VTE Flashcards

Question

What are contraindications to LMWH?

Answer 1

``` Active bleeding Allergy Severe renal / liver disease Thrombocytopenia, Plt < 75 Known bleeding disorder Acute stroke in previous 4 weeks (Haemorrhagic / ischaemia) Uncontrolled HTN ```

Answer 2

Shorter half life - required interval between prophylactic UFH and regional anaesthesia is less ( 4 hours c.f. 12 hours with LMWH) More complete reversal with Protamine sulphate Less concern regarding neuraxial haematomas

Answer 3

Crosses placenta Embryopathy in approx 5% of fetuses exposed between 6-12/40 Dose dependent, higher incidence if >5mg/ day ``` C-ongenital heart defects H-ypoplasia of nasal bridge V-entriculomegaly A-genesis of corpus callosum S-tipple epiphysis ``` ``` Other adverse effects Miscarriage Stillbirth Neurological impairment Fetal and maternal haemorrhage ```

Answer 4

- Significant family Hx is only for 1st degree relatives - Correlated with increased risk of VTE in pregnancy/postpartum - Risk stratified to high risk and low risk thrombophilias LOW RISK - Antenatal LMWH not usually required - Extended LMWH postpartum should be considered if other risk factors HIGH RISK - factor V leiden homozygous, protein c or protein s deficiency, multiple inherited thrombophilias - consider antenatal prophylactic LMWH AND prolonged 6 week postpartum course - Antithrombin (factor Xa) deficiency particularly high risk therefore consider intermediate/therapeutic dose antenatally and for 6 weeks postpartum (SOMANZ)

Answer 5

- The majority of inherited thrombophilias have minimal increased risk of VTE - The high risk conditions: antithrombin deficiency, factor V leiden homozygous, protein c and protein s deficiency, >1 thrombophilic marker Low risk thrombophilia - no need for antenatal or extended postnatal LMWH High risk thrombophilia and no FHx VTE - extended 6 week postnatal prophylaxis only High risk thrombophilia and positive FHx VTE - consider antenatal prophylaxis - extended 6week postnatal prophylaxis Antithrombin deficiency - The most high risk thrombophilia, 11% risk antenatal VTE and 29% risk postnatal VTE, which increases significantly if FHx of VTE - Antenatal prophylaxis with intermediate of therapeutic dose LMWH - extended 6week postnatal prophylaxis (SOMANZ)

Answer 6

CTPA - NPV 100%, sensitivity 83% - Higher dose of radiation and therefore higher risk for future breast cancer (1/2000 lifetime risk - though likely lower now with modern radiology techniques) - Useful in detecting other lung pathology - More widely available, less delay in diagnosis - Can continue breast feeding after - Can lead to over diagnosis - More sensitive to detecting SSPE - but these are of little clinical significance with no increase in mortality or recurrence if treated or not V/Q - NPV 100%, sensitivity 100% - Nuclear imaging not as widely available - Lower dose of radiation and lower risk of future breast cancer (1/40,000 lifetime risk - though likely lower with modern radiology techniques) - Lower rate of non-diagnostic studies, particularly in the third trimester - Must avoid breast feeding for at least 12 hours due to increased passage of radioactive contrast in breast milk Both studies give negligible doses of radiation to the fetus (<1mSv), well below the threshold (10mGy) for increased risk of miscarriage, genetic damage or congenital malformation. Even if this threshold is exceeded the risk of additional childhood cancer is roughly 2/1000. Perfusion only scanning is generally not recommended due to the relatively low levels of radiation and risks associated. - NPV 83%, sensitivity 60% - If abnormal perfusion scan, then need to do a ventilation scan after - 1/4 - 1/2 studies are inconclusive (SOMANZ 2021)

Answer 7

CTPA - NPV = 100%, sensitivity 83% V/Q - NPV = 100%, sensitivity 100%

Answer 8

- Do not avoid doing necessary scan due to concerns about radiation - the radiation exposure is minimal with both CTPA and V/Q scanning and is far outweighed by the potential risks of PE. - Both CTPA and V/Q are safe and acceptable options - In clinically stable women with a normal CXR - preference is for V/Q scan - If clinically unstable women or with CXR abnormalities, a CTPA is preferred Others: - Echo can be considered in unstable women to assess evidence of right heart strain and aid risk stratification - If multiple scans are performed calculate the breast and fetal radiation exposure - If radiation contraindication non-gadolinium MRA can be considered if available

Answer 9

- Choose V/Q scan instead or perfusion-only - bismuth protective shield for breasts ( reduces by 50%) - Reduced contrast monitoring component of CTPA

Answer 10

- Most common cause of direct maternal death in Aus | - 3rd most common cause of direct maternal death in NZ

Answer 11

LMWH - 12 hours CS - 12 hours epidural placement or removal - Can restart 4 hours after epidural removal - Can restart 6-12 hours after delivery UFH - 4-6 hours CS - 4-6 hours epidural placement or removal - Can restart 1 hour after epidural removal

Answer 12

LMWH - 24 hours CS - 24 hours epidural placement or removal - Can restart 4 hours after epidural removal - Can restart 12-24 hours after delivery UFH - 24 hours CS BUT 4-6 if given IV - 24 hours epidural placement BUT 4-6 if given IV - 4-6 hours before removal - Can restart 1 hours after epidural removal

Answer 13

- All routine care and work-up - Senior obs review and senior anaesthetic review - Stop anticoagulation - Decision re. timing - can delivery be delayed till reversal of thromboprophylaxis - Ensure IV access, FBC and G&H - Measure anti-Xa levels for LMWH, and APTT for UFH - Liase with haematology and Consider administration of protamine (more effective for reversal of UFH) - Ensure plan in place for recommencing anticoagulation postpartum

Answer 14

Binds to antithrombin causing structural change and increasing its activity, thus: - inhibits factor Xa cleavage of prothrombin to thrombin (factor IIa), and acts directly to inhibit thrombin - which is required for cleavage of fibrinogen to fibrin involved in stable clot formation.