5 top tips to help you care for your haematology patients
Tell me if this sounds familiar…
You’ve got an anaemic patient in the hospital. You’ve made a smear and you’d like to take a look at it, but you’re not really sure what you’re looking for - so you stain it and leave it to dry for the vet to look at, then send the rest of the sample off for external analysis.
After this, the vet asks you to administer some packed RBCs to the patient. They arrive from the blood bank, and you’re handed the bag and told how much to administer.
You do it as directed - but what if I told you that you can - and should - be helping to make these transfusion plans for your patient? And that there is a really easy way to know exactly how to troubleshoot transfusion reactions, and know exactly what to look out for when monitoring your patient?
In today’s post, we’re continuing our ‘Up Your Medical Nursing Skills’ series by looking at 5 skills we can use when caring for haematology patients. From making the most of tiny samples from anaemic patients, to selecting a blood product and transfusing it, to looking at smears, you’ll leave today’s post feeling much more confident about haematology nursing.
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#1: How to examine a blood smear
Blood smear examination is a vital skill for the veterinary nurse - and it’s often something we don’t do enough!
Here’s how to do it 6 quick and easy steps:
Prepare and stain a blood smear.
Scan the smear initially on low power.
Look in the feathered edge for platelet clumps, before scanning the rest of the smear to identify optimal areas for cell counting.
Increase the magnification (x 40-100) and examine the cells in the monolayer (the area just behind the feathered edge, where the slide is more densely populated but still one cell thick).
Perform any counts as needed, such as a manual platelet count or white blood cell differential count.
Assess the cells for changes in morphology - for example, cells of differing size, shape, colour, and whether any inclusions are present.
#2: How to interpret a PCV with a tiny sample
Anaemic patients are those challenging ones that need us to work nursing magic - that is, run as many tests as we can from the smallest sample imaginable.
So if you’re in a situation where you need to magic up a PCV from a sample that’s too small to fit in your reader, here’s a quick and easy way to do it:
Create your PCV tubes and centrifuge them.
Grab a ruler or measuring tape.
Line the bottom of the cell column (the top of the putty line) with the ‘zero’ line on your ruler/measuring tape.
Measure the length of the RBCs in mm.
Measure the length of the whole sample (packed cells and plasma) in mm.
Divide the length of the RBCs by the length of the whole sample, then multiply this by 100.
And there you have it - your PCV, without the need for a reader! This works with samples of any length, so the next time you think you don’t have enough sample to check a PCV, remember this hack and think again!
#3: How to work out what blood product your patient needs
There are SO many options out there when it comes to transfusions. But how do we know which product our patient needs?
Most of our patients will need one of five blood products. These are:
Fresh whole blood (which is collected and transfused within 4-6 hours)
Stored whole blood (which can be stored for up to 28 days in most cases)
Packed RBCs (which contains red blood cells +/- white blood cells and non-viable platelets, in a small amount of plasma and nutrient mix)
Fresh frozen plasma (which contains all clotting factors, plasma proteins +/- some WBCs and non-viable platelets)
Frozen plasma (aka stored plasma, which contains most clotting factors, and all other plasma components as above)
By using blood components, rather than whole blood for every patient, we can meet their individual needs whilst giving unnecessary blood products. This minimises the risk of adverse events.
For example, if we were to give whole blood to an IMHA patient, we’re giving them a ton of plasma that they don’t need - increasing their risk of volume overload.
So let’s look at which blood products are indicated for which patients:
Whole Blood
Generally, we want to replace only the portion of blood that’s been lost. So whole blood is indicated for patients with haemorrhage - where they’ve lost not just red blood cells, but plasma too.
In most cases, stored whole blood is acceptable - there is one exception to this, though, and that’s in patients with thrombocytopenia.
The reason for this is that stored whole blood is not a source of viable platelets. So if a patient has become transfusion-dependent from haemorrhage secondary to thrombocytopenia, they’ll need a fresh whole blood transfusion.
Packed RBCs
Packed RBCs are indicated for use in anaemic patients. These patients do not need plasma but have a decrease in their PCV, haematocrit or RBC level meaning they need additional RBCs.
Fresh Frozen Plasma
Fresh frozen plasma is used in patients with coagulopathies in most cases. Many coagulopathies can be managed with frozen plasma, since this also contains many of our clotting factors.
However, 2 congenital coagulopathies specifically require FFP: von Willebrand’s disease, and haemophilia A.
Why? Because von Willebrand’s factor and factor VIII - the factors deficient in these diseases, respectively, are known as ‘labile’ clotting factors. This means that they aren’t as reliably present in older blood products, or in blood where there has been a delay in separating and freezing it.
