What is the most likely cause of edema resulting from the use of a venous occlusive (VO) tourniquet, relative to normal capillary exchange parameters?

From the Research

The most likely cause of edema resulting from venous occlusive (VO) tourniquet use is increased hydrostatic pressure in the capillaries, as evidenced by the most recent study 1 which supports the concept that tourniquet use leads to temporary and reversible edema. When a VO tourniquet is applied, it blocks venous outflow while arterial inflow continues, creating a pressure imbalance in the affected limb. This disrupts normal capillary exchange parameters by increasing the hydrostatic pressure within the capillaries beyond the opposing oncotic pressure. According to Starling's forces that govern fluid movement across capillary membranes, this elevated hydrostatic pressure forces fluid out of the vascular space and into the interstitial tissues. The continued arterial inflow without adequate venous drainage causes progressive fluid accumulation in the tissues distal to the tourniquet. This process is exacerbated the longer the tourniquet remains in place, as more fluid continues to filter out of the capillaries. Once the tourniquet is removed, normal venous drainage resumes and the edema typically resolves as the excess interstitial fluid is reabsorbed into the circulation and lymphatic system. Key factors to consider include:

• The duration of tourniquet application, as longer durations can lead to greater fluid accumulation and edema 2
• The pressure applied by the tourniquet, as higher pressures can increase the risk of edema and other complications 3
• The individual patient's underlying health status and any pre-existing conditions that may affect their response to tourniquet use, such as lymphedema or vascular disease 1. It is essential to weigh these factors and consider the potential risks and benefits of tourniquet use in each individual case, as supported by the study 4 that highlights the importance of minimizing tourniquet-related ischemic damage. In clinical practice, the use of tourniquets should be carefully managed to minimize the risk of edema and other complications, while also ensuring effective control of bleeding and optimal surgical conditions.