What is TRALI?
As the name implies, this is a condition that occurs as a result of a blood transfusion and is blamed for 50 percent of the transfusion related deaths in the United States. TRALI is the diagnosis when symptoms appear within the first six hours following a transfusion, although many times symptoms are present during the transfusion or within the first one or two hours after.
Doctors and researchers don't really know why transfusion-related acute lung injury occurs. It appears that no particular blood product causes it. In fact, all "plasma-containing blood products have been implicated..." (www.transfusionmedicine.ca).
Symptoms
Within the first six hours following transfusion, if not during the transfusion or immediately following, patients will report difficulty breathing (dyspnea) or excessively fast breathing (tachypnea), fever, cyanosis (bluish/grayish tinge of the skin), and hypotension (decrease in blood pressure).
On clinical examination, physicians will find respiratory distress and "pulmonary crackles" without signs associated with congestive heart failure or volume overload. Doctors may also see froth in the endotracheal tube. X-rays will show pulmonary edema in both lungs which looks like the chest cavity is filled with two clouds. At the "cloudy" stage, it is impossible for doctors to tell the difference between TRALI and Acute Respiratory Distress Syndrome.
Laboratory testing will reveal extreme, short-term decrease in the white blood cells, normal BNP tests (no congestive heart failure) and an antibody match between the donor and recipient.
Risk factors
Those who have had "recent surgery, induction chemotherapy, cardiopulmonary bypass, massive transfusion, plasma exchange for TTP [thrombotic thrombocytopenic purpura] or have recently aspirated gastric contents or developed sepsis [toxins in the bloodstream or tissues]" are at a higher risk of developing TRALI.
Causes of TRALI
While doctors are still uncertain how symptoms begin precisely, there are two theories.
The leukocyte antibody hypothesis suggests that antibodies in the blood being transfused attach themselves to the white blood cells (particularly neutrophils) of the person receiving the blood and activate. These cells adhere to the interior of the lungs and release chemicals that are toxic to the lung tissue. The reaction between the host blood cells and the "invading" blood cells is pulmonary edema. This has been found to be true in 90 percent of cases where antibodies were detected.
Since the leukocyte antibody hypothesis doesn't address the remaining 10 percent of cases, researchers/doctors have put forth an hypothesis involving neutrophils. In this hypothesis, it is believed that the neutrophils are primed and become sequestered in the lungs. Then the primed neutrophils are "activated" and the activated neutrophils damage the pulmonary capillaries. Doctors and researchers surmise that the neutrophils are already present in some patients due to recent surgery or infection and that the act of the transfusion activates them.
Prevention
As research has continued into the causes of TRALI, blood collection agencies like the Red Cross have started to implement steps to minimize the preparation of high plasma-volume components from donors who show high levels of leukocyte antibodies, this includes platelets.
As research continues, it is likely that a screening process will be introduced to identify whether or not certain factors, like the presence of leukocytes, exist in the donors and recipients, so the blood being transfused will not conflict with the transfusion recipient's natural blood chemistry.
Sources: http://bloodjournal.hematologylibrary.org; www.transfusionmedicine.ca; www.clinlabnavigator.com; www.wikipedia.com.