Influence of Dextran Infusion on the Pulmonary Hypertensive Effect of Concentrated Saline

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Abstract
Low-molecular-weight dextran, which is known to prevent the sludging of blood cells seen in shock, has recently been reported to reduce the toxicity of concentrated radiopaque agents. Experiments have been performed to determine whether this latter effect applies to other hyperosmotic solutions. An attempt was made to delineate the mechanism involved. One ml./Kg. of 15 per cent NaCl was rapidly injected into dogs before and after infusion of 10 ml./Kg. of 15 per cent low-molecular-weight dextran. This treatment significantly reduced the usual pulmonary-hypertensive response. However, other dextran preparations, plasma, and blood were equally effective. Moreover, previous infusion of isotonic saline also conferred immunity when given at a rate sufficient to raise left-atrial pressure. Let't-atrial hypertension produced independently of changes in blood volume evoked similar amelioration. If this latter change was prevented by concurrent bleeding, none of the infusions was beneficial. Vice versa, a fall in left-atrial pressure was associated with an accentuated reaction to 15 per cent NaCl. Microscopic examination of the intact lung during protection showed that red-cell agglutination still occurred from concentrated saline, but the small vessels were dilated. It is concluded that low-molecular-weight dextran and other infusions provide prophylaxis against the pulmonary-hypertensive effects of concentrated saline by reducing the susceptibility of the lung to microembolism through the development of left-atrial hypertension.