Paraquat poisoning: clinical features and immediate general management

Abstract

1 In contrast to 10-15 years ago most cases of paraquat poisoning are now due to deliberate self-poisoning with parasuicidal or suicidal intent rather than to accidental ingestion. Less commonly, poisoning may follow careless handling of paraquat during occupational use. Although paraquat can be absorbed through the skin if improperly handled, poisoning usually follows ingestion and has rarely been reported after subcutaneous, intravenous or intraperitoneal injection. 2 Clinically, three degrees of intoxication may be distinguished. (a) Mild poisoning occurs after the ingestion or injection of less than 20 mg of paraquat ion/kg body weight. In these cases patients are either asymptomatic or symptoms are confined to the gastrointestinal system. All patients recover fully. (b) Moderate to severe poisoning usually follows the ingestion (rarely injection) of 20-40 mg of paraquat ion/kg body weight. Non-specific symptoms of ill health together with local gastrointestinal symptoms precede the development of renal failure (which may recover spontaneously) and pulmonary fibrosis which may not be manifest for days or weeks. Death occurs in the majority of cases but is usually delayed for 2-3 weeks. (c) Acute fulminant poisoning follows the ingestion of substantial quantities of paraquat (> 40 mg of paraquat ion/kg body weight). In addition to local symptoms, multiple organ (cardiac, respiratory, hepatic, renal, adrenal, pancreatic, neurological) failure occurs. Death may supervene within hours and is never delayed for more than a few days. 3 Initial general management has four priorities. Firstly, fluid loss should be replaced; secondly, the prognosis should be determined by measurement of the plasma paraquat concentration; thirdly, symptoms due to ulceration of the oropharynx must be relieved; fourthly, supportive care for patients and relatives must be provided. 4 Experience suggests that management of the terminally ill patient with acute fulminant poisoning is a far greater clinical challenge to medical and nursing expertise than simply the employment of methods to prevent absorption or increase elimination of paraquat.