bleeding SA

Haemostasis

·    Stages:

1.        Primary haemostasis = platelet plug

2.        Secondary haemostasis = fibrin plug (requires coagulation cascade)

3.        Clot lysis

Primary haemostatic disorders

Clinical signs: petechia, mucosal bleeds, multiple sites of bleeding

Investigations: haematology (platelet count), BMBT, vWF

Causes:

·    Thrombocytopenia

o  Defective platelet production – bone marrow neoplasia, drug/chemical/toxin-induced bone marrow suppression, bone marrow infection

o  Accelerated platelet removal – IMTP (most common cause), DIC

o  Platelet loss – splenomegaly, acute ongoing haemorrhage

·    Thrombocytopathia – treat symptomatically

o  Inherited thrombopathias

o  Drug-induced defects of platelet function, e.g. NSAIDs

o  Platelet dysplasia, e.g. neoplasia

·    vWF dysfunction

o  Dobermans predisposed

o  Diagnosis: normal platelet count, prolonged BMBT, low vWF antigens

o  Treatment: plasma transfusion, cryoprecipitate, desmopressin (for type 1)

Secondary haemostatic disorders

Clinical signs: deep bleeds, single site, haematomas, mucosal bleeds

Investigations: WBCT, OSPT, APTT, specific factor assays

Causes:

·    Congenital

o  Haemophilia – either factor 8 or factor 9 deficient – will have increased APTT

·    Acquired

o  Vitamin K antagonism (rat bait) – stops production of factors 2, 7, 9, 10 (takes few days so don’t see CS for few days)

§ If can make vomit on same day then risk of side effects is very low

o  Hepatic disease – all clotting factors made in liver – incr. OSPT and APTT

Approach to bleeding patient

Signalment –

Clinical signs:

·    Primary coagulopathy

o  Petechiae/ecchymoses – little bleeds common (differentiate from vasodilation – push microscope slide into lesion – if doesn’t fade = petechiae)

o  Bleeding from MMs

o  Usually >1 site of bleeding

·    Secondary coagulopathy

o  Deep or cavity bleeds (little bleeds not seen)

o  Haematomas common

o  Sometimes only 1 site of bleeding

Investigations:

·    Haematology – platelet count – normal = rule out IMTP

o  Take blood sample from peripheral vein (cephalic) – easier to apply pressure bandage

·    Buccal mucosal bleeding time (conscious dog, small nick, hold gum up and see how long takes to stop bleeding) – increased = primary coagulopathy

·    vWF antigen measurement – normal = rule out vWF

·    Whole blood clotting time – increased = thrombocytopenia, vit K antagonism

o  Measures intrinsic + extrinsic pathways (also incr. if low platelets)

·    One stage prothrombin time – increased = hepatic disease, vit K antagonism

o  Measures extrinsic + common pathways

·    Activated partial thromboplastin time – increased = hepatic disease, vit K antagonism, haemophilia

o  Measures intrinsic + common pathways

Management:

·    Avoid SC injections, DON’T use IM injections

·    Minimise movement, cage rest

·    Handle very gently (bruises easily)

Thrombosis

·    Causes hypoxia and tissue damage (but hard to detect)

·    To test fibrinolysis – test fibrinogen, FDP (degradation products), D-dimer (breakdown products)

o  D-dimer increased when more thrombin activated (animal in pro-thrombotic state) = DIC, feline thromboembolism disease, PLN, cushings

DIC

·    Disseminated intravascular coagulation – balance of haemostasis tips (animal turns prothrombotic or wont form any clots)

·    Always an underlying causes – potential triggers:

o  Endothelial damage

o  Platelet activation, e.g. FIP, endotoxemia

o  Release of tissue procoagulants – trauma, pancreatitis, bacterial infections, neoplasia

o  Specific groups of diseases known to cause DIC:

§ Infectious agents – bacterial sepsis, FIP, babesia, rickets

§ Neoplasia – metastatic tumours, haemangiosarcoma

§ Inflammation/necrosis – trauma, IMHA, pancreatitis, hepatitis, GDV, vasculitis

§ IV haemolysis – IMHA, acute transfusion reactions, snake/insect bites

·    Two types:

o  Overt DIC – body able to compensate for a bit, may see few clinical signs as small clots thrown (but no clinically detectable abnormalities)

o  Overt DIC – body can no longer compensate, lots of clots thrown (cats), bleeding (dogs) ® haemorrhage and end-organ damage

·    Diagnosis:

o  Thrombocytopenia

o  Hypofibrinogenemia (as coagulation factors used up)

o  Schistocytes

·    Treatment: treat underlying cause