Paraquat poisoning: significance of plasma-paraquat concentrations

Plasma-paraquat concentrations were measured in 79 patients who had ingested liquid or granular weedkillers containing paraquat. At any given time after ingestion, the plasma-paraquat concentrations in the patients who died usually exceeded those in the survivors. It is suggested that measurement of plasma-paraquat concentrations is useful in assessing the severity and predicting the outcome of poisoning. Patients whose plasma concentrations do not exceed 2.0, 0.6, 0.3, 0.16, and 0.1 mg/l at 4, 6, 10, 16, and 24 h respectively are likely to survive.

Prediction of outcome after paraquat poisoning by measurement of the plasma paraquat concentration

BACKGROUND

Paraquat is a herbicide with a good occupational safety record, but a high mortality after intentional ingestion that has proved refractory to treatment. For nearly three decades paraquat concentration-time data have been used to predict the outcome following ingestion. However, none of the published methods has been independently or prospectively validated. We aimed to use prospectively collected data to test the published predictive methods and to determine if any is superior.

METHODS

Plasma paraquat concentrations were measured on admission for 451 patients in 10 hospitals in Sri Lanka as part of large prospective cohort study. All deaths in hospital were recorded; patients surviving to hospital discharge were followed up after 3 months to detect delayed deaths. Five prediction methods that are based on paraquat concentration-time data were then evaluated in all eligible patients.

RESULTS

All methods showed comparable performance within their range of application. For example, between 4- and 24-h prediction of prognosis was most variable between Sawada and Proudfoot methods but these differences were relatively small [specificity 0.96 (95% CI: 0.90-0.99) vs. 0.89 (0.82-0.95); sensitivity 0.57 vs. 0.79, positive and negative likelihood ratios 14.8 vs. 7.40 and 0.44 vs. 0.23 and positive predictive values 0.96 vs. 0.92, respectively].

CONCLUSION

All five published methods were better at predicting death than survival. These predictions may also serve as tools to identify patients who need treatment and for some assessment to be made of new treatments that are trialled without a control group.

Prognostic value of plasma and urine paraquat concentration

A non-exponential mathematical equation was used to extrapolate the 'predictive line' for plasma paraquat concentrations beyond 24 h. Plasma paraquat concentrations were measured in 30 patients who were admitted more than 24 h after overdose. The extrapolated line accurately predicted the outcome in 27 of these 30 patients. Urine paraquat concentrations were measured in 53 patients. All patients with urine paraquat concentrations of less than 1 mg/l (colourless or light blue test result using the colorimetric test) within 24 h of overdose survived. In contrast, patients with urine paraquat concentrations of more than 1 mg/l had a high probability of death. Even if plasma paraquat concentrations have a higher predictive value, urine data may contribute to a more rapid evaluation of prognosis.

Repeated pulse of methylprednisolone and cyclophosphamide with continuous dexamethasone therapy for patients with severe paraquat poisoning

OBJECTIVE

Paraquat is widely used in the world, and all treatments for paraquat poisoning have been unsuccessful. Many patients have died of paraquat poisoning in developing countries. A novel anti-inflammation method was developed to treat severe paraquat-poisoned patients with >50% to <90% predictive mortality: initial pulse therapy with methylprednisolone (1 g/day for 3 days) and cyclophosphamide (15 mg/kg/day for 2 days), followed by dexamethasone 20 mg/day until Pao2 was >11.5 kPa (80 mm Hg) and repeated pulse therapy with methylprednisolone (1 g/day for 3 days) and cyclophosphamide (15 mg/kg/day for 1 day), which was repeated if Pao2 was <8.64 kPa (60 mm Hg).

DESIGN

Randomized controlled trial.

SETTING

Academic medical center in Taiwan.

PATIENTS

Twenty-three paraquat-poisoned patients with >50% and <90% predictive mortality assessed by plasma paraquat levels were prospectively and randomly assigned to the control and study groups at a proportion of 1:2.

