Vet Times The website for the veterinary profession https://www.vettimes.co.uk Feline blood transfusions: preliminary considerations Author : Andrea Harvey Categories : RVNs Date : September 1, 2011 ABSTRACT Performing a blood transfusion can be a life-saving event. However, this is not a straightforward procedure in cats. Cats have naturally occurring antibodies to the opposite blood type and, therefore, always need to be blood-typed prior to transfusion. A transfusion may be needed for a number of reasons, but deciding whether blood is required, and when, is not always easy. A blood donor then needs to be sourced. Not all cats make suitable donors, and a careful choice is required to ensure appropriate blood is collected for the recipient, and that the donor is not put at risk of complications. The donor cat s owner must be made aware of the potential risks to the cat, and informed consent given. Practicalities, technique and equipment then need to be considered. Finally, both recipient and donor need to be monitored closely following the procedure. The veterinary nurse has an important role in supporting both cats and sets of owners. This article aims to provide some practical guidance for the veterinary nurse on all steps of the blood transfusion process. When is a blood transfusion required? There is no magic number packed cell volume (PCV) below which a blood transfusion is required. Requirement depends on the clinical effects of the anaemia, and, to some extent, the underlying cause and expected response to treatment and/or degree of regeneration. Severity of anaemia, cardiovascular status, speed of onset of anaemia and degree of regeneration are important considerations in deciding whether a transfusion is needed. Blood collection also takes time approximately 30 minutes on average, once the donor cat and all the equipment is ready. Finding a suitable donor can take considerable time; therefore, blood transfusions are not always 1 / 7
suitable for immediate support in a collapsed cat, and alternative fluid therapy support is likely to be required initially. Feline blood types Figure 1. A blood typing card demonstrating a type-b cat. Note the agglutination of red blood cells in the type-b well. There are three feline blood types A, B and AB. In contrast to dogs, cats have naturally occurring antibodies against the other blood types. This means that even with a first transfusion, a transfusion reaction would occur if the cat was administered the wrong blood type. If type-b cats were given type-a blood, the reaction could be fatal. It is, therefore, essential that all feline donors as well as recipients are blood-typed prior to collecting blood. 2 / 7
Type-A cats must only receive type-a blood. Type-B cats must only receive type-b blood. Type-AB cats should ideally receive type-ab blood, but, when unavailable, type A blood is the second choice. Type A is the most common blood type in domestic shorthair (DSH) cats. Some pedigree breeds have a higher prevalence of type B, such as the British shorthair, ragdoll, Birman and rex breeds, along with Persians, Somalis, Abyssinians, Himalayans and Scottish folds. In-house blood typing kits mean immediate results can be obtained. They are quick and simple to use and are relatively cheap. Examples include in-house cards (Rapid Vet-H, www.rapidvet.com; Figure 1 ) or strip tests (Quick Test A+B, www.alvediavet.com/products_new.php). Choosing a donor cat Obtaining consent for blood donation Owners must be made aware of what informed consent means, and that they fully understand the risks associated with the procedure. This is especially important in cats because there is a higher risk involved in cats donating blood compared to humans or dogs. This is mainly due to their small size and the relatively larger proportion of their total blood volume that is being removed, together with the fact they usually need to be sedated for blood collection. It is also common for cats to have occult diseases (such as renal and cardiac disease) that may not be evident on routine health checks. It is important to provide the owner of the potential donor with information and to discuss the procedure and associated risks with him or her, and the precautions that you will be taking. Informed consent should always be obtained from the owner before using a cat for blood donation. What are the risks to a blood donor? Potential risks are detailed below. Hypotension resulting from removal of a large volume of blood. This may also be exacerbated by sedation. Occult heart disease is quite common in cats and severe hypotension may develop if this is present. Exacerbation of occult disease of particular importance are heart disease (as above) and renal disease. Renal failure can be exacerbated by hypotension. Is the potential donor suitable? Any cat used for donation should meet the following criteria. 3 / 7
