Citrate- vs. acetate-based dialysate in bicarbonate haemodialysis: consequences on haemodynamics, coagulation, acid-base status, and electrolytes.

BACKGROUND: A concentrate for bicarbonate haemodialysis acidified with citrate instead of acetate has been marketed in recent years. The small amount of citrate used (one-fifth of the concentration adopted in regional anticoagulation) protects against intradialyser clotting while minimally affecting the calcium concentration. The aim of this study was to compare the impact of citrate- and acetate-based dialysates on systemic haemodynamics, coagulation, acid-base status, calcium balance and dialysis efficiency. METHODS: In 25 patients who underwent a total of 375 dialysis sessions, an acetate dialysate (A) was compared with a citrate dialysate with (C+) or without (C) calcium supplementation (0.25 mmol/L) in a randomised single-blind cross-over study. Systemic haemodynamics were evaluated using pulse-wave analysis. Coagulation, acid-base status, calcium balance and dialysis efficiency were assessed using standard biochemical markers. RESULTS: Patients receiving the citrate dialysate had significantly lower systolic blood pressure (BP) (-4.3 mmHg, p < 0.01) and peripheral resistances (PR) (-51 dyne.sec.cm-5, p < 0.001) while stroke volume was not increased. In hypertensive patients there was a substantial reduction in BP (-7.8 mmHg, p < 0.01). With the C+ dialysate the BP gap was less pronounced but the reduction in PR was even greater (-226 dyne.sec.cm-5, p < 0.001). Analyses of the fluctuations in PR and of subjective tolerance suggested improved haemodynamic stability with the citrate dialysate. Furthermore, an increase in pre-dialysis bicarbonate and a decrease in pre-dialysis BUN, post-dialysis phosphate and ionised calcium were noted. Systemic coagulation activation was not influenced by citrate. CONCLUSION: The positive impact on dialysis efficiency, acid-base status and haemodynamics, as well as the subjective tolerance, together indicate that citrate dialysate can significantly contribute to improving haemodialysis in selected patients.

Erosion and channel change as factors of landslides and valley formation in Champlain sea clays: The Chacoura river, Quebec, Canada

The Champlain Sea clays of Eastern Canada are incised by numerous rivers. Their slopes have been modified by landslides: on the Chacoura River near Trois-Rivières (Quebec), several large landslide scars, more or less recent, are visible. The role of erosion (channel incision, lateral channel migration and erosion of slopes due to agricultural drainage) as a trigger of these landslides is important. The aim of this study is to understand how erosion and landslides are related to valley development. From a detailed analysis of aerial photographs and DEMs, a map of the phenomena has been drawn by identifying various elements such as landslides, limits of the slope, position of the channel, and the area covered by forest. It is shown that channel change and erosion are strongly linked to landslides by the fact that they change the bank morphology in an unstable way. A slide in itself is a natural way for the slope to achieve stability. But when it occurs in a stream, it creates a disturbance to the stream flow enhancing local erosion which may change the river path and generate more erosion downstream or upstream resulting in more slides. Cross-valley sections and a longitudinal profile show that landslides are a major factor of valley formation. It appears that the upper part of the Chacoura River valley is still unaffected by landslides and has V-shaped sections. The lower part has been subject to intense erosion and many landslide scars can be seen. This shows that the valley morphology is transient, and that future activity is more likely to occur in the upper part of the river. Therefore the identification of areas prone to erosion will help determine the possible location of future large landslides just like the ones that occurred in the lower part.

Assessing catchment-scale erosion and yields of suspended solids from improved temperate grassland.

