A new statistical approach to the prognostic significance of plasma paraquat concentrations

The efficacy of high doses of vitamin C in patients with paraquat poisoning

Paraquat (PQ) poisoning is an extremely difficult condition to manage clinically because of the lack of effective treatments. The purpose of this study was to assess the effect of high doses of vitamin C in combination with anti-inflammatory and immunosuppressant therapy in patients with PQ poisoning. The medical records of 134 patients who presented to the emergency department within 24 hours after PQ poisoning were reviewed retrospectively. The 57 patients presented between January 2004 and September 2005 were group 1; they received pulse therapy, which included cyclophosphamide and methylprednisolone, followed by the administration of dexamethasone over 2 weeks. The 77 patients that presented between October 2005 and January 2008 were group 2; they received the above-mentioned therapy and high-dose vitamin C for 2 weeks. There was no difference in the distribution of baseline variables between the 2 groups. However, group 2 showed a significant reduction in acute kidney injury related to PQ. Furthermore, a multivariate logistic regression analysis showed that the addition of vitamin C to the treatment was significantly associated with an increased survival of the patients. Larger trials will be needed to verify the effect of high-dose vitamin C on survival in patients with PQ poisoning.

Glucocorticoid with cyclophosphamide for paraquat-induced lung fibrosis

BACKGROUND

Paraquat is an effective and widely used herbicide but is also a lethal poison. In many developing countries paraquat is widely available and inexpensive, making poisoning prevention difficult. However most of the people who become poisoned from paraquat have taken it as a means of suicide.Standard treatment for paraquat poisoning both 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 is being developed and studied.

OBJECTIVES

To assess the effects of glucocorticoid with cyclophosphamide on mortality in patients with paraquat-induced lung fibrosis.

SEARCH STRATEGY

To identify randomised controlled trials on this topic, we searched the Cochrane Injuries Group's Specialised Register (searched 15 Sept 2009), CENTRAL (The Cochrane Library 2009, Issue 3), MEDLINE (Ovid SP) (1950 September Week 1 2009), EMBASE (Ovid SP) (1980 to 2009 Week 37), ISI Web of Science: Science Citation Index Expanded (SCI-EXPANDED) (1970 to Sept 2009), ISI Web of Science: Conference Proceedings Citation Index - Science (CPCI-S) (1990 to Sept 2009), Chinese bio-medical literature & retrieval system (CBM) (1978 to Sept 2009), Chinese medical current contents (CMCC) (1995 to Sept 2009), and Chinese medical academic conference (CMAC) (1994-Sept 2009). The searches were completed in September 2009.

SELECTION CRITERIA

Randomised controlled trials (RCTs) were included in this review. All patients were to receive standard care, plus the intervention or control. The intervention was glucocorticoid with cyclophosphamide in combination versus a control of a placebo, standard care alone, or any other therapy in addition to standard care.

DATA COLLECTION AND ANALYSIS

The mortality risk ratio (RR) and 95% confidence interval (CI) was calculated for each study on an intention-to-treat basis. Data for all-cause mortality at final follow-up were summarised in a meta-analysis using a fixed-effects model.

MAIN RESULTS

This systematic review includes three trials with a combined total of 164 participants who had moderate to severe paraquat poisoning. Patients who received glucocorticoid with cyclophosphamide in addition to standard care had a lower risk of death at final follow-up than those receiving standard care only (RR 0.72 (95% CI 0.59 to 0.89)).

AUTHORS' CONCLUSIONS

Based on the findings of three small RCTs of moderate to severely poisoned patients, glucocorticoid with cyclophosphamide in addition to standard care may be a beneficial treatment for patients with paraquat-induced lung fibrosis. To enable further study of the effects of glucocorticoid with cyclophosphamide for patients with moderate to severe paraquat poisoning, hospitals may provide this treatment as part of an RCT with allocation concealment.

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.

