Brain Involvement in Organophosphate Poisoning

Yılmazlar, Aysun; Özyurt, Gürayten

doi:10.1006/enrs.1997.3758

Cited by 16 publications

(10 citation statements)

References 15 publications

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“…According to our results which are also similar to previous studies, SPECT appears to be sensitive to neuronal changes during initial phase of poisoning. Furthermore, these G. Ozyurt et al changes may be disappeared over time, as described previously in our studies (15)(16)(17). Thus, cerebral perfusion SPECT imaging offers a better prospect for the estimation of the severity of the initial cerebral damage, which correlates with outcome (13,21).…”

Section: Discussionmentioning

confidence: 58%

“…Other sites include the hippocampus, thalamus, medial temporal lobe, cerebellum, parietal lobe, occipital lobe, and frontal lobe (4,(9)(10)(11)(12)(13)(14). In acute OP intoxication, there are changes in the hippocampus, enthorinal and frontal cortex, amygdaloid complex, caudate nuclei, thalamus, and temporal and parietal lobes (7,(15)(16)(17). The possible mechanism of the selective white matter involvement of both forms of poisoning could be explained by the high vulnerability of end-arteries to hypoxemia, and a hemodynamic compromise in poorly vascularized zones (22,23).…”

Section: Discussionmentioning

confidence: 99%

“…Although abnormalities may be absent on MRI or CT scans, cerebral perfusion SPECT can demonstrate regional cerebral blood flow (rCBF) reductions (9,10). However, few studies have been performed on brain perfusion in patients with CO poisoning and especially OP poisoning (4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17). To the authors' knowledge, there is no other study comparing the early SPECT findings in the two types of poisoning, both of which may both cause neurological sequelae.…”

Section: Introductionmentioning

confidence: 94%

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Comparison of SPECT findings and neuropsychological sequelae in carbon monoxide and organophosphate poisoning

Özyurt

Kaya

Kahveci

et al. 2008

Clinical Toxicology

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Abnormal regional cerebral blood flow in patients with acute carbon monoxide (CO) and organophosphate (OP) poisoning was examined using (99m)Tc-hexamethylpropylene amine oxime (HMPAO) brain single photon emission computed tomography (SPECT) in fourteen patients. We evaluated the predictive significance of acute phase brain SPECT findings for long-term neuropsychological sequelae. Changes were found in the frontal, temporal, parietal lobes within the first week after both types of poisoning. The distribution of the hypoperfused cerebral areas as demonstrated by (99m)Tc-HMPAO imaging was similar in the two groups during the acute phase. Neuropsychological sequelae developed in five patients poisoned with OP and six with CO. Patients who had SPECT findings heterogeneously or in the temporal or frontal lobes displayed disorientation. Those with fronto-parietal and frontal lobe changes displayed mental confusion. Parkinsonism also was observed in patients with parieto-occipital, parietal and frontal lobe lesions. The distribution of these lesions appears to predict the long term sequelae of these poisonings, though additional studies with larger numbers of patients are needed to confirm the role of SPECT imaging in both OP and CO poisonings.

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Section: Discussionmentioning

confidence: 58%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 94%

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Comparison of SPECT findings and neuropsychological sequelae in carbon monoxide and organophosphate poisoning

Özyurt

Kaya

Kahveci

et al. 2008

Clinical Toxicology

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“…The findings represented an unexpected persistence of known short-term OP actions and, taken in parallel with the reported longterm behavioural effects, indicate that OP exposure can produce long-term changes in brain function. Perfusion defects, especially in the parietal lobe, have been detected on brain single photon emission computerised tomography (SPECT) after OP poisoning [78]. Acetylcholinesterase, in addition to being an acetylcholine hydrolysing enzyme, is also a neuromodulator that participates in the phenomenon of neuronal plasticity, i.e.…”

Section: Other Effects Of Organophosphorus Insecticidesmentioning

confidence: 99%

Organophosphorus poisoning and anaesthesia

1999

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SummaryOrganophosphorus compounds, used as insecticides and agents of chemical warfare, are a major global cause of health problems. These irreversible inhibitors of cholinesterase produce three wellrecognised clinical entities: the initial cholinergic phase, which is a medical emergency often requiring management in an intensive care unit; the intermediate syndrome, during which prolonged ventilatory care is necessary; and delayed polyneuropathy. In addition, disturbances of body temperature and endocrine function, electrolyte imbalances, immunological dysfunction and disorders of reproduction have been reported in animals and man. Vocal cord paralysis, pancreatitis, cardiac arrhythmias and a wide range of neuropsychiatric disorders are known to follow acute and chronic exposure to organophosphorus compounds. As a result of the inhibition of plasma cholinesterase, there can be increased sensitivity to drugs hydrolysed by this enzyme, e.g. suxamethonium and mivacurium. The inhibition of acetylcholinesterase causes dysfunction at the neuromuscular junction which can produce altered responses to nondepolarising neuromuscular blockers. Anaesthetists may encounter patients exposed to organophosphorus compounds either following acute poisoning, trauma (warfare) or as patients with a wide range of nonspecific disorders presenting for surgery. The traditional use of oximes and atropine in treatment has failed to reduce the morbidity and mortality associated with poisoning. The roles of agents that have reduced the toxicity of organophosphorus compounds in animal experiments are discussed as potential therapeutic agents. There is an urgent need for accurate information on the problems associated with exposure to organophosphorus compounds. This would best be achieved by collaborative research between technologically advanced countries and developing countries, where organophosphorus compounds are a leading cause of ill health.

