to conscious patients; unconscious ones receive 5% glucose solution or isotonic sodium chloride solution intravenously. This method is effective only when kidneys are still capable of excretion. Alkaline diuresis may aid in increasing renal clearance and reducing the elimination half-life of salicylates and phenobarbital (acids), because the reabsorption of acids at alkaline pH is lower. And on the contrary, alcohol and amphetamine (alkaline compounds) are better excreted with acidic urine that can be achieved by using of ammonium chloride.
Extracorporeal techniques include hemodialysis, hemoperfusion, etc that are used for different kinds of poisonings.
During the procedure hemodialysis of soluble substances and water from the blood by diffusion through a semipermeable membrane is appearing. The separation of cellular elements and colloids from soluble substances is achieved by pore size in the membrane and rates of diffusion. Hemodialysis is especially effective in case of kidney insufficiency (sulema poisonings). It promotes the evacuation of poisons with small molecular weight.
Hemoperfusion (hemosorption) is a detoxicative method. It consists of blood passage through columns of adsorptive material, such as activated charcoal (carbon), to remove toxic substances from the blood. It is active against poisons, diluted in blood. Hemoperfusion is useful for intoxication with a drug known to be metabolized to a more toxic one and a drug known to produce delayed toxicity.
Peritoneal dialysis is a removal from the body of soluble substances and water by transfer across the peritoneum, utilizing a dialysis solution which is intermittently introduced into and removed from the peritoneal cavity. Transfer of diffusable solutes and water between the blood and the peritoneal cavity depends on the concentration gradient between the two fluid compartments. Acute peritoneal dialysis is used principally to treat patients with acute renal failure.
Supportive care (symptomatic therapy)
Morbidity and mortality following an overdose are reduced by intensive appropriate symptomatic supportive therapy, which includes restoring of vital functions (cardiac status, airway, and mental status).
Respiratory depression claims endotracheal intubation, bronchial cleaning and artificial lung ventilation. Respiratory centre depression is managed by analeptics (camphor, bemegride). Respiratory depression caused by morphine is can be treated by naloxone or nalorphine. Pulmonary edema is treated with complex therapy according to blood pressure rate. Spirit and antifoamsilane inhalations are performed to manage the foam; glucocorticoids, diuretics and ganglioblockers are given depending on the indications. Bronchospasm can be managed by broncholytics (adrenomimetics, cholinoblockers, euphylline, etc). Hypoxia is managed by oxygen inhalation and special apparatus for respiration and blood circulation support.
Cardiac insufficiency claims glycosides with a quick onset of action (strophantine, corglycon); antiarrhythmics are used in cases of arrhythmia.
Vascular tonus and blood pressure are decreased during most of poisonings. Hypotonia causes tissue nutrition disorders, hypoxia, and poison retention. Hypotonia is managed with adrenomimetics (e.g., dopamine, ephedrine, adrenaline, mesatone, and noradrenaline). Hypertension (poisoning by vasoconstrictors) is the indication for the using of clopheline, magnesium sulfate, phentolamine, benzohexonium, furosemide, etc.
Cholinomimetics and CNS agitators often cause cramps. They are managed with narcosis agents, tranquilizers (diazepam), barbiturates (thiopental), muscle relaxants, and magnesium sulfate.
Allergic reactions and especially anaphylactic shock first aid is urgent injections of adrenomimetics (adrenaline), glucocorticoids (prednisolone), anti-histamines (dimedrol), broncholytics (euphylline), and cardiac glycosides (strophantine).
Coma is the symptom of severe poisonings. It is prefer for the poisoning by CNS depressants. Treatment is designed to support vital functions. Analeptic use should be extremely cautious in these cases. Pain syndrome claims narcotic analgesics, which can inhibit the respiratory centre on the other hand.
The support of acid-base balance and liquid-salt balance are extremely important in cases of poisonings therapy. Acidifying and alkalinizing agents, salt solutions are discussed in chapter “Plasma substitutes and deintoxication solution”.
Thus, first aid means depend on the kind of poisoning and patients state.