Sarin poisoning in Matsumoto, Japan

State-wide hospital clinical laboratory plan for measuring cholinesterase activity for individuals suspected of exposure to nerve agent chemical weapons

BACKGROUND

Hospital laboratories currently lack the capacity to provide emergency determination of cholinesterase activity.

METHODS

We have developed a hospital-based 3-tiered system to test plasma for butyrylcholinesterase (BChE) activity and whole blood for red cell acetylcholinesterase (AChE) activity using available technology and personnel. Interagency communications, toxidrome definition, and patient triage will be coordinated by the Connecticut Department of Public Health and the Poison Control Center.

DATA

Initial BChE data documents good precision between institutions (coefficient of variation < 8%).

SUMMARY

Laboratory testing of plasma or blood for cholinesterase activity is important in the management of nerve agent exposure and in ruling out disease in those with non-specific symptoms in the setting of a terrorist attack or accidental exposure. Rapid availability of strong hospital-based analytic support in a smoothly functioning network of clinical, public health, and laboratory services will facilitate overall regional response to chemical terrorism or large scale HazMat events.

Glutamate receptor pathology is present in the hippocampus following repeated sub-lethal soman exposure in the absence of spatial memory deficits

Much is still unknown about the long-term effects of repeated, sub-lethal exposure to organophosphorus (OP) nerve agents, such as soman (GD), on learning and memory tasks and related protein expression in the hippocampus. In the present study, guinea pigs were exposed to sub-lethal doses of GD for 10 days and cognitive performance assessed using the Morris water maze (MWM) up to 88 days post-exposure to investigate spatial learning. Additionally, hippocampal lysates were probed for cytoskeletal, synaptic and glutamate receptor proteins using Western blot analyses. No significant difference in MWM performance was observed between repeated sub-lethal GD exposed and saline control groups. However, Western blot analyses revealed significant changes in glutamate receptor protein immunoreactivity for subunits GluR2, NMDAR1, NMDAR2a and NMDAR2b in the hippocampi of GD-exposed guinea pigs. Levels of GluR2, NMDAR2a and NMDAR2b increased by 3 months post-initial exposure and returned to control levels by 6 months while NMDAR1 decreased by 6 months. No significant differences in neurofilament medium (NFM), neurofilament light (NFL) or synaptophysin densitometry were detected and alpha-II-spectrin proteolytic breakdown was also absent. These results reveal that repeated, sub-lethal exposure to GD affects glutamate receptor subunit expression but does not affect cytoskeletal protein immunoreactivity or the proteolytic state in the hippocampus. Though these changes do not affect spatial memory, they may contribute to other cognitive deficits previously observed following sub-lethal OP exposure.

Bioterrorism: Processing Contaminated Evidence, the Effects of Formaldehyde Gas on the Recovery of Latent Fingermarks

In the present age of heightened emphasis on counter terrorism, law enforcement and forensic science are constantly evolving and adapting to the motivations and capabilities of terrorist groups and individuals. The use of biological agents on a population, such as anthrax spores, presents unique challenges to the forensic investigator, and the processing of contaminated evidence. In this research, a number of porous and non-porous items were contaminated with viable [corrected] spores and marked with latent fingermarks. The test samples were then subjected to a standard formulation of formaldehyde gas. Latent fingermarks were then recovered post decontamination using a range of methods. Standard fumigation, while effective at destroying viable spores, contributed to the degradation of amino acids leading to loss of ridge detail. A new protocol for formaldehyde gas decontamination was developed which allows for the destruction of viable spores and the successful recovery of latent marks, all within a rapid response time of less than 1 h.

Influence of air-purifying respirators on the simulated first response emergency treatment of CBRN victims

AIM

Medical first responders and emergency room personnel potentially are threatened by exposure to primary or secondary intoxication by chemical, biological, radiological or nuclear (CBRN) substances. The impact of personal respiratory protection by air-purifying respirators on the performance of resuscitation requires evaluation. This will help to improve major incident planning and measures for protecting medical staff.

METHODS

We investigated the influence of two air-purifying respirator designs on the resuscitation of simulated CBRN victims. Fourteen UK paramedics followed a standardised resuscitation algorithm, either unprotected or wearing a bi-ocular and a panoramic visor respirator in a randomised crossover design. Treatment times and wearer comfort was determined and compared.

RESULTS

We did not find any difference in treatment times between the groups wearing respiratory protection and the controls (189+/-8.3s for the controls, 191+/-9.5s for the panoramic visor mask and 206+/-9.1s for the bi-ocular respirator [mean+/-S.E.M.]). Tracheal intubation appeared to be the most time consuming task. In a questionnaire, volunteers were of the opinion that orientation whilst wearing the respirator with the panoramic visor was better compared to the bi-ocular one (85% versus 15%). With respect to the fit, the majority (79%) rated the bi-ocular respirator as more comfortable.

CONCLUSIONS

Modern personal respiratory protection has only a negligible effect in the delay on the short term treatment during well defined simulated scenarios with a single CBRN casualty. Furthermore, air-purifying respirators with panoramic visors seem to allow a better orientation for medical first responders during simulated resuscitation.

Nonconventional terror--the anesthesiologist's role in a nerve agent event

The structure and biologic action of nerve agents is similar to organophosphates, commonly used as insecticides. Acetylcholine accumulation and binding to the cholinergic receptor site stimulates the affected organs producing a predictable set of clinical symptoms. Treatment of the affected patients will include decontamination, respiratory and hemodynamic support, as well as specific antidotes. The multiple casualties that may be expected present additional logistical and organizational problems. The specific skills of anesthesiologists will make them invaluable members of the care team in such a chemical mass casualty event.