INTERVENTIONS

The control group received conventional therapy and the study group received the novel repeated pulse treatment with long-term steroid therapy.

MEASUREMENTS AND MAIN RESULTS

We measured patient mortality during the study period. There was not a different distribution of basal variables between the two study groups. The mortality rate (85.7%, six of seven) of the control group was higher than that of the study group (31.3%, five of 16; p = .0272).

CONCLUSIONS

The novel anti-inflammatory therapy reduces the mortality rate for patients with severe paraquat poisoning.

Prospects for treatment of paraquat-induced lung fibrosis with immunosuppressive drugs and the need for better prediction of outcome: a systematic review

BACKGROUND

Acute paraquat self-poisoning is a significant problem in parts of Asia, the Pacific and the Caribbean. Ingestion of large amounts of paraquat results in rapid death, but smaller doses often cause a delayed lung fibrosis that is usually fatal. Anti-neutrophil ('immunosuppressive') treatment has been recommended to prevent lung fibrosis, but there is no consensus on efficacy.

AIM

To review the evidence for the use of immunosuppression in paraquat poisoning, and to identify validated prognostic systems that would allow the use of data from historical control studies and the future identification of patients who might benefit from immunosuppression.

DESIGN

Systematic review.

METHODS

We searched PubMed, Embase and Cochrane databases for 'paraquat' together with 'poisoning' or 'overdose'. We cross-checked references and contacted experts, and searched on [www.google.com] and [www.yahoo.com] using 'paraquat', 'cyclophosphamide', 'methylprednisolone' and 'prognosis'.

RESULTS

We found ten clinical studies of immunosuppression in paraquat poisoning. One was a randomized controlled trial (RCT). Seven used historical controls only; the other two were small (n = 1 and n = 4). Mortality in controls and patients varied markedly between studies. Three of the seven non-RCT controlled studies measured plasma paraquat; analysis using Proudfoot's or Hart's nomograms did not suggest that immunosuppression increased survival in these studies. Of 16 prognostic systems for paraquat poisoning, none has been independently validated in a large cohort.

DISCUSSION

The authors of the RCT have performed valuable and difficult research, but their results are hypothesis-forming rather than conclusive; elsewhere, the use of historical controls is problematic. In the absence of a validated prognostic marker, a large RCT of immunosuppression using death as the primary outcome is required. This RCT should also prospectively test and validate the available prognostic methods, so that future patients can be selected for this and other therapies on admission.

Effective treatment for paraquat poisoning in rats and its relevance to treatment of paraquat poisoning in man

After oral administration of a lethal dose of paraquat to rats the plasma concentration remained relatively constant over four to 30 hours and was related to the paraquat content of the small intestine over the first 16 hours. During the first 30 hours the concentration of paraquat in the lung rose progressively above that of the plasma to levels which are known to cause pulmonary damage. A treatment has been devised which prevents the absorption of paraquat into the plasma and prevents accumulation of paraquat in the lung. This treatment consists of a stomach was followed by four administrations of bentonite plus purgatives at two- to three-hour intervals. Even when treatment was delayed until 10 hours after administration of paraquat 80% survival was obtained. The relevance of this treatment to paraquat poisoning in man is discussed in the light of the finding that slices of human lung accumulate paraquat in the same way as those of rat lung.