This paper quantifies the yields of suspended solids (SS) from a headwater catchment managed as improved temperate grassland, providing the first direct, catchment-scale evidence of the rates of erosion from this land-use in the UK and assessing the threat posed to aquatic ecosystems. High-resolution monitoring of catchment hydrology and the concentrations of SS and volatile organic matter (VOM) were carried out in the first-order channel of the Den Brook headwater catchment in Devon (UK) during the 2006-2007 hydrological season. The widely used 'rating curve' (discharge-concentration) approach was employed to estimate yields of SS, but as demonstrated by previous researchers, this study showed that discharge is a poor predictor of SS concentrations and therefore any yields estimated from this technique are likely to be highly uncertain. Nevertheless, for the purpose of providing estimates of yields that are comparable to previous studies on other land uses/sources, this technique was adopted albeit in an uncertainty-based framework. The findings suggest that contrary to the common perception, grasslands can be erosive landscapes with SS yields from this catchment estimated to be between 0.54 and 1.21 t ha(-1) y(-1). In terms of on-site erosion problems, this rate of erosion does not significantly exceed the commonly used 'tolerable' threshold in the UK ( approximately 1 t ha(-1) y(-1)). In terms of off-site erosion problems, it is argued here that the conventional expression of SS yield as a bulk annual figure has little relevance to the water quality and ecological status of surface waters and therefore an alternative technique (the concentration-frequency curve) is developed within this paper for the specific purpose of assessing the ecological threat posed by the delivery of SS into surface waters. This technique illustrates that concentrations of SS recorded at the catchment outlet frequently exceed the water quality guidelines, such as those of the EU Freshwater Fisheries Directive (78/659/EC), and pose a serious threat to aquatic organisms. It is suggested that failure to recognise improved temperate grasslands as a potential source of particulate material could result in the non-compliance of surface waters to water quality guidelines, deterioration of ecological status and failure of water quality remediation measures.

Skull base chordomas: presentation of six cases and review of the literature.

Chordomas are uncommon tumours occuring from remnants of the notochord. They are mainly localized in the sacrococcygium, the spine and the skull base. We focused our study on skull base chordomas and reviewed 531 published cases and 6 cases diagnosed in our institution. The six cases diagnosed at our hospital are described with a special mention of a unique case presenting with meningitis. Clinical features, radiology, histopathology and survival with different treatments are reviewed. Skull base chordomas can occur at any age and are slightly more frequent in males. Patients complain most often of diplopia and headaches. Abducens nerve palsy is the commonest neurological finding. Radiological examination should include both CT-scan which shows extensive osteolysis, calcifications and contrast enhancement and MRI for topographical definition. Metastases rarely occur. Treatment remains controversial but combined surgery and radiotherapy is the best treatment with a 5 year survival rate of 75%.

Stratigraphy and palaeoenvironment of Early Jurassic dinosaur-bearing volcaniclastic deposits from Toundoute (Province of Ouarzazate, Haut-Atlas, Morocco)

The Early Jurassic dinosaur site of Toundoute which yielded the basal sauropod Tazoudasaurus naimi is examined in the light of its stratigraphic, sedimentological and palaeoenvironmental context. A thin succession of Early Liassic marine carbonates (probably Hettangian-Sinemurian in age) is continuously overlain by continental beds with dinosaurs. These latter are assumed to be of Middle to Late Liassic age. The continental deposits include a large part of volcanoclastics, different from the Triassic basalts. The Jurassic volcanoclastics originated from an unknown but obviously close eruption centre. The continental sediments (channels and flood plain) were deposited under tropical climate conditions with alternating humid and dry episodes. The bones occur as isolated or partly articulated elements (parts of carcasses). The two bone-beds are related to typical mud-flows. This type of transport protected the bones from erosion, and favoured their burying and fossilization.

Weathering and the mobility of phosphorus in the catchments and forefields of the Rhone and Oberaar glaciers, central Switzerland: Implications for the global phosphorus cycle on glacial-interglacial timescales

