Leucocyte suppression in treatment of 72 patients with paraquat poisoning

Single-Center Experience with Mass Paraquat Exposure in Nine Patients

Paraquat dichloride is a widely used, highly toxic chemical herbicide and a significant cause of fatal poisonings. Toxicity is thought to be secondary to generation of reactive oxygen species. Hours after exposure, patients may experience signs and symptoms ranging from nausea to multi-system organ failure. To mitigate complications and death, immunosuppression with cyclophosphamide and corticosteroid-based therapies have shown to be an effective option in limited studies. Our objective is to report our center's experience treating patients that had been exposed to paraquat over a two-day period. Patients were identified using our Institutional Burn Center registry, and linked to the clinical and administrative data. Demographics, length of stay, costs and mortality were evaluated. There were nine patients admitted from the exposure. All were male. All survived. Eight were undocumented migrant farmers. The average age was 36 years (25-59 years). The average length of stay was 3.3 days (2-5 days). Seventy-eight percent had cutaneous injury, but only one required debridement and placement of a skin substitute. Thirty-three percent complained of continued shortness of breath after discharge. Average total hospital cost was $28,131 ($9,500-$51,000). Paraquat is a highly toxic herbicide and exposure can be fatal if not treated promptly. Immediate decontamination and repeated pulse therapy with cyclophosphamide and methylprednisolone may be life-saving.

Thoracic radiographic features of fatal paraquat intoxication in eleven dogs

BACKGROUND

Paraquat (1,1-dimethyl-4,4-bipyridinium dichloride) is a toxic herbicide. Accidental ingestion of paraquat in animals and humans causes respiratory failure and death.

AIM

To describe the radiographic features of confirmed paraquat intoxication in a group of dogs and determines whether any identified features can facilitate this diagnosis.

METHODS

Eleven dogs diagnosed with paraquat intoxication were selected from two institutions between November 2014 and August 2019 comprising five males (all intact) and six females (one intact and five spayed). The mean age was 3.9 ± 2.9 (SD) years and their mean weight was 11.6 ± 5.0 kg. The tentative diagnosis was confirmed through analysis of their urine samples using a colorimetric assay (paraquat concentation 0.39 μg/ml ranging from 0.19-0.65 μg/ml), and their clinical signs were reviewed. Thoracic radiographs were evaluated for the presence of pneumomediastinum, lung patterns (interstitial or alveolar) and their locations (caudodorsal, cranioventral, diffuse, or symmetrical), subcutaneous emphysema, pneumoretroperitoneum, and pneumothorax.

RESULTS

The most common clinical signs were dyspnea (11/11, 100%) and anorexia (9/11, 82%). Pneumomediastinum (10/11, 91%) and symmetrically increased lung opacity (7/11, 65%) were the most common radiographic features. Pneumothorax (3/11, 27%), pleural effusion (3/11, 27%), subcutaneous emphysema (2/11, 18%), and pneumoretroperitoneum (1/5, 20%) were the less common findings. None of the dogs survived.

CONCLUSION

Pneumomediastinum and diffuse or symmetrical interstitial or alveolar lung patterns are the most common radiographic features in dogs with paraquat intoxication.

CLINICAL RELEVANCE

In countries where this herbicide is not banned, paraquat intoxication should be considered if dogs with no history of trauma present with pneumomediastinum.

Glucocorticoid with cyclophosphamide for oral paraquat poisoning

BACKGROUND

This an update of a Cochrane Review. Paraquat is a widely used herbicide, but is also a lethal poison. In some low- and middle-income countries (LMICs) paraquat is commonly available and inexpensive, making poisoning prevention difficult. Most of the people poisoned by paraquat have taken it as a means of self-poisoning. Standard treatment for paraquat poisoning prevents further absorption and reduces the load of paraquat in the blood through haemoperfusion or haemodialysis. The effectiveness of standard treatments is extremely limited. The immune system plays an important role in exacerbating paraquat-induced lung fibrosis. Immunosuppressive treatment using glucocorticoid and cyclophosphamide in combination has been developed and studied as an intervention for paraquat poisoning.

OBJECTIVES

To assess the effects of glucocorticoid with cyclophosphamide for moderate to severe oral paraquat poisoning.

SEARCH METHODS

The most recent searches were run in September 2020. We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (which contains the Cochrane Injuries Trials Register), Ovid MEDLINE(R), Ovid MEDLINE In-Process & Other Non-Indexed Citations, Ovid MEDLINE Daily and Ovid OLDMEDLINE, Embase Classic + Embase (Ovid), ISI WOS (SCI-EXPANDED, SSCI, CPCI-S, and CPSI-SSH), and trials registries. We also searched the following three resources: China National Knowledge Infrastructure database (CNKI ); Wanfang Data (); and VIP () on 12 November 2020. We examined the reference lists of included studies and review papers.

SELECTION CRITERIA

We included randomised controlled trials (RCTs). For this update, in accordance with Cochrane Injuries' Group policy (2015), we included only prospectively registered RCTs for trials published after 2010. We included trials which assessed the effects of glucocorticoid with cyclophosphamide delivered in combination. Eligible comparators were standard care (with or without a placebo), or any other therapy in addition to standard care. Outcomes of interest included mortality and infections.

DATA COLLECTION AND ANALYSIS

We calculated the mortality risk ratio (RR) and 95% confidence interval (CI). Where possible, we summarised data for all-cause mortality at relevant time periods (from hospital discharge to three months after discharge) in meta-analysis, using a fixed-effect model. We conducted sensitivity analyses based on factors including whether participants were assessed at baseline for plasma paraquat levels. We also reported data on infections within one week after initiation of treatment.