Guidelines for treating cardiac manifestations of organophosphates poisoning with special emphasis on long QT and Torsades De Pointes

Organophosphate poisoning may precipitate complex ventricular arrhythmias, a frequently overlooked and potentially lethal aspect of this condition. Acute effects consist of electrocardiographic ST-T segment changes and AV conduction disturbances of varying degrees, while long-lasting cardiac changes include QT prolongation, polymorphic tachycardia ("Torsades de Pointes"), and sudden cardiac death. Cardiac monitoring of organophosphate intoxicated patients for relatively long periods after the poisoning and early aggressive treatment of arrhythmias may be the clue to better survival. We present here a review of the literature with a focus on late cardiac arrhythmias (mainly "Torsades de pointes"), possible mechanisms, and treatment modalities, with special emphasis on postpoisoning monitoring for development of arrhythmias.

Unequal efficacy of pyridinium oximes in acute organophosphate poisoning

The use of organophosphorus pesticides results in toxicity risk to non-target organisms. Organophosphorus compounds share a common mode of action, exerting their toxic effects primarily via acetylcholinesterase (AChE) inhibition. Consequently, acetylcholine accumulates in the synaptic clefts of muscles and nerves, leading to overstimulation of cholinergic receptors. Acute cholinergic crisis immediately follows exposure to organophosphate and includes signs and symptoms resulting from hyperstimulation of central and peripheral muscarinic and nicotinic receptors. The current view of the treatment of organophosphate poisoning includes three strategies, i.e. the use of an anticholinergic drug (e.g., atropine), cholinesterase-reactivating agents (e.g., oximes) and anticonvulsant drugs (e.g., benzodiazepines). Oximes, as a part of antidotal therapy, ensure the recovery of phosphylated enzymes via a process denoted as reactivation of inhibited AChE. However, both experimental results and clinical findings have demonstrated that different oximes are not equally effective against poisonings caused by structurally different organophosphorus compounds. Therefore, antidotal characteristics of conventionally used oximes can be evaluated regarding how close the certain substance is to the theoretical concept of the universal oxime. Pralidoxime (PAM-2), trimedoxime (TMB-4), obidoxime (LüH-6), HI-6 and HLö-7 have all been demonstrated to be very effective in experimental poisonings with sarin and VX. TMB-4 and LüH-6 may reactivate tabun-inhibited AChE, whereas HI-6 possesses the ability to reactivate the soman-inhibited enzyme. An oxime HLö-7 seems to be an efficient reactivator of AChE inhibited by any of the four organophosphorus warfare agents. According to the available literature, the oximes LüH-6 and TMB-4, although relatively toxic, are the most potent to induce reactivation of AChE inhibited by the majority of organophosphorus pesticides. Since there are no reports of controlled clinical trials on the use of TMB-4 in human organophosphate pesticide poisoning, LüH-6 may be a better option.

Reactivation of organophosphate-inhibited human AChE by combinations of obidoxime and HI 6in vitro

Highly toxic organophosphorus-type (OP) chemical warfare agents (nerve agents) and OP pesticides may be used by terrorists and during military conflicts emphasizing the necessity for the development of effective medical countermeasures. The standard treatment with atropine and acetylcholinesterase (AChE) reactivators (oximes) is considered to be ineffective with certain nerve agents due to low oxime efficacy. Despite research over decades none of the oximes has turned out to be a broad spectrum reactivator to cover the whole range of potential threat agents. The prospective oxime HI 6 is a weak reactivator of tabun- and pesticide-inhibited AChE, while the established oxime obidoxime mainly lacks efficacy with cyclosarin-inhibited enzyme. In order to investigate the feasibility of combining obidoxime and HI 6, human AChE inhibited by sarin, cyclosarin, VX, tabun and paraoxon was reactivated by these oximes either alone or in combination. Two major findings of this study were that a combination of HI 6 and obidoxime did not impair reactivation, compared with HI 6 or obidoxime alone, but broadened the spectrum compared with the individual oximes. By using different oxime concentrations a combination of oxime doses may be suggested which could be an alternative to individual obidoxime or HI 6 autoinjectors.

The acute treatment of nerve agent exposure

Nerve agents (NA) are simple and cheap to produce but can produce casualties on a massive scale. They have already been employed by terrorist organizations and rogue states on civilians and armed forces alike. By inhibiting the enzyme acetylcholine esterase, NAs prevent the breakdown of the neurotransmitter acetylcholine. This results in over-stimulation of muscarinic and nicotinic receptors in the autonomic and central nervous systems and at the neuromuscular junction. Increased parasympathetic stimulation produces miosis, sialorrhea, bronchospasm and bronchorrhea. Effects at the neuromuscular junction cause weakness, fasciculations, and eventually paralysis. Central effects include altered behavior and mental status, loss of consciousness, seizures, or apnea. Most deaths are due to respiratory failure. Treatment with atropine competitively blocks the parasympathetic effects. Oximes like pralidoxime salvage acetylcholine esterase by "prying off" NA, provided the attachment has not "aged" to an irreversible bond. This reverses weakness. Benzodiazepines like diazepam are effective against NA induced seizures. Mortality has been surprisingly low. If victims can survive the first 15 to 20 min of a vapor attack, they will likely live. The low mortality rate to date underscores that attacks are survivable and research reveals even simple barriers such as clothing offer substantial protection. This article reviews the properties of NAs and how to recognize the clinical features of NA intoxication, employ the needed drugs properly, and screen out anxious patients who mistakenly believe they have been exposed.

