Attacking anaemia - how to care for the anaemic patient

Picture this…

It’s a Friday afternoon (of course!) and you get a call at the clinic. 

A 3-year-old Springer Spaniel has collapsed at home and is tachypnoeic, weak, and jaundiced. They’re coming down as an emergency and you need to get ready to triage and stabilise them.

We’ve all been there, right? But before we jump in to calling the blood bank and panicking about transfusions, we need to also think about what’s going on in our patient’s body, and how we can use our understanding of this to plan their nursing care. 

Anaemia is probably the most common haematologic disease that we see - so it’s vital we understand why it occurs, how it affects our patients, and what we need to do when nursing these patients.

Today we’re going to talk all about anaemia - how we classify it, what changes we see in our results, and how we treat these patients - so that you can provide the best possible nursing care.

If you want to learn even more about caring for the anaemic patient, I’m also running a special event in July which will help you do just that. Make sure you’re signed up to my email list (you also get free bonus teaching from me every fortnight, straight to your inbox!) to be the first to know when this goes live!

What is anaemia?

We can define anaemia as any of the following:

• A reduced packed cell volume (PCV)

• A reduced haematocrit (HCT)

• A decrease in red blood cell concentration 

• A decrease in haemoglobin concentration

We see anaemia due to several causes. It’s also considered a secondary condition - due to an underlying disease process - rather than a primary disease itself. 

Anaemia is either relative or absolute.

A relative anaemia is associated with fluid balance (e.g. haemodilution after fluid therapy is given, causing an increase in plasma volume). 

Absolute anaemia is caused by actual clinical disease. This is the ‘true’ anaemia we think of when we see patients like the one I mentioned earlier. We can classify anaemia in several ways - by the underlying cause, by the bone marrow’s response to the anaemia, and by the size and shape of the red blood cells.

What causes anaemia?

Really, all anaemias boil down to one of three main causes - lack of production, destruction, or loss.

A lack of RBC production (aka aplastic anaemia) is seen when the bone marrow fails to create new red blood cells. Normally, mature RBCs would be removed by the spleen, and the bone marrow would replace them with reticulocytes (immature RBCs which then mature in the bloodstream).

If there is a primary bone marrow disease or neoplasia, the bone marrow can’t do its job - so our patients end up anaemic.

Destruction is a common cause of anaemia, and occurs when there is haemolysis - red blood cell breakdown. Immune-mediated haemolytic anaemia (IMHA) is a classic example of this. These patients are able to make new RBCs as their bone marrow is working normally, but something in the body (the immune system in IMHA cases) is destroying those cells.

The last cause of anaemia is haemorrhage - whole blood loss, for example in trauma patients, or during surgery.

Patients can present with anaemia due to one or more of these three causes.

What changes do we see in our haematology?

In addition to a low PCV, haematocrit and RBC level, we can also classify our patient’s anaemia based on our haematology results.

Specifically, by the size and haemoglobin concentration of the red blood cells:

• The mean corpuscular volume (MCV) tells us about the size of our RBCs

• The mean corpuscular haemoglobin concentration (MCHC) tells us about the iron content/oxygen-carrying capability of the cells. 

These results help us determine the underlying cause of the anaemia.

Normocytic anaemia is where the RBCs are  normal in size. There are many causes of normocytic anaemia. It is commonly seen in cases of regenerative anaemia.

Microcytic anaemia is where the RBCs are small. It is generally associated with iron deficiency - this is because our RBC division increases when insufficient iron is present, resulting in smaller cells.

Hypochromic anaemia is where MCHC is low. It is commonly seen in cases of iron deficiency. 

Normochromic anaemia is anaemia with a normal MCHC. We see normochromic anaemia for a wide variety of reasons.

What about regeneration?

Anaemia can also be categorised as non-regenerative or regenerative, depending on whether new red blood cells are being released.

Figuring out if the anaemia is regenerative or not is an important step in investigating anaemia. It allows us to refine our list of differential diagnoses and guides further tests and treatments.

Regenerative anaemia

Regenerative anaemia is seen due to haemorrhage or haemolysis and is assessed by the presence of polychromasia. This is seen as an increase in reticulocytes (aka polychromatophils - our baby RBCs). 

Polychromasia can be seen on a blood film examination, and reticulocyte levels can be counted on a haematology analyser.

On microscopic examination, polychromatophils are larger than mature red blood cells and do not contain as much haemoglobin. This means they don’t absorb as much diff-quick stain, and appear a lighter purple colour.

In dogs and cats, reticulocyte levels will begin to increase after 2-5 days (depending on species) after red blood cell loss, reaching peak levels within 7-10 days. 

Erythropoietin kicks off this process. This hormone is released from the kidneys after anaemia causes a reduction in circulating oxygen levels. 

The erythropoietin stimulates the bone marrow to produce more red blood cells, causing an increase in reticulocytes released into the bloodstream. 

