Organophosphate-Induced Intermediate Syndrome

Clinical features of organophosphate poisoning: A review of different classification systems and approaches

PURPOSE

The typical toxidrome in organophosphate (OP) poisoning comprises of the Salivation, Lacrimation, Urination, Defecation, Gastric cramps, Emesis (SLUDGE) symptoms. However, several other manifestations are described. We review the spectrum of symptoms and signs in OP poisoning as well as the different approaches to clinical features in these patients.

MATERIALS AND METHODS

Articles were obtained by electronic search of PubMed(®) between 1966 and April 2014 using the search terms organophosphorus compounds or phosphoric acid esters AND poison or poisoning AND manifestations.

RESULTS

Of the 5026 articles on OP poisoning, 2584 articles pertained to human poisoning; 452 articles focusing on clinical manifestations in human OP poisoning were retrieved for detailed evaluation. In addition to the traditional approach of symptoms and signs of OP poisoning as peripheral (muscarinic, nicotinic) and central nervous system receptor stimulation, symptoms were alternatively approached using a time-based classification. In this, symptom onset was categorized as acute (within 24-h), delayed (24-h to 2-week) or late (beyond 2-week). Although most symptoms occur with minutes or hours following acute exposure, delayed onset symptoms occurring after a period of minimal or mild symptoms, may impact treatment and timing of the discharge following acute exposure. Symptoms and signs were also viewed as an organ specific as cardiovascular, respiratory or neurological manifestations. An organ specific approach enables focused management of individual organ dysfunction that may vary with different OP compounds.

CONCLUSIONS

Different approaches to the symptoms and signs in OP poisoning may better our understanding of the underlying mechanism that in turn may assist with the management of acutely poisoned patients.

Delayed onset neuropathy along with recurrent laryngeal nerve palsy due to organophosphate poisoning and the role of physiotherapy rehabilitation

Organophosphorus poisoning is a major global cause of health problems and the leading cause of mortality and morbidity in the developing countries. In this, the inhibition of acetyl-choline esterase and neurotoxic esterase along with nicotinic receptor involvement produces three well-identified and documented clinical phases: The initial cholinergic phase, which is a medical emergency often requiring management in an intensive care unit; the intermediate syndrome, during which prolonged ventilator care is necessary; and finally delayed neurotoxicity. Vocal cord paralysis is rare and leads to aphonia. Role of physiotherapy rehabilitation is substantial in all three stages and aims at early weaning off from mechanical ventilator until the functional independence and community integration of the patient.

Analysis of medical use of carbon adsorbents in China and additional possibilities in this field achieved in Ukraine

The review is devoted to analysis of the use of carbon sorbents for medicinal purposes in China and description of some innovative technologies in this field in Ukraine. The review underlines the presence of common roots of sorption therapy development in these two countries determined by pioneer works of Prof. T.M.S. Chang, created to the concept of artificial cells. High level of works of Chinese scientists on sorption purification of blood and combined extracorporeal methods has been mentioned. At the same time, by author's opinion, two other methods of sorption therapy, namely enterosorption and sorption therapy of wounds and burns, has not been properly developed in China. In the review, there are also described the essential results of Ukrainian scientists in the field of blood purification from protein-bound toxins and other harmful compounds what is important for treatment of many serious human pathologies, and also the important data on the use of oral sorbents and dressings from activated carbon materials, which could be considered as a useful addition to achievements of Chinese scientists in the field of the development and use of sorbents for medicinal purposes.

Incidence, predictors, and outcome of intermediate syndrome in cholinergic insecticide poisoning: a prospective observational cohort study

CONTEXT

Clinical manifestations and outcome of cholinergic insecticide poisoning is well studied. There are limited data on neuroparalytic features, predictors, and impact on mortality of intermediate syndrome.

METHODS

Patients admitted with history of insecticide exposure and cholinergic signs in a tertiary care center between April 2011 and March 2012 were followed up till recovery or death. While on standard care, development of intermediate syndrome was noted by neck and proximal muscle weakness, and/or signs of respiratory failure in the absence of cholinergic signs.

