There are many ways to measure the toll of gun violence, from neighborhood homicide rates to the cost of a hospital bill to the number of gunshots a child hears outside her window at night. Now, new research explores how shootings tax a precious human resource: blood.

The study, published this month in Transfusion Journal, found that gunshot patients required 10 times more blood than survivors of other traumas, including car accidents, falls, and stabbing assaults. That blood comes at a price: The authors calculated the average cost of transfusion per gunshot patient to be $11,327. For any other type of trauma patient, the price is about half that: $5,716.

The study is one of the first to assess blood transfusion needs among gunshot patients specifically, and comes amid a scarcity of blood at the nation’s blood banks. The findings offer a blueprint for how hospitals — especially urban trauma centers in cities with high rates of gun violence — can prepare to treat shooting patients.

“We had no idea how much blood was going to support gunshot victims because no one’s ever reported that,” said Steve Frank, a professor of anesthesiology and critical care medicine at Johns Hopkins Hospital in Baltimore, who authored the study along with other Hopkins medical faculty. “We were surprised by the magnitude of the difference in blood use.”

To conduct their research, Frank and his colleagues analyzed 12 years of retrospective data on trauma patients treated at Hopkins. Between 2005 and 2017, the hospital treated 2,672 gunshot patients, who tended to be younger, male, and more severely injured than other trauma patients. Of those, 538 required a blood transfusion. The average transfused gunshot patient received more than 10 units of red blood cells.

Blood is a life-saving commodity that isn’t cheap for hospitals to obtain, store, or deliver to patients. The researchers determined that Hopkins paid between $50 and $500 per unit for forms of blood, ranging from red blood cells to platelets. However, the study estimates the true cost of the blood increased fourfold by the time it was circulating inside a patient.

“There are about 70 steps between the donor and the recipient,” Frank said. These steps include testing the blood for viruses like HIV, transporting the blood from the blood bank to the hospital, and storing it properly.

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This results in a high overall cost of replacing patients’ blood over the course of their hospital stay. Though the average cost of transfusion per gunshot victim hovered just above $11,000, in extreme cases it reached as high as $126,000.

Blood on its own can’t always reverse the damage bullets inflict. In the study, gunshot patients who received a transfusion died about 33 percent of the time. In one instance, a patient wounded in a shooting received 190 units of blood. It still wasn’t enough to save the patient’s life. Besides blood loss or transfusion reactions, patients can die of a multitude of causes, including infections and other complications of their injuries.

Frank said he hopes the findings help hospitals better manage their blood inventories. Major trauma centers like Johns Hopkins tend to keep large quantities of blood, said Frank, but stocking the right amount of blood may be harder for smaller or rural hospitals.

“You don’t want to keep too much blood in the building because it has a limited shelf life and it’ll expire and that wastes blood and money,” he said. “If you have too little inventory then you’re not going to be prepared to treat patients who need massive transfusions.”