COVID-19 patients at higher risk of blood clots after surgery, study shows

Blood clot in vein
Blood clot in vein

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Venous thromboembolism (VTE), a dangerous complication of surgery, is 50% more likely to occur in current COVID-19 patients and nearly twice as likely in those with recent infection, according to an international study yesterday in Anaesthesia.

The researchers also found that this type of blood clot, the top cause of preventable death in hospitalized patients, poses a fivefold increased risk of death in the first 30 days after surgery relative to patients without VTE (pulmonary embolism or deep vein thrombosis).

The prospective cohort study, conducted by the GlobalSurg-COVIDSurg Collaborative, involved 128,013 adult patients undergoing surgery at 1,630 hospitals in 115 countries. COVID-19 diagnosis was defined as perioperative (7 days before to 30 days after surgery), recent (1 to 6 weeks before surgery), previous (7 or more weeks after surgery), or no past or current diagnosis.

Of all patients, 3.5% had a COVID-19 diagnosis, 46.2% were men, 73.5% were American Society of Anesthesiologists (ASA) physical status 1 or 2 (no or mild systemic disease), and 16.0% smoked.

Relative to patients without COVID-19, those with perioperative coronavirus were older (28.2% vs 21.3%), more often had an ASA physical status of 3 to 5 (meaning severe systemic disease) (39.6% vs 26.2%), more often underwent emergency surgery (58.4% vs 29.5%), and had more underlying illnesses.

Risk 90% higher in those with recent COVID

The rate of postoperative VTE was 666 of 123,591 patients without COVID-19 (0.5%), while it was 50 of 2,317 (2.2%) in those with perioperative COVID-19, 15 of 953 (1.6%) in those with a recent coronavirus infection, and 11 of 1,148 (1.0%) in those with a previous infection.

After adjusting for confounding factors, patients with perioperative COVID had a 50% higher risk of VTE, while those with a recent case were at a 90% increased risk. Those with a previous infection had a 70% higher odds of VTE, although this finding was of borderline statistical significance.

The overall postoperative death rate was 1.7%, and VTE was strongly tied to 30-day mortality (odds ratio, 5.4). VTE had an independent link to death within the first 30 days after surgery, pushing the risk of death during this time up 5.4-fold. COVID-19 without VTE carried a 7.4% risk of death (319/4,342), which rose to 40.8% (31/76) (more than five times higher) when VTE was involved.

Patients with preoperative COVID-19 and ongoing symptoms had an increased incidence of VTE compared with those who were asymptomatic or whose symptoms had resolved (4.6% vs 0.8%). This finding persisted after stratifying patients by timing of COVID-19 diagnosis and in symptomatic patients with a coronavirus diagnosis 7 or more weeks before surgery compared with those who were asymptomatic or whose symptoms had resolved (5.7% vs 0.7%).

Research needed on optimal prevention

VTE occurs in 9% to 26% of hospitalized COVID-19 patients and in 21% to 31% of coronavirus patients in critical care settings, despite the administration of preventive therapies, according to the authors.

"People undergoing surgery are already at higher risk of VTE than the general public," coauthor Elizabeth Li, PhD, of the University of Birmingham in England, said in an Association of Anaesthetists of Great Britain and Ireland news release. "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.”

Preliminary guidance for COVID-19 patients undergoing surgery has been mixed, with some recommending no change in practice, and others suggesting increased doses and duration of therapies to minimize risk, the researchers noted. "However, such regimens are associated with serious bleeding risks," they wrote. "Determining the optimal VTE prophylactic regimen for patients with moderate and severe COVID-19 is an active area of research."

Coauthor Aneel Bhangu, MBChB, PhD, of the University of Birmingham, said that increased awareness and surveillance of VTE in COVID-19 patients are needed to prevent it. "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," he said.

The authors cautioned that data on VTE- or clot-preventing therapy in COVID-19 patients were not available. "Further research is needed to define the optimal protocols for VTE prophylaxis and treatment for surgical patients in the setting of SARS-CoV-2 infection," they said.

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