Chapter 16
Feline Blood Collection
Robyn K. Taylor and Karen Humm
Royal Veterinary College, Queen Mother Hospital for Animals, Hatfield, Hertfordshire, UK
Introduction
The main reason for a blood transfusion in a cat is poor oxygen-carrying capacity and subsequent tissue hypoxia from a decrease in red cell mass. This can be due to a lack of red cell production, red cell destruction, or blood loss. In the United States and Canada, blood banks store feline blood products, but in most other countries these blood products are not available and feline blood donation is only performed when a recipient is in need of blood. This can create difficulties obtaining blood for a patient, as a suitable feline donor needs to be identified for the collection of fresh whole blood (FWB).
Because feline transfusions create a demand for a very precious resource, ensuring the patient is a suitable candidate for transfusion is essential. Before a feline blood collection is considered, it is imperative that the level of need for the blood transfusion by the recipient is established. A blood collection from a cat has risks and is not a benign procedure. While some countries have feline donor colonies that live in the hospital, this is uncommon in many countries, such as the United Kingdom (UK). It is therefore important to recognize that most feline donors are healthy cats, often pets owned by staff in the hospital or a member of the public. Because the blood collection is performed using a cat that otherwise does not require any veterinary medical intervention, the need for the blood collection must be recognized before the cat donates. The benefit to the recipient greatly outweighs any benefit to the donor, therefore the donor’s well-being and safety must take priority over the recipient’s need for the blood transfusion.
This consideration brings its own ethical challenges. Sometimes decisions might have to be made as to the suitability of the recipient of the proposed transfusion in light of donor considerations. Such factors that might influence this decision are the disease process or age of the recipient (i.e., how much the transfusion will aid in the recovery of the patient and improve the quality of life). Additionally, if there are two recipients requiring a blood transfusion and only one suitable blood donor, priority will usually go to the recipient who is the least stable and/or has the greatest need for the transfusion, while a second donor is located for the other recipient. Under any circumstance, essential points must be maintained to adhere to a good standard of care during the blood collection process (Box 16.1).
Donor selection
When preparing for a feline blood collection for transfusion to a recipient, it is vitally important to select an appropriate donor. This has been covered thoroughly in Chapter 15, which explains how to choose and screen the feline donor appropriately prior to blood collection. Specifically, the donor must be of the correct blood type to match the recipient, as well as up to date with all routine blood screen tests, vaccinations, deworming, and flea treatments. Selecting the correct blood donor is the first step in successful blood collection for transfusion.
Donor eligibility
History and consent
Some important questions should be asked of the owner of the feline donor regarding the cat’s health since the last donation. Such questions include if the cat has exhibited any vomiting, diarrhea, coughing, sneezing, or changes in eating or drinking habits, and whether the cat is being given any medications or supplements. Recent vaccinations or surgeries during the previous 4 weeks or travel (depending on the area) might also prevent a cat from donating. When the cat last ate food is also helpful to know as fasting is recommended to minimize the risk of any vomiting during sedation and to prevent a lipemia in the collected blood.
The owner should sign a consent form with full understanding of the blood collection procedure. Confirmation should also be made with the owner that the blood bank records are correct and that the cat has not donated blood at any other hospital during the previous 8 weeks. There is no consensus on the minimum interval between feline donations, but 8 weeks is commonly recommended to prevent adverse effects such as anemia.
Physical examination
A thorough physical examination must be performed by a veterinarian to ensure the health and well-being of the feline donor. This examination should include auscultation of the heart to listen for any rhythm abnormalities or murmurs, auscultation of the lung fields to confirm the health of the respiratory system, palpation of the lymph nodes for any enlargement, and palpation of the abdomen to rule out any unusual findings. Temperature, pulse, and respiratory rate should also be recorded. If echocardiography is available, it is recommended to examine all donors prior to their first donation due to the risk of occult cardiomyopathy, which can be present with or without a heart murmur (Côté et al. 2004; Paige et al. 2009).
If the physical examination determines that the cat is healthy and able to donate, the venipuncture and intravenous (IV) catheter sites can be clipped and a topical anesthetic such as eutectic mixture of local anesthetics (EMLA) cream applied using the manufacturer’s recommended dose (see the section on pre-donation procedure). EMLA causes methemoglobinemia in human neonates and is theorized to do so in cats as well, especially if inappropriately applied (Larson et al. 2013; Wagner et al. 2006). In contrast, the use of another topical anesthetic called liposomal lidocaine cream has no reports of methemoglobin development (Fransson et al. 2002).
Another important procedure that must be completed prior to blood collection is measuring the cat’s body weight to ensure the required volume of blood can be collected safely. No more than 
of blood should be collected from feline donors (Davidow 2013).
