hemolysis and what can cause it.Posted: February 8, 2015
as a medical technologist(i run the tests for blood work) of 14 years i’ve experienced quite a lot in the way of rejected specimens. one way a specimen can be rejected by someone who works in the lab is for the specimen to be hemolyzed. hemolysis is what happens when cells burst or lyse causing what would have been yellow serum or plasma to become pink or red. the severity of hemolysis is determined by the color of the serum or plasma. light pink would be trace to 1+ with gross hemolysis or 4+ being a bright red color. hemolysis can affect potassium levels along with other tests like magnesium. it can also affect the outcome of colorimetric methods used for testing. an example would be coagulation studies. some instruments are affected by hemolysis while other instruments with a different methodology are not. thus, the reason why different labs will have different standards for specimen rejection. for example, one lab may use one test methodology while another lab uses a different analyzer with a different way of testing the same test. there is also a difference in what is acceptable as part of the culture of one lab to another, even one tech to another. this isn’t a standardized part of working in a lab, and tech discretion is something that is usually followed when determining whether a specimen needs to be rejected and redrawn. i personally will run a chemistry level if a specimen is slight to moderately hemolyzed and note that the specimen is hemolyzed IF the potassium level is normal and the patient does not have a history of low potassium levels. other techs might have different standards they set for themselves as to what they reject.
what causes hemolysis? i don’t pretend to be an expert by any means, but i do have enough experience to explain the more common causes of specimen hemolysis.
the most prevalent reason a specimen becomes hemolyzed is because there was trouble acquiring the specimen. either the patient was a hard stick, or the person drawing the blood had a hard time getting blood from the patient. blood should flow free. it should be a smooth draw with no stops and starts. the easier the blood is to obtain, the less likely it is to be hemolyzed. the longer it takes to get the blood in the tubes means there is a chance for clotting(cells clump together) which when forced into a tube can cause hemolysis. another method i know of that causes hemolysis by force is when a health care professional uses a syringe to draw from a line or port. instead of pulling back the plunger of the needle a little bit at a time, the plunger is pulled all the way back to the back of the syringe forcing the blood to fill the syringe. the blood is forced into the syringe instead of being coaxed into it a small amount at a time which damages the red cells and causes hemolysis.
the needle crimp-another way to cause hemolysis. when drawing with a smaller gauge needle, it is easy to bend the needle when either drawing the specimen or putting the specimen in the tubes. the average size of a rbc is 6-7 microns. the lumen of a smaller gauge needle is just enough for those cells to pass through without being damaged. when the needle on a syringe is bent, even if it is straightened, the crimp will damage cells that pass through that part of the needle. the cells are shredded or burst open causing hemolysis. the solution is to replace the needle and use a new tube if possible.
another reason hemolysis can occur is the patient’s disease process. the cells are more fragile than normal. this can be part of the disease state or due to medications or other substances the patient is exposed to. these occurrences of hemolysis are relatively rare and are usually discovered after multiple collections with different people drawing the blood. it was easy to collect, but it is still hemolyzed usually means there is something going on with the patient and not the people drawing the blood.
prolonged tourniquet use can also cause damage to cells as well as vigorous mixing of the tubes blood is collected in. the goal of mixing anticoagulant tubes is to get the anticoagulant in the tube to mix with the cells preventing clotting. not all tubes require inverting or mixing, but the ones that do should never be shaken. inverting the tubes several times is enough to mix the specimen.
in general, a lab is only as good as the specimen it receives. there are exceptions, but a phlebotomist or person drawing blood has an important job. the way a specimen is collected can influence a patient’s lab results. i hope this helps people realize the importance of a properly collected specimen.