MAIN RESULTS

We included four trials with a total of 463 participants. The included studies were conducted in Taiwan (Republic of China), Iran, and Sri Lanka. Most participants were male. The mean age of participants was 28 years. We judged two of the four included studies, including the largest and most recently conducted study (n = 299), to be at low risk of bias for key domains including sequence generation. We assessed one study to be at high risk of selection bias and another at unclear risk, since allocation concealment was either not mentioned in the trial report or explicitly not undertaken. We assessed three of the four studies to be at unclear risk of selective reporting, as no protocols could be identified. An important source of heterogeneity amongst the included studies was the method of assessment of participants' baseline severity using analysis of plasma levels (two studies employed this method, whilst the other two did not). No studies assessed the outcome of mortality at 30 days following ingestion of paraquat. Low-certainty evidence from two studies indicates that glucocorticoids with cyclophosphamide in addition to standard care may slightly reduce the risk of death in hospital compared to standard care alone ((RR 0.82, 95% CI 0.68 to 0.99; participants = 322); results come from sensitivity analysis excluding studies not assessing plasma at baseline). However, we have limited confidence in this finding as heterogeneity was high (I2 = 77%) and studies varied in terms of size and comparators. A single large study provided data showing that there may be little or no effect of treatment at three months post discharge from hospital (RR 0.98, 95% CI 0.85 to 1.13; 1 study, 293 participants; low-certainty evidence); however, analysis of long-term results amongst participants whose injuries arose from self-poisoning must be interpreted with caution. We remain uncertain of the effect of glucocorticoids with cyclophosphamide on infection within one week after initiation of the treatment; this outcome was assessed by two small studies only (31 participants, very low-certainty evidence) that considered leukopenia as a proxy or risk factor for infection. Neither study reported infections in any participants.

AUTHORS' CONCLUSIONS

Low-certainly evidence suggests that glucocorticoids with cyclophosphamide in addition to standard care may slightly reduce mortality in hospitalised people with oral paraquat poisoning. However, we have limited confidence in this finding because of substantial heterogeneity and concerns about imprecision. Glucocorticoids with cyclophosphamide in addition to standard care may have little or no effect on mortality at three months after hospital discharge. We are uncertain whether glucocorticoid with cyclophosphamide puts patients at an increased risk of infection due to the limited evidence available for this outcome. Future research should be prospectively registered and CONSORT-compliant. Investigators should attempt to ensure an adequate sample size, screen participants for inclusion rigorously, and seek long-term follow-up of participants. Investigators may wish to research the effects of glucocorticoid in combination with other treatments.

Osteonecrosis of Femoral Head, An Overlooked Long-Term Complication after Paraquat Intoxication: A Retrospective Cohort Study

With increasing numbers of patients surviving acute intoxication phase, long-term complication after paraquat intoxication is a topic worth exploring, such as osteonecrosis (ON) of femoral head. We reviewed 86 paraquat-intoxicated survivors between 2000 and 2012 in Chang Gung Memorial Hospital, a 3700-bed tertiary hospital in Taiwan. With all the patients underwent same detoxification protocol in the acute stage, 17.4% of paraquat poisoning survivors developed ON of femoral head requiring surgery during follow up. Most of ON episodes occurred within 2 to 4 years after paraquat intoxication and then plateau after 6 years. ON patients exhibited higher SOFA scores than non-ON patients (2.80 ± 2.14 vs. 1.76 ± 1.52, p = 0.028). Furthermore, AKIN scores are also higher in the ON patients than non-ON patients (0.87 ± 1.13 vs. 0.38 ± 0.74, p = 0.040). Multivariate logistic regression showed higher AKIN score and higher partial pressure of carbon dioxide in the blood 48 hours after admission significantly predicted ON of femoral head after paraquat intoxication (p = 0.002 and p = 0.006 respectively). Larger studies with longer follow-up durations are warranted to confirm our finding.

The effects of ω-3 fish oil emulsion-based parenteral nutrition plus combination treatment for acute paraquat poisoning

Objective

To investigate the effects of parenteral nutrition (PN) including ω-3 fish-oil emulsion on nutritional state, inflammatory response, and prognosis in patients with acute paraquat poisoning.

Methods

Patients randomized to receive medium chain triglycerides (MCT)/long chain triglycerides (LCT)-based PN (control group) or MCT/LCT-based PN containing ω-3 fish-oil emulsion (intervention group) were compared for 90-day survival and short-term treatment efficacy.

Results

Tumour necrosis factor-α levels were significantly lower in the intervention group (n = 101) versus controls (n = 73) on treatment days 4 and 7. Intervention group C-reactive protein (CRP) levels were significantly increased on day 4, decreased to baseline (day 1) levels on day 7, and were significantly lower than baseline on day 10. Control group CRP levels were significantly increased on days 4 and 7 versus baseline, and returned to baseline levels on day 10. On day 7, retinol binding protein had recovered to baseline levels in the intervention group only. Intervention group mortality rate (36.6%) was significantly lower than controls (57.5%). ω-3 fish-oil PN was associated with reduced risk of death (hazard ratio 0.52; 95% confidence interval 0.33, 0.82).

Conclusion

In patients with acute paraquat poisoning, MCT/LCT with ω-3 fish-oil emulsion PN plus combination treatment advantageously attenuated the inflammatory response, modified the nutritional state, and was associated with significantly improved 90-day survival versus treatment without ω-3 fish oil.

