Paraquat poisoning: toxicologic and pathologic findings in three fatal cases

Paraquat Poisoning: Insights from Autopsy, Histology, and Liquid Chromatography with Tandem Mass Spectrometry in Multidisciplinary Forensic Toxicology Practice

The herbicide paraquat (PQ) is responsible for a significant number of fatalities resulting from self-poisoning. Nevertheless, only a limited number of comprehensive studies focusing on fatal PQ poisoning, which include examination of autopsy findings, histopathology, and quantitative analysis of post-mortem samples, have been published. This study aimed to evaluate autopsy findings, histopathology, and quantitative analysis of PQ in post-mortem human serum samples using liquid chromatography-tandem mass spectrometry (LC-MS/MS), a simple, sensitive, and specific method. Autopsies were performed on all deaths due to PQ poisoning, and serum samples were sent to the toxicology laboratory for chemical analysis. The method was successfully applied to seven human serum samples, and the results indicate its reliability for detecting PQ. The study reports fatal serum PQ levels ranging from 0.5 to 372.0 µg/mL. The comprehensive data presented in this study can be useful for further research and practical applications.

Tissue concentration of paraquat on day 32 after intoxication and failed bridge to transplantation by extracorporeal membrane oxygenation therapy

Background

Paraquat is a highly toxic herbicide, which not only leads to acute organ damage, but also to pulmonary fibrosis. There are only anecdotal reports of rescue lung transplantation, as paraquat is stored and only slowly released from different tissues. Bridging the time to complete depletion of paraquat from the body could render this exceptional therapy strategy possible, but not much is known on the time interval after which transplantation can safely be performed.

Case presentation

We report on a case of accidental paraquat poisoning in a 23 years old Caucasian man, who developed respiratory failure due to pulmonary fibrosis. The patient was listed for high urgency lung transplantion, and extracorporeal membrane oxygenation was implemented to bridge the time to transplantation. The patient died 32 days after paraquat ingestion, before a suitable donor organ was found. In postmortem tissue specimen, no paraquat was detectable anymore.

Conclusion

This case report indicates that complete elimination of paraquat after oral ingestion of a lethal dose is achievable. The determined time frame for this complete elimination might be relevant for patients, in which lung transplantation is considered.

Postmortem analyses unveil the poor efficacy of decontamination, anti-inflammatory and immunosuppressive therapies in paraquat human intoxications

Background

Fatalities resulting from paraquat (PQ) self-poisonings represent a major burden of this herbicide. Specific therapeutic approaches have been followed to interrupt its toxic pathway, namely decontamination measures to prevent PQ absorption and to increase its excretion from organism, as well as the administration of anti-inflammatory and immunosuppressive drugs. Until now, none of the postmortem studies resulting from human PQ poisonings have assessed the relationship of these therapeutic measures with PQ toxicokinetics and related histopathological lesions, these being the aims of the present study.

Methodology/Principal Findings

For that purpose, during 2008, we collected human fluids and tissues from five forensic autopsies following fatal PQ poisonings. PQ levels were measured by gas chromatography-ion trap mass spectrometry. Structural inflammatory lesions were evaluated by histological and immunohistochemistry analysis. The samples of cardiac blood, urine, gastric and duodenal wall, liver, lung, kidney, heart and diaphragm, showed quantifiable levels of PQ even at 6 days post-intoxication. Structural analysis showed diffused necrotic areas, intense macrophage activation and leukocyte infiltration in all analyzed tissues. By immunohistochemistry it was possible to observe a strong nuclear factor kappa-B (NF-κB) activation and excessive collagen deposition.

Conclusions/Significance

Considering the observed PQ levels in all analyzed tissues and the expressive inflammatory reaction that ultimately leads to fibrosis, we conclude that the therapeutic protocol usually performed needs to be reviewed, in order to increase the efficacy of PQ elimination from the body as well as to diminish the inflammatory process.

Paraquat poisonings: mechanisms of lung toxicity, clinical features, and treatment

Paraquat dichloride (methyl viologen; PQ) is an effective and widely used herbicide that has a proven safety record when appropriately applied to eliminate weeds. However, over the last decades, there have been numerous fatalities, mainly caused by accidental or voluntary ingestion. PQ poisoning is an extremely frustrating condition to manage clinically, due to the elevated morbidity and mortality observed so far and due to the lack of effective treatments to be used in humans. PQ mainly accumulates in the lung (pulmonary concentrations can be 6 to 10 times higher than those in the plasma), where it is retained even when blood levels start to decrease. The pulmonary effects can be explained by the participation of the polyamine transport system abundantly expressed in the membrane of alveolar cells type I, II, and Clara cells. Further downstream at the toxicodynamic level, the main molecular mechanism of PQ toxicity is based on redox cycling and intracellular oxidative stress generation. With this review we aimed to collect and describe the most pertinent and significant findings published in established scientific publications since the discovery of PQ, focusing on the most recent developments related to PQ lung toxicity and their relevance to the treatment of human poisonings. Considerable space is also dedicated to techniques for prognosis prediction, since these could allow development of rigorous clinical protocols that may produce comparable data for the evaluation of proposed therapies.

