Kinetics Study of Heterogeneous Bromine Release from the Reaction between Gaseous Ozone and Aqueous Bromide Solution.

The heterogeneous release of molecular bromine, Br2, from the reaction between gaseous ozone and aqueous bromide ion in seawater ice and sea salt aerosols is considered to be an initial source of reactive bromine species in the troposphere. Recent studies have demonstrated that the uptake of ozone by aqueous bromide solution is promoted by reactions at the gas-liquid interface. The present work investigated the heterogeneous reaction between gaseous ozone and aqueous bromide solution at atmospheric pressure and room temperature using a wetted wall flow reactor combined with a chemical ionization mass spectrometer. The emission rate of Br2 was measured as a function of gaseous ozone concentration, aqueous bromide concentration, and pH. In addition, we conducted a simple kinetics model simulation that included only bulk aqueous-phase reactions and compared the theoretical values with the experimentally determined values. The Br2 emission rates measured experimentally differ from the simulated rates at relatively high bromide concentration, as well as in the pH region of 6-9. These differences might be explained by different Br- concentration and/or deprotonation efficiency near the interface region and those in the bulk solution.

Effectiveness of preanesthetic administration of gabapentin on sedative action during intravenous sedation with propofol.

PURPOSE: There are no sufficient evidences for the sedative effect of gabapentin during anesthesia, especially intravenous sedation (IVS). The purpose of this study was to evaluate the sedative effect of gabapentin as preanesthetic medication during the IVS with propofol. METHODS: 10 volunteer subjects joined this study. They underwent propofol IVS three times on separate days. On the first day, the IVS without gabapentin was performed as a control. On the second and the third day, gabapentin 200 mg and 400 mg were administered before the IVS, respectively. The target blood concentration (CT) of propofol was gradually increased, and the bispectral index (BIS) value and Ramsay sedation score (RSS) were evaluated at each propofol CT. Postanesthetic complications and influences on vital signs were also evaluated. RESULTS: Compared to the control group, the propofol CTs in the gabapentin 400 mg group significantly reduced at the BIS values of 60 and 70 (p = 0.031 and p = 0.043, respectively), and at RSS 3, 4, 5 and 6 (p = 0.040, p = 0.004, p = 0.001 and p = 0.004, respectively). There was no significant difference in propofol CTs between the control group and the gabapentin 200 mg group. There were no abnormality and no deterioration in circulation and respiration in all groups. There were no significant increases in complications with the administration of gabapentin. CONCLUSION: The oral administration of 400 mg dose of gabapentin reduced the propofol CTs for achieving an adequate sedation level on IVS.

Water vapour effects on secondary organic aerosol formation in isoprene ozonolysis.

Secondary organic aerosol (SOA) formation from isoprene ozonolysis was investigated using a Teflon bag reactor under dry and humid conditions. Both the number and volume concentrations of SOA were found to be decreased by the addition of water vapour. Gas- and particle-phase product analyses with a negative ion chemical ionization mass spectrometer show that oligomers composed of stabilized Criegee intermediates as the chain units contribute to the SOA formation and that water vapour inhibits stabilized Criegee intermediates from forming the oligomers, resulting in the suppression of SOA formation. Additionally, it is suggested that a portion of stabilized Criegee intermediates other than CH2OO have low reactivity toward H2O, and thus can be involved in the oligomer and SOA formation even under humid conditions. Volatility estimation predicts that the oligomers containing even one or two stabilized Criegee intermediates can be partitioned into the aerosol phase.

Relative Reactivity Measurements of Stabilized CH2OO, Produced by Ethene Ozonolysis, Toward Acetic Acid and Water Vapor Using Chemical Ionization Mass Spectrometry.

