Performance characteristics of a 'to and fro' disposable soda lime canister

The performance of the Intersurgical disposable soda lime canister was compared to British Pharmacopoeia standards for carbon dioxide absorption and to other carbon dioxide absorber systems. This canister system more than adequately fulfilled the equivalent of the British Pharmacopoeia standard for CO2 absorption. It performed efficiently for over 3 h of continuous use, absorbing 200 ml.min-1 at varying combinations of tidal volume and ventilation rate. Efficiency was not dependent on close matching of tidal volume with canister volume and there was no channelling of gases. Heat was generated by the reaction between soda lime and CO2 and the maximum temperature recorded in the system was 42.1 degrees C. Under clinical conditions this should pose no threat of thermal injury to the patient.

Treatment of osteomyelitis with antibiotic-soaked porous glass ceramic

We have developed a new drug delivery system using porous apatite-wollastonite glass ceramic (A-W GC) to treat osteomyelitis. A-W GC (porosity, 70% and 20% to 30%), or porous hydroxyapatite (HA) blocks (porosity 35% to 48%) used as controls, were soaked in mixtures of two antibiotics, isepamicin sulphate (ISP) and cefmetazole (CMZ) under high vacuum. We evaluated the release concentrations of the antibiotics from the blocks. The bactericidal concentration of ISP from A-W GC was maintained for more than 42 days, but that from HA decreased to below the detection limit after 28 days. The concentrations of CMZ from both materials were lower than those of ISP. An in vivo study using rabbit femora showed that an osseous concentration of ISP was maintained at eight weeks after implantation. Osteoconduction of the A-W GC block was good. Four patients with infected hip arthroplasties and one with osteomyelitis of the tibia have been treated with the new delivery system with excellent results.

The in vitro and in vivo indomethacin release from self-setting bioactive glass bone cement

The in vivo and in vitro drug release profiles from a self-setting bioactive CaO-SiO2-P2O5 glass bone cement containing indomethacin as a model drug were investigated. The cement containing 2% and 5% indomethacin (IMC) powder hardened within 5 min after mixing with ammonium phosphate buffer. After setting, in vitro drug release from drug-loaded cement pellets in a simulated body fluid (SBF) at pH 7.25 and 37 degrees C continued for two weeks. The hardened cement gradually formed low-crystallinity hydroxyapatite during the drug release test in SBF. An IMC-loaded cement device (2% and 5% drug) was implanted in the subcutaneous tissue on the back of rats. The in vivo IMC release from the cement increased and attained maximum levels (Cmax of 2% and 5% drug-loaded cements was 0.27 and 3.37 micrograms/ml, respectively) at Tmax, 3 and 0.5 d, respectively, upon subcutaneous (s.c.) administration in rats. This suggested that the s.c. administration of the cement provided IMC release for a much longer period than s.c. administration of the solution, and the plasma IMC concentration was dependent on the drug concentration in the cement. The plasma IMC concentration and the area under the curve from 2% and 5% IMC-loaded cements in rats were dependent on the concentration of IMC in the cements. The in vivo IMC concentration in plasma obtained by the deconvolution method was much lower than that delivered in SBF in vitro. Scanning electron microscopy and photomicrographs of cross sections showed that the bioactive bone cement had excellent biocompatibility with the surrounding soft tissues.

[Carbon monoxide concentrations during low flow anesthesia]

Elevated carbon monoxide (CO) concentrations have been reported during general anesthesia using inhaled anesthetics. In order to assess the safety of low flow anesthesia, we examined CO concentrations in anesthesia circuit during low flow anesthesia. Thirty patients were randomly divided into two groups. Anesthesia was induced with intravenous thiopental 5 mg.kg-1 and maintained with oxygen 2 l.min-1, nitrous oxide 4 l.min-1 and isoflurane (group H) or oxygen 0.5 l.min-1, nitrous oxide 0.5 l.min-1 and isoflurane (group L). The concentrations of CO in exhaust gas of anesthetic gas monitor were examined by CO sensor (XC-341, Shinkosumosudenki, Tokyo) and COHb was analyzed. The concentrations of CO in group L were significantly higher than in group H. The highest value, however, was 30 ppm. The COHb levels were slightly higher in group L, but the highest value was 2.1%. We consider that these results show no clinical risk and low flow isoflurane anesthesia may be performed safely. Measuring the CO concentrations is helpful for the safety of low flow anesthesia.

