I80.0-3/I80.8-9/I81/I82.0-3/I8.8-9/I26.0/I26.9
DESCRIPTION
Venous thromboembolism (VTE) should be seen as a spectrum from calf deep venous thrombosis (DVT) to pulmonary thrombo-embolism. All patients should be seen as potentially high risk.
Differential diagnosis includes:
- cellulitis
- ruptured popliteal (Baker’s) cyst
- superficial thrombophlebitis
- calf muscle pull or tear
- lymphoedema
- internal derangement of the knee
- chronic venous insufficiency
Diagnosis is primarily clinical and confirmed with imaging studies, e.g. Duplex Doppler.
GENERAL MEASURES
Strategies for prevention include: lifestyle modifications like avoiding obesity and inactivity, avoiding dehydration, avoiding cigarette smoking, maintaining normal blood pressure, and mechanical measures like vascular compression stockings and intermittent pneumatic compression boots.
Acute management
Thrombolytic therapy may be indicated in patients with confirmed early pulmonary embolism where haemodynamic stability cannot be achieved. Discuss with a specialist.
MEDICINE TREATMENT
PROPHYLAXIS
Risk Assesement
Risk assessment is essential, and treatment needs to be individualised. Risk factors for VTE can be divided into predisposing factors (i.e. patient characteristics) and exposing factors (i.e. underlying medical conditions, nature of surgical intervention, etc.).
SUBCATEGORIES OF VTE RISK IN SURGICAL AND NON-SURGICAL PATIENTS
| Surgical patients | Medical patients | |
| Low VTE risk |
» Surgery lasting <30 minutes » Injuries without or with only minor soft-tissue trauma » No or only minor additional predisposing risk factors |
» Infection or acute inflammatory diseases without bed rest » Central venous catheters » No or only minor additional predisposing risk factors |
|
Moderate VTE risk |
» Surgical procedures of longer duration » Immobilisation of lower limb with plaster cast » Lower limb arthroscopic procedures. » No or only minor additional predisposing risk factors |
» Acute cardiac insufficiency (NYHA III/IV) » Acute decompensated COPD without ventilation » Infection or acute inflammatory diseases with bed rest » Malignant disease » No or only minor additional predisposing risk factors |
| High VTE risk |
» Major surgical procedures for malignancy » Multiple trauma or severe trauma of the spine, vertebra or » lower limbs » Major orthopaedic surgery, e.g. hip or knee replacement » Major surgical procedure of cardiothoracic and pelvic region |
» Stroke with paralysis » Acute decompensated COPD with ventilation » Sepsis » ICU patients |
Source: Jacobson BF, Louw S, Büller H, Mer M, de Jong PR, Rowji P, Schapkaitz E, Adler D, Beeton A, Hsu HC, Wessels P, Haas S; South African Society of Thrombosis and Haemostasis. Venous thromboembolism: prophylactic and therapeutic practice guideline. S Afr Med J. 2013 Feb 15;103(4 Pt 2):261-7.
https://www.ncbi.nlm.nih.gov/pubmed/23547704
Some risk assesement models for assessing VTE risk:
| Model | Url link to tool |
| Padua Prediction Score[22] | https://www.mdcalc.com/padua-prediction-score-risk-vte/ |
| IMPROVE VTE risk score[23] | https://www.outcomes-umassmed.org/IMPROVE/risk_score/vte/index.html/ |
| Geneva risk score[24] | https://www.mdcalc.com/geneva-risk-score-venous-thromboembolism-vte-prophylaxis/ |
Prophylactic treatment
Prophylaxis is indicated for medical patients with moderate to high risk of VTE (see table above), with restricted mobility during acute illness/ surgical patients.
- Low molecular weight heparin, e.g.:
- Enoxaparin, SC, 40 mg daily.
In morbid obesity dosing of LMWH should be individualised, in discussion with a specialist.
In renal failure (eGFR <30 mL/minute), the recommended dose of LMWH is 1 mg/kg daily.
OR
- Unfractionated heparin, SC, 5 000 units 12 hourly.