Prognosis and treatment of paraquat poisoning: a review of 28 cases

Paraquat poisoning is very severe. When it is ingested, this herbicide may be responsible for causative lesions of the digestive tract, cytolytic hepatitis, renal tubular necrosis, circulatory failure, and/or pulmonary fibrosis. Since a very low dose (as little as one mouthful) is potentially lethal, it is important to understand why 11 of our 28 patients who entered our department for paraquat poisoning survived. The main prognostic factors appear to be the following: Route of administration. Of four patients who had inhaled paraquat aerosols and/or contaminated their skin with the herbicide, all survived. Ingested amount. Above 50 mg/kg, patients died of circulatory failure within 72 h; between 35 and 50 mg/kg, a progressive pulmonary fibrosis occurred. Delay between ingestion and the last meal. Paraquat is adsorbed and neutralized by foodstuffs. Caustic gastric lesions revealed by early endoscopic examination. The occurrence of an organic renal failure. The plasma paraquat concentrations within the first 24 h. Patients whose plasma concentrations do not exceed 2.0, 0.6, 0.3, 0.16, and 0.1 mg/L at 4, 6, 10, 16, and 24 h, respectively, are likely to survive. The different treatments that have been tested (fuller's earth, forced diarrhea, furosemide, hemodialysis, hemoperfusion, artificial ventilation with hypoxic breathing mixtures) did not modify the initial prognosis. The 11 survivals are only linked to the circumstances of the poisonings (route of administration, ingested amount, delay between ingestion and the last meal, etc.). The treatments did not modify the outcome.

Gas chromatographic-mass spectrometric method for the determination of the herbicides paraquat and diquat in plasma and urine samples

In the present work, a method was developed and optimized aiming to determinate the herbicides paraquat (PQ) and diquat (DQ) in human plasma and urine samples. An initial procedure of chemical reduction of the analytes by adding NaBH4 directly in the buffered samples (pH 8.0) was performed. This procedure was necessary to convert the quaternary ammonium substances into more volatile compounds for gas chromatographic analysis. The reduction compounds were extracted with C18 cartridges (solid-phase extraction). Ethyl paraquat (EPQ) was used as internal standard (IS). Gas chromatography-mass spectrometry (GC-MS) was used to identify and quantify the analytes in selected ion monitoring (SIM) mode. The limits of detection were 0.05 mg/l for both PQ and DQ. By using the weighted least squares linear regression (1/x1/2 for plasma and 1/y for urine), the accuracy of the analytical method was improved at the lower end of the calibration curve (from 0.1 to 50 mg/l; r>0.98). This method can be readily utilized as an important tool to confirm the suspicion of PQ and/or DQ poisoning and evaluate the extent of the intoxication.

Glyphosate and Paraquat in Maternal and Fetal Serums in Thai Women

OBJECTIVES

This longitudinal study measured the glyphosate and paraquat concentrations found in maternal and umbilical cord serum in 82 pregnant women who gave birth in three provinces of Thailand.

METHODS

Through questionnaires and biological samples collected at childbirth, factors such as personal characteristics, family members occupation, agricultural activities, and herbicide use in agricultural work were evaluated as predictors of glyphosate and paraquat levels in the pregnant women. Statistical analysis used univariate and binary multiple logistic regression, where the outcome was the probability of exposure to paraquat or glyphosate above the limit of detection associated with occupation and household factors.

RESULTS

The glyphosate concentrations in the pregnant women's serum at childbirth (median: 17.5, range: 0.2-189.1 ng/mL) were significantly higher (P < .007) than those in the umbilical cord serum (median: 0.2, range: 0.2-94.9 ng/mL). However, the paraquat concentrations in the serum of the pregnant women at childbirth (83% ≤limit of detection [LOD], with maximum of 58.3 ng/mL) were similar to those in the umbilical cord serum (80% LOD in serum at childbirth were 11.9 times more likely to report work as an agriculturist (P < .001), 3.7 times more likely to live near agricultural areas (P = .006), and 5.9 times more likely to have a family member who worked in agriculture (P < .001). The only factors affecting paraquat exposures in pregnant women at childbirth were reporting the agricultural activity of digging in farm soil and working in the agricultural fields in the third trimester of pregnancy.

CONCLUSIONS

These results show that pregnant women who work in agriculture or live in families that work in agriculture have higher exposures to the herbicides glyphosate and paraquat. The potential for long-term health impacts of these prenatal exposures to children should be evaluated, and greater regulation of the sale and use of herbicides should be considered in Thailand.

