| 1. |
- Hahn, Robert G, et al.
(författare)
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Isoflurane inhibits compensatory intravascular volume expansion after hemorrhage in sheep
- 2006
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Ingår i: Anesthesia and Analgesia. - : Lippincott Williams & Wilkins. - 0003-2999 .- 1526-7598. ; 103:2, s. 350-358
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Tidskriftsartikel (refereegranskat)abstract
- After hemorrhage, blood volume is partially restored by transcapillary refill, a process of spontaneous compensatory intravascular volume expansion that we hypothesized would be inhibited by anesthesia. Six chronically instrumented sheep were subjected to four randomly ordered experiments while conscious or during anesthesia with isoflurane. After plasma volume measurement (indocyanine green), 15% or 45% of the blood volume was withdrawn. To quantify transcapillary refill, mass balance and kinetic calculations utilized repeated measurements of hemoglobin concentration, assuming that transcapillary refill would dilute hemoglobin concentration. After 15% hemorrhage, mean arterial blood pressure remained stable in both conscious and isoflurane-anesthetized sheep (normotensive hemorrhage) but decreased after 45% hemorrhage (hypotensive hemorrhage). After either normotensive or hypotensive hemorrhage, transcapillary refill occurred more rapidly during the first 40 min than during the next 140 min (P < 0.001). In conscious sheep, at 180 min, 57% and 42% of the bled volume had been restored after normotensive and hypotensive hemorrhage, respectively, in contrast to only 13% and 27% (P < 0.001) in isoflurane-anesthetized sheep. A novel kinetic model implicated hemodynamic factors in rapid, early transcapillary refill and decreased plasma oncotic pressure in subsequent slower filling. We conclude that isoflurane inhibits transcapillary refill after both normotensive and hypotensive hemorrhage in sheep.
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| 2. |
- Rockström, Johan, et al.
(författare)
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A safe operating space for humanity
- 2009
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 461:7263, s. 472-475
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Tidskriftsartikel (refereegranskat)
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| 3. |
- Rockström, Johan, et al.
(författare)
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Planetary Boundaries : Exploring the Safe Operating Space for Humanity
- 2009
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Ingår i: Ecology and Society. - 1708-3087. ; 14:2, s. 32-
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Tidskriftsartikel (refereegranskat)abstract
- Anthropogenic pressures on the Earth System have reached a scale where abrupt global environmental change can no longer be excluded. We propose a new approach to global sustainability in which we define planetary boundaries within which we expect that humanity can operate safely. Transgressing one or more planetary boundaries may be deleterious or even catastrophic due to the risk of crossing thresholds that will trigger non-linear, abrupt environmental change within continental- to planetary-scale systems. We have identified nine planetary boundaries and, drawing upon current scientific understanding, we propose quantifications for seven of them. These seven are climate change (CO2 concentration in the atmosphere <350 ppm and/or a maximum change of +1 W m(-2) in radiative forcing); ocean acidification (mean surface seawater saturation state with respect to aragonite >= 80% of pre-industrial levels); stratospheric ozone (<5% reduction in O-3 concentration from pre-industrial level of 290 Dobson Units); biogeochemical nitrogen (N) cycle (limit industrial and agricultural fixation of N-2 to 35 Tg N yr(-1)) and phosphorus (P) cycle (annual P inflow to oceans not to exceed 10 times the natural background weathering of P); global freshwater use (<4000 km(3) yr(-1) of consumptive use of runoff resources); land system change (<15% of the ice-free land surface under cropland); and the rate at which biological diversity is lost (annual rate of <10 extinctions per million species). The two additional planetary boundaries for which we have not yet been able to determine a boundary level are chemical pollution and atmospheric aerosol loading. We estimate that humanity has already transgressed three planetary boundaries: for climate change, rate of biodiversity loss, and changes to the global nitrogen cycle. Planetary boundaries are interdependent, because transgressing one may both shift the position of other boundaries or cause them to be transgressed. The social impacts of transgressing boundaries will be a function of the social-ecological resilience of the affected societies. Our proposed boundaries are rough, first estimates only, surrounded by large uncertainties and knowledge gaps. Filling these gaps will require major advancements in Earth System and resilience science. The proposed concept of "planetary boundaries" lays the groundwork for shifting our approach to governance and management, away from the essentially sectoral analyses of limits to growth aimed at minimizing negative externalities, toward the estimation of the safe space for human development. Planetary boundaries define, as it were, the boundaries of the "planetary playing field" for humanity if we want to be sure of avoiding major human-induced environmental change on a global scale.