[Causes for the reaction between dry soda lime and halogenated inhalation anesthetics]

All volatile anesthetics undergo chemical breakdown to multiple, partly identified degradation products in the presence of dry soda lime. These chemical reactions are highly exothermic, ranging from 100 degrees C for halothane to 120 degrees C for sevoflurane. The increase in temperature correlates with the moisture content of the soda lime, being maximal below 5%. Sevoflurane and isoflurane were exposed to dry soda lime in a circle system. The anaesthetic gas was condensed in a series of cold temperature traps and the degradation products of the volatile anesthetics were analysed using GC/MS. Surprisingly, neither sevoflurane nor its degradation products could be measured in the gas-flow emerging from the soda lime during the first 15-20 min of exposure. After 20 minutes, larger quantities of methanol, compounds C and D as well as compounds A and B were detected. After 40-60 min of exposure, sevoflurane's degradation markedly decreased and unaltered sevoflurane emerged from the soda lime canister. Additionally, using isoflurane in the same experimental set-up resulted in various degradation products due to its reaction with dry soda lime. Obviously, all volatile anesthetics are prone to such a reaction. In conclusion, sevoflurane and isoflurane react with dry soda lime. These reactions are caused by the presence of two components of soda lime, sodium hydroxide and potassium hydroxide. A modification of soda lime to prevent its reaction with volatile anaesthetics is discussed.

[Various reactions of sevoflurane with the individual components of soda lime]

The various components of commercial soda lime (sodium hydroxide, potassium hydroxide, calcium hydroxide, barium hydroxide) were studied in terms of their reactivity with sevoflurane at its boiling point (59 degrees C). A simple closed system, a reflux cooler, served as a model. Analyses were performed by GC/MS. Besides sevoflurane, we identified four compounds: A, B, C, and D. Free methanol, formaldehyde and formic acid could not be found. Presumably methanol is transferred from an intermediate formalin-semiacetal of the hexafluorisopropanol. Calcium hydroxide and barium hydroxide showed little reaction with sevoflurane, whereas larger amounts of reaction products were observed with sodium hydroxide and potassium hydroxide. The alkali hydroxides of sodalime are presumably responsible for its reaction with halogenated inhalation anaesthetics. We therefore conclude that decomposing reactions of halogenated inhalation anesthetics with dry soda lime could be prevented by using a newly developed soda lime.

[Heat production from reaction of inhalation anesthetics with dry soda lime]

There are some case reports about excessive heat production in the absorbent canister when sevoflurane or enflurane are washed into a circle containing dried soda lime. This observation was often made in the DRAGER ISO 8 circle system with the gas inlet upstream of the soda lime canister with the gas-flow from bottom to top.

METHODS

The temperature in the center of an absorbent canister was measured 3.0 cm and 7.5 cm above the bottom. Soda lime (DRAGERSORB 800) was dried in an O2 stream for 2-3 days until there was no further loss in weight. 5 Vol% of desflurane, enflurane, isoflurane and sevoflurane in 2 1/min O2 or 4 Vol% of halothane in 2.5 I/min O2 were continuously fed into the canister. The concentration of the respective inhalational agents were measured after the soda lime canister using a DATEX Capnomac. Experiments were performed at ambient temperatures of 20-22 degrees C.

RESULTS

A considerable temperature increase was achieved with all anaesthetics. The highest temperatures were measured at the upper sensor with 56-58 degrees C for desflurane, 76-80 degrees C for enflurane and isoflurane, 84-88 degrees C for halothane and 126-130 degrees C for sevoflurane. IR-detection for some agents was considerably delayed or the time course indicated that other compounds might have formed which absorb at the wavelength monitored.

DISCUSSION

The high temperatures indicate the degradation rather than absorption of the volatile anaesthetics. CO is known to be degradation product of all currently used volatile anaesthetics except sevoflurane. Sevoflurane, however, produced the highest temperatures passing through dried soda lime. There are no reports about new specific breakdown products for sevoflurane on dried soda lime.

