Management of decontamination in chemical accidents: a laboratory model.

Rapid and efficient decontamination of the skin is a major task for emergency rescue services in the event of a chemical accident involving humans. While rinsing the skin with water (and soap) has been the standard procedure, some skepticism has developed in recent years regarding the situational suitability of this method. The efficacy of three different decontamination materials/techniques (Easyderm® cleaning cloth, water-soaked all-purpose sponge, rinsing with water) in removing Capsaicin, Bromadiolone, Paraquat and 2,2'-dichlorodiethylether (DCEE) from porcine skin was compared. Different cleaning motions (wiping, twisting, pressing) with the Easyderm® were evaluated for their effectiveness in removing Capsaicin from porcine skin. Finally, the impact of different exposure times of the skin to Capsaicin on the decontamination process were investigated. Contaminant recovery rates (CRRs) were analysed in the skin and in each decontamination material using high-performance-liquid-chromatography (HPLC; used for Capsaicin, Bromadiolone, Paraquat) or gas chromatography (GC; used for DCEE). Wiping the skin with the amphiphilic Easyderm® was most effective for decontamination of Capsaicin and DCEE, while the water rinsing method gave the best results for removing Paraquat and Bromadiolone. Both wiping with the Easyderm® and rotating the Easyderm® were significantly more effective in cleaning Capsaicin-contaminated skin than pressing the Easyderm® on the contamination area alone. Prolonged exposure times of the porcine skin to Capsaicin were associated with a decrease in efficacy of the following decontamination. Emergency rescue services should have materials available that can remove both hydrophilic and hydrophobic substances from skin. Since not all of our results for comparing different decontamination materials were as distinct as we expected, there are likely several other factors determining the efficacy of skin decontamination in some cases. Time is key; therefore, first responders should try to begin the decontamination process as soon as possible after arriving at the scene.

The (in-)validity of volatile POCT parameters from patients beyond normothermia.

BACKGROUND: A common characteristic of all blood gas analyzers on the market is that measurements are processed at 37°C, not at the real patients´ temperature. Subsequently temperature-sensitive parameters can be mathematically corrected (alpha-stat method) or used directly (pH-stat method). National rules in Germany (Rili-BAEK) demand defined accuracy and precision without any restriction to samples´ temperatures or corrections. As consequence in the investigation at hand we tried to find out whether blood gas analyzers can fulfill the regulations for pCO2 and pO2 when normothermia of the matrix is not given. METHODS: Five matrices (blood from intensive care unit (ICU) patients, blood from healthy donors and 3 levels of bovine based quality control material) were tonometered at "high" and "low" partial pressures of O2 and CO2 within the RiLi-BAEK controlled range at 32, 37 and 40°C. One mL material was aspired into each blood gas (BG) syringe and analysis was accomplished immediately after. The procedure was repeated 10-fold for "high" and "low" gas concentrations and run on 4 different analyzers. At 18°C instead to the "high" one a "median" gas (n=10 as well) was employed. Every condition which constitutes of temperature (4), matrix (5), analyzer (4) and level of the partial pressure (2) led to a total of 1600 measurements. RESULTS: At 32°C or 37°C matrix temperature 7.5% to 27.5% of the pCO2(T) and between 14.5% and 28.1% of the pO2(T) results were outside the borders required by the RiLi-BAEK. At 18°C or 40°C the number of results beyond the allowed borders grows up to 82.5% for pCO2(T) and 73% for pO2(T) depending on the partial pressure (PP) level. CONCLUSIONS: High precision in automated quality control (at a constant matrix temperature) is given in modern BGAnalyzers but is counteracted in practice by non normothermic patient's temperature and unavoidable sample handling effects.

Preanalytics: The (in-)stability of volatile POCT parameters and the homogeneity of blood in syringes at the market.