Failed rescue therapy with rapamycin after paraquat intoxication

INTRODUCTION

Ingestion of large quantities of paraquat leads to irreversible, often fatal pulmonary fibrosis. Case presentation. A 50-year-old man (body weight of 78.6 kg) ingested 500 mL Gramoxone containing 200 g/L of paraquat in a suicide attempt. The patient did not seek medical attention until 15 h after ingestion. Initial treatment consisted of the administration of intravenous methylprednisolone, 250 mg once daily. Seventy-two hours after ingestion the patient was transferred to our tertiary care center. Paraquat concentration was 0.2 mg/L in the serum and urinary concentration was 4.42 mg/L. Antioxidative therapy including the administration of acetylcysteine and an anti-inflammatory therapy employing methylprednisolone (1 g/day) was started. Extended daily dialysis was initiated. As the high plasma concentration of paraquat indicated a 100% predicted mortality, we expanded treatment strategies by using the antiproliferative agent rapamycin. A dose of 8 mg/day was started 72 h after the intoxication. Maximum rapamycin concentrations amounted to 12.9 microg/L. Despite these efforts, the patient died on day 18 after intoxication from respiratory failure caused by severe pulmonary fibrosis.

CONCLUSION

Despite theoretical considerations suggesting the use of rapamycin in paraquat poisoning, the substance failed to halt the progression of pulmonary fibrosis in this case.

Intravenous paraquat poisoning

Paraquat is a substance that is highly poisonous to humans. Oral ingestion is the most common pathway of poisoning. Intravenous paraquat poisoning is rare and is strongly associated with attempted suicide. The clinical presentations of such a scenario would appear to be quite different from those of oral ingestion. Herein, we present a case of an intravenous drug abuser who injected paraquat in an effort to commit suicide. He received hemoperfusion and intravenous cyclophosphamide treatment and parenteral pulse therapy with methylprednisolone. Nevertheless, he suffered from dyspnea at around 48 hours post-exposure. His condition improved transiently, but he eventually died from severe hypoxia. The findings from our case and those of previously reported cases indicate the grave prognosis and lack of effective management of intravenous paraquat poisoning.

Delayed immunosuppressive treatment in life-threatening paraquat ingestion: a case report

INTRODUCTION

Combined glucocorticoids and cyclophosphamide pulse therapy showed promising results in moderate-to-severe paraquat poisonings to reduce life-threatening respiratory complications. Its benefit has been observed when given early in the course of poisoning; however, whether its delayed administration remains beneficial is unknown.

CASE REPORT

We describe a 23-year-old male who ingested 70 mL of a commercialized concentrate formulation with 20% weight/volume paraquat in a suicide attempt. Within 24 hours from paraquat ingestion, he presented most of the indicators of poor outcome, including gastritis, early renal dysfunction, dark blue urine colorimetric dithionite test, and marked plasma paraquat concentrations (0.56 microg/mL at 13 hours, and 0.41 microg/mL at 24 hours after ingestion). The patient received early gastrointestinal decontamination and aggressive supportive treatments. However, due to a rapidly progressive severe pulmonary infection, glucocorticoids and cyclophosphamide were delayed until day 14. Interestingly, our patient survived with mild respiratory sequelae despite poor initial prognosis.

DISCUSSION

This observation suggests the potential benefit of immunosuppressive pulse therapy, even if administered 14 days after paraquat ingestion, and highlights the role of paraquat-induced alveolitis in the development of fibrosis.

CONCLUSION

Combined glucocorticoids and cyclophosphamide should be considered in moderate-to-severe paraquat poisonings, even if delayed.

The level and clinical significance of pancreatic enzymes in survivors of acute paraquat poisoning

INTRODUCTION

Acute paraquat poisoning is often fatal. When ingested, paraquat affects multiple organs including the lung, gastrointestinal tract, pancreas, kidney, heart, and central nervous system. Our center previously found that initial pancreatic function was related to the prognosis of patients with acute paraquat poisoning. However, pancreatic injury after paraquat intoxication has been incompletely studied.

METHODS

This study analyzed the clinical outcome and extent of pancreatic injury in 34 survivors of acute paraquat poisoning. Paraquat exposure was assessed based on a quantitative measure of the plasma level of paraquat by high-performance liquid chromatography. The subsequent variations in the level of pancreatic enzymes, clinical symptoms, and abdominal computed tomography were obtained. Outcomes after acute paraquat poisoning were categorized as pancreatic enzyme elevation group (elevation group: amylase >160 IU/L and lipase >100 IU/L) and nonelevation group.

RESULTS

Pancreatic enzyme elevations occurred in seven cases (20.6%), and the level of pancreatic enzymes peaked at day 7. The elevation in pancreatic enzymes after paraquat ingestion was positively correlated with the plasma paraquat level (p < 0.05 at days 4 and 7). Creatinine was higher in the elevation group. Abdominal computed tomography of the seven cases showed no evidence of pancreatitis, and significant abdominal pain was not observed.