Effect of Pulse Therapy with Glucocorticoids and Cyclophosphamide in Patients with Paraquat Poisoning

Introduction

Paraquat (PQ) is a widely used herbicide with a high mortality rate when ingested. The aim of the present study was to assess the effectiveness of repeated cyclosphosphamide (CP) and methylprednisolone (MP) combination in the treatment of PQ poisoning.

Design

Randomised, double-blinded, placebo-controlled trial.

Methods

Eligible participants were 47 patients with moderate to severe PQ poisoning within 24 hours of hospitalisation. Patients were allocated in a random fashion, 24 as the intervention and 23 as the control group. All patients received two cycles of eight hours of haemoperfusion with charcoal, and underwent emergency haemodialysis. After the dialysis, the intervention group received 15 mg/kg CP for two days and 1g MP for three days. The control group received routine supportive care. Outcome parameters, including mortality, incidence of hypoxia, hepatitis and renal failure were compared between the two groups.

Results

There were no significant differences between the two groups with regard to age, sex, baseline liver function test, creatinine, time from poisoning to dialysis, and time from poisoning to the hospitalisation. Although the incidence of hepatitis and acute renal failure did not differ significantly between the two groups, the incidence of hypoxia and mortality rate was lower in the intervention group. The number need-to-treat to reduce one mortality was 2.8.

Conclusion

The results suggest that CP and MP repeated treatment can reduce the mortality rate in moderate to severe PQ intoxication.

Prolonged methylprednisolone therapy after the pulse treatment for patients with moderate-to-severe paraquat poisoning: A retrospective analysis

This retrospective study aims to evaluate the effect of prolonged methylprednisolone (MP) therapy on the mortality of patients with moderate-to-severe paraquat (PQ) poisoning after the pulse treatment.We performed a retrospective analysis of patients with acute moderate-to-severe PQ poisoning that were admitted to the emergency department from May 2012 to August 2016. Out of 138 patients, 60 were treated with pulse treatment (15 mg kg day MP for 3 days) and 78 were treated with prolonged MP therapy after pulse treatment (15 mg kg day MP for 3 days; afterward, the dosage was reduced in half every 2 days, and the MP therapy was terminated until 0.47 mg kg day). Kaplan-Meier method was used to compare the mortality between the 2 groups. Cox proportional hazard models were used to estimate the hazard ratios (HR) and 95% confidence intervals (CI).The mortality of the prolonged MP therapy after pulse treatment group was lower than that of the pulse group (47.4% vs 63.3%; log-rank tests, P  =  .003). According to the multivariate Cox analysis, the prolonged MP therapy after pulse treatment was significantly associated with a lower mortality risk (HR: 0.31, 95% CI: 0.19-0.52, P < .001) compared with the pulse group. In addition, the prolonged MP therapy after pulse treatment caused more incidences of leucopenia than the pulse treatment alone (25.6% vs 11.7%, P  =  .04).The prolonged MP therapy after pulse treatment can reduce the mortality of moderate-to-severe PQ poisoning patients.

Effects of Concentration Reduction and Partial Replacement of Paraquat by Diquat on Human Toxicity: A Clinical Survey

Paraquat poisoning was studied in 174 patients over a 12-month period when a new, low concentration paraquat product (4.5% w/v paraquat ion mixed with 4.5% w/v diquat ion; 6 3 cases) replaced the original high concentration paraquat product (20% w/v paraquat ion only; 111 cases).

In both groups approximately 60% of the patients died from circulatory failure accompanied by multiple organ failure within a week of ingesting the products. However, a remarkable reduction in late deaths from respiratory failure was noted in the new product group (17.1% vs 6.3%). This was reflected in this group's improved survival (23.4% vs 34.9%).

The improvement in survival seems to be attributable to the dilution of paraquat with diquat which seems to have a different toxicological profile to paraquat.

Prediction of outcome following paraquat poisoning by arterial lactate concentration-time data

The present study retrospectively analyzed 170 patients diagnosed with paraquat (PQ) poisoning with the aim of clarifying whether the arterial lactate-time (arterial lactate concentration × time between ingestion and arterial lactate measurement) was a good predictor of mortality in patients with acute PQ poisoning. The results indicated that there was a positive correlation between the arterial lactate-time and PQ concentration-time (ρ=0.485). In addition, the arterial lactate-time data exhibited a similar discriminative power to the plasma PQ concentration-time data (z=0.712; P=0.864). For the receiver operating characteristic curve analysis, the lactate-time data had an area of 0.782 with a cut-off value of 11.95 mmol/l.h (sensitivity, 64.52%; specificity, 84.42%). To calculate the predicted probability of survival for any specified time and initial arterial lactate concentration, the following formula was derived based on the logistic regression coefficients: Logit(p) = 3.066 − 0.139 × (time lag following PQ ingestion) − 0.177 × (initial arterial lactate concentration); where the probability of survivors = 1/1 + e^−logit(p). Therefore, the arterial lactate-time data exhibited a good predictive power for evaluating the prognosis of patients with acute PQ poisoning.

