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Troublesome toxins
  1. A Parfitt,
  2. J A Henry
  1. Academic Department of Accident and Emergency Medicine, Imperial College School of Medicine, St Mary's Hospital, London W2 1NY, UK

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    The treatment of patients with acute poisoning admitted to the emergency department is discussed

    Acute poisoning now accounts for about 3%–5% of emergency department attendances in most countries with developed medical services.1,2 Each patient presents a challenge to the skills of the doctor, who has to deal not only with the toxic effects of the poison but also with the mental state of the patient, anxious parents, friends or relatives. Because of this, many doctors find the poisoned patient more difficult to deal with than a “straightforward” medical or surgical case. Here we consider a few current topics in poisoning.

    GASTROINTESTINAL DECONTAMINATION

    Some junior doctors still think that a decision not to empty the stomach might lead to an appearance in the coroner's court. However, there is no evidence that reducing absorption of ingested toxins shortens the duration of admission to hospital or saves life.3 Syrup of ipecacuanha, although an effective emetic, does not effectively empty the stomach and should not be used. Gastric lavage also has drawbacks and may force poisons through the pylorus into the proximal small intestine.4 Consensus of expert opinion in Europe and the USA considers activated charcoal the preferred treatment for most poisons within one hour of ingestion.2,3 Karim et al have recently drawn attention in this journal to time constraints in the administration of charcoal, while Wolseley et al in the USA have noted that patients brought to hospital by ambulance are given charcoal earlier after arrival.5,6 The other treatment deserving consideration in special circumstances is whole bowel lavage, which uses a large amount of isotonic fluid (as in bowel preparation for radiological procedures) to empty the gut by “flushing out” the intestinal contents. This technique is of special use for sustained release preparations (such as lithium, theophylline, and propranolol), heavy metal compounds, iron, and illicit drug packets in body packers.7–10 The technique is less disturbing to the patient than might be imagined and flavoured formulations exist for children. This brief look at methods of intestinal decontamination will hopefully encourage hospital doctors to revise their knowledge concerning the appropriate methods for use in their own environment.2,3

    CLINICAL ISSUES IN PARACETAMOL POISONING

    Paracetamol is still the commonest substance taken in overdose in Britain, and in many places paracetamol ingestion forms 50% of all poisoning cases seen.2 Despite a clear exposition on management in the British National Formulary and the availability of guidelines and posters from the British Association for Accident and Emergency Medicine, paracetamol remains the commonest cause of enquiries to the United Kingdom National Poisons Information Service in both adults and children.11,12 It is important to be aware that the great majority of overdose cases will be asymptomatic when seen, so that every patient requires a plasma paracetamol level at least four hours after ingestion in order to decide on the need for treatment.

    What are the main things that the “doctor at the door” needs to know about paracetamol? Firstly, that we have highly effective antidotes, provided they are given within about 10 hours of ingestion. Secondly, the decision to treat is based on a nomogram involving time since ingestion of a single overdose and the plasma paracetamol level. Thirdly, that it is safer to give the antidotes than not to give them unless one can be completely sure of the history, the timing of ingestion and the blood level—if there are confounding issues, such as a staggered overdose or an unreliable history, the patient must be treated. And fourthly, one has to determine whether the patient falls into a “high risk” category, so that the patient must be treated at lower blood paracetamol levels as the current guidelines indicate. Knowledge of these simple facts alone should enable the great majority of cases to be treated effectively without the need for further advice.

    CARBON MONOXIDE

    Carbon monoxide is still the commonest cause of poisoning deaths in the United Kingdom. In the emergency department, acute and subacute exposure are important presentations to recognise and treat. Many departments in the UK wisely teach on the common and non-specific symptoms that result from poisoning at the start of the winter months. Treatment is controversial. Publication of the first double blind trial of hyperbaric oxygen in carbon monoxide poisoning in the Australian Journal of Medicine has cast doubt on the usefulness of hyperbaric therapy,13,14 but a further study as yet only published in abstract form is likely to show that it is effective (LK Weaver, et al, UHMS Annual Scientific Meeting Session Texas, 2001). Many recommend hyperbaric oxygen in those who have lost consciousness, those with a blood carboxyhaemoglobin over 20% on arrival, the pregnant patient and those with neurological or electrocardiographic changes. Hyperbaric centres are available for expert consultation and generally rely on the clinical picture to reach a decision regarding treatment.

    CYANIDE

    Although rare, acute cyanide poisoning requires immediate action. Many patients suffering from smoke inhalation or burns may also have cyanide toxicity, and may present with a metabolic acidosis not responding to oxygen administration. Different antidotes are used in different countries, cobalt edetate (UK) and sodium nitrite (USA) are the commonest, each with its drawbacks, while sodium thiosulphate is slower acting but harmless. There is now a further antidote, hydroxocobalamin.15,16 This drug should be more widely used because it may be especially useful in patients with smoke inhalation, as it is not toxic and can be given outside the hospital.

    CONCLUSION

    The scene changes from time to time. We have tried to point out a few of the developments in poisoning where changes are taking place. Hippocrates is reputed to have said “Primum non nocere” (first of all do not cause harm). Many dramatic interventions are available, but the risk-benefit balance has to be borne in mind so that the patient recovers as a result of good medicine.

    The treatment of patients with acute poisoning admitted to the emergency department is discussed

    REFERENCES

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