RESULTS

In 176 patients studied, incidence of intermediate syndrome was 17.6% (n = 31) with mean time of appearance of 44.5 ± 22.1 h after exposure (range 26 h- 5 days). Intermediate syndrome occurred in organophosphorus and carbamate poisoning (38.7% and 41.9%) and lasted for 1-7 days. All patients with intermediate syndrome developed weakness of neck and proximal muscles during the course; neck muscle weakness was the initial feature in majority of patients with respiratory failure (20/26). Age ≥ 45 (RR 2.23, 95% CI 1.14-4.38, p = 0.02), and dimethyl organophosphorus compounds (RR 4.87, 95% CI 1.82-13.04, p = 0.01) were found to be associated with development of intermediate syndrome while multiple gastric lavage was protective (RR 0.44, 95% CI 0.22-0.87, p = 0.001). Receiver operating characteristic curves were plotted for International Program on Chemical Safety Poison Severity Score (IPCS PSS) and Glasgow coma scale (GCS) on admission (AUC/sensitivity/specificity 0.77/0.94/0.6 for IPCS PSS > 2 and 0.64/0.71/0.65 for GCS ≤ 10). Overall mortality was 28.4% (n = 50); 40% (n = 20/50) occurred among intermediate syndrome patients with respiratory failure.

CONCLUSION

As with exposure to organophosphorus, carbamate also result in intermediate syndrome; risk may be high with age ≥ 45, admission score of PSS > 2, and GCS ≤ 10. It can be detected early by identifying neck muscle weakness which aids in anticipating respiratory failure. Multiple gastric lavages may be protective; needs larger studies for clarification.

Neurotranmission systems as targets for toxicants: a review

Neurotransmitters are chemicals that transmit impulses from one nerve to another or from nerves to effector organs. Numerous neurotransmitters have been described in mammals, amongst them acetylcholine, amino acids, amines, peptides and gases. Toxicants may interact with various parts of neurotransmission systems, including synthetic and degradative enzymes, presynaptic vesicles and the specialized receptors that characterize neurotransmission systems. Important toxicants acting on the cholinergic system include the anticholinesterases (organophosphates and carbamates) and substances that act on receptors such as nicotine and the neonicotinoid insecticides, including imidacloprid. An important substance acting on the glutamatergic system is domoic acid, responsible for amnesic shellfish poisoning. 4-Aminobutyric acid (GABA) and glycine are inhibitory neurotransmitters and their antagonists, fipronil (an insecticide) and strychnine respectively, are excitatory. Abnormalities of dopamine neurotransmission occur in Parkinson's disease, and a number of substances that interfere with this system produce Parkinsonian symptoms and clinical signs, including notably 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine, which is the precursor of 1-methyl-4-phenylpyridinium. Fewer substances are known that interfere with adrenergic, histaminergic or seroninergic neurotransmission, but there are some examples. Among peptide neurotransmission systems, agonists of opioids are the only well-known toxic compounds.

Mechanisms of muscular electrophysiological and mitochondrial dysfunction following exposure to malathion, an organophosphorus pesticide

Muscle dysfunction in acute organophosphorus (OP) poisoning is a cause of death in human. The present study was conducted to identify the mechanism of action of OP in terms of muscle mitochondrial dysfunction. Electromyography (EMG) was conducted on rats exposed to the acute oral dose of malathion (400 mg/kg) that could inhibit acetylcholinesterase activity up to 70%. The function of mitochondrial respiratory chain and the rate of production of reactive oxygen species (ROS) from intact mitochondria were measured. The bioenergetic pathways were studied by measurement of adenosine triphosphate (ATP), lactate, and glycogen. To identify mitochondrial-dependent apoptotic pathways, the messenger RNA (mRNA) expression of bax and bcl-2, protein expression of caspase-9, mitochondrial cytochrome c release, and DNA damage were measured. The EMG confirmed muscle weakness. The reduction in activity of mitochondrial complexes and muscular glycogen with an elevation of lactate was in association with impairment of cellular respiration. The reduction in mitochondrial proapoptotic stimuli is indicative of autophagic process inducing cytoprotective effects in the early stage of stress. Downregulation of apoptotic signaling may be due to reduction in ATP and ROS, and genotoxic potential of malathion. The maintenance of mitochondrial integrity by means of artificial electron donors and increasing exogenous ATP might prevent toxicity of OPs.