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| 4. |
- Sicardi Salomón, Z., et al.
(författare)
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Progressive decrease in glucose clearance during surgery
- 2006
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Ingår i: Acta Anaesthesiologica Scandinavica. - : Wiley-Blackwell. - 0001-5172 .- 1399-6576. ; 50:7, s. 848-854
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Anaesthesia and surgery reduce the clearance of glucose. We studied how surgical procedures of different magnitude affect the clearance of a glucose load.METHODS: An intravenous infusion of 10 ml/kg/h of 2.5% buffered glucose was given over 80 min to 26 patients with a mean age of 50 years. The infusion started with the skin incision during minor surgery (inguinal hernia repair), medium-range surgery (laparoscopic cholecystectomy) and major surgery (aortic surgery, gastrectomy or colorectal surgery). General anaesthesia was induced in all patients and was supplemented by thoracic epidural analgesia for those undergoing major surgery. Plasma glucose was measured repeatedly for comparison of the clearance and endogenous glucose production during and after the infusion.RESULTS: Metabolic changes affected the shape of the plasma glucose curves more than the peak values. In those undergoing minor surgery, the clearance after the infusion was 65% of that recorded during the actual administration of glucose. The corresponding values for medium-range and major surgery were 37% and 60%, respectively (P < 0.001). The limited decrease in clearance in major surgery can probably be attributed to the epidural analgesia. In all three groups, the estimated endogenous glucose production decreased by the same magnitude as the clearance. The volume of distribution for glucose averaged 10.3 l.CONCLUSION: The hyperglycaemic effect of anaesthesia and surgery was not fully expressed within 80 min, regardless of the extent of surgery, and therefore appears to develop slowly. Even minor surgical trauma affected the metabolism of glucose.
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| 5. |
- Svensen, Christer H, et al.
(författare)
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Arteriovenous differences in plasma dilution and the distribution kinetics of lactated ringer's solution
- 2009
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Ingår i: Anesthesia and Analgesia. - : Lippincott Williams & Wilkins. - 0003-2999 .- 1526-7598. ; 108:1, s. 128-133
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Conventional concept suggests that infused crystalloid fluid is first distributed in the plasma volume and then, since the capillary permeability for fluid is very high, almost instantly equilibrates with the extracellular fluid space. We challenge whether this view is consistent with findings based on volume kinetic analysis.METHODS: Fifteen volunteers received an IV infusion of 15 mL/kg of lactated Ringer's solution during 10 min. Simultaneous arterial and venous blood hemoglobin (Hgb) samples were obtained and Hgb concentrations measured. The arteriovenous (AV) difference in Hgb dilution in the forearm was determined and a volume kinetic model was fitted to the series of Hgb concentrations in arterial and venous blood.RESULTS: The AV difference in plasma dilution was only positive during the infusion and for 2.5 min thereafter, which represents the period of net flow of fluid from plasma to tissue. Kinetic analysis showed that volume expansion of the peripheral fluid space began to decrease 14 min (arterial blood) and 20 min (venous blood) after the infusion ended. Distribution of lactated Ringer's solution apparently occurs much faster in the forearm than in the body as a whole. Therefore, the AV difference in the arm does not accurately reflect the distribution of Ringer's solutions or whole-body changes in plasma volume.CONCLUSIONS: The relatively slow whole-body distribution of lactated Ringer's solution, which boosts the plasma volume expansion during and for up to 30 min after an infusion, is probably governed by a joint effect of capillary permeability and differences in tissue perfusion between body regions.
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