In this study we evaluate the dynamics of the biophile element phosphorus (P) in the catchment and proglacial areas of the Rhone and Oberaar glaciers (central Switzerland). We analysed erosion and dissolution rates of P-containing minerals in the subglacial environment by sampling water and suspended sediment in glacier outlets during three ablation and two accumulation seasons. We also quantified biogeochemical weathering rates of detrital P in proglacial sedimentary deposits using two chronosequences of samples of fresh, suspended, material obtained from the Oberaar and Rhone water outlets, Little-Ice-Age (LIA) moraines and Younger Dryas (YD) tills in each catchment. Subglacial P weathering is mainly a physical process and detrital P represents more than 99%, of the precipitation-corrected total P denudation flux (234 and 540 kg km(-2) yr(-1) for the Rhone and Oberaar catchments, respectively). The calculated detrital P flux rates are three to almost five times higher than the world average flux. The precipitation-corrected soluble reactive P (SRP) flux corresponds to 1.88-1.99 kg km(-2) yr(-1) (Rhone) and 2.12-2.44 kg km(-2) yr(-1) (Oberaar), respectively. These fluxes are comparable to those of tropical rivers draining transport-limited, tectonically inactive weathering areas. In order to evaluate the efficiency of detrital P weathering in the Rhone and Oberaar proglacial areas, we systematically graded apatite grains extracted from the chronosequence in each catchment relative to weathering-induced changes in their surface morphologies (grades 1-4). Fresh apatite grains are heavily indented and dissolution rounded (grade 1). LIA grains from two 0-10 cm deep moraine samples show extensive dissolution etching, similar to surface grains from the YD profile (mean grades 2.7, 3.5 and 3.5, respectively). In these proglacial deposits, the weathering front deepens progressively as a function of time due to biocorrosion in the evolving acidic pedosphere, with mechanical indentations on grains acting as sites of preferential dissolution. We also measured iron-bound, organic and detrital P concentrations in the chronosequence and show that organic and iron-bound P has almost completely replaced detrital P in the top layers of the YD profiles. Detrital P weathering rates are calculated as 3 10 and 280 kg km(-2) yr(-1) for LIA moraines and 10 kg km(-2) yr(-1) for YD tills. During the first 300 years of glacial sediment exposure P dissolution rates are shown to be approximately 70 times higher than the mean global dissolved P flux from ice-free continents. After 11.6 kyr the flux is 2.5 times the global mean. These data strengthen the argument for substantial changes in the global dissolved P flux on glacial-interglacial timescales. A crude extrapolation from the data described here suggests that the global dissolved P flux may increase by 40-45% during the first few hundred years of a deglaciation phase

Präoperative Azidose und Entwicklung von Säuglingen nach Operation angeborener Herzfehler Preoperative acidosis and infant development following surgery for congenital heart disease.

OBJECTIVE: Prenatal diagnosis has been shown to decrease pre-operative acidosis and might prevent the occurrence of disturbed developmental outcome. The aim of this study is to evaluate parameters for acidosis and their predictive value on developmental outcome in newborns with congenital heart disease. METHODS: A total of 117 patients requiring surgery for structural heart disease in the first 31 days of life were included. Diagnosis was established either pre- or postnatally. Preoperative values of lactate, pH and base excess levels were compared to the occurrence of disturbed developmental outcome, i.e. an underperformance of more than 10% on the P90 of a standardized Dutch developmental scale. Patients were divided into groups according to blood levels of acidosis parameters, using receiver operating characteristics curves to determine cut-off values for pH, base excess and lactate. RESULTS: No significant difference in developmental outcome was found using values for pH or base excess as a cut-off level. Preoperative lactate values exceeding 6.1 mmol/l resulted in a significant increase in impaired development compared to infants with a pre-operative lactate lower than 6.1 mmol/l: 40.9% vs 15.1% in (p=0.03). CONCLUSIONS: Pre-operative lactate values might have a prognostic value on developmental outcome in newborns with congenital heart disease. The limited prognostic value of pH can be explained by the fact that pH can be easily corrected, while lactate better reflects the total oxygen debt experienced by these patients.

Cruveilhier's legacy to skull base surgery: premise of an evidence-based neuropathology in the 19th century.

