Critical care : the official journal of the Critical Care Forum
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Observational Study
Identification of an optimal threshold to define oliguria in critically ill patients: an observational study.
The relevance of current consensus threshold to define oliguria has been challenged by small observational studies. We aimed to determine the optimal threshold to define oliguria in critically-ill patients. ⋯ The widely used cut-off for oliguria of 0.5 ml/kg/h over 6 h may be too conservative. A cut-off of 0.2 ml/kg/h over 3 or 6 h is supported by the data and should be considered in further definitions of oliguria.
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Fluid normally exchanges freely between the plasma and interstitial space and is returned primarily via the lymphatic system. This balance can be disturbed by diseases and medications. ⋯ Herein, we have combined data from fluid kinetic trials with previously unconnected mechanisms of inflammation, interstitial fluid physiology and lymphatic pathology to synthesize a novel explanation for common and clinically relevant examples of circulatory dysregulation. Experimental studies suggest that two key mechanisms contribute to the combination of hypovolemia, hypoalbuminemia and edema; (1) acute lowering of the interstitial pressure by inflammatory mediators such as TNFα, IL-1β, and IL-6 and, (2) nitric oxide-induced inhibition of intrinsic lymphatic pumping.