Partly exhausted soda lime or soda lime with water added, inhibits the increase in compound A concentration in the circle system during low-flow sevoflurane anaesthesia

We performed low-flow sevoflurane anaesthesia at a flow rate of 1 litre min-1 in three groups (n = 8 each) using 600 g of fresh soda lime (control group), 600 g of soda lime with 60 ml of water added (water group) or 600 g of soda lime saturated with carbon dioxide, that is partly exhausted soda lime (carbon dioxide group). Degradation products in the system were measured hourly. Inspired and end-tidal carbon dioxide and sevoflurane concentrations, carbon dioxide and temperature of the soda lime were monitored. CF2 = C(CF3)-O-CH2F (compound A) was the only sevoflurane degradation product detected. The mean maximum concentration of compound A was significantly higher in the control group (mean 16.0 (SD 5.0) ppm) than in the water (1.4 (1.0) ppm) or carbon dioxide (4.0 (1.8) ppm) group, and the maximum temperature of the soda lime was significantly lower in the carbon dioxide group (30.7 (3.5) degrees C) than in the control (43.4 (1.8) degrees C) or water (40.8 (1.8) degrees C) group (P < 0.05). The use of partly exhausted soda lime or soda lime with water added reduced compound A concentrations in the system during low-flow sevoflurane anaesthesia.

[Interactions of dry soda lime with enflurane and sevoflurane. Clinical report on two unusual anesthesias]

We report two cases of unexpected courses of inhalation anaesthesia with sevoflurane and enflurane which were caused by the presence dry soda lime. Case 1: During mask induction of a healthy 46-year-old female patient for elective hysterectomy it was noted that the vaporizer setting of 5% sevoflurane (in 50% O2, 50% N2O) did not result in the expected increase of inspiratory sevoflurane concentration. At the same time, the anaesthesiologist observed that the patient did not lose consciousness while the temperature of the soda lime canister increased sharply and the colour of the soda lime turned to blue with condensing water visible in the tubing. It was later determined that this anaesthesia machine had not been used for more than 2 weeks. Analysis of the soda lime showed a water content of <1%. Case 2: Following intravenous induction of a non-smoking 64-year-old male patient for elective gastrectomy, it was noted that the concomitant inhalation of enflurane was associated with a sharp rise in the temperature of the soda lime canister, a colour change of the soda lime to blue and a decrease in the measured inspiratory enflurane concentration despite an unchanged or even increased vaporizer setting. Arterial blood gas analysis revealed a CO-Hb concentration of 8.8% with otherwise normal acidity and partial gas pressures. Immediate change of the absorbant resulted in a decline in the CO-Hb concentration to 6.9% within 3 h. It was later determined that the anaesthesia machine had not been used for 34 h. Analysis of the soda lime showed a water content of 5.4%.

DISCUSSION

Both case reports were associated with a rise in temperature and a colour change to blue of the soda lime. Reactions of desflurane, enflurane or isoflurane with dry soda lime resulting in significant CO-Hb formation have been previously reported. Reactions of sevoflurane with dry soda lime have been observed but have so far not been published. Until further analysis of these phenomena is completed, it is mandatory for the patient's safety to guarantee that only soda lime with a sufficient water content be used for clinical anaesthesia.

[Rutherford back-scattering spectrometry and photoelectron spectroscopy of the calcium/titanium interface]

Evaporation of calcium on commercially pure titanium was performed. Heatings under vacuum or oxygen flow improved calcium diffusion in the titanium substrate. X-Ray Photoelectron Spectroscopy did not revealed any superficial segregation of titanium but revealed the formation of CaCO3. The film formed on titanium was characterized using X-ray photoelectron spectroscopy with argon-ion sputtering. The results indicated that: the surface layer consisted of CaCO3; the interface contained CaCP3, CaO et TiO2; only CaO was present in the bulk titanium.

Reduction in nitrogen dioxide concentration by soda lime preparations during simulated nitric oxide inhalation

Nitrogen dioxide is formed during delivery of inhaled nitric oxide for the treatment of patients with pulmonary hypertension. Soda lime has been shown to absorb nitrogen dioxide. We tested three different commercially available soda lime preparations (Sodasorb, Drägersorb 800 and Sofnolime) for their efficacy in absorbing nitrogen dioxide and nitric oxide during simulated nitric oxide inhalation. All soda lime preparation absorbed nitrogen dioxide (15%, 24% and 34%, respectively). To test if this difference could be attributed to the potassium hydroxide (KOH) content of the different preparations, two other preparations with a higher (3.0% and 7.3% w/w, respectively) KOH content were tested and we found an increase in nitrogen dioxide removal up to 47% and 46%, respectively. We conclude that soda lime absorbed nitrogen dioxide during nitric oxide inhalation. This effect seemed to be moderate under simulated clinical conditions, but increased using soda lime with a higher KOH content. Nevertheless, we recommend continuous monitoring of inspired nitrogen dioxide concentration during clinical inhalation of nitric oxide.

