Small Animal Medical Nursing: Blood Product Transfusions

Introduction and Veterinary Technician Responsibilities

• Blood Product Transfusions: Veterinary technicians are integral to the success of transfusion medicine, maintaining several key areas of responsibility.

• Core Responsibilities:

  • Donor Collections: Managing the selection and screening of donors and the physical collection of blood.

  • Separation and Storage: Processing whole blood into various components and ensuring proper storage conditions (temperature and expiration monitoring).

  • Administration: Setting up delivery systems and managing the infusion process.

  • Patient Monitoring: Observing the recipient closely for therapeutic efficacy and adverse reactions.

Indications for Transfusion Medicine

• Blood (Whole Blood or RBCs):

  • Acute hemorrhage.

  • Chronic or hemolytic anemia.

• Platelet Transfusions:

  • Severe thrombocytopenia accompanied by active hemorrhage.

  • Used prophylactically for patients with severe thrombocytopenia requiring surgery.

• Plasma Transfusions:

  • Coagulopathy (clotting factor deficiencies).

  • Hypoalbuminemia (low protein levels).

  • Failure of passive transfer of immunity (specifically in neonates).

Blood Donor Selection and Preparation

• Criteria for Healthy Donors:

  • Temperament: Must be calm enough for the procedure; sedation is used if necessary, though most dogs become accustomed to the routine without it.

  • Physical Parameters: Must have an adequate Packed Cell Volume (PCV), appropriate body weight, and normal Total Protein (TP) levels.

  • Anatomy: Good access to the jugular vein is required.

  • Health Screening: Must be screened for infectious diseases.

• Collection Site Preparation:

  • The collection site (typically the jugular vein for both dogs and cats) must undergo full surgical preparation.

• Collection Process:

  • Collection is performed rapidly and without interruption to prevent activation of clotting factors or damage to cells.

Pre-Transfusion Testing and Cross-Matching

• Blood Typing: Identifying the specific blood group of the donor and recipient.

• Antibody Screen: Testing for the presence of RBC antibodies.

• Cross-matching Procedures:

  • Major Cross-match: Tests for agglutination reactions between the donor’s RBCs and the recipient’s plasma. This is the most critical test to prevent acute hemolysis.

  • Minor Cross-match: Tests for agglutination reactions between the donor’s plasma and the recipient’s RBCs.

• Testing Resources: Mentioned labs include Rapid Vet-H and DMS Laboratories (Flemington, New Jersey).

Blood Collection Calculations and Limits

• Calculation Base: All collection volumes should be based on the animal's lean body weight.

• Maximum Donation: Generally limited to $10-15\%$ of the animal's total blood volume.

• Specific Species Guidelines:

  • Canine: $13-17\,\text{mL/kg}$ of body weight.

  • Feline: $11-15\,\text{mL/kg}$ of body weight.

  • Equine: Approximately $16\,\text{mL/kg}$ of body weight.

Anticoagulants and Storage

• Immediate Use: Sodium citrate is the preferred anticoagulant when the blood product will be used immediately.

• Storage and Preservation:

  • Citrate-phosphate-dextrose (CPD).

  • Citrate-phosphate-dextrose-adenine (CPDA).

Overview of Blood Products and Indications

• Fresh Whole Blood (WB):

  • Composition: Contains Red Blood Cells (RBCs), plasma proteins, viable platelets, and all clotting factors.

  • Timing: Must be used within $6\,\text{hours}$ of collection to maintain all properties (specifically platelets and labile factors).

  • Indications: Severe bleeding, coagulopathies (e.g., DIC, warfarin toxicity), factor deficiencies, severe anemia, and severe hypoproteinemia.

• Packed Red Blood Cells (pRBCs):

  • Composition: Supplies red blood cells only (for oxygen delivery).

  • Shelf Life: Roughly $35-42\,\text{days}$.

  • Indications: Anemia with normal plasma volume; hemorrhage.

• Fresh Frozen Plasma (FFP):

  • Definition: Plasma frozen within $8\,\text{hours}$ of collection; less than one year old.

  • Composition: Supplies all labile clotting factors (Factor 5, Factor 8, von Willebrand Factor [vWF]), Vitamin K-dependent clotting factors (Factors 2, 7, 9, 10), and albumin.

  • Indications: Coagulopathy of unknown origin, DIC, warfarin toxicity, inherited factor deficiencies, and hypoproteinemia.

• Frozen Plasma (FP):

  • Storage: Can be kept for $2-5\,\text{years}$.

  • Composition: Supplies plasma proteins and Vitamin K-dependent clotting factors (2, 7, 9, 10), but does not supply labile clotting factors.