Sarin experiences in Japan: acute toxicity and long-term effects

Two terrorist attacks with the nerve agent Sarin affected citizens in Matsumoto and Tokyo, Japan in 1994 and 1995, killing 19 and injuring more the 6000. Sarin, a very potent organophosphate nerve agent, inhibits acetylcholinesterase (AchE) activity within the central, peripheral, and autonomic nervous systems. Acute and long-term Sarin effects upon humans were well documented in these two events. Sarin gas inhalation caused instantaneous death by respiratory arrest in 4 victims in Matsumoto. In Tokyo, two died in station yards and another ten victims died in hospitals within a few hours to 3 months after poisoning. Six victims with serum ChE below 20% of the lowest normal were resuscitated from cardiopulmonary arrest (CPA) or coma with generalized convulsion. Five recovered completely and one remained in vegetative state due to anoxic brain damage. EEG abnormalities persisted for up to 5 years. Miosis and copious secretions from the respiratory and GI tracts (muscarinic effects) were common in severely to slightly affected victims. Weakness and twitches of muscles (nicotinic effects) appeared in severely affected victims. Neuropathy and ataxia were observed in small number (less than 10%) of victims, which findings disappeared between 3 days and 3 months. Leukocytosis and high serum CK levels were common. Hyperglycemia, ketonuria, low serum triglyceride, hypopotassemia were observed in severely affected victims, which abnormalities were attributed to damage of the adrenal medulla. Oximes, atropine sulphate, diazepam and ample intravenous infusion were effective treatments. Pralidoxime iodide IV reversed cholinesterase and symptoms quickly even if administered 6 h after exposure. Post Traumatic Stress Disorder (PTSD) was less than 8% after 5 years. However, psychological symptoms continue in victims of both incidents. In summary, both potent toxicity and quick recovery from critical ill conditions were prominent features. Conventional therapies proved effective in Sarin incidents in Japan.

Toxicological assessments of Gulf War veterans

Concerns about unexplained illnesses among veterans of the 1991 Gulf War appeared soon after that conflict ended. Many environmental causes have been suggested, including possible exposure to depleted uranium munitions, vaccines and other drugs used to protect troops, deliberate or accidental exposure to chemical warfare agents and pesticides and smoke from oil-well fires. To help resolve these issues, US and UK governments have sought independent expert scientific advice from prestigious, independent scientific and public health experts, including the US National Academies of Science and the UK Royal Society and Medical Research Council. Their authoritative and independent scientific and medical reviews shed light on a wide range of Gulf War environmental hazards. However, they have added little to our understanding of Gulf War veterans' illnesses, because identified health effects have been previously well characterized, primarily in the occupational health literature. This effort has not identified any new health effects or unique syndromes associated with the evaluated environmental hazards. Nor do their findings provide an explanation for significant amounts of illnesses among veterans of the 1991 Gulf War. Nevertheless, these independent and highly credible scientific reviews have proven to be an effective means for evaluating potential health effects from deployment-related environmental hazards.

Development and application of acute exposure guideline levels (AEGLs) for chemical warfare nerve and sulfur mustard agents

Acute exposure guideline levels (AEGLs) have been developed for the chemical warfare agents GB, GA, GD, GF, VX, and sulfur mustard. These AEGLs were approved by the National Advisory Committee for Acute Exposure Guideline Levels for Hazardous Substances after Federal Register publication and comment, and judged as scientifically valid by the National Research Council Committee on Toxicology Subcommittee on AEGLs. AEGLs represent general public exposure limits for durations ranging from 10 min to 8 h, and for three levels of severity (AEGL-1, AEGL-2, AEGL-3). Mild effects are possible at concentrations greater than AEGL-1, while life-threatening effects are expected at concentrations greater than AEGL-3. AEGLs can be applied to various civilian and national defense purposes, including evacuation and shelter-in-place protocols, reentry levels, protective clothing specifications, and analytical monitoring requirements. This report documents development and derivation of AEGL values for six key chemical warfare agents, and makes recommendations for their application to various potential exposure scenarios.

Prehospital management of sarin nerve gas terrorism in urban settings: 10 years of progress after the Tokyo subway sarin attack

Chemical agents have been used previously in wartime on numerous occasions, from World War I to the Gulf War. In 1994 and 1995, sarin nerve gas was used first in peacetime as a weapon of terrorism in Japan. The Tokyo subway sarin attack was the first large-scale disaster caused by nerve gas. A religious cult released sarin gas into subway commuter trains during morning rush hour. Twelve passengers died and about 5500 people were harmed. Sarin is a highly toxic nerve agent that can be fatal within minutes to hours. It causes the clinical syndrome of cholinergic hyperstimulation by inhibition of the crucial enzyme acetylcholinesterase. Therapy of nerve agent toxicity is divided into three categories, decontamination, respiratory support, and antidotes. All of these therapies may be given simultaneously. This article reviews toxicology and management of this acute chemical emergency. To help minimize the possible catastrophic impact on the public, we make several recommendations based on analysis of the Tokyo subway sarin attack and systematically review the current scientific literature.

