I82
DESCRIPTION
An occulusive or non-occlusive thrombus in the venous circulation, with or without pulmonary embolus. Associated risk factors included central venous catheters, venous stasis, endothelial damage and hypercoaguable states, e.g. nephrotic syndrome. Causes include protein C and S deficiency, factor V leiden and antithrombin III deficiency.
DIAGNOSTIC CRITERIA
Clinical
Depends on the site of thrombosis, may be silent.
- Deep venous thrombosis of an extremity presents with unilateral limb swelling.
- Upper extremity thrombus may present with associated facial and neck oedema.
- Pulmonary embolus presents with sudden onset of shortness of breath and chest pain.
- Cerebral sinus venous thrombosis presents with seizures or other neurological symptoms and signs.
- Renal vein thrombosis presents with haematuria, thrombocytopaenia, oliguria and renal failure if bilateral.
Investigations
- Doppler ultrasonography, CT scan or MRI demonstrate thrombosis or embolus.
- D-dimer, antithrombin III, protein C, protein S, Factor V Leiden and antiphospholipid antibody testing may reveal underlying thrombophilia.
GENERAL AND SUPPORTIVE MEASURES
- Appropriate fluid restriction and electrolyte management if renal failure.
If hypoxic:
- Oxygen by face mask.
For acute thrombotic episode:
- Low molecular weight heparin e.g.
- Enoxaparin sodium, SC, 1 mg/kg 12 hourly
OR
- Unfractionated Heparin (UFH), IV, administered over 10 minutes as a bolus followed by an initial maintenance dose as a continuous infusion.
| Bolus | Initial maintenance dose | |
|---|---|---|
| Preterm neonates | 25-50 units/kg | 15 units/kg/hour |
| Term neonates | 75-100 units/kg | 28 units/kg/hour |
| Children | 75 -100 units/kg | 20 units/kg/hour |
Note: Neonates need a higher maintenance dose per body weight compared with older children.
Target levels
If available LMWH dosing can be guided by anti-Xa levels 3-4 hours after dose.
For UFH
PTT: 60–85 seconds or 2–3 times the baseline value (if normal for age).
Monitor PTT 4 hours after bolus injection and adjust the continuous IV dose according to the result (See table below)
Nomogram for adjusting UFH dose*
|
PTT (seconds) |
Bolus (units/kg) |
Hold infusion (minutes |
Dose change |
Repeat PTT (hours) |
|---|---|---|---|---|
| <50 | 50 | 0 | Increase by 20% | 4 |
| 50-59 | 0 | 0 | Increase by 10% | 4 |
| 60-85 | 0 | 0 | No change | 24 |
| 86-95 | 0 | 0 | Decrease by 10% | 4 |
| 96-120 | 0 | 30 | Decrease by 10% | 4 |
| >120 | 0 | 60 | Decrease by 15% | 4 |
* The sensitivity of the PTT towards UFH depends on the reagent used.
Maintain PTT 2.5–3.5 times the control.
Discontinue heparin once therapeutic INR is achieved with warfarin.
Table reproduced from Venous thromboembolism: Prophylactic and therapeutic practice guideline. S Afr Med J 2013;103(4):260-267. Published with kind permission.
AND
- Warfarin, oral, 0.1 mg/kg daily from day 1.
- Target INR: 2–3.
- Continue warfarin therapy for 3–6 months if no underlying severe thrombophilia.
- Inherited thrombophilic conditions may need lifelong therapy.
- Beware of drug interactions.
| Weight | Starting dose of warfarin |
|---|---|
| 10-20 kg | 2.5 mg alternate days |
| 20-35 kg | 2.5 mg daily |
| 35-50 mg | 2.5 mg alternating with 5 mg daily |
| 50 kg+ | 5 mg daily |
Adjust schedules using combinations of 2.5 mg and 5 mg or 5 mg and 7.5 mg or 7.5 mg and 10 mg if a standard daily dose does not provide a therapeutic INR. For example: 2.5 mg Monday, Wednesday, Friday and 5 mg Tuesday, Thursday, Saturday, Sunday.
REFERRAL
- All patients to an appropriate centre for diagnostic imaging.
- Long term management of thrombophilic states should be in consultation with a paediatric haematologist or paediatrician.