OBJECTIVES: Jean Cruveilhier has always been described as a pioneer in pathological anatomy. Almost nothing has been reported concerning his exceptional methodology allying pre-mortem clinical description and syndromic classification of neurological and neurosurgical diseases, and post-mortem meticulous dissections. Cruveilhier's methodology announced the birth of the anatomoclinical method built up by Jean-Martin Charcot and the neurological French school during the 19th century. The aim of our work is to extract the quintessence of Cruveilhier's contributions to skull base pathology through his cogent clinical descriptions coupled with exceptional lithographs of anterior skull base, suprasellar and cerebello-pontine angle tumors. METHODS: We reviewed the masterwork of Jean Cruveilhier on pathological anatomy and we selected the chapters dedicated to central nervous system pathologies, mainly skull base diseases. A systematic review was performed on Pubmed/Medline and Google Scholar using the keywords "Jean Cruveilhier", "Skull base pathology", "Anatomoclinical method". RESULTS: Among his descriptions, Cruveilhier dedicated large chapters to neurosurgical diseases including brain tumors, cerebrovascular pathologies, malformations of the central nervous system, hydrocephalus, brain infections and spinal cord compressions. CONCLUSION: This work emphasizes on the role of Jean Cruveilhier in the birth of the anatomoclinical method particularly in neuroscience during a 19th century rich of epistemological evolutions toward an evidence-based medicine, through the prism of Cruveilhier's contribution to skull base pathology.

Reconstruction of metal pollution and recent sedimentation processes in Havana Bay (Cuba): A tool for coastal ecosystem management.

Since 1998 the highly polluted Havana Bay ecosystem has been the subject of a mitigation program. In order to determine whether pollution-reduction strategies were effective, we have evaluated the historical trends of pollution recorded in sediments of the Bay. A sediment core was dated radiometrically using natural and artificial fallout radionuclides. An irregularity in the (210)Pb record was caused by an episode of accelerated sedimentation. This episode was dated to occur in 1982, a year coincident with the heaviest rains reported in Havana over the XX century. Peaks of mass accumulation rates (MAR) were associated with hurricanes and intensive rains. In the past 60 years, these maxima are related to strong El Niño periods, which are known to increase rainfall in the north Caribbean region. We observed a steady increase of pollution (mainly Pb, Zn, Sn, and Hg) since the beginning of the century to the mid 90s, with enrichment factors as high as 6. MAR and pollution decreased rapidly after the mid 90s, although some trace metal levels remain high. This reduction was due to the integrated coastal zone management program introduced in the late 90s, which dismissed catchment erosion and pollution.

α-Ketoglutarate regulates acid-base balance through an intrarenal paracrine mechanism.

Paracrine communication between different parts of the renal tubule is increasingly recognized as an important determinant of renal function. Previous studies have shown that changes in dietary acid-base load can reverse the direction of apical α-ketoglutarate (αKG) transport in the proximal tubule and Henle's loop from reabsorption (acid load) to secretion (base load). Here we show that the resulting changes in the luminal concentrations of αKG are sensed by the αKG receptor OXGR1 expressed in the type B and non-A-non-B intercalated cells of the connecting tubule (CNT) and the cortical collecting duct (CCD). The addition of 1 mM αKG to the tubular lumen strongly stimulated Cl--dependent HCO3- secretion and electroneutral transepithelial NaCl reabsorption in microperfused CCDs of wild-type mice but not Oxgr1-/- mice. Analysis of alkali-loaded mice revealed a significantly reduced ability of Oxgr1-/- mice to maintain acid-base balance. Collectively, these results demonstrate that OXGR1 is involved in the adaptive regulation of HCO3- secretion and NaCl reabsorption in the CNT/CCD under acid-base stress and establish αKG as a paracrine mediator involved in the functional coordination of the proximal and the distal parts of the renal tubule.

Stratigraphic, sedimentological and palaeoenvironmental constraints on the rise of the Urgonian platform in the western Swiss Jura

