Blood Conservation
Importance for Cardiac Patients | Blood Use in Cardiac Surgery | Risks of Blood Use | Minimizing Blood Use | Success of Blood Conservation
Why blood is particularly important in cardiac patients
Hemoglobin in red blood cells is the molecule responsible for transporting oxygen through the bloodstream from the lungs to all the tissues of the body.
A normal hemoglobin (or hematocrit) level is important for maintaining the ability to deliver enough oxygen to meet the body's needs.
A low hemoglobin level (anemia) forces the heart to generate a higher output to achieve adequate oxygen delivery. This may not always be possible, especially in the presence of cardiac anomalies or dysfunction.
There are components of blood which are crucial in the complex clotting mechanisms. It is particularly important that this system works properly at the time of surgery to prevent bleeding complications.
Return to Top
When blood is used in cardiac surgery
Blood products may be administered to patients before, during, or following surgery. Before an operation, blood products are used to treat anemia in order to help stabilize cardiac function, especially in newborns with complex defects.
In the operating room, blood is used to prime the cardiopulmonary bypass machine so the patient's own blood volume won't get excessively diluted when heart-lung bypass is used.
Following surgery, blood may be transfused to replace losses from chest drains or from blood sampling required for tests. In all cases, blood products are used judiciously with the goal to maintain optimal oxygen delivery to the tissues with minimal stress on the heart's function.
Return to Top
Risks associated with blood use
Blood product use has the potential for a number of complications. As with any medication, side effects may be present, and in addition, blood is technically similar to a transplant in that it is a form of tissue from another person.
Transmission of infectious agents is often the risk that most people are concerned about. All blood products are tested for various infectious agents such as the AIDS and hepatitis viruses.
Despite testing, there is still a small risk of transmitting these diseases with transfusions. The risk of transmitting the AIDS virus is as low as one in a million, the risk of hepatitis one in 100,000.
Immune-mediated transfusion reactions are actually the most common side effect of blood use, though most reactions are mild, consisting of little more than a fever. Serious, immune mediated transfusion reactions are extremely rare (about one in 500,000).
Transfusion of blood products may affect electrolyte levels in the body, particularly in infants. There is increasing evidence that blood transfusion has an impact on a patient's immune system that could increase the risk for infections or neoplasm.
Despite the number of potential side effects, the overall risk of blood transfusion is far outweighed by its benefits when used judiciously.
Return to Top
Minimizing blood use in cardiac surgery patients
There are a number of strategies that are routinely employed which can be very successful in allowing us to minimize the number of blood exposures a patient receives during their hospitalization.
In some instances, open-heart operations may even be possible in small children without the need for any blood use at all.
Maintaining a patient's own ability to manufacture new blood cells is an important factor in the long-term management of children with heart defects. Good nutrition along with iron and vitamin supplementation are the cornerstones of this strategy.
Blood unit exposures can be minimized over the course of a hospitalization by ordering blood products wisely. For example, if requested, a single adult unit of blood can be split into multiple "pedi-packs" that can be used over a period of days or weeks allowing multiple transfusions from just one donor exposure.
Good surgical technique to minimize blood losses is probably the single most important factor in minimizing blood use around the time of an operation.
Special medications are used during some high-risk operations that maximize the blood's clotting abilities, and special cardiopulmonary bypass circuit components are sometimes employed to minimize the body's inflammatory response to heart-lung bypass.
Other techniques maximize the conservation of a patient's own blood cells. Using smaller-sized cardiopulmonary bypass circuits in smaller patients decreases the dilutional anemia that occurs with heart-lung bypass and may allow the pump to be primed with a blood-free solution.
Most children are not big enough to pre-donate their own blood for surgery, but a form of autologous donation called "intraoperative sequestration" is performed regularly at some centers.
"Cell-saver" suction devices that can recover shed blood from the operative field, wash it, and process it for immediate retransfusion are used in cases where a higher than usual amount of bleeding is anticipated.
Finally, ultrafiltration, a form of artificial kidney device, is used routinely in most pediatric centers as a component of the heart-lung bypass machine.
In addition to other benefits, ultrafiltration allows rapid removal of crystalloid fluid from the patient and bypass circuit at the end of an open-heart operation to allow transfer of most of the blood cells in the cardiopulmonary bypass circuit back into the patient at the completion of the operation.
Finally, we have begun to use a drug called "EPO", short for erythropoietin, to help the body make more blood cells before surgery. Although we and others have used this drug on selective patients in the past, we are now testing the efficacy of this medicine for more routine use. Our goal is to increase the blood count of the patient before surgery. EPO treatment is effective only when done over several weeks. We can not use this for emergency surgeries or situations when there is little time left before surgery. Also, the child has to be on iron supplements during the EPO treatment.
Return to Top
How successful are blood conservation methods?
Over the past 5 years, Cincinnati Children's has found that initiation of blood conservation methods has resulted in significantly less blood loss following surgery, due to better blood clotting function.
These methods have also led to a decrease in the number of blood product exposures to one fourth of prior rates in selected groups of patients.
In patients undergoing atrial septal defect (ASD) closure, no blood products were used during the entire hospitalization for any patient over 20 kg. and for over 75 percent of patients between 10 and 20 kg.
These strategies can even be successfully applied to some of the most complex newborn cardiac operations performed. For example, in newborns undergoing arterial switch operation for transposition of the great vessels, three-quarters of our patients were exposed to four or fewer blood units during their entire hospitalization.
Return to Top
Revised 9/06