DISCUSSION

Pancreatic enzyme elevation reflects the systemic toxicity and multiorgan involvement following acute paraquat poisoning.

CONCLUSIONS

Pancreatic injury was subtle and the elevation of pancreatic enzymes in survivors is clinically benign.

Serum total antioxidant statuses of survivors and nonsurvivors after acute paraquat poisoning

INTRODUCTION

The plasma paraquat (PQ) concentration is an excellent prognostic indicator. However, at the bedside, it is difficult to predict survivors even with known PQ concentrations. We examined the association of total antioxidant status (TAS) in serum to clinical outcome in patients with acute PQ intoxication.

METHODS

After acute PQ intoxication, 296 patients were admitted to the Institute of Pesticide Poisoning, Soonchunhyang University Cheonan Hospital, from January through December 2007. Serum total antioxidant levels in emergency department were compared between a survivor group and a nonsurvivor group.

RESULTS

Age, the amount of PQ ingested, plasma PQ concentration, leukocyte count, blood urea nitrogen (BUN), serum creatinine, uric acid, aspartate aminotransferase, alanine aminotransferase (ALT), and amylase in the emergency department were individually associated with the clinical outcome (p < 0.001), but TAS was not. Multiple logistic regression found the odds ratio (95% confidence interval) to be 10.79 (3.45-33.74) for plasma PQ concentration, but 0.43 (0.02-8.52) for TAS in serum. TAS was not associated with survival.

CONCLUSION

TAS in serum was not a significant influence on the clinical outcome in patients with acute PQ intoxication.

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.

Comparison between kidney and hemoperfusion for paraquat elimination

The mortality rate of acute paraquat (PQ) poisoning depends on the PQ concentration in the blood. It has been shown that the kidneys eliminate PQ effectively. However, early renal function deterioration is frequently observed in acute PQ intoxication. This study is designed to compare the efficacy of PQ elimination with hemoperfusion (HP) and kidneys, taking into account the functional deterioration of the kidneys. The amount of renal and HP excretion of PQ were measured during the procedure of HP in patients with acute PQ intoxication. The PQ clearance and the actual amount of PQ elimination by the HP cartridge during the HP procedure were 111+/-11 mL/min (range; 13.2-162.2 mL/min) and 251.4+/-506.3 mg (range; 4.6-1,655.7) each. While, the renal clearance and actual amount of renal elimination of PQ was 79.8+/-56.0 mL/min (range; 9.7-177.0) and 75.4+/-73.6 mg (range; 4.9-245.8). As the creatinine clearance decreased, the PQ elimination by HP was as effective as or more effective than the renal elimination. In conclusion, early HP must be provided for life saving treatment in patients with acute PQ intoxication.

Association between plasma paraquat level and outcome of paraquat poisoning in 375 paraquat poisoning patients

OBJECTIVES

Paraquat poisoning by ingestion is often fatal. Many studies have investigated treatment modalities and predictor parameters, but there is no standard treatment. Plasma paraquat concentration seems a valid predictable parameter of survival. In order to achieve uniform treatment, including extracorporeal elimination and antioxidant therapy, the outcome of paraquat poisoning based on plasma paraquat level needs to be investigated.

METHODS

This study included 375 paraquat poisoning patients who were diagnosed by means of plasma paraquat concentration within 24 hours after ingestion in the Institute of Pesticide Poisoning of Soonchunhyang University Cheonan Hospital, Korea, from January 2005 to December 2006. All patients were treated according to a uniform protocol including extracorporeal elimination and antioxidant therapy. Plasma paraquat concentration was measured by high-performance liquid chromatography.

RESULTS

The mean age of the paraquat-intoxicated patients was 48.42 +/- 6.75. One hundred ten patients (29.3%) survived. The upper limit of plasma paraquat concentration in survivors was 2.64 at 3 hour. All patients with plasma paraquat level above 3.44 died. The minimum paraquat level of the deaths was very low (0.12 microg/ml at 5 hours; 0.02 microg/ml at 12 hours; 0.01 microg/ml at 24 hours).