Introduction--What critical care practitioners should know about terrorism agents

Terrorist attack by chemical, biologic, or radiologic agents is a prime concern of emergency planners, and would likely lead to casualties that require critical care. This article reviews the past military and terrorist uses of these agents and reviews the most likely agents to be used by terrorists against civilian populations.

Effects of sarin on the nervous system of subway workers seven years after the Tokyo subway sarin attack

This study was designed to assess the after effects of sarin exposure on the nervous system in victims of the Tokyo Subway Sarin Attack, which occurred on 20 March, 1995. We performed a similar study 3 yr after the disaster. This time, we newly enrolled 36 staff of the Teito Rapid Transit Authority (Tokyo Eidan subway) to assess the 7 yr after effects on the nervous system, and merged previous data including unpublished data to enhance statistical power. New subjects consisted of 23 male exposed subjects and 13 referent subjects matched for age and working types. Neurobehavioral tests for psychomotor function and memory, stabilometry, and Benton visual retention test were performed. As reported previously, the exposed group performed significantly less well in the psychomotor function test (tapping) than the referent group (117.8 +/- 1.2 vs. 105.6 +/- 1.2 msec). Using merged data, this phenomenon was also observed in a dose-dependent manner and the exposed group performed significantly less well in the backward digit span test (4.47 +/- 1.17 vs. 5.11 +/- 1.65 digits). These results indicate that chronic decline of psychomotor function and memory function still exist 7 yr after the sarin exposure.

OP or not OP: the medical challenge at the chemical terrorism scene

Since the 1995 Tokyo subway sarin attack, terrorist attacks involving weapons of mass destruction or other industrial chemicals present worldwide security and health concerns. On-scene medical triage and treatment in such events is crucial to save as many lives as possible and minimize the deleterious effects of the toxic agent involved. Since there are many chemicals that can be used as potential terrorist weapons, the medical challenge for the emergency medical services (EMS) is a combination of: (1) recognizing that a chemical terrorist attack (non-conventional) has occurred; and (2) identifying the toxic agent followed by proper antidotal treatment. The latter must be done as quickly as possible, preferably on-scene. The most valuable decision at this stage should be whether the agent is organophosphate (OP) or not OP, based on clinical findings observed by pre-trained, first responders. This decision is crucial, since only OP intoxication has readily available, rapidly acting, onscene, specific agents such as atropine and one of the oximes, preferably administered using autoinjectors. Due to the lack of a specific antidote, exposure to other agents (such as industrial chemicals, e.g., chlorine, bromide, or ammonia) should be treated on-scene symptomatically with non-specific measures, such as decontamination and supportive treatment. This paper proposes an algorithm as a cognitive framework for the medical teams on-scene. This algorithm should be part of the medical team's training for preparedness for chemical terrorist attacks, and the team should be trained to use it in drills. Implementing this path of thinking should improve the medical outcome of such an event.

Organic Phosphorus Compounds—Nerve Agents

The organic phosphorous compounds (OPC) include both the military grade nerve agents and the organic phosphorous pesticides. The major mechanism of OPC toxicity is through inhibition of acetylcholinesterase in neuronal synapses leading to excess acetylcholine and overstimulation of target organs. Signs and symptoms depend on the affinity of the OPC for muscarinic versus nicotinic receptors, and are likely to include both. Muscarinic symptoms may include diarrhea, urination, bronchospasm, bronchorrhea, emesis, and salivation. Nicotinic symptoms such as paralysis and fasciculations may also occur. Central nervous system toxicity may include seizures, altered mental status, and apnea, and require prompt intervention. Treatment includes early airway and ventilatory support as well as antidotal therapy with atropine, pralidoxime, and diazepam. Goals of therapy include prevention and rapid treatment of hypoxia and seizures, as these are linked to patient outcome.

Biphasic extrathoracic cuirass ventilation for resuscitation

PURPOSES

The MRTX portable lightweight respirator (MRTX) provides noninvasive respiratory support using biphasic extrathoracic ventilation via a cuirass fitted around the patient's chest.

METHODS

MRTX was applied with or without full protective gear, on adult volunteers simulating nerve agent (NA) victims by nonmedical caregivers. Assessment was made based on scores for correct positioning of the cuirass, quality of seal, and rapidness.

RESULTS

For the unprotected and protected personnel, the respective median (+/-95% confidence interval) scores for correct positioning of the cuirass were 2 (1.4-1.9) and 1 (1.2-1.8) (n = 15 per group, P = NS); quality of seal scores were 2 (1.5-2.0) and 2 (1.3-1.8) ( P = NS); and mean (+/-SD) time required for instituting mechanical ventilation was 90.5 +/- 10.9 and 100.3 +/- 7.9 seconds ( P < .05). The respirator was activated at first attempt 11 times in the group of 15 without protective gear and 8 times in the group of 15 with protective gear ( P = NS).

DISCUSSION

Biphasic cuirass ventilation is an easily learned and rapidly applied method suitable for use by nonmedical personnel, even when wearing cumbersome protective gear.

