44 | Help, my patient won't stop bleeding! How to care for common coagulopathies

HaematologyPodcastEmergency and Critical Care
Written By Laura Jones

Ever seen a young puppy present bleeding after their microchip, vaccination, or even after neutering? There’s a good chance they’ve got a coagulopathy.

 

We see two types of coagulopathy in practice - congenital and acquired - and it’s those congenital ones we’re discussing today. It’s important we pick up on these as soon as possible in the patient’s life, to prevent severe haemorrhage at the time of neutering or during other procedures.

Identifying congenital coagulopathies starts with understanding what they are, and how they impact our patients - which is exactly what you’ll be able to do after this episode.

Let’s talk about clotting

Before we dive into coagulopathies, we need to revisit coagulation briefly.

As we mentioned in episode 42, clotting factors turn a platelet plug—the temporary structure used to stop bleeding—into a fibrin-based blood clot. This gives the clot strength, stability, and durability, preventing bleeding while the injured vessel heals.

So, what are clotting factors, and what happens when they’re activated?

Clotting factors are proteins that, when activated, contribute to haemostasis. There are 12 factors, labelled with both names and Roman numerals—they are numbered from I to XIII (factor VI is technically not a clotting factor, which is why we say there are 12 despite them being labelled I-XIII).

Four of these factors (factors II, VII, IX and X) are created by the liver from vitamin K.

All these clotting factors are activated sequentially in the body down one of two pathways: the intrinsic or extrinsic pathways.

What is intrinsic coagulation?

The intrinsic coagulation pathway is activated when the body detects damage inside a blood vessel. Factors XII, XI, IX, and VIII are activated in a cascade, with each factor activating the next.

How does this differ from extrinsic coagulation?

Unlike intrinsic coagulation, the extrinsic pathway is activated when substances outside of the blood vessel detect haemorrhage. Factor III, AKA tissue factor, kicks off this process, in turn activating factor VII. This is important to note for some of our acquired coagulopathies, like anticoagulant rodenticide toxicity, which we’ll talk more about in the next episode.

Ok, so those are the intrinsic and extrinsic pathways. What’s next?

Those pathways merge and meet to form the common coagulation pathway. Here, several other clotting factors are activated, the last one being factor I or fibrinogen. Fibrinogen is converted to fibrin, at which point the cascade is complete and a stabilised fibrin blood clot results.

What happens when coagulation goes wrong?

Coagulopathies or coagulation disorders can be seen due to congenital clotting factor abnormalities or acquired clotting disorders.

Congenital Coagulopathies

Patients with congenital coagulation disorders are either born deficient in or with dysfunctional clotting factors. In most cases, we see an inherited deficiency of a single clotting factor. There are lots of different inherited coagulopathies we can see, including:

  • Factor VII deficiency, which has been reported in various breeds, including Beagles, Alaskan Malamutes, English Bulldogs, Miniature Schnauzers and Boxers

  • Factor X deficiency, which has been rarely reported in Cocker Spaniels

  • Factor XI deficiency, which has been reported in Kerry Blue Terriers, amongst other breeds,

  • And Factor XII deficiency, which has been reported in cats, as well as poodle and pointer breeds.

These disorders cause varying degrees of bleeding, from no clinically significant haemorrhage with factor XII deficiency to severe bleeding with factor X deficiency.

The two most common inherited coagulopathies are Haemophilia A and Haemophilia B, which we’ll focus on in detail for the rest of this episode.

Let’s start with Haemophilia A

Haemophilia A is the most common inherited coagulopathy in dogs and cats. In most cases, females are asymptomatic carriers and males are clinically affected.

These patients are deficient in factor VIII. In affected animals, we see prolonged bleeding early in life - from the umbilical vessels after birth, after deciduous tooth loss, and following vaccination or microchip implantation, for example.

Severely affected patients (with less than 5% of normal factor VIII level) can have spontaneous bleeding. These patients will often bleed into body cavities, spontaneously form haematomas and bleed into the joints, causing haemarthrosis.

Patients with 5-10% of normal factor VIII levels will typically not bleed spontaneously but will have prolonged bleeding from injury or surgery.

What about Haemophilia B?

As the name suggests, Haemophilia B is very similar to haemophilia A. The main difference is that these patients are deficient in factor IX - the previous factor on the intrinsic pathway - rather than factor VIII.

The disease has been reported in various dog breeds, including Labradors and mixed breeds, as well as Himalayan, Siamese, and British shorthaired cats.

The clinical signs are similar to those of haemophilia A. Usually, these patients bleed into the thoracic or abdominal cavity. However, bleeding into the CNS or between muscles is also reported. Bleeding is normally delayed-onset in these patients, compared with haemophilia A - with signs seen after around 3-4 days.

