Abstract
Inciting events leading to deep vein thrombosis occur primarily intraoperatively. Therefore, if at all possible, intervention should be performed at the time of the operative procedure. It has been demonstrated in hip replacement surgery that DVT is significantly reduced with epidural hypotensive anaesthesia, which may or not be augmented with intraoperative small doses of heparin (500–1000 units). Reduction of extreme limb position with occlusion of the femoral vein during hip replacement surgery reduces the stasis effect, which promotes clotting. In the hip, overall DVT rates have been reduced to 7% and proximal DVT rates to 2% using these intraoperative techniques.
Mechanical devices work by a myriad of mechanisms: 1.) venous turbulence is created in valve pocket areas and this reduces clot formation; 2.) there is an increase release of endothelial relaxing factor (EDRF) which inhibits platelet aggregation; 3.) intermittent compression stimulates fibrinolysis by inducing release of urokinase and tissue plasminogen from the venous endothelium. Randomised trials have demonstrated a reduction in DVT to levels similar to pharmacologic agents (20–27%) without the risk of postoperative haemorrhage. However, compliance with use of these devices is crucia1, as a positive relationship has been demonstrated between time of use and DVT rates. Although plantar pump devices tend to be well tolerated with occasional complaints of foot and skin irritation, calf compression devices with or without sequential foot compression applying at least 50 mmHg of external pressure at a frequency of at least once per minute and an inflation rate of less than 1 second tend to be the ideal device for DVT prophylaxis.
The abstracts were prepared by Mrs Dorothy L. Granchi, Course Coordinator. Correspondence should be addressed to her at PMB 295, 8000 Plaza Boulevard, Mentor, Ohio 44060, USA.