Effective bisquaternary reactivators of tabun-inhibited AChE

Two cholinesterase reactivators (K074 and K075) were synthesized and their reactivation efficacy against tabun-inhibited acetylcholinesterase of the rat brain was tested in vitro. Comparing this efficacy showed that commonly used oximes (pralidoxim, obidoxime and HI-6) were practically without reactivation potency. On the other hand, oximes K074, K075 and trimedoxime were satisfactorily effective. Moreover, K-oximes reactivated tabun-inhibited AChE at lower concentration (10(-4) and 10(-3) m) in comparison with trimedoxime (10(-3) and 10(-2) m). Thus, K-oximes can be considered as the most effective reactivators of tabun-inhibited AChE at present.

Resolving Disputes About Toxicological Risks During Military Conflict

In the last 15 years, the US and UK have fought two major wars in the Persian Gulf region. Controversy has arisen over the nature and causes of health problems among military veterans of these two wars. Toxic exposures have been hypothesised to cause the majority of the long-term health problems experienced by veterans of the 1991 Gulf War. The assessment of these toxic exposures and the resolution of controversy about their health effects provide a unique case study for understanding how toxicological disputes are settled in the US. Neither clinical examination of ill war veterans nor scientific research studies have been sufficient to answer contentious questions about toxic exposures. Numerous expert review panels have also been unable to resolve these controversies except for the US National Academy of Sciences Institute of Medicine (IOM). The IOM has conducted exhaustive and independent investigations based on peer-reviewed scientific literature related to potential health risks during the two Gulf Wars. In four recent studies, IOM committees identified a wide range of previously documented illnesses associated with common occupational and environmental exposures after considering thousands of relevant publications; however, they did not identify a new medical syndrome or a specific toxic exposure that caused widespread health problems among Gulf War veterans. These IOM studies have, therefore, added little to our basic knowledge of environmental hazards because most of the health effects were well known. Nevertheless, this expert review process, which is on-going, has been generally acceptable to a wide range of competing interests because the findings of the IOM have been perceived as scientifically credible and independent, and because none of the postulated toxicological risks have been completely ruled-out as possible causes of ill health among veterans.

Organophosphates/nerve agent poisoning: mechanism of action, diagnosis, prophylaxis, and treatment

OP/nerve agents are still considered as important chemicals acting on living organisms and are widely used. They are characterized according to their action as compounds influencing cholinergic nerve transmission via inhibition of AChE. Modeling of this action and extrapolation of experimental data from animals to humans is more possible for highly toxic agents than for the OP. The symptoms of intoxication comprise nicotinic, muscarinic, and central symptoms; for some OP/nerve agents, a delayed neurotoxicity is observed. Cholinesterases (AChE and BuChE) are characterized as the main enzymes involved in the toxic effect of these compounds, including molecular forms. The activity of both enzymes (and molecular forms) is influenced by inhibitors (reversible, irreversible, and allosteric) and other factors, such as pathological states. There are different methods for cholinesterase determination; however, the most frequent is the method based on the hydrolysis of thiocholine esters and subsequent detection of free SH-group of the released thiocholine. The diagnosis of OP/nerve agent poisoning is based on anamnesis, the clinical status of the intoxicated organism, and on cholinesterase determination in the blood. For nerve agent intoxication, AChE in the red blood cell is more diagnostically important than BuChE activity in the plasma. This enzyme is a good diagnostic marker for intoxication with OP pesticides. Some other biochemical examinations are recommended, especially arterial blood gas, blood pH, minerals, and some other specialized parameters usually not available in all clinical laboratories. These special examinations are important for prognosis of the intoxication, for effective treatment, and for retrospective analysis of the agent used for exposure. Some principles of prophylaxis against OP/nerve agent poisoning comprising the administration of reversible cholinesterase inhibitors such as pyridostigmine (alone or in combination with other drugs), scavengers such as preparations of cholinesterases, some therapeutic drugs, and possible combinations are given. Basic principles of the treatment of nerve agent OP poisoning are described. They are based on the administration of anticholinergics (mostly atropine but some other anticholinergics can be recommended) as a symptomatic treatment, cholinesterase reactivators as a causal treatment (different types but without a universal reactivator against all OP/nerve agents) as the first aid and medical treatment, and anticonvulsants, preferably diazepam though some other effective benzodiazepines are available. New drugs for the treatment are under experimental study based on new approaches to the mechanism of action. Future trends in the complex research of these compounds, which is important not only for the treatment of intoxication but also for the quantitative and qualitative increase of our knowledge of toxicology, neurochemistry, neuropharmacology, clinical biochemistry, and analytical chemistry in general, are characterized.

Cholinergic symptoms due to nerve agent attack: a strategy for management

This article provides a brief history of nerve agent development and use and discusses the pharmacology, symptoms, signs, and treatment of nerve agent exposure. In addition, this article discusses the challenges of mass-casualty triage, decontamination, resuscitation, and intensive care.

Organophosphorus ester-induced chronic neurotoxicity

Organophosphorus compounds are potent neurotoxic chemicals that are widely used in medicine, industry, and agriculture. The neurotoxicity of these chemicals has been documented in accidental human poisoning, epidemiological studies, and animal models. Organophosphorus compounds have 3 distinct neurotoxic actions. The primary action is the irreversible inhibition of acetylcholinesterase, resulting in the accumulation of acetylcholine and subsequent overstimulation of the nicotinic and muscarinic acetylcholine receptors, resulting in cholinergic effects. Another action of some of these compounds, arising from single or repeated exposure, is a delayed onset of ataxia, accompanied by a Wallerian-type degeneration of the axon and myelin in the most distal portion of the longest tracts in both the central and peripheral nervous systems, and is known as organophosphorus ester-induced delayed neurotoxicity (OPIDN). In addition, since the introduction and extensive use of synthetic organophosphorus compounds in agriculture and industry half a century ago, many studies have reported long-term, persistent, chronic neurotoxicity symptoms in individuals as a result of acute exposure to high doses that cause acute cholinergic toxicity, or from long-term, low-level, subclinical doses of these chemicals. The author attempts to define the neuronal disorder that results from organophosphorus ester-induced chronic neurotoxicity (OPICN), which leads to long-term neurological and neurobehavioral deficits. Although the mechanisms of this neurodegenerative disorder have yet to be established, the sparse available data suggest that large toxic doses of organophosphorus compounds cause acute necrotic neuronal cell death in the brain, whereas sublethal or subclinical doses produce apoptotic neuronal cell death and involve oxidative stress.

