Thromboprophylaxis In Surgery

Thromboprophylaxis is the use of mechanical and pharmacological methods to prevent the development of venous thrombosis.

It is a frequently used term in the field of Surgery, as it is not uncommon for the patients to develop deep vein thrombosis following surgery. 

Deep vein thrombosis (DVT) can occur insidiously in many surgical patients and if these patients are not addressed properly, they can lead to pulmonary embolism resulting in death

Therefore prevention of DVT is essential and thromboprophylaxis plays a major role in it.  

Certain surgical patients carries a higher risk of developing DVT and identification of such patients also carries a great value in prevention of DVT. 


Risk Factors Of DVT

  • Surgery
    • Duration of surgery more than 90 minutes (Any surgery)
    • Duration of surgery more than 60 minutes (Surgery involving lower limbs or pelvis)
  • Acute abdomen with inflammation within the abdomen 
  • Immobility / Reduced mobility – Paralysis
  • Age more than 60 years
  • Malignancy
  • Thrombophilia
  • Previous venous thromboembolism
  • BMI 30 and above 
  • HRT and OCP
  • Varicose veins with phlebitis
  • Associated co-morbidities (Stroke, CCF, MI)



Risk Stratification For Venous Thromboembolism


Prevention Of Venous Thrombosis

Preventive methods can be adopted even before surgery. There are two methods, when used in combination, it increases the effective than either modality alone. 

  • Non pharmacological methods / Mechanical methods
  • Pharmacological methods 


Mechanical Methods
Mechanical methods promote venous outflow and thereby avoid venous stagnation
Mechanical methods are….
  • Elastic stocking 
  • Graduated compression stockings 
  • Intermittent pneumatic compression
  • Early ambulation following surgery – Cheap and effective

Pharmacological Methods

These methods acts by attenuating coagulation
Mainly used agents are….

  • Low molecular weight heparin (LMWH)
  • Unfractionated heparin 
  • Dabigatran 
  • Warfarin
  • Aspirin


Heparin

  • Types
    • Low molecular weight heparin (LMWH)
    • Unfractionated heparin (UH) 
  • Mechanism of action 
    • Binds with antithrombin III and inhibit thrombin and Factor Xa 
  • Monitoring
    • UH – Monitoring with APTT is required 
    • LMWH – No monitoring is required  
  • Antidote
    • UH – Action can be reversed by using protamine sulfate 
    • LMWH – Cannot be reversed 
  • Complications
    • Haemorrhage
    • Osteoporosis 
    • Heparin induced thrombocytopenia
    • Anaphylaxis 
 
Warfarin
  • Mechanism of action
    • Inhibits the reduction of vitamin K to its’ active form
    • Reduce formation of vitamin K dependent clotting factors II, VII, IX, X 
  • Monitoring
    • PT / INR  
  • Antidote 
    • Vitamin K  
  • Complications
    • Hemorrhage
    • Warfarin embryopathy
    • Skin necrosis 
      • Warfarin → Reduces protein C → Thrombosis of venules → Skin necrosis
Dabigatran
  • Mechanism of action
    • Direct inhibition of thrombin  
  • Monitoring
    • Not required 
  • Antidote 
    • Idarucizumab  
  • Contraindications
    • Should not be used on patients’ with risk of bleeding 
Aspirin
  • Mechanism of action
    •  Inhibits platelets by acetylating cyclooxygenase-1 enzyme 
  • Monitoring
    • Not required 
  • Complications 
    • GI bleeding
    • Electrolyte disturbance 
    • Hypoglycemia
    • Prolong prothrombin time 
    • Cerebral oedema and pulmonary oedema 
 
 
Thromboprophylaxis In Practical Setting
  • Low risk patients
    • No need of specific methods
    • Early ambulation is satisfactory
  • High risk patients
    • Preoperative thromboprophylaxis
      • Should be considered in major surgeries, specially in orthopedic surgery
      • LMWH should be started 12 hours prior to procedure
      • Intermittent pneumatic compression or elastic stocking can be used as a combination with LMWH to maximize the effect
    • Postoperative thromboprophylaxis
      • LMWH or warfarin titrated to an INR of 2 – 3 can be used postoperatively for 10 days 
      • Intermittent pneumatic compression with or without concomitant use of elastic stockings
      • Aspirin should be considered specially in vascular or cardio-thoracic surgeries 
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