As this process takes a few days, a pre-regenerative anaemia may be seen if the patient presents to the clinic early enough. These patients appear to have a non-regenerative anaemia, but in actual fact the body has just not had enough time to release those reticulocytes yet.

Immune-mediated haemolytic anaemia is a regenerative anaemia, caused by antibody-mediated destruction of red blood cells.

Other causes of regenerative anaemia include pyruvate kinase deficiency; this is a genetic defect resulting in a shortened red blood cell lifespan.

Non-regenerative anaemia

In cases of non-regenerative anaemia there is no increase in reticulocyte levels. This means that a mature population of red blood cells are seen, which are not being replaced by immature cells. 

This is aplastic anaemia – where a lack of production is present.

Aplastic anaemia can be primary or secondary. 

Primary aplastic anaemia is an immune-mediated condition where the immune system attacks red blood cell precursor cells within the bone marrow. 

Secondary aplastic anaemia can occur due to various reasons, including infectious diseases, reactions to toxins and certain medications, such as immunosuppressive and cytotoxic agents. 

How do we stabilise the anaemic patient?

Anaemia is often a medical emergency. These patients can present to the clinic with severe shock, as circulating volume reduces, hypovolaemia results, and oxygen delivery to tissues is impaired secondary to red blood cell loss.

When the patient arrives at the clinic, we need to perform an immediate triage examination. 

This assessment should include an evaluation of the major body systems - the cardiovascular system, respiratory system, and neurological system.

Once your initial triage assessment is complete, we need to prioritise intravenous catheterisation and appropriate fluid resuscitation, under the direction of the veterinary surgeon. 

Supplemental oxygen should also be provided. This is important as a small amount of oxygen is transported dissolved in plasma - so this will continue even when there are less RBCs.

How do we diagnose anaemia?

There are many diagnostic tests used to investigate anaemia. We use these both to assess how severe the patient’s anaemia is and to understand the underlying cause. We also perform tests to prepare the patient for blood transfusions, where this is required.

Common diagnostics include:

• Full haematology

• Blood smear examination

• PCV and total solids measurement

• Full biochemistry

• Infectious disease testing – e.g. FeLV/FIV in cats, 4Dx (tick-borne disease panel) in dogs

• Blood typing +/- cross-matching (where a transfusion is required)

• In-saline agglutination (+/- Coombs Test) to test for IMHA

• Abdominal ultrasound +/- thoracic X-ray to determine any underlying cause (e.g. neoplasia)

• Bone marrow aspirate and core biopsy to examine red blood cell precursor cells, if required.

We’ve diagnosed our patient - how do we treat them?

Treatment of anaemia is based on managing the underlying cause. Common treatment options include:

Blood product transfusion 

Where required, the patient should be transfused with a suitable type-matched blood product. 

The idea with transfusion medicine is to replace only what’s lost. This means if you have a patient with haemorrhage, whole blood is the most suitable replacement fluid.

Where red blood cells are destroyed or not produced, packed red blood cells is a more appropriate choice, since the patient is only losing RBCs, not plasma or other blood components.

Immunosuppression

Immunosuppressive drugs are required in the management of IMHA. 

These typically include glucocorticoids (steroids), and in severe cases, an additional second-line immunosuppressive agent. 

These medications have health and safety considerations and cause polyuria and polydipsia, so they should be handled with care and the patient given regular toileting opportunities.

Supportive treatments

Supportive care may include the provision of:

• Supplemental oxygen

• Antithrombotic agents (since IMHA patients love to throw clots!)

• Analgesia

• Gastro-protectants,

• or other medications depending on the underlying cause of the anaemia.

How will we nurse our anaemic patient?

There’s a LOT to think about when it comes to anaemic patient care.

In addition to general nursing care requirements, the following areas should be considered:

Monitoring

The patient should receive regular clinical assessments, particularly parameters such as heart rate, pulse quality, blood pressure, mucous membrane colour, capillary refill time, and assessment of mentation and temperature, in order to assess perfusion status. 

The frequency of these observations should be tailored to the individual patient and the severity of their disease.

Blood product transfusion

Patients requiring blood product transfusions require intensive nursing monitoring for the duration of their transfusion (typically 4-6 hours), in order to identify any transfusion reaction. 

TPR’s, blood pressure, mucous membrane and CRT assessments should be repeated initially every 10 minutes for the first 30 minutes of the transfusion, before being reduced to every 15-30 minutes until the transfusion is completed.

We’re talking all about transfusions as a separate post, so that’s coming up in the next few weeks!

Prioritising rest and sleep

Anaemic patients can tire easily and have a lower tolerance for handling, procedures and exercise. This is because they have a reduced oxygen-carrying capacity compared with healthy patients!

We must consider this when planning nursing care, and treatment times scheduled in a way which maximises rest and sleep between periods of patient contact. 

'Lights-off' time should be provided where possible, to facilitate rest and keep the patient calm.

Nutrition

The patient’s resting energy requirement should be calculated, and quantities of food offered and consumed should be recorded. 

