Severe electrolyte disorders following cardiac surgery: a prospective controlled observational study

Introduction

Electrolyte disorders are an important cause of ventricular and supraventricular arrhythmias as well as various other complications in the intensive care unit. Patients undergoing cardiac surgery are at risk for development of tachyarrhythmias, especially in the period during and immediately after surgical intervention. Preventing electrolyte disorders is thus an important goal of therapy in such patients. However, although levels of potassium are usually measured regularly in these patients, other electrolytes such as magnesium, phosphate and calcium are measured far less frequently. We hypothesized that patients undergoing cardiac surgical procedures might be at risk for electrolyte depletion, and we therefore conducted the present study to assess electrolyte levels in such patients.

Methods

Levels of magnesium, phosphate, potassium, calcium and sodium were measured in 500 consecutive patients undergoing various cardiac surgical procedures who required extracorporeal circulation (group 1). A total of 250 patients admitted to the intensive care unit following other major surgical procedures served as control individuals (group 2). Urine electrolyte excretion was measured in a subgroup of 50 patients in both groups.

Results

All cardiac patients received 1 l cardioplegia solution containing 16 mmol potassium and 16 mmol magnesium. In addition, intravenous potassium supplementation was greater in cardiac surgery patients (mean ± standard error: 10.2 ± 4.8 mmol/hour in cardiac surgery patients versus 1.3 ± 1.0 in control individuals; P < 0.01), and most (76% versus 2%; P < 0.01) received one or more doses of magnesium (on average 2.1 g) for clinical reasons, mostly intraoperative arrhythmia. Despite these differences in supplementation, electrolyte levels decreased significantly in cardiac surgery patients, most of whom (88% of cardiac surgery patients versus 20% of control individuals; P < 0.001) met criteria for clinical deficiency in one or more electrolytes. Electrolyte levels were as follows (mmol/l [mean ± standard error]; cardiac patients versus control individuals): phosphate 0.43 ± 0.22 versus 0.92 ± 0.32 (P < 0.001); magnesium 0.62 ± 0.24 versus 0.95 ± 0.27 (P < 0.001); calcium 1.96 ± 0.41 versus 2.12 ± 0.33 (P < 0.001); and potassium 3.6 ± 0.70 versus 3.9 ± 0.63 (P < 0.01). Magnesium levels in patients who had not received supplementation were 0.47 ± 0.16 mmol/l in group 1 and 0.95 ± 0.26 mmol/l in group 2 (P < 0.001). Urinary excretion of potassium, magnesium and phosphate was high in group 1 (data not shown), but this alone could not completely account for the observed electrolyte depletion.

Conclusion

Patients undergoing cardiac surgery with extracorporeal circulation are at high risk for electrolyte depletion, despite supplementation of some electrolytes, such as potassium. The probable mechanism is a combination of increased urinary excretion and intracellular shift induced by a combination of extracorporeal circulation and decreased body temperature during surgery (hypothermia induced diuresis). Our findings may partly explain the high risk of tachyarrhythmia in patients who have undergone cardiac surgery. Prophylactic supplementation of potassium, magnesium and phosphate should be seriously considered in all patients undergoing cardiac surgical procedures, both during surgery and in the immediate postoperative period. Levels of these electrolytes should be monitored frequently in such patients.     

Saccharomyces boulardii Inhibits Water and Electrolytes Changes Induced by Castor Oil in the Rat Colon

The biotherapeutic agent Saccharomyces boulardii has been shown to inhibit castor oil-induced diarrhoea in rats. The present study investigated the mechanism(s) of this antidiarrhoeal effect in terms of water and electrolyte (sodium, potassium and chloride) changes using two rat models. A single oral dose of S. boulardii of up to 12 × 10¹⁰ CFU/kg of viable cells did not inhibit castor oil-induced fluid secretion in the enteropooling model. However, the yeast dose dependently reduced castor oil induced fluid secretion into the colon, with a significant protection at 12 × 10¹⁰ CFU/kg. In this model, castor oil reversed net sodium and chloride absorption into net secretion, and increased net potassium secretion into the lumen. Single pre-treatment with S. boulardii at 4 and 12 × 10¹⁰ CFU/kg dose dependently decreased these electrolyte changes. In conclusion, S. boulardii possesses potent anti-secretory properties versus water and electrolyte secretion induced by castor oil in the rat colon.     

