Blood Transfusions Flashcards
Define blood transfusion
Intravenous therapy with whole blood or blood products.
What are blood products?
Blood components
What is oxyglobin?
Chemically modified haemoglobin of bovine origin.
What to transfuse and why?
•TRY to establish why you think the dog or cat is anaemic
–Helps determine WHAT you should be transfusing (less so cats)
–E.g. haemorrhage, haemolysis or erythropoietic failure
- This may not be apparent initially but must be considered in addition to your transfusion plans
- If the animal is bleeding its demand for and the type of blood products required will be very different
- Care if not bleeding with products with high oncotic pressures…
–Careful history from the owner will be invaluable for planning appropriately in these cases
•What is the duration of the anaemia, clinical signs associated with
–Short term, medium term or long-term
- Evidence for reduced oxygen carrying capacity?
- Replace what is lacking
•
- Supports patient whilst investigations are being carried out/treatment is being initiated
- Aim for a clinical improvement rather than a normal PCV.
–Post-transfusion PCV of 25 to 30% in dogs
20% in cats
- Remember the benefits of transfusion MUST outweigh the drawbacks
- Responses to transfusion tend to depend on how quickly they became anaemic
Name iminent triggers for transfusion
–Evidence for circulatory collapse means transfusion is essential
–Rapid drop in PCV to <20% in dogs or <15% in cats (e.g. 10% or more)
–Absolute PCV of 15-20%
•Depends a lot on historical and presenting clinical signs
–If PCV <10-12%, automatic trigger as organ hypoxia is imminent – particularly myocardium
–Signs of specific organ hypoxia – particularly CNS
–Clear evidence for reduced oxygen carrying capacity
•Tachycardia, Tachypnoea, bounding peripheral pulse (water-hammer – rapid rise and fall of pulse)
–(Concern that PCV is likely to fall lower over period of time whereby transfusion would be difficult to organize e.g. Friday afternoon)
Why is the transfusion product important?
- Don’t want to give them more than we need
- The importance relies on our ability to assess suitability of the use of each of the products
–A diagnosis is required to ensure appropriate product choice
•e.g. IMHA, whole blood loss, deficiency in Vit-K dependent clotting factors, hypoproteinaemia and secondary pro-coagulability
–if we only need coagulation factor replacement many of the products are suitable
- Some contain more than you need – risks?
- Some may contain less – risks?
- Identifying the main reason for using the product is important
What products are available for transfusion?
–Products containing everything
•Whole blood products
–Products containing cells
•PRBC, platelet products, (WBC)
–Products containing plasma proteins
•Plasma and its fractions
–Products containing none of the above
•Oxygen carrying solutions
What products do we use most frequently and why?
- Fresh whole blood – surgery
- Packed red blood cells (most commonly used as hemolytic anaemia is common)
- Fresh frozen plasma – coagulopathy
Discuss fresh whole blood
–‘Unadulterated’ blood from a suitable donor
–Should be harvested aseptically into closed collection system
–Single unit is ~450ml
–Must be transfused within 8 hours or must be refrigerated after collection – becomes SWB
–All blood products are present and functional
•Red cells, platelets, WBC, labile and non-labile clotting factors
–Most common agent transfused in private practices
–Most appropriate for animals that are haemorrhaging
- Coagulopathies
- Thrombocytopaenia
- Whole blood loss due to trauma/surgical complications
Discuss stored whole blood
–Fresh whole blood that is not transfused within 8 hours can be stored in fridge (<4°C)
–Storage life of SWB is around 3-5 weeks depending on anticoagulant used
–The major difference cf. FWB is the lack of platelets, white blood cells and labile clotting factors (FV, FVIII and vWF)
•Valuable in haemorrhage due to trauma (less ideal that FWB), vitamin K dependent rodenticide toxicity, coagulopathies due to liver disease (where whole blood is not contraindicated)
–Once transfusion has begun MUST be completed within 4 hours
Discuss packed red cells
–This is prepared from whole blood by centrifugation
–The whole blood is collected into a system where there is an extra bag for the plasma to be separated
–The red cells are then resuspended in small volume of plasma and nutrient solution
- E.g. SAG-M (Sodium chloride, Adenine, Glucose, Mannitol)
- Unit volume ~ 250ml
–PCV of this is between 70-80% (depending on starting PCV)
- Shelf life is between 3-6 weeks depending on preservative used (SAG-M provides up to 6 weeks shelf life)
- Should be stored to enable air to circulate around units
- Indications:
–Anaemia due to haemolysis/chronic disease/erythropoietic failure
»Where patients are volume replete
–Can use this in conjunction with colloidal solution in animals needing whole blood if unavailable
- Saline was historically introduced into the bag or coadministered during transfusion
- No longer considered necessary
Discus autologous transfusion
–Often overlooked source of recipient matched blood
- harvest blood ready for later transfusion when anticipating haemorrhage
- acute cavity haemorrhage due to trauma/coagulopathies
–Caution if there is other organ damage – such as urinary or gall bladder
–Benefits of reducing potential for exposure to allogenic blood, reduces risk of (new) infectious diseases, reduces chance of transfusion reactions, immediate availability (!)