Bone bonding ability of bioactive bone cements

The bone bonding ability of three types of bioactive bone cement A, B, and C consisting of glass or glass ceramic powder and bisphenol-alpha-glycidyl methacrylate resin was evaluated. Type A contained MgO-CaO-SiO2-P2O5-CaF2 glass powder; Type B, MgO-CaO-SiO2-P2O5-CaF2 glass ceramic powder; and Type C, MgO free CaO-SiO2-P2O5-CaF2 glass powder. Rectangular plates (2 x 10 x 15 mm) of Types A, B, C, and polymethylmethacrylate cements were implanted into the tibial metaphyses of male rabbits and the failure load measured by mechanical failure testing (detaching test) 10 and 25 weeks after implantation. The failure loads of Types A, B, C, and polymethylmethacrylate cements were respectively, 29.52, 41.48, 28.22, and 0.29 N at 10 weeks and 33.42, 41.27, 33.64, and 0.20 N at 25 weeks. Examination of the bone cement interface revealed that all the bioactive bone cements achieved direct bone contact with the bone. These results showed that all three types of bioactive bone cement have the ability to bond to bone, and the cement containing glass ceramic powder revealed higher bonding strength than did those containing glass powder.

Bioeutectic: a new ceramic material for human bone replacement

In the present work, a new way of obtaining bioactive ceramic materials with eutectic morphology is presented. To this purpose the binary system wollastonite-tricalcium phosphate was selected, taking into account the different bioactivity behaviour of both phases. The material is formed by quasi-spherical colonies composed of alternating radial lamellae of wollastonite and tricalcium phosphate. In in vitro experiments the material presents a high reactivity, with the formation of two well-differentiated zones of hydroxyapatite, one formed by alteration of the eutectic material with solution of the wollastonite into the simulated body fluid and subsequent pseudomorphic transformation of the tricalcium phosphate into hydroxyapatite, and the other, in the last stages of the experiments, by deposition of hydroxyapatite onto the surface of the material. The hydroxyapatite morphology, formed at the beginning of the reaction, is similar to that of porous bone. The method used opens the opportunity to develop a new family of bioactive materials with different constituents, binary or ternary, for which the authors propose the general name of bioeutectics.

Natural (Mg,Fe)SiO3-ilmenite and -perovskite in the Tenham meteorite

The minerals (Mg,Fe)SiO3-ilmenite and -perovskite were identified in the shock-induced veins in the Tenham chondritic meteorite. Both phases are inferred to have transformed from pyroxene at high pressures and temperatures by shock metamorphism. Columnar-shaped ilmenite grains, one of two types of morphologies, have a topotaxial relationship with neighboring pyroxene grains, indicating shear transformation. Granular-shaped perovskite grains showed a diffraction pattern consistent with orthorhombic perovskite, but these grains were not stable under the electron beam irradiation and became amorphous. The higher iron concentration in both phases compared with those experimentally reported may suggest their metastable transition from enstatite because of shock compression.

High carboxyhemoglobin concentrations occur in swine during desflurane anesthesia in the presence of partially dried carbon dioxide absorbents

BACKGROUND

Increased carboxyhemoglobin concentrations in patients receiving inhalation anesthetics (desflurane, enflurane, and isoflurane) have been reported. Recent in vitro studies suggest that dry carbon dioxide absorbents may allow the production of carbon monoxide.

METHODS

The authors used high fresh oxygen flow (5 or 10 l/min) through a conventional circle breathing system of an anesthesia machine for 24 or 48 h to produce absorbent drying. Initial studies used 10 l/min oxygen flow with the reservoir bag removed or with the reservoir bag left in place during absorbent drying (this increases resistance to gas flow through the canister). A third investigation evaluated a lower flow rate (5 l/min) for absorbent drying. Water content of the absorbent and temperature were measured. Pigs received a 1.0 (human) minimum alveolar concentration desflurane anesthetic (7.5%) for 240 min using a 1 l/min oxygen flow rate with dried absorbent. Carbon monoxide concentrations in the circuit and carboxyhemoglobin concentrations in the pigs were measured.