Giant reversible,facet-dependent,structural changes in a correlated-electron insulator induced by ionic liquid gating

The use of electric fields to alter the conductivity of correlated electron oxides is a powerful tool to probe their fundamental nature as well as for the possibility of developing novel electronic devices. Vanadium dioxide (VO₂) is an archetypical correlated electron system that displays a temperature-controlled insulating to metal phase transition near room temperature. Recently, ionic liquid gating, which allows for very high electric fields, has been shown to induce a metallic state to low temperatures in the insulating phase of epitaxially grown thin films of VO₂. Surprisingly, the entire film becomes electrically conducting. Here, we show, from in situ synchrotron X-ray diffraction and absorption experiments, that the whole film undergoes giant, structural changes on gating in which the lattice expands by up to ∼3% near room temperature, in contrast to the 10 times smaller (∼0.3%) contraction when the system is thermally metallized. Remarkably, these structural changes are fully reversible on reverse gating. Moreover, we find these structural changes and the concomitant metallization are highly dependent on the VO₂ crystal facet, which we relate to the ease of electric-field–induced motion of oxygen ions along chains of edge-sharing VO₆ octahedra that exist along the (rutile) c axis.The use of electric fields to influence the transport properties of various materials by electrostatic injection of charge at an interface is the foundation of much of modern day electronics (1). Using a three-terminal field-effect transistor geometry, the magnitude of the electric fields provided by conventional gate dielectrics is limited by their dielectric properties. Much higher electric fields are possible by replacing the conventional gate material with an ionic liquid. Consequently, much higher electrostatically induced charge densities are possible, leading to the control or creation of novel metallic (2–3) and superconducting phases (4–7). Materials that are insulating by virtue of strong electron–electron correlations, namely Mott–Hubbard and charge-transfer insulators (8), are anticipated to be particularly sensitive to the injection of small numbers of carriers that could result in their metallization (9–11). Often these materials exhibit a thermally driven insulator to metal transition: one of these, VO₂, exhibits such a transition near room temperature (12, 13) and, for this reason, has been extensively studied (14–16). In VO₂ the metal to insulator transition (MIT) is accompanied by a structural phase transition (SPT) in which the monoclinic insulating phase transforms to a rutile metallic phase (17). Recently, both Nakano et al. (18) and Jeong et al. (19) showed that ionic liquid (IL) gating of thin films of VO₂ results in the suppression of the MIT to temperatures below ∼10 K and, moreover, that the entire film becomes metallic even though gating takes place at the top surface of the film in contact with the IL. However, whereas Nakano et al. (18) claimed the metallization phenomenon was a direct result of electrostatic carrier injection, Jeong et al. (19) presented clear evidence that the metallic state was rather induced by the electric-field–induced migration of oxygen from the film into the IL. An important question is whether the IL gating results in a structural phase transition, as supposed by Nakano et al. (18), or whether the initially insulating film remains in the monoclinic phase and the metallization results rather from the formation of oxygen vacancies (19). Here, we show, using in situ X-ray diffraction and absorption, that IL gating induces massive, reversible structural changes in which the VO₂ (001) film expands and contracts along its thickness by up to 3%, but that the film remains in the monoclinic phase. Furthermore, we identify a remarkable dependence of the IL gating phenomenon on the crystal facet of the VO₂ films. Whereas the (001) and (101) facets exhibit similar IL gate-induced metallization, almost no effect is observed for films grown with (100) and (110) facets. Because there are open channels in the VO₂ crystal structure along the rutile c axis, we associate the IL gating phenomenon with the ease of migration of oxygen along these channels under the influence of electric field. Previously, clear evidence for the formation and refilling of oxygen vacancies under ionic liquid gating of VO₂ (001) has been reported (19).The facet-dependent IL-induced metallization and associated structural changes of VO₂ were studied using two types of devices shown in Fig. 1 A and B, respectively. We label these devices as type T and