Addition of immunosuppressive treatment to hemoperfusion is associated with improved survival after paraquat poisoning: a nationwide study

Paraquat poisoning associates very high mortality rate. Early treatment with hemoperfusion is strongly suggested by animal and human studies. Although the survival benefit of additional immunosuppressive treatment (IST) in combination with hemoperfusion is also reported since 1971, the large-scale randomized control trials to confirm the effects of IST is difficult to be executed. Therefore, we designed this nationwide large-scale population-based retrospective cohort study to investigate the outcome of paraquat poisoning with hemoperfusion and the additional effects of IST combined with hemoperfusion. This nationwide retrospective cohort study utilized data retrieved from the National Health Insurance Research Database (NHIRD) of Taiwan. A total of 1811 hospitalized patients with a diagnosis of paraquat poisoning who received hemoperfusion between 1997 and 2009 were enrolled. The mean age of all 1811 study subjects was 47.3 years. 70% was male. The overall survival rate was only 26.4%. Respiratory failure and renal failure were diagnosed in 56.2% and 36% patients. The average frequency of hemoperfusion was twice. IST was added in 42.2% patients. IST significantly increases survival rate (from 24.3% to 29.3%, P<0.001). The combined IST with methylprednisolone, cyclophosphamide and dexamethasone associates with the highest survival rate (48%, P<0.001). Moreover, patients younger than 45 years of age in the IST group had the best survival (41.0% vs. 33.7%, p<0.001). Our results support the use of IST with hemoperfusion for paraquat-poisoned patients. The best survival effect of IST is the combination of methylprednisolone, cyclophosphamide and daily dexamethasone, especially in patients with younger age.

The dose of cyclophosphamide for treating paraquat-induced rat lung injury

BACKGROUND/AIMS

Cyclophosphamide (CP) is a promising treatment for severe cases of paraquat (PQ) poisoning. We investigated the effective dose of CP for mitigating PQ-induced lung injury.

METHODS

Adult male Sprague-Dawley rats were allocated into five groups: control, PQ (35 mg/kg, intraperitoneal injection), and PQ + CP (1.5, 15, or 30 mg/kg). The dimensions of lung lesions were determined using X-ray microtomography (micro-CT), and histological changes and cytokine levels were recorded.

RESULTS

The micro-CT results showed that 15 mg/kg CP was more effective than 1.5 mg/kg CP for treating PQ-induced lung injury. At a dose of 1.5 mg/kg, CP alleviated the histological evidence of inflammation and altered superoxide dismutase activity. Using 15 mg/kg CP reduced the elevated catalase activity and serum transforming growth factor (TGF)-β1 level.

CONCLUSIONS

A CP dose of > 15 mg/kg is effective for reducing the severity of PQ-induced lung injury as determined by histological and micro-CT tissue examination, possibly by modulating antioxidant enzyme and TGF-β1 levels.

Medical management of paraquat ingestion

Poisoning by paraquat herbicide is a major medical problem in parts of Asia while sporadic cases occur elsewhere. The very high case fatality of paraquat is due to inherent toxicity and lack of effective treatments. We conducted a systematic search for human studies that report toxicokinetics, mechanisms, clinical features, prognosis and treatment. Paraquat is rapidly but incompletely absorbed and then largely eliminated unchanged in urine within 12-24 h. Clinical features are largely due to intracellular effects. Paraquat generates reactive oxygen species which cause cellular damage via lipid peroxidation, activation of NF-κB, mitochondrial damage and apoptosis in many organs. Kinetics of distribution into these target tissues can be described by a two-compartment model. Paraquat is actively taken up against a concentration gradient into lung tissue leading to pneumonitis and lung fibrosis. Paraquat also causes renal and liver injury. Plasma paraquat concentrations, urine and plasma dithionite tests and clinical features provide a good guide to prognosis. Activated charcoal and Fuller's earth are routinely given to minimize further absorption. Gastric lavage should not be performed. Elimination methods such as haemodialysis and haemoperfusion are unlikely to change the clinical course. Immunosuppression with dexamethasone, cyclophosphamide and methylprednisolone is widely practised, but evidence for efficacy is very weak. Antioxidants such as acetylcysteine and salicylate might be beneficial through free radical scavenging, anti-inflammatory and NF-κB inhibitory actions. However, there are no published human trials. The case fatality is very high in all centres despite large variations in treatment.

Improved survival in severe paraquat poisoning with repeated pulse therapy of cyclophosphamide and steroids

PURPOSE

To clarify the efficacy of repeated methylprednisolone (MP) and cyclophosphamide (CP) pulse therapy and daily dexamethasone (DEX) therapy in patients with severe paraquat (PQ) poisoning.

METHODS

A total of 111 patients with severe PQ poisoning and dark-blue color in urine tests within 24 h of intoxication were included prospectively. The control group consisted of 52 patients who were admitted between 1998 and 2001 and who received high doses of CP (2 mg/kg per day) and DEX (5 mg every 6 h) for 14 days. The study group consisted of 59 patients who were admitted from 2002 to 2007 and who received initial MP (1 g) for 3 days and CP (15 mg/kg per day) for 2 days, followed by DEX (5 mg every 6 h) until a PaO(2) of >80 mmHg had been achieved, or treated with repeated 1 g MP for 3 days and 1 g CP for 1 day if the PaO(2) was <60 mmHg.

RESULTS

There were no differences between the two groups with regard to baseline data and plasma PQ levels. The study group patients had a lower mortality rate (39/59, 66%) than the control group patients (48/52, 92%; P=0.003, log-rank test). Multivariate Cox regression analysis revealed that the repeated pulse therapy was correlated with decreased hazard ratios (HR) for all-cause mortality (HR=0.50, 95% CI 0.31-0.80; P=0.004) and death from lung fibrosis-related hypoxemia (HR=0.10, 95% CI 0.04-0.25; P<0.001) in severely PQ-intoxicated patients.

CONCLUSION

Repeated pulses of CP and MP, rather than high doses of CP and DEX, may result in a lower mortality rate in patients with severe PQ poisoning.

