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Abstract
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In the minds of many doctors, exposure to a substance is equated with poisoning. However, uptake is necessary for there to be a toxic effect and, even if this occurs, poisoning does not necessarily result, because the amount absorbed may be too small to produce adverse effects. Moreover, to many, the term poisoning suggests an acute event demanding immediate care and attention. This is often so, but the consequences of exposure are not always immediate. For example, distinctive sequelae may not appear until many years have elapsed, as is the case with hepatic haemangiosarcoma from vinyl chloride exposure. Alternatively, features may arise only after prolonged exposure, as with many heavy metals.
In many hospitals in developed countries, poisoning is one of the most common reasons for acute admission to adult medical wards. In such cases, poisoning usually involves self-administration of a prescribed or over-the-counter medicine or an illicit drug. Most patients have taken (usually ingested) more than one drug, and alcohol is the most commonly implicated second agent. Substances may also be administered deliberately to cause harm, or for financial or sexual gain. Sometimes, poisoning is iatrogenic (e.g. digoxin toxicity). Occupational poisoning is common in developing countries and continues to occur in the developed world. Poisoning in young children is usually accidental. It may be iatrogenic in those aged below 6 months, involving, for example, over-treatment with paracetamol.
When poisoning occurs, the ensuing clinical syndrome may be distinctive. For example, fixed dilated pupils, exaggerated tendon reflexes, extensor plantar responses, depressed respiration and cardiac arrhythmias suggest tricyclic antidepressant poisoning. However, with many psychotropic drugs there may be only nonspecific CNS depression, respiratory impairment and hypotension.
Management of poisoning should never be confined solely to the poison and its effects. Most cases of self-poisoning do not require intensive medical treatment, but all patients require a sympathetic and caring approach, psychiatric and social assessment and, sometimes, psychiatric treatment. All the circumstances surrounding the episode must be taken into account, particularly when litigation may follow (e.g. after an occupational accident with a chemical). It is therefore important that the clinician, having instituted any necessary life-saving measures, should take a careful history, retain all pertinent evidence (e.g. suicide note) and make a meticulous record of symptoms, signs, progress and outcome. |