Biochemical changes in mouse lung after subcutaneous injection of the sulfur mustard 2-chloroethyl 4-chlorobutyl sulfide

Sulfur mustard (HD) is a vesicant-type chemical warfare agent (CWA) introduced in World War I which continues to be produced, stockpiled, and occasionally deployed by some countries, and could be used potentially by terrorists. Exposure to HD can cause erythema, blisters, corneal opacity, and airway damage. We have reported previously that subcutaneous (SC) injection of immunodeficient athymic nude mice with the half mustard butyl 2-chloroethyl sulfide (BCS) causes systemic biochemical changes in several organs distal to the exposure site. In the present study, we examined the response of non-immunodeficient Swiss Webster mice to the mustard, 2-chloroethyl 4-chlorobutyl sulfide (CECBS). In a pilot study, we found that a single SC injection of 20-25 microl/mouse causes death within 24h. Consequently, we used 5 microl/mouse (approx. 0.017 mg/kg body weight) of neat CECBS or an equal volume of saline as control. We examined the lungs after 1, 24, and 48 h for biochemical changes including total and oxidized glutathione, protein, DNA, and lipid peroxidation contents in tissue homogenate, and superoxide dismutase, catalase, glucose-6-phosphate dehydrogenase, and glutathione S-transferases activities in the cytosol. After 1h and/or 24h, we found statistically significant changes that were resolved by 48 h. These changes mimicked those of HD and BCS and were generally consistent with free radical-mediated oxidative stress. The implications of these observations are two-fold. First, dermal exposure to low-dose mustard gas could elicit systemic changes impacting distal organs such as the lungs. It also suggests that antioxidants could potentially modulate the response and reduce the damage. Second, although the use of known CWAs such as HD is prohibited, analogs that are not recognized as agents are as toxic and could be dangerous if acquired and used by potential terrorists.

Future considerations for the medical management of nerve-agent intoxication

The use of chemical warfare agents against civilians and unprotected troops in international conflicts or by terrorists against civilians is considered to be a real threat, particularly following the terrorist attacks on 11 September 2001 against the World Trade Center in New York and against the Pentagon in Washington, DC. Over the past 10 years, terrorists have been planning to use or have used chemical warfare agents on several occasions around the world, and the attacks in 2001 illustrate their willingness to use any means of warfare to cause death and destruction among civilians. In spite of new international treaties with strong verification measures and with an aim to prohibit and prevent the use of weapons of mass destruction, nevertheless, some countries and terrorist groups have been able to develop, produce, and use such weapons, particularly nerve agents, in domestic terrorist attacks or during warfare in international conflicts. This article reviews current medical therapy for nerve-agent intoxication and discusses possible future improvement of medical therapies. Present medical counter-measures against nerve agents are not sufficiently effective particularly in protecting the brain. Therefore, new and more effective countermeasures must be developed to enable better medical treatment of civilians and military personnel following exposure to nerve agents. Therefore, it is important with an enhanced effort by all countries, to improve and increase research in medical countermeasures, in the development of protective equipment, and in carrying out regular training of medical and emergency personnel as well as of military nuclear, biological, or chemical (NBC) units. Only then will nations be able to reduce the risk from and prevent the use of such weapons of mass destruction (WMD).

Future applications of phosphotriesterases in the prophylaxis and treatment of organophosporus insecticide and nerve agent poisonings

Organophosphorus compounds (OPs) are being used as insecticides and warfare agents. OP insecticides represent an important problem of public health, causing around 200,000 deaths annually. The World Health Organization has pointed to the necessity to introduce new medical practices that improve the results of classical treatments. Many studies have shown that the administration of phosphotriesterases (enzymes that detoxify OPs through hydrolysis) is a promising treatment of persons poisoned with OPs. Such an enzyme-based treatment might introduce important improvements in the treatment of patients having ingested large amounts of OPs. Phosphotriesterases might also be suitable for prophylactic treatment of persons at risk to be severely exposed. The new experimental treatments do not exhibit the intrinsic neurotoxicity of the classical prophylaxis based on carbamates and antimuscarinic drugs. Experimental data suggest that might be time to initiate clinical trials in order to study the efficacy of phosphotriesterases in the therapy and prophylaxis of OP intoxication.

Nerve agents: a comprehensive review

Nerve agents are perhaps the most feared of potential agents of chemical attack. The authors review the history, physical characteristics, pharmacology, clinical effects, and treatment of these agents.

