Patients with current COVID-19 infection undergoing surgery are 50% more likely to have a venous thromboembolism (VTE) than the general population, a global study has concluded.

And those with recent infection – 1-6 weeks before surgery – are twice as likely to suffer a VTE after an operation, the data from thousands of patients suggests.

The study led by UK researchers also found having a VTE was associated with five-fold increased risk of death within 30 days after surgery compared with patients with no VTE.

Analysis of 128,013 patients, from 1,630 hospitals across 115 countries found that the post-operative VTE rate was 0.5% in patients without SARS-CoV-2; 2.2% in patients with peri-operative SARS-CoV-2 (7 days before to 30 days after surgery); 1.6% in patients with recent SARS-CoV-2; and 1.0% in patients who’d had SARS-CoV-2 infection more than 7 weeks ago.

After adjusting for confounding factors, the research team found that those with peri-operative SARS-CoV-2 were at a 50% higher risk of VTE, those with recent SARS-CoV-2 at a 90% increased risk and those with previous SARS-CoV-2 were at a 70% increased risk.

Writing in the journal Anaesthesia, the team at the NIHR Global Health Research Unit on Global Surgery, Birmingham, noted that in patients with SARS-CoV-2, mortality without VTE was 7.4% and with VTE five times higher at 40.8%.

The study also showed that in patients with pre-operative SARS-CoV-2, ongoing symptoms were associated with an increased rate of post-operative VTE, irrespective of how long before their operation the diagnosis was made.

Pneumonia was also strongly associated with postoperative VTE, possibly due to a combination of SARS-CoV-2-induced pneumonitis and a more difficult post-operative period involving infection, increased disease burden and greater immobility, the researchers said.

Information on the post-surgery prophylaxis regimens and pre-operative anticoagulation was not available to the researchers who called for further research to define the optimal protocols for VTE prevention and treatment for surgical patients in the COVID-19 era.

Co-author Dr Elizabeth Li, a General Surgery Registrar at University Hospital Birmingham, said: “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.”

Study co-author Dr Aneel Bhangu, Consultant Colorectal Surgeon at the University of Birmingham, added: “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.”