Medicine (Abingdon, England : UK ed.)最新文献

Blood coagulation is the result of a complex cascade of proteases that produce an insoluble fibrin polymer from soluble fibrinogen. Abnormal or excessive coagulation can cause venous thromboembolic disorders or arterial thromboembolic disease. Parenteral and oral anticoagulants have demonstrated efficacy in treating these conditions. Haemorrhage is a predicable consequence of anticoagulant poisoning. Treatment involves the general management of haemorrhage, and the administration of specific antidotes for individual anticoagulants is discussed. Complicated cases should be discussed with a haematologist and the UK National Poisons Information Service.

Accidental poisoning is most common in children, but deliberate self-harm becomes predominant in teenagers and early adulthood. The epidemiology of poisoning can be studied using mortality data, hospital admission rates and enquiries to poisons information services. Effective strategies for preventing suicide and reducing the risk of accidental poisoning require an understanding of the epidemiology of poisoning.

Around 150,000 people die each year from pesticide poisoning. Most deaths result from self-poisoning by ingestion, rather than occupational or accidental exposures, which are typically topical or inhalational. Severe pesticide poisoning is more common in rural lower- and middle-income countries where pesticides are widely used in smallholder agricultural practice and therefore freely available. Significant acute poisoning is much less common in industrialized countries; here the long-term effects of low-dose chronic exposure most concern the population. Poisoning from organophosphorus and carbamate insecticides causes most severe cases and deaths worldwide, although numbers are falling as the most highly toxic compounds are withdrawn from agricultural practice. Severe organophosphorus poisoning requires urgent resuscitation and administration of oxygen, atropine and oximes. Paraquat and aluminium phosphide are major problems in some countries, with case fatality usually >50% and no effective treatments. Newer pesticides that have become widely used over the last 30 years, for example neonicotinoid and phenylpyrazole insecticides, are more selective in their toxicity to pests, resulting in far less acute human toxicity and few deaths. Toxicity can result from solvents rather than the pesticide's active ingredient. Acute poisoning with newer pesticides usually requires only careful supportive care.

Cardiovascular poisoning may be significant from toxicity related to β-blockers, calcium channel blockers and digoxin. Various treatment options exist that are based on the pharmacological pattern of toxicity from these drugs. These include supportive clinical care and the use of specific antidotes.

Lead can be absorbed after inhalation or ingestion and is toxic to most organ systems. Management involves avoidance of exposure and, in more severe cases, chelation therapy with either sodium calcium edetate or dimercaptosuccinic acid. Iron poisoning causes metabolic effects in proportion to the concentrations of free iron, although individual responses vary. Toxicity is therefore related to the dose ingested. Iron concentrations can rise and fall, making plasma concentrations difficult to interpret in acute poisoning. Clinical features include severe gastrointestinal irritation, cardiovascular collapse and direct organ damage to the liver and kidneys. Unconsciousness occurs in severe cases. The chelating agent desferrioxamine is used as the antidote, although uncertainty remains over the optimal dose in individual patients. Chelating agents are also used in other metal poisonings. It is advised that the investigation and management of suspected heavy metal poisoning should be conducted in consultation with a poison centre and/or a clinical toxicologist.

Exposures to household products are common. Most of these exposures are accidental, causing minimal symptoms. Serious toxicity is possible if large amounts or high concentrations of products are involved.

Anticonvulsant medications are used in the treatment of epilepsy as neuropathic pain, migraine and psychiatric illness. Anticonvulsants suppress neuronal excitation to reduce the likelihood of seizure activity. Generally, management is supportive, with correction of physiological and metabolic parameters. Drug concentrations can help guide specific treatments such as l-carnitine (for valproate) and multiple-dose activated charcoal (for carbamazepine, phenytoin and phenobarbital). Extracorporeal treatments can be used to enhance elimination.

Poisoning caused by a large range of drugs and chemicals can induce metabolic complications via many different mechanisms. Some metabolic complications are life-threatening but all require careful assessment, appropriate monitoring and consideration of treatment. Prompt diagnosis and management reduce morbidity and mortality. Treatment may be targeted to the specific poisoning, and can be time-critical, or can follow approaches similar to those of general and acute medicine. This review introduces metabolic complications associated with sodium, potassium, metabolic acidosis, rhabdomyolysis and methaemoglobinaemia.

Paracetamol overdose is common. If left untreated, liver and/or renal failure can develop. Administration of the antidote, acetylcysteine, within 8–10 hours of overdose minimizes or prevents liver damage. After overdose, the tests used to identify that patients are at risk of liver injury are well established but have limitations. Once liver injury has occurred, important prognostic factors are the presence of hepatic encephalopathy, the international normalized ratio, acid–base status and renal function. The only treatment for acute liver failure is transplantation.