Blood transfusion in cats
edt November, 2016
These Guidelines were published in Journal of Feline Medicine and Surgery 17 (7), 2015, 588-593 by Maria Grazia Pennisi et al. The present guidelines were updated by Maria Grazia Pennisi.
- Blood transfusion in terminal patients should be avoided.
- Each step of the blood transfusion procedure should be performed under strict hygienic conditions, even in emergencies.
- The longer the delay between blood collection and transfusion, the higher the risk of contamination of the collected blood.
- Blood bags should be visually inspected before use and be discarded when there is any suspicion of change in colour or other visible abnormality.
- The worldwide core screening panel for donor cats includes FeLV, FIV, Bartonella and feline haemoplasma.
- Although the onset of FIP following blood transfusion in cats has not been reported, FCoV-antibody negative donors are preferred.
- The most useful, practical, rapid and inexpensive preventive measure is to check the risk profile of donor cats.
- Risk assessment may eliminate the need of repeating expensive and time-consuming screening for blood-borne pathogens in cats with a low-risk profile.
- Free-roaming cats should never be considered as potential donors.
The availability of blood components has increased the number of indications for transfusing dogs and cats and fresh whole blood is readily available to clinicians because it can be taken from in-house donor cats or “volunteer” feline blood donors. A certain amount of risk remains to the recipient cat, as immediate or delayed adverse reactions can occur during or after transfusion, related to immune-mediated mechanisms. This article, however, is dealing with adverse events caused by infectious agents, which may originate from either contamination of blood following incorrect collection, storage or transfusion or from transfusion of contaminated blood obtained from an infected donor.
Prevention of contamination of donor blood requires a multi-step manipulation of syringes and other devices, because in cats blood cannot be collected through a closed system. It is crucial that each step of the procedure is performed under the strictest hygienic conditions and bacterial contamination of blood bags is prevented, as bacterial endotoxins can cause an immediate febrile reaction or even fatal shock.
To prevent transmission of blood-borne infectious diseases the American College of Veterinary Internal Medicine adopted basic criteria for selecting pathogens to be tested in donor pets. According to that the worldwide core screening panel for donor cats includes feline leukaemia virus, feline immunodeficiency virus, Bartonella spp and feline haemoplasma. The list should be adapted to the local epidemiological situation concerning other feline vector-borne infections. The most useful, practical, rapid and inexpensive measure to reduce transfusion risk is to check the risk profile of donor cats on the basis of a written questionnaire. However, blood transfusion can never be considered totally safe.
Over recent decades, small animal transfusion medicine has made significant progress, contributing to the development of emergency medicine and critical care. The availability of blood components has increased the number of indications for transfusing dogs and cats, even if the evidence-based benefit is still lacking in certain cases (Davidow, 2013).
Fresh whole blood is readily available to clinicians because it can be taken from in-house donor cats or ‘volunteer’ feline blood donors. Thanks to the commercial availability of in-house typing kits and gel cross-match systems for cats, blood transfusion in veterinary practice has become safer and more accessible (Rudd, 2013a). However, blood transfusion implies a certain amount of risk to the recipient cat and, to some extent, also to the donor cat, subjected to an invasive procedure requiring sedation (Spada et al., 2014). These risks always need to be carefully weighed against the achievable benefits. Blood transfusion in terminal patients should be avoided and other treatment options should be considered (Rudd, 2013b). Surprisingly, blood transfusion did not reduce the risk of 30-day mortality in humans in a study performed in a critical care setting (Hérbert et al., 1999).
Immediate or delayed adverse reactions can occur during or after transfusion, related to immune-mediated mechanisms. The severity of these reactions varies from a mild febrile reaction to a severe, life-threatening circulatory overload or haemolytic crisis. The prevention of this risk is not the objective of these guidelines, since guidance is provided elsewhere (BSAVA Scientific Committee, 2000; Helm and Knottenbelt, 2010a, 2010b; Barfield and Adamantos, 2011; Davidow, 2013; Rudd, 2013a, 2013b; Kisielewicz and Self, 2014).
This guideline focuses on the prevention of transmission of infectious disease related to blood transfusion in cats. Adverse events caused by infectious agents may originate from: a) contamination of blood following incorrect collection, storage or transfusion; b) transfusion of contaminated blood obtained from an infected donor.
