Surgery is a risk factor for VTE. As with any surgical procedure, the blood clotting system can be activated as a result of the surgical intervention, and certain surgeries, such as orthopaedic surgery, activate the coagulation system. Coupled with reduced blood flow or ‘stasis’ as a result of being immobile, surgery fulfils the triad of categories that increase the risk of thrombosis.

The figure shows an operation on the brain. This type of surgery—neurosurgery—has a high risk of thrombosis.

The risk of thrombosis can be increased even in the absence of other risk factors, depending on the type of surgery. A risk assessment will be carried out in hospital in order to establish the level of risk and to determine if measures should be taken to reduce the likelihood of a VTE. For some operations, the increased risk of VTE is still present even after hospital discharge. For example, as many as six in ten patients may suffer a DVT after hip fracture surgery in the absence of preventative treatment (known as prophylaxis) [8].