California Phlebotomy Certification Practice Exam

What can the technician expect if the tourniquet has been left on a patient for 3 minutes during a potassium, CBC, and glucose test?

1. Low potassium level

2. Normal glucose level

3. High potassium level

4. Low CBC count

The correct answer is: High potassium level

Leaving a tourniquet on a patient for an extended period, such as three minutes, can lead to changes in the blood sample being drawn. When a tourniquet is applied, blood flow to the veins is restricted, which can cause an accumulation of certain substances in the blood. In the case of potassium, prolonged tourniquet application can result in hemoconcentration, where the concentration of potassium in the blood increases due to the restriction of blood flow. This increase is primarily because the potassium, which is normally contained within the cells, will diffuse into the plasma when the blood flow is impeded, thereby raising the potassium level in the serum sample collected. Understanding this physiological response is critical for accurate laboratory results, especially for tests involving potassium, as elevated potassium levels can lead to serious health implications and misinterpretations if the sample is not processed correctly. Additionally, while glucose and CBC results might be affected, the predominant concern and notable effect from prolonged tourniquet application is significantly seen in the potassium levels, leading to the conclusion that a high potassium level would be expected.