  • Indications: Anticoagulant rodenticide toxicity, hypoproteinemia, colostrum replacement, and volume expansion.

• Cryoprecipitate (Cryoppt):

  • Composition: Concentrated labile clotting factors (Factor 5, Factor 8, and vWF).

  • Indications: von Willebrand Disease (vWD) and Hemophilia A.

• Cryoprecipitate Poor Plasma (Cryopoor):

  • Composition: Albumin and Vitamin K-dependent clotting factors (2, 7, 9, 10).

  • Indications: Anticoagulant rodenticide toxicity and hypoproteinemia.

Blood Product Administration Protocols

• Preparation:

  • Blood temperature should be less than or equal to body temperature ($\le\text{body temp}$).

  • Plasma should be thawed in a water bath.

• Contraindications for Co-administration: Do not give blood products with:

  • Hypertonic or hypotonic solutions.

  • Calcium-containing solutions (e.g., Lactated Ringer's Solution).

• Volume and Rate:

  • Estimation: Based on patient blood loss and estimated blood volume.

  • Canine Plasma Dose: $10-15\,\text{mL/kg}$.

  • Feline Plasma Dose: $5-8\,\text{mL/kg}$.

  • Rule of Thumb: Start the infusion slow; the total transfusion time must be less than $4\,\text{hours}$.

Patient Monitoring

• Frequency: Monitoring should occur every $15\,\text{minutes}$.

• Critical Period: The first $15\,\text{minutes}$ of the transfusion is the most critical time for observing adverse reactions.

• Parameters to Monitor:

  • Physical exam and vital signs.

  • Packed Cell Volume (PCV).

  • Blood lactate levels.

Transfusion Reactions

• Acute Allergic Hypersensitivity:

  • Signs include erythema (redness), urticaria (hives), pruritus (itching), or full anaphylaxis.

• Acute Hemolytic Transfusion Reactions (AHTR):

  • Causes: Incompatible blood; reaction occurs very quickly.

  • Signs: Hemoglobinemia, hemoglobinuria, progressive anemia, lack of PCV increase, systemic inflammatory response, DIC, shock, and cardiovascular collapse.

• Delayed Hemolytic Transfusion Reactions: Often caused by improper handling of the blood product.

• Other Immune-Mediated Reactions:

  • Fever: The most common nonhemolytic immune reaction.

  • Transfusion-Related Acute Lung Injury (TRALI).

• Non-Immunologic Reactions:

  • Transfusion-Associated Circulatory Overload (TACO): Caused by large volumes or rapid delivery, leading to pulmonary congestion. Signs include coughing, increased respiratory rate, and respiratory distress.

  • Bacterial Contamination.

  • Citrate Toxicity.

• Management of Overload/Reactions:

  • If vascular overload occurs, reduce the rate to approximately $1\,\text{mL/kg/hr}$.

  • Vomiting is a possible reaction; food, water, and medications should be withheld during the transfusion.

Feline Blood Group System

• Blood Types: The AB system includes Type A, Type B, and the rare Type AB. A newer type, Mik, has also been identified.

• Frequency in the United States:

  • Type A: Greater than $90\%$ of Domestic Shorthair (DSH) cats.

  • Type B: More common in certain purebred cats. Distribution varies by geographic region.

• Natural Alloantibodies:

  • Found in all cats by a few weeks of age.

  • Type B cats have strong anti-A antibodies.

  • Type A cats have anti-B antibodies.

• Transfusion Incompatibility in Cats:

  • Type A given Type B blood: Results in mild reactions on the first transfusion.

  • Type B given Type A blood: Can result in a fatal reaction even on the very first transfusion. Clinical signs (seen after as little as $1\,\text{mL}$ of blood) include vocalization, salivation, urination, defecation, depression, recumbency, bradycardia, arrhythmias, seizures, apnea, and death.

Neonatal Isoerythrolysis (NI) in Cats

• Cause: Occurs when Type A or AB kittens are born to Type B dams.

• Mechanism: The kitten ingests maternal anti-A antibodies via the colostrum, which then attack and lyse the kitten's red blood cells.

• Clinical Signs: Acute death, "fading kittens," or tail-tip necrosis.

Canine Blood Group System

• Dog Erythrocyte Antigens (DEA): The primary system includes DEA 1.1, 1.2, 3, 4, 5, 6, 7, and 8.

• Commonality: DEA 1.1 negative is the most common type.

• Historical Context: Reactions are unlikely on the initial transfusion because dogs do not have significant naturally occurring antibodies. However, previous transfusions create isoantibodies, necessitating a cross-match for any dog with a history of prior blood transfusions.