X, respectively. In Fig. 1A a typical device type T with a channel area of 200 × 20 µm² defined by optical lithography is shown (see Methods for details). The channel conductance is measured using the source (S) and drain (D) contacts that are shown in the figure. A drop of the IL (∼100 nl) fully covers the channel and a significant part of the lateral gate electrode (19). Such devices T are suitable for detailed transport studies as a function of temperature and environment. Fig. 1B shows a cell (20) that was specially designed for in situ synchrotron-based X-ray measurements. Device X, used in this cell, is much larger than that of Fig. 1A and indeed is almost as large as the substrate itself (1 × 1 cm²) with S and D gold contacts, defined by shadow masks, along opposite edges of the substrate. The device and the gate electrode, which is formed from a coiled Au wire that surrounds the device, are immersed in ∼2 mL of IL which is introduced through Teflon tubes and which is contained by a 7.5-µm-thick Kapton sheet, sealed with Viton O-rings, that allows for transmission of the incident and diffracted X-ray beams and fluorescent X-rays. The cell is attached to a four-circle X-ray goniometer for the X-ray diffraction studies. Incorporated within the cell is a heater and a Peltier cooler that allows for operation at temperatures ranging from ∼250 K to ∼400 K. Pulsed laser deposition was used to deposit 10-nm-thick VO₂ films with four different crystal facets, (001), (101), (100), and (110) on single-crystalline substrates of TiO₂ with the same respective crystal orientations, and 20-nm-thick VO₂ (001) films on Al₂O₃(101¯0)(see Methods for details).Open in a separate windowFig. 1.Two different types of ionic liquid devices and facet dependence of gating effect. (A) Optical image of a device with a droplet of HMIM-TFSI with channel size of 200 × 20 µm². (B) Optical image of an ionic liquid device for in situ X-ray measurement. The entire film surface (10 × 10-mm² area) is covered with ionic liquid surrounded by a Au wire used as a gate electrode. Source–drain (Top) and gate (Bottom) current versus V_G for small size device (C) and large size device (D) fabricated from VO₂ films grown on TiO₂ substrates of different orientations. Gate voltages were swept at a rate of 3 mV/s (0.3 mV/s for D) and source–drain voltage (V_SD) of 100 mV (300 mV for D) is applied.Fig. 1 C and D compares the gate voltage (V_G) dependence of the source–drain current I_SD and the gate current I_G at 270 K for devices X and T. Initially the devices are in the insulating phase but above a certain threshold gate voltage I_SD increases substantially. When V_G is decreased to zero the devices remain conducting and revert back to their original state only when reverse gated by applying a negative voltage. I_G remains below 5 nA for all V_G for device T. For device X, I_G is much larger but only because of the much larger gated area: the leakage current per unit area of the gated VO₂ is similar for both devices (see SI Appendix for a detailed comparison). In the fully gated state, device T is metallic to low temperatures as shown earlier (19) but device X was only measured to 250 K, due to limitations of the X-ray cell, where it remained metallic. An important result is the dramatic dependence of the IL gating on the VO₂ crystal facet, as is clearly shown in Fig. 1 C and D.X-ray diffraction θ–2θ curves from a VO₂ (001) device X in the insulating phase and the thermally induced metallic phase are shown in Fig. 2A. The unit cell (all peaks are indexed throughout the paper with respect to the rutile unit cell, for simplicity) contracts along the c axis as evidenced by the shift of the VO₂ (002) peak to higher 2θ as VO₂ transforms from the monoclinic to a rutile phase. Fig. 2B shows a sequence of X-ray θ–2θ curves for the device in different gated states as V_G was systematically ramped in steps from 0 to +2.2 V to −2.2 V and back to zero. The X-ray data were collected after V_G was fixed at each step for 30 min. Fig. 2C shows the corresponding values of I_SD for these data. The gate voltage-induced increase in I_SD is ∼3 orders of magnitude. The X-ray data show very large shifts in the VO₂ (002) peak position which, however, are opposite to that seen for the temperature-driven MIT shown in Fig. 2A. The VO₂ (002) peak rather shifts to smaller 2θ values. This corresponds, as shown in Fig. 2D, to an expansion of the c-axis parameter in the fully gated metallic state by a factor which is 10 times larger than the contraction in the c-lattice parameter that is observed for the temperature-driven SPT. We note that the threshold voltages at which the lattice changes are observed appear to be smaller than that at which I_SD changes. We find that no structural changes are observed when the same experiment is carried out on a 10-nm-thick VO₂ film grown with a (110) facet on TiO₂(110). X-ray diffraction θ–2θ curves taken during gating at gate voltages of up to 2.8 V show no shift in the VO₂ (220) peak position nor any other changes in the X-ray diffraction curves. As shown in Fig. 1D there are similarly no changes in I_SD during gating up to V_G = 3 V.Open in a separate windowFig. 