Laryngeal mask airway control versus endotracheal intubation by medical personnel wearing protective gear

The purpose of this study was to evaluate the rates of successful airway control using endotracheal tubes (ETs) or laryngeal mask airways (LMAs) and compare them between anesthetists and non-anesthetists wearing full antichemical protective gear. Anesthetists and non-anesthetists (n = 10 per group) twice attempted inserting ETs and LMAs on a mannequin model of airway management in a crossover, prospective manner. Times to successful insertion and failure rates were recorded. Non-anesthetists had a slightly higher failure rate inserting ETs compared with anesthetists (P = not significant). Respective mean times to successfully inserting ETs were 38 +/- 7.1 and 26.4 +/- 7.5 seconds (P < .05). Both groups inserted LMAs more rapidly than ETs (P < .05) and their failure rates in ET use were higher. In view of the relative rapidity by which LMAs were inserted as compared with ETs, by fully protected caregivers, the incorporation of LMA in algorithms dealing with emergency airway management in a nonconventional mass casualty scenario deserves further evaluation.

Application of a cuirass and institution of biphasic extra-thoracic ventilation by gear-protected physicians

OBJECTIVES

To evaluate the speed by which cuirass application, followed by biphasic extra-thoracic ventilation, can be instituted by full anti-chemical protective gear-wearing physicians.

MATERIALS AND METHODS

Ten physicians of variable subspecialties applied a cuirass on an adult volunteer and instituted biphasic extra-thoracic ventilation, using the RTX respirator (Medivent, London, UK). Endotracheal (ET) intubation and manual ventilation of a mannequin and its ventilation was comparatively assessed. Performances were conducted in a prospective, crossover, randomized manner. Times to successful applications as well as failure rates were recorded.

RESULTS

Cuirass application was performed more rapidly (102 +/- 9 s, 177 +/- 31 s, respectively, P <.01) and with a slightly lower failure rate than ET intubation.

CONCLUSIONS

Physicians wearing full anti-chemical protective gear applied the cuirass and instituted biphasic extra-thoracic ventilation faster than ET intubation and manual positive pressure ventilation. Extra-thoracic ventilation should be further evaluated as an option for emergent respiratory support during toxic mass casualty events.

Secondary contamination in organophosphate poisoning: analysis of an incident

BACKGROUND

Acute organophosphate poisoning is rare in the UK, and the risks to attending staff are seldom appreciated.

STUDY DESIGN

Report of an incident.

RESULTS

In May 2001, a 45-year-old man attempted suicide by drinking organophosphate insecticide, and was brought to an urban general hospital in a collapsed state. Twenty-five hospital workers and paramedics sought medical advice after coming into contact with the poisoned patient, of whom ten complained of symptoms related to toxin exposure. Provision of emergency services by the hospital was compromised, and the emergency department was closed until the area was decontaminated and staffing levels could be restored.

DISCUSSION

Ingestion of OP compounds can present a significant risk to health professionals as well as patients. Problems with the management of this patient included late recognition of the need for decontamination, large numbers of non-essential staff coming into contact with the patient, and the difficulty of carrying out medical procedures while wearing protective equipment. Decontamination should always be considered early, and the possibility of an ingested poison being vomited and causing a chemical spill should not be overlooked.

Resuscitative challenges in nerve agent poisoning

The threat of weapons of mass destruction such as nerve agents has become real since last year. The medical community has established protocols for the rapid evacuation and decontamination of affected civilians. However, protocols for resuscitative measures or acute perioperative care in cases of life-saving surgical interventions in toxic-traumatized casualties are still lacking. The database concerning the effects of nerve agent poisoning in humans is limited, and is largely based on reports of unintentional exposures to pesticide organophosphate poisoning and similar chemical substances. In this review, we summarize the knowledge on the possible pharmacological interactions between nerve agents and acute care.

Nerve agent attacks on children: diagnosis and management

Nerve agents (NAs) are the most lethal chemical weapons. We review the pathophysiology and management of NA poisoning of children. NAs cause cholinergic crisis. Children may manifest signs of cholinergic poisoning differently than adults. Children may be less likely to manifest miosis and glandular secretions. They may present with neurologic derangements alone. The goals of treatment should be to limit additional exposure, to provide respiratory support, and to prevent neurologic morbidity. Autoinjectors are optimal delivery vehicles for intramuscular antidotes and are likely to be used in civilian prehospital care. Antidotes include anticholinergics, oximes, and benzodiazepines. Several medications may be available within each class of antidotes. Clinicians will select an antidote based on the status of the individual victim, the accessibility of supportive care, and the availability of the drug. Atropine is well-tolerated and high doses may be required. The oxime pralidoxime chloride has a longer half-life in children. Currently, diazepam is the standard NA anticonvulsant. Midazolam may be the most effective intramuscular anticonvulsant after NA exposure, but, despite its efficacy, it is not an approved agent for seizures. Supportive care and long-term complications are summarized.

