Clinical outcomes and kinetics of propanil following acute self-poisoning: a prospective case series

Novel Bifunctional Amidase Catalyzing the Degradation of Propanil and Aryloxyphenoxypropionate Herbicides in Rhodococcus sp. C-1

Propanil residues can contaminate habitats where microbial degradation is predominant. In this study, an efficient propanil-degrading strain C-1 was isolated from paddy and identified as Rhodococcus sp. It can completely degrade 10 μg/L-150 mg/L propanil within 0.33-10 h via the hydrolysis of the amide bond, forming 3,4-dichloroaniline. A novel bifunctional amidase, PamC, was identified in strain C-1. PamC can catalyze the hydrolysis of the amide bond of propanil to produce 3,4-dichloroaniline as well as the hydrolysis of the ester bonds of aryloxyphenoxypropionate herbicides (APPHs, clodinafop-propargyl, cyhalofop-butyl, fenoxaprop-p-ethyl, fluazifop-p-butyl, haloxyfop-p-methyl, and quizalofop-p-ethyl) to form aryloxyphenoxypropionic acids. Molecular docking and site-directed mutagenesis confirmed that the catalytic triad Lys82-Ser157-Ser181 was the active center for PamC to hydrolyze propanil and cyhalofop-butyl. This study presents a novel bifunctional amidase with capabilities for both amide and ester bond hydrolysis and enhances our understanding of the molecular mechanisms underlying the degradation of propanil and APPHs.

Characterization of a novel amidohydrolase with promiscuous esterase activity from a soil metagenomic library and its application in degradation of amide herbicides

Amide herbicides have been extensively used worldwide and have received substantial attention due to their adverse environmental effects. Here, a novel amidohydrolase gene was identified from a soil metagenomic library using diethyl terephthalate (DET) as a screening substrate. The recombinant enzyme, AmiH52, was heterologously expressed in Escherichia coli and later purified and characterized, with the highest activity occurring at 40 ℃ and pH 8.0. AmiH52 was demonstrated to have both esterase and amidohydrolase activities, which exhibited highly specific activity for p-nitrophenyl butyrate (2669 U/mg) and degrading activity against several amide herbicides. In particular, it displayed the strongest activity against propanil, with a high degradation rate of 84% at 8 h. A GC-MS analysis revealed that propanil was transformed into 3,4-dichloroaniline (3,4-DCA) during this degradation. The molecular interactions and binding stability were then analyzed by molecular docking and molecular dynamics simulation, which revealed that several key amino acid residues, including Tyr164, Trp66, Ala59, Val283, Arg58, His33, His191, and His226, are involved in the specific interactions with propanil. This study provides a function-driven screening method for amide herbicide hydrolase from the metagenomic libraries and a promising propanil-degrading enzyme (AmiH52) for potential applications in environmental remediation.

Experimental and computational approaches to characterize a novel amidase that initiates the biodegradation of the herbicide propanil in Bosea sp. P5

The herbicide propanil and its major metabolite 3,4-dichloroaniline (3,4-DCA) are difficult to biodegrade and pose great health and environmental risks. However, studies on the sole or synergistic mineralization of propanil by pure cultured strains are limited. A two-strain consortium (Comamonas sp. SWP-3 and Alicycliphilus sp. PH-34), obtained from a swep-mineralizing enrichment culture that can synergistically mineralize propanil, has been previously reported. Here, another propanil degradation strain, Bosea sp. P5, was successfully isolated from the same enrichment culture. A novel amidase, PsaA, responsible for initial propanil degradation, was identified from strain P5. PsaA shared low sequence identity (24.0-39.7 %) with other biochemically characterized amidases. PsaA exhibited optimal activity at 30 °C and pH 7.5 and had k_cat and K_m values of 5.7 s^-1 and 125 μM, respectively. PsaA could convert the herbicide propanil to 3,4-DCA but exhibited no activity toward other herbicide structural analogs. This catalytic specificity was explained by using propanil and swep as substrates and then analyzed by molecular docking, molecular dynamics simulation and thermodynamic calculations, which revealed that Tyr138 is the key residue that affects the substrate spectrum of PsaA. This is the first propanil amidase with a narrow substrate spectrum identified, providing new insights into the catalytic mechanism of amidase in propanil hydrolysis.