LC/MS/MS analysis of quaternary ammonium drugs and herbicides in whole blood

Quaternary ammonium drugs (atracurium, bretylium, edrophonium, ipratropium, mivacurium, neostigmine, pancuronium and rocuronium) and herbicides (difenzoquat, diquat and paraquat) in human whole blood were analysed by LC/MS/MS with positive electrospray ionisation (ESI), following extraction with Bond Elut LRC-CBA cartridges. Internal standards were benzyldimethylphenylammonium chloride monohydrate and ethyl viologen for drug and herbicide analysis, respectively. Ion-pair chromatography used heptafluorobutyric acid (15 mM)-ammonium formate (20 mM) buffer adjusted to pH 3.30 with formic acid and a linear gradient from 5 to 90% methanol run over 18 min. Recoveries ranged from 79.7 to 105.1%, detection limits were between 3.6 and 20.4 ng/ml and the intra- and inter-day precisions were less than 18.6% at a concentration of 10 ng/ml. The method was applied to a case of accidental paraquat poisoning in which the concentration of paraquat in blood was 0.64 mg/l, which is within the range associated with fatal paraquat poisoning.

Diagnostic and therapeutic approach for acute paraquat intoxication

Paraquat (PQ) has known negative human health effects, but continues to be commonly used worldwide as a herbicide. Our clinical data shows that the main prognostic factor is the time required to achieve a negative urine dithionite test. Patient survival is a 100% when the area affected by ground glass opacity is <20% of the total lung volume on high-resolution computed tomography imaging 7 days post-PQ ingestion. The incidence of acute kidney injury is approximately 50%. The average serum creatinine level reaches its peak around 5 days post-ingestion, and usually normalizes within 3 weeks. We obtain two connecting lines from the highest PQ level for the survivors and the lowest PQ level among the non-survivors at a given time. Patients with a PQ level between these two lines are considered treatable. The following treatment modalities are recommended to preserve kidney function: 1) extracorporeal elimination, 2) intravenous antioxidant administration, 3) diuresis with a fluid, and 4) cytotoxic drugs. In conclusion, this review provides a general overview on the diagnostic procedure and treatment modality of acute PQ intoxication, while focusing on our clinical experience.

Leucocyte suppression in treatment of 72 patients with paraquat poisoning

72 patients who had ingested more than 10 ml 20% or 24% liquid paraquat concentrate were treated for 2 weeks with high doses of dexamethasone and cyclophosphamide, forced diuresis with liberal potassium supplements, and, to eliminate paraquat from the gut, Fuller's earth suspension, activated charcoal, and magnesium sulphate. 52 patients (72%) survived. Serum paraquat concentrations were measured retrospectively in samples from 25 patients. 18 had levels of 2-76 mg/l; 6 survived and 12 died. The other survivors were a patient with a serum level of 0.5 mg/l at 24 h and 6 with positive urine tests but no measurable paraquat in serum collected 8-16 h after admission.

Determination of the herbicides paraquat and diquat in blood and urine by gas chromatography

A gas chromatographic method is described for determining paraquat (I) and diquat (II) in human blood and urine. I or II was readily precipitated as its reineckate complex (III and IV) by addition of Reinecke reagent, although blood required deproteination with 3.4% perchloric acid or 10% trichloroacetic acid. The precipitation is completed in 1 h at room temperature. III and IV were easily reduced by treatment with a mixture of sodium borohydride and nickel(II) chloride to afford corresponding perhydrogenated products, 1,1'-dimethyl-4,4'-bipiperidine (V) from III and trans- and cis-perhydrodipyrido[1,2-a:2',1'-c] pyrazine (VI) from IV. The perhydrogenated products were determined by gas-liquid chromatography (GLC) without interference from the original components of the blood and urine. The GLC method (5% potassium hydroxide solution with 5% Apiezon L on Chromosorb W AW DMCS) is suitable for simultaneous determination with hydrogen flame-ionization detection in the range 1-70 micrograms/ml (0.7-50.7 micrograms/ml as I ion; 0.5-35.6 micrograms/ml as II ion) of I and II in blood and urine. The method could be applicable to the determination of the chemicals in postmortem tissue and as pollutants in soils.

