Trauma-induced coagulopathy in dogs

8 August 2023

 

Rachael Birkbeck and collaborators Dan Chan, Duana McBride and Stefano Cortellini from the Department of Clinical Science and Services, Royal Veterinary College were awarded PetSavers’ funding in 2017 to study trauma-induced coagulopathy in dogs.

Severe trauma is associated with derangements of coagulation status. Acute traumatic coagulopathy (ATC) is a coagulopathy that occurs in the immediate minutes following trauma prior to or independently of resuscitation e­ orts. It is a coagulopathy that is attributed primarily to the e­ffects of tissue damage, hypoperfusion and haemorrhage. Hypocoagulability and hyperfibrinolysis are the hallmarks of ATC, which is reported to occur in up to 25% of severely traumatized people, and its presence is associated with a 4-fold increased risk of mortality and massive transfusion requirement. Platelet hypofunction has also been shown to contribute to ATC in people and has been associated with a 10-fold increase in mortality despite normal platelet count. Resuscitation-associated coagulopathy occurs secondary to haemodilution with large fluid volumes, the administration of synthetic colloids, massive transfusion and prolonged surgery which contribute to the development of acidaemia and hypothermia.

Trauma-induced coagulopathy (TIC) is a term used to describe the spectrum of coagulation changes which occur following severe traumatic injury due to endogenous ATC and resuscitation attempts. There are multiple phenotypes of TIC, which may result in hypocoagulability or hypercoagulability and/or hypofibrinolysis or hyperfirinolysis. The clinical manifestation is influenced primarily by the degree of change in thrombin production, platelet function and fibrinolysis which ultimately depend on the degree of trauma. The accumulation of catecholamines and metabolites post-injury, the extent of endothelial activation and the host immune response also a­ffect the phenotype of TIC.

In dogs, it is unclear how significant the impact of fibrinolytic or platelet dysfunction is on coagulation derangements following trauma, although a recent study1 using rotational thromboelastometry in dogs with trauma demonstrated that hyperfibrinolysis occurred in 9% of patients on admission. The current shared hypothesis is that hyperfibrinolysis might occur in patients with severe trauma, although more studies are required to corroborate this theory and to provide a solid ground for decision-making processes in the treatment of trauma in dogs.

 

What will be the benefits of this research?

Trauma is a leading cause for admission in small animal veterinary hospitals and is associated with significant morbidity and mortality. Intracavity bleeding is reported in up to 38% of veterinary trauma patients. Furthermore, up to 36% of dogs may require a packed red blood cell transfusion following severe trauma. Haemostatic derangements are reported in cats and dogs following trauma; however, a consensus defining features of TIC and ATC in veterinary species has not been reached. Haemorrhage is a potentially reversible cause of death; therefore, it is possible that refinement of resuscitation strategies and therapeutic interventions (e.g. use of tranexamic acid) to target haemorrhage secondary to TIC and ATC in cats and dogs could improve survival outcomes.

 

What are the aims of this research?

The aims of this study were to assess platelet function via whole blood electrical impedance platelet aggregometry induced by the action of specific platelet activators arachidonic acid, adenosine diphosphate and collagen, and to assess the degree of fibrinolysis using citrated whole blood kaolin-activated thromboelastography with a tissue plasminogen activator (tPa) challenge in dogs following trauma. We hypothesized that dogs with severe traumatic injury and evidence of hypoperfusion would have decreased platelet aggregation and hyperfibrinolysis. We also hypothesized that higher degrees of traumatic injury, as assessed by the Animal Trauma Triage score and markers of hypoperfusion, would be associated with greater platelet dysfunction and fibrinolysis.

 

What have we learned so far?

Data collection and analysis is now complete and our manuscript has been accepted by the Journal of Veterinary Emergency and Critical Care. This study was a residency project and gave me the opportunity to develop my understanding of coagulation from clot formation to dissolution, and the e­ffects of severe traumatic injury at a vascular level. Without financial support from BSAVA PetSavers this project would not have been possible. Personally, I have learnt so much from this project and look forward to sharing this knowledge and our findings with my colleagues in primary-care practice who are on the frontline providing trauma care.

 

Challenges of the project

Our study had several challenges, the most impactful being the fact that it was conducted within a referral setting, although first-opinion cases are also seen out of hours through the emergency service. Currently, the availability of viscoelastic techniques and platelet function analysers is limited to referral hospitals in the UK; however, most trauma patients present to their primary care vet first and are typically stabilized prior to referral. Although it is essential that every e­ ort is made to ensure trauma patients are stable before being transported, this did result in a delay from the time of trauma to presentation at our hospital. Given that the aim of our study was to assess acute changes to coagulation in dogs following trauma, the fact that our trauma population was comprised predominantly of referral cases meant that it was challenging to capture data within 24 hours of trauma when coagulation derangement consistent with ATC is likely to occur.

With the advent of point-of-care viscoelastic techniques, the global assessment of coagulation in primary-care practice is now possible. I would encourage future studies to consider collaborations between academic institutions and primary-care practices; this will ensure that our primary-care patient population is represented in research.

Another obstacle we had to overcome was ensuring that to maintain consistency, two of the authors (RB, SC) were available 24/7/365 to sample blood from patients following admission and study enrolment then run the coagulation tests within 90 minutes of obtaining samples. The nature of emergency work often resulted in late night calls from our emergency room and some unsociable hours in the laboratory. Despite these challenges, a morale-boosting positive of this project was that it shone a light on the exceptional care our ECC team and supporting services deliver to dogs with severe traumatic injury. We also got to spend time with our lovely blood donor dogs who were the control population for this study.

 

Thinking about applying for BSAVA PetSavers’ funding?

Funding from organizations such as BSAVA PetSavers has the potential to make research opportunities available to everyone and not just those working in academic institutions. I would advise anyone with an interest in research to consider applying for a BSAVA PetSavers grant to fund their project.

 

About the Author

Rachael Birkbeck graduated from St George’s University, West Indies in 2011, then completed a Feline Medicine Internship at Edinburgh University and a rotating Internship at Pride Veterinary Centre. After spending several years working out of hours for Vets Now, she began a residency in Emergency and Critical Care at the Royal Veterinary College in July 2017. In August 2020, she sat the board exam to join the American College of Emergency and Critical Care and then started work in private referral practice as a specialist in ECC. In October 2021, she joined The Ralph Veterinary Referral Centre in a role that provides a combination of clinical work, teaching responsibilities and research opportunities – plus a good work/life balance!

She enjoys all clinical work and research; however, the aspect of her job that she loves the most is helping others to succeed in their chosen career path. Often career development requires research experience and the funding provided by PetSavers removes the financial barrier that can make project costs prohibitive. Rachael is particularly keen to ensure research opportunities are available to both vets and veterinary nurses outside of a university teaching hospital setting.