静脉中的空气：部分不可见的现象

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Intravenous Air: The Partially Invisible Phenomenon

背景与目的

空气注射在静脉给药期间是需要小心避免的。然而，环境里的空气会溶解在需要注射的溶液中，当溶液在流体加温系统和（或）体内加温到正常体温时，一部分气体会以气泡的形式从溶液中排出来。我们试图在理论上测量在室温时溶解的气体的比例，以及4℃注射器中血液加热到37℃排出的气体比例。

方  法

根据亨利理论，在各种温度下进行氯化钠（0.9％），浓缩红细胞和新鲜冷冻血浆的平衡溶解空气计算。测量室温时氯化钠（0.9％）和4℃血液制品（浓缩红细胞和新鲜冷冻血浆）在室温水浴中加热至37℃时的排出气体体积。 测量到的气体体积被认定为维持平衡饱和度所需的理论排气量的一部分。

结  果

在每升液体的毫升气体中测量的静脉管道中的排气体积分别为氯化钠（0.9％）1.4±0.3mL / L（n = 6），浓缩红细胞3.4±0.2mL / L（n = 6），新鲜冷冻血浆4.8±0.8mL / L（n = 6），当这些流体从各自的起始温度升温至体温时，对于相同的流体和温度，保持平衡饱和度所需的理论排气体积分别为氯化钠（0.9％）为4.7mL / L，浓缩红细胞8.3mL / L，新鲜冷冻血浆10.9mL / L。作为理论排气量的一部分，测量的空气体积分别为氯化钠（0.9％），浓缩红细胞和新鲜冷冻血浆的30％，41％和44％。 在给药前将晶体溶液预热至37℃，可显著减少了排气。

结  论

在室温溶液中存在明显而潜在的与临床有关的定量溶解气体，4℃的红细胞和血浆溶液在升温至体温后也会出现。 根据本研究的结果，这种排气的很大一部分也预计会发生在体内循环中。这可以通过预热来进行实质地预防。

原始文献摘要

Varga C, Luria I, Gravenstein N. Intravenous Air: The Partially Invisible Phenomenon[J]. Anesthesia & Analgesia, 2016, 123(5):1149.

PURPOSE:

Air injection is carefully avoided during IV solution administration; however, ambient air is dissolved in all liquids used for intravenous (IV) therapy. A portion of this gas will come out of solution in the form of bubbles as the solution is warmed to body temperature in a fluid warming system and/or within the body. We sought to quantify the proportion of the gas theoretically dissolved in room temperature crystalloid and 4°C blood products that comes out of solution in the IV tubing on warming to 37°C.

METHODS:

Equilibrium-dissolved air calculations were performed for sodium chloride (0.9%), packed red blood cells, and fresh frozen plasma at various temperatures according to Henry’s Law. Outgassed gas volumes were experimentally measured for room temperature sodium chloride (0.9%) and 4°C blood products (packed red blood cells and fresh frozen plasma) warmed to 37°C during infusion into a body temperature water bath. The measured gas volumes were quantified as a fraction of the theoretical outgassing volumes required to maintain equilibrium saturation.

RESULTS:

Measured outgassed volumes in the IV tubing in milliliters of gas per liter of fluid were 1.4 ± 0.3 mL/L (n = 6) for sodium chloride (0.9%), 3.4 ± 0.2 mL/L (n = 6) for packed red blood cells, and 4.8 ± 0.8 mL/L (n = 6) for fresh frozen plasma when these fluids were warmed to body temperature from their respective starting temperatures. Theoretical outgassed gas volumes required to maintain equilibrium saturation for the same fluids and temperatures are 4.7 mL/L for sodium chloride (0.9%), 8.3 mL/L for packed red blood cells, and 10.9 mL/L for fresh frozen plasma. As a fraction of the theoretical outgassing volumes, the measured air volumes represented 30%, 41%, and 44%, respectively, for sodium chloride (0.9%), packed red blood cells, and fresh frozen plasma. Prewarming crystalloid solutions to 37°C before administration significantly reduced the outgassing.

CONCLUSION:

A significant and potentially clinically relevant amount of the resident dissolved gas in room temperature crystalloid, and 4°C packed red blood cells and plasma solutions comes out of solution on warming to body temperature. A nontrivial fraction of this outgassing

is also expected to occur within the body circulation based on the results of this study. This can be substantially prevented by prewarming. 

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