Spectrum of corrosive esophageal injury after intentional paraquat ingestion

INTRODUCTION

This is an observational study that examines the clinical features, the degrees of esophageal injury, physiological markers, and clinical outcomes after paraquat ingestion and seeks to determine what association, if any, may exist between these findings.

METHODS

The study included 16 of 1410 paraquat subjects who underwent endoscopies at Chang Gung Memorial Hospital between 1980 and 2007.

RESULTS

Corrosive esophageal injuries were classified as grade 1 in 8, 2a in 5, and 2b in 3 patients. No patients had grade 0, 3a, or 3b esophageal injuries. After paraquat ingestion, systemic toxicity occurred, with rapid development of hypoxia, hepatitis, and renal failure in many cases. Hypoxia occurred in 1 (12.5%), 5 (100%), and 3 (100%) patients with grades 1, 2a, and 2b esophageal injury, respectively. There were more hypoxic patients with grades 2a and 2b than those with grade 1 esophageal injury (P < .05). The nadir Pao(2) was lower in patients with grades 2a and 2b than those with grade 1 esophageal injury (P < .05). However, there were no significant differences in terms of acute hepatitis, peak serum alanine aminotransferase, acute renal failure, and peak serum creatinine between the 3 groups (P > .05). Kaplan-Meier analysis did not find any difference in survival between the groups (P > .05).

CONCLUSION

Paraquat, a mild caustic agent, produces only grades 1, 2a, and 2b esophageal injury. Our findings showed a potential relationship between the degree of hypoxia, mortality, and degree of esophageal injury, although such a low number of study subjects limits the conclusions that can be made by this study.

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.

[Immunosuppressive treatment due to paraquat poisoning]

Paraquat is the most important member of the bipyridyl compound. It is directly caustic in nature and it exerts its herbicidal activity by inhibiting the reduction of NADP to NADPH during photosynthesis, a process in which superoxide, singlet oxygen, hydroxyl, and peroxide radicals are formed. Human tissue toxicity likely results from a similar oxidative mechanism. After oxidative destruction, recruitment of inflammatory cells leads to late onset and irreversible pulmonary fibrosis. Ingestion greater than 20-40 mg/kg of paraquat concentrate should be aggressively managed with the administration of intestinal decontaminants and hemoperfusion. Low-inspired oxygen therapy should be given until it becomes impractical in the face of hypoxemia. Administration of immunodepressive therapy, steroids and cyclophosphamide, should be considered. In addition, there should be intermittent assessment of pulmonary function and of plasma and urinary concentrations of paraquat.

Acute paraquat poisoning: report of a survival case following intake of a potential lethal dose

When properly used, paraquat (PQ) is a widely used bipyridil herbicide with a good safety record. Most cases of PQ poisoning result from intentional ingestion, with death resulting from hypoxemia secondary to lung fibrosis in moderate to severe poisonings. With high ingestion volumes (>50 mL of a 20% wt/vol formulation), death results from multiple organ failure and cardiovascular collapse within 1 week after intoxication. The present report describes a successful clinical case regarding the intoxication of a 15-year-old girl by a presumed lethal dose of PQ. The adolescent ingested approximately 50 mL of a commercialized concentrate (20% wt/vol of dichloride salt) formulation of PQ. High serum and urinary levels of PQ confirmed the bad prognosis. However, the therapeutic protocol followed in the present clinical case led to a positive outcome. Besides the measures for decreasing PQ absorption and increasing its elimination, other protective procedures were applied in aiming to reduce the production of reactive oxygen species (ROS), to scavenge ROS, to repair ROS-induced lesions, and to reduce inflammation. The status-of-the-art concerning the biochemical and toxicological aspects of PQ poisoning and the pharmacologic basis of the respective treatment is also presented.

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.

Combined initial cyclophosphamide with repeated methylprednisolone pulse therapy for severe paraquat poisoning from dermal exposure

The article presents a patient with severe paraquat poisoning from dermal exposure, who had chemical bums to more than 10% of his body surface area, serum paraquat level 0.13 microg/mL 60 hr after exposure, and severe hypoxemia (PaO2 41.6 mmHg). The patient was successfully treated with combined initial megadoses of cyclophosphamide (15 mg/kg/day, total 2 days) with repeated methylprednisolone pulse therapy (15 mg/kg/day, total 6 days) and continuous dexamethasone administration (5 mg every 8 hr), and recovered completely without sequelae 3 months later. This treatment deserves further investigation in future clinical trials.

Methylprednisolone effects on oxygenation and histology in a rat model of acute lung injury

We examined the effects of methylprednisolone on gas exchange, pressure-volume curve, lavage fluid inflammatory cell counts, protein content, surfactant pool size, and lung histology in a rat model of paraquat-induced lung injury. Twenty-three adult male Sprague-Dawley rats received intraperitoneal paraquat injection (35 mg/kg) and were randomly divided into three groups: (1). control group received no further treatment; (2). 1-dose methylprednisolone group received a concomitant intraperitoneal methylprednisolone injection (30 mg/kg); (3). 3-dose methylprednisolone group received a concomitant and daily intraperitoneal methylprednisolone injection (30 mg/kg) for three doses. Three days after paraquat injection, the rat was ventilated for 90 min, a static pressure-volume curve and bronchoalveolar lavage was performed, and postmortem histology was examined. Surfactant pool size of the 3-dose methylprednisolone group was significantly increased when compared with the control and 1-dose methylprednisolone groups. Methylprednisolone treatment increased oxygenation and the value was statistically significant for 3-dose methylprednisolone group at 90 min of ventilation. Inflammatory cell counts in bronchoalveolar lavage fluid and lung injury score were decreased as the methylprednisolone dose increased. We conclude that high-dose methylprednisolone treatment increased surfactant pool size and improved lung histology of paraquat-injured lungs but this augmentation could not significantly improve oxygenation throughout the ventilation period.

