When selecting blood products to use, it is worth noting the existence of component therapy to deliver targeted blood components, possibly through the UK-based not-for-profit charity Pet Blood Bank UK (PBB). Transfusing only the required component (eg fresh whole blood, packed red blood cells, fresh frozen plasma, cryoprecipitate; Pet Blood Bank, 2020) reduces the volume of the product to be administered and reduces both the anaphylactic risk and the development of any inadvertent recipient sensitisation to the unnecessary blood components that may affect the safety of future transfusions.
Prior to transfusion of any blood product, but particularly a red cell product, blood typing to determine the dog erythrocyte antigen (DEA) 1 status of the recipient should be established. This can be done quickly and easily even in an out of hours or emergency setting using an in-house kit. Establishing the recipient as DEA 1 negative or positive allows a compatible red cell product to be administered which reduces the risk of an adverse transfusion reaction during subsequent transfusions as a result of DEA 1 sensitisation. In addition, as only 30 percent of PBB blood donors are DEA 1 negative and 70 percent are DEA 1 positive, using type-matched red cells supports PBB in managing their stock levels.
A major cross-match detects existing recipient anti-bodies to any donated red cell antigen, including and beyond DEA 1, as even when DEA 1-typed blood is given correctly to patients there is still the potential to introduce other antigens that may be seen as foreign and that the patient may create antibodies against (Young et al., 1949). It is therefore recommended in dogs to perform a cross-match prior to transfusion if:
- The transfusion history of the dog is unknown
- Previous transfusions have caused a reaction
- A transfusion has been administered more than four days previously
A cross-match should be carried out prior to transfusion for the lifetime of the dog.
A compatible cross-match result means that an acute haemolytic transfusion reaction (AHTR) would be unlikely. As with blood typing, a cross-match can be carried out in-house using a commercial test kit in under 30 minutes.
STEP-BY-STEP BLOOD PRODUCT PREPARATION
Select the blood product and check the unit for any unusual discoloration, cloudiness or particles and check the bag for signs of external damage. If any of these are observed, do not administer the unit and inform PBB. Check that the unit is in date and has been stored correctly and the appropriate temperature range was maintained during storage. It is sensible to have a double-check process to confirm that the blood product selected and the DEA 1 status are correct prior to unit preparation.
Preparation of the patient
Blood products can be given by the intraosseous and central venous routes but are generally administered via a peripheral intravenous catheter. Due to blood being an ideal growth medium for bacteria, gloves should always be worn when handling the blood product and line or the intravenous catheter (IvC) being used. Confirm the IvC is in situ by disinfecting the port and flushing with sterile saline before disinfecting the port again and attaching the blood administration/extension set.
Patients are generally not given food during a transfusion, but water can be provided. It is best to avoid using the catheter to administer drugs and other fluids, especially fluids containing calcium such as Hartmann’s solution, during the transfusion. Where a drug is time critical, for example an analgesic, and cannot be given earlier or later, the drug can be administered if a second IvC is available.
Once started, the blood administration set should not be disconnected, or the transfusion stopped, except when a potential adverse reaction is occurring. Make sure patients have been walked out and have no owner visits scheduled during the transfusion window.
Monitoring for adverse transfusion reactions
The recipient should be placed in a kennel that permits constant visualisation and a transfusion nurse assigned. It is preferable to have the same nurse monitoring the entire transfusion for consistency and so subtle changes are more likely to be identified, and a specific transfusion monitoring form completed. Staff availability may need to be considered when planning a non-urgent transfusion on a busy shift.
Prior to starting the transfusion, obtain the baseline values. Pulse rate and quality, respiratory rate and effort, temperature, mentation, mucous membrane colour and capillary refill time are the minimum parameters to be monitored, as well as recording the passage of urine and faeces and their appearance, any episodes of vomiting and noting any changes in behaviour. In addition, SpO2 and arterial blood pressure can be recorded. The author prefers to attach transfusion patients to a multiparameter monitor with the ECG and blood pressure cuff attached (Figure 9) and where tolerated the rectal and pulse oximetry probes placed. This allows continuous monitoring without repeatedly disturbing the patient.
There are various forms of acute adverse transfusion reactions, including immunological reactions such as acute haemolytic transfusion reaction, febrile transfusion reaction and transfusion-related lung injury, as well as non-immunological reactions such as allergic reaction/ anaphylactic shock, erythrocyte haemolysis circulatory overload and sepsis. Signs of an acute adverse transfusion reaction include increased body temperature, increase or decrease in heart rate, weak or bounding pulses, increased respiratory rate or effort, dyspnoea, cyanosis, weakness or collapse, urticaria/erythema/oedema, hyperaemic mucous membranes, reduced mentation or responsiveness, shaking/trembling/seizures, vomiting or diarrhoea, or demonstration of unusual behaviours.
There is no one transfusion monitoring schedule; the following is based on the author’s experience:
- First 20 to 30 minutes: The nurse will remain with the patient continuously during this time, recording observations every 10 minutes
- 30 minutes to 1 hour: If there are no signs of an adverse transfusion reaction, monitoring can continue every 10 to 15 minutes
- 1 to 2 hours: If progressing uneventfully, monitor at 30-minute intervals
- 2 to 4 hours: Monitoring can be reduced to hourly
Administration of the blood product
When small volumes of blood product need to be delivered, or if the desired volume cannot be completed within four hours, the unit may be separated into smaller volumes and stored labelled in a sterile empty blood bag or syringes. If kept in the fridge at +2 to +6˚C, each syringe must be discarded after four hours at room temperature and the syringes can be kept refrigerated for 24 hours. The blood product must be passed through a filter and the product is then delivered using a syringe driver (Figure 10).
The transfusion rate is started slowly at 0.5 to 1ml/kg/hr, as the severity of an adverse reaction is, in part, related to the volume of blood that has been administered. If no signs of an adverse transfusion reaction have been observed in the first 15 to 30 minutes, the rate can be increased to 5 to 10ml/ kg/hr. Any breached unit must be discarded after four hours. Lower rates of 1 to 2ml/kg/hr should be used for patients with circulatory compromise.
The ability to control the delivery of the blood product is important for recipient safety and use of an infusion pump or syringe driver for smaller volumes allows this. The current recommendation is to check with the manufacturer if the infusion pump is compatible for delivering blood products as some studies have reported a reduced red cell survival time with this type of delivery versus gravity flow (McDevitt et al., 2011).
The blood administration set should be changed after four hours or when a new unit is to be administered. Similarly, Hemo-nate filters should be changed after every 50ml blood product, after four hours of use or whenever a new unit is attached.
Once the transfusion is complete, it is vital that a transfusion log is maintained recording each unit and its recipient so the recipient of a given unit can always be traced.