Transfusion of blood products is a frequent necessity in small animal practice. Although potentially life-saving, this procedure
does carry some inherent risk. To practice successful transfusion medicine the clinician must understand not only when and
how to administer the appropriate blood product; but also how to collect and store these products to minimize the potential
for an adverse outcome.
The plethora of blood products, fractions, and concentrates now available for transfusion may seem confusing. However, it
is rational to use a component wherever possible as this practice not only reduces the element of risk, but is also a more
efficient use of valuable resources.
Canine transfusions are commonly provided as components; packed red blood cells (pRBCs) and fresh-frozen plasma (FFP). Each
unit (~450 mL) of whole blood, if processed promptly, may be divided into 1 unit of pRBCs and 1 unit of FFP. Fresh frozen
plasma represents plasma that has been separated and frozen within 6 hours of collection. It has a shelf-life of 1 year, after
which it is stable for an additional 4 years as frozen plasma. Fresh frozen plasma may also be divided into cryoprecipitate
and cryo-poor plasma. Cryoprecipitate contains increased concentrations of factor VIII, von Willebrand factor (vWF), and fibrinogen.
Fresh whole blood may also be processed into platelet-rich plasma or platelet concentrates and typically has a half-life of
Collecting blood for feline transfusions is inherently more challenging than for canine blood transfusions. Cats' blood volume
is less than dogs' and donation typically requires sedation. Though cat blood transfusions are still commonly administered
as whole blood, units can be separated into pRBCs and FFP components and are commercially available.
Blood products may be purchased from commercial blood banks or collected and processed in-house before emergent need. The
once common practice of bleeding a staff member's personal dog or an in-house donor on an as-needed basis is not appropriate
for most emergency practices because of time constraints and the manpower required.
In dogs, whole blood is collected into bags containing citrate–phosphate-dextrose–adenine (CPDA-1) as the anticoagulant preservative.
These bags provide a closed system for collection and separation, which minimizes the opportunity for bacterial contamination.
Each bag is designed to collect 450 mL. Sixty-three milliliters of anticoagulant is located in the main collection bag. The
storage time for canine packed red blood cells (pRBCs) collected in CPDA-1 has been suggested to be 20 days. This short lifespan
is not a problem when the product collected is immediately used, but it does present a significant problem when products are
banked for later use. Additive solutions for the preservation of RBCs are available in closed-collection systems used in dogs.
Both Adsol and Nutricel have been evaluated as additive solutions for canine pRBC storage. Adsol extended viability from 20
to 37 days, and Nutricel extended viability to 35 days.
Cat blood is most commonly collected into a syringe through a butterfly catheter. The anticoagulant must be added before collection.
Anticoagulants used most commonly include acid–citrate–dextrose (ACD) and CPDA-1. The ACD and CPDA-1 are used at a ratio of
1 mL per 6-9 mL of whole blood. Typically, feline whole-blood units contain a total volume of 60 mL (7 mL of anticoagulant
and 53 mL of whole blood).