Introduction
This document provides guidance on the application of tourniquets during blood collection, emphasizing their importance and the impact on blood test results.

Specifications
Essential tools for blood collection include safety needles, multi adapters, blood collection tubes, and tourniquets. A tourniquet is not always necessary if veins are visible, but it aids in making veins more prominent for reliable puncture.

Procedure for Tourniquet Application
1. Place the tourniquet about a hand’s width above the puncture site.
2. Ensure the pulse is still palpable to maintain circulation.
3. Dynamic pressure should ideally be 10 mmHg below diastolic pressure.
4. Tighten the tourniquet away from the patient.

Timing and Effects
Once blood flow begins, loosen the tourniquet. It should not be applied for more than one minute to avoid altering blood test results. Prolonged application changes colloid osmotic pressure, affecting the concentration of substances in the blood.

Impact on Measured Values
High molecular weight substances like bilirubin and cholesterol increase in concentration, while low molecular weight substances like glucose and potassium decrease. These changes can lead to incorrect measurements if the tourniquet is applied for too long.

Conclusion
The tourniquet is crucial for reliable vein puncture but must be used correctly to ensure accurate blood test results. It should not be applied for more than one minute to prevent deviations in measured values.