Disorders of haemostasis Flashcards
Discuss clinical features of disorders of haemostasis
Platelet disorders are usually manifested as acquired petechiae, purpura or mucosal bleeding and are more common in women.
Epistaxis, menorrhagia and GI bleeding are common initial symtpoms.
Describe immune thrombocytopenia
Thrombocytopenia associated with increased peripheral desturction of platelets and shortened platelet survival caused by an antiplatelet antibody is seen in a number of disease.
Following cause immune thrombocytopenia
- Collagen vascular disesase such as SLE
- Leukaemia and lymphoma
- Drugs (quinine and quinidine, heparin and clexane, digoxin, sulfonamides, phenytoin and aspirin)
- Post infectious (rubella, rubeola, and varicella)
- Post transfusions thrombocytopenia - severe thrombocytopenia occurring about 1 week after blood transfusion
Disucss HIT
HIT type 1 is a mild transient drop in platelet count that typically occurs within the first two days of heparin exposure. The platelet count typically returns to normal with continued heparin administration and appears to be a direct effect of heparin on platelets.
HIT type 2 is a clinically signifaicnt syndrome due to antibodies to platelet factor 4 complexed to heparin. THese antibodies can cause thrombosis along with thrombocytopenia
Discuss clinical features of HIT
Timing
1) typical - occurs 5-10 days after the initiation of heparin. Heparin dependant antibodies usually develop between five and 8 days after heparin exposure.
- Early onset HIT may be seen wihtin the first 24 hours fi the patient has been exposed to heparin in the previous one to three months and has circulating HIT antibodies.
2) delayed onset HIT following withdrawal of heparin
Features
1) Thrombocytopenia is the most common manifestation. The mean nadir count is approxiamtly 60.
2) Bleeding is uncommon but has been reported in unusual sites.
3) Thrombosis occurs in up to 50% of individuals with venous thormbus more common than arterial.
- skin necrosis at the site of heparin injections should immediatley suggest HIT
- Limb gangrene more commonly associagted with venous rather than arteiral
- Organ ischaemia or infarct
Discuss evaluation of HIT
Should be suspected in any one with the following who has recieved heparin in the preceeding 5-10 days
1) new onset thrombocytopenia
2) a decrease in platelet count by 50 percent or more even if the platlet count is above 150
3) venous or arterial thrombosis
4) Necrotic skin lesions at heparin injection sites
5) acute systemic reaction occurring after IV heparin admin
4 ts score Thrombocytopenia Timing Thrombosis or other sequelae other cuase for thrombocytopenia present
Score
0-3 low
4-5 intermediate
6-8 high probability
Discuss ix of HIT
CLinical with the four t score and antibody testing
Discuss management of HIT
Stop heparin
Consider dialysis
Start fondaparinux, DOAC or danaporoid for bridging for warfarin
Describe idiopathic thrombocytopenic purpura
Autoimmune ITP is considered after other causes have been excluded. It is asscoiated with an IgG antiplatelet antibody
Acute
- seen most commonly in children 2-6 years old.
- a viral prodrom commonly occurs within 3 weeks of its onset
- platelet count decreases usually to less than 20
- self limiting with greater than 90% rare of spont remission.
- steroids and IVIG are reserved for those with active beeding
Chronic
- Adults - women more commonly then men
- Onset is insidious wihtout prodrome
- manifested by easy bruising, prlonged menses, and mucosal bleeding.
- petichaie and purpura are common
- splenomegaly is unusual in either chronic or acute
Non immune thrombocytopenia
Non immune platelet destruction is usually consumptive or mechanical
Consumptive
- occur as part of the process of intervascular coagulation although it may be seen at sites of significant endothelial loss.
- TTP, HUS and vasculitis all intitiate platelet destruction through endothelial damage,
Describe thrombotic thrombocytopenic purpura
Pathological state of TTP is the result of subendothelial and intraluminal deposits of fibrin and platelet aggregates in capillaries and arterioles.
THe disease affects patients of any age or sex but the majority of patients are 10-40 years of age.
