Deep Vein Thrombosis (DVT)

Definition: A blood clot embedded in a major vein of the lower leg, thigh or pelvis.

Causes:
· Damage to the inside of blood vessels.
· Change in normal blood flow, including turbulence, partial or complete blockage of blood flow.
· Hypercoagulability.
(Virchow’s triad)



Risk Factors:
Prolonged immobility.
Recent Surgery.
Recent trauma to lower body, inluding fractures.
Obesity.
Heart failure/myocardial infarction.
Pregnancy / Recent childbirth.
Increased altitude.
Use of oestrogen replacement / birth control pills.
Malignant tumour.
Genetic disorder - coagulpathy.
Disseminated intravascular coagulation.
Previous DVT.
Family hisory of DVT.
Dehydration.
Smoking.

Signs and Symptoms:
Swelling/oedema in the distal extremity.
Pain/tenderness.
Redness / blud-white discolouration of the skin.
Warmth.
Leg pain, worsening on dorsifexion (Homan's sign).
Palpable clot.
Petechiae.
Leg cramps, particularly at night.

Prevention:
Prophylactic fragmin following surgery.
TED stockings/flotron boots followig surgery.
Flight socks.
Leg exercise when immobile.
Adequate fluid intake following surgery / when immobile.
Weight loss.
Avoid prolonged immobility.
Elevation of legs if at risk.
Avoid oestrogen / BC pills.
Exercise following surgery.

Pathophysiology:
Blood normally flows quickly through veins, therefore does not clot. The formation of a clot can be triggered when platelets come into contact with endothelial damage. Platelets clump together, releasing chemicals that start the coagulation cascade. This entraps subsequent blood vessels, causing reduced blood flow, allowing the clot to increase in size, eventually partially/completely blocking the vein.


Diagnosis:
Doppler ultrasound.
Venography.
CT scan.
Pro-thrombin time needs to be established.
D-dimer test -tests the level of fibrin degradation products. A raised level indicats significant clot formation and breakdown.


Complications:
Pulmonary Embolus.
Death.
Recurrent DVT.
Post phlebitic syndrome.
Venous insufficiency.
Pain.
Gangrene.
Amputation.
Stroke.

Treatment:
Bed confinement for 24 hours, foot raised 15-30 degrees.
TED stockings / flotron boots.
Exercise encouraged.
5 day heparin / warfarin course (baseline ProThrombin needs to be established to determine dose).
Surgery to remove the clot when viability of the limb is threatened.

DVT in pregnancy
Pregnancy is a hypercoagulable state, resulting from the increase in clotting factors, which is a physiological process thought to minimise blood loss following separation of the placenta at delivery. Venous stasis begins to occur by the end of the first trimester, reaching a peak at 36 weeks gestation. Endothelial damage can occur during vaginal delivery or caesarean section, further more increasing the risk of developing a DVT.

Risk factors
Hyperemesis.
Diarrhoea.
Multiple pregnancy.
Partiy >4.
Varicose veins.
Inflammatory bowel disease.
Prolonged labour.
Assisted vaginal delivery - forceps / ventouse.
Caesarean section.
Epidural in situ.
Indwelling catheter.

CEMACH identified 30 deaths due to thrombosis in the period 2000-2002. Of these, 25 were from thromboembolism and 5 from cerebral vein thrombosis. Substandard care was identified in 17 (57%) of case, in the form of delayed treatment, diagnosis and inadequate thromboprophylaxis. 19 of the 25 cases had specific risk factors identified.

Four deaths occured in the antenatal period, three of which had a previous history of DVT. Sixteen women died in the postnatal period.

Recommendations:
Use of antenatal risk assessment tool.
Use of risk assesment tool for women undergoing caesarean section.

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