Clinical Pathology- Haematology: Approach to Bleeding Patient and Transfusion Medicine Flashcards
If a patient arrives and is bleeding how should you approach the animal?
Attempt to quantify blood loss
Identify life threatening situation- hypovolaemic shock, severe anaemia, brain or pulmonary haem
Establish venous access and collect samples for test
How can the patient be stablilised?
Control of haemorrhage- pressure
Fluid replacement:
Volume replacement crystalloid if hypovolaemic
‘shock rates’ recomend a bolue of 1/5-1/4 animals blood volume
Blood transfusion if significant anaemia
Briefly describe the process of haemostasis?
Vessel injury
Vascular contraction- primary plug
Primary haemostasis- endothelium, platelets, von willebrand
Secondary haemostasis- coagulation cascade resulting in generation of thrombin
Tertiary haemostasis- fibrinolysis- plasmin
What is needed for primary haemostasis?
von Willebrand factor
platelets
What are clinical signs of primary haemostasis defects?
‘Small holes’
due to lack of platelets/poor platelet function
What are clinical signs of secondary haemostasis defects?
Result of deficiency in clotting factors
Tend to present more acutely with life-threatening blood loss
Subcutaneous or cavity bleeding
Haematoma formation
Pulmonary haemorrhage
Haemarthrosis
‘Large holes’
What in house tests can be used to test for primary and secondary haemostasis disorders?
Haematology- smear examination and platelet estimation
Biochemistry
Whole blood clotting time- uncommon
Activated clotting time- uncommon
Buccal mucosal bleeding time
Where should thepatient be venepunctured if worried aboiut haemostasis disorders?
Cephalic/Saphenous vein
What tests can be used to differentiate between primary and secondary haemostasis disorders?
Primary coagulopathy- test platelet function or number:
manual count, buccal mucosal bleeding time, von Willebrand factor
Test of coagulation:
Prothrombin time
Activated partial thromboplastin time
Activated clotting time- rarely used
Test specific factor levels
Test of fibrinolysis- fibrinogen degredation products, D-dimers
How much blood can healthy animals usually lose?
15-25% of blood
What disorders of primary haemostasis are there?
Thrombocytopenia
von Willebrands disease
Thrombocytopathia- v rare
Vascular disorders- v rare
What can cause thrombocytopenia?
Most common cause
Lack of production- bone marrow disorders, drug toxicosis
Increased consumption- DIC, acute severe haemorrhage
Increased destruction- immune mediated- primary/secondary
Increased sequestration- splenic torsion
What are the two types of inherited thrombocytopenia?
Inherited macrothrombocytopaenia- CKCS, norfolk and cairn terriers
Breed-associated thrombocytopenia- Sighthounds with lower platlet counts
What is the difference between primary and secondary immune mediated thrombocytopenia?
Primary- IgG binding to platlets resulting in their destruction, marked thrombocytopenia
Secondary- secondary to drugs, infectious disease or neoplasia, antibiotics most common
How is IMTP diagnosed?
Full clinical history- including drugs and travel history
Full clinical exam including opthalmological exam
Haematology with blood smear evalutation
Biochemistry +/- urinalysis
Thoracic radiographs
Abdominal ultrasound
Idexx 4DX SNAP
How is IMTP treated?
Secondary- treat underlying disease or discontinue offending drug
Glucocorticoids mainstay of therapy for primary disease:
regulator of gene expression, effects humoral and cell-mediated immune system
Whole blood transfusions can provide short-term haemostasis despite a negligible increase in platelet count post-transfusion
What is platlet dysfunction and what can cause it?
Animals who bleed excessively despite normal platelet count and coagulation profile
Causes:
Drug therapy
von Willebrands disease
Hepatic disease
Renal disease
Hyperproteinaemias
Bone marrow neoplasia
What is von Willebrands disease?
Deficiency of von Willebrand factor- inherited, acquired with severe aortic stenosis
vWF is synthesised and stored by endothelial cells- vital for platelet adherence
Mucosal surface bleeding or excessive bleeding following surgery
How is von Willebrands disease treated?
Cryoprecipitate- rich in VII, fibrinogen and vWF, whole blood or fresh plasma
DDAVP- 1-desamino-8-D-arginine vasopressin increases vWF release
What causes disorders of secondary haemostasis?
Deficiency of clotting factors
Inherited uncommon- haemophilia A/B
Usually acquired- vitamin K antagonism (deficency), severe liver disease, DIC
What can cause vitamin K deficiency?
Most commonly caused by ingestion of vitamin K antagonists- rodenticides
Other causes- hepatic failure, decreased absorption
Vit K involved in production/activation of factors II, VII, IX, X