Can be idiopathic or may be asscoiated with pregnancy. epidemics of verotoxin producing e.coli and shigella, malignancy, chemo, marrow transplant and drug dependent ABs
Classic pentad
- Thrombocytopenic purpura - generalized purpura and bleeding complaints are common
- microangioathic haemolytic anaemia
- fluctuating neurological symptoms - stroke, seizures, parethesias, alOC and coma all of which fluctuate
- renal disease
- fever
Treatment with plasma exchange has dramatically ifnluenced outcomes. Mortality has fallen more than 90% to less than 20% with treatment
Discuss haemophilia A
Factor 8 variant that is present in normal levels but lacks a clot promoting property
Haemophilia A can be corrected by liver transplant
Cases with 1% activity are severe and may ahve spont bleeding, those with 1-5% are moderate and spont bleeding is rare, 5-10% and above are considered mild with little risk for spont bleeding but still with hazards with trauma and surgery.
Bleeding may occur anyway, recurrent haemarthrosis and joint destruction are a major cause of morbidity. Intracranial bleeding is a major cause of death in all groups
Discuss management of haemophilia A
Prepation
- ED management of haemophilia is best accomplished with advanced planning that includes protocols developed with haemotolgoist for the administration of Factor
- Infomration surrounding - primary physician, haematologist, factor 8 activity level, blood type presence of antihaemophilic factor antibodies and last time of hospitilatioazn
-Desmopressin acetate (DDAVP) has been shown to increase levels of factor 8 in patients with haemophilia A and in some with vWD - it is given IV at a dose of 0.3mic/kg - DDAVP acts be releasing vWF stored in the lining of blood vessels and mobilising factor 8 available
REPLACEMENT
MILD/MODERATE (haemoarthosis, minor trauma, epistaxis, suturing)
30IU/kg of Factor 8 concentrate for the 1st dose than 20 IU/kg at 12 hours and 24 hours post firsst dose
-DDAVP 0.3micc/kg in 100ml NaCl over 45 minutes
-If factor 9 deficiency 60IU/kg followed by 30IU 24 hours later of factor 9
MAJOR - intracerebral, GIT, hip, throat, major muscles (psoas or limb muscle bleeds with risk of compartment syndrome )
- 45 IU/KG factor 8 stat - commence continous factor 8 infusion wihtin 4 hours to maintain factor level >70%- this should be started by haemoatologist
- 90IU/kg of factor 9 with infusion by the 4 hour mark for factor level >70% started by haem
All haemophiliacs should be screened for the development of antihemophilic factor antibodies - patients who develop these antibodies more often have sever thrombophilia necessitating recurrent transfusions
Prophylaxis
- the anticipation of delayed bleeding in patients with haemophilia may necessitate lower thresholds for admission and observation.
- Deep laceration, those with soft tissue injuries where the pressure from developing haematoma may be destructive (eye, airway, spinal column), any head injury
- head injury should have factor replacement as a prophylactic
Discuss von Wille brands disease
Patient platelets are normal in number, morphology and other function but in the absence of circulating factor 8/vWF thied adhering properties are diminised
vWD is teh most common hereditary bleeding disorder
Manifestations are generally less crippling than those of haemophilia.
Bleeding sites are predominantly mucosal.
Haemarthrosis are rare but menorrhagia and GI bleeding are common
vWF concentrates are avialable
DDAVP
In pateints with severe vWD replacement therapy with factor 8 is the form of intermediate purity factor 8 concentrate is the method of choice. The intitial dose is 50IU/kg followed by 20-40 IU/kg every 12 hours.
Describe DIC
Relatively common acquired coaguloatphy .
1) Platelets and coag factors are consumed especially fibrinogen and facotrs 5,8,13
2) Thrombin is fomred and it overhwhelms its inhibitor system and acts to accerleate the coagulation process
3) fibrin is deposited in small vessels in multiple organs
4) the fibrinolytic system by menas of plasmin may lyse firbin and impair thrombin formation
5) fibrin degradation products are released and affect platelet function and inhibit fibrin polymerization
6) coag inhibitoin levels are decreased
The clinical consequence of these processes is the life threatening combination of bleeding diathesis from loss of platelets and clotting factors, fibrinolysis and fibrin degration product interference; small vessel obstruction and tissue ischaemia from fibrin deposition and RBC injury and anaemia
Discuss Coag profile of DIC
Platelets low <100 PT prlonged PTT prolonged Fibrongen low Fibrin degradation products high
