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Posted: May 5, 2020 7:25:28 am
Doctors treat Covid-19 patients in an intensive care unit at a hospital in Rome, Italy on March 26.
Another threat from the lung virus that causes Covid-19 has emerged that can cause rapid, sometimes fatal damage: blood clots.
Doctors around the world look at a number of bleeding disorders, from benign skin lesions on the feet, sometimes called “Covid toe” to life-threatening strokes and blockages of blood vessels. Ominously, if dangerous clots are not treated, they can manifest days or months after respiratory symptoms have resolved.
The clotting phenomenon is “probably the most important thing that emerged in the last month or two,” said Mitchell Levy, chief of pulmonary critical care and sleep medicine at Warren Albert School of Medicine at Brown University in Providence, Rhode. Island.
It is not unusual for infections to increase the risk of clotting. The 1918 Spanish flu pandemic, caused by a new strain of flu that killed some 50 million people worldwide, was also linked to downstream damage to clots that could dramatically end life.
Viruses like HIV, dengue, and Ebola are known to make blood cells prone to clump together. The pro-coagulation effect may be even more pronounced in coronavirus patients.
“There is something about this virus that exaggerated it in the nth grade,” said Levy, who is also medical director of the Rhode Island Hospital medical intensive care unit. “We are seeing clotting in a way in this disease that we have not seen in the past.”
The problem is visible in clots, doctors call them thrombi, which form on arterial catheters and patient filters that are used to support kidney failure. More pernicious are clots that impede blood flow in the lungs, causing difficulty in breathing.
Rapid deterioration
This is probably what is causing patients who otherwise seem well to “drop suddenly” and develop severe blood oxygen deficiency, said Margaret Pisani, an associate professor of medicine at the University of Medicine School of Medicine. Yale in New Haven, Connecticut.
The researchers looked at bleeding disorders in Covid-19 patients in China in February, but their severity has become clearer. While doctors thought the vast majority of lung damage was due to viral pneumonia, they are now looking more closely at coagulation.
“When you look at the autopsies now, we’re seeing things we didn’t expect,” said Anthony Fauci, director of the National Institutes of Allergy and Infectious Diseases who is at the forefront of the US pandemic response. Clusters of platelets within blood vessels, or microthrombi, are probably the reason why Covid patients can “deteriorate rapidly and dramatically,” he said in an interview with CNN last week.
Separate studies from France and the Netherlands found that up to 30% of seriously ill Covid-19 patients suffered a so-called pulmonary embolism, a life-threatening blockage in one of the arteries of the lungs. Often this occurs when fragments of blood clots from deep veins in the legs travel to the lungs. In comparison, the prevalence of pulmonary embolism was 1.3% in critically ill patients without Covid-19, according to one study.
Heart attack
Left untreated, large arterial blood clots can put overwhelming pressure on the heart and cause cardiac arrest. Even small clots in the capillaries of lung tissue can interrupt blood flow, undermining attempts to help oxygenate patients with ventilators, said Edwin van Beek, president of clinical radiology at the Queen’s Medical Research Institute at the University of Edinburgh.
In the early 1990s, Van Beek helped develop the D-dimer blood test that is used worldwide to monitor clot formation in patients, including those with Covid-19, and to dose them with heparin and others. anticoagulant medications.
Untreated pulmonary embolism is fatal in one in three cases, and will recur in another third, he said. In 3% to 7% of patients, it will cause pulmonary hypertension, another dangerous complication that can cause fatigue and shortness of breath.
Scarred lungs and clotting-related problems may be a lingering legacy of the pandemic, Van Beek said. Covid-19 survivors who have subsequent difficulty breathing, especially in exertion, might mistakenly believe that it is a recurrence of coronavirus infection, when in fact it may be a “reactivation of the entire clotting problem.”
“I hope to see more of this when we come out of the pandemic,” he said. Patients and doctors alike may not be aware of the risks or possible need for treatment.
Coagulation can occur due to damage to the cells that line the blood vessels that results from both viral infection and the response that causes inflammation of the immune system, said Jean Connors, a hematologist at Harvard Medical School.
“The result is not affected if it is treated properly,” he said. But “people may be dying of undiagnosed pulmonary embolism.”
Hospital workers move a Covid-19 patient off the Montefiore Medical Center Moses campus in New York City on April 7.
Organ damage
Clots can form in other parts of the body, potentially damaging vital organs such as the heart, kidneys, liver, intestine, and other tissues.
Five cases of stroke were treated at the Mount Sinai Health System in Manhattan over a two-week period through early April, doctors reported in the New England Journal of Medicine last week. The patients, who had the coronavirus and were under the age of 50, were treated for large vessel blockages.
It is a rare complication amplified by the “large number of infected patients,” Connors said. New York City has reported about 170,000 Covid-19 cases, including approximately 43,000 hospitalizations.
Puzzling, enlightening
Such findings are “puzzling” on the one hand, “but on the other hand they are illuminating” because they can inform better ways of treating patients, said Fauci, the NIAID leader.
In Italy, the first European country affected by the pandemic, it was after Covid-19 patients died of acute pulmonary embolism and other coagulation-related events that doctors switched to inflammation-blocking treatments, such as tocilizumab, sold by Roche Holding AG as Actemra, said Frank Rasulo, head of neurological care at Spedali Civili University Hospital in Brescia.
Some doctors are starting to see Covid as a less typical respiratory illness and more than dangerous clotting, said Rasulo, who is also an associate professor of anesthesia and intensive care. “That’s pretty scary when you think about it, because we didn’t know what we were dealing with until we were at a later stage.”
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