RESULTS

Pigs anesthetized with desflurane using Baralyme exposed to 48 h of 10 l/min oxygen flow (reservoir bag removed) had extremely high carboxyhemoglobin concentrations (more than 80%). Circuit carbon monoxide concentrations during desflurane anesthesia using absorbents exposed to 10 l/min oxygen flow (reservoir bag removed, 24 h) reached peak values of 8,800 to 13,600 ppm, depending on the absorbent used. Carboxyhemoglobin concentrations reached peak values of 73% (Baralyme) and 53% (soda lime). The water content of Baralyme decreased from 12.1 +/- 0.3% (mean +/- SEM) to as low as 1.9 +/- 0.4% at the bottom of the lower canister (oxygen flow direction during drying was from bottom to top). Absorbent temperatures in the bottom canister increased to temperatures as high as 50 degrees C. With the reservoir bag in place during drying (10 l/min oxygen flow), water removal from Baralyme was insufficient to produce carbon monoxide (lowest water content = 5.5%). Use of 5 l/min oxygen flow (reservoir bag removed) for 24 h did not reduce water content sufficiently to produce carbon dioxide with desflurane.

CONCLUSIONS

An oxygen flow rate of 10 l/min for 24 h in a conventional anesthesia circuit can dry carbon dioxide absorbents sufficiently to produce extremely high levels of carbon monoxide with high carboxyhemoglobin concentrations in desflurane-anesthetized pigs. When the reservoir bag is in place on the anesthesia machine or when a lower oxygen flow rate (5 l/min) is used, carbon dioxide absorbent drying still occurs, but 24-48-h exposure time is insufficient to allow for carbon monoxide production with desflurane.

In vitro study of intradentinal calcium diffusion induced by two endodontic biomaterials

The aim of this in vitro study was to assess intratubular calcium penetration induced by two root canal restoration materials, one calcium oxide based, and the other calcium hydroxide based. Pig teeth were restored with no preliminary root canal preparation. The filing materials were left in place for 8, 15, or 21 days. The samples were then examined using various microanalytical techniques and, in parallel, by backscattered electron image (BEI) scanning electron microscopy. The Ca/P ratios obtained by microanalysis were higher for samples restored with calcium oxide. In addition, the distances over which the ratios increased were also greater than those obtained using calcium hydroxide. BEI photographs confirm these results and show corresponding retrodiffusion fringes.

[Quantification of dehydration of soda lime in clinical circumstances]

HYPOTHESIS AND OBJECTIVES

When the CO2 absorbents, soda lime and baralime, have lost their normal level of hydration, they may react with certain halogenated anesthetics to produce appreciable levels of carbon monoxide. The degree of absorbent desiccation has been considered the limiting factor for this phenomenon. This study quantifies the level of dehydration of lime produced under clinical conditions and the influence of several factors.

MATERIAL AND METHOD

Desiccation was determined: 1) at set periods of time (3, 7 and 14 days) after clinical use of fresh soda lime in general anesthesia using a fresh gas flow (FGF) of 6 l/min, and 2) after gas had been crossing the continuous flow (CF) oxygen reservoir at 7 l/min for 17 and 65 hours. Two anesthetic systems were used: a) the Ohmeda Excel-210, in which the continuous FGF did not cross the reservoir and b) the Siemens Ventilator 710, in which the FGF did cross the reservoir. The experiments were repeated with three types of lime.

RESULTS

The clinical use of lime for 3, 7 and 14 days caused different levels of desiccation, with decreases in hydration of up to 50% and 14 days. Nevertheless, water content was always over 5%, a level at which no reaction with halogenated agents takes place. After 17 and 65 hours of CF in the circuit where continuous FGF did not pass through the canister, the water content did not change. With the Siemens 710 circuit, in which the continuous FGF crossed the canister, the dehydration level was 1.2 +/- 0.3% after 17 hours and 0.7 +/- 0.3% after 65 hours, a level that can produce CO upon reaction between lime and halogenated gases. The type of lime used had little effect.

CONCLUSIONS

Lime does not desiccate to levels able to produce CO in daily use, regardless of the FGF system used. The phenomenon of desiccation depends on two factors: 1) use of anesthetic equipment in which continuous FGF conditions require gas to pass through the canister, and 2) the maintenance of CF for a sufficient period of time.

