Peripheral burning sensation: a novel clinical marker of poor prognosis and higher plasma-paraquat concentrations in paraquat poisoning

Introduction: Self-poisoning with paraquat has a case fatality ratio (CFR) over 65% in Sri Lanka. Plasma-paraquat concentration is the best prognostic indicator for patient outcome but is not readily available. Alternative surrogate clinical markers could be useful in management and determining prognosis. Anecdotal reports by medical and research staff suggested that patients who complained of burning sensation of the body had a poor prognosis and a prospective study was initiated. Methods: This was a prospective observational study in three hospitals in Sri Lanka. We collected demographic data, presence or absence of burning sensation, and major outcome, and determined the plasma-paraquat concentration within 24 h post-ingestion. Results: There were 179 patients with deliberate self-ingestion of paraquat over 30 months. Burning sensation was reported in 84 patients (48%), which was initiated at a median of 1 day (range 1–3 days) postingestion. Of the patients who had burning, 61 died [CFR = 72.62%; 95% confidence interval (CI) = 62–81]. Of the 91 patients who had no peripheral burning, 23 died (CFR = 25.27%, 95% CI = 18.15–35.9). Presence of peripheral burning sensation was associated with a significantly higher risk of death (odds ratio = 7.8, 95% CI = 3.9–15, p < 0.0001). Patients who complained of peripheral burning died at a median of 36 h (interquartile range = 30.5–88) following ingestion whereas those who had no peripheral burning died at a median of 50.5 h (interquartile range = 16.75–80). The difference was not significant (p > 0.05). Median admission plasma-paraquat concentration in patients with peripheral burning (2.67 μg/mL, 95% CI = 0.84–14.2) was significantly higher than in the patients with no peripheral burning (0.022 μg/mL, 95% CI = 0.005–0.78; p < 0.001). Peripheral burning has a sensitivity of 0.72 (95% CI = 0.6–8) and specificity of 0.74 (95% CI = 0.64–0.08) and a positive predictive value of 0.73 (95% CI = 0.6–0.8). Discussion: It is possible that this symptom may help discriminate between patients who have poor chance of survival and those who may potentially benefit from interventions. The mechanism is not clear but could either include a direct concentration-related effect or be a marker of oxidative stress. Conclusion: Presence of burning sensation is associated with high plasma-paraquat concentrations and is strongly predictive of death