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Blood Transfusion Sticks To Rule ‘Less Is More,’ As Too Much Can Overload Circulatory System

blood transfusion
Smaller blood transfusions are no more dangerous than larger ones, and they may even protect against potentially fatal illness. makelessnoise, CC BY 2.0

At the risk of introducing too much blood into patients’ circulatory systems, exposing them to possible infection, surgeons should consider the value of using less blood in their transfusions, a new study argues.

The rule “less is more” doesn’t usually apply to matters of life and death, but researchers from Rutgers University argue there may be a case for it. Smaller infusions not only reduce the immediate risk of death from disease and other illnesses, but keep more people alive over the long-term. Three-year survival rates showed marked spikes among those who received less blood.

“I think it is very reassuring that we have found that using less blood is okay not just from a short-term perspective, but also a long-term perspective,” said Dr. Jeffrey Carson, lead author and chief of the Division of Internal Medicine at Rutgers Robert Wood Johnson Medical School, in a statement.

Carson and a team of colleagues followed 2,016 patients 50 years and older for a period of roughly four years. Half received a more restrictive amount of blood, which was three times less the amount of the other group. All told, the researchers found no difference in risk of increased mortality from cardiovascular disease, cancer, or infection depending on the amount of blood a patient received. Deaths between the two groups fell at 432 for more blood and 409 for less.

The findings bode well for blood banks like the American Red Cross, which experience blood shortages year after year. Last year, for example, the organization issued an emergency request for blood and platelet donation, calling upon people with blood types O-, B+, and A- to step up and donate. As it provides more than 40 percent of the nation’s blood supply, the Red Cross must collect nearly 17,000 pints of blood every day for the estimated 3,000 patients across the country.

Carson also sees the findings as a victory more generally. Blood transfusions can be a tenuous guessing game, as surgeons have to estimate how much blood is necessary given a patient’s current blood pressure and level of blood loss. Larger transfusions leave room for over-donation, which can overwhelm people’s circulatory systems and lead to catastrophic complications.  

“There are definite risks associated with transfusion,” said Carson. “The classic ones are hepatitis and HIV. They are as rare as being hit by lightning, but even so — why give more blood to anyone if you can’t show it benefits them?”

In prior years, the risks of under-donating mostly involved oxygen deprivation to the heart. At the time, the idea was that too little blood meant the heart wouldn’t receive enough red blood cells or nutrients to pump effectively — in essence falling short of the donation’s intended goal. Since then, the theories have been amended to weigh the risks of giving patients too much blood.

Carson, however, emphasizes that both risks are decidedly low. Complications are dire, but don’t often crop up. If anything, he says, the new data motivate a case-by-case analysis of each patient, rather than a reliance on broad patterns.

“It’s a bit hard,” he told Medical Daily. “In the end, we don’t really know because there aren’t large clinical trials that clearly establish what the right threshold is.” The real benefit to the general public is a greater reassurance that, on a long-term basis, blood transfusions are still a viable option and won’t cause more harm or deaths than the causes themselves.

Source: Carson J, Sieber F, Cook D, et al. Liberal versus restrictive blood transfusion strategy: 3-year survival and cause of death results from the FOCUS randomised controlled trial. The Lancet. 2014.

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