流動パラフイン下における微量の血液ガス分析試料の保存に関する検討

On the reduction of the carbon dioxide content of a small amount of blood plasma during the preservation under liquid paraffine.

　血液ガスの分析を行う場合は一般にそのガス分圧が大気圧と著しく異るから，試料中のガスの逸散を防ぐ目的で，通常流動パラフインを重畳することが行われている。しかしながら他面流動パラフインには極めてよくガスを吸収する性質があることに注意を払わなければならない。近年化学分析法の微量化の進展に伴い，血液ガス分析の面にも1回の分析試料が0.03mlで足りるCopp-Nate—lson^1）の装置が広く用いられつつある。この場合試料が極めて僅かであるために流動パラフインによるガス吸収の危険もより多いことが考えられる。Kubie^2）によると流動パラフインのCO₂吸収率は20℃で0.873である。これより炭酸張力40mmHgを有する血漿0.1mlが1mlの流動パラフインと接触した場合吸収され得るCO₂の量は血漿総炭酸の約90％にも達し得る計算となる。此の様に分析試料が少い場合に流動パラフイン下における血漿の保存が実際にどれ位の総炭酸含有量の減少を来すものかを調査する目的で本実験を行つた。

Though it is well known as a routine procedure that the blood or plasma is preserved under liquid para-ffine to prevent the rapid escape of its gas content, much attention must be paid to the high gas solubi-lity of the liquid paraffine.

Since Natelson reported on the blood gas analyzer which is able to determine the plasma CO₂ content in only 0.03 ml sample, a great advantage has been seen in an experiment in the case of using small exper-imental animals. But the smaller the amount of the blood is preserved under the oil, the more will incr-ease the possibility of absorbing its gas content with the oil owing to its rather larger surface comparing with its small mass.

This experiment was performed with the object to perceive the real loss of the blood gas content when a small amount of blood plasma (ca. 0.1 ml) was preserved under liquid paraffine (ca. 4cm layer) in a conical centrifuge tube. Total plasma CO₂ as a blood gas was determind by the Copp-Natelson's apparatus at the room temperature ranging from 19℃ to 27℃.

The results obtained were as follows :

1) The rate of the escaping of the CO₂ was rather fast till one hour after the preserving the plasma under the oil, then its rate became alower as time lapsed. The average value of the loss of the plasma CO₂ was 2.0 vol.% at 1 hour storage and 3.7 vol.% at 24 hours.

2) Four kinds of commercial liquid paraffine furnished by different chemical companies were each ex-amined to compaire their abilities preventing the escape of the plasma CO₂. A definite standing was obs-erved.

3) The average 1.5 vol.% loss of the plasma CO₂ was seen after the 10 minutes centrifugation.

The most convenient and reliable procedure to prevent such losses of blood gases as described above is, it may he concluded, to preserve the plasma in a syringe illustrated in Fig. 1 on this acount.