Approach to the bleeding patient Flashcards
In ml/Kg what is the total blood volume of:
- dogs
- cats
80/90ml/Kg
60-70ml/Kg
When there is blood loss which 3 life threatening situations need to be considered?
- Hypovolaemic shock
- Severe anaemia
- Brain or pulmonary haemorrhage
In a patient, what samples would you want to collect?
- Blood smear
- Full blood count (EDTA)
- Coagulation profile (Citrate)
- Biochemistry (heparinised plasma)
What are the steps when approaching a bleeding pateint?
- Attempt to quantify blood loss
- Identify life threatening situations
- Establish venous access and take samples
- Control haemorrhage
- Fluid replacement
What fluids should be given if a patient is hypovolaemic?
Crystalloids
“Shock rates”: recommend a bolus of fluids of?
1/4 of the animals normal blood volume
What are the 5 stages of haemostasis?
- Vessel injury
- Vascular contraction
- Primary haemostasis
- Secondary haemostasis
- Tertiary haemostasis
Describe primary haemostasis
Formation of the primary plug:
- Von Willebrand factor attached to the walls of vessels interacts with platelets and allows them to bind to each other and the vessel wall
What does secondary haemostasis involve?
Coagulation cascade resulting in the generation of thrombin
Compare when primary vs primary and secondary haemostasis is needed
- Small defect: platelet only (primary haemostasis)
- Large defect: requires platelets and stabilisation of the clot by cross-linked fibrin (secondary haemostasis)
What does tertiary haemostasis involve?
Fibrinolysis - plasmin
What are the clinical signs of secondary haemostasis defects?
- Deficiency in clotting factors
- Present more acutely with life-threatening blood loss
- subcutaneous or cavity bleeding e.g. haemothorax
- haematoma formation
Which vessel must you not sample from if a bleeding disorder is suspected and why?
Jugular vein
- it will be very hard to stop the bleeding and a pressure bandage cant be used on the neck
Which in house labs tests are used to differentiate 1 vs 2 coagulopathy
Primary coagulopathy (test of platelet function or number)
- Manual platelet count
- Buccal Mucosal Bleeding Time
- Von Willebrand factor
Test of Coagulation
- Prothrombin Time (PT)
- Activated Partial Thromboplastin Time (APTT)
In which situation should you use a buccal mucosal bleeding time test?
Should only be performed in a situation of a normal platelet count & normal clotting (PT/APTT) times – assessing platelet function
Give examples of disorders of primary haemostasis
- Thrombocytopenia
- Inherited thrombocytopenia
- Immune mediated thrombocytopenia
- Platelet dysfunction
- Von Willebrand disease
What is thrombocytopenia?
a condition in which you have a low blood platelet count
What are the causes of a thrombocytopenia?
- Lack of platelet production
- Increased platelet consumption
- Increased platelet destruction
- Splenic torsion
What can cause a lack of production of platelets?
- Bone marrow disorder
- Drug toxicosis
What can cause an increase in platelet consumption?
- Disseminated Intravascular Coagulation
- Acute severe haemorrhage
What causes a primary immune mediated thrombocytopenia?
IgG binding to platelets, resulting in their destruction
What causes a secondary immune mediated thrombocytopenia?
Secondary to drugs, infectious disease or neoplasia
- 5-7d of exposure of drug required to produce sensitisation and onset of thrombocytopenia
How would you treat an Immune Mediated Thrombocytopaenia?
If 1° treat with glucocorticoids, eg Prednisolone or Dexamethasone.
If 2° treat underlying disease of discontinue drug
What is the name given to decreased platelet function?
Thrombocytopathia
Which test is used to assess platelet function?
Buccal mucosal bleeding time
Describe Von Willebrand disease
Deficiency of von Willebrand factor
How is von Willebrand factor normally synthesised, stored and used?
By endothelial cells
- vital for platelet adherence
- Binds to factor VIII and prolongs its half life
Which situation should prompt evaluation of von Willebrand factor?
Mucosal surface bleeding or excessive bleeding following surgery or trauma in a dog with a normal platelet count, prothrombin time (PT), and activated partial thromboplastin time (aPTT)
Disorders of secondary haemostasis are inherited or quired disorders of …?
Clotting factors
Give examples of acquired secondary disorders of haemostasis
- vitamin K deficiency
- liver disease
- DIC
Vitamin K deficiency is most commonly caused by?
Ingestion of vitamin K antagonist rodenticides
Vitamin K is involved in the production/activation of which clotting factors?
II
VII
IX
X
What are the clinical signs of a vitamin K deficiency?
- observed 2-5 days after ingestion
- epistaxis, melaena (black stool), haemoptysis, haematoma, ecchymoses, haematuria, gingival bleeding, haemoabdomen, haemothorax
Which breeds are pre-disposed to von Willebrand disease?
Doberman pinschers
What is haemophilia A?
What is haemophilia B?
Deficiency of factor VIII
Deficiency of factor IX
Disseminated Intravascular Coagulation (DIC) is related to which part of haemostasis?
Tertiary haemostasis - problems with the breakdown of the clot
How does DIC first present?
As a thromboembolic disease so there are clots everywhere
How does DIC progress leading to organ failure?
Bleeding begins as clotting factors are exhausted
- widespread activation of coagulation and thrombosis
- microthrombi in organs
- ischaemia and necrosis
What are some of the underlying causes of DIC?
- infectious disease
- immune mediated disease
- neoplasia
- trauma
- heat stroke
- cardiac disease
What lab abnormalities are seen with acute DIC?
- prolonged clotting times
- thrombocytopenia (low platelet blood count)
- decreased fibrinogen
When are fibrin degradation products formed?
During degradation of both fibrin (fibrinolysis) and fibrinogen (fibrinogenolysis)
When are fibrin degradation elevated?
- DIC
- Thrombotic disease
What are D-dimers specific for?
Breakdown of cross linked fibrin