Overhauling the ecotoxicological impact of synthetic pesticides using plants' natural products: a focus on Zanthoxylum metabolites

The reduction in agricultural production due to the negative impact of insects and weeds, as well as the health and economic burden associated with vector-borne diseases, has promoted the wide use of chemicals that control these "enemies." However, the use of these synthetic chemicals has been recognized to elicit negative impacts on the environment as well as the health and wellbeing of man. In this study, we presented an overview of recent updates on the environmental and health impacts of synthetic pesticides against agro-pest and disease vectors while exhaustive reviewing the potentials of natural plant products from Zanthoxylum species (Rutaceae) as sustainable alternatives. This study is expected to spur further research on exploiting these plants and their chemicals as safe and effective pesticide entities to minimize the impact of their chemical and synthetic counterparts on health and the environment.

A New Treatment Approach for Acute Propanil Poisoning: A Case Report

Propanil is a widely used herbicide in agriculture and is also an important cause of poisoning in Sri Lanka. Incidence is around 2% and is commonly reported as self-poisoning. Although it is classified as an agent with low to medium toxicity, severe poisoning can cause lethal outcome and death especially when there is a limited medical facility. We describe a case of severe Propanil poisoning who was successfully treated in a peripheral hospital with available facilities.

Anaerobic Degradation of Propanil in Soil and Sediment Using Mixed Bacterial Culture

The widespread use of the herbicide, propanil, causes severe environmental problems. In this study, the effects of propanil on the bacterial community in a sediment slurry were determined. Moreover, the degradation of the herbicide by pure and mixed cultures was first conducted under anaerobic conditions. The results showed that propanil caused significant changes in the bacterial community under anaerobic conditions. Four bacterial strains, i.e., Geobacter sp. Pr-1, Paracoccus denitrificans Pr-2, Pseudomonas sp. Pr-3, and Rhodococcus sp. Pr-4, isolated from the an enrichment sediment slurry were the first pure cultures that degraded propanil and 3,4-dichloroaniline (3,4-DCA) under anaerobic conditions. Some individual isolates showed the slow degradation of propanil and 3,4-DCA, but the mixture of the four strains increased the degradation rates of both compounds. The mixed culture of these isolates transformed more than 90% of propanil within 10 days in liquid media with the amendment of dextrose, glucose, or acetate. The determination of degradation pathway showed that propanil was transformed to 3,4-DCA and some other products before degrading completely. This study provides valuable information on the effects of propanil on the bacterial community and the synergistic degradation of propanil under anaerobic conditions.

Efficient activation of oxone by pyrite for the degradation of propanil: Kinetics and degradation pathway

Pyrite (FeS₂) is an abundant sulfide-associated iron mineral that exists in the earth. In this study, the pyrite/oxone process was demonstrated to be an effective approach for the catalytic degradation of propanil, where more than 90% decay ([propanil]₀ = 0.01 mM) was achieved within 15 min. Typically, the effects of various experimental parameters, including catalyst loading, oxone dosage, propanil concentration, and initial solution pH, were examined. Two optimal reaction pH values were observed at pH 9.1 and pH 2.9. The generated SO₄－ and OH were verified to be the dominant reactive radicals and primarily responsible for the propanil degradation. Both Fe(II) regeneration and sulfur conversion play an important role in oxone activation mechanism and effectively aid the catalytic activity of pyrite. Different co-existing natural water constituents exert dissimilar effects on the pyrite/oxone process. Additionally, the reusability test of pyrite exhibited a reasonable catalytic activity. The pyrite/oxone process was proven efficient in terms of propanil mineralization. A series of reaction intermediates was detected via four major degradation pathways. Overall, the pyrite/oxone process could be a promising approach for the removal of organic compounds in water.

