I don't how true this is but I heard they use to use air (not saline) to push blood back in the patient's system in certain countries. Its too hairraising to be real. Probablly a dialysis urban legend.
A single bubble isn’t going to do the trick.Let’s review the blood’s circulation pattern. Blood from the body flows into the right side of the heart, then out to the lungs, back to the left side of the heart where it is pumped to the body, thus completing the circuit. The lungs are excellent filters. They trap small blood clots and injected air bubbles. In actuality, the air bubble would be shattered into microbubbles by the churning action of the right ventricle, which pumps the blood into the lungs, and these tiny bubbles would dissolve into the blood. Any bubbles that survived this “washing machine” would be filtered by the lungs.Fifty to sixty CCs injected rapidly would travel into the right ventricle, where it could cut off the flow of blood. The beating heart relies upon the non-compressibility of liquids (blood in this case) to squeeze the blood out of the ventricles. Air, as are other gases, is compressible. This produces a sort of “vapor lock,” and almost instantaneous death can result. Quote