We investigated the relative reactivity of stabilized CH2OO, produced by ethene ozonolysis, toward acetic acid and water vapor at a temperature of 298 ± 2 K and atmospheric pressure. Hydroperoxymethyl acetate produced through the reaction between stabilized CH2OO and acetic acid was monitored using a chemical ionization mass spectrometer as a function of the acetic acid concentration at different relative humidities. The rate of the reaction between CH2OO and water vapor depended quadratically on the water vapor concentration, suggesting that CH2OO reacted with water dimers in preference to water monomers. We obtained the bimolecular rate constant for the reaction between CH2OO and water dimer relative to the rate constant for the reaction between CH2OO and acetic acid, k3/k1, of (6.3 ± 0.4) × 10-2. The k3 value of (8.2 ± 0.8) × 10-12 cm3 molecule-1 s-1 was derived by combining with a k1 value of (1.3 ± 0.1) × 10-10 cm3 molecule-1 s-1, which has been previously reported by direct kinetic studies. The k3 value thus obtained is consistent with the absolute rate constants measured directly, suggesting that the reactivity of CH2OO is irrespective of the CH2OO generation method, namely, ethene ozonolysis or diiodomethane photolysis. We indirectly determined the yield of stabilized CH2OO from the ozonolysis of ethene of 0.59 ± 0.17 and 0.55 ± 0.16 under dry and humid (relative humidity 23-24%) conditions, respectively, suggesting that the yield is independent of the water vapor concentration. Our results suggest that hydroperoxymethyl acetate is the sole product of the reaction between stabilized CH2OO and acetic acid. The approach presented here can likely be extended to studies of the reactivities of more complicated and atmospherically relevant stabilized Criegee intermediates.

Sedative effects of oral pregabalin premedication on intravenous sedation using propofol target-controlled infusion.

PURPOSE: The sedative effects of pregabalin during perioperative period have not been sufficiently characterized. The aim of this study was to verify the sedative effects of premedication with pregabalin on intravenous sedation (IVS) using propofol and also to assess the influences of this agent on circulation, respiration, and postanesthetic complications. METHODS: Ten healthy young volunteers underwent 1 h of IVS using propofol, three times per subject, on separate days (first time, no pregabalin; second time, pregabalin 100 mg; third time, pregabalin 200 mg). The target blood concentration (C T) of propofol was increased in a stepwise fashion based on the bispectral index (BIS) value. Ramsay's sedation score (RSS) was determined at each propofol C T. Propofol C T was analyzed at each sedation level. Circulation and respiration during IVS and complications were also verified. RESULTS: Propofol C T was reduced at BIS values of 60 and 70 in both premedicated groups (100 mg: p = 0.043 and 0.041; 200 mg: p = 0.004 and 0.016, respectively) and at a BIS value of 80 in the pregabalin 200 mg group (p < 0.001). Propofol C T was decreased at RSS 4-6 in the pregabalin 100 mg group (RSS 4: p = 0.047; RSS 5: p = 0.007; RSS 6: p = 0.014), and at RSS 3-6 in the pregabalin 200 mg group (RSS 3-5: p < 0.001; RSS 6: p = 0.002). CONCLUSION: We conclude that oral premedication with pregabalin reduces the amount of propofol required to obtain an acceptable and adequate sedation level.

[Anesthetic management of a patient with osteogenesis imperfecta combined with mandibular defect].

Osteogenesis imperfecta (OI) is a rare hereditary disorder characterized by an excessive tendency to bone fractures and retarded growth. We report an anesthetic management of the patient with OI who has the history of vertebral bone fracture by coughing. A 44-year-old female underwent mandibular resection and reconstruction with a metal instrument due to ossifying fibroma 35 years ago. Since then, she had undergone mandibular resection and shaving the instrument several times because of recurrence of the tumor and/or fracture of the instrument. This time, some parts of the instrument were removed under general anesthesia since it had exposed from the skin. Difficulty in mask ventilation and intubation was predicted due to the defect of mandible and some muscles supporting the tongue and the pharynx. Awake fiber-optic nasotracheal intubation, therefore, was performed in consideration of airway obstruction. Dexmedetomidine was administered to reduce the risk of bone fracture in addition to low doses of midazolam and fentanyl. Considering incomplete respiration after extubation, the tracheal tube was extubated after inserting the tube exchanger into the trachea through the tube. The tube exchanger was pulled out after confirming spontaneous respiration and upper airway patency. The patient was cooperative, and respiratory and hemodynamic conditions were stable throughout.

Oligomerization reaction of the Criegee intermediate leads to secondary organic aerosol formation in ethylene ozonolysis.