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.

Overview of tropical nephrology

Tropical nephrology covers renal diseases commonly seen in the tropics and elsewhere and specific tropical renal diseases seen mostly or only in the tropical area. Emphasis in this article is placed on the latter category, which includes renal involvement in tropical infectious diseases, natural toxin poisoning, and environmental renal problems. Pathologically, all renal structures can be affected. There is, therefore, a broad spectrum of pathologic changes, and clinical renal manifestations vary from mild urinary sediment changes to acute renal failure. Inflammatory processes plays an essential role in the pathogenesis of renal involvement in infection and toxin groups. Both models share the same inflammatory pathways through cytokines, chemokines, and mediators. Hemodynamic alterations, immune response, and direct nephrotoxicity are involved in the development of renal lesions.

Effect of vitamin C on plasma total antioxidant status in patients with paraquat intoxication

This study was conducted to evaluate whether vitamin C (VC) was associated with total antioxidant status (TAS) in human plasma and to determine the usefulness of VC on TAS in the treatment of patients with paraquat poisoning. VC and TAS were measured in 56 healthy subjects. Then, various concentrations (1-100 mg/dl) of VC in pooled plasma from 10 volunteers were constructed in vitro and TAS was measured. The VC and TAS were measured in vivo at 0.5, 1, 2, 3, 5, 7, 9, and 11 h after injection of VC (50 mg/kg) in seven volunteers and pharmacokinetic data were calculated. Finally, various amounts of VC (100, 500, 1000, 3000 mg/day, and 3000 mg/8 h) were given to 10 paraquat-poisoned patients for 5 consecutive days, and blood was taken for TAS 1 h after each injection. The means (SD) of VC and TAS in healthy subjects were 2.22 (0.16) mmol/l and 0.48 (0.10) mg/dl, respectively. Positive correlation between VC and TAS was observed in both in vitro and in healthy volunteers. The pharmacokinetic results in vivo were as follows: means (SD) of distribution volume, area under curve, plasma clearance, half life, C(max), and T(max) were 32.0 (4.4) l, 36.4 (11.3) mg h/dl, 2.13 (1.36) l/h, 10.2 (7.8) h, 17.1 (7.1) mg/dl, and 0.64 (0.24) h, respectively. Estimated loading and maintenance doses of VC were 2278 mg and 146 mg/h, respectively. The means of TAS were increased over 5 consecutive days as 2.26, 2.76, 2.81, 3.18, and 3.58 mmol/l in paraquat patients. All patients were recovered within mean (SD) 21.2 (5.4) admission days. Our data suggested that VC was a significant antioxidant as TAS in human plasma and that increased TAS by high doses of VC could be useful as a free radical scavenger for paraquat poisoned patients.

Associations between laboratory parameters and outcome of paraquat poisoning

Paraquat, a non-selective herbicide, is a known fatal substance in humans, and intentional ingestion of paraquat is increasing among Korean suicides. In 1999, 147 subjects admitted to the Institute of Pesticide Poisoning, Soonchunhyang Chunan Hospital, Korea ingested paraquat. Initial routine laboratory tests were conducted and the outcome of paraquat poisoning was categorized as survivor and fatality. Mean amount (S.D.) of ingestion was 54.5 (104.9) ml, and the overall fatality rate was 44.2%. Abnormal liver function (GOT and GPT), renal dysfunction (BUN and creatinine), metabolic acidosis (pH and PaCO(2)), and abnormal urine analysis (RBC, WBC, and protein) had significant odds ratios (ORs) for paraquat fatality (P<0.05). In multiple logistic regression, subjects with liver or renal dysfunction or metabolic acidosis had significant risks of the fatality. Our results determined that initial routine laboratory parameters could be used to predict the outcome of paraquat poisoning and recommended that evaluation of acid-base status and renal and liver function should be conducted and evaluated before intensive therapy.

[Paraquat poisoning. A study of 29 cases and evaluation of the effectiveness of the "Caribbean scheme"]

BACKGROUND

To study clinical aspects of the oral paraquat intoxication and to assess the effectiveness of both the charcoal haemoperfusion and the so-called "Caribbean scheme" (cyclophosphamide, dexamethasone, furosemide and vitamins B and C) to reduce its mortality.

PATIENTS AND METHOD

Retrospective study of 29 consecutive cases admitted to our intensive care unit in 17 years.

RESULTS

a) Twenty five men and four women ingested 20% paraquat solution, either accidentally (4 subjects) or deliberately (25 subjects). The suicidal purpose was particularly strong among men aged 50-66 years. Most of patients had vomits and diarrhoea. All patients developed oral and pharyngeal caustic lesions. Hypokalaemia was detected on admission in 9 patients. Increased levels of serum aminotransferases, bilirubin, amylase or creatinkinase were detected in some patients. Twenty two patients developed acute renal failure and 18 patients respiratory failure. Twenty patients died (ten in the first 48 hours and ten between days 3 and 30); b) charcoal haemoperfusion was performed on 16 patients; 4 of the 16 treated patients survived, versus 5 of the 13 non treated (p = NS), and c) the "Caribbean scheme" was applied on 18 patients. All but one of the 11 subjects who ingested >= 45 ml (treated with the "Caribbean scheme" or not) died. Among those who ingested 45 ml, 8 of the 12 treated patients survived, versus none of the 6 non treated ones (p < 0.05).

