Thrombo-embolism in Pregnancy
Leg pain, chest pain or dyspnoea in a pregnant or recently pregnant woman should be considered to be due to thrombosis untill proved otherwise.
Incidence
- The incidence of non-fatal TE in pregnancy is not known
- 20% of maternal mortality
- Deep vein thrombosis (DVT) complicates about 2% of caesarean sections
Deep vein thrombosis (DVT) in pregnancy
The most common clinical features are:
- pain, local tenderness, swelling,
- oedema, a positive Homan’s sign
- change in leg colour and temperature and
- a palable thrombosed vein.
- Most cases are less obvious and some are silent
- Clinical diagnosis is, therefore unreliable.
- Over 80% are left-sided.
Diagnosis
- Limited Venography in 2nd/3rd trimester
- Doppler Ultrasound first choice (limited view iliacs)
- Radioactive fibrinogen uptake is contra-indicated
The main complications are PE and chronic vascular insufficiency.
(Superficial thrombo-phlebitis does not carry a significant risk of thrombo-embolism unless it extends to the deep veins)
Pulmonary Embolism in pregnancy
- There may be no prior clinical evidence of DVT.
- Pleuritic pain, haemopthsis, dyspnoea and varying degrees of shock.
- Chest pain, abdo pain, confusion, cardiac failure
- Collapse, cyanosis, cardiac arrest, death
- Consider also if there is no other obvious explanation for tachycardia, pyrexia or bronchospasm.
Differential Diagnosis
- Chest infection, pneumothorax, aspiration, amniotic fluid embolus, myocardial infarction.
Diagnosis
- Third heart sound, parasternal heave JVP
- Chest x-ray may be helpful but can be totally normal
- ABGs - pO2a < 70 mmHg, pCO2 normal
- ECG - usually normal except when the embolus is large and has produced acute cor pulmonale. Even these changes may be obscured by the usual ECG changes which occur in pregnancy (RAD)
- Ventilation - perfusion isotope (VQ) lung scan.
- Pulmonary angiography may need to be considered.
Management of DVT and pulmonary embolism
Heparin: unfractionated or LMW heparin does not cross the placenta or into breast milk so there is no added risk to the fetus.
- Acute therapy - intravenous calcium heparin 40,000 units daily for at least 48 hours.
- Long-term therapy - subcutaneous heparin. Twice daily unfractionated heparin (10,000 iu bd) or a single daily dose of low molecular weight heparin (40 mg/d enoxaprin). This does not add to the risk of haemorrhage even at caesarean section. Continue for at least 6 weeks post-partum (or Warfarin be substituted after delivery).
- Side-effects of long-term therapy - allergic reactions, thrombocytopaenia and maternal osteopaenia.
Warfarin it crosses the placenta readily but not significantly in breast milk.
- It is best avoided in the first trimester
because of a slight risk of embryopathy
- chondrodysplasia punctata (abnormal bone and cartilage formation)
- microcephaly
- mental retardation, cataracts, optic atrophy
- nasal hypoplasia, saddle nose, frontal bossing, short stature
- Even with meticulous control (prothrombin time to 2 to 2.5 times the clotting time for a normal control plasma), there is an increased risk of fetal haemorrhage as liver enzymes immature.
- Its anticoagulant effect cannot be reversed rapidly.
- Therefore heparin therapy is preferred .
- Because of the increased risk of haemorrhage if warfarin is used, change to heparin at 36 weeks’ gestation. If labour supervenes while the patient is taking Warfarin it can be counteracted with fresh frozen plasma
- Breast-feeding is not contra-indicated.
- It should be continued for at least 6 weeks after delivery.
Dextran 70 the risks of anaphylaxis to the mother and subsequent uterine hypertonus to the fetus may exceed any benefit. Therefore its use is best avoided during pregnancy.
Treatment of cardiac arrest from pulmonary embolism
- Prolonged external cardiac massage to break up the clot and produce pulmonary blood flow.
- Heparin 20,000 iu iv
- Hypotension Noradrenaline 2 mg in 500 ml saline, titrated to BP > 80
- Surgery Pulmonary embolectomy if no improvement
- Thrombolytic agents 100iu rTPA
