Effects of high-volume hemofiltration on alveolar- arterial oxygen exchange in patients with refractory septic shock

BACKGROUND：High-volume hemofiltration （HVHF） is technically possible in severe acute pancreatitis （SAP） patients complicated with multiple organ dysfunction syndrome （MODS）. Continuous HVHF is expected to become a beneficial adjunct therapy for SAP complicated with MODS. In this study, we aimed to explore the effects of fluid resuscitation and HVHF on alveolar- arterial oxygen exchange, the Acute Physiology and Chronic Health Evaluation II （APACHE II） score in patients with refractory septic shock. METHODS：A total of 89 refractory septic shock patients, who were admitted to ICU, the Provincial Hospital affiliated to Shandong University from August 2006 to December 2009, were enrolled in this retrospective study. The patients were randomly divided into two groups： fluid resuscitation （group A, n=41）, and fluid resuscitation plus high-volume hemofiltration （group B, n=48）, The levels of O2 content of central venous blood （CcvO2）, arterial oxygen content （CaO2）, alveolar-arterial oxygen pressure difference P（A-a）DO2, ratio of arterial oxygen pressure/alveolar oxygen pressure （PaO2/ PAO2）, respiratory index （RI） and oxygenation index （OI） were determined. The oxygen exchange levels of the two groups were examined based on the arterial blood gas analysis at different times （0, 24, 72 hours and 7 days of treatment） in the two groups. The APACHE II score was calculated before and after 7-day treatment in the two groups. The levels of CcvO2, CaO2 on day 7 in group A were significantly lower than those in group B （CcvO2：0.60±0.24 vs, 0.72±0.28, P〈0.05; CaO2：0.84±0.43 vs. 0.94±0.46, P〈0.05）. The level of oxygen extraction rate （O2ER） in group A on the 7th day was significantly higher than that in group B （ 28.7±2.4 vs. 21.7±3.4, P〈0.01）. The levels of P（A-a）DO2 and RI in group B on the 7th day were significantly lower than those in group A. The levels of PaO2/PAO2 and OI in group B on 7th day were significantly higher than those in group A （P〈0.05 or P〈0.01）. The APACHE II score in the two groups reduced gradually after 7-day treatment, and the APACHE II score on the 7th day in group B was significantly lower than that in group A （8.2±3.8 vs. 17.2±6.8, P〈0.01）. HVHF combined with fluid resuscitation can improve alveolar- arterial-oxygen exchange, decrease the APACHE II score in patients with refractory septic shock, and thus it increases the survival rate of patients.

Oxygen Isotope Exchange Kinetics Between Coexisting Minerals and Water in the Aral Granite Pluton of the Altay Mountains, Northern Xinjiang

Coexisting quartz, feldspar and biotite vary widely in their δ18O values and display a remarkable 18O/16O disequilibrium relation; especially, a quartz-feldspar reversal (△ 18OQUartz_feldspar< 0) exsists in the Aral granite pluton of the Altay Mountains, northern Xinjiang. The 18O / 16O exchange reaction definitely occurred between granite and water. Initial δ18O values of the granite and exotic fluid are evaluated by the mass balance consideration. The conventional method of discrimination between various magma derivations simply with δ18O values of either whole rock or separate minerals is misleading and unreliable. Experiments carried out by the authors show that the 18O / 16O exchange reaction is not accompanied by what geologists describe as petrological and mineralogical alteration effect. This decoupling relation implies that exchange reaction occurs at a relatively high temperature during subsolidus-postmagmatic cooling of magmas. The exchange mechanism is mainly diffusion-controlled. It is demonstrated through quantitative modelling that the hydrothermal system associated with the Aral pluton is long-lived (0.8-6 Ma), with a relatively high fluid flow rate (3 ×10-14 mol. s-1) and high W/ R ratio (0.79-6.14). This means that an intense flow and convection may exist at the midcrustal level of erogenic magmatic arcs.

Oxygen Atom Exchange Mechanism in Reaction of OH Radical with AsO

Oxygen atom exchange reaction mechanism in the reaction of OH radicals with AsO was investigated by means of the density functional theory (DFT) with 6 311++G( 3df,3pd ) and 6 311++G( d,p ) basis sets. The calculated results suggest that the reaction between OH and AsO should make the oxygen atoms exchange rapidly because the barrier to isomerization is significantly less than the HO-AsO bond dissociation energy.

Detailed Description of Pulse Isotopic Exchange Method for Analyzing Oxygen Surface Exchange Behavior on Oxide Ion Conductors

A novel pulse 18O-16O isotopic exchange (PIE) technique for measurement of the rate of oxygen surface exchange of oxide ion conductors was presented. The technique employs a continuous flow packed-bed micro-reactor loaded with the oxide powder. The isothermal response to an 18O-enriched pulse passing through the reactor, thereby maintaining chemical equilibrium, is measured by on-line mass spectrometry. Evaluation of the apparent exchange rate follows from the uptake of 18O by the oxide at given reactor residence time and surface area available for exchange. The developed PIE technique is rapid, simple and highly suitable for screening and systematic studies. No rapid heating/quenching steps are required to facilitate 18O tracer anneal or analysis, as in other commonly used techniques based upon oxygen isotopic exchange. Moreover, the relative distribution of the oxygen isotopologues 18O2, 16O18O, and 16O2 in the effluent pulse provides insight into the mechanism of the oxygen exchange reaction. The PIE technique has been demonstrated by measuring the exchange rate of selected oxides with enhanced oxide ionic conductivity in the range of 350?900 oC. Analysis of the experimental data in terms of a model with two consecutive, lumped steps for the isotopic exchange reaction shows that for mixed conductors Ba0.5Sr0.5Co0.8Fe0.2O3-δ(BSCF) and La2NiO4+δ the reaction is limited by the apparent rate of dissociative adsorption of O2 molecules at the oxide surface. For yttria-stabilized zirconia (YSZ), a change-over takes place, from rate-limitations by oxygen incorporation below ∽800 oC to rate-limitations by O2 dissociative adsorption above this temperature. Good agreement is obtained with exchange rates reported for these materials in literature.

Microtubular solid oxide fuel cells with a two-layer LSCF/BSCFM5 cathode

In this study,we present the development of microtubular solid oxide fuel cells(MT-SOFC)with a two-layer cathode:a composite cathode functional layer(CFL)adjacent to the buffer layer(BL)and a cathode current-collecting layer(CCCL).CFL consists of a mixture of BL material Ce_(0.9)Sm_(0.2)O_(1.95)(SDC)and perovskite Ba_(0.5)Sr_(0.5)Co_(0.75)Fe_(0.2)Mo_(0.05)O_(3-δ)(BSCFM5),which has a high exchange rate with oxygen.The widely used cathode material La_(0.6)Sr_(0.4)Co_(0.2)Fe_(0.8)O_(3-δ)(LSCF)with high electrical conductivity was used as the CCCL.A significant increase in the peak power density of the MT-SOFC to 1.2 W/cm^(2)at 850℃ was achieved using the proposed two-layer cathode.