CONCLUSIONS

Our data showed that plasma paraquat concentration is good predictor of survivors but is not good predictor of non-survivors in the low plasma paraquat level.

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.

Clinical Implications of the Ethane in Exhaled Breath in Patients With Acute Paraquat Intoxication

STUDY OBJECTIVES

Pulmonary fibrosis due to lipid peroxidation is a major symptom of paraquat intoxication. Ethane in the expired breath (exEth) reflects lipid peroxidation and may be a measure of the damage effected by oxygen radicals in acute lung injury. The purpose of this study was to evaluate the clinical efficacy of exEth as a measure of exposure to paraquat and as an indicator of lung damage.

DESIGN

Exposure levels were evaluated by the amount ingested, semiquantitative measurement of urine paraquat levels, and plasma paraquat concentration. End-tidal breath was collected for measurement of ethane 24 h after paraquat ingestion. Renal function and blood gas analyses were conducted on the same day as the breath collection, and the final clinical outcome was defined as either recovery or death. Associations between exEth and paraquat exposure profiles and clinical outcomes were assessed using linear regression models.

PATIENTS

Twenty-one patients poisoned by paraquat were selected for the study during 2001 and 2002.

RESULTS

exEth could not be used as a predictor of laboratory parameters such as Pa(O2), Pa(CO2), serum creatinine, and lung injury (as graded by high-resolution CT). A logistical analysis revealed that only the amount of paraquat ingested was a significant predictor of fatality (p = 0.021). The strength of the association between exEth and fatality was unaffected by the addition of potential confounders such as age, sex, and time interval and paraquat concentration.

CONCLUSION

exEth cannot be used as either an independent predictor of survival or a specific marker of lung injury in patients with acute 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.

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.

Combined methylprednisolone and dexamethasone therapy for paraquat poisoning

OBJECTIVE

To report a severe case of paraquat poisoning successfully treated with repeated-pulse therapy of methylprednisolone.

DESIGN

Case study.

SETTING

University Hospital, Lin-Kou Medical Center, Taipei, Taiwan, Republic of China.

PATIENTS

A 60-yr-old man with paraquat poisoning with severe acute renal failure (serum creatinine level of 11.8 mg/dL and serum paraquat level of 3.66 microg/mL at 10 hrs after ingestion) and severe hypoxemia (Pao2, 66.6 mm Hg).

INTERVENTION

Repeated 3-day pulse therapy with methylprednisolone, one course of 2-day cyclophosphamide, and a high dose of dexamethasone for 33 days. MEASUREMENTS AND MAIN OUTCOME: Arterial blood gas analysis was obtained regularly. A chest radiography was obtained every week. The arterial blood oxygen concentrations dramatically elevated from 66 mm Hg to 97 mm Hg, and the chest radiographs markedly improved after repeated-pulse therapy with anti-inflammatory agents and cyclophosphamide.

CONCLUSIONS

We successfully treated a severe paraquat poisoned patient with repeated methylprednisolone pulse therapy and prolonged dexamethasone treatment. This case demonstrates that the severe inflammation, not the fibrosis, of the lungs plays a major role in the lethal hypoxemia of patients with paraquat poisoning during the subacute period and confirms our previous hypotheses. Clearly, the use of anti-inflammatory therapy to treat paraquat-poisoned patients needs further evaluation; however, anti-inflammatory therapy may be an effective treatment after failure of standard therapies.

Predictors of survival after acute paraquat poisoning

Acute paraquat poisoning is often fatal. Many studies have investigated successful treatment modalities, but no standard treatment yet exists. The purpose of this study was to determine the predictors of survival after acute paraquat poisoning in 602 patients. The paraquat exposure was assessed based on the amount of ingested paraquat and a semiquantitative measure of the urine level of paraquat. Initial clinical parameters including vital signs, hemoglobin, white-blood-cell count, pH, PaCO2, PaO2, blood urea nitrogen, creatinine, aspartate aminotransferase, alanine aminotransferase, total bilirubin, amylase, and glucose were obtained at the time of arrival at the emergency room. Outcomes after acute paraquat poisoning were categorized as survivors and nonsurvivors. Multiple logistic regression analysis was applied to assess the predictors of survival after acute paraquat poisoning. Some patients (55.5%) survived after oral ingestion of paraquat, whereas all those exposed to paraquat percutaneous or inhalational route survived. The amount of paraquat (24.5% concentrate of 1,1'-dimethyl-4,4'-bipyridium dichloride) ingested was 45.6 +/- 74.1 mL (mean +/- SD). In addition to degree of paraquat exposure, survival after acute paraquat poisoning was associated with age, respiratory rate, pH, PaCO2, hemoglobin, white-blood-cell count, blood urea nitrogen, amylase, and the number of failed organs in multiple logistic regression analysis. In conclusion, young age, percutaneous or inhalational route, exposure to less paraquat, and lesser degrees of leukocytosis, acidosis, and renal, hepatic, and pancreatic failures on admission are good prognostic factors of survival after acute paraquat poisoning.