Effect of the substitution of Y2O3 for CaO on the bioactivity of 2.5CaO.2SiO2 glass

Glasses were prepared whose composition is defined by the following general formula: (2.5-x)CaO.x/3Y2O3.2SiO2 (0 < or = x < or = 1). Their behaviour when they were soaked in a simulated body fluid (SBF) and their thermal properties (glass transformation and softening temperatures, Tg and Ts respectively) were studied Tg and Ts increase with the Y2O3 content. The trend can be explained on the basis of the increased structural rigidity when Ca2+ ions are substituted by Y2+ ions, because of the formation of stronger bonds to the oxygen. The bioactivity was studied by means of electron microscopy equipped with an energy dispersive system for elemental analysis and IR spectroscopy. All the glasses studied except the one with the greatest amount of Y2O3. x = 1.0, reacted with SBF by forming a calcium phosphate layer. The experimental results suggest that the bioactivity is negatively influenced by the Y2O3 content: the tendency to form a calcium phosphate layer is reduced the greater the amount of CaO substituted. A comparison with literature data indicates that the amount of Y2O3 that can be substituted depends on the CaO content of the base CaO-SiO2 glass. The experimental results are in good agreement with the mechanism reported in the literature. After 7 days soaking, crystalline hydroxyapatite is formed in the Y2O3-free glass and in the glasses of low Y2O3 content (x-0.2).

Preparation and characterization of double layered coating composed of hydroxyapatite and perovskite by thermal decomposition

A new modified thermal decomposition method is described for preparing a double layered coating on titanium plates which includes an initial perovskite (CaTiO3) layer followed by a hydroxyapatite (HA) layer on top. The characterization of the coating was studied by X-ray diffractometry and infrared spectroscopy and indicated that the double layer consisted of carbonate HA and CaTiO3 and the thickness of the layer was 4 microns. The coating was performed on the inner surfaces of 50-200 microns sized pores and was also consistent in the smallest of the pores even those of 50 microns. Bone formation was examined in canines at 2-32 week intervals and was dominant on coated plates and in large-sized pores before 16 weeks. However, after 16 weeks bone ingrowth was similar in non-coated and coated plates and in all pore sizes. The results indicated that HA could only influence early bone ingrowth, though good bone ingrowth into small pores indicated that HA exhibited enhanced osteocompatibility. Our methodology ensured the stability of the HA layer consequently minimizing the problems associated with HA loss.

Decomposition of volatile anesthetics in soda lime

Soda lime mediated decomposition products of volatile anesthetics--halothane, enflurane, isoflurane and sevoflurane--and the degree of degradation, toxicity and concentration in an anesthetic circuit equipped with a model lung are described. These anesthetics undergo decomposition by soda lime as follows: halothane decomposes to yield difluorochlorobromoethylene and trifluorochloroethane; enflurane decomposes to yield l-chloro-l,2-difluorovinyl difluoromethyl ether; isoflurane decomposes to yield 2,2-difluoro-l-chlorovinyl difluoromethyl ether and fluoroform; sevoflurane decomposes to yield fluoromethyl 2,2-difluoro-l-(trifluoromethyl)vinyl ether, fluoromethyl 2-methyl-2,2-difluoro-l-(difluoromethylene)ethyl ether, two isomers of fluoromethyl 2-methoxy-2-fluoro-l-(trifluoromethyl)vinyl ether and fluoromethyl 2,2-difluoro-l-(difluoromethoxy ethyl)vinyl ether. Almost all degraded compounds of these volatile anesthetics are produced by elimination of hydrofluoride from adjacent carbon atoms by soda lime.

Effects of liming on uptake of lead and cadmium by Raphanus sativa

Although liming soil to reduce the heavy metal uptake by plants has been recommended generally, there is some disagreement with the practice based on the results of recent studies. Radishes, Raphanus sativa L. var. Paekyong, were grown in greenhouse pots which were filled with soils treated with 1.52 mg kg(-1) Cd and 25.37 mg kg(-1) Pb, respectively and amended with lime at five rates of 0, 0.25, 0.5, 1.0, and 2.0% by dry soil weight. Plants were harvested three times at 25, 50, and 75 days after sowing and the roots and shoots separated. After the plant samples were digested with HNO3-HClO4, Cd was analyzed by flame AAS and Pb by graphite furnace AAS. A large amount of Cd was translocated into the radishes, which accumulated dramatically with time. Compared to Cd, Pb uptake was very low and accumulated slowly. Cd contents were very much higher in the shoots than the roots, but Pb was not significantly different. Liming or increased soil pH decreased Cd uptake markedly with increased lime level; Pb influence was negligible. Yields were decreased with excessive liming, but not by the levels of Cd or Pb added.