Spectra interference between diquat and paraquat by second derivative spectrophotometry

A rapid and accurate method, combining solid-phase extraction and second-order derivative spectrophotomety approaches, is developed for the simultaneous determination of diquat (DQ) and paraquat (PQ) in blood, tissue and urine samples. Supernatant resulting from the precipitation of protein (with trichloroacetic acid) in plasma and tissue or Amberlite IRA-401 resin treated urine are passed through a mini-column packed with Wakogel gel (Silica gel). Analytes are then eluted with a non-organic solvent, 0.2mol/l HCl solution containing 2mol/l NH(4)Cl. UV spectrum of the eluent in 220-350nm range provides effective screen to detect the presence of DQ and/or PQ. In the presence of DQ or PQ alone, the analyte present is quantitated by conventional zero- or second-order derivative spectrophotometry. The calibration curve in the 0.1-5.0mg/l range for either analyte obeys Beer's law. When both DQ and PQ are present, their concentrations are determined by the peak amplitudes of their respective second-derivative spectra after the addition of alkaline dithionite reagent. Interference is negligible when the DQ/PQ concentration ratio is within the 5.0-0.2 range. Using a 2-ml of sample size, the detection limits for DQ and PQ in plasma are 0.02 and 0.005mg/l. The corresponding detection limits for urine samples (10ml sample size) are 0.004 and 0.001mg/l. Recoveries of DQ and PQ in triplicate plasma and urine samples spiked with 0.5mg/l of analytes are 93 and 85%. The precision of the proposed method resulting from triplicate study of spiked urine samples varies from 3.2 to 4.6% at 0.5mg/l of DQ and PQ, respectively.

Tracheal injury caused by ingested paraquat

Paraquat is a potent herbicide of lethal toxicity. Its injury mechanism is attributed to the generation of very-reactive oxygen species, such as superoxide radicals, through which multiple injuries are produced on mucosa, although there have been no reports of injuries on the trachea. We describe a case of fatal paraquat poisoning with tracheal injuries, where the clinical debut was acute respiratory insufficiency and a spontaneous pneumothorax.

Paraquat myopathy: report on two suicide cases

We describe two suicide cases in which old paraquat was ingested. In conjunction with lung involvement a pronounced degeneration was observed in skeletal muscle of one who died on the 14th day after the ingestion. The following sarcoplasmic or endoplasmic reticulum Ca2+ ATPase (SERCA) monoclonal antibodies were used for skeletal muscle fiber typing by an immunohistochemical method: NCL-SERCA1, reactive with type 2 fiber (fast-twitch), and NCL-SERCA2, reactive with type 1 fiber (slow-twitch). The examination revealed that the remarkably degenerated fibers belonged to type 1 muscle fibers. This case showed an abrupt increase of plasma CK levels (1796 mU/ml) on the fifth day after the ingestion. The authors presume that the damage to the skeletal muscle had occurred in this period. The degeneration of the muscle seemed to be attributable to the long retention of paraquat in the tissue because these findings were not observed in the other case who died on the fifth day. Paraquat-induced myopathy may develop in prolonged paraquat poisoning. The examination of CK levels in plasma will be useful for diagnosis of damage of skeletal muscle.

Cytotoxicity of paraquat in freshly isolated rat hepatocytes: effects of L-carnitine

The effects of L-carnitine, a mitochondrial carrier of fatty acids, on paraquat (PQ) cytotoxicity in freshly isolated rat hepatocytes were studied. Addition of PQ (10 mM) to hepatocytes resulted in a time-dependent depletion of intracellular glutathione (GSH) accompanied by an increase in accumulation of malondialdehyde (MDA) in the incubation medium which proceeded to a loss of cell viability. Pretreatment of hepatocytes with L-carnitine (50-mM) alone did not affect cell viability or intracellular levels of GSH, or accumulation of MDA in the medium during the incubation period; however, pretreatment with L-carnitine 30 min prior to PQ addition did promote the depletion of intracellular GSH and MDA accumulation induced by PQ, and ultimately enhanced the cytotoxicity of PQ.

