Plus-Hex CLINICAL
The solid components of blood are the blood cells , known as erythrocytes , leukocytes and thrombocytes . Erythrocytes , also referred to as red blood cells ( RBCs ), are the most abundant blood cell and are responsible for the transport of oxygen to the tissues . A decline in the number of circulating erythrocytes is defined as anaemia and ongoing loss will eventually lead to decreased tissue oxygen consumption ( Garcia & South- Bodiford , 2012 ). In current practice , PRBC transfusions are commonly used to treat patients that are anaemic , whether this is from immune-mediated disease , acute haemorrhage or decreased production of erythrocytes ( Walker , 2016 ) ( Table 3 ). It should be noted that deciding to transfuse a patient with PRBCs based upon laboratory results alone is not recommended . However , a transfusion may be necessary if the patient shows signs of hypoxia due to anaemia ( Yagi , 2021 ) ( Table 4 ).
Table 4 . Clinical signs of anaemia ( Yagi , 2021 ).
Clinical signs of anaemia
• Tachycardia
• Tachypnoea
• Increased respiratory effort
• Pale mucous membranes
Blood typing and cross-matching
Blood typing identifies the presence of a specific antigen on the surface of the animal ' s RBCs . Cross-matching assesses whether any components of a recipient ' s blood will react with any of the donor ' s blood . Blood typing and cross-matching recipients against potential donors can prevent immunological transfusion reactions by avoiding the administration of incompatible blood products ( Walton & Tappin , 2017 ). Type I and type II hypersensitivity and acute haemolytic transfusion ( AHR ) reactions are examples of immunological responses in which a patient ' s immune system triggers antibody release against the mismatched antigen ( Yagi , 2021 ). Cross-matching is achieved by visually inspecting for agglutination during sample mixing ( Webb , 2019 ).
DEA ANTIGEN
In dogs , the most significant blood types have been assigned the prefix DEA ( dog erythrocyte antigen ) ( Kendon & McMichael , 2020 ). Webb ( 2019 ) details that it is the antigen DEA 1 that is most likely to cause an AHR in patients that are originally DEA 1 negative and is therefore the most clinically significant . As a result , inhouse canine blood-typing kits have been developed to determine the presence of the DEA 1 antigen , allowing practices to administer initial blood transfusions safely depending on the patient ' s DEA 1 status ( Figure 2 ).
• Weakness / lethargy
• Dull mentation
Leukocytes are less numerous compared with erythrocytes but they play a major role in the body ' s defence against infection , and function closely with the body ' s immune system ( Aspinall & Cappello , 2009 ). The immune system ' s function is to protect the body against infectious organisms and , for it to perform effectively , recognition molecules must recognise the presence of a pathogen by analysing a potential invader and distinguishing it as being either self or non-self .
Through evolution , the immune system has developed to allow for adaptation , so species and individuals can create their own recognition molecules , tailored by the pathogens they have already encountered ( Playfair & Bancroft , 2013 ). This is carried out by a type of leukocyte termed a lymphocyte . Once a lymphocyte has recognised an antigen , it will proliferate and instruct a response , which can include the release of antibodies or cytokines , or cytotoxicity . Once complete , a number of these proliferated cells will remain circulating throughout the blood and tissues as memory cells , allowing the individual to respond faster and more aggressively during repeat exposure to the specific antigen .
Figure 2 . Canine blood-typing kit .
Naturally occurring alloantibodies to any blood type are rare in canine patients and , even if they do exist , their risk of causing an AHR is low , so it is common practice to use the term ‘ universal donor ’ when describing patients with a DEA 1 negative status . However , because patients ' immune systems will develop alloantibodies to all foreign antigens in the days after an initial transfusion , consequently increasing the risk of delayed reactions or serious complications during subsequent transfusions , use of the term ‘ universal donor ’ should be void ( Zaremba et al ., 2019 ).
Volume 37 ( 4 ) • September 2022
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