The blood collecting procedure in cats is of greater risk of contamination than in dogs. In cats, blood cannot be collected through a closed system as in dogs or humans and therefore a multi-step manipulation of syringes and other devices is required, with the help of several assistants. This increases the risk of contamination. In general, 50 ml of blood is collected from donor cats using three (20 ml) or five (10 ml) different syringes, each containing the appropriate quantity of anticoagulant obtained from a human blood collection bag (Rudd, 2013b). Usually, a T-connector and a three-way tap connect the IV needle to the syringes, which are filled with blood and then gently rotated by an assistant. The blood collected into the syringes is then immediately transferred into a single, plain blood collection bag through the injection port (Fig. 1). Finally, blood is transfused through a giving set inserted into another port of the bag when transfusion has to be performed.
It is crucial that each step of the procedure is performed under the strictest hygienic conditions, even in an emergency (FECAVA, 2013). The surface carrying the disposable equipment should be sterile and staff should wear sterile gloves and masks. Each syringe should be immediately sealed with its capped needle, both after adding the anticoagulant and after collecting the blood until it is transferred into the bag. Surgical preparation of the ventral neck of the donor is necessary. The longer the delay between blood collection and transfusion, the higher the risk of contamination of the collected blood. Collected blood should be stored at 4 °C. However, the blood bag should not be stored once the giving set has been inserted.
The same principles must be applied in case of autologous transfusion, a procedure reported in dogs in emergency situations such as haemothorax or haemoperitoneum: in this situation, blood is collected from the body cavity using cell salvage devices and transfused after appropriate washing (Tasker, 2013; Kisielewicz and Self, 2014).
Bacterial contamination of blood bags can cause an immediate febrile reaction in the recipient if bacterial endotoxins are produced by cold-growing Gram-negative bacteria, such as Pseudomonas species or coliforms, such as Serratia marcescens. The latter microorganism was isolated from contaminated feline blood bags and from transfused cats that presented with fever, vomiting, diarrhoea, jaundice and even death (Hohenhaus et al., 1997). Fatal endotoxin-related shock is the most dangerous consequence in such cases.
Blood bags should be visually inspected before use and be discarded where there is any suspected change in colour or other visible abnormality (Wardrop et al., 2005).
Information on feline blood-borne infectious agents is becoming increasingly available, in particular regarding vector-borne pathogens (Beugnet and Marié, 2009; Vilhena et al., 2013). In 2016, the American College of Veterinary Internal Medicine (ACVIM) updated the consensus statement on canine and feline blood donor screening for infectious diseases in North America adopted in 2005 for selecting pathogens to be tested in donor pets (Wardrop et al., 2005; Wardrop et al., 2016). Testing is recommended for pathogens that meet at least three of the following criteria: (1) documented clinical disease obtained in recipients by blood transmission; (2) possibility of subclinical infections (healthy carrier state); (3) possibility of cultivation from the blood of an infected animal; (4) the disease caused is severe or difficult to clear. Conversely, the opportunity for testing is conditionally recommended when: (1) only experimental transmission by blood is documented or (2) the disease caused is not severe in most cases or is easily overcome.
|PATHOGEN (*)||DIAGNOSTIC TESTS|
|Feline leukaemia virus (FeLV)||FeLV provirus PCR §|
|Feline immunodeficiency virus (FIV)||Rapid anti-FIV antibodies test on blood serum/plasma|
|Mycoplasma haemofelis |
Candidatus Mycoplasma haemominutum Candidatus Mycoplasma turicensis
|Bartonella spp||anti-Bartonella antibodies (IFAT) and/or blood PCR|
(*) For more information on these pathogens, see Hosie et al. (2009), Lutz et al. (2009), Pennisi et al. (2013a), Willi et al. (2006)
Tests for anti-FIV antibodies and FeLV DNA should be confirmed negative at least three months after the last exposure.
§ In life-threatening emergency situations, donors can be screened using rapid FeLV antigen tests, but owners should be informed about a higher risk.
