Surgical patients who have recently had COVID-19 are more likely to develop potentially fatal post-operative blood clots, a new global study reveals.

Researchers discovered that patients diagnosed with current or previous SARS-CoV-2 are more likely to develop postoperative venous thromboembolism (VTE) than those with no history of COVID infection.

VTE has been described as the number one preventable cause of death in hospitalised patients. In this study, VTE was independently associated with 30-day mortality with 5 times increased risk of death within 30 days after surgery in patients who develop VTEs.

Patients hospitalised with COVID-19 have previously been shown to have a high risk of VTE - between 9% and 26% despite the use of preventative drugs, and as high as 31% in patients within critical care settings. This study confirms an increased risk in patients hospitalised for surgery also.

Led by experts at the University of Birmingham, surgeons and anaesthetists from around the world worked together as part of the NIHR-funded COVIDSurg Collaborative to analyse data from 128,013 patients in 1,630 hospitals across 115 countries. The team today published its findings in Anaesthesia.

The research team is calling for surgeons around the world to be on the lookout for VTE - following routine measures to help prevent the condition occurring, such as using appropriate drugs when bleeding risk is minimal and lowering the threshold for diagnostic testing in patients presenting with signs of VTE.

Routine postoperative care of surgical patients should include interventions to reduce VTE risk in general, and further research is needed to define the optimal protocols for VTE prevention and treatment for surgical patients in the setting of SARS-CoV-2 infection.

Co-author Elizabeth Li, clinical research fellow at the University of Birmingham, commented: “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.
“Most surgical patients have risk factors for VTE, including immobility, surgical wounds and systematic inflammation; the addition of SARS-CoV-2 infection may further increase this risk.”
Unlike medical patients, those people having surgery undergo an operative procedure artificially producing a wound that increases the risk of bleeding and initiates a series of inflammatory responses known to alter haemodynamics and coagulation.

Co-author Mr. Aneel Bhangu, from the University of Birmingham, commented: “The impact of surgery on coagulation and early reports of increased risk of VTE in COVID-19 patients means there is a need to define VTE risk specifically in patients undergoing surgery. This will help clinicians and policymakers around the world construct future systems of identifying and minimising VTE risk in surgical patients with active or prior SARS-CoV-2 infection.

“Routine postoperative care of surgical patients should include interventions to reduce VTE risk in general, but further research is needed to define the best protocols for VTE prevention and treatment in this setting.”

Researchers examined data from adult patients, aged 18 and over, undergoing elective or emergency surgery from any specialty.

They defined four categories of patient: no SARS-CoV-2; peri-operative SARS-CoV-2 (diagnosed seven days before to 30 days after surgery); recent SARS-CoV-2 (diagnosed 1–6 weeks before surgery); or previous SARS-CoV-2 (diagnosed seven weeks or longer before surgery). VTE was defined as either deep vein thrombosis (DVT) or pulmonary embolism (PE).

A positive SARS‐CoV‐2 diagnosis was based on a patient having one or more of the following: a positive PCR test; a positive rapid antigen test; CT scan indicating infection; positive immunoglobulin G or immunoglobulin M antibody test; or clinical diagnosis where no swab test or CT scan were available.

• For further information please contact Tony Moran, International Communications Manager, University of Birmingham on +44 (0)782 783 2312. Out-of-hours, please call +44 (0) 7789 921 165.The University of Birmingham is ranked amongst the world’s top 100 institutions. Its work brings people from across the world to Birmingham, including researchers, teachers and more than 6,500 international students from over 150 countries.
• ‘SARS-CoV-2 infection and venous thromboembolism after surgery: an international prospective cohort study’ – Elizabeth Li and Aneel Bhangu is published in Anaesthesia.

About the COVIDSurg Collaborative

• Before the COVID-19 pandemic, 5 billion people lacked access to surgical care and 143 million more operations per year were required globally. There was already a major global inequity in access to safe and affordable surgery across low and middle-income countries, with an urgent need to expand capacity. This pandemic has acutely worsened that situation and placed a spotlight on the need for change in how surgery is delivered. Launched in March 2020, the University of Birmingham-led COVIDSurg collaborative has provided data needed to support this change in the fastest time frame ever seen by a surgical research group, with data from 150,000 patients across 2000 hospitals collected over the past 9 months.

About the NIHR Global Health Research Unit on Global Surgery

• The NIHR Global Health Research Unit on Global Surgery is based at the University of Birmingham and is co-directed by Professor Dion Morton, a leading colorectal surgeon from the University of Birmingham’s Institute of Cancer and Genomic Sciences, and Professor Peter Brocklehurst, Director of the University of Birmingham’s Birmingham Clinical Trials Unit. It has established international research hubs across a range of low and middle income countries (LMICs) in order to set up pathways to rapidly translate research findings in to evidence-based patient care.

About the National Institute for Health Research (NIHR)

The mission of the NIHR is to improve the health and wealth of the nation through research. We do this by:

• Funding high quality, timely research that benefits the NHS, public health and social care;
• Investing in world-class expertise, facilities and a skilled delivery workforce to translate discoveries into improved treatments and services;
• Partnering with patients, service users, carers and communities, improving the relevance, quality and impact of our research;
• Attracting, training and supporting the best researchers to tackle complex health and social care challenges;
• Collaborating with other public funders, charities and industry to help shape a cohesive and globally competitive research system;
• Funding applied global health research and training to meet the needs of the poorest people in low and middle income countries.

NIHR is funded by the Department of Health and Social Care. Its work in low and middle income countries is principally funded through UK Aid from the UK government.