Ethylene ozonolysis was investigated in laboratory experiments using a Teflon bag reactor. A negative ion chemical ionization mass spectrometer (NI-CIMS) using SO2Cl(-) and Cl(-) as reagent ions was used for product analysis. In addition to the expected gas-phase products, such as formic acid and hydroperoxymethyl formate, oligomeric hydroperoxides composed of the Criegee intermediate (CH2OO) as a chain unit were observed. Furthermore, we observed secondary organic aerosol (SOA) formation from the ethylene ozonolysis, and the particle-phase products were also analyzed by NI-CIMS. The CH2OO oligomers were also observed as particle-phase components, suggesting that the oligomeric hydroperoxides formed in the gas phase partition into the particle phase. By adding methanol as a stabilized Criegee intermediate scavenger, both the gas-phase oligomer formation and SOA formation were strongly suppressed. This indicates that CH2OO plays a critical role in the formation of oligomeric hydroperoxides followed by SOA formation in ethylene ozonolysis. A new formation mechanism for the oligomeric hydroperoxides, which includes sequential addition of CH2OO to hydroperoxides, is proposed.

Successful Premedication With Sublingual Midazolam Using a Suction Toothbrush.

Premedication is often used to reduce the stress associated with anesthesia-related procedures. However, in some cases, patients may not cooperate with medication delivery because of significant fear and anxiety. We report a case of an uncooperative patient with severe intellectual disabilities who was successfully premedicated with the unique technique of sublingual midazolam administration using a suction toothbrush. The 38-year-old male patient was planned to receive dental treatment under deep intravenous sedation (IVS), but he refused both intravenous cannulation and mask induction. Preanesthetic medication delivery using other routes was attempted but not accepted. As the patient tolerated toothbrushing, we used repeated practice with sublingual water administration through the toothbrush's suction hole to gradually desensitize the patient. Using that same method, sublingual midazolam was administered as a successful premedication to allow placement of a face mask for inhalational induction without distress and completion of the dental treatment under IVS. For patients who refuse other premedication routes, sublingual administration during toothbrushing with a suction toothbrush may provide a successful alternative.

Positional Change Used to Manage Postextubation Respiratory Failure in a Child With Cerebral Palsy.

Dental treatment for patients with cerebral palsy (CP) is often performed under general anesthesia due to involuntary movements that can render dental treatment difficult. Since CP is often accompanied by spasticity, care must be taken when positioning patients during general anesthesia. We report the management of a 14-year-old girl with CP and epilepsy undergoing general anesthesia for dental treatment who experienced respiratory failure due to acute thoracoabdominal muscle hypertonia after extubation. She had a history of cardiac arrest due to respiratory failure caused by acute muscle hypertonia and successful resuscitation. General anesthesia was induced after careful positioning of the patient to prevent spastic muscle stretching, and the dental treatment was completed without complications. However, upon awakening after extubation, the patient developed respiratory failure due to acute muscle hypertonia. The patient was resedated and repositioned from a supine to a sitting position, and her symptoms improved. There was no recurrence of muscle hypertonia, and she recovered fully without complications. In this case, respiratory failure associated with acute muscle hypertonia was successfully managed by position change after initial treatment with positive-pressure ventilation and propofol. It is important to be prepared for the possibility of respiratory failure associated with acute muscle hypertonia and its countermeasures when providing general anesthesia for patients with CP.

The influence of electrocardiogram (ECG) filters on the heights of R and T waves in children.

Anesthesiologists often compare intraoperative and preoperative electrocardiogram (ECG) waveforms in patients undergoing general anesthesia. In addition, many intraoperative ECG monitors have filters for removing electrocautery noise. In pediatric anesthesiology practice, we often note the appearance of elevated T waves-specifically, an increase in their height-with the use of such filters, even though no actual clinical change has occurred, which possibly leads to misdiagnosis. We investigated changes in R and T wave heights and in the T/R ratio according to the use of the strong (S) versus the diagnostic (D) filtering mode during pediatric anesthesiology. Primary outcomes were the dependence of the heights of the R and T waves on the filter mode and the correlation between rates of change in the R- and T-wave heights and heart rate (HR). In the S mode, the height of the R wave was lower (p = 0.013, η2 = 0.28) and the T/R ratio was higher than the corresponding values in the D mode (χ2 = 20.46, p < 0.001). The T/R ratios were also higher in the S mode than in the D mode, and when the D mode was changed to the S mode during tachycardia, there was a strong correlation between the rate of reduction in the R wave and HR (r = 0. 573, p = 0.041). Significant differences in the heights of the R wave and in the T/R ratio occur when using different intraoperative ECG filtering modes. Specifically, in S mode, a greater relative increase in T wave height may occur due to a significant decrease in R wave height. To avoid spurious diagnoses, anesthesiologists should be familiar with these potentially purely filter-driven changes whenever ECG is intraoperatively monitored.

