Murder by injection with a syringe with an air bubble in an artery is one of the favorite subjects in many detective novels. The perpetrator injects the contents of an empty syringe into the victim's vein, leaving nothing on his body except a tiny prick mark that the local pathologist would not be able to see. It is widely believed that a person will die if air enters the venous blood. Is this really so? Let's figure it out together.
In fact, the injection site that no one sees is another literary and cinematic myth. To find it, you don't even need to be the most brilliant of criminologists or the luminary of forensic medicine. After the death of a person, it becomes dark, and a light halo appears around it. So the average forensic scientist will quickly find him and understand the cause of death.
An air bubble that enters an artery and blocks the flow of blood to the heart or brain is called an air embolism. Air embolism can indeed be fatal. If it is a heart embolism, it can cause a heart attack or create a dangerous coronary airlock. If there is a cerebral embolism, a stroke may occur. However, an air bubble is unlikely to kill someone. First, the air must be injected into a large artery or vein - it will not work into a small one. Second, the air bubble itself must be large enough to be able to completely block the large vessel. According to experts, it is necessary to inject about 200 milliliters of air in order to cause someone's sudden death. A small bubble will simply dissolve in the cells of the body.
Under what circumstances can such an amount of air enter the vein, which is really enough to cause death? This is possible with injuries and injuries to the neck or chest. These situations are dangerous because the neck is above the level of the heart, and in the thoracic region the pressure is lower than in the environment. In this case, air is quickly sucked into the circulatory system.
Standard medical practice requires that the doctor make sure the syringe is free of air bubbles before giving the injection. The same applies to IVs that are used during or after surgery. The heart-lung machines have built-in filters that remove all accidental bubbles. Hospitals follow simple rule number one - "there should be no air anywhere."