Cytogenotoxic effect of propanil using the Lens culinaris Med and Allium cepa L test

Propanil can produce methemoglobinemia, hemolytic anemia, hepatotoxicity, metabolic disorder and nephrotoxicity. It also has a genotoxic effect, although it is not listed as a carcinogen and it continues to be applied excessively throughout the world. Consequently, in this study the cytogenotoxic effect of propanil was evaluated, using apical root cells of Allium cepa and Lens culinaris. In which, L. culinaris seeds and A. cepa bulbs were subjected to 6 treatments with propanil (2, 4, 6, 8, 10 and 12 mg L^-1) and to distilled water as control treatment. Subsequently, the root growth was measured every 24 h for 3 days. Next, the mitotic index and cellular anomalies were determined. Whereby, decreased root development was observed in all treatments. Likewise, greater inhibition of mitosis was evidenced in L. culinaris compared to A. cepa. In addition, chromosomal abnormalities, such as nucleus absence, sticky chromosomes in metaphase and binucleated cells, were present in most of the treatments. Thus, the presence of micronuclei and the results of L. culinaris, indicate the high cytogenotoxicity of propanil and the feasibility of this species as bioindicator.

Development and application of fluorescence sensor and test strip based on molecularly imprinted quantum dots for the selective and sensitive detection of propanil in fish and seawater samples

Molecularly imprinted quantum dots (MIP-QDs) were successfully synthesized via reversed-phase microemulsion and used as the specific recognition element and signal probe of a fluorescence sensor or test strip to achieve the highly sensitive detection of propanil. The physical-chemical characteristics and excellent selectivity of MIP-QDs were elucidated. Under optimized parameters, the MIP-QDs had good linearity at the propanil concentration range of 1.0 μg/L to 20.0 × 10³ μg/L by fluorescence quenching. The developed MIP-QD-based fluorescence sensor showed good recoveries ranging from 87.2 % to 112.2 %, and the relative standard deviation was below 6.0 % for the fish and seawater samples. In addition, the limits of detection (LODs) for fish and seawater were 0.42 μg/kg and 0.38 μg/L, respectively. The fluorescence test strip developed on the basis of the MIP-QDs also displayed satisfactory recoveries of 90.1 %-111.1 %, and the LOD for propanil in the seawater sample was 0.6 μg/L. The proposed fluorescence sensor and test strip were successfully used in propanil determination in environment and aquatic products.

Biodegradation of propanil by Acinetobacter baumannii DT in a biofilm-batch reactor and effects of butachlor on the degradation process

The herbicide, propanil, has been extensively applied in weed control, which causes serious environmental pollution. Acinetobacter baumannii DT isolated from soil has been used to determine the degradation rates of propanil and 3,4-dichloroaniline by freely suspended and biofilm cells. The results showed that the bacterial isolate could utilize both compounds as sole carbon and nitrogen sources. Edwards's model could be fitted well to the degradation kinetics of propanil, with the maximum degradation of 0.027 ± 0.003 mM h-1. The investigation of the degradation pathway showed that A. baumannii DT transformed propanil to 3,4-dichloroaniline before being completely degraded via the ortho-cleavage pathway. In addition, A. baumannii DT showed high tolerance to butachlor, a herbicide usually mixed with propanil to enhance weed control. The presence of propanil and butachlor in the liquid media increased the cell surface hydrophobicity and biofilm formation. Moreover, the biofilm reactor showed increased degradation rates of propanil and butachlor and high tolerance of bacteria to these chemicals. The obtained results showed that A. baumannii DT has a high potential in the degradation of propanil.

Characterization of an arylamidase from a newly isolated propanil-transforming strain of Ochrobactrum sp. PP-2

Propanil, one of the most extensively used post-emergent contact herbicides, has also been reported to have adverse effect on environmental safety. A bacterial strain of Ochrobactrum sp. PP-2, which was capable of transforming propanil, was isolated from a propanil-contaminated soil collected from a chemical factory. An arylamidase gene mah responsible for transforming propanil to 3,4-dichloroaniline (3,4-DCA) was cloned from strain PP-2 by shotgun method and subsequently confirmed by function expression. The arylamidase Mah shares low amino acid sequence identity (27-50%) with other biochemically characterized amidases and shows less than 30% identities to other reported propanil hydrolytic enzymes. Mah was most active at pH 8 and 35 °C. Mah had a remarkable activity toward propanil (K_m = 6.3 ± 1.2 µM), showing the highest affinity efficiency for propanil as compared with other reported propanil hydrolytic enzymes. Our study also provides a new arylamidase for the hydrolysis of propanil.

