Temperature Response of Respiration Across the Heterogeneous Landscape of the Alaskan Arctic Tundra

AbstractPredictions of the response of ecosystem respiration to warming in the Arctic are not well constrained, partly due to the considerable spatial heterogeneity of these permafrost‐dominated areas. Accurate calculations of in situ temperature sensitivities of respiration (Q10) are vital for the prediction of future Arctic emissions. To understand the impact of spatial heterogeneity on respiration rates and Q10, we compared respiration measured from automated chambers across the main local polygonized landscape forms (high and low centers, polygon rims, polygon troughs) to estimates from the flux‐partitioned net ecosystem exchange collected in an adjacent eddy covariance tower. Microtopographic type appears to be the most important variable explaining the variability in respiration rates, and low‐center polygons and polygon troughs show the greatest cumulative respiration rates, possibly linked to their deeper thaw depth and higher plant biomass. Regardless of the differences in absolute respiration rates, Q10 is surprisingly similar across all microtopographic features, possibly indicating a similar temperature limitation to decomposition across the landscape. Q10 was higher during the colder early summer and lower during the warmer peak growing season, consistent with an elevated temperature sensitivity under colder conditions. The respiration measured by the chambers and the estimates from the daytime flux‐partitioned eddy covariance data were within uncertainties during early and peak seasons but overestimated respiration later in the growing season. Overall, this study suggests that it is possible to simplify estimates of the temperature sensitivity of respiration across heterogeneous landscapes but that seasonal changes in Q10 should be incorporated into model simulations

Defining the characteristics and expectations of fluid bolus therapy : A worldwide perspective

Purpose: The purpose of the study is to understand what clinicians believe defines fluid bolus therapy (FBT) and the expected response to such intervention. Methods: We asked intensive care specialists in 30 countries to participate in an electronic questionnaire of their practice, definition, and expectations of FBT. Results: We obtained 3138 responses. Despite much variation, more than 80% of respondents felt that more than 250 mL of either colloid or crystalloid fluid given over less than 30 minutes defined FBT, with crystalloids most acceptable. The most acceptable crystalloid and colloid for use as FBT were 0.9% saline and 4% albumin solution, respectively. Most respondents believed that one or more of the following physiological changes indicates a response to FBT: a mean arterial pressure increase greater than 10 mm Hg, a heart rate decrease greater than 10 beats per minute, an increase in urinary output by more than 10 mL/h, an increase in central venous oxygen saturation greater than 4%, or a lactate decrease greater than 1 mmol/L. Conclusions: Despite wide variability between individuals and countries, clear majority views emerged to describe practice, define FBT, and identify a response to it. Further investigation is now required to describe actual FBT practice and to identify the magnitude and duration of the physiological response to FBT and its relationship to patient-centered outcomes. (C) 2016 Elsevier Inc. All rights reserved.Peer reviewe

Defining the characteristics and expectations of fluid bolus therapy: a worldwide perspective

Purpose: The purpose of the study is to understand what clinicians believe defines fluid bolus therapy (FBT) and the expected response to such intervention. Methods: We asked intensive care specialists in 30 countries to participate in an electronic questionnaire of their practice, definition, and expectations of FBT. Results: We obtained 3138 responses. Despite much variation, more than 80% of respondents felt that more than 250 mL of either colloid or crystalloid fluid given over less than 30 minutes defined FBT, with crystalloids most acceptable. The most acceptable crystalloid and colloid for use as FBT were 0.9% saline and 4% albumin solution, respectively. Most respondents believed that one or more of the following physiological changes indicates a response to FBT: a mean arterial pressure increase greater than 10 mm Hg, a heart rate decrease greater than 10 beats per minute, an increase in urinary output by more than 10 mL/h, an increase in central venous oxygen saturation greater than 4%, or a lactate decrease greater than 1 mmol/L. Conclusions: Despite wide variability between individuals and countries, clear majority views emerged to describe practice, define FBT, and identify a response to it. Further investigation is now required to describe actual FBT practice and to identify the magnitude and duration of the physiological response to FBT and its relationship to patient-centered outcomes.Facultad de Ciencias Médica