Nitrous oxide does not produce a clinically important sparing effect during closed-loop delivered propofol-remifentanil anaesthesia guided by the bispectral index: a randomized multicentre study†‡

Background Nitrous oxide (N2O) offers both hypnotic and analgesic characteristics. We therefore tested the hypothesis that N2O administration decreases the amount of propofol and remifentanil given by a closed-loop automated controller to maintain a similar bispectral index (BIS). Methods In a randomized multicentre double-blind study, patients undergoing elective surgery were randomly assigned to breathe 60% inspired N2O (N2O group) or 40% oxygen (AIR group). Anaesthesia depth was evaluated by the proportion of time where BIS was within the range of 40-60 (BIS40-60). The primary outcomes were propofol and remifentanil consumption, with reductions of 20% in either being considered clinically important. Results A total of 302 patients were randomized to the N2O group and 299 to the AIR group. At similar BIS40-60 [79 (67-86)% vs 76 (65-85)%], N2O slightly decreased propofol consumption [4.5 (3.7-5.5) vs 4.8 (4.0-5.9) mg kg−1 h−1, P=0.032], but not remifentanil consumption [0.17 (0.12-0.23) vs 0.18 (0.14-0.24) µg kg−1 min−1]. For the subgroups of men, at similar BIS40-60 [80 (72-88)% vs 80 (70-87)%], propofol [4.2 (3.4-5.3) vs 4.4 (3.6-5.4) mg kg−1 h−1] and remifentanil [0.19 (0.13-0.25) vs 0.18 (0.15-0.23) µg kg−1 min−1] consumptions were similar in the N2O vs AIR group, respectively. For the subgroups of women, at similar BIS40-60 [76 (64-84)% vs 72 (62-82)%], propofol [4.7 (4.0-5.8) vs 5.3 (4.5-6.6) mg kg−1 h−1, P=0.004] and remifentanil [0.18 (0.13-0.25) vs 0.20 (0.15-0.27) µg kg−1 min−1, P=0.029] consumptions decreased with the co-administration of N2O. Conclusions With automated drug administration titrated to comparable BIS, N2O only slightly reduced propofol consumption and did not reduce remifentanil consumption. There was a minor gender dependence, but not by a clinically important amount. Clinical trial registration This study was registered at ClinicalTrials.gov, number NCT0054720

Quaternary glacial history of the Mediterranean mountains

Glacial and periglacial landforms are widespread in the mountains of the Mediterranean region. The evidence for glacial and periglacial activity has been studied for over 120 years and it is possible to identify three phases of development in this area of research. First, a pioneer phase characterized by initial descriptive observations of glacial landforms; second, a mapping phase whereby the detailed distribution of glacial landforms and sediments have been depicted on geomorphological maps; and, third, an advanced phase characterized by detailed understanding of the geochronology of glacial sequences using radiometric dating alongside detailed sedimentological and stratigraphical analyses. It is only relatively recently that studies of glaciated mountain terrains in the Mediterranean region have reached an advanced phase and it is now clear from radiometric dating programmes that the Mediterranean mountains have been glaciated during multiple glacial cycles. The most extensive phases of glaciation appear to have occurred during the Middle Pleistocene. This represents a major shift from earlier work whereby many glacial sequences were assumed to have formed during the last cold stage. Glacial and periglacial deposits from multiple Quaternary cold stages constitute a valuable palaeoclimatic record. This is especially so in the Mediterranean mountains, since mountain glaciers in this latitudinal zone would have been particularly sensitive to changes in the global climate system. © 2006 Edward Arnold (Publishers) Ltd

Les techniques artisanales d'exploitation des gîtes alluviaux : analogies dans le temps et dans l'espace

Cet étude montre que, par comparaison avec l'exploitation de l'or dans le nord-ouest de l'Espagne à l'époque romaine, les techniques actuellement en usage aussi bien en Amérique du Sud (Bolivie, Pérou) qu'en Afrique centrale (Rwanda) sont sensiblement les mêmes qu'autrefois, sans que pour autant il ait pu y avoir d'influence des plus anciennes sur les récentes. (Résumé d'auteur

Les techniques artisanales d'exploitation des gîtes alluviaux : analogies dans le temps et dans l'espace

Cet étude montre que, par comparaison avec l'exploitation de l'or dans le nord-ouest de l'Espagne à l'époque romaine, les techniques actuellement en usage aussi bien en Amérique du Sud (Bolivie, Pérou) qu'en Afrique centrale (Rwanda) sont sensiblement les mêmes qu'autrefois, sans que pour autant il ait pu y avoir d'influence des plus anciennes sur les récentes. (Résumé d'auteur

Neogene erosion and uplift of the western edge of the Andean Plateau as determined by detrital heavy mineral analysis