Metabolic Hydrolysis of Aromatic Amides in Selected Rat, Minipig, and Human In Vitro Systems

The release of aromatic amines from drugs and other xenobiotics resulting from the hydrolysis of metabolically labile amide bonds presents a safety risk through several mechanisms, including geno-, hepato- and nephrotoxicity. Whilst multiple in vitro systems used for studying metabolic stability display serine hydrolase activity, responsible for the hydrolysis of amide bonds, they vary in their efficiency and selectivity. Using a range of amide-containing probe compounds (0.5–10 µM), we have investigated the hydrolytic activity of several rat, minipig and human-derived in vitro systems - including Supersomes, microsomes, S9 fractions and hepatocytes - with respect to their previously observed human in vivo metabolism. In our hands, human carboxylesterase Supersomes and rat S9 fractions systems showed relatively poor prediction of human in vivo metabolism. Rat S9 fractions, which are commonly utilised in the Ames test to assess mutagenicity, may be limited in the detection of genotoxic metabolites from aromatic amides due to their poor concordance with human in vivo amide hydrolysis. In this study, human liver microsomes and minipig subcellular fractions provided more representative models of human in vivo hydrolytic metabolism of the aromatic amide compounds tested.

A bedside test for methemoglobinemia, Sri Lanka

Problem

Propanil is an aniline herbicide that is widely used for rice cultivation, but is also used for self-poisoning. Toxicity from propanil is largely due to methemoglobinemia. In resource-poor settings, the capacity to determine methemoglobin concentration is insufficient and prevents effective case management, which results in increased deaths from propanil poisoning.

Approach

Blood with a methemoglobin concentration greater than 15% of total haemoglobin levels appears brownish in colour. We introduced a colour reference chart that can be used to semiquantitatively determine methemoglobinemia. Each ward in three rural hospitals received a chart. Ward staff, medical officers and trainee doctors were given a presentation describing the test method and how it should be used with the relevant national treatment guidelines.

Local setting

In three rural hospitals in Sri Lanka, 401 patients were admitted with a diagnosis of propanil poisoning before the introduction of this test (2003–2007) and 262 patients after it was introduced (2008–2014), 46 of 663 patients died.

Relevant changes

The chart can be freely produced with any good-quality colour printer. In three rural hospitals, deaths from propanil poisoning fell from 10% of those admitted with this diagnosis in 2003–2007 (38/401) to 3% (8/262) in 2008–2014 and the use of methylene blue increased from 10% (13/136) to 55% (59/107) over this period.

Lessons learnt

This simple bedside test was associated with increased use of the first line treatment for propanil poisoning and improved survival. In 2011, the test was included in the national guidelines for the management of propanil poisoning.

Role of biomarkers of nephrotoxic acute kidney injury in deliberate poisoning and envenomation in less developed countries

Acute kidney injury (AKI) has diverse causes and is associated with increased mortality and morbidity. In less developed countries (LDC), nephrotoxic AKI (ToxAKI) is common and mainly due to deliberate ingestion of nephrotoxic pesticides, toxic plants or to snake envenomation. ToxAKI shares some pathophysiological pathways with the much more intensively studied ischaemic AKI, but in contrast to ischaemic AKI, most victims are young, previously healthy adults. Diagnosis of AKI is currently based on a rise in serum creatinine. However this may delay diagnosis because of the kinetics of creatinine. Baseline creatinine values are also rarely available in LDC. Novel renal injury biomarkers offer a way forward because they usually increase more rapidly in AKI and are normally regarded as absent or very low in concentration, thereby reducing the need for a baseline estimate. This should increase sensitivity and speed of diagnosis. Specificity should also be increased for urine biomarkers since many originate from the renal tubular epithelium. Earlier diagnosis of ToxAKI should allow earlier initiation of appropriate therapy. However, translation of novel biomarkers of ToxAKI into clinical practice requires better understanding of non-renal factors in poisoning that alter biomarkers and the influence of dose of nephrotoxin on biomarker performance. Further issues are establishing LDC population-based normal ranges and assessing sampling and analytical parameters for low resource settings. The potential role of renal biomarkers in exploring ToxAKI aetiologies for chronic kidney disease of unknown origin (CKDu) is a high research priority in LDC. Therefore, developing more sensitive biomarkers for early diagnosis of nephrotoxicity is a critical step to making progress against AKI and CKDu in the developing world.

