There are now more than two dozen Cochrane reviews of high priority topics relevant to COVID-19, which are being kept up to date as new evidence becomes available. In March 2022, we published updated findings on the effects of anticoagulants and we asked lead author, Ronald Flumignan from the Federal University of Sao Paulo in Brazil to summarize the evidence in this podcast.
Mike: Hello, I'm Mike Clarke, Podcast Editor for the Cochrane Library. There are now more than two dozen Cochrane reviews of high priority topics relevant to COVID-19, which are being kept up to date as new evidence becomes available. In March 2022, we published updated findings on the effects of anticoagulants and we asked lead author, Ronald Flumignan from the Federal University of Sao Paulo in Brazil to summarize the evidence in this podcast.
Ronald: COVID-19 typically affects a person’s lungs and airways, but, as well as these breathing problems, about one in six people who go into hospital with COVID-19 may develop blood clots in their veins or arteries. Anticoagulants prevent these clots from forming but they can cause unwanted effects such as bleeding. Some guidelines recommend giving these medicines when people are first admitted to hospital with COVID-19, to prevent blood clots from developing, rather than waiting to see if blood clots develop before treating them with anticoagulants. We wanted to know whether using this prophylactic or preventative approach of giving anticoagulants when people are hospitalised with COVID-19 reduced the number of deaths. We also wanted to know whether these people needed less support with their breathing, still developed harmful blood clots or experienced bleeding or any other unwanted events such as nausea, vomiting, kidney problems or the need for amputation.
We searched for studies that assessed anticoagulants given to people hospitalised with COVID-19 to prevent blood clots which had compared an anticoagulant with another anticoagulant, no anticoagulant or a placebo. Following our most recent search in April 2021, the review now includes seven studies with approximately 16,000 people with COVID-19 who were in either intensive care units, hospital wards or emergency departments. Patients were followed for 15 to 90 days and the studies provided data on deaths, bleeding, blood clots, length of hospital stay and unwanted effects; but there was little or no information on the need for breathing support, deaths related to COVID-19 or quality of life.
Four randomised trials, with nearly 4700 participants, compared people allocated to higher versus lower doses of anticoagulants. These found little to no difference in death rates but people on higher doses were more likely to experience minor bleeding compared to those on lower doses. People who received higher doses of anticoagulants also had reduced pulmonary embolism, which is a blood clot in the lung or blood vessel leading to the lung and slightly increased major bleeding, but there was little to no difference between the doses in time spent in hospital, the rate of deep vein thrombosis or other unwanted events.
Three non-randomised studies, with nearly 11,600 participants, compared people who had, or had not been given anticoagulants. These studies found that people who received anticoagulants had a lower death rate than those who did not receive anticoagulants, but this evidence is very uncertain.
In summary, at this moment, we are very confident that higher doses of anticoagulants do not change the risk of death but do increase the risk of bleeding in people hospitalised with COVID-19. In addition, although our confidence in this evidence is much less, it appears that people who receive anticoagulants may have a lower death rate compared to those who do not receive any anticoagulants. However, these conclusions may change in the future, not least because our searches also found 62 ongoing studies with approximately 35,000 participants and we plan to add the results of these studies to our review when they are published.
Mike: To find out more about the current research evidence and to watch for updates as the results become available from the ongoing trials, you can access the review online. Just visit Cochrane Library dot com and search 'anticoagulants and COVID-19'.