London, Aug 25 (IANS): Recent or current Covid-19 infection can increase the risk of dangerous blood clots during surgery, finds a study.

Venous thromboembolism (VTE) -- a combination of deep vein thrombosis and pulmonary embolism -- is a condition in which blood clots form in the veins and has been described as the number one preventable cause of death in hospitalised patients.

The study, published in Anaesthesia, showed that VTEs are 50 per cent more likely to occur in patients with current Covid-19 infection while those with recent infection are almost twice at risk.

Having a VTE was associated with a five-times increased risk of death within 30 days following surgery compared with patients with no VTE, said researchers from the University of Birmingham.

"People undergoing surgery are already at higher risk of VTE than the general public, but we discovered that a current or recent SARS-CoV-2 infection was associated with greater risk of postoperative VTE. Surgical patients have risk factors for VTE, including immobility, surgical wounds and systematic inflammation -- and the addition of SARS-CoV-2 infection may further increase this risk," said Elizabeth Li, General Surgery Registrar at University Hospital Birmingham.

"Increased awareness and surveillance should be considered. At a minimum, we suggest close adherence to routine standard VTE prophylaxis for surgical patients, including the use of anti-clotting medication when bleeding risk is minimal, and increased vigilance and diagnostic testing in patients presenting with signs of VTE, such as swelling in one calf, right sided chest pain and shortness of breath," added Aneel Bhangu, Consultant Colorectal Surgeon from the varsity.

For the study, the team included 1,28,013 patients, from 1,630 hospitals across 115 countries.

Patients were categorised as having VTE within 30 days of surgery. SARS-CoV-2 diagnosis was defined as peri-operative (seven days before to 30 days after surgery); recent (one-six weeks before surgery); previous (seven weeks or more before surgery); or no diagnosis past or present.

Patients with peri-operative SARS-CoV-2 were at a 50 per cent higher risk of VTE and those with recent SARS-CoV-2 at a 90 per cent increased risk. Patients with previous SARS-CoV-2 were at a 70 per cent increased risk of VTE, but this result was of borderline statistical significance.

Overall, VTE was independently associated with 30-day mortality, increasing the risk of death during this period by 5.4 times. In patients with SARS-CoV-2, mortality without VTE was 7.4 per cent and with VTE was again more than five times higher at 40.8 per cent.