Yossi Rosman

Prevention of organophosphate-induced chronic epilepsy by early benzodiazepine treatment.

Poisoning with organophosphates (OPs) may induce status epilepticus (SE), leading to severe brain damage. Our objectives were to investigate whether OP-induced SE leads to the emergence of spontaneous recurrent seizures (SRSs), the hallmark of chronic epilepsy, and if so, to assess the efficacy of benzodiazepine therapy following SE onset in preventing the epileptogenesis. We also explored early changes in hippocampal pyramidal cells excitability in this model. Adult rats were poisoned with the paraoxon (450μg/kg) and immediately treated with atropine (3mg/kg) and obidoxime (20mg/kg) to reduce acute mortality due to peripheral acetylcholinesterase inhibition. Electrical brain activity was assessed for two weeks during weeks 4-6 after poisoning using telemetric electrocorticographic intracranial recordings. All OP-poisoned animals developed SE, which could be suppressed by midazolam. Most (88%) rats which were not treated with midazolam developed SRSs, indicating that they have become chronically epileptic. Application of midazolam 1min following SE onset had a significant antiepileptogenic effect (only 11% of the rats became epileptic; p=0.001 compared to non-midazolam-treated rats). Applying midazolam 30min after SE onset did not significantly prevent chronic epilepsy. The electrophysiological properties of CA1 pyramidal cells, assessed electrophysiologically in hippocampal slices, were not altered by OP-induced SE. Thus we show for the first time that a single episode of OP-induced SE in rats leads to the acquisition of chronic epilepsy, and that this epileptogenic outcome can be largely prevented by immediate, but not delayed, administration of midazolam. Extrapolating these results to humans would suggest that midazolam should be provided together with atropine and an oxime in the immediate pharmacological treatment of OP poisoning.

Imaging blood–brain barrier dysfunction as a biomarker for epileptogenesis

A biomarker that will enable the identification of patients at high-risk for developing post-injury epilepsy is critically required. Microvascular pathology and related blood-brain barrier dysfunction and neuroinflammation were shown to be associated with epileptogenesis after injury. Here we used prospective, longitudinal magnetic resonance imaging to quantitatively follow blood-brain barrier pathology in rats following status epilepticus, late electrocorticography to identify epileptic animals and post-mortem immunohistochemistry to confirm blood-brain barrier dysfunction and neuroinflammation. Finally, to test the pharmacodynamic relevance of the proposed biomarker, two anti-epileptogenic interventions were used; isoflurane anaesthesia and losartan. Our results show that early blood-brain barrier pathology in the piriform network is a sensitive and specific predictor (area under the curve of 0.96, P < 0.0001) for epilepsy, while diffused pathology is associated with a lower risk. Early treatments with either isoflurane anaesthesia or losartan prevented early microvascular damage and late epilepsy. We suggest quantitative assessment of blood-brain barrier pathology as a clinically relevant predictive, diagnostic and pharmaco!dynamics biomarker for acquired epilepsy.

Early brain magnetic resonance imaging can predict short and long- term outcomes after organophosphate poisoning in a rat model

INTRODUCTION Magnetic resonance (MR) imaging is a sensitive modality for demonstrating in vivo alterations in brain structure and function after acute organophosphate (OP) poisoning. The goals of this study were to explore early imaging findings in organophosphate-poisoned animals, to assess the efficacy of centrally acting antidotes and to find whether early MR findings can predict post-poisoning cognitive dysfunction. METHODS Sprague-Dawley rats were poisoned with the agricultural OP paraoxon and were treated with immediate atropine and obidoxime (ATOX) to reduce acute mortality caused by peripheral inhibition of acetylcholinesterase. Animals were randomly divided into three groups based on the protocol of centrally acting antidotal treatment: group 1 - no central antidotal treatment (n=10); group 2 - treated with midazolam (MID) at 30 min after poisoning (n=9), group 3 - treated with a combination of MID and scopolamine (SCOP) at 30 min after poisoning (n=9) and controls (n=6). Each animal had a brain MR examination 3 and 24 h after poisoning. Each MR examination included the acquisition of a T2 map and a single-voxel (1)H MR spectroscopy (localized on the thalami, to measure total creatine [Cr], N-acetyl-aspartate [NAA] and cholines [Cho] levels). Eleven days after poisoning each animal underwent a Morris water maze to assess hippocampal learning. Eighteen days after poisoning, animals were euthanized, and their brains were dissected, fixed and processed for histology. RESULTS All paraoxon poisoned animals developed generalized convulsions, starting within a few minutes following paraoxon injection. Brain edema was maximal on MR imaging 3 h after poisoning. Both MID and MID+SCOP prevented most of the cortical edema, with equivalent efficacy. Brain metabolic dysfunction, manifested as decreased NAA/Cr, appeared in all poisoned animals as early as 3h after exposure (1.1 ± 0.07 and 1.42 ± 0.05 in ATOX and control groups, respectively) and remained lower compared to non-poisoned animals even 24h after poisoning. MID and MID+SCOP prevented much of the 3h NAA/Cr decrease (1.22 ± 0.05 and 1.32 ± 0.1, respectively). Significant correlations were found between imaging findings (brain edema and spectroscopic changes) and clinical outcomes (poor learning, weight loss and pathological score) with correlation coefficients of 0.4-0.75 (p<0.05). CONCLUSIONS MR imaging is a sensitive modality to explore organophosphate-induced brain damage. Delayed treatment with midazolam with or without scopolamine provides only transient neuroprotection with some advantage in adding scopolamine. Early imaging findings were found to correlate with clinical consequences of organophosphate poisoning and could be potentially used in the future to predict long-term prognosis of poisoned casualties.