Blood tests
The hematocrit (HCT) or packed cell volume (PCV) should also be measured to ensure the cat is not anemic and can safely donate blood. The minimum HCT or PCV value recommended for a safe blood collection is 30–35% or a hemoglobin of 
(Barfield and Adamantos 2011). If the value is below this threshold, the cat should not be used on this occasion and further investigation to understand the reason for the anemia should be performed. Performing in-hospital feline leukemia virus (FeLV) and feline immunodeficiency virus (FIV) blood testing is also highly recommended at every feline blood donation if the donor has contact with other cats, such as outdoor cats or those living in multiple cat households.
Once the vital signs and laboratory values are obtained, they should be compared to values from the previous blood collection. A comparison is a useful tool to establish a pattern for that particular cat and to determine if abnormalities are present. For example, a cat might present with a higher temperature than the reference range, which might be normal for the cat because the cat becomes anxious in the car on the way to the hospital. A weight change can indicate an illness otherwise undetected and might prompt investigation.
Depending on the protocols set in place at the hospital, routine health screen blood testing (see Chapter 15) such as hematology and biochemistry profiles, as well as infectious disease screening might be due. These tests are performed prior to the first donation and annually thereafter. If the donor is due for annual screening of these tests, these blood samples can be drawn at the time of collection. However, if a crossmatch is required prior to the blood collection, the blood samples will need to be drawn first and crossmatch procedure performed to ensure a match between the donor and recipient before any blood is collected from the donor (see Chapter 10).
Pre-donation procedure
Preparing for donation
Being organized prior to the blood collection is paramount. All supplies required for a smooth and successful feline blood collection must be readied first (Box 16.2). Calculating the volume that can be safely collected from the donor is also of the utmost importance. A blood collection ranging from 10 to 15 mL/kg has been recommended (Davidow 2013) and has been shown to have minimal adverse effects on blood pressure and heart rate (Iazbik et al. 2007). In the authors’ experience, limiting the collection volume to 12 mL/kg has consistently minimized adverse effects during and after the donation.
It is common practice for feline blood donations to collect enough blood to fill a 60 mL syringe (one unit) primed with anticoagulant solution. A feline donor would need to be 4.3 kg or heavier for a 
collection, which would fill a 60 mL syringe when the volume of anticoagulant needed is included (Box 16.3).
It is uncommon to collect a volume greater than the 60 mL from feline donors. However, on occasion larger cats such as Maine Coon or Norwegian Forest cats might be able to donate a larger volume of blood. In such cases, calculations should be performed to ensure that a safe volume within the recommended range is collected. However, these situations are rare and in most circumstances, 60 mL syringe collections are not exceeded, even with larger donors.
Preparing the donor
Placing an IV catheter is highly recommended and is routinely performed with most feline blood collections. This is to enable IV sedation if needed, as well as fluid therapy as part of the after care of the donor. While many blood banks use sedation for feline blood collections, the authors recommend sedation only for cats that are demonstrating signs of stress, as conscious blood collections are becoming more frequent in cats. The first recommended site for an IV catheter is the cephalic vein, although for short-term IV catheter placement the lateral or medial saphenous vein would also be suitable. The selected IV catheter site should be clipped. The blood collection is best obtained from the jugular vein, therefore the area over the jugular vein should also be clipped. All venipuncture and catheter sites should be recorded (right vs left), since alternating sides between donations is best practice to minimize repeated use of one vessel.
Topical local anesthetic creams are very effective at the manufacturer’s recommended dose to perform conscious blood collections and IV catheter placement with ease by reducing the pain stimulation associated with needle insertion through the skin. EMLA or liposomal lidocaine creams are routinely used as a topical cream for this effect. Covering the skin with a non-absorbent dressing after the cream is applied is recommended to prevent inadvertent removal of the cream by the patient. As anesthetic creams have a relatively long time to onset of activity, applying the cream to the clipped areas as soon as possible after the physical examination will allow time for the cream to be effective. Studies suggest waiting 60 minutes after the application of EMLA cream prior to catheterization in cats (Wagner et al. 2006) and 20–30 minutes after application of liposomal lidocaine.
Ensuring the feline donor is comfortable and that stress is minimized throughout the procedure is of the utmost importance, therefore maintaining an environment that is as stress free and as calm as possible is essential. Considerations are made from the time the cat arrives at the hospital to donate. The kennel allocated to the cat for pre- and post-donation boarding should be in a quiet area that provides the most stress-free environment for the donor as reasonably possible. The donor might benefit from having his or her own blanket from home while in the hospital to provide familiar smells; feline pheromone sprays and diffusers can also be used to decrease stress (Beck 2013). The donor should be given water and a litter tray, but no food, and left to relax in the kennel while the materials for blood collection are being prepared.
