Cahan MA, Hanna DJ, Wiley LA, Cox DK, Kilewich LA.
External pneumatic compression and fibrnolysis in abdominal surgery.
J Vasc Surg 2000 Sep;32(3):537-43

Division of Vascular Surgery, Department of Surgery, University of Maryland
School of Medicine, Baltimore, MD, USA.

INTRODUCTION: External pneumatic compression (EPC) devices prevent lower
extremity deep venous thrombosis by increasing venous flow and thereby reducing
stasis. Early studies suggested that they also enhance systemic fibrinolytic
activity and thus prevent thrombus formation; more recent studies have been
conflicting. The hypothesis of this study was that EPC devices enhance systemic
fibrinolysis or reduce postoperative fibrinolytic impairment in patients
undergoing abdominal surgical procedures. METHODS: Each of 48 patients (98% male;
mean age, 67 years) undergoing major intra-abdominal surgical procedures (36
bowel procedures, 12 aortic reconstructions) was prospectively randomized to one
of three treatments for deep venous thrombosis prophylaxis: subcutaneous heparin
injections (HEP group), use of a thigh-length sequential EPC device (EPC group),
or both (HEP + EPC group). Antecubital venous samples were collected for
measurement of systemic fibrinolytic activity on the day before surgery, after
induction of anesthesia but before prophylaxis was initiated, and on
postoperative days 1, 3, and 5. Fibrinolysis was assessed through measurement of
the activities of the rate limiting fibrinolytic activator, tissue plasminogen
activator, and its inhibitor plasminogen activator inhibitor-1 with amidolytic
methods. RESULTS: On the day before surgery, plasminogen activator inhibitor-1
activity was elevated in all groups in comparison with that in age-matched and
sex-matched controls (20.3 +/- 0.6 AU/mL). In the HEP group, plasminogen
activator inhibitor-1 activity was further elevated above the value for the day
before surgery on postoperative day 1 (28.5 +/- 4.3 AU/mL; P =.04) and
postoperative day 3 (25.1 +/- 1.9 AU/mL; P =.07). No significant decrease in
plasminogen activator inhibitor-1 activity occurred in either group treated with
EPC devices in comparison with the HEP group at any time. There were no changes
in tissue plasminogen activator activity postoperatively in the HEP group and no
significant increases in either EPC group at any point. CONCLUSIONS: Reduced
systemic fibrinolytic activity ("fibrinolytic shutdown") occurred in these
patients after abdominal surgery; it was manifested as increased plasminogen
activator inhibitor-1 activity. EPC devices did not enhance systemic fibrinolysis
or prevent postoperative shutdown either by decreasing plasminogen activator
inhibitor-1 activity or by increasing tissue plasminogen activator activity.
These data suggest that EPC devices do not prevent deep venous thrombosis by
fibrinolytic enhancement; effective prophylaxis is achieved only when the devices
are used in a manner that reduces lower extremity venous stasis.