Supportive care of the anemic cat Flashcards
What are the clinical signs indicating a blood transfusion is required
Clinical signs for a blood transfusion are:
- lethargy
- collapse
- tachypnoea
- tachycardia (might not be observed in some feline patients)
- bounding femoral pulses
When a pre-emptive blood transfusion may be considered
A pre-emptive blood transfusion may be considered if:
- a surgical procedure is planned for a cat that is already mildly to moderately anemic
- if excessive hemorrhage during surgery is anticipated
How is the blood group system characterized in cats
The blood group system in cats is characterized by three phenotypes: A, B and AB
The group are defined by the presence of antibodies in the cat’s serum against the antigen that the cat lacks
- unlike dogs, the presence of these antibodies does not require prior exposure
- they are naturally occuring
- these antibodies are known as alloantibodies and are responsible for potentially fatal blood transfusion reactions that can arise even when cats undergo their first blood transfusion, as they are already in the cat’s circulation
What is the prevalence of allo-antibodies according to the blood group of the cat
Type A cats:
- generally have low levels of anti-B allo-antibodies
Type B cats:
- generally have moderate to high levels of anti-A allo-antibodies
- severe immediate hypersensitivity occurs when Type-B cats receive even small amounts of Type-A blood
Type AB cats:
- no allo-antibodies to either A or B antigens
What is the prevalence of blood groups among cats
The prevalence of blood group type varies between breed and geographical location
Type A is the most common in the domestic crossbreed population (nearly 100% in USA, Europe)
The cat’s breed also influences the likelihood of being a certain blood type:
- Siamese, Tonkinese, Oriental nearly 100% Type A
- Burmses, Maine Coon, Norwegian > 93% Type A
- British and Exotic shorthair, Devon Rex, Cornish, Ragdoll 40-72% Type A
What is the mode of inheritance of feline blood groups
Studies of the inheritance of feline blood-group types have found that the Type A genotype is dominant overt Type B
Type A cats can be genotype AA, Aa^ab or Ab
Type AB cats are aabb or a^ab a^ab
Type B cats are always bb
What is the principle of blood typing
Blood typing determines the type of antigens on the RBC surface
What is the principle of cross matching
Cross matching detects the presence of potentially cross reactive antibodies in the sera of the donor and recipient
Generally, blood typing is all that is required in cats that have never had a blood transfusion
Why should it be view as good practice to cross match blood even in a cat without previous blood transfusion
The presence of another previously unknown RBC antigen (called Mik) and consequent naturally occuring anti-Mik antibodies in some Mik-negative cats may render transfusions incompatible even in cats of the same A/B blood type
Thus, it has been suggested that cross matching prior to transfusions be carried out if possible
The prevalence of Mik-antigen negative cats is unknown and cats with Mik antigen have not been identified outside the USA
What are the criteria for a cat to be a blood donor
Donor cats should:
- be housed indoors to minimize exposure to diseases such as FIV and FeLV
- be screened for hemoplasmas via PCR
- have good flea control, be up to date with relevant vaccination and worming
- FIV PCR testing if recently involved in a fight
- should be screened for FeLV by both ELISA and PCR
- have echocardiographic screening because occult cardiomyopathy is prevalent in cats
- be young to middle aged (1-8 years) healthy individuals with no current medications
- > 4.5 kg lean bodyweight for regular donors
- have a calm temperament
- have never received a transfusion nor be currently pregnant
Donors can be used every 4-8 weeks
- providing their PCV is within the normal range
If cats are being used regularly for donation, they should be supplemented with ferrous sulfate
- at least 30 mg per blood donation
How is blood collected for a blood transfusion
Usually the donor cat is anesthesized or heavily sedated
An IV catheter is placed in a cephalic vein
The cat is positioned in lateral recumbency, the head is extended and an area over the uppermost jugular vein is clipped and surgically prepared
A 20 gauge butterfly needle attached to a 3-way stopcock is primed with anti-coagulant
The neck is held in extenesion and the jugular vein is punctured
Connect both 25 ml syringes to the three-way stopcock before commencement of blood collection
The syringes are gently rocked to ensure adequate mixture of blood and anti-coagulant
During collection, concurrently administer 100 ml of 0.9% saline to the donor
Anticoagulant for blood unit collection: CPDA-1 7ml per 50 ml of blood
As this is not a closed collection system, the blood should be given to the recipient immediattely
How would you administer blood transfusion to recipient patient
The aim is to give enough blood to obtain a post-transfusion PCV of 20% or at least to improve demeanor and clinical signs
Assuming a donor PCV of 30%, roughly 2 ml/kg of whole blood will theorrtically increase the recipient’s PCV by 1%
Formulas for predicting post-transfusion PCVs are very unreliable in cats
Often approximately 30-50 ml of blood are obtained from the donor and administered
Cats that have not had previous blood transfusion do not need to be pre-medicated
- if the cat has had a previous transfusion, a cross-match with the donor blood should be performed
- chlorpheniramine or diphenydramine can be given to ameliorate histamine-mediated reactions in cats that have received previous transfusions
The transfusion should be given through a filtered blood administration set to prevent blood clots entering the patient’s circulation
Only saline should be co-administered with blood products
- the calcium in Hartmann’s solution can cause clotting
The transfusion should be completed within 4 hours to prevent bacterial contamination
Blood should be administered slowly for the first 30 moniutes (0.25-0.5 ml/kg/h) and the petient monitored closely for any signs of reaction
- heart rate, respiratory rate, body temperature, gum color should be monitored every 5 minutes for 30 minutes, then every 15 minutes for the first hour, then every 30 minutes for the remainder of the transfusion
- if no transfusion reaction is noted, the rate may be increased to 1 ml/kg/h for 15 min and so on as needed
- often the first sign that might be seen in a cat is vocalisation
- in cats with heart failure or cardiac disease, the infusion rate should not exceed 2 to 4 ml/kg/h
If reactions are observed (i.e., vocalisation, tachycardia, hypersalivation, vomiting, diarrhoea, facial swelling/urticaria, tachypnoea/respiratory distress), the transfusion should be stopped immediately
A PCV and total protein level should be measured about 1 hour after completeion of the transfusion
- a significant increase in PCV rarely occurs, however the cat is usually clinically improved following blood administration
What is the difference between whole blood and packed RBCs (pRBCs) for transfusion
Whole blood contains RBCs, serum proteins, clotting factors, and platelets
- platelets are lost after 2 to 4 hours
- function of factors V and VIII is lost after 24 hours
- whole blood transfusions are generally indicated for anemia as a result of hemostatic disorders or with concurrent hypoproteinemia
Packed RBCs will provide the same degree of oxygen-carrying capacity as whole blood, but in a significantly smaller volume
- it is better to use pRBCs in normovolemic patients that are anemic from blood loss, hemolysis, or ineffective erythropoiesis
- if volume overload is a concern (e.g., cardiac conditions), pRBCs are preferable
