NHA Phlebotomy Certification Practice Exam

Using a small-gauge needle with a large evacuated tube can cause:

1. A hematoma.

2. Petechiae.

3. Hemolysis.

4. Patient discomfort.

The correct answer is: Hemolysis.

Using a small-gauge needle with a large evacuated tube can lead to hemolysis, which is the destruction of red blood cells. The primary reason for this is that a smaller gauge needle has a narrower lumen, causing the blood to move through the needle at a higher velocity. When blood is drawn into a large evacuated tube, the pressure difference can be significant. This rapid flow and pressure can lead to shear forces that damage the red blood cells, resulting in hemolysis. Understanding the mechanics of blood collection helps illustrate this phenomenon. When blood cells are pulled through a narrow passageway at high speed, they can collide with each other and with the walls of the needle, increasing the likelihood of rupture. Hemolysis can lead to inaccurate test results and complications in the sample. This highlights the importance of selecting the appropriate needle gauge for the size of the evacuated tube being used, ensuring both patient safety and the integrity of the sample collected.