GTG: Preventing and Treating VTE Flashcards
Incidence of VTE in pregnancy/puerperium
1-2 per 1000
Incidence of antenatal PE
1.3 per 10,000
Which side are 90% of DVTs located?
Left
Where are 70% of DVTs located?
Above knee (ileofemoral)
When is the highest risk for VTE?
Postnatal highest risk. Within pregnancy, 3rd trimester highest risk.
What percentage of patients experiencing a VTE had identifiable risk factors?
70%
What is the effect of LMWH on reducing risk of VTE?
Medical patients 60%, Surgical patients 70%, Obstetric patients with previous VTE 88%.
In what proportion of pregnancy related VTE is a heritable thrombophilia found?
20-50%
What percentage of women who died from PE were obese?
60%
What do the VTE “scores” advise re: prophylaxis?
Antenatal score 4 or more - LMWH from first trimester.
Antenatal score 3 or more - LMWH from 28 weeks.
Postnatal score 4 - 6/52 LMWH.
Postnatal score more than 3 or persistent - consider LMWH 6/52.
Postnatal score 2 - 10 days LMWH.
Factors which score “4” on VTE assessment
- Previous VTE episode (except for isolated surgical provoked VTE)
- OHSS
Factors which score “3” on VTE assessment
- Previous isolated surgically provoked VTE
- High risk thrombophilia
- Medical co-morbidities
- Hyperemesis
- Any surgical procedure in pregnancy or puerperium
Factors which score “2” on VTE assessment
- BMI > 40
- Emergency Caesarean in labour
Factors which score “1” on VTE assessment
- Low risk thrombophilia
- FHx of VTE < 50 years
- Age > 35 years
- Parity 3 or more
- BMI > 30
- Smoking
- Varicose veins
- PET
- Stillbirth
- PTB
- PPH
- Prolonged labour
- Infection
- ELCS
- Midcavity delivery
- ART/IVF (antenatal only)
- Multiple pregnancy
- Immobility
When to consider LMWH for admission?
Any antenatal admission and prolonged admission >3 days postnatal or any readmission to hospital within puerperium
If pt gives history of VTE but cannot be confirmed, when can it be assumed?
Good history and received >6/52 anticoagulation.
Recurrence rate of VTE in pregnancy
10%
When to test for thrombophillias in pregnancy?
If previous VTE and family history of VTE - test antithrombin.
If previous history of unprovoked VTE - test APLS.
If no personal history of VTE but family history under age 50 - consider.
Which thrombophilias are classed as high risk?
ANtithrombin deficiency
Protein C/S deficiency
Homozygous factor V Leiden or prothrombin mutation.
Which thrombophilias are classed as low risk?
Heterozygous factor V Leiden or prothrombin mutation.
APLS.
Which thrombophilias require dose adjustment of LMWH?
- Antithrombin deficiency (may require anti-Xa levels monitoring)
- APLS
What are target anti-Xa levels?
Peak (4 hours post administration) 0.5-1.0
Doses of LMWH
Weight brackets: <50, 50-90, 90-130, 130-170, >170
Enoxaparin: 20mg, 40mg, 60mg, 80mg, 0.6mg/kg/day
Dalteparin: 2500u, 5000u, 7500u, 10000u, 75u/kg/day
Tinzaparin: 3500u, 4500u, 7000u, 9000u, 75u/kg/day
At what level of renal impairment do doses need to be adjusted?
CrCl<30ml/min (<20 for tinzaparin).
Roughly corresponds to Cr of 200 in a 70kg 30F.
Risks associated with LMWH
Osteoporotic fractures 0.04%
Skin allergic reactions 1.8%
Bleeding/wound haematoma 2%
When might you use unfractionated heparin?
Pericardium in women at high risk of VTE but concerns re: bleeding or regional.
How long after unfractionated heparin before regional anaesthetic?
4 hours
What monitoring required for unfractionated heparin?
Platelets every 2-3 days from D4-14 or until heparin stopped.
Alternatives to LMWH
Danaparoid or fondaparinux in conjunction with haematology in patients intolerant of LMWH.
