Critically-sick Covid-19 patients have blood 95% thicker than normal increasing chances of blood clots: Study
Blood clotting could also explain why some people have low levels of oxygen in the blood and why mechanical ventilators do not help them
The new coronavirus seems to be inducing changes in the blood. A small study found that the blood of a handful of critically sick patients was thicker than usual, explaining why some people develop blood clots - a complication of Covid-19.
The thickening condition is called hyperviscosity and can result when the blood becomes rich in proteins and cells. "Hyperviscosity has been known to be associated with infections, including viral infections, for many years," Dr. Jeffrey Laurence, Professor of Medicine at Weill Cornell Medicine, who was not involved in the study, told MEA WorldWide (MEAWW).
The study involved 15 patients with severe infection. Of them, 14 required breathing support, and kidneys failed in 12 people. All of them had blood thickness that was 95% higher than usual levels. Four patients developed complications due to blood clots. Based on the study, the researchers from Atlanta's Emory University School of Medicine propose that hyperviscosity is strongly connected to disease severity. "However, there is no evidence that hyperviscosity per se contributes to the mortality of such individuals," Dr. Laurence added.
How is infection triggering blood thickening?
All the patients in the study had high levels of a blood protein called fibrinogen. It becomes active during an injury and triggers clots to stop bleeding. Current evidence suggests that the virus attacks blood vessels and damaging its outer lining, resulting in clotting. An increased immune response to Covid-19 may also have a role to play. While fighting the virus, human cells could activate clotting. Blood clotting could also explain why some people have low levels of oxygen in the blood and why mechanical ventilators do not help them. Clots restrict the flow of blood and oxygen to the body. “This is not what you'd expect to see in someone who just has a severe infection. This is really very new," Dr. Laurence told Nature.
What does the study say about treatment?
The Atlanta researchers propose using a treatment that is already used in lowering blood thickness: plasma exchange. "We are actively exploring any beneficial role of therapeutic plasma exchange, highly effective treatment for symptomatic hyperviscosity," the authors wrote in their study
Plasma exchange is similar to how dialysis works. A machine removes affected plasma -- the liquid component of the blood, which contains clot-inducing fibrinogen and other proteins -- and replaces it with good plasma from a healthy individual. This could address the clotting problem, they say. But Dr. Laurence thinks there is limited evidence to suggest hyperviscosity increases death rate. "Therefore, without further evidence, I doubt there is any role for plasma exchange in the correction of the hyperviscosity these Lancet authors found in their severe or critical Covid-19 patients," he said.
For now, doctors treat critical patients with blood-thinning medications. One study found that these drugs slow down clotting and improve survival rates. According to Dr. Laurence, certain medications or anticoagulants that break down fibrinogen will help. "If clotting is uncontrolled in the setting of one type of anticoagulant in a Covid-19 patient, try increasing doses or changing anticoagulants," he said.