KANSAS CITY, Mo. — On the day the Boston Marathon bombing transfixed the world, Mark Watkins of suburban Kansas City, Mo., lay face to face with a crisis of life, death and faith of his own.

Little could he guess that, in the end, it would be a controversial product sent from a terrorized city that would save him.

“Obviously, we’re thrilled,” Watkins’ son, Rocky, 30, said recently, from his father’s hospital bedside. “Not only were they able to save his life, but they did it while they respected his beliefs.”

Watkins’ drama began April 15. The night that Boston went into terror lockdown, the 51-year-old husband and father had been in church with his wife, Nellie, when his skin turned white. His body crashed.

He was rushed to the hospital, where doctors discovered he was slowly but surely bleeding to death internally.

The cause was unknown. Maybe it was a ruptured vessel or a bleeding ulcer, which he had suffered before. But without oxygen-rich blood, his body was suffocating. He needed surgery. He needed to be stabilized. He needed blood.

The problem: Watkins is a Jehovah’s Witness.

His faith allows for the medical use of non-blood alternatives and, for some, reinfusion of their own blood or some blood fractions. But the majority of Jehovah’s Witnesses hold tight to what they say is the Bible’s command to “keep abstaining from ... blood.”

Given the restriction, Nellie Watkins said, their hospital delivered grave news.

“We were told that there was nothing else they could do for us,” she said. “They said he might not make it through the night.”

Then a call went out to the University of Kansas Hospital, where trauma surgeon Charlie Richart, 53, performs what is known as “bloodless” surgery. Richart, who has been at the hospital three years, has treated Jehovah’s Witnesses for close to 27 years and recalled the sad frustration of losing patients because he could not give them blood.

“I could not save them because they bled to death,” he said.

Somewhat of a misnomer, bloodless surgery actually refers to the methods doctors use to reduce the amount of outside blood transfused into the body during surgery or the amount of blood lost during an operation.

Some of the methods are most effective when there is time to plan a surgery. Doctors can collect and store volumes of a patient’s own blood before surgery, or dilute the patient’s own blood and reinfuse it during a procedure. After surgery, medicine can be given to boost the bone marrow’s production of blood.

In 2010, bloodless surgery made headlines in Kansas when Mary Stinemetz, a Jehovah’s Witness who was then 64, sued the Kansas Health Policy Authority, which administers the state’s Medicaid program. Stinemetz had sought a bloodless liver transplant at the University of Kansas Hospital, which could not guarantee a bloodless procedure at that time.

She wanted the state to pay for the procedure in Nebraska, arguing that in refusing the transplant Kansas was violating her First Amendment rights to exercise her religion. She won her case a year later, but by then she was too sick to be put on the transplant list. She died last October.

In Watkins’ emergency, time was short.

“When he got here,” Richart said of Watkins, “he was way behind the eight ball. His foot was on a banana peel and his other was 6 feet deep in the grave.”

As soon as the University of Kansas Hospital received the call from the other hospital, Richart thought of Hemopure, a product produced by OPK Biotech of Cambridge, Mass., that holds oxygen just like human blood, but which itself is not blood. Instead, it is a blood substitute, also known as an HBOC, for hemoglobin-based oxygen carrier. The solution is made from purified bovine — meaning cow — hemoglobin, which is the molecule in blood that carries oxygen to the tissues.

Over the years, the product has been used successfully worldwide to save the lives of some Jehovah’s Witnesses in crisis, although the company won’t reveal the exact number.

In Watkins’ case, it was also the only resort.

Ten units of the blood substitute were on the way, each unit slightly smaller than a can of soda.

Watkins received four units late at night on April 17 and two more over 12 hours on April 18. The company would later send 10 more units while the Boston police searched for the marathon bombers.

Watkins stabilized. In the late evening of April 19, Watkins went into surgery, where Richart and his team found bleeding polyps, which Richart thinks may have contributed to the loss of blood. Watkins was then stable enough to do other tests.

“I’m just real appreciative. It was scary,” Watkins said.