Mechanism of cytotoxicity of paraquat. III. The effects of acute paraquat exposure on the electron transport system in rat mitochondria

The effects of acute paraquat exposure on mitochondrial function in rat lung were studied. The paraquat dose-response study and time-effective study were performed to prove our hypothesis, enzyme toxicity especially in electron transport system following lipid peroxidation of mitochondrial inner membrane. In dose-response study, lipid peroxidation was increased by high dose paraquat exposure (40 mg/kg body weight) in rat lung, but not by low dose exposure (10 mg/kg body weight). But paraquat inhibited NADH:ubiquinone oxidoreductase (complex I) activities, especially NADH:ubiquinone reaction (NQR), even in low dose exposure. The lipid peroxide concentration did not correspond to the damage of complex I activity. In paraquat time-effective study, both lung and blood lipid peroxides increased after 6 h of paraquat exposure, decreased after 12 and 24 h and increased again after 48 h. After first peak of lipid peroxidation, NQR velocity decreased earlier than NADH:ferricyanide reaction (NFR) velocity. From these results, the cytotoxicity via mitochondrial dysfunction by acute paraquat exposure might be caused by complex I toxicity following lipid peroxidation of mitochondrial inner membrane.

Quantitative determination of the herbicide paraquat in human plasma by gas chromatographic and mass spectrometric methods

The gas chromatographic (GC) determination of the herbicide paraquat, the 1,1'-dimethyl-4,4'-dipyridyl cation in human plasma is described. In poisoning cases, plasma concentrations provide a necessary index of the severity of intoxication and a means of monitoring subsequent therapy. The methods may be extended to the specific trace analysis of paraquat in body fluids of post-mortem tissue. Reduction of fully ionised paraquat salts with sodium borohydride yields a hexahydro derivative, a diene, amenable to solvent extraction and GC. Employing 1,1'-diethyl-4,4'-dipyridyl dichloride as the internal standard, plasma concentrations of 0.1 microgram/ml (+/- 6% S.D.) may be determined with flame ionisation detection and 0.025 microgram/ml with nitrogen-selective flame ionisation. Further enhancement of specificity is achieved using selected ion monitoring mass spectrometry and the value of this technique in forensic analysis is illustrated.

Radioimmunoassay for serum paraquat

Two variants of a radioimmunoassay for the bipyridylium herbicide Paraquat are described. Both employ antiserum raised to Paraquat-BSA which has been covalently linked to particulate solid-phase support media. The rapid assay for clinical use employs a [3H] Paraquat tracer, requires no agitation and yields results in the range 10--2500 ng/ml serum in 20 min from receipt of sample. The more sensitive assay, designed for research purposes, employs a 125iodinated tracer, requires 2 h continuous agitation but can detect Paraquat at 0.1 ng/ml in simple aqueous solution or 0.25 ng/ml serum. Results from rapid clinical assay agree well with the existing colorimetric method.

A long-term follow-up of lung function in survivors of paraquat poisoning

1. Respiratory failure is a frequent cause of death in moderate to severe paraquat poisoning, and a transient fall in the gas transfer factor may be seen in mild poisoning. 2. The objectives of this study were to detect long-term changes in lung function in survivors of paraquat poisoning. 3. We analyzed 12 survivors retrospectively for age, sex, signs and symptoms, laboratory findings, chest X-ray findings, serum paraquat level, and lung function test. The first and the follow-up lung tests were performed at 3.7+/-1.4 weeks and 3.4+/-1.4 years, respectively. 4. Serum paraquat levels were assayed in all patients and 3/12 were above the Proudfoot's predictive line. Liver dysfunction (GOT > 50) and renal dysfunction (BUN > 30) were noted in 5/12 and 8/12, respectively. D(L)/V(A) was lower than the normal limit in the first study (3.9+/-0.6 L), but increased significantly and returned to the normal range in the follow-up study (4.5+/-0.6 L). %VC was within the normal range in either examination, but significantly decreased in the follow-up. %TLC was within the normal range in the first study (87+/-13%), but significantly decreased below the normal limit in the follow-up (81+/-13%). 5. These results indicate that survivors of paraquat poisoning may be left with a restrictive type of pulmonary dysfunction and suggest that a long-term follow-up of lung function may be necessary for survivors of paraquat poisoning.