Fresh frozen plasma is known to reliably contain these factors - so it is indicated for use in these patients.
Frozen Plasma
Frozen plasma has many of the same indications as FFP - except those von Willebrand and haemophilia A patients. It can be used in all other coagulopathies, including anticoagulant rodenticide toxicity and haemophilia B (factor IX deficiency).
There are also other indications for plasma administration, including in patients who would benefit from immunoglobulins - such as patients with pancreatitis, or parvovirus.
And of course, this is by no means an exhaustive list - there are other products for example, like cryoprecipitate, that are used in very specific circumstances. To read more about blood products, check out this post.
#4: How to calculate transfusion requirements
So you’ve picked your product and you’re getting ready to administer it. But how do you calculate your patient’s transfusion requirement and rate?
Well, this depends on whether you’re giving a red blood cell-containing product or a plasma product. Let’s take a look:
Whole blood or packed RBCs
The first thing we need to do is figure out how much blood our patient needs. We do this using this formula:
Volume required = (blood volume x recipient bodyweight) x (target PCV – current PCV)
/ Donor or blood product PCV
Put simply, we are looking at what the patient’s normal blood volume is, multiplied by the amount we want to increase their PCV by, divided by the PCV of the blood product you’re giving.
This tells us how much of this particular bag of blood our patient needs, to increase their PCV to the target figure.
The normal blood volume is a species-specific constant and is approximately 85-90ml/kg for dogs and 60-65ml/kg for cats.
We ideally want to give the whole transfusion over about 4 hours. This is because the risk of bacterial contamination increases the longer a blood product is broached - because it contains no preservatives.
In patients with cardiac or renal disease or those at risk of volume overload, the transfusion may have to be given over a longer period (ideally not over 6 hours, if possible, due to the risk of contamination).
We begin at a slow rate (usually 0.5ml/kg/hour) for the first 30 minutes, in case a reaction is seen. If everything is ok after this, we’ll increase the rate to deliver the rest of the transfusion within that 4-6 hour period.
What about plasma products?
We don’t need to worry about the PCV when we’re calculating plasma transfusion rates. Instead, we generally give our patients 10-30ml/kg of either FFP or FP, over 4-6 hours.
Like whole blood or RBCs, we begin at a slower rate initially and increase this if no signs of a transfusion reaction are seen.
#5: How to spot the signs of a transfusion reaction
Speaking of transfusion reactions, how do we recognise one? And more importantly, what do we do if our patient has one?
Well, the answer to this is that it depends on the type of transfusion reaction seen. There are many different reactions, which we can broadly classify as:
Immunological - caused by the immune system
Non-immunological - varied causes, not via the immune system
Haemolytic - where RBCs are destroyed
Non-haemolytic - where RBCs are not destroyed
Haemolytic reactions
These are caused by antibodies against red blood cell antigens, for example, a type B cat given type A blood.
This causes rapid destruction of the donor’s red blood cells and when this happens acutely, is an emergency as the reaction can be fatal.
Haemolytic reactions can be acute (within the first 15 minutes of the transfusion) or delayed (up to 21 days after the transfusion).
Clinical signs of an acute haemolytic reaction include:
Pyrexia
Tachycardia
Dyspnoea
Hypotension
Seizures
Cardiac arrhythmias
Hypotension
Potentially cardiac arrest
Non-haemolytic reactions
These are antibody-associated reactions to proteins, platelets and white blood cells within plasma products.
These reactions can be seen during the transfusion or shortly afterwards, and clinical signs are similar to allergic/anaphylactic reactions. Pyrexia, hives, itching, redness, vomiting and oedema are commonly seen.
Non-immunological reactions
Non-immunological reactions are varied and have lots of underlying causes. They include:
Microbial contamination of the blood product
Infectious disease transmission from donor to recipient
Pre-transfusion haemolysis (caused by overheating or improper handling/preparation of the blood product)
Another important non-immunological reaction is citrate toxicity. This occurs when there is too much anticoagulant for the volume of blood collected from the donor. The citrate in the anticoagulant binds to calcium in the body, causing hypocalcaemia and cardiac arrhythmias.
How do we manage a reaction?
If signs of a transfusion reaction are seen (or if you suspect them), the transfusion should be immediately stopped and the veterinary surgeon informed.
We then want to direct our attention to these transfusion reaction guidelines. These provide handy flow charts of exactly what to monitor and how to troubleshoot the different types of reactions we see.
If you’re in a practice that transfuses regularly, I’d really recommend having a copy of these charts printed and laminated so you have them to refer back to!
So that’s this week’s top tips for managing haematology patients! From examining blood smears to running other diagnostics, selecting and calculating transfusions and monitoring for reactions, there are so many skills nurses can use with these patients!
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