Morphological studies of pseudowollastonite for biomedical application

Pseudowollastonite ceramic (psW) composed of CaO.SiO2 was found to be bioactive in a simulated body fluid environment. The chemical reaction initiated at the material surface resulted in hydroxyapatite (HA) formation. These bone-bonding properties are essential for securing the necessary physico-chemical integration of the material with living bone. Materials behaving in this way can be considered for potential biomedical application as bone tissue substitute for a natural bone repair or replacement as implant. A mechanism of hydroxyapatite formation on pseudowollastonite ceramics surface was investigated during exposure to a stimulated body fluid (SBF) for a period of 3 weeks. Morphology and structure of the surface product and its original substrate was examined by thin-film X-ray diffraction, scanning electron microscopy and high-resolution transmission electron microscopy. HA crystals were found to form on an amorphous silica intermediate layer. (100) lattice planes of HA were resolved and identified. Concentration of ions in the SBF and pH of the SBF were monitored throughout the exposure. Additional pH measurements were made at the interface of psW with SBF. The HA formation occurred when there was a sudden increase of pH from 7.25 to 10.5 at the interface of psW with SBF as a result of ionic exchange between 2H+ and Ca2+ within the psW network. This ionic exchange transformed the psW crystals into an amorphous silica phase. The appropriate pH and the ion concentrations were essential for partial dissolution of the amorphous silica phase and subsequent precipitation of a Ca-P rich phase which then transformed to HA.

Factors affecting production of compound A from the interaction of sevoflurane with Baralyme and soda lime

Various alkali (e.g., soda lime) convert sevoflurane to CF2=C(CF3)OCH2F, a vinyl ether called "Compound A, " whose toxicity raises concerns regarding the safe administration of sevoflurane via rebreathing circuits. In the present investigation, we measured the sevoflurane degradation and output of Compound A caused by standard (13% water) Baralyme brand absorbent and standard (15% water) soda lime, and Baralyme and soda lime having various water contents (including no water). We used a flow-through system, applying a gas flow rate relative to absorbent volume that roughly equaled the rate/volume found in clinical practice. Both absorbents, at similar water contents, temperatures, and sevoflurane concentrations, produced roughly equal concentrations of Compound A. Dry and nearly dry absorbents produced less Compound A early in exposure to sevoflurane, and more later, than standard absorbents. Increases in temperature and sevoflurane concentration increased output of Compound A. Both absorbents, especially when dry, also destroyed Compound A, the concentration exiting from absorbent resulting from a complex sum of production and destruction. We conclude that the variability of concentrations of Compound A found in clinical practice may be largely explained by the inflow rate used (i.e., by rebreathing), sevoflurane concentration, and absorbent temperature and dryness. The effect of dryness is complex, with fresh dry absorbent destroying Compound A as it is made, and with dry absorbent that has been exposed to sevoflurane for a period of time providing a sometimes unusually high output of Compound A.

Chemical safety of U.S. Navy Fleet soda lime

Contamination was suspected of U.S. Navy Fleet soda lime (High Performance Sodasorb) when an ammonia-like odor was reported during its use in August 1992. This material contained indicator dye and was used for carbon dioxide absorption during diving. This incident had a major impact on the U.S Navy diving program when the Navy temporarily banned use of Sodasorb and authorized Sofnolime as an interim replacement. The Naval Medical Research Institute was assigned to investigate. Testing involved sampling from the headspace (gas space) inside closed buckets and from an apparatus simulating conditions during operational diving. Volatile organic compounds were analyzed by gas chromatography and mass spectrometry; ammonia and amines were measured by infrared spectroscopy. Significant amounts of ammonia (up to 30 ppm), ethyl and diethyl amines (up to several ppm), and various aliphatic hydrocarbons (up to 60 ppm) were detected during testing of both Sodasorb and Sofnolime. Contaminants were slowly removed by gas flow and did not return. The source(s) of the ammonia and amines are unknown, although they may result from the breakdown of the indicator dye. Hydrocarbon contamination seems to result from the materials of which the bucket is constructed. Unfortunately, evaluation of potential hazards associated with this contamination is difficult, due in part to the large number of variables of operational use and the absence of appropriate exposure limits. Based on these findings, the U.S. Navy has begun to phase in, for all diving, non-indicating soda lime that will be required to meet defined contaminant limits.