Arterial lactate as a predictor of mortality in emergency department patients with paraquat intoxication

Context. Plasma paraquat concentration is recognized as the best prognostic indicator in patients with acute paraquat poisoning, but it cannot be measured in many hospitals due to limited medical resources. By contrast, arterial lactate is easily obtainable, even in local hospitals. Objective. To evaluate whether initial arterial lactate concentration is a good predictor of mortality in patients with acute paraquat poisoning. Materials and methods. A total of 272 patients with acute paraquat poisoning were admitted to the emergency department of Samsung Changwon Hospital from January 2005 to January 2011. Initial arterial lactate in the emergency department was compared in survivors and non-survivors. Initial arterial lactate and the Acute Physiology and Chronic Health Evaluation II (APACHE II) score system were compared by analyzing receiver operating characteristic (ROC) curves. Results. The overall rate of mortality was calculated to be 81.6%; 222 out of 272 patients died. The arterial lactate was higher in non-survivors (8.30 +/- 4.04 mmol/L) than survivors (2.81 +/- 1.95 mmol/L) (p < 0.001). The arterial lactate was found to be associated with a significantly higher risk of death in a multiple logistic regression (odds ratio (OR) = 7.02, 95% confidence interval = 2.06 -23.91, p = 0.002). For the ROC curve analysis, the arterial lactate had an area of 0.886 and the cut-off concentration was 4.4 mmol/L (sensitivity 82%, specificity 88%, the best Youden index was 0.7). The APACHE II score system had an area of 0.859 and the cut off was 9 (sensitivity 75%, specificity 84%, and the best Youden index was 0.59). Discussion and conclusion. The arterial lactate had a good predictive power in evaluating the prognosis of patients with acute paraquat poisoning. In the case of hospitals without facilities to test plasma paraquat concentration, measurement of the arterial lactate may be a simple and practical tool for assessing the severity of paraquat poisoning.