Page 81 - ONLINE PROCEEDING BOOK WSAVA 2017
P. 81

WSVA7-0342
EMERGENCY/CRITICAL CARE (VECCS)
THE BLEEDING PATIENT: DIAGNOSIS AND TREATMENT APPROACH
D. McBride1
1Royal Veterinary College, Queen Mother Hospital for Animals, London, United Kingdom
THE BLEEDING PATIENT: DIAGNOSIS AND TREATMENT APPROACH
Duana McBride BVSc DACVECC MVMedSc MRCVS
Royal Veterinary College, Hawkshead Lane, North Mymms, United Kingdom
dmcbride@rvc.ac.uk
Physiology
The haemostatic system can be broken down into 3 main components: 1) Primary haemostasis; 2) Secondary haemostasis; and 3) Fibrinolysis. All 3 systems are occurring as a continuum, and there are continued advances in the understanding of haemostasis, which
is described by the ‘cell based model of coagulation’. However, in this lecture, to better understand the bases of diagnostics and treatment of the bleeding patient, we will be discussing haemostasis in the traditional sense.
Primary haemostasis:
Primary haemostasis involves the interaction between platelets and the subendothelial matrix to form a temporary primary haemostatic (platelet) plug. When injury occurs to vessels (endothelium), platelets
adhere to the subendothelial matrix (collagen) via von Willebrand factor (vWF). Once platelets are adhered to the subendothelial matrix, they are activated by several different mechanisms, including collagen, adenosine diphosphate (ADP), thromboxane A2 (TXA2), thrombin, and platelet activating factor to name a few. Platelets change shape to an activated form, having an ability to aggregate together forming a platelet plug. The platelet plug forms a framework for secondary haemostasis to occur. Therefore the 3 important components to primary haemostasis are: normally functioning platelets, vWF, and the endothelium.
Secondary haemostasis:
Secondary haemostasis involves several enzymatic reactions which we commonly refer to as the intrinsic, extrinsic and common pathways, eventually forming  brin which stabilises the clot ( gure 1).
Figure 1. Secondary coagulation cascade
Important things to remember about the secondary cascade:
· All factors involved in the secondary cascade are produced by the liver
· Factors II, VII, IX, and X are vitamin K dependent · Factor VII has the shortest half-life of 4 – 6 hours Fibrinolysis:
Coagulation is a continuum of processes, and therefore requires  brinolysis to occur. Plasminogen is converted to plasmin, which is responsible for the breakdown of the  brin clot. Once the  brin clot breaks down,  brin degradation products (FDP), including D dimers, are produced. Fibrin degradation products are eventually removed by the liver.
Approach to the bleeding patient Primary haemostatic disorder: Diagnostic tests:
An Urban Experience
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Clinical Signs:
Petechial haemorrhages and ecchymosis, bleeding of mucosal surfaces
Platelet count (CBC):
Normal > 200,000/μL. Less than 40,000/μL can lead to clinical signs.
Platelet count (blood smear)
One platelet represents 15,000 – 20,000/μL
Look for clumps on the feathered edge which could falsely lower your platelet count
Buccal Mucosal Bleeding Time (BMBT)
Normal: 1.7 – 4.2 minutes (dog); 1.4 – 2.4 minutes (cat)
Procedure: Ensure normal platelet count, as thrombocytopenia will result in prolonged BMBT
Prolonged BMBT indicates thrombocytopathia or vasculopathy.
vWF:Ag
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