P-chloroaniline poisoning causing methemoglobinemia: a case report and review of the literature

Background. Methemoglobin (MetHb) most commonly results from exposure to an oxidizing chemical but may also arise from genetic, dietary, or even idiopathic etiologies. P-chloroaniline (PCA) was one of the first substances described in the context of acquired methemoglobinemia. Case Report. We report the case of a cyanotic chemistry worker who presented to our emergency department (ED) after working with PCA. His peripheral oxygen saturation (SpO₂) measured by pulse oximetry was at 81% and remained on that level despite oxygen administration (100% oxygenation via nonrebreather mask). His MetHb level was measured at 42.8% in arterial blood gas analysis. After treatment with intravenous methylene blue cyanosis resolved and the patient was discharged after 36 hours of observation. Conclusion. Acquired methemoglobinemia is a treatable condition, which may cause significant morbidity and mortality. The knowledge about the most common causes, fast diagnostic, and proper treatment is crucial.

Exchange transfusion can be life-saving in severe propanil poisoning: a case report

BACKGROUND

Propanil is an important cause of herbicide poisoning in Sri Lanka, accounting for about 2% of all cases of self-poisoning. The outcome is extremely poor when the poisoning is severe and current medical care is of limited efficacy. Death usually occurs due to the severe and prolonged methaemoglobinaemia. We describe a case of severe Propanil poisoning, successfully treated by exchange transfusion at a tertiary care hospital in Sri Lanka.

CASE PRESENTATION

A 17-year old Sri Lankan male (body weight--42 kg), presented to a local hospital 1 hour after self-ingestion of nearly 500 ml (4.3 g/kg) of liquid Propanil (concentration--360 g/l). On admission he had dizziness and peripheral cyanosis. He was given intravenous methylene blue (1 mg/kg) within one hour of admission, which was repeated subsequently due to minimal response. The next day morning, (18 hours after poisoning) the patient was transferred to the National Hospital of Sri Lanka (NHSL) for further management. On admission to NHSL, he was drowsy and confused, had a shallow respiratory effort and marked central and peripheral cyanosis. Respiratory rate was 20/min, with a pulse-oximetry of 77% on room air. The arterial blood gas analysis was as follows; pH--7.24, HCO3(-)--12 mmol/l, pCO2--28 mmHg, pO2--239 mmHg and O2 saturation--100%. Exchange transfusion was commenced within two hours of admission to NHSL. A dramatic improvement in oxygen saturation was observed immediately afterwards, with the saturation in pulse-oximetry rising to >95%. The level of consciousness and respiratory effort also improved. He was discharged subsequently 8 days after the initial poisoning.

CONCLUSION

Propanil has potential to produce severe life threatening clinical manifestations, despite categorization as a herbicide with low toxicity. In cases of severe poisoning, exchange transfusion may be life saving. Since methylene blue, intensive care and exchange transfusion facilities are also not readily available in local hospitals, which frequently encounter cases of severe Propanil poisoning, early transfer of patients to tertiary care hospitals should be considered. Exchange transfusion may be helpful even in late stages in patients with severe poisoning.

Available extracorporeal treatments for poisoning: overview and limitations

Poisoning is a significant public health problem. In severe cases, extracorporeal treatments (ECTRs) may be required to prevent or reverse major toxicity. Available ECTRs include intermittent hemodialysis, sustained low-efficiency dialysis, intermittent hemofiltration and hemodiafiltration, continuous renal replacement therapy, hemoperfusion, therapeutic plasma exchange, exchange transfusion, peritoneal dialysis, albumin dialysis, cerebrospinal fluid exchange, and extracorporeal life support. The aim of this article was to provide an overview of the technical aspects, as well as the potential indications and limitations of the different ECTRs used for poisoned patients.

Applied clinical pharmacology and public health in rural Asia--preventing deaths from organophosphorus pesticide and yellow oleander poisoning

Self-poisoning with pesticides or plants is a major clinical problem in rural Asia, killing several hundred thousand people every year. Over the last 17 years, our clinical toxicology and pharmacology group has carried out clinical studies in the North Central Province of Sri Lanka to improve treatment and reduce deaths. Studies have looked at the effectiveness of anti-digoxin Fab in cardiac glycoside plant poisoning, multiple dose activated charcoal in all poisoning, and pralidoxime in moderate toxicity organophosphorus insecticide poisoning. More recently, using a Haddon matrix as a guide, we have started conducting public health and animal studies to find strategies that may work outside of the hospital. Based on the 2009 GSK Research in Clinical Pharmacology prize lecture, this review shows the evolution of the group's research from a clinical pharmacology approach to one that studies possible interventions at multiple levels, including the patient, the community and government legislation.