The rapid extraction of paraquat from plasma using an ion-pairing technique

A method for the quantitative extraction of paraquat from plasma is described. The method relies on the use of an organic-soluble ion pair of paraquat with dodecyl sulphate. The use of the extraction procedure in conjunction with the dithionite colour reaction gives a method which is suitable for emergency estimations with a sensitivity limit of 50 micrograms/l. The extraction procedure alone offers a new first step in the clean up of paraquat for analysis by other methods.

Simultaneous Determination and Quantitation of Paraquat, Diquat, Glufosinate and Glyphosate in Postmortem Blood and Urine by LC-MS-MS

A simple method, incorporating protein-precipitation/organic backwashing and liquid chromatography-tandem mass spectrometry (LC-MS-MS), has been successfully developed for the simultaneous analysis of four highly water-soluble and less volatile herbicides (paraquat, diquat, glufosinate and glyphosate) in ante- and postmortem blood, urine and gastric content samples. Respective isotopically labeled analogs of these analytes were adopted as internal standards. Acetonitrile and dichloromethane were used for protein precipitation and organic solvent backwashing, respectively, followed by injecting the upper aqueous phase into the LC-MS-MS system. Chromatographic separation was achieved using an Agilent Zorbax SB-Aq analytical column, with gradient elution of 15 mM heptafluorobutyric acid and acetonitrile. Mass spectrometric analysis was performed under electrospray ionization in positive-ion multiple reaction monitoring mode. The precursor ions and the two transition ions (m/z) adopted for each of these four analytes were paraquat (185; 169 and 115), diquat (183; 157 and 78), glufosinate (182; 136 and 119) and glyphosate (170; 88 and 60), respectively. Analyte-free blood and urine samples, fortified with the analytes of interest, were used for method development/validation and yielded acceptable recoveries of the analytes; interday and intraday precision and accuracy data; calibration linearity and limits of detection and quantitation. This method was successfully incorporated into an overall analytical scheme, designed for the analysis of a broad range of compounds present in postmortem samples, helpful to medical examiners' efforts to determine victims' causes of death.

Multiple logistic regression analysis of plasma paraquat concentrations as a predictor of outcome in 375 cases of paraquat poisoning

Successful prediction of who may survive paraquat poisoning can prevent inappropriately aggressive treatment in those who have little hope of survival and those only minimally poisoned. We examined case records of patients admitted to one poisoning treatment unit over the last 5 years, and the English and French language literature on paraquat poisoning. Data were recorded from all patients where outcome and timed plasma paraquat concentrations were present. Of 375 patients (113 M, 62 F, 200 unknown), mean age 38.3 years (range 1-87 years), 49 had evidence of renal toxicity, and 41 received haemodialysis or charcoal haemoperfusion; 61 developed pulmonary sequelae; and 44 had lesions in the upper gastrointestinal tract. Median time from ingestion to death in the 241 deaths reported was 270 h (range 3-720 h). We plotted log(plasma paraquat concentration) against log(h since ingestion). The predicted probability of survival for any specified time and concentration was exp(logit)/[1 + exp(logit)], where logit = 0.58-2.33 x log(plasma paraquat)-1.15 x log(h since ingestion). This equation may be helpful in predicting who will survive after ingestion of paraquat up to at least 200 h after ingestion, and can now be used as a research tool for studies on efficacy of treatment of paraquat poisoning.