Medical Laboratory Professionals' Association of Ontario (MLPAO) Practice Exam

When should the phlebotomist release the tourniquet during blood drawing?

Just before the needle is inserted

Prior to the withdrawal of the last tube

Five minutes after the needle has been removed

As soon as possible after blood begins to flow

Releasing the tourniquet as soon as blood begins to flow is crucial for several reasons. Firstly, keeping the tourniquet on for an extended period can lead to hemoconcentration, which alters the concentration of analytes in the blood sample and can result in inaccurate lab results. This is especially pertinent for tests that measure the levels of substances that may be affected by a change in blood volume or fluid distribution, such as electrolytes, proteins, and waste products.

Additionally, releasing the tourniquet promptly allows for better blood flow dynamics, contributing to a smoother procedure and reducing discomfort for the patient. It also minimizes the risk of adverse effects, such as the formation of hematomas or collapsed veins, which can occur if the tourniquet is left on too long.

The other choices suggest scenarios that would either lead to inaccurate results or increase patient discomfort, hence reinforcing why prompt release upon blood flow is the proper course of action.