Which analyte is most sensitive to prolonged tourniquet application, leading to falsely elevated values?

Which analyte is most sensitive to prolonged tourniquet application, leading to falsely elevated values?

• A. Potassium
• B. Sodium
• C. Glucose
• D. Creatinine

Answer: (A)

Prolonged tourniquet time concentrates the blood in the limb and stresses cells, which can cause ions and substances to shift from inside cells into the plasma. Potassium is largely stored inside cells, so as cells leak potassium into the plasma during ischemia, the measured potassium rises and can appear falsely elevated. The other analytes are less affected in this specific way: sodium remains relatively stable because extracellular fluid balance is less disrupted by short-term ischemia; glucose tends to fall because cells keep metabolizing it after collection unless the sample is processed quickly or kept iced; creatinine is largely unaffected by tourniquet duration under routine conditions. To minimize this artifact, keep tourniquet use brief, draw promptly, and handle samples quickly after collection.

Prolonged tourniquet time concentrates the blood in the limb and stresses cells, which can cause ions and substances to shift from inside cells into the plasma. Potassium is largely stored inside cells, so as cells leak potassium into the plasma during ischemia, the measured potassium rises and can appear falsely elevated. The other analytes are less affected in this specific way: sodium remains relatively stable because extracellular fluid balance is less disrupted by short-term ischemia; glucose tends to fall because cells keep metabolizing it after collection unless the sample is processed quickly or kept iced; creatinine is largely unaffected by tourniquet duration under routine conditions. To minimize this artifact, keep tourniquet use brief, draw promptly, and handle samples quickly after collection.