Certified Medical Assistant (CMA AAMA)Procedures, Examinations and DiagnosticsMedium
A medical assistant is performing a venipuncture and leaves the tourniquet in place for over two minutes while searching for a vein. What effect is this most likely to have on the specimen?
- AClotting within the collection tube
- BDilution causing falsely decreased glucose
- CHemoconcentration causing falsely elevated results
- DHemolysis causing falsely decreased potassium
Show answer & explanationAnswer & explanation
Correct answer: C. Hemoconcentration causing falsely elevated results
Prolonged tourniquet application (over one minute) causes fluid to shift out of the vessel into surrounding tissue, concentrating larger molecules, cells, and protein-bound analytes in the blood, leading to falsely elevated results (hemoconcentration).
Why the other options are wrong
- A. Clotting relates to inadequate mixing of anticoagulant tubes, not tourniquet duration.
- B. Dilution is not caused by tourniquet application; it results from IV fluid contamination.
- D. Hemolysis is caused by trauma to cells (small needle, vigorous mixing), not tourniquet time.
Tourniquet Time Limit
A tourniquet should not remain on the arm longer than one minute to avoid hemoconcentration, which can skew laboratory results.
- Release tourniquet within 1 minute of application
- Prolonged use raises protein, cellular, and enzyme levels falsely
- If vein is hard to find, release and reapply after 2 minutes
Memory trick: 'One minute max, or the blood gets stacked' (hemoconcentration).