This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Vascular surgery, Subject name: Surgery
Which of the following is the best way of preventing the development of deep vein thrombosis (DVT) in the postoperative period 
Select and explain. 
A. Early ambulation, B. Low dose aspirin, C. Prophylactic heparin, D. Physiotherapy
C: Prophylactic heparin
Answer: C: Prophylactic heparin 
Explanation: Patients are at increased risk for developing venous thromboembolism after: Major abdominal surgery Major ohopaedic surgery Has sustained major trauma Has prolonged immobility (>3 days) These patients need some form of prophylaxis. The prophylaxis can be mechanical or pharmacological. Prophylaxis for DVT Mechanical Prophylaxis include : Early ambulation It is the simplest method of prophylaxis It acts by activating the calf pump mechanism Pneumatic compression devices It is the most common method of prophylaxis Pneumatic compresses prevents the stasis by periodically compressing the calves. Pharmacological Prophylaxis include Use of unfractionated heparin - Now being replaced by fractionated low molecular weight heparin Use of fractionated low molecular - Better efficacy than unfractionated heparin weight heparin - No laboratory monitoring is necessary