Influence of sequential pneumatic compression on postoperative venous function

Abstract

Sequential external pneumatic compression (SEPC) has been reported to decrease the incidence of acute deep venous thrombosis in postoperative patients by a direct mechanical action on the lower extremity veins and/or by inducing alterations in systemic fibrinolysis. To evaluate the effect of SEPC on venous function in the postoperative patient, pre- and postoperative venous capacitance (VC) and outflow (VO) were measured in a series of general surgical patients. In phase I, 17 limbs were evaluated in patients who had been fully ambulatory preoperatively and at complete bed rest postoperatively. VC decreased from 3.19 ± 0.43 cc/100 cc of tissue (mean ± standard error of the mean) preoperatively to 2.08 ± 0.34 cc/100 cc of tissue postoperatively (p < 0.05) and VO decreased from 87.2 ± 10.6 cc/100 cc of tissue/min preoperatively to 58.1 ± 8.7 cc/100 cc of tissue/min postoperatively (p < 0.025). In phase II SEPC was begun preoperatively and continued for 24 hours postoperatively on one limb of 20 patients. SEPC prevented the decrease in VC and VO both in the pumped leg (VC—2.65 ± 0.26 cc/100 cc of tissue preop, 2.40 ± 0.18 cc/100 cc of tissue postop, p > 0.2; VO—72.3 ± 5.9 cc/100 cc of tissue/min preop, 66.2 ± 5.3 cc/100 cc of tissue/min postop, p > 0.2) and in the unpumped limb (VC—2.85 ± 0.18 cc/100 cc of tissue preop, 2.41 ± 0.24 cc/100 cc of tissue postop, p > 0.05; VO—66.1 ± 5.2 cc/100 cc of tissue/min preop, 66.7 ± 6.7 cc/100 cc of tissue/min postop, p > 0.5). SEPC prevents the decrease in VC and VO seen in patients who are maintained at complete bed rest after general surgical procedures. This improvement in parameters of venous function as measured by strain-gauge plethysmography may be induced by direct mechanical effects on the vein wall, humoral or neurogenic factors, or a Venturi effect through increased flow velocity in the vena cava. Increased femoral vein flow velocity or reflex calf muscle contractions could not be demonstrated in the contralateral limb of five normal control subjects.