From the Guidelines
A tight tourniquet during blood collection should be avoided as it can significantly affect laboratory test results, and the most recent guidelines recommend using either no tourniquet or only a light tourniquet during blood collection 1. When a tourniquet is applied too tightly or left on for more than one minute, it causes hemoconcentration, which artificially increases the concentration of cells, proteins, and protein-bound substances in the blood sample. This can lead to falsely elevated results for:
- Hemoglobin
- Hematocrit
- Red blood cell count
- White blood cell count
- Calcium
- Potassium
- Enzymes
- Lipids
- Protein-bound substances To avoid these inaccuracies,
- Apply the tourniquet just tight enough to make veins visible (40-60 mmHg pressure)
- Release it as soon as blood flow is established
- Never leave it on for more than one minute
- Consider releasing and reapplying the tourniquet between tubes for time-sensitive tests
- For certain tests like lactate or ionized calcium that are particularly sensitive to tourniquet effects, a tourniquet-free technique may be preferred, as recommended by the most recent study 1. These precautions ensure accurate laboratory results that reflect the patient's true physiological state rather than collection artifacts, and are in line with the latest recommendations for blood drawing 1.
From the Research
Tourniquet-Related Complications
- Tourniquet use can lead to compartment syndrome, a serious condition that requires immediate attention 2
- Compartment syndrome can result in functional deficiencies, peroneal weakness, and restricted movements of the ankle 2
- Creatine kinase (CK) levels can be a useful adjunct in diagnosing compartment syndrome, and early fasciotomy can help lower elevated CK levels 3
Tourniquet-Related Nerve Injury
- Tourniquet-related nerve injuries (TRNIs) are a rare but feared complication of operative tourniquet use 4
- TRNIs can occur over a wide range of tourniquet application times and pressures, and most patients experience a complete recovery 4
- Surgeons should consider TRNI as a potential complication and understand the methodology for diagnosis and long-term management 4
Tourniquet Removal and Management
- Emergency physicians should be knowledgeable about the initial assessment and management of patients with a prehospital tourniquet in place 5
- A stepwise approach to tourniquet removal includes determining how long the tourniquet has been in place, evaluating for contraindications, preparing for removal, releasing the tourniquet, and monitoring the patient 5
- Tourniquet-induced ischemia-reperfusion injury can lead to local and systemic oxidative stress, inflammatory reactions, and renal function disturbance 6
Protective Therapeutic Interventions
- Propofol, ischemic preconditioning (IPC), and vitamin C may have protective effects on oxidative and inflammatory markers in tourniquet-induced ischemia-reperfusion injury 6
- However, a high dose of N-acetylcysteine may induce kidney injury, and the relationship between biochemical parameters and postoperative clinical outcomes has not been validated 6