CONCLUSIONS

Charcoal haemoperfusion did not reduce mortality of paraquat. The "Caribbean scheme" was associated with a lesser mortality in the subjects who ingested 45 ml of 20% paraquat solution.

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.

Nitric oxide inhalation for paraquat-induced lung injury

BACKGROUND

When ingested, concentrated paraquat can cause either rapid death from multisystem failure and cardiovascular shock or delayed death from progressive pulmonary fibrosis. Diquat ingestion does not usually cause pulmonary fibrosis, but produces early onset acute renal failure.

CASE REPORT

A 52-year-old male ingested approximately 50 mL of a solution containing 13% paraquat and 7% diquat (about 6650 mg of paraquat and 3500 mg of diquat), and subsequently developed adult respiratory distress syndrome and pulmonary fibrosis. Survival prediction employing the criteria of Hart et al. for paraquat plasma levels was 30%. From the probable amount of paraquat ingested, severe toxicity was expected. The clinical course was not consistent with significant diquat toxicity. Treatment included oral Fuller's earth, forced diuresis, hemofiltration, N-acetylcysteine, methylprednisolone, cyclophosphamide, vitamin E, colchicine, and delayed continuous nitric oxide inhalation. The patient recovered and pulmonary function was subsequently normal.

CONCLUSION

It is unclear which, if any, of the above treatments contributed to recovery, but the encouraging outcome suggests a possible benefit of nitric oxide inhalation in paraquat poisoning which deserves further study.

Pulse therapy with cyclophosphamide and methylprednisolone in patients with moderate to severe paraquat poisoning: a preliminary report

BACKGROUND

Severe paraquat poisoning causes considerable morbidity and mortality. High doses of cyclophosphamide and dexamethasone have been used to treat patients with paraquat poisoning, but with mixed results. The use of pulse methylprednisolone and cyclophosphamide was investigated in the treatment of moderately severe paraquat poisoning.

METHODS

During a six-year period 87 patients with paraquat poisoning were admitted to hospital, of whom 33 had moderate to severe intoxication. Seventeen patients received conventional treatment and served as historical controls, and 16 received intravenous infusions of cyclophosphamide 1 g daily for two days and methylprednisolone 1 g daily for three days.

RESULTS

There were no differences between the groups in age, sex, severity of paraquat poisoning (as assessed by urine dithionite tests), or in the time elapsed from ingestion to presentation at hospital or to the beginning of haemoperfusion. No differences were seen in biochemical measurements on the third day after paraquat poisoning. The mortality in the pulse therapy group was lower than that in the control group (4/16 (25%) versus 12/17 (70.6%), p = 0.01). All fatalities were from progressive respiratory failure.

CONCLUSIONS

Pulse therapy with cyclophosphamide and methylprednisolone may be effective in preventing respiratory failure and reducing mortality in patients with moderate to severe paraquat poisoning. Further controlled studies are needed to confirm this and to establish the mechanisms.

Survival after paraquat poisoning in a HIV positive patient

From 1987 to 1994, 31 cases of acute paraquat poisoning were managed in the CHRU of Pointe à Pitre (FWI). Eighteen patients died, 13 survived. Biological indexes accurately predicted patient's outcome in all cases out of one. In the last case biological parameters were misleading: the corresponding patient survived despite consistent clinical and biological prognosis of death. The unexpected survivor was West Indian, male, agricultural worker of 26 years who alleged drunk about 300 ml of gramoxone (20% v/v paraquat) in a suicide attempt. The patient was HIV-infected (Elisa+, Western-Blot+) and presented an AIDS syndrome (CD4 count inferior to 200 cells/mm2) established since 10 months and treated by AZT. We could not identify any other distinguishing features among the unexpected survivor and the rest of the patients. This observation suggests that the immunological status of the patient could explain this protection from paraquat toxicity.

Recovery of respiratory function in survivors with paraquat intoxication

The purpose of this study was to investigate chest radiograms and respiratory function changes, including pulmonary function tests and alveolar-arterial oxygen difference, in survivors with paraquat intoxication. Chest radiograms and pulmonary function tests for 21 paraquat-poisoned patients were performed 10 d after paraquat intoxication; 3 mo later, the tests were repeated in 16 patients who survived. Forced vital capacity, forced expiratory volume in 1 s, diffusing capacity of the lung, and alveolar-arterial oxygen difference were compromised after paraquat intoxication. Forced expiratory volume in 1 s and forced vital capacity correlated significantly with initial platelet counts (r = .453 and .443, respectively) 10 d after intoxication. The alveolar-arterial oxygen difference also correlated significantly with peak serum total bilirubin concentrations (r = .443) and initial platelet counts (r = .469). The follow-up data for respiratory functions forced expiratory volume in 1 s; 74.33 +/- 27.1% versus 97.89 +/- 16.39%; forced vital capacity: 71.44 +/- 26.03% versus 93.22 +/- 13.92%; diffusing capacity of lung: 60.11 +/- 27.61% versus 81.67 +/- 24.56%; alveolar-arterial oxygen difference: 37.95 +/- 24.32 mm Hg versus 7.75 +/- 9.94 mm Hg) and chest radiograms of survivors with moderate to severe paraquat poisoning showed significant improvements 3 mo after intoxication. The results demonstrated that paraquat-induced respiratory function impairments could recover significantly, at least partially, with time. In addition, pulmonary structure damage improved, as shown in the follow-up chest radiographs.

