Venous return: a fresh start Dalmau, Rafael
American journal of physiology. Heart and circulatory physiology,
11/2019, Volume:
317, Issue:
5
Journal Article
In other words, the input stimulus in the FR is, by definition, the fluid bolus (or “challenge”) alone, whereas the so-called “dynamic tests” (or “preload challenges”) are, as the authors stated, a ...way of predicting potential FR by a host of reversible maneuvers to inferre the preload-reserve of the heart, not the FR in itself. ...in the case of FR, preload is increased by volume expansion (provided that the ventricular preload-reserve is recruitable) and the stroke volume is increased according to Starling's law. Unlike fluid responsiveness (defined by a given increase in cardiac output) and fluid overload (by a given amount of fluid accumulation, in terms of body weight), “fluid tolerance” lacks quantitative inputs and outputs, only relying on the onset of organ impairment, which, as mentioned, is multifactorial. 3)Due to the reliance on the appearance of organ damage, the diagnosis of “fluid tolerance” has to be retrospective (contrary to what is indicated in Table 1), just like the diagnosis of fluid overload. ...there seems to be a contradiction between what is the main goal of the emerging fluid-restrictive, pro-early-vasopressors paradigms —a therapeutic strategy that I personally follow— and the initial premise regarding what is said to be the role of intravenous fluids: —“Fluids are the first-line resuscitation intervention in septic shock, aiming at restoring tissue perfusion by effectively increasing cardiac output and oxygen delivery” 1—, in that a direct connection is assumed between fluid therapy and tissue flow (and oxygen delivery), when fluids are actually the most inefficient and unpredictable means to increase systemic flow (except, of course, in cases of evident hypovolemia) and to enhance oxygen delivery.
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