Alterations in gene expression in Caenorhabditis elegans associated with organophosphate pesticide intoxication and recovery

Background

The principal toxicity of acute organophosphate (OP) pesticide poisoning is the disruption of neurotransmission through inhibition of acetylcholinesterase (AChE). However, other mechanisms leading to persistent effects and neurodegeneration remain controversial and difficult to detect. Because Caenorhabditis elegans is relatively resistant to OP lethality—particularly through the inhibition of AChE—studies in this nematode provide an opportunity to observe alterations in global gene expression following OP exposure that cannot be readily observed in less resistant organisms.

Results

We exposed cultures of worms in axenic, defined medium to dichlorvos under three exposure protocols. In the first, worms were exposed continuously throughout the experiment. In the second and third, the worms were exposed for either 2 or 8 h, the dichlorvos was washed out of the culture, and the worms were allowed to recover. We then analyzed gene expression using whole genome microarrays from RNA obtained from worms sampled at multiple time points throughout the exposure. The worms showed a time-dependent increase in the expression of genes involved in stress responses. Early in the exposure, the predominant effect was on metabolic processes, while at later times, an immune-like response and cellular repair mechanisms dominated the expression pattern. Following removal of dichlorvos, the gene expression in the worms appeared to relatively rapidly return to steady-state levels.

Conclusion

The changes in gene expression observed in the worms following exposure to dichlorvos point towards two potential mechanisms of toxicity: inhibition of AChE and mitochondrial disruption.

Assessment of the severity of organophosphate (fenitrothion) poisoning based on its serum concentration and clinical parameters

BACKGROUND

Fenitrothion (MEP) is the most frequent cause of organophosphate pesticides (OP) poisoning in Japan, but clinical parameters to predict its severity remain uncertain.

METHOD

We evaluated 26 cases (12 males and 14 females) of MEP poisoning brought to our critical care center. Regarding acute lung injury (ALI) as a hallmark complication leading to poor recovery, we divided patients into two groups: cases without ALI (Grp1, n = 14), and cases who developed ALI (Grp2, n = 12) at various points after the poisoning. Serial changes in clinical parameters and laboratory test results were compared between them.

RESULTS

The median MEP concentrations on arrival (min~max) for Grp1 and Grp2 were 2.3 (0.5-5.1) and 4.6 (1.1-14.0) μg/ml, respectively. Serum pseudo-cholinesterase (PChE) levels on arrival were 21(< 10-59) U/L in Grp1 and < 10 in Grp2. Based on individual patient kinetics, we estimated MEP concentration at 2 and 24 hours after ingestion, and determined cutoff values for differentiating the two groups for each time point as 4.0 μg/ml and 0.5 μg/ml, respectively. By logistic regression analysis, two groups were distinguished with accuracy of 92.3% based on their time of arrival after ingestion and initial MEP concentration. Clinical parameters associated with ALI were days with miosis, days with PChE below 100 U/L, and days requiring administration of atropine.

CONCLUSION

The severity of MEP poisoning is closely associated with both time to presentation after ingestion and initial MEP concentration. Serial monitoring of MEP concentrations in the first 24 hours is also useful in predicting the clinical course.

Epidemiology of organophosphate pesticide poisoning in Taiwan

INTRODUCTION

The nationwide epidemiology of organophosphate pesticide (OP) poisoning has never been reported in detail for Taiwan.

METHODS

This study retrospectively reviewed all human OP exposures reported to Taiwan's Poison Control Centers (PCCs) from July 1985 through December 2006.

RESULTS

There were 4799 OP exposures. Most OP exposures were acute (98.37%) ingestions (74.50%) of a single OP (80.37%) to attempt suicide (64.72%) in adults (93.25%). Males were the most common gender (64.95%). Most patients (61.97%) received atropine and/or pralidoxime. The mortality rate for all 4799 OP exposures was 12.71%. Exposures to single OPs without co-intoxicants caused 524 deaths; of these, 63.36% were due to dimethyl OPs.

CONCLUSION

Dimethyl OPs cause the majority of deaths in Taiwan.

The spectrum of intermediate syndrome following acute organophosphate poisoning: a prospective cohort study from Sri Lanka

BACKGROUND

Intermediate syndrome (IMS) is a major cause of death from respiratory failure following acute organophosphate poisoning. The objective of this study was to determine repetitive nerve stimulation (RNS) predictors of IMS that would assist in patient management and clinical research.