The toxicity of the N-hydroxy and 6-hydroxy metabolites of 3,4-dichloropropionanilide does not depend on calcium release-activated calcium channel inhibition

Each year ~1 billion kg of herbicides are used worldwide to control the unwanted growth of plants. In the United States, over a quarter of a billion kg of herbicides are used, representing 28% of worldwide use. (Kiely, T., Donaldson, D., and Grube, A. [2004]. Pesticide Industry Sales and Usage. 2000 and 2001 Market Estimates. Available at: http://www.epa.gov/pesticides/pestsales/01pestsales/market_estimates2001.pdf. Accessed October 25, 2012.) Propanil (3,4-dichloropropionanilide [DCPA]) is a commonly used herbicide in the United States, with 2-4 million kg applied annually to 2 million acres of crop land. The immunomodulatory effects of DCPA have been well documented, but limited data are available on the effects of its metabolites. (Salazar, K. D., Ustyugova, I. V., Brundage, K. M., Barnett, J. B., and Schafer, R. [2008]. A review of the immunotoxicity of the pesticide 3,4-dichloropropionanalide. J. Toxicol. Environ. Health B Crit. Rev. 11, 630-645.) In mammals, hepatic enzymes metabolize DCPA, resulting in the production of 3,4-dichloroaniline (DCA). Further biotransformation of DCA leads to the production of 6-hydroxy-3,4-dichloroaniline (6OH-DCA) and N-hydroxy-3,4-dichloroaniline (NOH-DCA). We report, for the first time, the immunotoxic effects of DCPA metabolites on T-cell function. Human Jurkat T cells were exposed to varying concentrations of DCPA or its metabolites and assayed for effects on T-cell function. In addition, fluorine analogs of DCPA and DCA were investigated to determine the relative role of chlorine substituents on T-cell immunotoxicity. Here we report that exposure of Jurkat T cells to DCPA and DCA alters IL-2 secretion, nuclear factor of activated T cells (NFAT) activity, and calcium influx. However, exposure to 6OH-DCA and NOH-DCA reduces IL-2 secretion and NFAT activity but has no effect on calcium flux. When both chlorines in DCPA and DCA were substituted with fluorines all effects were abrogated. Our data indicate that metabolites of DCPA have differential effects on T-cell function and the presence of chlorines plays an important role in eliciting these effects.

Acute human self-poisoning with bispyribac-containing herbicide Nominee: a prospective observational study

INTRODUCTION

Self-poisoning with herbicides is an important reason for hospital admission and death in Asia. Although some herbicides have a well-described toxicity profile in humans, many of the newer compounds rely on extrapolation from animal results as no published literature on clinical outcomes of human self-poisoning has been described. One example of these compounds is bispyribac, a selective herbicide used in rice and wheat cultivation that is marketed in two containers, one containing bispyribac 400 g/L with a solvent and the other the surfactant, polyethylene glycol. We present the first case series of acute human self-poisoning with an herbicide product containing bispyribac.

METHODS

Clinical data for all patients who presented with acute poisoning from a bispyribac-containing herbicide (Nominee) to two general hospitals in Sri Lanka from June 2002 to January 2009 were collected prospectively. Admission and serial blood samples were collected from consenting patients to confirm exposure and to study the toxicokinetics of bispyribac, respectively.