Low molecular weight dicarboxylic acids, oxocarboxylic acids and α-dicarbonyls as ozonolysis products of isoprene: Implication for the gaseous-phase formation of secondary organic aerosols.

Oxidation of isoprene, a major biogenic volatile organic compound emitted from forest canopies, is a potential source of oxalic acid; the dominant species in organic aerosols. We evaluated here ozonolysis of isoprene in dry darkness as a source of oxalic (C2), malonic (C3) and succinic (C4) acids. We found that oxalic acid and methylglyoxal are dominant products within 10 min of reaction followed by glyoxylic, malonic or succinic acids. Interestingly, molecular distributions of oxidation products from early reactions (9-29 min) were characterized by the predominance of methylglyoxal followed by C2, which became dominant after 30 min. The isoprene-derived secondary organic aerosols (SOAs) showed chemical evolution with reaction time towards the molecular characteristics of dicarboxylic acids similar to those of ambient aerosols (C2>C3≥C4). The carbon-based relative abundances of methylglyoxal decreased steadily (40%→30%), while those of C2 increased with reaction time (15%→25%), but no such variations persisted for glyoxal (6-10%). This finding means that methylglyoxal is more important intermediate of oxalic acid than glyoxal. In contrast, smaller variability and lower concentrations of pyruvic and glyoxylic acids than other intermediates indicate that oxalic acid formation under dry conditions follows a different pathway than in aqueous-phase heterogeneous chemistry usually invoked for cloud/fog/atmospheric waters. Here, we propose new reaction schemes for high levels of methylglyoxal and oxalic acid via gas-phase chemical reactions with ozone and OH radicals to better interpret the ambient SOA composition. Furthermore, the relative abundances of C2 exhibit small variability from 1 to 8 h, suggesting its stable character towards the oxidation by hydroxyl radicals.

In situ measurements of atmospheric nitrous acid by chemical ionization mass spectrometry using chloride ion transfer reactions.

Recently, chemical ionization mass spectrometry (CIMS) has been widely applied to the in situ measurements of atmospheric trace species. In this article, we propose a new chemical ionization scheme using a chloride ion transfer reaction from SO(2)Cl(-) as the reagent ion and discuss the applicability of this technique to the detection of nitrous acid (HONO) in the atmosphere. From laboratory investigations, the detection sensitivity was found to depend on the flow rate of SO(2) introduced into the ion source region and the pressure inside the chemical ionization region, which suggests that the chemical ionization reaction is reversible. The detection sensitivity was well described in terms of the forward and backward rates. The present limit of detection is estimated to be 60 parts per trillion by volume (pptv) for an integration time of 1 min. Improvement of the CIMS instrument would enable the measurements of the daytime level of HONO, which might be less than 50 pptv. In addition, the possibility of the interference is discussed from thermodynamic considerations based on ab initio calculations, and the effects of the sampling artifacts are experimentally quantified.

Uptake of gas-phase nitrous acid by pH-controlled aqueous solution studied by a wetted wall flow tube.

Uptake kinetics of gas phase nitrous acid (HONO) by a pH-controlled aqueous solution was investigated by using a wetted wall flow tube. The gas phase concentration of HONO after exposure to the aqueous solution was measured selectively by the chemical ionization mass spectrometer in a high sensitive manner. The uptake rate of the gaseous HONO was found to depend on the pH of the solution. For the uptake by neutral and alkaline solutions, the gas phase concentration was observed to decay exponentially, suggesting that the uptake was fully limited by the gas phase diffusion. On the other hand, the uptake by the acidic solution was found to be determined by both the gas phase diffusion and the liquid phase processes such as physical absorption and reversible acid dissociation reaction. The decay was analyzed by the rate equations using the time dependent uptake coefficient involving the saturation of the liquid surface. While the uptake processes by the solution at pH = 2-3 were well described by those calculated using the physical and chemical parameters reported for the bulk, the uptake rates by the solution at 4 < pH < 7 deviate from the calculated ones. The present result can suggest that the pH at the liquid surface is lower than that in the bulk liquid, which is responsible for the additional resistance of mass transfer from the gas to the liquid phase.