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“…Similarly, Yilmazlar and Özyurt (1997) using brain single photon emission computerized tomography (SPECT) found evidence of focal dysfunction in patients that had experienced symptom-producing organophosphate poisoning. The investigators concluded that SPECT is a highly sensitive diagnostic tool which, in conjunction with clinical symptoms and plasma ChE activity, may prove useful for clinical prognosis of organophosphate poisoning.…”

Section: Is An Uncertainty Factor Needed To Extrapolate From Subchronmentioning

confidence: 96%

Deriving Toxicity Values for Organophosphate Nerve Agents: A Position Paper in Support of the Procedures and Rationale for Deriving Oral RfDs for Chemical Warfare Nerve Agents

Young

Opresko

Watson

et al. 1999

Human and Ecological Risk Assessment: An International Journal

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During the process of deriving oral Reference Dose (RfDs) values for chemical warfare agents, several issues arose regarding the identification of adverse effect levels and the application of uncertainty factors. For those agents that function as cholinesterase inhibitors (e.g., agents VX, GA, GB, and GD), these issues included the following: (1) Is the endpoint of blood cholinesterase inhibition an indicator of toxicity or a biomarker of exposure? (2) Can an experimental animal species be more sensitive than humans, thereby eliminating the need for an animal-to-human uncertainty factor? (3) Can the uncertainty factor that is used to extrapolate from a lowest-observed adverseeffect-level (LOAEL) to a no-observed-adverse-effect-level (NOAEL) be less than the default value of 10? (4) Can an oral RfD be derived from non-oral toxicity data? (5) Can an uncertainty factor of less than 10 be used to extrapolate from subchronic to chronic exposure (i.e., is the critical effect adequately described by the subchronic exposure data)? (6) What constitutes an adequate data base for organophosphate cholinesterase inhibitors, and what uncertainty factor should be used for an incomplete data base? Young, et al.Analysis of relevant data resulted in the following selection and justifications of uncertainty factors. For uncertainty associated with intraspecies extrapolation (UF H ), physiologic and pathologic conditions affecting cholinesterase activity levels justified maintaining a UF H of 10 for all of the nerve agents. Because available data indicated that humans tended to be more sensitive than rats regarding anticholinesterase effects, an interspecies variability (UF A ) factor of 10 was retained for agents GA, GB, and GD. For agent VX, however, the available data revealed that the domestic sheep test species exhibited sensitivity equivalent to or greater than that of humans thereby justifying a UF A of 1. For uncertainties regarding extrapolation from subchronic-to-chronic exposure data, consideration of information on the physiology of cholinergic systems and the available toxicity data for the nerve agents and other cholinesterase inhibitors indicated that a UF S of 3 was justified for all four of the nerve agents. For uncertainties regarding LOAEL-to-NOAEL extrapolation (UF L ), the selection of agent GB, GD, and VX doses resulting in cholinesterase inhibition in the absence of clinical signs of toxicity (biomarker of exposure) justified this endpoint as a minimal LOAEL and a UF L of 3. For agent GA, a NOAEL was used, and therefore no UF L was required. The uncertainty factor for data base completeness (UF D ), was based upon several considerations. Of primary concern was the fact that chronic toxicity studies are not considered an essential component of the data base requirements for cholinesterase inhibitors because of the unlikelihood that the endpoint will change with an increase in exposure time beyond that defined as a subchronic exposure. Additionally, limited data regarding reproductive and developmental toxicity ...

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Brain Involvement in Organophosphate Poisoning

Cited by 16 publications

References 15 publications

Comparison of SPECT findings and neuropsychological sequelae in carbon monoxide and organophosphate poisoning

Comparison of SPECT findings and neuropsychological sequelae in carbon monoxide and organophosphate poisoning

Organophosphorus poisoning and anaesthesia

Deriving Toxicity Values for Organophosphate Nerve Agents: A Position Paper in Support of the Procedures and Rationale for Deriving Oral RfDs for Chemical Warfare Nerve Agents

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