2.Structural changes of VO₂/TiO₂(001) by electrolyte gating as a function of gate voltages. (A) XRD patterns of insulating (red) phase at 270 K and metallic phase (black) at 300 K for 10-nm VO₂/TiO₂(001) with 12-keV photon energy. (B) XRD pattern for in situ X-ray measurements and (C) source–drain current (I_SD) versus gate voltage (V_G). Both XRD and I_SD were measured ∼30 min after V_G was applied. (D) c-axis lattice parameter extracted from B versus gate voltage. The error bars are from the nonlinear least-squares fitting algorithm and in many cases are smaller than the symbols.The structural changes that we find on gating VO₂ (001) are similar to those found by growing VO₂ (001) films of comparable thickness at lower oxygen pressures during pulsed laser deposition. Fig. 3A shows X-ray diffraction θ–2θ curves for a series of five samples, each ∼10 nm thick, prepared at oxygen pressures of 9, 7, 5, 3, and 1 mTorr. As the oxygen pressure is reduced the c-lattice parameter systematically increases, as shown in Fig. 3B. The MIT transition is systematically broadened and suppressed to low temperatures as the oxygen pressure is reduced (19). The c-lattice parameter expansion caused by the introduction of oxygen vacancies by modifying the film growth conditions are similar to those that IL gating induces, and the resulting metallization of the VO₂ films is comparable. We presume that the thickness oscillations in the θ–2θ curves from VO₂/TiO₂(001) in Fig. 2B that disappear on gating result from the loss of coherence in the film structure due to gating and the subsequent formation of oxygen vacancies.Open in a separate windowFig. 3.Crystal structure of oxygen-deficient and gated VO₂/TiO₂(001). Dependence of (A) XRD θ–2θ curves, and (B) c-lattice parameter and T_MIT on oxygen pressure during growth. (C) Reciprocal space maps of VO₂(202) peak versus oxygen pressure during film growth and comparison with those for the pristine and gated states of a device formed from a film grown at 9 mtorr. (D) Structure of the monoclinic phase of VO₂ looking along the <001> and <110> axes.The crystal facet of the VO₂ film is determined by epitaxial growth onto the respective facet of the TiO₂ substrate. This also results in clamping of the 10-nm-thick VO₂ films to the corresponding TiO₂ lattices by coherent strain such that their in-plane unit cell parameters are very similar. This is illustrated in Fig. 3C, which shows reciprocal lattice maps centered near TiO₂ (202) in the k = 0 plane for the five films prepared in different oxygen ambients in Fig. 3A. The maps show along the [20l] direction a very sharp, intense TiO₂ (202) peak together with a weaker and broader VO₂ (202) peak and associated Kiessig fringes (21). The VO₂ (202) peak systematically shifts to lower l as the oxygen pressure is reduced. Along the [h02] direction, by contrast, the VO₂ and TiO₂ peaks have similar narrow widths that indicate in-plane clamping of the VO₂ lattice to that of the TiO₂ substrate. Thus, during IL gating it is anticipated that only the out-of-plane VO₂ lattice parameter can be significantly changed. This is confirmed in the reciprocal space map for a sample that was gated at V_G = 3 V for 10 h and the IL removed before the measurement using a laboratory X-ray source.The clamping of the VO₂ lattice to that of the TiO₂ lattice could offer an explanation for the lack of any significant IL gating response for facets of VO₂ for which the c axis lies in plane. It could be that to remove significant amounts of oxygen the lattice needs to expand along the c direction. It is along the rutile c direction that the structure comprises one-dimensional chains of edge-sharing VO₆ octahedra that allow for the expansion and contraction of the VO₂ lattice during IL gating (Fig. 3D).To inspect the local environment of V we performed in situ X-ray absorption spectroscopy (XAS) at the V K edge using VO₂ (001) films grown on Al₂O₃(101¯0)rather than TiO₂ to avoid the otherwise significant fluorescence from Ti in the substrate. The sample was gated and the XAS data were measured at ambient temperature well below the MIT of the pristine film. The X-ray absorption near-edge spectra (XANES) are shown in Fig. 4A for a pristine sample and the same sample after gating (V_G = 