Toward quantification of loop diuretic responsiveness for congestive heart failure

Figures

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  FIGURE 1. Conceptual representation of the interstitial space comprised of a glycosaminoglycan (GAG) network, which gives the tissue structure and rigidity, and surrounding interstitial fluid. In the presence of normal interstitial sodium (Na) concentration, Na is stored within the negative‐charged GAG network and interstitial Na and osmotic pressure (∏) are similar to that in the capillaries. The rigid GAG network keeps compliance (C) low. The normal osmotic pressure and high hydrostatic pressure (P) of the interstitium maintain normal water balance between the interstitium and capillaries. In situations of Na overload, the GAG network is disrupted, tissue compliance increases, and hydrostatic pressure decreases. Excess Na favors high osmotic pressure in the interstitial fluid and along with the decreased hydrostatic pressure, net water movement occurs from the capillaries into the interstitium

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  FIGURE 2. Conceptual representation of the consequences of hypotonic or free water loss (ie, diuresis) vs more balanced or isotonic fluid loss (ie, diuresis and natriuresis) in congestive heart failure (CHF). (A) Body water (grid) is distributed among the intracellular, interstitial, and intravascular spaces, all with similar osmolarity. Movement of water from intracellular to extracellular spaces is influenced by the relative osmolarity between spaces. In the extracellular spaces, Na makes up the majority of osmoles and H2O and Na freely diffuse between the interstitial and intravascular spaces. (B) During CHF, retention of H2O and Na causes expansion of blood volume and congestion in the form of excess H2O in the interstitial and intravascular spaces. (C) Free water excretion without accompanying natriuresis increases the osmolarity of the extracellular spaces, which promotes the undesirable effect of intracellular water loss through osmosis and all body spaces experience H2O loss (ie, dehydration). (D) Excretion of both H2O and Na decongests the interstitial and intravascular spaces while maintaining normal extracellular osmolarity and avoidance of intracellular water loss