–Scavenging systems are available to harvest the blood however these are not considered essential
•Surgical suction catheters, dialysis catheters or needles can be used as long as sterility is assured
–Cavity blood can be drawn into sterile syringes and driven back into the patient using an in-line filter or placed aseptically into sterile freshly emptied fluid bags delivered via blood giving set, depending on volume
–Survival of the replaced autologous blood is better when transfused using gravity feed
•This is thought at least in part due to increased osmotic fragility from contact with serosal surfaces
–Risks include sepsis and dissemination of neoplasia. The dissemination of neoplasia is a theoretical concern, which may be borne out by immediate survival of the patient.
- No need to anticoagulate if has been present in body cavity for >1 hour
- If <1 hour then anticoagulation is recommended (although in cases of coagulopathy this would be of questionable benefit)
Discuss fresh frozen plasma. Indications for use?
–This is plasma harvested from fresh whole blood (historically) within 8 hours of collection
•More recent data would suggest ok within 24 hours
–Provides maximal concentrations of all factors
–Dose: 6-10ml/kg every 12hrs (up to 20ml/kg for severe coagulopathy)
–If stored
•Although may be longer……
–Indications for use
–Acquired or inherited coagulopathies
–DIC, pancreatitis (?)
–Liver disease
–Perioperative use for vWD or other inherited coagulopathies
–Once defrosted or after fresh is collected, it should be used within 5 days
–It should NOT be used for albumin replacement or as colloidal therapy due to the volume required to increase the plasma oncotic pressure and albumin concentration
–Recent study has suggested that transfusion of freeze thaw cycled fresh frozen plasma (refrozen within 1 hour of defrosting) is expected to provide the recipient with comparable replacement of hemostatic proteins as FFP that has remained frozen
Discuss stored plasma/frozen plasma. Uses?
–This is the term used to describe FFP which is >1 year old
–OR FFP that has been thawed or separated from whole blood >8 hours after collection
•However new data would suggest that up to 24 hours is acceptable to prepare FFP
–Some factor activity lost (particularly labile factors)
•However vitamin K dependent factors (II, VII, IX and X) are not labile and so should be functional
–Can use up to 5 years from preparation if stored at
- Standard unit is ~200ml
- Dose is ~10-20ml/kg
–Standard approach to transfusion
–Uses –
- Anticoagulant rodenticide toxicity, Haemophilia B
- Liver disease, DIC, pancreatitis (?)
Discuss oxyglobin
–Currently unavailable!! (prevoiusly Dechra Veterinary Products)
–Cell free bovine polymerised haemoglobin in LRS
•Slows clearance from vasculature
–Stored as deoxyhaemoglobin
–Binds oxygen less tightly that normal RBC-Hb
•This improves dissociation at lower tissue oxygen conc
–Once opened should discard within 24 hours
- Methaemoglobin develops which is irreversible
- no preservative – high risk of bacterial growth
–Has significant colloidal influence as well as oxygen carrying capacity
•Low doses therefore are recommended in cats
–No preservative! – bag needs to be used/thrown away
Discuss oxyglobin doses
–Impact and duration of effect is dose dependent
- 10ml/kg theoretical PCV increase ~3%, duration 11-23h
- 30ml/kg theoretical PCV increase ~12%, duration 74-82h
–In dogs
- dose should not exceed 30ml/kg in given 24 hour period
- Rate should not exceed 10ml/kg/hr
–In cats
- Dose should not exceed 10ml/kg in given 24 hour period
- Rate should not exceed 3ml/kg/hr (0.5-2ml/kg/h)