3 V, 1 h) to a conducting state. The XANES data remain largely unchanged with two exceptions. Firstly, there is a small shift in the position of the inflection point of the V 1s→3d preedge transition and a small decrease in the intensity of the preedge peak that suggest a reduction in the valence state of the V ions [by ∼0.2 electrons per V (22)]. The decrease in the intensity of this preedge feature is also consistent with a decrease in the degree of distortion of the VO₆ octahedra (22). Secondly, there is a small shift to lower photon energies in the position of the main V K edge and the white line (V1s → V4p transition) at this edge which is also consistent with a reduced V valence on gating (22). A change in V valence was previously observed in X-ray photoelectron spectroscopy measurements performed on electrolyte-gated VO₂ that suggested the formation of oxygen vacancies on gating (19).Open in a separate windowFig. 4.XAS of VO₂/Al₂O₃(101¯0). (A) Vanadium K-edge XANES for a pristine and gated device X. (B and C) χ(R) curves for the data and corresponding fits. The individual contributions to these fits from respective V–O and V–V shells are shown (inverted) in the bottom halves of B and C. The experimental data for the pristine and gated states are shown in blue and red, respectively; the fits to these data are shown in green; the differences between the experimental data and fits are shown in magenta; the contributions from V–O shells are shown in purple; the contributions from V–V shells along the dimer axis are brown and perpendicular to the dimer axis are dark yellow. The brown horizontal lines in B and C are aids to the eye, showing the degree of dimerization, namely, the difference between the intra- and inter-V–V dimer distances. The solid and dashed curves are the moduli and real parts of the Fourier transform of the EXAFS data and the fits, respectively. (D) Table of fitted V–O and V–V bond distances.Much larger changes are observed in the extended X-ray absorption fine structure (EXAFS) (23), χ(k), that is most readily seen in its Fourier transform (FT), namely, χ(R) = FT(k³ χ(k)) (23), that is presented in Fig. 4 B and C. Detailed information on the types of locally ordered neighbor shells and their metrical parameters was obtained by nonlinear least-squares curve fits using calculated amplitudes and phases (24). The k³-weighted data were fit for k varying from 2.6 to 10.3 Å^–1 so that shells are distinguishable only if separated by more than ∼0.15 Å. The spectra were well fit (Fig. 4 B and C) with a limited number of shells relative to the crystal structure (SI Appendix). The distances found for the pristine samples are consistent with the monoclinic phase of VO₂ below its MIT in which the shorter V–V distances that correspond to those in the (rutile) c direction that is normal to the film plane are split because of the dimerization of the V–V atoms along this direction. In the pristine sample these V–V distances of 2.61 and 3.03 Å differ by 0.42 Å, whereas in the gated sample these distances become 2.94 and 3.16 Å and differ by only 0.22 Å. Note that the almost complete loss of the peak in the χ(R) spectra near R−ϕ = 2.0 Å on gating is not because of a radical change in the V–V chain ordering and departure from the V–V dimerized monoclinic structure, but is because the decreased separation between the short and long dimer V–V pairs causes their individual EXAFS waves to destructively interfere, reducing their combined amplitude in the FT. Thus, a crucial result is that the V–V dimerization, although reduced, is nevertheless retained in the gated state. Moreover, the average V–V distance in the c direction normal to the film planes increases by a much larger amount than is found by diffraction that could indicate rotation of the VO₆ octahedra. On the other hand, the V–V distance within the ab plane (∼3.5 Å) changes little on gating (Fig. 4D), suggesting that the structure in the plane is largely unaffected, consistent with the X-ray diffraction data in Fig. 3C.Our in situ X-ray diffraction (XRD) and XAS measurements clearly indicate a giant expansion of the VO₂ unit cell that is clearly inconsistent with the formation of the rutile phase that the thermally induced metallic phase exhibits. Moreover, we find these reversible structural changes only in films in which channels formed from chains of edge-sharing VO₆ octahedra do not lie in the plane of the films, strongly suggesting that these channels are the paths along which the gate-induced oxygen migration takes place. These gate-induced changes in structure and conductivity are likely to be common to many ionic liquid gated systems, opening the way to a potential future of “liquid electronics.”     