Airway control in case of a mass toxicological event: superiority of second-generation supraglottic airway devices.

INTRODUCTION Early respiratory support and airway (AW) control with endotracheal intubation (ETI) are crucial in mass toxicology events and must be performed while wearing chemical personal protective equipment (C-PPE). AIM The aim of this study is to evaluate the efficiency of AW control by using second-generation supraglottic AW devices (SADs) as compared with ETI and first-generation SAD while wearing C-PPE. METHODS This is a randomized crossover trial involving 117 medical practitioners. Four AW management devices were examined: endotracheal tube, the first-generation SAD, laryngeal mask AW unique and 2 second-generation SAD, the laryngeal tube suction disposable, and supreme laryngeal mask AW (SLMA). Primary end point measured were success or failure, number of attempts, and time needed to achieve successful device insertion. Secondary end point was a subjective appraisal of the AW devices by study population. RESULTS More attempts were required to achieve AW control with endotracheal tube, with and without C-PPE (P<.001). Time to achieve AW control with ETI was, on average, 88% longer than required with other devices and improved with practice. The mean times to achieve an AW were longer when operators were equipped with C-PPE as compared with standard clothing. Subjectively, difficulty levels were significantly higher for ETI than for all other devices (P<.0001). CONCLUSIONS When compared with ETI, the use of SADs significantly shortened the time for AW control while wearing C-PPE. Second-generation SAD were superior to laryngeal mask AW unique. These finding suggest that SADs may be used in a mass toxicology event as a bridge, until definite AW control is achieved.

Early in vivo MR spectroscopy findings in organophosphate-induced brain damage-potential biomarkers for short-term survival.

Organophosphates are highly toxic substances, which cause severe brain damage. The hallmark of the brain injury is major convulsions. The goal of this study was to assess the spatial and temporal MR changes in the brain of paraoxon intoxicated rats. T2‐weighted MRI and 1H‐MR‐spectroscopy were conducted before intoxication, 3 h, 24 h, and 8 days postintoxication. T2 prolongation mainly in the thalami and cortex was evident as early as 3 h after intoxication (4–6% increase in T2 values, P < 0.05). On spectroscopy, N‐acetyl aspartate (NAA)/creatine and NAA/choline levels significantly decreased 3 h postintoxication (>20% decrease, P < 0.005), and 3 h lactate peak was evident in all intoxicated animals. On the 8th day, although very little T2 changes were evident, NAA/creatine and choline/creatine were significantly decreased (>15%, P < 0.05). Animals who succumbed had extensive cortical edema, significant higher lactate levels and a significant decrease in NAA/creatine and NAA/choline levels compared to animals which survived the experiment. Organophosphates‐induced brain damage is obvious on MR data already 3 h postintoxication. In vivo spectroscopic changes are more sensitive for assessing long‐term injury than T2‐weighted MR imaging. Early spectroscopic findings might be used as biomarkers for the severity of the intoxication and might predict early survival. Magn Reson Med, 2012.

The Organophosphate Paraoxon and Its Antidote Obidoxime Inhibit Thrombin Activity and Affect Coagulation In Vitro

Organophosphates (OPs) are potentially able to affect serine proteases by reacting with their active site. The potential effects of OPs on coagulation factors such as thrombin and on coagulation tests have been only partially characterized and potential interactions with OPs antidotes such as oximes and muscarinic blockers have not been addressed. In the current study, we investigated the in vitro interactions between coagulation, thrombin, the OP paraoxon, and its antidotes obidoxime and atropine. The effects of these substances on thrombin activity were measured in a fluorescent substrate and on coagulation by standard tests. Both paraoxon and obidoxime but not atropine significantly inhibited thrombin activity, and prolonged prothrombin time, thrombin time, and partial thromboplastin time. When paraoxon and obidoxime were combined, a significant synergistic effect was found on both thrombin activity and coagulation tests. In conclusion, paraoxon and obidoxime affect thrombin activity and consequently alter the function of the coagulation system. Similar interactions may be clinically relevant for coagulation pathways in the blood and possibly in the brain.

Using the skin protective lotion IB1 as a substitute for chemical protective gloves

We aimed to evaluate the performance of medical personnel in using the IB1 topical protective lotion on their hands and wrists together with standard disposable medical gloves, compared to standard-issued medical chemical protective gloves. This randomized cross-over study included 144 medical personnel. Primary endpoints were time-to-completion of autoinjection; success rate, number of attempts, and time-to-achieve successful endotracheal intubation; time-to-achieve satisfactory tube fixation; time-to-draw and inject the content of an ampoule; and the total time-to-perform all medical procedures. Secondary endpoints included the subjective assessment of convenience to perform these four procedures with each protective measure. Mean time was significantly shorter using IB1 compared to chemical protective gloves for tube fixation, ampoule drawing, and the total time-to-perform all procedures (58.6±22.7 seconds vs. 71.7±29.7; 31.5±21.8 vs. 38.2±19.4; 137.4±56.1 vs. 162.5±63.6, respectively; P<.001 for all). For all medical procedures, the use of IB1 was reported as significantly more convenient than the use of chemical protective gloves (P<.001 for all comparisons). IB1 with standard medical gloves significantly shorten the time-to-perform medical procedures requiring fine motor dexterities and is subjectively more convenient than chemical protective gloves. IB1 should be considered as an appropriate alternative for medical teams in a chemical event.