Rapid analysis of plasma paraquat using sodium dithionite as a predictor of outcome in acute paraquat poisoning.

BACKGROUND: Paraquat poisoning can be lethal, and aggressive treatments might have little or no effect on severely poisoned patients. Accordingly, a convenient prognostic test is necessary to guide therapy for acute paraquat poisoning. Sodium dithionite reduces paraquat to a blue radical form in alkaline plasma with a paraquat detection sensitivity of 2.0 mg/L, which is a 100% lethal concentration at 10 to 12 hours postingestion. The prognostic utility of this simple reaction was examined prospectively. METHODS: Of 233 paraquat-poisoned patients, who were taken to the hospital within 12 hours after ingestion, the plasma samples obtained on arrival were tested using the sodium dithionite reaction. Standard saline containing 2.0 mg/L paraquat was used as the positive control. The test result was interpreted as being positive when the plasma test yielded a blue color darker than that of the positive control. The effects of aggressive treatment, including cyclophosphamide pulse and continuous venovenous hemofiltration, were evaluated retrospectively. RESULTS: The discharge survival rate was 41.6% (97 of 233). Ninety-seven of 142 patients with negative or equivocal plasma dithionite test survived. However, all 91 patients with positive plasma dithionite test died of multiorgan failure. Cyclophosphamide and/or continuous venovenous hemofiltration could not improve survival. CONCLUSIONS: In this single-center study, a positive plasma dithionite test was associated with 100% mortality, despite aggressive treatment. In contrast, negative or equivocal tests were associated with a 68% survival rate. It is believed that after further verification, this test can be used to guide therapy and predict the outcomes of patients suffering acute paraquat poisoning.