PubMed · 16003105
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Marcus J Schultz, Esther K Wolthuis, Rogier M Determann. 2005. Mixing up old data.. https://doi.org/10.1097/01.ccm.0000170198.14613.f4
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BACKGROUND: The slope-intercept method is widely used for the determination of the plasma clearance of 51Cr-EDTA. When three or more plasma samples are used, the goodness-of-fit (r2) can be used as a measure of consistency of the samples. This parameter can not be used, however, if only two samples are available. PURPOSE: To evaluate whether the single-sample technique (SBS) can be used to check the consistency of the slope-intercept method using two blood samples (2BS) in children. METHODS: Simulated computer models of a mono-exponential curve were created in order to represent three children aged 3, 6 and 10 years, each with a large range of clearances values and three distribution volumes, respectively 20%, 25% and 30% of body weight. Errors were then introduced in the injected dose (errors from -50% to +50%) and on the 120 or 240 min blood sample (errors from -50% to +50%). The effects of these errors on the clearance measurement using 2BS and SBS methods were calculated and compared. RESULTS: The errors on the injected dose, the 120 min and 240 min plasma samples introduced errors in the same direction and with the same magnitude on both the SBS and 2BS clearance values. For that reason, the comparison between the SBS methods and the 2BS techniques has a low sensitivity in detecting an eventual error. Striking differences between the SBS method and the 2BS technique were only observed when considerable errors on the injected dose or plasma samples were introduced, particularly in case of a reduced clearance. The comparison between the SBS clearances calculated using the 120 min sample to that obtained using the 240 min samples is slightly more sensitive. However, this approach is also slightly less specific. A difference of more than 10 ml . min(-1). 1.73 m(-2) can be observed in the absence of an error. CONCLUSIONS: The use of the SBS for checking the consistency of the 2BS constitutes an insensitive approach to detect an eventual error in the injected dose or in the plasma samples. Obvious different results obtained by SBS and 2BS or between the SBS calculated using the 120 min and the 240 min samples suggest the presence of an error, but comparable results do not exclude erroneous measurement. Moreover, a difference of more than 10 ml . min(-1). 1.73 m(-2) can be observed in the absence of an error in the injected dose or in the plasma samples.
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Oceanic communities are sources or sinks of CO2, depending on the balance between primary production and community respiration. The prediction of how global climate change will modify this metabolic balance of the oceans is limited by the lack of a comprehensive underlying theory. Here, we show that the balance between production and respiration is profoundly affected by environmental temperature. We extend the general metabolic theory of ecology to the production and respiration of oceanic communities and show that ecosystem rates can be reliably scaled from theoretical knowledge of organism physiology and measurement of population abundance. Our theory predicts that the differential temperature-dependence of respiration and photosynthesis at the organism level determines the response of the metabolic balance of the epipelagic ocean to changes in ambient temperature, a prediction that we support with empirical data over the global ocean. Furthermore, our model predicts that there will be a negative feedback of ocean communities to climate warming because they will capture less CO2 with a future increase in ocean temperature. This feedback of marine biota will further aggravate the anthropogenic effects on global warming.