The worldwide core screening panel for donor cats (Table 1) therefore includes: feline leukaemia virus (FeLV), feline immunodeficiency virus (FIV), Bartonella spp. and feline haemoplasma (Reine, 2004; Wardrop et al., 2005; Gary et al., 2006), but the list of pathogens to be tested in donor cats should be adapted to the local epidemiological situation (Hackett et al., 2006). Other infectious agents that may be investigated in endemic areas are reported in Table 2.
|Cytauxzoon felis||blood PCR in endemic areas|
|Babesia spp||blood PCR in endemic areas*|
|Leishmania infantum||blood PCR in endemic areas|
|Ehrlichia spp||blood PCR in endemic areas*|
|Anaplasma phagocytophilum||anti-Anaplasma phagocytophilum antibodies (IFAT)
and blood PCR in endemic area
|* probably rare and poorly characterised infection of cats in Europe|
For more information concerning these pathogens, see Carli et al. (2012), Hartmann et al. (2013), Pennisi et al. (2013b)
Two common feline infections - Toxoplasma gondii and feline coronavirus (FCoV) - do not meet the ACVIM criteria and are not included in donor screening panels (Wardrop et al., 2016).
The presence of antibodies against FCoV in blood products may passively immunize transfused cats. In case of contact with the virus in the weeks following transfusion, these cats could be exposed to the risk of the antibody dependent enhancement (ADE) of macrophage infection (Takano et al., 2008; Bàlint et al., 2014). Although there have been no reports of FIP following blood transfusion in cats, FCoV-antibody negative blood bank donors are preferred.
Although Rickettsia felis and Rickettsia of the other spotted fever group can infect cats, the organisms have never been detected by molecular methods in cat blood. At present, there is no indication for testing cats for these pathogens (Lappin and Hawley, 2009).
The risk of transmission of pathogens associated with xenotransfusion (transfusion of blood obtained from a different animal species, usually dogs) is theoretically zero for FIV, FeLV and feline haemoplasmas but may be relevant for vector-borne infections, some of which are more common in dogs than in cats (Otranto and Dantas-Torres, 2010). Xenotransfusion should be restricted to exceptional circumstances, e.g. emergencies in case of lack of compatible feline blood or oxygen carrier solution, as it is associated with delayed immune-mediated haemolysis and a very short lifespan of the transfused erythrocytes (Bovens and Gruffydd-Jones, 2013).
Molecular tests have significantly increased the sensitivity and specificity of diagnostic tests for the detection of feline blood-borne agents and their use has increased the safety of blood products. Healthy cats that test negative for FeLV p27 antigenaemia can still harbour provirus integrated in their DNA, which means their blood can transmit FeLV infection to transfused cats (Lutz et al., 2009; Nesina et al., 2015). Blood bank donors should therefore be tested for FeLV provirus using PCR. In life-threatening emergency situations, transfusions from donors can be screened using rapid FeLV antigen tests, but owners should be informed about the risk.
The screening of blood donors is also affected by costs. In human medicine, individual blood units are usually tested for several pathogens of major concern (e.g. HIV, HBV, HCV, Treponema pallidum) while for cost reasons, no testing is done for other transmissible blood-borne agents from healthy carriers (Cytomegalovirus, West Nile Virus, prions, Leishmania, etc.). The preliminary selection of potential human donors is based on history and risk assessment related to travels, sexual behaviour or certain medical procedures. This is also true in the veterinary field; the most useful, practical, rapid and inexpensive measure to reduce transfusion risk is to check the risk profile of donor cats prior to transfusion, on the basis of a written questionnaire completed by the guardian of the donor cat (Table 3). This questionnaire can be presented together with the informed consent form for blood donation. The ideal low-risk profile of a donor cat is an adult cat (more than three years old in order to reduce the risk for Bartonella bacteraemia), strictly indoor since birth, living since being a kitten in the same single-cat household (full history directly available from the guardian), regularly vaccinated and treated against fleas and ticks, with no history of travelling or vector-borne diseases. Heartworm prevention in endemic areas is also indicated, although the blood from infected cats is not infectious following transfusion (Lee and Atkins, 2010).
|Table 3: Risk profile form for candidate blood donors. If all answers are in the right-hand column, the cat has a low-risk profile for transmission of infectious agents by blood.|
Cat’s Name:………………..…………………. Breed:………………………………….
