TORONTO -- An increasing number of COVID-19 patients are developing fast moving, potentially life-threatening blood clots that may lead to stroke or limb amputation in some cases.

Doctors on the front lines say these “substantial” clots are forming in veins not normally affected by critical illness and are difficult to break down even with the use of blood thinners, presenting a new challenge in treating and understanding the novel coronavirus.

“Many patients infected with COVID are getting large blood clots in veins and arteries, but also very small blood clots even in the smaller blood vessels of the lung, of the kidney, of the brain,” Dr. James Downar, specialist in critical and palliative care at The Ottawa Hospital, told CTV News.

"This is something that we really haven't seen before and this is one of the unique factors of COVID that we're still trying to figure out.”

A recent high-profile case has shed light on the mounting concerns surrounding the side effects of the disease.

Canadian Broadway star Nick Cordero had his right leg amputated April 20 after a severe case of COVID-19 caused blood clots in his leg. Cordero, a previously healthy 41 year old, remains in a medically induced coma, relying on several machines to support his heart, lung and kidney functions.

"We took him off blood thinners but that again was going to cause some clotting in the right leg,” his wife, fitness star Amanda Kloots wrote on Instagram prior to the operation.

According to his family, Cordero developed a dry cough and experiencing difficulty breathing in late March. He was admitted to the intensive care unit at Cedars-Sinai Medical Center in Los Angeles on March 31 and was placed in a medically induced coma April 1.

Despite being cleared of the COVID-19 infection, he remains on a ventilator and has since undergone a pacemaker operation to help regulate his heart.

Speaking to CTV News from Cordero’s hometown of Hamilton, Ont., his mother said although he is slowly being weaned off of the life-supporting machines and medication, his doctors may still put a tracheotomy in to help him breathe.

"Why did Nick – who is a healthy 41-year-old male -- why did he get hit with this?” his mother, Lesley, said.

“And if it hadn't been for the secondary infection, I strongly believe Nick would be getting out of the hospital now so it's a great unknown, we don't know.”

Due to ongoing travel restrictions, she is unable to travel to the U.S. to support her son’s family or see her 10-month-old grandson, Elvis. Cordero’s wife is also unable to visit her husband in hospital, despite having tested negative for the virus.

“We can't be with him. We can't get down there we can't help support his wife or his child. We can't be in the ICU holding him or talking to him,” his mother said.

“I want Nick to regain consciousness, that's what we're all hoping for now. We need him to come to.”


Though severe, the side effects Cordero has experienced are becoming more prevalent in COVID-19 patients here in Canada, Downar says.

“What seems to be happening is the body is clearly making a lot more of the clotting factors, the proteins, that ultimately work to build clots when they're activated,” the critical care specialist explained.

“We’ve seen certainly people who have had clots forming, and quite substantial clots forming in veins where normally you don't see clots forming in critical illness.”

Downar says doctors are recording clotting levels that are much higher than seen in other conditions, leading to unique challenges in regards to the speed of which clots form.

“Part of the problem is by the time it happens, if it’s a clot that blocks an artery, unless you’ve noticed it almost straight away, the limbs can't usually last very long. Human tissues can't last that long without oxygen,” he said.

“Even in the best ICUs in the world, with the best trained staff, it's very possible that a blood clot, a significant blood clot that completely blocks the flow of blood through an artery, would lead potentially to an amputation.”

Amputation isn’t the only emerging threat to patients. Last week, doctors in New York reported a seven-fold increase in incidences of sudden stroke in young, otherwise healthy COVID-19 patients.

“Most of these patients have no past medical history and were at home with either mild symptoms (or in two cases, no symptoms) of COVID,” Dr. Thomas Oxley, a neurosurgeon at Mount Sinai Health System in New York, told CNN.

At least one patient noted in the study died, while others are recovering in rehabilitation facilities, intensive care or in the stroke unit.

Downar says a number of studies are now underway to see if COVID-19 patients should be treated with therapeutic doses of blood thinners in the hope that it might improve their outcomes.

“It also speaks to the need for further research and understanding why COVID seems to be having this effect on the blood clotting system, in the hope that we can develop better treatments to stop it from happening again,” he noted.


Because Cordero lives in the U.S., his family started fundraising for his medical care and likely long rehabilitation. A GoFundMe campaign has raised over $438,000 for his care so far.

Kloots has also begun rallying support for her husband on Instagram, using the hashtag #WakeNickUp to encourage people to dance to his song “Live Your Life.”

“At some point every day I go to [Cedars-Sinai Medical Center] and stand outside the hospital. I talk to Nick, I pray, I play his song and I sing to him,” Kloots wrote on Instagram earlier this week, thanking staff at the hospital.

“It’s the closest I can get to him on a daily basis.”