Transfusion support for the bleeding patient (Proceedings)
Transfusion of blood products is an important lifesaving measure performed frequently in veterinary medicine. The decision to transfuse should not be taken lightly: it is costly and can frequently be clouded by complications. Blood transfusion therapy should be limited to the treatment of anemia, hypoproteinemia, coagulation disorders, or hemodynamic instability. The following review will focus on practical considerations of blood product therapy, including component selection, administration rates, monitoring techniques and transfusion complications, and the use of hemoglobin based oxygen-carrying fluids.
There are limited reasons for which to transfuse a patient. Anemia is the most common reason. Careful evaluation of the underlying cause of anemia should be considered. Anemia can be defined as a decrease in the number of red blood cells. There are two types of anemia: regenerative and non-regenerative. If the anemia is regenerative, the bone marrow is functional and the anemia will resolve, provided the underlying cause of anemia is treated. Non-regenerative anemia is generally associated with a chronic illness in which the bone-marrow production is insufficient. The cause of the anemia needs to be treated indefinitely.
Keep in mind that every anemic patient that is admitted does not necessarily need to be transfused: the type of anemia must be established, and the cause of the anemia must be found. The duration of the anemia must be determined, and the trends of the PCV/TS must be monitored carefully. (This will be discussed in a later section.)Hypoproteinemia is another reason to transfuse a patient. Severe protein deficiency (regardless of the cause) can result in pulmonary edema, pleural effusion, abdominal distention (ascites), or subcutaneous edema. Conditions severe enough to cause such clinical signs warrant transfusion of blood or blood products.
Lastly, a patient with a severe coagulation disorder may also require a blood transfusion. Note that not every patient with a coagulopathy requires a blood transfusion. If the coagulopathy results in severe anemia, transfusion medicine is applicable. Patients with thrombocytopenia should not be transfused solely on the platelet count. It would take large amounts of fresh, whole blood to raise a patient's platelet count by a mere 10%. Most coagulopathic patients require clotting factors, not necessarily just the platelets, to help correct a coagulopathy or to prevent hemorrhage. Careful consideration to the type of blood product is vital. (This will be discussed in a later section). The severity of the coagulopathy must also be considered in a timely fashion. For example, a patient that has ingested rodenticide and a patient in DIC would not necessarily be treated in the same fashion, although both are coagulopathic. It is not necessary to transfuse all rodenticide toxicities, nor every DIC patient. The severity of the anemia, the severity of the coagulopathy, and the overall systemic stability of the patient should first be evaluated.
Knowing when to transfuse is critical. The PCV/TS is not the only factor in making this decision. Patient history is extremely important, as well as the duration of the illness. For example, if a patient presents with a PCV of 13, transfusing the patient on this number alone is not founded. This patient with a PCV of 13 might have chronic renal failure and have been at 13 for weeks. Again, establish whether the anemia is regenerative or non-regenerative and carefully evaluate the patient systemically (i.e.: respiratory pattern) to establish proper compensatory mechanisms to the anemia. Conversely, if a patient with a low PCV had history of trauma, suspect abdominal or thoracic bleeding. Evaluate each cavity radiographically (or by centesis, ultrasound), and make the decision to transfuse based on hemodynamic stability (blood pressure, pulse quality), and ventilatory patterns.
Monitoring the trends of the PCV/TS is essential. Know the baseline PCV/TS before fluid administration, before transfusions, before diagnostic tests. If possible, do not take the PCV from a catheter, be consistent with how long the hemocrit tube is spun and who reads it, in order to eliminate margin of error. Understand exactly what a PCV determines, and the value of the total protein.
The following list categorizes the type of blood product and what it supplies to the recipient:
1. Stored whole blood
a. Supplies RBC's (increases oxygen delivery to tissues)
b. Supplies plasma proteins (oncotic volume expansion)
c. Supplies stable coagulation factors (fibrinogen)
Please note that whole blood does not supply platelet or labile coagulation factors V and VII.