BACKGROUND: In between calibrations, quality controls and so on reduce the availability of blood gas analyzers. Despite the intended urgency of the measurements, these inhibitory circumstances cause delays of measurements. The comparison of changes (primarily PO2 and PCO2, secondarily ctHb) in syringes from different suppliers and the embedding into guideline ranges are the objectives of this study. METHODS: Five matrices were tonometered at two levels within the German guideline (RiLi-BAEK) controlled range. Matrices were aspired into each syringe and blood gas analysis accomplished after 0 to 30min. The procedure was repeated 5 to 8-fold for the gas concentrations and every condition which consisted of syringe type (7), matrices (5) and time delay (7). RESULTS: Syringes produce almost identical effects on partial pressures during the 30min observation period. Initial fast changes arise when partial pressure (PP) differs widely from the atmospheric pressure and are followed by diffusion, gas production or consumption and ctHb depending effects. CONCLUSIONS: Only normal arterial blood gases without "atmospheric pollution" are not affected by the syringe materials within 30min. The homogeneity of a de-aerated and capped ICU-patients' sample is hardly to be provided after more than 10min of resting without mechanical assistance.

In Vitro Induction of Endothelial Apoptosis of the Post-Hypoxic Blood-Brain Barrier by Isoflurane but Not by Sevoflurane and Midazolam.

BACKGROUND: The effects of anesthetics on the injured brain continue to be the subject of controversial discussion. Since isoflurane has recently been shown to induce apoptosis of cerebral endothelial cells, this study compared different anesthetic compounds regarding their potential to induce cerebro-vascular apoptosis. METHODS: The in vitro model of the blood-brain barrier used in this study consisted of astrocyte-conditioned human umbilical vein endothelial cells (AC-HUVEC) has been used. After 24 h of deep hypoxia and reoxygenation or control treatment, AC-HUVEC were exposed to 0, 0.5, 1.0, or 2.0 times the minimum alveolar concentration of isoflurane or sevoflurane, or 0, 75, 150, or 300 nM of midazolam for 2 h. After 24 h, AC-HUVEC were harvested, and the degree of apoptosis was assessed by means of Western blots for the Bax and Bcl-2 ratio and, for controls and the highest concentration groups, terminal deoxynucleotidyl-mediated dUTP-biotin nick end labeling (TUNEL). RESULTS: Without hypoxic pretreatment, 2.0 MAC of isoflurane slightly increased TUNEL intensity compared to control and sevoflurane, but without any significant changes in the Bax and Bcl-2 ratio. After hypoxic pretreatment, exposure to isoflurane led to a multifold increase in the Bax and Bcl-2 ratio in a dose dependent manner, which was also significantly higher than the ratio observed in the 2 MAC sevoflurane group. TUNEL intensity in the post-hypoxic 2 MAC isoflurane group was increased by a factor of 11 vs. control and by 40 vs. sevoflurane. Sevoflurane and midazolam did not significantly alter these markers of apoptosis, when compared to the control group. CONCLUSIONS: Isoflurane administered after hypoxia elevates markers of apoptosis in endothelial cells transdifferentiated to the cerebro-vascular endothelium. Endothelial apoptosis may be a previously underestimated mechanism of anesthetic neurotoxicity. Administration of high concentrations of isoflurane in experimental settings may have negative effects on the blood-brain barrier.

Long-term NMDA receptor inhibition affects NMDA receptor expression and alters glutamatergic activity in developing rat hippocampal neurons.

