You never know when you may need a blood transfusion. Transfusions occur when a blood from a donor is infused into a patient. This usually happens when certain components of the patient’s blood, such as red blood cells or platelets, become too low. 

“Transfusions are as safe now as they’ve ever been in the era of modern medicine,” says Yale Medicine pathologist Jeanne Hendrickson, MD, associate director of Yale Medicine's Blood Bank. While blood transfusions are life-saving treatments, like all medical procedures, they come with some risks. Physicians and staff at Yale Medicine take additional measures to ensure safe transfusions.

There are many reasons why a blood transfusion may be necessary for a patient. Some examples include surgical operations, trauma accidents, complications from cancer, or chronic medical conditions. Some medications, such as chemotherapy, can diminish the body’s ability to produce blood. In these situations, blood transfusions can be used to increase the concentrations of blood cells and of the blood's ability to clot.

"Blood, blood components, and coagulation factors are safer today than they have ever been at any point in our lifetimes," Dr. Hendrickson says.

Blood is obtained from recognized blood suppliers that follow national guidelines for donor screening and testing. All donated blood is tested for specific infections, including HIV and hepatitis, and many other diseases.

Recently, the York Street and Saint Raphael hospital campuses have begun to introduce a new “pathogen-reduced” platelet product called Intercept. The Intercept product has been used in Europe for over 20 years, and the U.S. Food and Drug Administration (FDA) approved this pathogen reduction process two years ago. The Intercept platelets are generated from the same donor pool used to provide other platelet products, and are then treated in a way that reduces the chance of contamination or disease.

The most common reactions to a blood transfusion are:

• Allergic reactions: may include breaking out in a rash for hives
• Febrile reactions: these may include fevers and chills

Both reactions are generally mild and resolve on their own or with supportive treatment. Although the rash or hives can be uncomfortable, they generally do not pose a serious threat to the patient's health. 

Another type of reaction that is common, but often underreported, includes:

• Transfusion-associated circulatory overload (TACO): this can cause excess fluid in the lungs, a condition called a pulmonary edema. 

TACO usually happens in patients who receive a large amount of a transfused product in a short time period, or in those with cardiovascular or renal disease. 

If a transfusion reaction is suspected, then the Yale Medicine Blood Bank performs testing to assess whether the patients may require additional therapies or whether modifications to future transfused blood products may be necessary.

"An allergic transfusion may occur because a patient is allergic to a protein in the donor's blood," Dr. Hendrickson says. Other potential allergens include preservatives used to keep the donated blood fluid stable or used to sterilize the plastic bags that store the blood. 

"Febrile reactions are thought to be due to cytokines contained in blood product unit or due to substances in the transfusion recipient that react with donor antigens, though these reactions are not fully understood," Dr. Hendrickson explains. If a spike in a patient's temperature is observed during the transfusion, then the procedure is stopped to investigate. 

While it's not possible to completely prevent blood transfusion reactions, Yale Medicine works with its blood suppliers to take steps to reduce the likelihood of these occurring.

Patients with allergic reactions are often treated with antihistamines, medications that can stop allergic symptoms. Patients who experience febrile reactions are usually treated with acetaminophen, an over-the-counter medication that can reduce fevers.

Reactions generally occur either during the transfusion or four to six hours after the transfusion is complete; some may occur later.

All patients who receive a transfusion at Yale Medicine leave with a telephone number to call and specific instructions to follow if they think that they are having a reaction to the transfusion after leaving the hospital or clinic.

"We constantly educate staff and have transfusion evaluation reporting built directly into EPIC (the electronic health records system)," Dr. Hendrickson says. "For every reaction that is reported, our transfusion medicine physicians evaluate the investigation performed by the blood bank and give a recommendation to the clinical team for future situations." 

Physicians and staff work with blood suppliers to ensure that the safest possible blood is used for transfusion. They also strictly observe established and nationally mandated guidelines for pre-transfusion safety checks and compatibility testing.

Physicians and the staff at Yale Medicine recently implemented an additional computer-based safety check. This provides an added level of security that should increase the confidence of patients receiving transfusions. 

Another important safety aspect that makes Yale Medicine's blood banks unique is that all platelet blood products now undergo a recently approved FDA process that eradicates any new or emerging infectious diseases -- such as the Zika virus -- from donor blood.