Comparative efficacy of diazepam and avizafone against sarin-induced neuropathology and respiratory failure in guinea pigs: influence of atropine dose

This investigation compared the efficacy of diazepam and the water-soluble prodiazepam-avizafone-in sarin poisoning therapy. Guinea pigs, pretreated with pyridostigmine 0.1 mg/kg, were intoxicated with 4LD(50) of sarin (s.c. route) and 1 min after intoxication treated by intramuscular injection of atropine (3 or 33.8 mg/kg), pralidoxime (32 mg/kg) and either diazepam (2 mg/kg) or avizafone (3.5 mg/kg). EEG and pneumo-physiological parameters were simultaneously recorded. When atropine was administered at a dose of 3 mg/kg, seizures were observed in 87.5% of the cases; if an anticonvulsant was added (diazepam (2 mg/kg) or avizafone (3.5 mg/kg)), seizure was prevented but respiratory disorders were observed. At 33.8 mg/kg, atropine markedly increased the seizure threshold and prevented early respiratory distress induced by sarin. When diazepam was administered together with atropine, seizures were not observed but 62.5% of the animals displayed respiratory difficulties. These symptoms were not observed when using avizafone. The pharmacokinetic data showed marked variation of the plasma levels of atropine and diazepam in different antidote combination groups, where groups receiving diazepam exhibited the lowest concentration of atropine in plasma. Taken together, the results indicate that avizafone is suitable in therapy against sarin when an anticonvulsant is judged necessary.

Pulmonary manifestations of intentionally released chemical and biological agents

Recent events have underscored the importance of knowledge and understanding of biological and chemical agents that are intentionally released on civilian populations. Preparedness of the medical community to recognize and manage the resulting clinical syndromes will be a major determinant in the outcome of such attack, or a community's 'prognosis' for survival. The biological and chemical agents that have been weaponized produce diseases and toxidromes that are not commonly seen by clinicians in most parts of the United States. Patients or clusters of patients who present with febrile syndromes that are unusual for the geographic or seasonal setting should trigger notification of public health authorities and the use of state or national reference lab systems for augmented diagnostic support. In many cases, early, empiric therapy, administered before definitive diagnosis, is required for survival. The basic principles in the management of exposure to chemical agents include containment, prevention of secondary exposure, rapid decontamination, implementation of supportive and symptomatic care, and specific antidotes as indicated and available.

A review of nerve agent exposure for the critical care physician

Nerve agents are discussed. The article discusses their properties, routes of exposure, toxicodynamics, targets of toxicity, and treatment. It is concluded that a focused organized approach to the treatment of nerve agents is key to its successful management.

Clinical features on nerve gas terrorism in Matsumoto

Clinical features on the first unexpected nerve gas terrorism using sarin (isopropyl methylphosphonofluoridate) on citizens in the city of Matsumoto is described. The nerve gas terrorism occurred at midnight on 27 June, 1994. About 600 people including residents and rescue staff were exposed to sarin gas. Fifty-eight victims were admitted to hospitals and seven died. Theoretically, sarin inhibits systemic acetylcholinesterase and damages all the autonomic transmission at the muscarinic and nicotinic acetylcholine receptor. Miosis was the most common finding in the affected people. In cases with severe poisoning, organophosphate may affect the central nervous system and cause cardiomyopathy. A few of the victims complained of arrhythmia and showed a decreased cardiac contraction. Abnormal electroencephalograms were recorded in two patients. The clinical features and follow-up studies are discussed with reference to the Tokyo subway terrorism and related articles.

Toxicology update: the cardiotoxicity of the oxidative stress metabolites of catecholamines (aminochromes)

This toxicology update reviews the oxidative stress metabolites of catecholamines, postulated to be the biochemical initiators of cardiotoxicity. A brief overview of catecholamine metabolism is provided with several noteworthy historical observations relating to the autoxidation and rearrangement of epinephrine. The basic chemical and physical properties of adrenochrome and adrenolutin are discussed. The autoxidative, enzymatic and cellular basis for the transformation of catecholamines to oxidative metabolites is reviewed. Mechanisms seeking to account for the observed cardiotoxic changes in isolated heart perfusion studies and in vivo models are described.

Perioperative care of children with nerve agent intoxication

Nerve agents (NA) present a major threat to civilian populations. When a ballistic system is used for spreading poison, multiple trauma, as well as toxic trauma could be caused. Children are more susceptible, due to their smaller physiological reserve. Urgent surgical intervention for combined intoxication in the multiple-traumatized child could be a tremendous task in view of the background of physiological instability. Nerve agents affect the autonomic, as well as the central nervous system, leading occasionally to unexpected interactions with agents normally used for resuscitation. This can cause additional instability, and possibly systemic collapse. This review presents and emphasizes points concerning treatment of a child who suffers from combined multiple and toxic traumas. The review is based on scant knowledge of a database of similar cases of pesticide organophosphate poisoning in children since these compounds are alike. We also extrapolated data from reports concerning episodic civilian exposure to NA.

Anaesthesia and critical care considerations in nerve agent warfare trauma casualties

Nerve agents (NA) (tabun, sarin, suman, VX) have been stocked around the world for some time and still present a major threat to civilian as well as to military populations. Since NA can be delivered through both an aerial spray system and a ballistic system, victims could suffer both NA intoxication and multiple trauma necessitating urgent surgical intervention followed by intensive care. These patients can be expected to be extremely precarious neurologically, respiratorily and haemodynamically. Moreover, their clinical signs can be misleading. Further exacerbating the problem is the fact that interactions of NA with the pharmacological agents used for resuscitation and/or during anaesthesia can aggravate organ instability even more and possibly cause systemic collapse. There are no protocols for perioperative critical care and early assessment or for the administration of anaesthesia for surgical interventions in such combined multiple trauma and intoxicated casualties. We propose a scheme for the administration of critical care and anaesthesia based on the scant anecdotal reports that have emerged after the occurrence of local accidents involving NA intoxication and on the neuropharmacological knowledge of the pesticide organophosphate poisoning database, these compounds being related chemical substances.