12:54am Friday 05 June 2020

The life of blood: new truths about transfusions

By UAB Magazine


Blood transfusions are a vital part of modern medicine, but recent research shows that patients who receive fewer transfusions often fare better. These findings have spurred changes in the way blood is used at UAB Hospital.

When a patient gets a transfusion—to replace blood lost during surgery or after a car accident, for example—the blood the patient receives isn’t the same as the blood flowing through that patient’s own body, even if it’s the same blood type, says Marisa B. Marques, M.D., director of the Transfusion Service at UAB and co-chair of the UAB Blood Utilization and Management Committee. That is where the problems start.

Blood Simple

The fluid we call blood actually includes many components, including red blood cells (which carry oxygen), plasma (the liquid portion that carries the red blood cells), and platelets (cell fragments that, among other things, cause blood to clot). Blood donated to the American Red Cross and other collection organizations is separated into these three components for storage. Each has its own use in a blood transfusion.

Because the original plasma that surrounded the red blood cells has been removed, “the red cells are re-suspended in a fluid to keep them ‘alive,’” Marques says. “What is becoming more and more clear is that as these cells sit in a bag in a blood bank for up to six weeks, a lot of things are happening inside.”

Donate Today
UAB Hospital will be holding blood drives on March 15 and March 22-25 at locations across the UAB campus. (Click here for times/locations and to make an appointment.) Donations are always accepted at the American Red Cross UAB Blood Donor Center in UAB Hospital’s North Pavilion, second floor. Call (205) 996-7377 for hours.

By the time the blood cells are taken out of the bank for use in a hospital, “they are no longer the very flexible globules that circulate in our veins and arteries, which are able to go through very narrow capillaries and deliver oxygen everywhere,” Marques says. In fact, banked cells can become so inflexible that they clog the flow of a patient’s own blood in those very narrow places. “So instead of facilitating oxygen delivery to the tissues, what we are actually doing is preventing the patients’ own cells from getting all the way there to deliver oxygen.”

Why didn’t physicians realize this sooner? It’s important to recognize that patients who need blood are the sickest ones, Marques says—and those patients’ primary illnesses often cause the same kind of complications as the bagged blood.

The extent of the problem started to come into focus thanks to a groundbreaking 1999 study, the TRICC (Transfusion Requirements In Critical Care) trial, says Marques. Since then, several other studies among patients who were critically ill or recovering from cardiac surgery “have shown that the ones who received less blood actually seemed to do better in terms of survival and complications such as pneumonias and acute renal failure, stroke, and myocardial infarction.”

UAB pathology, microbiology, and surgery researchers, funded by a $1.47-million grant from the National Institutes of Health, are now gathering specific data on how red blood cell storage time affects blood flow through the capillaries and immune response. Their findings could lead to new therapies to prevent transfusion-related toxicities.

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Blood in, less blood out: Over the past four years, UAB Hospital has steadily increased blood donations while simultaneously lowering the number of transfusions, making UAB a national “poster child” for both blood utilization and collection. Click here to read more about these innovative efforts.

A New Approach

The less-is-more philosophy of blood use is a big shift from what medical students have been taught since 1949, when transfusions started to become routine after their success in combat hospitals during World War II. Until a few years ago, Marques says, the standard was to transfuse two units of blood at a time if a patient’s hemoglobin level dropped to 10 grams per deciliter (gm/dL), then follow with two units at a time as needed. (Hemoglobin is the protein in red blood cells that actually carries oxygen; normal levels vary, but they generally range from 13.8 to 17.2 gm/dL for men and 12.1 to 15.1 gm/dL for women.)

“The new protocol says that patients should not be transfused unless the hemoglobin falls to seven grams per deciliter” in a non-bleeding patient, Marques says. “Even then, they should only get one unit at a time, followed by a reassessment, then one unit at a time again if needed.” Though the patient’s hemoglobin might still be low, Marques says, the patient’s own blood cells will be capable of working a bit harder because they can circulate more freely.

Another concern uncovered in recent research, Marques adds, is transfusion-related immunomodulation, known as TRIM. “All transfusions introduce a number of new antigens into the patient” from the donor, she explains, and that throws off the patient’s immune response. “There are several studies showing that the more transfusions a patient receives, the more likely it is that he or she will have infections in the postoperative period, especially after cardiovascular surgery and cancer surgery.”

At UAB Hospital, blood usage is down 26 percent since 2007, when this new research—and chronic blood shortages—made it clear that a major change in standard procedure was warranted. (See “Blood In, Less Blood Out.”)

No Substitute

The new rules naturally don’t apply in all cases, Marques says. Patients who lose more than 30 to 40 percent of their blood volume in a short period of time, for example, will need a transfusion. “Or when they receive chemotherapy and they are not making any cells, we need to give them something to maintain a certain hemoglobin level.”

Transfused blood may not be the ideal choice for a sick patient, but in specific instances it saves lives, Marques points out. “Blood is a living tissue that keeps flowing, being pumped through our bodies 80 times or more a minute. It is put in a bag and sits in a cold room before being transfused. It’s amazing that it works at all—but without it, many patients would die.”

—Written by Tara Hulen

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