Ionic imbalance,in addition to molecular crowding,abates cytoskeletal dynamics and vesicle motility during hypertonic stress

Cell volume homeostasis is vital for the maintenance of optimal protein density and cellular function. Numerous mammalian cell types are routinely exposed to acute hypertonic challenge and shrink. Molecular crowding modifies biochemical reaction rates and decreases macromolecule diffusion. Cell volume is restored rapidly by ion influx but at the expense of elevated intracellular sodium and chloride levels that persist long after challenge. Although recent studies have highlighted the role of molecular crowding on the effects of hypertonicity, the effects of ionic imbalance on cellular trafficking dynamics in living cells are largely unexplored. By tracking distinct fluorescently labeled endosome/vesicle populations by live-cell imaging, we show that vesicle motility is reduced dramatically in a variety of cell types at the onset of hypertonic challenge. Live-cell imaging of actin and tubulin revealed similar arrested microfilament motility upon challenge. Vesicle motility recovered long after cell volume, a process that required functional regulatory volume increase and was accelerated by a return of extracellular osmolality to isosmotic levels. This delay suggests that, although volume-induced molecular crowding contributes to trafficking defects, it alone cannot explain the observed effects. Using fluorescent indicators and FRET-based probes, we found that intracellular ATP abundance and mitochondrial potential were reduced by hypertonicity and recovered after longer periods of time. Similar to the effects of osmotic challenge, isovolumetric elevation of intracellular chloride concentration by ionophores transiently decreased ATP production by mitochondria and abated microfilament and vesicle motility. These data illustrate how perturbed ionic balance, in addition to molecular crowding, affects membrane trafficking.A basic challenge for all animal cells is to maintain constant volume and intracellular electrolyte composition (1, 2). K⁺ is the principal intracellular cation, and Na⁺ is extruded from the cell interior. Cellular concentration of these ions is controlled by energy-consuming transport mechanisms, primarily the Na⁺/K⁺-ATPase. Cl⁻ is a major anion in the extracellular milieu that is maintained at relatively low concentrations (5–40 mM) within the cytosol by a variety of plasma membrane transporters, including the CFTR and members of the chloride channel, voltage-senstitive (ClC) family of Cl⁻ channels (3). Together, these ions not only maintain cell volume and a biologically compatible intracellular milieu but also allow passive diffusional movement of ions down their electrochemical gradients that is central to cell function, from general cell division to the more specialized processes of secretion and contractibility. Various types of environmental challenge lead to electrolyte imbalance, as illustrated by variations of environmental tonicity that immediately alter cell volume and intracellular ion composition (4–6). Cells shrink rapidly in hypertonic environments and swell in hypotonic environments. Cell volume is reestablished quickly—within minutes—in mammalian cells by salt (Na⁺ and Cl⁻) influx (in response to hypertonic stress) or K⁺ efflux (in response to hypotonic stress), but such changes occur at the expense of electrolyte imbalance. Prechallenge intracellular ion composition is reestablished gradually over time (hours to days) by readjusting the intracellular levels of nonionic solutes, principally amino acids and other organic compounds (2, 6) that have far fewer effects on enzyme activity.Numerous organisms across the animal kingdom are routinely exposed to fast variations of environmental osmolality. In mammals, many cell types must deal with hypertonic challenge as part of their daily function. These include blood cells passing through the renal medulla and intestinal epithelial cells after food ingestion (7). Moreover, hypertonic fluids are routinely administered to treat disorders such as hyponatremia, cystic fibrosis, and hemorrhagic shock (8–10). Hypertonicity affects a wide range of cellular processes. For example, it causes DNA damage (11) and protein damage and aggregation (5, 12), promotes autophagy (13), and leads to apoptosis when challenge is overwhelming (4). Membrane trafficking is a major process affected by hypertonicity that probably contributes significantly to the change incurred upon challenge. Indeed, we and others have observed that endocytosis, exocytosis, and vesicular trafficking are reduced from the onset of challenge, and that the reduction can persist hours after challenge (14–19). However, how immediate changes in the cell’s biophysical parameters influence these events is unclear. By inducing cell shrinkage, hypertonicity increases intracellular component density and molecular crowding (20). Increased crowding of macromolecules and organelles by water efflux results in cytoplasm stiffening (21), protein misfolding and aggregation (12), and reduces protein diffusion (22). Therefore it is reasonable to suppose that molecular crowding may interfere with at least some trafficking events. On the other hand, because osmotically induced cell shrinkage is invariably accompanied by increased intracellular salt concentration, the relative contribution of each occurrence on membrane trafficking is unclear.High levels of intracellular salt after hypertonic challenge may perturb a number of parameters that collectively affect membrane trafficking. Microtubules (MT) and actin filaments play paramount roles in membrane trafficking. Their dynamic nature creates forces that help move cargo, and they supply “tracks” for long-range delivery of cargo (23). A key feature of MT biology is dynamic instability, so that tubules continuously switch between episodes of steady growth and rapid shrinkage (24), allowing the cell to probe the cytoplasm constantly and adapt quickly to environmental change. A hallmark feature of hypertonicity is that it induces actin cytoskeleton reorganization (4), and we recently have shown that it also induces fast MT remodeling (13). Because the dynamics of microfilament assembly/disassembly are sensitive to ionic conditions (25, 26), a sudden increase in intracellular salt could alter their dynamics and impinge on membrane trafficking. High levels of intracellular salt also could affect membrane trafficking by modulating available energy. Increased ion concentration decreases mitochondrial matrix volume and disrupts key parameters of the respiratory chain, as shown in isolated mitochondria (27, 28) and as predicted by mathematical models of mitochondrial bioenergetics (29). Thus, hypertonicity conceivably could affect membrane trafficking by decreasing ATP production by mitochondria. However, the influence of hypertonicity on mitochondrial function in intact cells has been investigated mostly in the context of apoptosis induced by severe hypertonic stress, which disrupts mitochondrial potential (30–32).In the present study, we examined the effects of molecular crowding, high intracellular Cl⁻ concentration [Cl⁻]_i, microfilament remodeling, and altered mitochondrial function by hypertonicity on vesicle motility. We show that strong but sustainable hypertonic challenge to mammalian cells immediately halts both microfilament motility and the motility of a wide variety of endosome/vesicle subpopulations. We demonstrate that vesicle motility recovers significantly more slowly than cell volume and that an isovolumetric increase in [Cl⁻]_i by ionophores triggers mitochondrial depolarization and decreases ATP levels, microfilament dynamics, and vesicle motility. Thus, these data illustrate how intracellular ionic imbalance, in addition to molecular crowding, affects membrane trafficking and cell function.     