Retained Foreign Body in the Nasal Cavity After Oral Maxillofacial Surgery.

Retained foreign bodies sometimes occur in various surgical procedures and can lead to severe complications. Foreign bodies in the oral and maxillofacial region are not rare because of the use of many small items and the natural communication with the outside environment in some areas. We experienced a case of foreign body in the nasal cavity, which was discovered 1 year later at a second operation for hardware removal after maxillofacial surgery. A small, soft material is usually placed between the nasal endotracheal tube and nostril to avoid nasal pressure ulcer at the ala of nose after prolonged anesthesia after our group's experiencing some cases of this complication. The foreign body was found in the pharynx during induction of a second anesthesia. Attention should be directed to not leaving any materials in the patient after surgery. In addition to the normal counts of sponges, needles, etc, other small nonsurgical materials used should be recorded by medical staff to help ensure nothing is retained in the patient.

Airway Management for a Pediatric Patient With a Tracheal Bronchus.

Tracheal bronchus is an ectopic bronchus almost arising from the right side of the tracheal wall above the carina. The incidence of a tracheal bronchus is reported as 0.1 to 3%. We experienced a patient with tracheal bronchus that was incidentally found at induction of anesthesia. Endotracheal intubation in a patient with tracheal bronchus might cause obstruction of the tracheal bronchus, although in this case, ventilation was not impaired.

Kinetics Study of OH Uptake onto Deliquesced NaCl Particles by Combining Laser Photolysis and Laser-Induced Fluorescence.

Despite the role of hydroxyl radical (OH) uptake onto sea-salt particles as a daytime chlorine source, affecting the chemical processes in the marine boundary layer, its uptake coefficient has not yet been confirmed by direct measurement methods. This study reports the application of a combination technique of laser flash photolysis generation and laser-induced fluorescence detection for the direct kinetic measurement of OH uptake onto deliquesced NaCl particles. The uptake coefficient was not constant and inversely depended on the initial OH concentration, indicating that the first uptake step is Langmuir-type adsorption. The resistance model, including surface processes, well reproduced the observed uptake coefficient. The model predicted an uptake coefficient for the atmospheric relevant OH concentration within the range from 0.77 to 0.95. Such values may lead to emissions of Cl2 higher than those predicted in previous studies based on other values. Hence, the proposed value may provide more reliable estimations of ozone formation, oxidation of volatile organic compounds, secondary organic aerosol formation, and lifetime of methane and elemental mercury in the marine boundary layer.

A novel discharge source of hydronium ions for proton transfer reaction ionization: design, characterization, and performance.

A novel ion source based on direct current (d.c.) discharge has been developed for proton transfer reaction ionization operated at relatively high ion drift tube pressure. The shape and geometry of the ion source are designed to maximize overall ion intensity and to minimize interference from sample air. The initial performance of the technique, including speciation and intensity of reagent ions, their stability, and the impact of artifact signals, is evaluated by means of a proton transfer reaction time-of-flight mass spectrometer (PTR-TOFMS) newly built in our laboratory. Intensities of the hydronium (H(3)O(+)) ions are typically (5-7) x 10(5) counts for a 1-min integration time with a duty cycle of approximately 1%. The fluctuations of the ion signals over a period of hours are within 4%. Although the formation of artifact ions from sample air (NO(+) and O(2) (+)), which react with volatile organic compounds (VOCs) and subsequently cause fragmentation, is observed as background signals in addition to hydronium and mono- and di-hydrate H(3)O(+) ions, intensities of both NO(+) and O(2) (+) ions are only approximately 0.5% of those of H(3)O(+) ions. Using our PTR-TOFMS system at a drift tube pressure of approximately 5 Torr, the detection sensitivities are significantly improved and the detection limits for propene, acetaldehyde, acetone, isoprene, benzene, toluene, and p-xylene are estimated to be at the sub-ppbv level for 1-min integration.