High-dose cyclophosphamide and dexamethasone in paraquat poisoning: a prospective study

Between March 1986 and March 1988, 47 consecutive patients, whose paraquat intoxication was confirmed by urine testing, were enrolled in a prospective study on the treatment of paraquat poisoning. Fourteen received a standard treatment regimen consisting of fluid replacement and oral absorbents, and 33 received high-dose cyclophosphamide and dexamethasone, in addition to standard therapy. The case fatality rate in both treatment groups (63 and 61%) was similar. In addition, all 26 patients whose paraquat serum concentrations were measured and who had a probability of survival of less than 65% according the survival curve of Hart et al. died, regardless of therapy. These included four in the cyclophosphamide/dexamethasone group and two in the standard treatment group who had prior survival probabilities between 50 and 65%. This indicated that the cut-off curve relating mortality and paraquat serum concentrations was similar in both treatment groups. High-dose cyclophosphamide/dexamethasone treatment is unlikely to improve the prognosis of paraquat poisoning.

Paraquat poisoning. An overview of the current status

Paraquat is a bipyridyl compound with no known chronic toxicity or teratogenicity. It is poorly absorbed when inhaled, but causes severe illness when ingested orally, death usually occurring within 2 days of ingestion of 50 mg/kg. At lower doses death may be delayed for several weeks. The toxic compound accumulates in lung tissue where free radicals are formed, lipid peroxidation is induced and nicotinamide adenine dinucleotide phosphate (NADPH) is depleted. This produces diffuse alveolitis followed by extensive pulmonary fibrosis. The most important prognostic indicator is the quantity of paraquat absorbed, as shown by the plasma paraquat concentration. While renal failure will develop in the majority of those patients who eventually die, it may not, if present alone, indicate a fatal outcome. The absence of caustic burns in the upper digestive tract indicates a good prognosis. Treatment of paraquat poisoning remains ineffective, but Fuller's earth, activated charcoal and resins may prevent some absorption of the toxin. When tubular necrosis occurs, renal excretion of the compound decreases rapidly. A 3-compartment pharmacokinetic model has been described following ingestion of tracer doses including a 'deep' compartment for active pulmonary accumulation. Haemodialysis, haemoperfusion and forced dialysis have been attempted, with no clear improvement in survival rates. Superoxide dismutase, glutathione peroxidase, N-acetylcysteine and other 'free radical scavengers' have failed to alter the outcome in poisoned patients. Other theoretical treatments, such as deferoxamine, immunotherapy, NADPH repletion and lung transplantation still require clinical validation.

Effect of ambroxol of neutrophil chemotaxis in vitro

Ambroxol hydrochloride has been shown to protect the lung from damage by polymorphonuclear leucocyte (PMN). In view of this observation we have studied the effect of Ambroxol on PMN chemotaxis using a variety of chemoattractants. The PMN response was inhibited 50-80% by preincubating the cells with concentrations of 10(-4) M Ambroxol. There was no evidence of PMN killing by the drug at concentration of 10(-3) M. The results suggest that Ambroxol my have a role in the management of patients whose chronic lung damage is due to excess PMN recruitment.

N-acetylcysteine in paraquat toxicity: toxicological and histological evaluation in rats

The therapeutic effect of N-acetylcysteine (NAC) in paraquat-treated rats was investigated. The animals were divided into four groups: A = control; B = NAC; C = paraquat; D = NAC + paraquat. In the appropriate groups, paraquat 20 mg/kg body weight was administered intraperitoneally and 1% NAC solution was provided as drinking water. All surviving rats were killed on the seventh day after paraquat exposure. The lungs were graded histologically on the basis of oedema and cellular infiltration. On histological examination, the lungs of poisoned rats that had received NAC displayed a tendency towards less oedema and cellular infiltration than those of poisoned rats not treated with NAC. It is concluded that NAC might afford some therapeutic effect against paraquat toxicity in rats.

Selective inhibition of bipyridyl-stimulated NADPH oxidation by ascorbic acid

The effect of the bipyridyl herbicides, paraquat and diquat (0.01-1.0 mM), on NADPH oxidation was determined in vitro using rat lung microsomal preparations. Experiments were performed in the absence of mixed function oxidation (MFO) substrates, in the presence of substrates (ethylmorphine or benzphetamine), and also in the presence of ascorbic acid (0.1-10.0 mM). NADPH oxidation was stimulated by both herbicides in the absence or presence of either substrate in a concentration-dependent manner. When ascorbic acid was included in incubations along with either bipyridyl, the stimulated rate of NADPH oxidation decreased in the presence of benzphetamine but the stimulation was unaltered in the presence of ethylmorphine or in the absence of substrate. These studies indicate that ascorbic acid may offer some protection from bipyridyl-mediated NADPH oxidation in rat lung microsomal fractions, but that protection appears to be dependent upon the simultaneous presence of specific MFO substrates.

Paraquat lung: is there a role for radiotherapy?

We have previously reported the clinical course of a patient poisoned with paraquat who was treated with whole lung irradiation and who survived severe pulmonary damage. Four further cases are reported who were much more severely poisoned and who died despite early pulmonary irradiation. There is no definite evidence that this or any other form of cytotoxic therapy can influence the course of paraquat lung. As there is no adequate laboratory model, further investigation of such therapy should be in the context of a prospective clinical trial. Treatment of only one lung would allow rapid identification of a therapeutic effect of irradiation.