Ketamine and its stereoisomer S(+)-ketamine are widely used for sedation in pediatric anesthesia and intensive care medicine. Numerous experimental studies indicate that ketamine is potentially toxic to the developing brain. Here, we examined the long-term effects of NMDA receptor blockade on NMDA receptor subunit expression, alterations in neuronal Ca(2+)-oscillations and apoptosis. Hippocampal neurons, 15 days in culture, were exposed to either S(+)-ketamine or the NMDA receptor blocker MK801 for 24h. Cytosolic Ca(2+)-concentration was determined by fluorescence microscopy and the expression of the NMDA subunits NR1, NR2A and 2B was assessed by qRT-PCR, whereas Western blots and activated Caspase-3 served to measure the extent of apoptosis. Long-term incubation with MK801 or higher doses of S(+)-ketamine resulted in a dose-dependent decreased ability of MK801 to reduce amplitude and frequency of the Ca(2+)-oscillations 15min following washout of the drug. This was accompanied by an increase in NR1 mRNA but not the NR2A and B subunit expression at the same time point. 24h following washout of the specific drug, a significant elevation of the pro-apoptotic marker BAX, as well as activated Caspase-3 positive neurons, could be detected in cultures exposed to 100µM MK801 and 25µM S(+)-ketamine. Here, we show that long-term blockade of the NMDA receptor in developing rat hippocampal neurons significantly increased NR1 subunit expression, and that this was associated with an alteration in neuronal activity. Apoptosis was only induced 24h after withdrawal of long-term blockade for high doses of S(+)-ketamine.

Flow-cytometric measurement of respiratory burst in rat polymorphonuclear granulocytes: Comparison of four cell preparation procedures, and concentration-response evaluation of soluble stimulants.

Polymorphonuclear neutrophils (PMNs) contribute to organ injury in sepsis, stroke, and other diseases. Evaluation of the oxidative burst by flow cytometry (FCM) is frequently applied to examine PMN status in humans, but rarely in rats. We established a method to assess granulocyte activation in rats by means of FCM analysis of oxidative burst. Two methods for PMN isolation involving Histopaque separation were investigated, and additionally two whole blood techniques. In addition, the concentration-response relation of the stimulants fMLP, PMA, TNF-alpha, and LPS has been determined, both as sole stimulants and for priming. A novel technique with diluted rat whole blood proved to be most appropriate for PMN preparation. One micromolar PMA and fMLP, respectively, are effective concentrations for PMN stimulation in rat whole blood. Priming with 0.1 mug/ml TNF-alpha and 1 mug/ml LPS, respectively, resulted in optimal additional stimulation. This study defined the appropriate conditions for evaluating the reactive oxygen derivate production in rat PMNs by flow cytometry. The rapid, simple, and reliable cell preparation procedure of whole blood dilution that preserves cell integrity and requires only small sample quantities. This is the first systematic dose-response evaluation of soluble stimulants of neutrophil respiratory burst in rats.

The salicylate trapping method: is oxidation of salicylic acid solution oxygen and time dependent and metal catalysed?

For a microdialytic trapping method we systematically investigated changes in concentrations of 2,5-dihydroxy-benzoic acid (2,5-DHBA) and 2,3-dihydroxy-benzoic acid (2,3-DHBA) in freshly prepared solutions of salicylic acid (SA). The solvent was 0.9% saline exposed to different atmospheric concentrations of oxygen (0, 21, and 100%). The solutions were treated by freezing-thawing and an ultrasonic bath in presence and absence of aluminium foil. Without aluminium the concentrations of 2,5-DHBA and 2,3-DHBA kept constant over an observed period of 160 min on different levels from below 20 ng/ml to about 100 ng/ml. In presence of aluminium the concentrations increased to maximum 307 ng/ml after 160 min. Ultrasonic irradiation amplified this effect to maximum 341 ng/ml. HPLC/ECD processing and quantitative analysis of dihydroxy-benzoic acids (DHBAs) in microdialysis may be artificially influenced by varying oxygen environment and metal catalysis.

The effect of fluoride and hypothermia on the in vitro metabolism of mivacurium.

IMPLICATIONS: The fluoride inhibition of mivacurium hydrolysis by pseudocholinesterase increases in hypothermia, but it will very rarely occur in clinical practice because it requires rather large fluoride concentrations (>50 micromol/L) and very low temperatures (<28 degrees C).