Diagnosis of Acute Poisoning
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MAIN TOPIC Diagnosis of acute poisoning As all chemicals can act as poisons in the right quantity, effective lines of communication between the attending clinician or health worker, the laboratory and the toxicologist are essential. Virtually all known chemicals can rating (LD50 < 400 mg/kg), 2 is edible’ substances ingested acci- cause injury or death, depending intermediate (LD50 of 400 - 4 000 dentally is usually small. The aver- on the dose of the substance. The mg/kg), and 1 is low (LD50 of age quantity of liquids swallowed lethal dose may vary widely. For 4 000 - 40 000 mg/kg). Safety, the accidentally by a child under the example, 4 000 mg/kg of table salt opposite of risk, is the probability age of 5 years is 5 ml, and that by will be lethal to 50% of a popula- that harm will not occur under an adult 15 ml. In contrast, the tion of experimental animals specified conditions.2,3 quantity swallowed intentionally (expressed as the LD50), while the (by adults) is usually considerably LD50 of arsenic trioxide is 1 - 2 larger, and should be taken into mg/kg, and that of botulinum toxin consideration when potential haz- 0.00001 mg/kg. A number of fac- Virtually all known ard or risk is assessed. tors may contribute to toxicity: chemicals can cause Table I lists the most frequently physico-chemical characteristics injury or death, ingested household agents consid- such as the pKa, lipid solubility, ered ‘usually non-toxic’. This table the route of entry (e.g. orally or depending on the is intended as a guide only, and percutaneously), the nature of the dose of the sub- should be used in conjunction with exposure (e.g. acute or chronic) the information given above.4,5 and the susceptibility of the victim. stance. This refers to factors such as the For clinical purposes, poisons state of fetal development, child- (including therapeutic drugs) may ‘Non-toxic ingestion’ refers to the hood, advancing age and underly- be divided into two broad cate- consumption of a non-edible agent ing pathology. In addition, the gories: or product usually not associated vehicle in which the agent is dis- with harmful effects. The practical solved or suspended, and other • Poisons (and their metabo- value of knowing that a product is formulation factors, may markedly lites) which directly cause ‘usually non-toxic’ prevents: influence toxicity. There is no irreversible or slowly reversible structural or entirely ‘safe’ chemical since all • an inappropriate response that functional tissue damage in have the potential to cause death causes panic and injury under specific circum- one or more organ systems. • over-treatment of the patient stances. It should also be empha- These are also considered com- • unnecessary visits to the doctor sised that some adverse reactions pounds with a high inherent or hospital emergency facility.4 to chemicals, such as allergic and toxicity (Table II). Arsenic and idiosyncratic reactions, are not For an agent to be considered the organophosphates are good dose-related.1,2 ‘usually non-toxic’, it should meet examples of poisons which may the following criteria: cause irreversible damage, long- In practice the critical factor is not lasting (slowly reversible) organ • positive identification of the whether or not a substance is poi- dysfunction, or lead to compli- product, its ingredients, and its sonous, but whether someone is at cations which may require concentration risk from exposure to it. Risk is extended periods of supportive the probability that a substance • positive assurance that it was therapy. Significant symptoms 1,4 will cause harm under specified the only product ingested. and signs of a substantial num- conditions. This is reflected in a Because of unpleasant or disagree- ber of poisons in this group may hazard rating on a scale of 1 - 3, able tastes, the quantity of ‘non- appear late (1 - 3 days post where 3 indicates a high hazard 438 CME August 2003 Vol.21 No.8 Table I. Most frequently ingested household agents considered ‘usually non-toxic’4 Abrasives Detergents (phosphate type, anionic) Lozenges (without local anaesthetic) Shampoos (non-pediculicides) Adhesives Deodorants Lubricant Shoe polish (most do not con- Antacids Deodorisers (spray and refrigerator) Lubricating oils (lipid pneumonia tain aniline dyes) Antibiotics (most) when aspirated) Sesame oil Eye make-up Silica Baby products, cosmetics Magic markers Silly putty (99% silicones) Ballpoint pen inks Fabric softeners Make-up (eye, liquid, facial) Soap and soap products Bathtub floating toys Fertiliser (if no insecticides or herbicides Matches Suntan preparations Bath oil (castor oil and perfume) added) Mineral oil (unless aspirated) Sweetening agents (saccharin, Bleach (< 3.5% hypochlorite) Fish