急性胰腺炎的电解质酸碱失衡及TPN治疗

本文报道25例急性出血坏死性胰腺炎（ANP），30例急性水肿性胰腺炎（AEP）的电解质与酸碱失调分析结果，以ANP表现显著，有低钾，低钠，低氯，低钙，低磷，代酸与代酸呼碱，低氧血症，低蛋白血症的表现,与AEP比较有显著性差异（P＜0．01）。16例ANP型采用全肠外营养（TPN）治疗，其中13例存活，与过去未用TPN治疗22例，14例死亡有显著差异（P＜0．01）。作者认为TPN协同治疗ANP患者，对于提供营养，抑胰分泌，促进胰腺组织修复，纠正水盐代谢紊乱，防止并发症与提高存活率有重要意义。对TPN的用法及热原供给作了简要讨论。     

排钾-保钾结合排酸-保酸利尿方案对肺心病的探讨

目的　评价排钾 -保钾结合排酸 -保酸利尿方案对肺源性心脏病的优越性。方法　 191例肺源性心脏病例随机分为 A组 (42例 )、B组 (6 3例 )、C组 (86例 )。A组予呋塞米 2 0 mg(或氢氯噻嗪 5 0 mg) ,每日一次 ;B组予呋塞米 2 0 mg(或氢氯噻嗪 5 0 mg)、螺内酯 4 0 mg,每日各一次 ;C组予呋塞米 2 0 mg(或氢氯噻 5 0 mg)、螺内酯 4 0mg、乙酰唑胺 2 5 0 mg,每日各一次。对比三组治疗前后 K 、Na 、Cl- 、p H值、HCO3- 、SBE、Pa CO2 等指标的变化及肺性脑病的发生情况。结果　治疗 7日后 ,A组 K 、Na 、Cl 均显著降低 (P<0 .0 1) ,p H、HCO- 3、SBE和 Pa CO2 均显著升高 (P<0 .0 1) ;B组 Na 、Cl- 均显著降低 (P<0 .0 1) ,p H、HCO3- 、SBE和 Pa CO2 均显著升高 (P<0 .0 1) ,而K 变化不显著 (P>0 .0 5 ) ;C组虽 Na 仍有显著降低 (P<0 .0 5 ) ,但 K 、Cl- 、p H、HCO3- 、SBE、Pa CO2 变化均不显著 (P>0 .0 5 )。C组肺性脑病的发生率 (0 % )比 A组 (9.5 % )、B组 (12 .7% )显著减少 (P<0 .0 5～ 0 .0 1)。结论　排钾-保钾结合排酸 -保酸利尿方案对维持肺心病的电解质和酸碱平衡及预防肺性脑病的发生有明显优越性。     

