Therapeutic Plasma Exchange for IMHA

What is IMHA?

If your pet has been diagnosed with immune-mediated haemolytic anaemia (IMHA, auto-immune haemolytic anaemia, AIHA), this means their immune system is attacking and destroying their own red blood cells. This destruction is triggered by antibodies that the immune system is producing. These abnormal antibodies stick to red blood cells and mark them for destruction.

How is IMHA usually treated?

The main treatment for IMHA is drugs that suppress the immune system. However, these can take up to 5-7 days to start working. During this time, the excessive antibodies in the blood stream can continue to destroy cells, causing some patients to require multiple blood transfusions. Also, when the disease is uncontrolled, blood clots can also form in blood vessels, which can be rapidly life threatening if it occurs in the heart, lungs or brain (i.e. a stroke). Due to clot formation, traditional medical management only has a survival rate of 50-77% that is published (i.e. 23-50% of patients may not survive to leave the hospital).

What other treatments are available for IMHA?

Therapeutic Plasma Exchange or TPE is a technology newly available for dogs in Australia. At the time of writing, SASH offers the only TPE service in Australia that is performed by a team of highly qualified veterinary specialists and nurses – Dr Lucy Kopecny is the country’s only Internal Medicine Specialists with a Fellowship in Nephrology and Urology, and Dr Bing Yun Zhu, an Internal Medicine Specialist who has completed the UC Davis Hemodialysis accreditation course, with additional weeks of hands-on training at the UC Davis Hemodialysis Unit. More information about the service can be found at the Dialysis & Extracorporeal Therapies Unit page.

What is Therapeutic Plasma Exchange?

Plasma is the water component of blood that contains all the antibodies. Plasma exchange is where a machine takes blood from a patient, removes the plasma and returns the blood cells back to the patient with plasma from a donor patient. This is also how humans donate plasma to each other.

The removal of plasma is used as a first line therapy in many human immune-mediated conditions. Medication and medical management are still needed, but the hope is that this procedure can stabilise the disease a lot faster and minimise transfusion reactions.

When using plasma exchange for IMHA in dogs, we expect their survival rate to be similar or better to that of traditional management. However, we must remember that it tends to be the worst of the worst cases that receive these treatments. These are the patients that are most likely to die from IMHA based on how severe their disease is, but plasma exchange can give them equal survival chances to IMHA patients with less severe disease.

Patient receiving Therapeutic Plasma Exchange for IMHA
IMHA patient being prepared for Therapeutic Plasma Exchange

When is Therapeutic Plasma Exchange recommended for pets with IMHA?

Some animals with IMHA improve on drugs alone and may only need one blood transfusion, or uncommonly (and luckily) – no transfusion at all. It is not possible to accurately predict which patients will be the one who respond quickly and which will be the ones who have severe disease. We would typically be recommending initiation of plasma exchange if:

  • Your pet is needing its second blood transfusion (we often will perform the transfusion as part of the plasma exchange procedure)
  • Your pet is showing signs of being in the category of pets that are likely to have very bad disease (very jaundiced, very high or low white cell counts, throwing clots)
  • The size of your dog (especially if large) or frequency of need for blood transfusions would make transfusions extremely cost-prohibitive or resource prohibitive (donor blood is a precious research that come from pets of our clients and the general public). We have had situations where even our very robust blood bank runs out of donor blood.
  • The bilirubin (jaundice) level in a dog is so high it is starting to cause brain/neurological problems

Plasma exchange will be discussed with most SASH clients with pets who have been diagnosed with IMHA. Sometimes this treatment can be considered immediately before any blood transfusions to try and maximise chances of survival or control the disease as quickly as possible.

What happens to my dog during Therapeutic Plasma Exchange?

To draw blood from a patient, run it through a machine and return it to the patient, a large sized IV line (dialysis catheter) needs to be placed in a large vein. This is normally done through the jugular vein (in the neck). However, because these catheters need to be in place for a few weeks and your pet is on immune suppressant medications – it is very important that the procedure is performed extremely cleanly. In order to appropriately clean the skin and place the catheter in a sterile (germ-free) manner, most patients will require some sedative medication. If there are no complications (e.g. bruised veins, a lot of fat tissue around the neck), the placement of this catheter may take 15-20 minutes.

The placement of the IV line is the most invasive step in these treatments. During the plasma exchange procedure itself, pets will sit on a foam mattress with a car-harness clipped into the table. They are not sedated for the procedure (except in very rare circumstances where they are just moving too much). They will have enough room be able to stand up and turn around on the table.  The reason we clip them in a harness is so that they do not jump off the table and accidentally rip their catheter out.  We then hook up the machine to the patient’s catheter and put together our prescription on a machine that decides how much plasma to remove. The machine performs these functions and pumps the blood back into your pet through the same catheter. The procedure usually takes 6 hours. Initially, most animals are so sick that they just lie down on the mattress and fall asleep during the treatment. When they are better, they are often fed during their treatments. The main thing that animals may experience during the treatment itself is coldness because much of their blood may be outside their body. We often give them warm blankets and hot air blankets to help keep them warm.

IMHA plasma
Colour of plasma from an IMHA patient after rounds of plasma exchange treatment. Note the change in colour from left to right

For how man days will my dog require Therapeautic Plasma Exchange?

After the initial treatments on 1st day, 2nd day and 4th day, a lot of pets do not need any further treatments. The medication they are on usually has kicked into good effect by this stage. Other pets may need another 1-3 treatments to control their disease. It is uncommon that more plasma exchange treatments or blood transfusions are needed.

IMHA & Therapeutic Plasma Exchange Summary

IMHA is a life threatening condition with survival rates of 50-77%. Some animals only need one blood transfusion, while others need many. Although medications can stop the production of antibodies, they do not reduce the amount of existing antibodies in the blood, which will result in the need for additional blood transfusions. Medications may take 5-7 days to take effect and for some animals, the severity of their disease may be life threatening without plasma exchange to initially buy them some time.

For this reason, more and more leading veterinary hospitals across the world are starting to offer plasma exchange where the antibodies triggering the destruction of red blood cells can be removed. The primary goal of this is to improve survival in the initial hospitalisation event and control the disease as fast as possible to reduce the risk of clots and blood transfusion reactions.

It is best to start plasma exchange as early as possible because patients rarely pass away from the anaemia or procedure itself. Euthanasia or deaths are more often from the effects of the disease on other aspects of the body. The procedure itself is not overly invasive or risky in a medical sense, but it is a financial gamble whether to start plasma exchange early (within the first 1 or 2 transfusions). For some animals – it would be cheaper to start plasma exchange as early as possible (avoiding the need for long hospitalisation and multiple transfusions), while others may pull through with 2 transfusions without the need for plasma exchange.

However, if we wait too long, patients may be too sick to tolerate plasma exchange or have financially committed down one pathway so much that plasma exchange is no longer affordable. It is not possible to accurately predict which category a pet will fall into, but we may recommend plasma exchange more strongly in pets who display the previously mentioned complications with IMHA. We hope this article has helped provide the information required to make an informed decision.