Where anorexia or hyporexia (below 80-85% RER) persists for >2-3 days, we need to provide assisted nutrition - ideally with a feeding tube.

Fluid balance

We need to regularly assess our patient’s volume status and their hydration status, and administer appropriate fluid therapy. 

Remember - fluids are a drug, and have risks and considerations just like any other medication! So monitoring for signs of overload or insufficient administration is a vital part of our care.

In addition, intravenous catheters should be regularly checked for signs of phlebitis, flushed and re-bandaged at least twice a day.

So that’s a brief overview of why anaemia occurs, how we classify and diagnose different causes of anaemia, and how we nurse these patients! 

What types of anaemia do you commonly see in practice, and what are your biggest nursing takeaways from today’s post? DM me on Instagram and let me know - I can’t wait to hear from you!

And don’t forget, if you want early access to the live event in July, make sure you’re on the mailing list here! I’m so excited to share more about this with you over the next few weeks!

References

1.  Day, MJ and Kohn, B. 2012. BSAVA Manual of Canine and Feline Haematology and Transfusion Medicine. 2nd ed. Gloucester: BSAVA.

2.  EClinPath. 2013. Haematology [Available from: http://eclinpath.com/hematology/].

3.  Merrill, L. 2012. Small Animal Internal Medicine for Veterinary Technicians and Nurses. 1st ed. Iowa: Wiley-Blackwell.

4.  Sirois, M. 2020. Laboratory Procedures for Veterinary Technicians. 7th edition. Missouri: Elsevier.

Treatment

Treatment of anaemia is based on managing the underlying cause. Common treatment options include:

• Blood product transfusion where required, with a suitable type-matched blood product. In cases of haemorrhage, whole blood is the most suitable replacement fluid; where red blood cells are destroyed or not produced, packed red blood cells is a more appropriate choice.

• Immunosuppressive agents are required in the management of IMHA. These typically include glucocorticoids, and in severe cases, an additional second-line immunosuppressive agent. These medications have health and safety considerations and cause polyuria and polydipsia, so they should be handled with care and the patient given regular toileting opportunities.

• Supportive care may include the provision of supplemental oxygen, anti-thrombotic agents, analgesia, gastro-protectants or other medications depending on the underlying cause of the anaemia.

Nursing Care

Nursing care requirements for the anaemic patient are vast. In addition to general nursing care requirements, the following areas should be considered:

• Monitoring: The patient should receive regular clinical assessments, particularly parameters such as heart rate, pulse quality, blood pressure, mucous membrane colour, capillary refill time, and assessment of mentation and temperature, in order to assess perfusion status. The frequency of these observations should be tailored to the individual patient and the severity of their disease.

• Blood product transfusion: Patients requiring blood product transfusions require intensive nursing monitoring for the duration of their transfusion (typically 4-6 hours), in order to identify any transfusion reaction. TPR’s, blood pressure, mucous membrane and CRT assessments should be repeated initially every 10 minutes for the first 30 minutes of the transfusion, before being reduced to every 15-30 minutes until the transfusion is completed.

• Prioritising rest and sleep: Anaemic patients can tire easily and have a lower tolerance for handling, procedures and exercise since they have a reduced oxygen-carrying capacity. This should be considered when planning nursing care, and treatment times scheduled in a way which maximises rest and sleep between periods of patient contact. 'Lights-off' time should be provided where possible, to facilitate rest and keep the patient calm.

• Nutrition: The patient’s resting energy requirement should be calculated, and quantities of food offered and consumed should be recorded. Where anorexia or hyporexia (below 80-85% RER) persists for >2-3 days, appropriate enteral feeding support should be provided.

• Fluid Balance: The patient’s hydration and volaemic status should be assessed and appropriate fluid therapy administered, at a rate determined by the patient’s individual signs. Fluid therapy requirements should be regularly reassessed depending on the rate and duration of treatment, to prevent over or under-hydration, and to prevent marked haemodilution and an associated reduction in PCV. Intravenous catheters should be regularly checked for signs of phlebitis, flushed and re-bandaged at least twice a day.

So that’s a brief overview of why anaemia occurs, how we classify and diagnose different causes of anaemia, and how we nurse these patients! What types of anaemia do you commonly see in practice, and what are your biggest nursing takeaways from today’s post? Be sure to drop them in the comments below, and stay tuned for posts on other haematological disorders, IMHA, blood transfusions and more!

References

1. Day, MJ and Kohn, B. 2012. BSAVA Manual of Canine and Feline Haematology and Transfusion Medicine. 2nd ed. Gloucester: BSAVA.

2. EClinPath. 2013. Haematology [Available from: http://eclinpath.com/hematology/].

3. Merrill, L. 2012. Small Animal Internal Medicine for Veterinary Technicians and Nurses. 1st ed. Iowa: Wiley-Blackwell.

4. Sirois, M. 2020. Laboratory Procedures for Veterinary Technicians. 7th edition. Missouri: Elsevier.