Puppies have a particular knack for seeing the inherent chew toy potential in a wide range of household objects, such as sneakers and chair legs. Similarly, we have a theory that urgent and emergency veterinary medicine professionals are unparalleled at seeing the potential patient risks associated with seemingly harmless activities — especially during the summer. A kind of woes-colored glasses, so to speak.
- A fun family campout in the woods? You mean where venomous snakes live?
- A sunny summer jog through the neighborhood? Sounds like a recipe for hyperthermia.
- A cross-country road trip adventure? Better make sure your Airbnb host doesn’t use rodenticide.
- A relaxing backyard barbecue? Not if that chicken bone becomes lodged in your pet’s esophagus.
When summertime emergencies arrive (and arrive, they will), having the right diagnostic tools on hand can make all the difference when time is of the essence. One such tool – the handheld Element COAG+® Veterinary Analyzer – can be critical to diagnosing and/or treating the patients in the examples above with speed and accuracy.
COAGULATION: A QUICK REFRESHER
Coagulation is part of a larger process known as hemostasis. The hemostatic system is responsible for maintaining blood in a fluid state while in the vessels, arresting bleeding at the site of injury, and removing the clot once healing is complete. Hemostasis can be further divided into two categories, primary and secondary hemostasis, but don’t let their misleading monikers fool you. The two occur simultaneously and depend on each other for success.
Primary hemostasis describes the body’s initial response to vascular injury. “The process involves the interaction of endothelial cells lining the injured blood vessel, circulating coagulation factors, and platelets that form a plug in the region of the damaged endothelium,” explains Antech Pathologist Terry G. Taylor, DVM, MPH, DACVP, MRCVS.
Secondary hemostasis involves coagulation, or the formation of fibrin via the coagulation cascade, and concurrent fibrinolysis, which prevents the blood clot from growing too large. The coagulation cascade is divided into three distinct pathways: intrinsic, extrinsic, and common. “Coagulation factors are activated in a specific sequence,” says Terry. “They follow two different pathways (either intrinsic or extrinsic) and a final common pathway which results in the formation of the end product, fibrin.”
PRIMARY AND SECONDARY HEMOSTASIS DISORDERS
The hemostatic system needs an adequate number of functional platelets, as well as an adequate concentration and activity of coagulation factors, to function properly. Without these two components, life-threatening problems arise.
Primary hemostasis disorders are the result of platelet plug formation failure due to quantitative (thrombocytopenia) or qualitative (thrombocytopathia) platelet problems, or due to a deficiency of von Willebrand factor. Thrombocytopenia can be caused by things like venomous snake bites, tick-borne disease, and neoplasia. Thrombocytopathia, on the other hand, can be inherited or acquired (e.g., drug reactions).
Secondary hemostasis disorders are the result of fibrin clot formation failure due to a deficiency of one or more coagulation factors. Coagulation factors are predominantly made in the liver, and several factors (II, VII, IX, X) require carboxylation (a process dependent on vitamin K) to function. Thus, both liver and vitamin K issues can interfere with secondary hemostasis.
Returning to our previous list of emergencies, snakebites, heat stroke, and anticoagulant rodenticide toxicity fall into the category of secondary hemostasis disorders.
Venomous snakebite
Technically, snakebites are often such complex coagulopathies that they encompass both primary and secondary hemostasis. That’s because snake venoms are made of biologically active proteins and peptides that can either activate or inhibit both platelets (primary) and coagulation factors (secondary). In fact, for almost every coagulation factor involved in coagulation and fibrinolysis, there’s a venom protein that can affect its function.
Heat stroke
Hemostatic function relies on body temperature maintenance. Nonpyrogenic hyperthermia, which includes heat stroke, causes direct cytotoxicity at high enough body temperatures. This direct cytotoxicity results in endothelial damage that releases thromboplastin and factor XII, activating the coagulation cascade. In severe cases, disseminated intravascular coagulation (DIC), which involves both inappropriate clotting and bleeding, may develop. Though rare, this life-threatening condition is more common in dogs.
Anticoagulant rodenticide toxicity
Rodenticide is unfortunately widely used and highly palatable to dogs. And though feline poisonings are less common, they may become ill by consuming poisoned rodents. Anticoagulant rodenticides (e.g., brodifacoum, bromadiolone, difenacoum, difethialone, warfarin) antagonize vitamin K, which interferes with carboxylation, which keeps factors II, VII, IX, and X from functioning.
COAGULATION TESTING
Terry explains that in the laboratory, coagulation factor activity within the coagulation cascade pathways is measured separately and can thus help determine the area along the coagulation cascade that is affected. Prothrombin time (PT) and activated partial thromboplastin time (aPTT) are the most used coagulation tests. The Element COAG+ covers both PT and aPTT in dogs and cats in-clinic and in minutes using a single fresh blood or citrated whole blood sample.
PT evaluates the extrinsic and common pathways, and the coagulation factors that can be evaluated include I, II, V, VII and X. The activated partial thromboplastin time (aPTT) evaluates both intrinsic and common pathways, covering all factors except VII. “Therefore,” Terry explains, “if aPTT is normal and PT is abnormal, the problem can be localized to factor VII.”
Because factor VII has a short plasma half-life, Terry notes that a prolonged PT may be the first indication of anticoagulant rodenticide poisoning. And patients with prolonged PT and aPTT indicate the presence of multiple coagulation system pathway disruptions and are associated with a variety of disease states, including DIC.
It’s worth adding that despite the widespread utility of both PT and aPTT, they don’t cover everything. As with any test, the results may be an impetus for further testing to reach a definitive diagnosis. For example, given the complexity associated with snakebites, if the patient receives a normal result, it’s recommended to submit a sample for in-depth reference lab testing.
ELEMENT COAG+
The Element COAG+ provides on-the-spot evaluation of secondary hemostatic function via PT and aPTT in dogs and cats. In-clinic testing ensures rapid diagnosis and treatment of summertime emergencies, as well as crucial pre-surgical screening data if that backyard barbecue results in emergency surgery. In such cases, having the right diagnostics at the right time can make the difference between life and death.
Discover fast, flexible coagulation testing
The portable, handheld Element COAG+ allows you to run PT and aPTT when and where it’s needed, whether the patient is in the treatment room, the operating room, or a cage. A single test strip provides you with critical results in minutes.