RESULTS

One hundred ten patients with a history of bispyribac ingestion presented after a median time of 4 h post-ingestion. There were three deaths at 15, 6, and 5 h post-ingestion because of asystolic cardiac arrest. All three patients had reduced Glasgow Coma Score (GCS) (3, 12, and 13, respectively) of whom the former two had co-ingested ethanol and developed tonic-clonic seizures. Admission blood sample was obtained from the former two of these patients but bispyribac was detected in only one of these patients. The other patient presented 2.5 h post-ingestion with a GCS of 12 but bispyribac was not detected. Excluding the patient with undetectable bispyribac, a conservative estimate of the case fatality ratio at 1.81% (95% confidence interval 0.32-5.8) can be made. The majority of the remaining patients had self-limiting upper gastrointestinal symptoms and eight patients had an abnormal GCS on presentation to hospital. The overall median hospital stay was 3 days. Bispyribac was not detectable on admission in 21 patients; in the remaining patients, the median plasma concentration was 50.55 microg/mL (interquartile range 1.28-116.5; n=32). The peak concentration was noted around 3 h post-ingestion and plasma bispyribac concentration did not predict the severity of poisoning.

CONCLUSION

The majority of patients developed self-resolving symptoms and were successfully managed in rural general hospitals without transfer to larger tertiary hospitals. Patients who died developed significant poisoning within 6 h and plasma bispyribac concentrations did not appear to predict mortality. The lack of correlation between bispyribac outcomes and the available plasma concentrations may be because of exposure to nonbispyribac components or other undefined factors. Clinical outcomes from acute self-poisoning with bispyribac-containing herbicides appear to be relatively more favorable than other commonly used herbicides.

A simple quantitative bedside test to determine methemoglobin

STUDY OBJECTIVE

Methemoglobinemia after pesticide poisoning is associated with a mortality of 12% in Sri Lanka. Treatment is complicated by the lack of laboratory facilities. We aimed to develop and validate a low-cost bedside test for quantitative estimation of clinically significant methemoglobin to be used in settings of limited resources.

METHODS

A method to reliably produce blood samples with 10% to 100% methemoglobin was developed. Freshly prepared methemoglobin samples were used to develop the color chart. One drop (10 microL) of prepared methemoglobin sample was placed on white absorbent paper and scanned using a flatbed Cannon Scan LiDE 25 scanner. The mean red, green, and blue values were measured with ImageJ 1.37v. These color values were used to prepare a color chart to be used at the bedside. Interobserver agreement was assessed against prepared samples. The results from clinical use were compared with formal methemoglobin measurements.

RESULTS

The red color value was linearly related to percentage methemoglobin (R(2)=0.9938), with no effect of absolute hemoglobin concentration. Mean interobserver (N=21) agreement and weighted kappa for scanned methemoglobin spots using the color chart were 94% and 0.83, respectively. Mean interobserver (N=9) agreement and weighted kappa for a freshly prepared methemoglobin sample with the chart were 88% and 0.71, respectively. Clinical use of the color chart also showed good agreement with spectrometric measurements.

CONCLUSION

A color chart can be used to give a clinically useful quantitative estimate of methemoglobinemia.

Acute intentional self-poisoning with a herbicide product containing fenoxaprop-P-ethyl, ethoxysulfuron, and isoxadifen ethyl: a prospective observational study

BACKGROUND

Herbicides are commonly ingested for self-harm, but relatively little has been published on poisoning with herbicides other than paraquat and glyphosate. We report here a case series of patients with acute exposure to a combination herbicide (brand name Tiller Gold or Whip Super) containing the selective phenoxy herbicide compounds fenoxaprop-P-ethyl and ethoxysulfuron and a safener isoxadifen ethyl.

METHOD

Clinical data on all patients presenting with Tiller Gold or Whip Super poisoning to two General Hospitals in Sri Lanka from 2002-2008 were collected prospectively until discharge.

RESULTS

Eighty-six patients with a history of Tiller Gold or Whip Super ingestion were included. The main clinical features were an epigastric burning sensation and vomiting; however, most of those who vomited had received gastric lavage or forced emesis. Eight patients had a reduced level of consciousness on admission (Glasgow coma scale 9-14) that resolved without intervention over several hours. Only symptomatic and supportive care was required. The median hospital stay was 1 day (IQR: 1-2) and the case fatality was zero (95% confidence interval: 0-4.2%). This low case fatality compared favorably with the case fatality of other common herbicides in our cohort: paraquat >40%, propanil >10%, 4-chloro-2-methylphenoxyacetic acid > 5%, and glyphosate >2%.

CONCLUSION

This combination herbicide product appears to be safe in patients with acute self-poisoning, particularly in comparison with other herbicides, and causing few clinical features.