Blood Transfusions Flashcards
(41 cards)
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)
Where are the uses of oxyglobin and where should we take care?
–Uses
•Anaemia and circulatory collapse
–Care with volume replete patients
–Particularly useful where rapid (temporary) oxygen provision is required
–Due to the heavy colour of the product this influences some clinical pathology parameters
•Colorimetric assays are affected
–Biochemistry and optical coagulation methods
–Haematology parameters are less affected
–However those machines directly measuring Hb will also measure the oxyglobin
–Care with repeated administration due to antibody development
•However these do not seem to influence oxygen carriage
Do we have a feline blood bank?
–At present there is no repository for feline blood or blood products in the UK
•Problem with storage of feline blood is absence of true closed collection system
–This may change over the next few years
- Available in the USA
- However in UK major problem is with collection methods and ethics associated with this
–Until then whole blood should be obtained from practice based donor schemes
–Human albumin has been used with some success in hypoalbuminaemic cats and caveats are the same as that seen in dogs
How much blood do you transfuse? Dogs/cats?
•This has had recent scrutiny however previous equations suggested
–Dogs for donor PCV of around 45%
–2ml/kg will raise the recipients PCV by around 1%
–Cats for donor PCV of around 37%
–3ml/kg will raise the recipients PCV by 1%
•Recent publication (Short et al 2012) suggested best formulae for Dogs
–Volume to be transfused = recipients blood volume (BW in kg x 90ml) x [(desired PCV – recipient PCV)/donor PCV]
–Volume to be transfused = 1.5ml x desired PCV rise x BW in kg
•In cats reasonable formulae would be:
–Volume of whole blood (ml) = desired PCV rise (%) x BW in kg x 2
What is an older formula to decide how much to transfuse?
–Volume to be transfused (ml) = BW of recipient (kg) x average blood volume (ml/kg) for species in question* x [required PCV – current PCV]/donor PCV
–* dogs 85ml/kg, cats 60ml/kg
–For PRC rule of thumb:
•2ml PRC/kg BW raises PCV by 2%
What rate should I transfuse the blood?
–Depends on circulatory status
•It is possible to use blood as a colloid and as a shock/replacement fluid and deliver as rapidly as possible
–Risks of calcium chelation and hypocalcaemia, influence on clotting cascade and platelet function/activation
–If animals cannot tolerate the required volume in 4 hours then this should be aliquoted and refrigerated for no longer than 24 hours
–Longer the blood is out the more the blood has a chance of septic – must put in in 4 hours
–Dogs
- Usually 0.25ml/kg/h for 10-20 minutes followed by 0.5ml/kg/h for 10-20 minutes
- If no reactions are observed then increase rate to between 5-10ml/kg/h to deliver blood within 4 hours
–Cats
•Usually 1-3ml/h for the first 10-20 minutes, if all ok then can increase rate to 5-10ml/kg/h if circulation status appropriate
How should the blood product be transfused?
- Important that LRS (hartmanns) is not co-administered with blood or blood products as this can lead to clotting or haemolysis
- Historically need to use supplementary fluid when using packed red cells to reduce viscosity
–This can be added directly to the bag or run in separately
–More recently concentration of blood in PRC means this is no longer considered necessary by some
•What about chlorpheniramine prior to starting the transfusion
–The evidence that this is essential to reduce the incidence of acute reactions is lacking
–Increases comfort level of clinician (perhaps survival?)!
•Cephalic or jugular vein (intraosseous)
•
•Filtered giving set
–removes microthrombi and other cells fragments
•Infusion pump or standard giving set?
–majority of studies in humans suggest storage of blood is major influence on administration haemolysis
–Rate or volume administered does not seem to influence integrity (slow vs. fast)
•Aim to complete transfusion within 4 hours
–This prevents contamination of blood products
•It is important not to actively warm the blood before transfusion
–This damage cells
–Increases risks of bacterial growth
–(although you should warm plasma)
–DO NOT FREEZE blood
- In dogs a standard blood unit is infused via a blood giving set which contains a filter to remove clots and other large fragments
- In cats and smaller dogs where syringe collection has been used this is best administered via a syringe driver and in-line paediatric filter
What are blood groups?
- The presence of naturally occuring antibodies to blood group antigens determines the nature and frequency of any reaction
- Dogs have very few naturally occurring antibodies to major blood groups
–Low risk of transfusion reaction
•Cats frequently have naturally occurring antibodies to major blood groups
–Increases risk of transfusion reaction
•Rare to blood transfuse cat – must tell them it might kill them – theyd have to be dying anyway (best to refer if poss to type them)
Whata re the main blood groups in dogs?
–There are >10 blood group systems
•Dog erythrocyte antigen (DEA)
–There are 6 of these 1.1,1.2, (1.3), 3, 4, 5 and 7
–Alternate – 1, 3, 4, 5 and 7
- Dal
- Kai
