Current issues of ACP Journal Club are published in Annals of Internal Medicine


Subcutaneous heparin plus pneumatic compression stockings prevented pulmonary embolism after cardiac surgery

ACP J Club. 1996 May-June;124:63. doi:10.7326/ACPJC-1996-124-3-063

Source Citation

Ramos R, Salem BI, De Pawlikowski MP, et al. The efficacy of pneumatic compression stockings in the prevention of pulmonary embolism after cardiac surgery. Chest. 1996 Jan; 109:82-5. [PubMed ID: 8549224]



To compare subcutaneous heparin alone with subcutaneous heparin plus pneumatic compression stockings for prevention of pulmonary embolism in patients having cardiac surgery.


Randomized controlled trial.


A hospital in Missouri, USA.


2551 patients (mean age 64 y, 70% men) who had open-heart surgery. Patients were excluded if they had confirmed deep venous thrombosis before surgery, bleeding complications, intraoperative death, or intolerance to pneumatic compression stockings or if they withdrew from the prophylaxis before becoming fully ambulatory.


Patients were allocated to subcutaneous heparin, 5000 U every 12 hours (n = 1196), or to the same dose of heparin and pneumatic compression stockings (n = 1355). The stockings were inflatable plastic leg sleeves with 2 calf chambers and 1 thigh chamber. A sequential compression device (SCD 5325, Kendall Company, Boston) generated a compression wave to a peak pressure of 35 to 40 mm Hg for 11 seconds every 60 seconds. Both prophylaxis methods were started immediately after surgery and continued for 4 to 5 days or until patients were fully ambulatory.

Main Outcome Measure

Incidence of objectively confirmed, symptomatic pulmonary embolism after surgery.

Main Results

Prophylaxis with subcutaneous heparin plus pneumatic compression stockings led to a lower incidence of pulmonary embolism than did prophylaxis with subcutaneous heparin alone (P < 0.01) (Table).


The addition of pneumatic compression stockings to prophylaxis with subcutaneous heparin reduced the incidence of pulmonary embolism in patients who had cardiac surgery.

Source of funding: Not stated.

For article reprint: Dr. B.I. Salem, 222 South Woods Mill Road, Suite 500-North, Chesterfield, MO 63017, USA. FAX 314-205-6985.

Table. Subcutaneous heparin plus pneumatic compression stockings vs heparin alone for preventing pulmonary embolism after cardiac surgery*

Outcome by hospital discharge Heparin plus compression stockings Heparin alone RRR (95% CI) NNT (CI)
Pulmonary embolism 1.5% 4% 62% (47 to 71) 41 (26 to 82)

*Abbreviations defined in Glossary; RRR, NNT, and CI calculated from data in article.


The study by Ramos and colleagues is the largest to have evaluated use of pneumatic compression stockings for the prevention of venous thromboembolism. The addition of treatment with pneumatic compression stockings to low-dose heparin therapy resulted in a statistically significant and clinically important reduction in symptomatic pulmonary embolism after cardiac surgery.

In terms of the risk for developing venous thromboembolism after surgery, some differences between cardiac and noncardiac surgery are worthy of note. First, very high doses of heparin are administered during surgery while patients are on cardiopulmonary bypass. Second, because of their use in coronary bypass grafting, the superficial leg veins are commonly operated on. Despite these distinctive features of cardiac surgery, this study provides strong support for the use of mechanical and pharmacologic methods of prophylaxis in combination, particularly in patients at high risk for venous thromboembolism.

Mechanical methods of prophylaxis include graduated compression stockings, pneumatic compression stockings, or the two combined. It is unclear which method when combined with heparin gives the best results. In general surgical patients, graduated compression stockings plus heparin are more effective than heparin alone (1, 2). 2 small studies suggest that graduated compression stockings alone are as effective as graduated and pneumatic compression stockings combined (3, 4). In the absence of direct comparisons, it is not known whether graduated compression stockings are as effective as pneumatic ones when each is combined with heparin. Pneumatic compression stockings are more cumbersome to use than graduated stockings. Ramos and colleagues suggest that graduated compression stockings may have a detrimental effect on wound healing after leg-vein harvesting; however, this seems improbable (4).

This study supports the use of pneumatic compression stockings with low-dose heparin after cardiac surgery. Although the combination of graduated compression stockings and low-dose heparin may be as effective and more convenient in this setting, additional studies are required to determine this.

Clive Kearon, MB, PhD
McMaster UniversityHamilton, Ontario, Canada


1. Wille-Jorgensen P, Thorup J, Fischer A, Holst-Christensen J, Flamsholt R. Heparin with and without graded compression stockings in the prevention of thromboembolic complications of major abdominal surgery: a randomized trial. Br J Surg. 1985;72:579-81.

2. Torngren S. Low dose heparin and compression stockings in the prevention of postoperative deep venous thrombosis. Br J Surg. 1980;67:482-4.

3. Turpie AG, Hirsh J, Gent M, Julian D, Johnson J. Prevention of deep vein thrombosis in potential neurosurgical patients. A randomized trial comparing graduated compression stockings alone or graduated compression stockings plus intermittent pneumatic compression with control. Arch Intern Med. 1989;149:679-81.

4. Goldhaber SZ, Hirsch DR, MacDougall RC, et al. Prevention of venous thrombosis after coronary artery bypass surgery (a randomized trial comparing two mechanical prophylaxis strategies). Am J Cardiol. 1995;76:993-6.