Failure of continuous venovenous hemofiltration to prevent death in paraquat poisoning

Paraquat poisoning is characterized by multiorgan failure and pulmonary fibrosis with respiratory failure. Multiorgan failure with circulatory collapse is a major cause of early death within 3 days of paraquat ingestion. Recent studies suggested that continuous venovenous hemofiltration (CVVH) had a role in the treatment of multiorgan failure by promoting hemodynamic stability. We therefore evaluated the effect of prophylactic CVVH in 80 patients with paraquat poisoning (August 1996 to February 1999). The amount ingested was 2.1 +/- 1.0 mouthfuls (as 20% concentrate). All patients were treated with hemoperfusion (HP; duration, 6.4 +/- 3.0 hours) within 24 hours of ingestion and then randomly assigned to the HP-alone or HP-CVVH group. Forty-four patients underwent HP only, and 36 patients underwent CVVH (duration, 57.4 +/- 31.3 hours; ultrafiltration volume, 40.2 +/- 4.8 L/d) after HP. Although time to death after ingestion was significantly longer in the HP-CVVH than HP group (5.0 +/- 5.0 versus 2.5 +/- 2.1 days; P < 0.05), there was no difference in mortality rates between the two groups (66.7% versus 63.6%; P = 0.82). In the HP group, early circulatory collapse was a major cause of death compared with the HP-CVVH group, in which late respiratory failure was a major cause of death. In conclusion, prophylactic CVVH after HP prevented early death caused by circulatory collapse and prolonged survival time. However, it could not prevent late death caused by respiratory failure and did not provide a survival benefit in acute paraquat poisoning.

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.

Therapeutic drug monitoring in drug overdose

The treatment of poisoned patients is still largely defined by history, clinical assessment and interpretation of ancillary investigations. Measurement of drug concentrations is clinically important for relatively few compounds. Most measurements form an adjunct to and should not be considered a substitute for clinical assessment. Drug concentrations are particularly important for those compounds where the concentration is predictive of serious toxicity in an otherwise asymptomatic patient.

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.

Acute paraquat poisoning: increased toxicity in one case with high alcohol intake

Human paraquat poisoning from accidental or intentional ingestion is very often fatal. According to the amount of paraquat involved, death can occur within hours or weeks following ingestion. The inefficacy of the various treatments undertaken have led to determine prognostic factors based upon the evolution of plasma and urine paraquat concentrations or of usual biochemical parameters. We report one case of acute poisoning which, although the ingested dose of paraquat was not massive (< 50 mg/kg-1) and the severity indices were in favour of a delayed fatal outcome, has ended in an early death. The high blood alcohol level of the patient (3.34 g l-1) seems to be the main cause of the precocity of this death (86th hour).

Effects of Fuller's Earth and activated charcoal on oral absorption of paraquat in rabbits

1. Thirty male rabbits of local strain (weighing 1.5-2 kg) were divided into five groups. Four groups were treated with an oral dose of paraquat, which was followed by either Fuller's Earth or activated charcoal 0.5 or 2.0 h later. The remaining group acted as the control group and was treated only with an oral dose of paraquat. The dose of paraquat was 20.0 mg/kg given in a concentration of 20.0 mg/mL. 2. Both adsorbents were administered in 15 mL normal saline as a 30% slurry. Blood was sampled from the ear vein 0.5, 1, 2, 4, 8 and 24h after the administration of paraquat. 3. Paraquat concentration was determined spectophotometrically at 600 nm by comparing against a standard curve of paraquat obtained by the addition of standard paraquat into normal rabbit serum and extracting interfering substances with ether. 4. The results of the present study show that either adsorbent can bring down the serum paraquat level. There was no significant difference found in the effectiveness of either adsorbent. 5. It is concluded that the administration of an adsorbent as early as possible will help in the reduction of paraquat absorption from the gastrointestinal tract. 6. Activated charcoal is still effective in lowering serum paraquat concentration when given more than 1 h after ingestion of paraquat.

