NHA Phlebotomy-Technician Exam - Topic 1 Question 9 Discussion

The maximum recommended tourniquet application time before results may be affected is 60 seconds. A tourniquet is applied to increase venous filling and make the vein easier to locate and access, but prolonged application causes venous stasis and hemoconcentration. When blood remains trapped below the tourniquet too long, fluid shifts from the vascular space into surrounding tissue, concentrating cells, proteins, and protein-bound analytes. This can falsely elevate results such as potassium, calcium, proteins, and other chemistry values. It can also increase patient discomfort and make the collection more difficult. Thirty and forty-five seconds are acceptable but are not the maximum allowed time. Ninety seconds is too long and increases the risk of altered test values. Correct practice is to apply the tourniquet only long enough to select the site and establish blood flow, then release it promptly, especially before removing the needle. Reference topics: Routine Blood Collections; tourniquet application; hemoconcentration; venipuncture preanalytical variables.

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