Although the risk of bleeding is small, in the following patients prophylaxis should only be used under exceptional circumstances:
- active bleeding
- intraocular, intracranial or spinal surgery
- lumbar puncture or spinal/epidural anaesthesia within 12 hours after prophylactic dose or 24 hours of full therapeutic dose, [Timing of anticoagulants for patients receiving anaesthesia: See: Spinal (intrathecal) anaesthesia]
- renal insufficiency
- coagulopathy
- uncontrolled hypertension
ACUTE TREATMENT
Unfractionated or low molecular weight heparin started simultaneously with warfarin. After 5 days, heparin may be stopped if a therapeutic INR level has been reached and maintained for at least 24 hours.
Note: Heparin and warfarin therapy should overlap for at least 5 days.
For proximal deep venous thrombosis and/or pulmonary embolism:
- Low molecular weight heparin, e.g.:
- Enoxaparin, SC, 1.5 mg/kg daily,
or
1 mg/kg 12 hourly.
In morbid obesity dosing of LMWH should be individualised, in discussion with a specialist.
In renal failure (eGFR <30 mL/minute), the recommended dose of LMWH is 1 mg/kg daily.
OR
- Unfractionated heparin, SC, 333 units/kg as an initial dose.
- Follow 12 hours later by 250 units/kg/dose 12 hourly.
|
Units of unfractionated heparin |
Volume of heparin in mL (25 000 units/mL) |
|||
|---|---|---|---|---|
| Weight (kg) |
Loading dose (units) |
12 hourly dose (units) |
Loading dose (mL) |
12 hourly dose (mL) |
| 35 kg | 11 000 units | 8 750 units | 0.44 mL | 0.35 mL |
| 40 kg | 13 000 units | 10 000 units | 0.52 mL | 0.4 mL |
| 45 kg | 15 000 units | 11 250 units | 0.6 mL | 0.45 mL |
| 50 kg | 17 000 units | 12 500 units | 0.67 mL | 0.5 mL |
| 55 kg | 18 000 units | 13 750 units | 0.73 mL | 0.55 mL |
| 60 kg | 20 000 units | 15 000 units | 0.8 mL | 0.6 mL |
| 65 kg | 22 000 units | 16 250 units | 0.87 mL | 0.65 mL |
| 70 kg | 23 000 units | 17 500 units | 0.93 mL | 0.7 mL |
| 75 kg | 25 000 units | 18 750 units | 1 mL | 0.75 mL |
| 80 kg | 27 000 units | 20 000 units | 1.07 mL | 0.8 mL |
| 85 kg | 28 000 units | 21 250 units | 1.13 mL | 0.85 mL |
| 90 kg | 30 000 units | 22 500 units | 1.2 mL | 0.9 mL |
Evidence indicates that PTT monitoring is not necessary with weight- based dosing of unfractionated heparin. However, in patients with morbid obesity and renal failure (eGFR <30 mL/minute) unfractionated heparin should be used with PTT monitoring to maintain the PTT at 1.5 to 2.5 times the control.
PTT should be taken 4 hours after SC dose.
Follow with:
- Warfarin, oral, 5 mg daily.
- INR should be done after 48 hours, then every 1 to 2 days until within the therapeutic range of 2 to 3 (refer to Initiation dosing tables in the WARFARIN, oral).
- Adjust dose to keep INR within therapeutic range (refer to Maintenance dosing tables in the WARFARIN, oral).
- Continue warfarin for 3 months with regular INR monitoring if there was a precipitating cause that has resolved.
- In patients with a first unprovoked DVT, discuss duration of therapy with a specialist.
- Contraindications for warfarin: first trimester and the last month of pregnancy. In these instances, replace with heparin.
- For all major elective surgery and other elective procedures with a significant bleeding risk, such as neuraxial anaesthesia and lumbar punctures, the INR should be <1.5.
Heparin induced thrombocytopenia
A severe immune-mediated drug reaction occurring in 1–5% of patients receiving heparin (more common with unfractionated heparin, but may also occur with low molecular weight heparin) therapy. It presents with thrombocytopenia and thrombosis. Diagnosis needs a high index of suspicion and should be considered if a patient has a 50% drop in platelet count within 5–10 days after initiating heparin therapy. Confirmation is done by positive antibody testing.
Stop heparin and discuss all patients with a specialist.
REFERRAL/CONSULTATION
Heparin-induced thrombocytopenia.