bowl additives Motor oil cyclamate) Body conditioners Bubble-bath soaps Glues and pastes (for wood or paper) Newspaper Talc (not inhaled) Golf ball (core may cause mechanical Teething rings (containing Calamine lotion injury) Paint (indoor or latex) water, if sterile) Calcium sulphate Greases Pencil (lead, graphite, colouring) Thermometers (elemental mer- (plaster of Paris) Perfumes cury or alcohol) Candles (beeswax or Hair products (dyes, sprays, tonics) Peroxide 3% Toilet water paraffin) Hand lotions and creams Pet food Toothpaste (with or without Caps (toy pistol, potas- Homeopathic medication (excl. herbal Petroleum jelly (Vaseline) fluoride) sium chlorate) medicines) Phenolphthalein laxatives (Brooklax) Chalk (calcium carbonate) Hydrogen peroxide (medicinal 3%) Plasticine Vaseline Charcoal Play-Doh Vitamins (without iron) Cigarettes or cigars (nicotine) Ice bricks (water and edible thickener) Polaroid picture coating fluid Clay (modelling) Incense Porous-tip ink marking pens (koki) Water colours CME Colognes Inedible markers Prussian blue (ferricyanide) Contraceptives Ink (black and blue — non-permanent) Putty (less than 60 g) Zinc oxide Corticosteroids Iron filings (chemical sets) Zirconium oxide August 2003 Vol.21 No.8 August 2003 Vol.21 Cosmetics Rouge Crayons (marked ‘non-toxic’) Lanolin Rubber cement Laxatives MAIN TOPIC Dehumidifying packets Lipstick (silica or charcoal) Adapted from Ellenhorn and Barceloux,4 with permission 439 MAIN TOPIC exposure). At this stage symp- which are rapidly and com- maintenance of normal respira- toms may not be expected, or pletely reversible. Although tory, circulatory and renal func- the incident may have been par- many agents in this category tion with monitoring of blood tially forgotten. This can mean have the potential to cause gases, acid/base balance, serum that the patient and/or doctor serious organ dysfunction or electrolyte and glucose levels, may not immediately (if at all) even death, appropriate support- etc. Benzodiazepines and opi- associate the cause of the symp- ive care during the acute phase ates taken in overdose, and even toms with exposure, leading to will ensure complete recovery in strychnine, are examples of poi- delayed optimal therapeutic most instances. Fortunately, sons with a relatively low inher- intervention. Examples include most potential poisons dealt ent toxicity. paracetamol and Amanita phal- with in the clinical setting fall When dealing with a suspected loides poisoning. into this category. Consequently, case of poisoning, one of the main • Poisons which do not cause most poisoned patients require priorities should be to attempt to tissue damage directly or treatment of symptoms and identify poisons with a high inher- which cause toxic effects appropriate supportive care ent toxicity as soon as possible only. ‘Supportive care’ is the Table II. Examples of drugs and poisons with a high inherent toxicity* Drug or poison Specific treatment† Reason for early antidotal/ active removal therapy Carbon monoxide‡ Oxygen Tissue damage (nervous system) Cyanide‡, § Oxygen. In serious poisoning: Extremely toxic, often with a morbid course and sodium nitrite/sodium thiosulphate death or Kelocyanor (Restan) Digoxin Digoxin-specific antibodies With massive overdose poisoned membranes can no longer maintain electrolyte gradients; this leads to extremely high potassium levels Ethylene glycol‡, ¶ Ethanol, haemodialysis Tissue damage (nervous system, kidney) Isoniazid‡ Pyridoxine, haemodialysis Tissue damage (nervous system) Lithium carbonate** Haemodialysis Tissue damage (nervous system, kidney) Metals and metalloids Arsenic** Dimercaprol, penicillamine Tissue damage (nervous system, liver, kidney) Tissue damage (gastrointestinal, liver, CVS) Iron‡, ** Deferoxamine Tissue damage (nervous system) Lead** Dimercaprol, calcium disodium Tissue damage (nervous system, kidney) edetate Mercury** Dimercaprol, penicillamine Methanol‡, ¶ Ethanol, haemodialysis Tissue damage (nervous system, blindness) Methyl bromide Dimercaprol, N-acetylcysteine Tissue damage (nervous system, CVS, kidneys) Mushrooms — cyclopeptides as in Silibinin Tissue damage (liver, kidney, heart, pancreas) Amanita phalloides** Organophosphates** Obidoxime chloride, atropine To prevent extended periods of intensive care Paracetamol N-acetylcysteine Tissue damage (liver, kidney) Paraquat (diquat)**, †† Immediate, aggressive Multisystem failure (kidney, liver, nervous decontamination procedures plus system, heart, lungs) activated charcoal or a watery slurry of clay Salicylates‡ Haemodialysis Tissue damage (nervous system) Theophylline‡, ** Haemoperfusion Tissue damage (nervous system) *Examples are those in which antidotes or special toxin removal procedures may prevent permanent tissue damage or serious complications (paraquat