Healthy (indoor, fully vaccinated cats are ideal) and clinically well animals. Large (more than 4kg) and non-obese. Calm temperament. Aged one to eight years. Haematology and biochemistry should be checked to ensure within normal ranges. Recently screened for blood-borne infectious diseases (feline leukaemia virus, feline immunodeficiency virus and haemoplasma negative are essential, with or without Bartonella). Comprehensive clinical examinations should be performed and a complete donor history obtained. There should be no findings of concern. Donor PCV should be determined before each donation and should be 35 per cent or above. It is also preferable to check the donor s blood pressure before each donation to ensure it is normal (120-180mmHg). Occult heart disease and other conditions can be associated with low blood pressure, which may be exacerbated by sedation and blood donation. Check the blood type compatibility. Both the recipient and donor must be blood-typed. What can be done to minimise the risks of blood donation? Ensure the cat is a suitable blood donor (as above). Ensure the cat is healthy (as above). Take every precaution during and after the procedure. The donor cat should have been starved for at least four to five hours before sedation. Double check all pre-donation checks have been performed. Choose sedative agents that have a minimal effect on blood pressure avoid drugs such as acepromazine and medetomidine. Immediately after blood collection, intravenous fluids should be administered rapidly to the donor to replace the blood taken (a total of twice the volume of blood removed should be given over approximately 30 to 60 minutes). The cat should be kept warm and monitored closely after donation and sedation to ensure a quick recovery. The cat should be fed as soon as it is awake enough to be able to eat. Feline donors can usually be discharged three to five hours after the donation procedure, providing there are no concerns or problems, and they have fully recovered from the sedation. Collection of blood from the donor The maximum safe volume of blood to take from a donor cat is approximately 10-12ml/kg (in effect, approximately 50ml from a 4-5kg cat). The equipment required includes: 4 / 7
sedative (usually ketamine and midazolam); anticoagulant citrate phosphate dextrose acid (CPDA) or acid citrate dextrose (ACD) from human blood collection bags is preferred; 10ml syringes five; 21G needle and T-port or 19G butterfly needle (have spare ones ready); three-way tap; and small (100ml) blood collection bag where available (or a human blood collection bag emptied of anticoagulant), with exit tubing tied off/blocked. Figure 2. Blood being transferred into a blood collection bag. Care should be taken to ensure that this is done aseptically. Transfer should be performed slowly with a large-gauge needle to reduce damage to red blood cells during transfer. The method of preparation is as follows. Flush through the syringes, needle, extension tube and three-way tap with anticoagulant, and place 1ml anticoagulant into each 10ml syringe (although not ideal, you can use heparin anticoagulant if CPDA or ACD is unavailable; use 125 units per 10ml of blood. Heparinised blood must be used immediately). Place an intravenous catheter in both the donor and recipient. Set up intravenous fluids with normal saline or lactated Ringer s solution for the donor. Blood is collected from the donor aseptically from the jugular vein. Restraining the donor in an upside-down position, with the handler raising the vein at the base of the neck and the bleeder holding the head and extending the neck, can be a successful method. To bleed in this position the needle is inserted into the jugular, aiming towards the base of the neck. The needle is attached to the extension tube, which is connected via a threeway tap to a 10ml syringe. The bleeder inserts the needle into the jugular and draws back the 10ml syringe to collect the blood. The syringe must be regularly inverted to allow mixing of the anticoagulant and blood to prevent clotting. It may be easier to have one person holding the 5 / 7
needle steady in the jugular vein, while a second person holds the collection syringe, enabling rotation of the syringe as blood is collected. Once the first 10ml syringe is filled, the three-way tap is closed off. The syringe is disconnected and a 19G needle placed on the hub. A second 10ml syringe is attached, the three-way tap opened and blood collection continued until all five syringes are filled. The filled syringes should be inverted intermittently to prevent clotting. Transfer collected blood slowly into a blood collection bag via a 19G needle, and attach a blood filter giving set to a bag for administration to the patient ( Figure 2 ). The transfusion Figure 3. Blood is administered via a peripheral intravenous catheter, using a filtered giving set. Blood is usually administered via an intravenous catheter placed in the cephalic or saphenous vein, and using a filtered giving set ( Figure 3 ). An initial rate of 0.5ml/kg/ hour should be used over the first five to 15 minutes and the recipient observed for adverse transfusion reactions. Signs of reaction include tachycardia, urticaria (facial swelling), hypotension, vomiting, diarrhoea, 6 / 7
Powered by TCPDF (www.tcpdf.org) dyspnoea/tachypnoea, pyrexia and haemoglobinuria. Continuous monitoring of the cat s demeanour is required in the first 15 minutes, along with assessments of facial swelling, vomiting/diarrhoea, heart rate, pulse quality, respiratory rate and temperature. If no evidence of transfusion reaction occurs, the rate can be increased as required. The transfusion should be completed in four hours to reduce the risk of bacteraemia. Transfusion reactions If you suspect a transfusion reaction, stop the transfusion and treatment with glucocorticoids, antihistamines and/or adrenalin may be considered. Antipyretics may be required. If circulatory overload has resulted in pulmonary oedema, diuretic treatment and oxygen support may be required. // 7 / 7