Recent studies show that the western margin of the Andean plateau was uplifted during Neogene time in the form of a proto-Western Cordillera through a system of high angle reverse faults. In this study, we use XRD and microprobe data of heavy minerals (HM) contained in Neogene sandstones of the Central Depression and Copaquilla Depression, to the west of the Andean plateau, to better understand the paleogeographical evolution along this border. The composition of detrital metamorphic HM assemblages, e.g. garnet-staurolite and actinolite-epidote, found in the Neogene sandstones, correlates well with that of the HM in the basement. Based on this correlation, we outline the different stages of exhumation and surface exposure of the metamorphic and crystalline basement rocks that crop out along the eastern part of the Copaquilla Depression (Belen area). In addition, the vertical stratigraphic distribution of detrital volcanic HM assemblages, e.g. olivine-pyroxenes and amphibole-biotite, records in detail the evolution of the Neogene volcanism, showing the stages in which volcanics in the Precordillera covered the basement. A first stage of basement exposure took place before 26 Ma. This was followed by Early to Late Miocene (ca. 26-10 Ma) intermediate to andesite-basalt volcanism which led to basement burial. Later on, ca. 10-2.7 Ma, a deep incision of the Precordillera associated with a generalized uplift of the plateau exposed the basement again

Electrode Selection for Noninvasive Fetal Electrocardiogram Extraction using Mutual Information Criteria

Abstract. Blind source separation (BSS) techniques have revealed to be promising approaches for the noninvasive extraction of fetal cardiac signals from maternal abdominal recordings. From previous studies, it is now believed that a carefully selected array of electrodes well-placed over the abdomen of a pregnant woman contains the required ‘information ’ for BSS, to extract the complete fetal components. Based on this idea, previous works have involved array recording systems and sensor selection strategies based on the Mutual Information (MI) criterion. In this paper the previous works have been extended, by considering the 3-dimensional aspects of the cardiac electrical activity. The proposed method has been tested on simulated and real maternal abdominal recordings. The results show that the new sensor selection strategy together with the MI criterion, can be effectively used to select the channels containing the most ‘information ’ concerning the fetal ECG components from an array of 72 recordings. The method is hence believed to be useful for the selection of the most informative channels in online applications, considering the different fetal positions and movements

Geochemistry of Chilean rivers within the central zone : distinguishing the impact of mining, lithology and physical weathering

Several rivers of Chile from the latitude 30 degrees-38 degrees have been sampled during a stable anticyclonic period (October 2008). Firstly, our aim was to evaluate the dissolved chemical composition (major and trace elements) of poorly known central Chilean rivers. Secondly, we used a co-inertia analysis (see Doledec and Chessel in Freshw Biol 31:277-294, 1994) to explore the possible relationships between the concentrations of elements and the environmental parameters [surface of the basin (km(2))/mining activity (%)/average height (m)/watershed mean slope (%)/% of the surface covered by vegetation, sedimentary rocks, volcano-sedimentary rocks, volcanic rocks, granitoid rocks/erosion rate (mm/year)]. Globally, the major elements concentration could be explained by a strong control of mixed silicate and carbonate and evaporate lithology. The statistical treatment reveals that the highest metal and metalloids loads of Tinguiririca, Cachapoal, Aconcagua, Choapa, Illapel and Limari could be explained by the contribution of the mining activities in the uppermost part of these watersheds and/or by the higher geochemical background. Indeed, it remains difficult to decipher between a real mining impact and a higher geochemical background. Even if these rivers could be impacted by AMD process, the size of these watersheds is capable of diluting AMD waters by the alkaline character of tributaries that induce acid neutralization and decrease the level of metals and metalloids

Non-steady long-term uplift rates and Pleistocene marine terrace development along the andean margin of Chile (31°S) inferred from 10Be dating

International audiencePleistocene uplift of the Chilean coast is recorded by the formation of wave-cut platforms resulting from marine erosion during sea-level highstands. In the Altos de Talinay area (~ 31°S), we have identified a sequence of 5 wave-cut platforms. Using in situ produced 10Be exposure ages we show that these platforms were formed during interglacial periods at 6, 122, 232, 321 and 690 ka. These ages correspond to marine isotopic stages (MIS) or substages (MISS) 1, 5e, 7e, 9c and 17. Shoreline angle elevations used in conjunction with our chronology of wave-cut platform formation, illustrate that surface uplift rates vary from 103 ± 69 mm/ka between 122 and 6 ka, to 1158 ± 416 mm/ka between 321 and 232 ka. The absence of preserved platforms related to the MIS 11, 13 and 15 highstands likely reflects slow uplift rates during these times. We suggest that since 700 ka, the Altos de Talinay area was predominantly uplifted during 2 short periods following MIS 17 and MISS 9c. This episodic uplift of the Chilean coast in the Pleistocene may result from subduction related processes, such as pulses of tectonic accretion at the base of the forearc wedge