External pneumatic compression has been advocated for the prevention of deep venous thrombosis during operative procedures. Which of the following statement(s) concerning the use of external pneumatic compression devices is/are true?

a. Intermittent pneumatic compression is as effective as low-dose heparin in prevention of venous thrombosis

c. Pneumatic compression devices may also exhibit their antithrombotic effect through stimulating local and systemic fibrinolysis

d. The length of time that intermittent pneumatic compression should be used includes through the operation and for at least several days in the postoperative period

In many well-controlled studies of venous prophylaxis, intermittent pneumatic compression has been found to be as effective as low-dose heparin therapy. In addition to augmentation of venous return with these devices, local and systemic fibrinolysis appears to be stimulated. Fibrinolytic activities are usually reduced for a 7–10 day period after an operation. Studies have demonstrated that the pneumatic-compression devices may exhibit their antithrombotic effect through prevention of this fibrinolytic shutdown even when applied to the upper extremity. The length of time that intermittent pneumatic compression should be used has not been adequately determined but most data suggest that devices should be used through the operation and for at least five days in the face or prolonged immobilization.