Urgonian-type carbonates are a characteristic feature of many late Early Cretaceous shallow-marine, tropical and subtropical environments. The presence of typical photozoan carbonate-producing communities including corals and rudists indicates the prevalence of warm, transparent and presumably oligotrophic conditions in a period otherwise characterized by the high density of globally occurring anoxic episodes. Of particular interest, therefore, is the exploration of relationships between Urgonian platform growth and palaeoceanographic change. In the French and Swiss Jura Mountains, the onset and evolution of the Urgonian platform have been controversially dated, and a correlation with other, better dated, successions is correspondingly difficult. It is for this reason that the stratigraphy and sedimentology of a series of recently exposed sections (Eclepens, Vaumarcus and Neuchatel) and, in addition, the section of the Gorges de l'Areuse were analysed. Calcareous nannofossil biostratigraphy, the evolution of phosphorus contents of bulk rock, a sequence-stratigraphic interpretation and a correlation of drowning unconformities with better dated sections in the Helvetic Alps were used to constrain the age of the Urgonian platform. The sum of the data and field observations suggests the following evolution: during the Hauterivian, important outward and upward growth of a bioclastic and oolitic carbonate platform is documented in two sequences, separated by a phase of platform drowning during the late Early Hauterivian. Following these two phases of platform growth, a second drowning phase occurred during the latest Hauterivian and Early Barremian, which was accompanied by significant platform erosion and sediment reworking. The Late Barremian witnessed the renewed installation of a carbonate platform, which initiated with a phase of oolite production, and which progressively evolved into a typical Urgonian carbonate platform colonized by corals and rudists. This phase terminated at the latest in the middle Early Aptian, due to a further drowning event. The evolution of this particular platform segment is compatible with that of more distal and well-dated segments of the same northern Tethyan platform preserved in the Helvetic zone of the Alps and in the northern subalpine chains (Chartreuse and Vercors).

Characterization of gravitational rock slope deformations at different spatial scales based on field, remote sensing and numerical approaches

Rock slope instabilities such as rock slides, rock avalanche or deep-seated gravitational slope deformations are widespread in Alpine valleys. These phenomena represent at the same time a main factor that control the mountain belts erosion and also a significant natural hazard that creates important losses to the mountain communities. However, the potential geometrical and dynamic connections linking outcrop and slope-scale instabilities are often unknown. A more detailed definition of the potential links will be essential to improve the comprehension of the destabilization processes and to dispose of a more complete hazard characterization of the rock instabilities at different spatial scales. In order to propose an integrated approach in the study of the rock slope instabilities, three main themes were analysed in this PhD thesis: (1) the inventory and the spatial distribution of rock slope deformations at regional scale and their influence on the landscape evolution, (2) the influence of brittle and ductile tectonic structures on rock slope instabilities development and (3) the characterization of hazard posed by potential rock slope instabilities through the development of conceptual instability models. To prose and integrated approach for the analyses of these topics, several techniques were adopted. In particular, high resolution digital elevation models revealed to be fundamental tools that were employed during the different stages of the rock slope instability assessment. A special attention was spent in the application of digital elevation model for detailed geometrical modelling of past and potential instabilities and for the rock slope monitoring at different spatial scales. Detailed field analyses and numerical models were performed to complete and verify the remote sensing approach. In the first part of this thesis, large slope instabilities in Rhone valley (Switzerland) were mapped in order to dispose of a first overview of tectonic and climatic factors influencing their distribution and their characteristics. Our analyses demonstrate the key influence of neotectonic activity and the glacial conditioning on the spatial distribution of the rock slope deformations. Besides, the volumes of rock instabilities identified along the main Rhone valley, were then used to propose the first estimate of the postglacial denudation and filling of the Rhone valley associated to large gravitational movements. In the second part of the thesis, detailed structural analyses of the Frank slide and the Sierre rock avalanche were performed to characterize the influence of brittle and ductile tectonic structures on the geometry and on the failure mechanism of large instabilities. Our observations indicated that the geometric characteristics and the variation of the rock mass quality associated to ductile tectonic structures, that are often ignored landslide study, represent important factors that can drastically influence the extension and the failure mechanism of rock slope instabilities. In the last part of the thesis, the failure mechanisms and the hazard associated to five potential instabilities were analysed in detail. These case studies clearly highlighted the importance to incorporate different analyses and monitoring techniques to dispose of reliable and hazard scenarios. This information associated to the development of a conceptual instability model represents the primary data for an integrated risk management of rock slope instabilities. - Les mouvements de versant tels que les chutes de blocs, les éboulements ou encore les phénomènes plus lents comme les déformations gravitaires profondes de versant représentent des manifestations courantes en régions montagneuses. Les mouvements de versant sont à la fois un des facteurs principaux contrôlant la destruction progressive des chaines orogéniques mais aussi un danger naturel concret qui peut provoquer des dommages importants. Pourtant, les phénomènes gravitaires sont rarement analysés dans leur globalité et les rapports géométriques et mécaniques qui lient les instabilités à l'échelle du versant aux instabilités locales restent encore mal définis. Une meilleure caractérisation de ces liens pourrait pourtant représenter un apport substantiel dans la compréhension des processus de déstabilisation des versants et améliorer la caractérisation des dangers gravitaires à toutes les échelles spatiales. Dans le but de proposer un approche plus globale à la problématique des mouvements gravitaires, ce travail de thèse propose trois axes de recherche principaux: (1) l'inventaire et l'analyse de la distribution spatiale des grandes instabilités rocheuses à l'échelle régionale, (2) l'analyse des structures tectoniques cassantes et ductiles en relation avec les mécanismes de rupture des grandes instabilités rocheuses et (3) la caractérisation des aléas rocheux par une approche multidisciplinaire visant à développer un modèle conceptuel de l'instabilité et une meilleure appréciation du danger . Pour analyser les différentes problématiques traitées dans cette thèse, différentes techniques ont été utilisées. En particulier, le modèle numérique de terrain s'est révélé être un outil indispensable pour la majorité des analyses effectuées, en partant de l'identification de l'instabilité jusqu'au suivi des mouvements. Les analyses de terrain et des modélisations numériques ont ensuite permis de compléter les informations issues du modèle numérique de terrain. Dans la première partie de cette thèse, les mouvements gravitaires rocheux dans la vallée du Rhône (Suisse) ont été cartographiés pour étudier leur répartition en fonction des variables géologiques et morphologiques régionales. En particulier, les analyses ont mis en évidence l'influence de l'activité néotectonique et des phases glaciaires sur la distribution des zones à forte densité d'instabilités rocheuses. Les volumes des instabilités rocheuses identifiées le long de la vallée principale ont été ensuite utilisés pour estimer le taux de dénudations postglaciaire et le remplissage de la vallée du Rhône lié aux grands mouvements gravitaires. Dans la deuxième partie, l'étude de l'agencement structural des avalanches rocheuses de Sierre (Suisse) et de Frank (Canada) a permis de mieux caractériser l'influence passive des structures tectoniques sur la géométrie des instabilités. En particulier, les structures issues d'une tectonique ductile, souvent ignorées dans l'étude des instabilités gravitaires, ont été identifiées comme des structures très importantes qui contrôlent les mécanismes de rupture des instabilités à différentes échelles. Dans la dernière partie de la thèse, cinq instabilités rocheuses différentes ont été étudiées par une approche multidisciplinaire visant à mieux caractériser l'aléa et à développer un modèle conceptuel trois dimensionnel de ces instabilités. A l'aide de ces analyses on a pu mettre en évidence la nécessité d'incorporer différentes techniques d'analyses et de surveillance pour une gestion plus objective du risque associée aux grandes instabilités rocheuses.