Select a quiet room where there will be no disruptions during the blood collection. All supplies needed for the blood collection should be set up in this room. A successful blood collection ideally requires three people: a phlebotomist, someone to restrain and monitor the cat, and someone to fill the syringe(s). Ideally, this room should also be in close proximity to any emergency veterinary assistance you might urgently require for the donor if any complications occur during the blood collection. Let members of the veterinary team know that a blood collection is being performed so that you will not be disturbed and they can be available if assistance is required for any reason.
Preparing materials
The equipment and materials for feline blood collection are provided as a guideline and representation of what is used for collection in the authors’ experience (Box 16.2). Collection techniques vary depending on whether the blood is required for immediate transfusion or for storage for later use.
Anticoagulants
Anticoagulant solutions used for blood collection contain either citrate or heparin, but citrate is preferred. Citrate acts as an anticoagulant by binding the calcium in the collected blood, which is required for coagulation to occur. Conversely, heparin potentiates the activity of antithrombin, resulting in anticoagulation via inactivation of thrombin. Aseptic technique should be followed when withdrawing anticoagulant from a vial or fluid bag, including swabbing of the rubber injection port with alcohol.
Heparin
Heparin is available in most veterinary practices and can be the anticoagulant used if blood collections are rarely performed and the blood is transfused immediately after collection. If using heparin, 5–12.5 IU per milliliter of collected blood is recommended (Abrams-Ogg 2000). The concentration of the stock heparin solution should be diligently checked, since several concentrations exist (e.g., 1,000 IU/mL vs 10,000 IU/mL). Heparin is not a preservative and does not enable storage of blood for later use.
CPD and CPDA-1
Citrate-phosphate-dextrose (CPD) and citrate-phosphate-dextrose-adenine (CPDA-1) are anticoagulants used in human blood collection bags that have been adopted for canine blood collections. The storage time for collected blood varies depending on the anticoagulant used and the collection system chosen. If using an open collection system, no longer than 24 hours in refrigerated conditions of 33–42°F (1–6°C) is the recommended ideal storage time. If the semi-closed collection system using CPD or CPDA-1 has been selected, then 20 days under refrigeration storage conditions of 33–42°F (1–6°C) is recommended (Kohn and Weingart 2012).
These anticoagulants can be extracted aseptically and used for feline blood collection as well. Breach of the collection bag during removal of the anticoagulant renders the bag unusable for canine blood collection. Discarding the bag can be costly depending on the type of bag stocked by the practice. The cost of a single FWB collection bag is much less than the cost of a quad collection bag used for component collection, therefore this would be the ideal bag to use to extract anticoagulant from.
ACDA
Acid citrate dextrose solution A (ACDA) is the preferred anticoagulant in the UK as it is often less expensive than CPD or CPDA and is supplied in 500 mL or 1000 mL multiple-use bags. A volume of 1 mL of ACDA is used per 7 mL of collected blood (i.e., 8.5 mL in a 60-mL syringe for collection) and provides a shelf-life of 30 days for whole blood (Davidow 2013).
Sedation and anesthetic options
Many sedation and anesthetic protocols can be used during feline blood collection (Box 16.4). If sedation is required for the feline donor, it is advisable to avoid using acepromazine as it can cause platelet dysfunction, which is undesirable for both the recipient and donor (Conner et al. 2012). Acepromazine can also cause hypotension, which might result in difficulty performing the phlebotomy (Grasso et al. 2015).
Propofol (6 mg/kg IV) has been used in the past in combination with other sedatives. However, propofol is no longer the drug of choice for feline blood collection as it has been reported to have undesirable cardiovascular and respiratory effects, including hypotension, bradycardia, hypoventilation, and apnea in cats (Glowaski and Wetmore 1999).
Drugs such as butorphanol, dexmedetomidine, and/or ketamine can be effective sedatives for feline blood collection. Although dexmedetomidine is a reliable muscle relaxant and sedative it can cause vasoconstriction, making venipuncture and blood collection more difficult and therefore it is not routinely recommended. Ketamine has a rapid onset, can provide a prolonged sedative duration, and its cardiovascular effects make it a favorable choice when used in combination with other sedatives for the purpose of feline blood collection (Volpato et al. 2015).
IV only
After the IV catheter has been placed using aseptic technique and checked for patency, the sedation is administered via the IV catheter and it is flushed with catheter flush solution.
Sedation will take effect almost immediately so everything must be in place for the blood collection before sedating the donor. This sedation protocol is short acting (approximately 10–15 minutes), allowing for a smooth blood collection and donor recovery.
IM first, then IV
If the donor is stressed, anxious, or unmanageable then it is best not to persevere in placing an IV catheter. In this case, IM sedation prior to IV catheter placement is recommended. The donor should be housed somewhere secure and quiet for about 20 minutes after IM sedation to allow the drugs to take full effect. Even if IM sedation appears to have provided enough of an effect to continue with the blood collection, an IV catheter must still be placed for post-donation fluid support. If additional sedation is required for the blood collection, then additional drugs should be provided (Box 16.4).
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