Warfarin only if heparin not suitable.
What calf pressure should be achieved by TED stockings?
14-15mmHg
What percentage of foetuses exposed to warfarin 6-12w develop warfarin embryopathy?
5%
Features of warfarin embryopathy
Stippled epiphyses Congenital heart defects Hypoplasia nasal bridge Ventriculomegaly Agenesis corpus callosum
How long after LMWH for procedures?
12h after prophylaxis for regional insertion or removal. 24h after therapeutic for regional.
Can give LMWH 4 hours after regional removal.
ELCS omit any morning doses but can have the dose the day before delivery.
What percentage of suspected PE/DVT will be confirmed?
2-6% of PE, 8% of DVT.
If untreated, what percentage of patients with a DVT will go on to develop a PE?
15%
What is the mortality rate associated with PE in pregnancy?
15%
Investigation pathway for DVT in pregnancy
Compression duplex ultrasound.
If positive then diagnosis is confirmed. If negative but high clinical suspicion then stop treatment and repeat scan D3 and D7.
If iliac vein thrombosis suspected (back and buttock pain and swelling of entire limb) - Doppler ultrasound iliac vein or venography.
What percentage of cases of PE have abnormal ECG?
41%.
T wave inversion 21%
S1Q3T3 15%
RBBB 18%
What percentage of cases of PE have a normal CXR?
50%
What is the increase in childhood cancers with CTPA/VQ scans?
0.006% increase per mGy (1 in 17000 per mGy).
CTPA 0.1mGy, VQ 0.5mGy
What is the increase in breast cancer with CTPA scans?
13.6% increase in breast cancer. (E.g. a 25F has a background risk of 0.1% over next ten years. A CTPA will increase her risk to 0.1136%.
Treatment of VTE in pregnancy
LMWH.
Weight categories: <50, 50-70, 70-90, 90-110, 110-125, >125
Enoxaparin: 40mg BD or 60mg OD, 60mg BD or 90mg OD, 80mg BD or 120mg OD, 100mg BD or 150mg OD, 120mg BD or 180mg OD, discuss with haem.
Dalteparin: 5000 BD, 6000 BD, 8000 BD, 10000 BD, 120000 BD, discuss with haem. (All of these can be doubled and given once per day)
Tinzaparin: 175units/kg OD.
When to measure anti-Xa levels during treatment of VTE?
If extremes of body weight (<50 or >90) or other complicating factors.
Treatment for massive PE with collapse
Intravenous unfractionated heparin.
If haemodynamic compromise and life/limb threatening - thrombolysis and then IV heparin.
Dosing of IV heparin
Loading dose 80 units/kg (omit if thrombolysed) and then continuous infusion 18 units/kg/hour
Monitoring required during IV heparin
APTT 4-6h after loading, 6h after any dose change and at least daily whilst therapeutic. Target APTT 1.5-2.5x reference range.
(If <1.2 then increase dose by 4 and rebolus 80, if 1.2-1.5 then increase dose by 2 and rebolus 0, if 2.5-3 then reduce by 2 and if >3 then reduce by 3 and stop infusion for 1 hour)
What stockings are required following a DVT?
Graduated elastic compression stockings - Class I pressure >23mmHg on affected leg
Benefits and risks of thrombolysis
Reduces death (19% with heparin alone, 9% with thrombolysis) 2.9% risk maternal bleeding, 1.7% risk fetal death.
How long to continue treatment?
LMWH during remainder of pregnancy and for at least 6 weeks postnatal and until at least 3 months treatment given in total.
Risk of post-thrombotic syndrome
42% (reduced by LMWH >12 weeks and class I stocking on affected leg for 1 year)
How to manage labour and delivery in someone on therapeutic anticoagulation?
Consider unfractionated heparin.
24h free from therapeutic LMWH for regional.
After CS give prophylactic dose 4 hours post-op and recommence treatment dose 8-12h later.
Consider wound drains and interrupted skin sutures at CS
Incidence of wound haematology on therapeutic anticoagulation
9% (compared to 1.3% controls)
Chance of recurrent VTE on LMWH
1.2%