Welcome to the newest ADVANCE for Nurses online column, designed to address all your questions about lab tests, specimen collection, interpreting results and more.
This time, Ask the Lab responds to readers' questions and concerns regarding hemolyzed blood specimens:
Question No. 1:
I often find that potassium comes back "hemolyzed" or cannot be run, despite a large sample. What is the cause of this and what can be done to insure a better sample?
Question No. 2:
I have always wondered why my lab draws have come back hemolyzed. I start my IV and do not use a vacuum tube sytem device to draw labs. I allow the blood to drip into the tubes and then recap the tubes (micro tubes, no vacuum) and send them to the lab. Is it my imagination, or can blood hemolyze using this method?
Laboratory testing delays due to hemolysis are a source of frustration for nursing and the laboratory. More importantly, delays in providing timely patient care become the critical issue here.
When a blood sample is hemolyzed, it means the red cells have ruptured to the extent that they impart a pink/red color to the blood plasma, which is normally pale yellow.
By comparison, "gross hemolysis" describes a plasma sample as intensely red as cherry-flavored gelatin.
The red color is due to hemoglobin. Its presence indicates that other contents of the cell have also been released into the blood plasma.
Red cells are fragile, and subjecting them to mechanical stress causes a portion of them to rupture. Since there are 4 to 6 million red cells per milliliter of blood, the effects of cell destruction are significant.
A few metabolic disorders, as well as a severe transfusion reaction, can cause hemolysis; however, these situations are rare.
Hemolysis wreaks havoc with a number of laboratory tests, especially potassium.
When this "intracellular cation" spills out into the blood plasma, erroneously elevated readings occur.
Hyperkalemia and hypokalemia, both potentially life threatening, can be masked by the presence of hemolysis.
Certain enzyme results are also altered. For example, both CK and LDH can be falsely elevated. With some lab methods in use today, cardiac troponin results are invalid.
The red color causes problems in the detection of bilirubin, and coagulation testing might not be possible. (Hemolyzed blood bank specimens are refused.)
The laboratory is responsible for insuring the validity of test results, and, consequently, the lab should have a uniform specimen-rejection policy. Exceptions to this policy should be few, e.g., neonates and exceptionally difficult draws.
Studies have shown that the primary reason for hemolysis is how the blood is drawn.
Hemolysis rates of 7 percent to 12 percent are noted when blood is drawn through an IV catheter. This is common practice in emergency departments (EDs), for example. With a straight needle stick, hemolysis rates are less than 2 percent.
The second-most common cause of hemolysis is taking the specimen from a site other than the antecubital vein. A number of other causes exist, including small needle gauge, improper filling and mixing of tubes, and specimen transport conditions.
Consequently, the use of smaller gauge IV catheters in a distal arm vein to obtain blood prior to starting an IV solution can lead to hemolysis. This is common practice, as it eliminates additional patient discomfort with one more needle stick.
Hemolysis is a roadblock to the initial assessment of ED patients. This assessment should be made within 60 minutes, according to JCAHO.