Key investigations
Key investigations for paraquat poisoning are:
- full blood count
- coagulation studies
- serum electrolyte, urea and creatinine concentrations
- liver biochemistry
- blood gas analysis
- blood lactate concentration
- chest X-ray if aspiration pneumonitis, or acute pneumonitis (due to paraquat), or other respiratory pathology is suspected
- electrocardiogram (ECG).
A qualitative urine assay can be done to test for paraquat exposure. The assay involves adding 1 mL of sodium dithionite 1% solution to 10 mL of alkalinised urine. There is also a bedside test kit available that contains 2 g of sodium bicarbonate and 1 g of sodium dithionite, which are added to 10 mL of urine1. Both tests are positive for paraquat exposure if the solution colour changes to blue. The degree of colour change has been used in a semiquantitative way to predict toxicity. An early negative result does not preclude paraquat poisoning, but if the result is negative on urine passed 2 to 6 hours after ingestion, significant exposure is unlikely.