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.

Different distribution of paraquat and diquat in human poisoning cases after ingestion of a combined herbicide

This report describes a slight difference in the rate of decrease of serum paraquat and diquat concentrations in eight human cases of poisoning by the herbicide PreegloxL (containing paraquatCl2, 5% and diquatBr2, 7%) and the distribution of each in three autopsied cases. There was no variation between the serum concentrations of paraquat and diquat within 24 h after ingestion, but paraquat remained at a slightly higher concentration than diquat after more than 24 h. The decrease of urinary paraquat and diquat concentrations was almost the same during the 24-h determination period. In three autopsied cases, diquat concentrations in the tissues were relatively lower than those of paraquat, except in bile. Paraquat and diquat were unevenly distributed in various tissues and fluids, but the distribution patterns of each in any particular tissues were quite similar. As no difference was observed in the decrease of urinary paraquat and diquat, the much higher concentration of diquat in bile indicates that bile may be one of the effective factors in lowering the concentration of diquat in serum and in tissues of the human body long after ingestion.

Inhaled nitric oxide in advanced paraquat intoxication

No effective treatment is available for adult respiratory distress syndrome, pulmonary hypertension and progressive lung fibrosis in severe paraquat poisoning. A potentially beneficial effect of nitric oxide inhalation on the mean pulmonary artery pressure and gas exchange in a subject with advanced paraquat intoxication is reported. Eight days after the suicidal ingestion of an unknown dose of paraquat, a 52-year-old female had a PaO2 < or = 50 mm Hg despite ventilation with an FiO2 of 1 and a positive end-expiratory pressure of 14 to 18 cm H2O. After administration of 25 ppm nitric oxide, PaO2 increased and the mean pulmonary artery pressure and the right-to-left shunt decreased. Discontinuation of nitric oxide resulted in rapid reversal. Ventilatory function was stabilized for three days during nitric oxide inhalation but the patient developed massive pleural effusions and died on d 11 during an interruption of nitric oxide therapy. The response of serious paraquat intoxications to nitric oxide therapy may merit further study. A remarkable post-mortem finding was extensive myonecrosis supporting prolonged muscular retention of paraquat with toxic myopathy or neuromyopathy as a late manifestation of paraquat toxicity.

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.

Effect of ethanol on the disposition of paraquat

Rabbits that received paraquat (200 mg/kg) and ethanol (1.0-3.8 g/kg) by gavage resulted in shorter median survival times and higher mortality rates than those dosed with paraquat alone. Plasma paraquat levels in rabbits dosed with ethanol before, after and concurrently with ingestion of paraquat were significantly higher when compared with animals without ethanol intake. Furthermore, substantial differences in paraquat kinetics, higher AUC, lower total clearance (CL/F) and volume of distribution (V/F) were seen in the ethanol-paraquat group. The effect of ethanol on acute paraquat toxicity is, at least in part, associated with the increase in paraquat absorption and/or the decrease in paraquat excretion.

Pre-embarkment prognostication for acute paraquat poisoning

1. In order to assess which laboratory parameters could be related to the prognosis of patients with acute paraquat poisoning, we reviewed the medical records of 160 patients who had ingested paraquat in an attempt at suicide. 2. Serum creatinine and potassium concentrations, arterial blood bicarbonate and base excess levels, arterial blood pH, volume of paraquat ingested and the strength of the urinary paraquat qualitative test (sodium dithionate colour reaction) on admission in the surviving patients were significantly different from those of the patients who died within 48 h of ingestion. 3. The relationship of the quantity Eq1 defined as: Eq1 = ([K+] x [HCO3-])/([Cre] x 0.088) (mEq l-1) against the interval of time after ingestion to admission (T) had a significant correlation with prognosis (P less than 0.01). Patients with Eq1 greater than (1500 - 399 X LogT) had a 90% survival rate, Eq1: (930 - 399 X LogT) less than Eq1 less than or equal to (1500 - 399 X LogT) 38% and Eq1 less than or equal to (930 - 399 X LogT) 3%, P less than 0.01.