不同膨宫压力对宫腔镜电切术中患者中心静脉压和血浆电解质变化的影响

目的:观察宫腔镜电切术中不同膨宫压力对患者中心静脉压力(CVP)和血浆电解质变化的影响,为避免TURS的发生提供依据。方法:根据术中压力不同将80例宫腔镜电切术按随机方式分为H组(膨宫压力150 mm Hg)和L组(膨宫压力100 mm Hg)两组,膨宫介质均为生理盐水,观察患者入室时(T0)、手术开始后10 min(T1)、术毕(T2)时间段患者CVP和各种电解质血生化指标。结果:两组间血浆电解质指标在监测的各时间点无统计学差异(P>0.05),CVP数值H组比L组上升更加显著,有明显的统计学差异(P<0.05)。结论:在宫腔镜电切术中CVP动态监测对TURS早期诊断有一定的临床意义,使用高膨宫压力的宫腔镜电切术,CVP的升高更为明显,术者须谨慎增加膨宫压,以避免TURS的发生。     

老年人饮食摄入电解质及微量元素与便秘伴随症状的相关性

目的探讨老年人饮食中摄入的电解质及微量元素与便秘伴随症状的相关性。方法选择某于休所中自愿参加的65岁以上老年人,共51人,进行饮食和排便相关情况调查,并留取粪便标本进行电解质及微量元素测定。结果饮食中的钙离子含量与排便全程时间、排便用力指数及排便不净存在显著的正相关;粪便内钙的含量与饮食中钙的含量存在显著的正相关;20位便秘者日均摄入钙离子、钾离子含量显著高于31位非便秘者;且粪便标本中的钙离子含量与排便用力程度及排便时间长存在显著正相关。结论为防治便秘,老年人应摄入平衡饮食,不应过量摄入高钙饮食。     

HPLC测定混合糖电解质注射液中果糖、葡萄糖和木糖醇的含量

目的 建立混合糖电解质注射液中果糖、葡萄糖和木糖醇的含量测定方法。方法 色谱柱：Waters Sugar Pak I(300 mm×6.5 mm);流动相：水;流速：0.5 mL·min^-1;示差折光检测器。结果 果糖、葡萄糖和木糖醇峰分离度良好;果糖的线性范围为20~100 μg(r=0.999 9);平均回收率为99.53%,RSD=0.81%(n=9);葡萄糖的线性范围为40~200 μg(r=0.999 7);平均回收率为99.75%,RSD=0.47%(n=9);木糖醇的线性范围为10~50 μg(r=0.999 7);平均回收率为99.78%,RSD=1.02%(n=9)。结论 本方法简便、准确,可用于混合糖电解质注射液中果糖、葡萄糖和木糖醇的含量测定。     

聚乙二醇电解质散剂联合低剂量硫酸镁与西甲硅油在结肠镜检查前肠道准备中的应用

目的：探讨聚乙二醇电解质散剂（PEG）中加入低剂量硫酸镁和西甲硅油在结肠镜检查前肠道准备中的应用和观察。方法：150例行结肠镜检查的患者,按不同肠道准备方法随机分为三组：A组：PEG;B组：PEG＋低剂量硫酸镁;C组：PEG＋低剂量硫酸镁＋西甲硅油,每组50例。比较不同方法的有效性、安全性及耐受性。结果：所有患者均完成肠道准备和全结肠镜检查。肠道清洁度比较,C组、B组均优于A组,差异有统计学意义（96％vs 92％vs 72％,χ2＝6．78,χ2＝10．71,均P＜0．05）。肠道内气泡产生率比较,C组优于B组和A组,差异有统计学意义（χ2＝6．35,χ2＝4．33,均P＜0．05）。三种肠道准备方法的不良反应、药物耐受情况差异均无统计学意义（P＞0．05）。结论：聚乙二醇电解质散剂联合低剂量硫酸镁和西甲硅油用于结肠镜检查前的肠道准备,有效性较高,安全性和耐受性值得进一步探讨。