Difficulty: Medium

Average Score: 60%

Hemoconcentration of a venous blood sample is most often caused when

Rationale

The tourniquet is in place for more than 2 min.

When a tourniquet is applied for an extended period, it can lead to hemoconcentration, which is the increase of the concentration of blood components due to the reduction of plasma volume. This occurs because the prolonged pressure causes fluid to shift out of the vascular space, concentrating cells and other solutes in the remaining plasma.

A (the site is prepped with povidone iodine.) YOUR ANSWER

Using povidone iodine for site preparation does not affect the concentration of blood components. Its primary role is to disinfect the skin prior to venipuncture, thereby preventing infection. It does not influence the plasma volume or the cellular concentration in the blood sample.

C (the specimen is not refrigerated within 30 min.) YOUR ANSWER

Failure to refrigerate a blood specimen within 30 minutes may lead to changes in certain analytes over time, but it does not cause hemoconcentration. Hemoconcentration is specifically related to the physical condition of the blood during collection, particularly the duration a tourniquet is applied, rather than the temperature at which the sample is stored afterward.

D (the needle is removed before the tourniquet.) YOUR ANSWER

Removing the needle before the tourniquet is released may lead to complications such as bleeding or hematoma formation, but it will not cause hemoconcentration. Hemoconcentration is a direct result of prolonged tourniquet application, and removing the needle does not alter the concentration of blood components.

Conclusion

Hemoconcentration is primarily caused by the duration a tourniquet is applied, with more than 2 minutes being a critical threshold. Other factors listed, such as site preparation methods and specimen handling post-collection, do not impact the concentration of blood components in the same direct manner. Understanding the effects of tourniquet application is crucial for obtaining accurate laboratory results, emphasizing the importance of proper phlebotomy techniques.

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