Changes in lipid peroxidation levels and lipid composition in the lungs, livers, kidneys and brains of mice treated with paraquat

We examined lipid peroxide levels and the lipid composition of homogenates prepared from the lungs, livers, kidneys and brains of 48 male ICR mice treated with 30 mg kg-1 paraquat (1,1'-dimethyl-4,4'-bipyridylium dichloride). The mice were divided into eight groups, in which they were killed 0, 1.5, 3, 6, 12, 24, 48 and 120 h after the administration of paraquat. A significant increase in the lipid peroxide level was identified only in the liver. Change in lipid composition was identified in all the examined organs. However, the change was not a characteristic one in which there is a selective decrease of polyunsaturated fatty acids which become degraded in a lipid peroxidation reaction. It is possible that the mechanism of paraquat toxicity may differ in different organs.

A fatal case of parenteral paraquat poisoning

The chief clinical and analytical aspects of the suicide of a 21-year-old male with psychiatric problems by parenteral administration of a 200 g/l aqueous solution of paraquat are described. Paraquat levels were determined in plasma, urine, kidney, liver and lung after autopsy. Tissue damage was studied by electron microscopy. The death ensued from pulmonary dysfunction 15 days after hospital admission.

Determination of paraquat from formalin-fixed tissue

In this paper, a sulfuric acid digestion method and a clean-up technique by using cation exchange resin followed by XAD-2 resin has been developed for the determination of paraquat from formalin-fixed tissue at the submicrograms per gram level. Formalin-fixed tissue is dissolved by hot sulfuric acid, then paraquat is isolated and purified with cation exchange chromatography. The eluted paraquat forms an ion-pair with sodium dodecyl sulfate, it is then adsorbed on XAD-2 resin. Paraquat is eluted, extracted and reduced with solvent mixtures, NaCl solution and dithionite reagent, respectively. The calibration graphs of zero-order and second-derivative spectroscopy are linear in the range of 0.01-5.0 mg/kg. The relative standard deviation was less than 5% and the detection limit was 0.02 mg/kg based on 0.5-g samples. The sensitivity of the proposed method could be increased by using larger sample sizes. The method was precise and gave a quantitative recovery of paraquat spiked into formalin-fixed liver homogenates (78%). The proposed method has been satisfactorily applied to the determination of paraquat in the formalin-fixed tissues of suspected poisoned cases. It has been shown to be of great value in the field of forensic toxicology especially when formalin-fixed tissue only is available.

Failure of haemoperfusion and haemodialysis to prevent death in paraquat poisoning. A retrospective review of 42 patients

In this review the efficacy of haemoperfusion in the treatment of paraquat poisoning is addressed. 42 reports containing sufficient information of paraquat-poisoned patients were evaluated. These reports, from 35 patients reported in the literature and 7 new cases, were chosen for the following reasons: the timed plasma paraquat concentrations were known, patient outcome was known, and details of haemoperfusion were available. In some cases, haemodialysis was also performed. The plasma paraquat concentrations and the specific times post-ingestion were plotted on a contour graph that predicts the probability of survival. Comparison of the predicted probability of survival versus the actual outcome showed that haemoperfusion, single or repeated, did not affect patient survival. None of the patients whose initial plasma concentrations were greater than 3 mg/L paraquat survived, regardless of the time after ingestion that the concentrations were measured, and despite haemoperfusion. Therefore, such patients might not be considered for haemoperfusion because of their uniformly bad prognosis, despite the procedure being used, and because of the morbidity, discomfort and cost associated with it. Clearly, the need for better techniques to remove paraquat and to prevent the consequences of the metabolic effects of the compound are required urgently before the treatment of the paraquat-poisoned patient will be successful.

Determination of paraquat in tissue using ion-pair chromatography in conjunction with spectrophotometry

Homogenized tissue was deproteinized with sulfuric acid. Paraquat in the supernatant was quantificated directly with the dithionite reagent (step 1) or concentrated by the XAD-2 column chromatographic technique before paraquat determination (step 2). Tissue paraquat levels in the range of 0.01-75 mg/kg could be quantificated by second-derivative or zero-order spectroscopy using 2.5 g of tissues. The sensitivity could be increased tenfold by using 25 g of tissue samples. The coefficients of variation of within-run and day-to-day precisions of spiked paraquat in tissue homogenates were below 5% at concentrations of 10.0, 1.0 and 0.1 mg/kg, respectively. The recoveries of the spiked paraquat in tissues ranging from 0.1-10 mg/kg were 91% by step 1 and 74% by step 2. Using these simple methods, steps 1 and 2, the paraquat concentrations in the psoas muscle, liver, lung and kidneys of a swine dosed with 0.16 g/kg of paraquat were investigated. The results were in close agreement with those of the TCA deproteinization method followed by cation-resin column chromatography. The proposed method offers the advantages of simplicity, rapidity, reasonable sensitivity and a wide range of concentrations.