Gender: M / F Neutered: Age:……………
Circle the correct answer
|How long have you owned this cat?||Days||Months||Years|
|Is (or was) your cat free-roaming or has it (had) any outdoor access?||Yes||Don’t know||No|
|Did you adopt your cat from a shelter?||Yes||Don’t know||No|
|Was your cat a stray?||Yes||Don’t know||No|
|Did you buy your cat from a pet shop or a cat breeder?||Yes||Don’t know||No|
|Is (or was) your cat in contact with other cats?||Yes||Don’t know||No|
|Has your cat ever travelled to other countries?||Yes||Don’t know||No|
|Has your cat had any health problem in the past?||Yes||Don’t know||No|
|Has your cat had any drugs prescribed by a vet?||Yes||Don’t know||No|
|Do you regularly use anti-flea products?||No||Don’t know||Yes|
|Has your cat been vaccinated?||No||Don’t know||Yes|
|When your cat was vaccinated last?|
|Is your cat eating less than usual?||Yes||Don’t know||No|
|Have you recently seen any unusual behaviour?||Yes||Don’t know||No|
|Has your cat vomited in the last few days?||Yes||Don’t know||No|
|Has your cat had diarrhoea recently?||Yes||Don’t know||No|
|Have you seen any change in urination?||Yes||Don’t know||No|
|Have you seen any change in respiration?||Yes||Don’t know||No|
|Have you noticed sneezing or coughing?||Yes||Don’t know||No|
|Have you seen ocular or nasal discharge?||Yes||Don’t know||No|
Please inform us of any observed change in the health status of your cat in the next 15 days
Risk should be reassessed prior to each transfusion. Risk assessment may eliminate the need of repeating expensive and time-consuming screening for blood-borne pathogens in cats with low-risk profiles. The required frequency of testing varies according to the pathogen (seasonal exposure or not) and the individual risk of acquiring the infection. The ABCD does not recommend the use of closed colony donors, which are specifically bred for blood banks, as it would be preferable for cats’ welfare to live in a more natural environment.
If no feline blood is available from a blood bank, veterinary practitioners should be able to rely on an adequate number of pre-selected potential donors evaluated as low-risk cats and negative for blood-borne pathogens of interest. In any case, free-roaming cats should never be considered as potential donors. Shelter cats can potentially be considered according to their history and the quality of management of the shelter. Physical examination performed after history taking should include an accurate observation and combing of the coat to exclude the presence of fleas and ticks. Cats with fleas or ticks should not be considered as donors (Wardrop et al., 2005).
Occasional donors recruited in emergency settings always reduce the level of safety of blood transfusion. The need to find a compatible blood donor may rapidly lead to the neglect of important requirements of the donor health. Moreover, only in-house tests can be used for testing donors in emergency cases, which implies they will be screened only for retroviral infections following a physical examination, CBC, biochemical profile, and urinalysis. Records of the donor and recipient cats should be taken and an EDTA blood sample from the donor (the tube and sample taken for CBC may be used) should be kept, stored frozen at -20 °C, for possible further investigations.
The topical application of blood serum is empirically used as anticollagenolytic treatment in the medical management of deep corneal ulcers (Hartley, 2010; Mitchell, 2013; Fig. 2). The autologous preparation is cheap and easy to administer in practice but this must be performed under strict aseptic conditions as described above for the collection of blood. Sterile disposables (tube, pipette, eye dropper bottle) should be used to prevent bacterial contamination. The preparation should be stored at 4 °C and used as soon as possible (preferably within 48 hours) because the high administration frequency (up to once an hour) increases the risk of contamination of the contents of the eye drop bottle. In the case of very young kittens or the impracticality to bleed the patient, homologous (feline) or even canine serum may be used. The administration of canine serum reduces the risk of feline pathogen transmission in the ocular mucosa and damaged corneal tissue (Mitchell, 2013). In case of homologous serum, the donor should be carefully selected respecting the same criteria as used for blood transfusion. However, as there have been no controlled studies of the efficacy and safety of this therapy in cats, it should not be encouraged.
Autologous platelet-rich plasma is increasingly used for treating orthopaedic conditions in veterinary practice, including cats. Bacterial contamination during the preparation of the concentrate may occur and this risk must be reduced by strict hygiene (Hoareau et al., 2014).
Blood transfusion can be a life-saving treatment with a crucial impact on anaesthetic and surgical possibilities or intensive care but it never can be considered totally safe. The development of infectious diseases in recipient cats is an iatrogenic risk that must be minimised by the highest level of care for good clinical veterinary practice. Despite increasing data on blood-borne infections and the availability of more sensitive diagnostic techniques, the risk of transmitting pathogens using the blood of healthy infected carriers cannot be removed entirely. The most cost-effective action is to reduce this risk by the pre-selection of low-risk donors.
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