Cost effectiveness and cost utility of risedronate for osteoporosis treatment and fracture prevention in women: a Swiss perspective.

OBJECTIVES: To assess the incremental cost-effectiveness ratio (ICER) and incremental cost-utility ratio (ICUR) of risedronate compared to no intervention in postmenopausal osteoporotic women in a Swiss perspective. METHODS: A previously validated Markov model was populated with epidemiological and cost data specific to Switzerland and published utility values, and run on a population of 1,000 women of 70 years with established osteoporosis and previous vertebral fracture, treated over 5 years with risedronate 35 mg weekly or no intervention (base case), and five cohorts (according to age at therapy start) with eight risk factor distributions and three lengths of residual effects. RESULTS: In the base case population, the ICER of averting a hip fracture and the ICUR per quality-adjusted life year gained were both dominant. In the presence of a previous vertebral fracture, the ICUR was below euro45,000 (pound30,000) in all the scenarios. For all osteoporotic women>or=70 years of age with at least one risk factor, the ICUR was below euro45,000 or the intervention may even be cost saving. Age at the start of therapy and the fracture risk profile had a significant impact on results. CONCLUSION: Assuming a 2-year residual effect, that ICUR of risedronate in women with postmenopausal osteoporosis is below accepted thresholds from the age of 65 and even cost saving above the age of 70 with at least one risk factor.