How do we diagnose our coagulopathy patients?

The first step in establishing a diagnosis in a bleeding patient is to determine whether this is a coagulopathy or thrombocytopenia and then which clotting factors are affected.

Veterinary nurses and technicians are instrumental in assisting with this process, collecting samples, and running tests. Tests commonly performed include full haematology, blood smear examination, and coagulation times, at minimum, and then individual clotting factor levels as needed.

Let’s talk coagulation testing

We perform two main tests in bleeding patients:

  • Activated partial thromboplastin time (APTT), which tells us about the factors on the intrinsic and common pathways,

  • Prothrombin time (PT), which tells us about the factors on the extrinsic and common pathways.

Activated clotting time (ACT) can also be measured, though this has largely been replaced with APTT and PT.

Depending on which is elevated (APTT, PT or both), we can then perform individual clotting factor testing at an external lab, as needed.

Patients with haemophilia A and B have prolonged APTT and ACT since both factors are on the intrinsic coagulation pathway. Based on this result, levels of Factor VIII and Factor IX are measured to determine which type of haemophilia the patient has.

Clinically affected haemophilia A patients have very low factor VIII levels (below 10% of normal). Carriers usually have levels around 40-60% of normal and normal APPT/ACT.

Patients with haemophilia B are generally less severely affected, with factor IX levels around 30-40% of normal.

So that’s diagnosis, but what about treatment?

Like other bleeding disorders, any patient with clinically significant bleeding, anaemia or transfusion dependence needs to be stabilised as a priority.

These patients will beed whole blood (ideally fresh if possible) or packed red blood cells to restore circulatory support and oxygen delivery to cells and tissues. Signs of transfusion-dependence include:

  • Tachycardia with bounding pulses

  • Bradycardia with weak pulses

  • Pale MMs

  • Prolonged CRT

  • Tachypnoea

  • Hypotension

  • Dull mentation

  • Hyperlactataemia on bloods

Aside from this, we need to replenish the patient’s deficient clotting factor to stop ongoing haemorrhage - and we’ll do this by administering plasma.

Which plasma products do we use?

There are three main options when it comes to administering plasma:

  • Fresh frozen plasma (FFP), which reliably contains all clotting factors and is stable for up to a year in the freezer

  • Frozen (aka stored) plasma (FP), which reliably contains all clotting factors except factor VIII and von Willebrand’s factor

  • Cryoprecipitate, an ultra-concentrated plasma fraction which contains high levels of factor VIII and von Willebrand’s factor

This is important to note because we can already see that one of these 3 products may not work as well for a haemophilia A patient and one of them won’t work for a haemophilia B patient.

If you don’t know which coagulopathy your patient has, the safest thing to do is to give them fresh frozen plasma, as we know this will cover them regardless of the clotting factor they’re deficient in. Once you know which specific coagulopathy they have, you can then make tailored choices about which plasma products to give in the future. If they have haemophilia B, frozen plasma is fine. If they have haemophilia A, either give them FFP or cryoprecipitate.

What else can we do?

As this is an inherited condition, like von Willebrand’s disease in our last episode, we can’t reverse it—only treat its consequences. 

This means careful surgical planning (using pre-procedure plasma transfusions, for example), monitoring patients closely for signs of bleeding, and educating clients on managing a patient with the disease. Clients need to avoid injuries or wounds as much as possible, have a first-aid kit on hand in the event of injury, and communicate clearly with any vets they see about their pet’s condition. A collar tag identifying them as a haemophiliac is also useful.

In the clinic, we need to avoid bleeding as much as possible - avoiding the jugular for sampling and minimising any self-trauma in the hospital. This might mean preventing patient interference or providing anxiolytics to a nervous patient so they don’t tear a claw or rub their nose on the kennel door, for example.

With careful management and client support, these patients can have a good quality of life - and nurses are instrumental in this process. With everything from emergency management in bleeding patients to plasma transfusions and ongoing client care, the skills we use in managing these patients are vast.

Did you enjoy this episode? If so, I’d love to hear what you think. Take a screenshot and tag me on Instagram (@vetinternalmedicinenursing) so I can give you a shout-out and share it with a colleague who’d find it helpful!

Thanks for learning with me this week, and I’ll see you next time!

References and Further Reading

Laura Jones
Previous

45 | Help, my patient has eaten rat poison! The vet nurse's guide to anticoagulant rodenticide toxicity
Next

43 | Help, my patient is bleeding! How to care for patients with von Willebrand’s Disease