Venous thromboembolism (VTE) is a condition in which dangerous blood clots form in the veins and has been described as the number one preventable cause of death in hospitalised patients. 

New research published in Anaesthesia (a journal of the Association of Anaesthetists) shows that VTEs, a known complication of surgery, are 50 per cent more likely to occur in patients with current COVID-19 infection and almost twice as likely in those with recent infection. The study also found having a VTE was associated with five times increased risk of death within 30 days following surgery compared with patients with no VTE. 

The postoperative VTE rate was 0.5 per cent (666/123,591) in patients without SARS-CoV-2; 2.2 per cent (50/2317) in patients with peri-operative SARS-CoV-2; 1.6 per cent (15/953) in patients with recent SARS- CoV-2; and 1.0 per cent (11/1148) in patients with previous SARS-CoV-2. 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 (319/4342) and with VTE more than five times higher at 40.8 per cent (31/76). 

The authors note an important limitation to the study: that information on prophylaxis regimens for these blood clots in the veins or pre-operative anti-coagulation to prevent them was not available. As a result, they say that “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”.

The study was delivered by the UK-led GlobalSurg-COVIDSurg Collaborative. This global collaboration of over 15,000 surgeons included Fellows and Trainees from the Royal Australasian College of Surgeons who contributed to teams from 43 hospitals in Australia and 11 in New Zealand. Overall, data was collected from over 140,000 patients who underwent surgery during October 2020, over 5,000 from Australia and Aotearoa New Zealand. 

The Collaborative has recently been awarded the Guinness World Record for the ‘most authors on a single peer-reviewed academic paper’. This highlights the scale of this global partnership, which aims to contribute the understanding of COVID-19 and help to save as many lives as possible around the world.

The Collaborative has previously published analyses of this dataset that demonstrate an increase in perioperative morbidity and mortality for patients with SARS-CoV-2 and evidence of particular benefit from vaccination in this setting.

The first publication, also in Anaesthesia, found that perioperative risk is increased for patients undergoing surgery within 6 weeks of SARS-CoV-2 diagnosis, and longer for those who remain symptomatic. These findings were consistent across both low-risk (age < 70 years, ASA physical status 1–2, minor surgery) and high-risk (age ≥ 70 years, ASA physical status 3–5, major surgery) sub-groups and prompted us to advise delaying surgery for those with SARS-CoV-2 infection whenever possible. 

Our study modelling the benefit of COVID-19 vaccination, published in BJ found that when compared to people of the same age the benefit of vaccination was greater for people needing surgery, particularly cancer surgery. These findings were consistent across all settings regardless of community infection rates.

Aotearoa New Zealand study lead Chris Varghese, Medical Student, University of Auckland, 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. This adds to our previous work that has found that people with SARS-CoV-2 infection have higher rates of perioperative mortality and morbidity and receive even greater benefit from vaccination.” 

Co-author Dr Deborah Wright, Consultant Surgeon and Senior Lecturer, Dunedin School of Medicine commented: “This publication is the latest from this huge, international collaboration conducted by medical students, trainees, and specialist surgeons around the world. It has quickly produced critical, high quality, evidence that is helping to guide the care of people needing surgery. This is the second paper produced by the group that highlights the additional risks for people who need surgery and adds to our previous work demonstrating the particular benefit of vaccination in this setting. We encourage everyone in our communities to be vaccinated as it becomes available.”