METHODS AND FINDINGS

Seventy-eight consenting symptomatic patients with organophosphate poisoning were assessed prospectively with daily physical examination and RNS. RNS was done on the right and left median and ulnar nerves at 1, 3, 10, 15, 20, and 30 Hz. The study was conducted as a prospective observational cohort study in the Central Province, Sri Lanka. IMS was diagnosed in ten out of 78 patients using a priori clinical diagnostic criteria, and five of them developed respiratory failure. All ten patients showed progressive RNS changes correlating with the severity of IMS. A decrement-increment was observed at intermediate and high frequencies preceding the onset of clinical signs of IMS. As the patient developed clinical signs of IMS, decrement-increment was progressively noted at low and intermediate frequencies and a combination of decrement-increment and repetitive fade or severe decrement was noted at high frequencies. Severe decrement preceded respiratory failure in four patients. Thirty patients developed forme fruste IMS with less severe weakness not progressing to respiratory failure whose RNS was characterized by decrement-increment or a combination of decrement-increment and repetitive fade but never severe decrements.

CONCLUSIONS

Characteristic changes in RNS, preceding the development of IMS, help to identify a subgroup of patients at high risk of developing respiratory failure. The forme fruste IMS with the characteristic early changes on RNS indicates that IMS is a spectrum disorder. RNS changes are objective and precede the diagnosis and complications of IMS. Thus they may be useful in clinical management and research.

Noncholinesterase effects induced by organophosphate pesticides and their relationship to cognitive processes: implication for the action of acylpeptide hydrolase

Organophosphate pesticides have been classically described as inhibitors of acetylcholinesterase (AChE) activity in insects and invertebrates. However, there is now more evidence supporting the hypothesis that these compounds also act through noncholinergic pathways, especially those related to cognitive processes. The enzyme acylpeptide hydrolase was identified as a new target for organophosphate pesticides. This enzyme is more sensitive than AChE to some organophosphates (OP), including dichlorvos, which is the parent compound for metrifonate, a therapeutic agent used in the treatment of cognitive impairment associated to Alzheimer's disease. Therefore, there is some doubt as to whether the mechanism of action of this drug is mediated by a potentiation of cholinergic transmission. However, the direct action of acylpeptide hydrolase in cognitive processes and the physiological and molecular mechanisms underlying subacute exposure to OP have yet to be demonstrated. This review deals with evidence demonstrating the existence of mechanisms of actions of OP, which are independent of cholinergic pathway potentiation and which have an effect on cognitive processes. In addition, the possible participation of the enzyme acylpeptide hydrolase in these processes is also discussed. Finally, the possibility of using this enzyme activity as a new biomarker for exposure to OP is considered.

Michael Addition of Amine Derivatives to Conjugate Phosphinyl and Phosphonyl Nitrosoalkenes. Preparation of α-Amino Phosphine Oxide and Phosphonate Derivatives

The synthesis of nitrosoalkenes derived from phosphine oxides and phosphonates generated through base-mediated dehydrohalogenations of readily available alpha-halooximes is reported. These highly reactive intermediates act as Michael acceptors toward nucleophilic reagents such as ammonia, amines, and optically active amino esters, furnishing alpha-amino phosphine oxides and phosphonates in a highly regioselective fashion.

Intermediate Syndrome Following Acute Organophosphate Poisoning: Correlation with Initial Serum Levels of Muscle Enzymes

Following acute organophosphate poisoning, intermediate syndrome essentially relates to the impairment of neuromuscular transmission due to prolonged inhibition of acetylcholinesterase activity at the muscle end-plate. However, the role of muscle injury in the development of intermedicate syndrome is not clear. The aim of this study was to determine whether the initial serum levels of the muscle enzymes can predict the subsequent development of intermediate syndrome. We reviewed the files of 47 adult patients with organophosphate poisoning between April 2003 and February 2006. The muscle enzymes were obtained within first 24 hr from each patient. Among the patients, 17% (n = 8) had severe poisoning and 83% (n = 39) mild poisoning. In 10 patients (21%), intermediate syndrome was observed. Of the patients with severe poisoning, 63% (n = 5) developed subsequent intermediate syndrome; among those with mild poisoning, 13% (n = 5) developed intermediate syndrome. There was no significant difference in initial serum levels of creatine kinase and aspartate aminotransferase between the patients with severe poisoning and mild poisoning, and there was no difference in initial serum levels of creatine kinase and aspartate aminotransferase between the patients with and without intermediate syndrome. The serum levels of the muscle enzymes measured within the first 24 hr may not predict the subsequent development of intermediate syndrome.