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Intermittent Pneumatic Compression Prophylaxis for Proximal Deep Venous Thrombosis after Total Hip Replacement*

STEVEN T. WOOLSON, M.D., STANFORD, CALIFORNIA

Investigation performed at Stanford University Hospital, Stanford

	Abstract

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The efficacy of intermittent pneumatic compression in the prevention of proximal deep venous thrombosis was determined in a consecutive series of patients who had primary or revision total hip replacement. Two hundred and eighty-nine patients (242 primary and eighty revision hip replacements) who were at least forty years old were managed intraoperatively and postoperatively with intermittent pneumatic compression with use of thigh-high sequential compression sleeves and thigh-high elastic compression stockings as the only form of prophylaxis. Venous ultrasonography of the ipsilateral lower extremity was performed, at an average of five days postoperatively, to determine the presence of a thrombus in the femoral and popliteal veins. The prevalence of proximal deep venous thrombosis was 6 per cent (twenty of 322 procedures), and no patient had a clinically detected pulmonary embolism. The prevalence of a proximal thrombus was 4 per cent (ten of 233 procedures) when a regional anesthetic had been used and 11 per cent (ten of eighty-nine procedures) when a general anesthetic had been used; this difference was significant (p = 0.02). The prevalence of a proximal thrombus was 3 per cent (eight of 245 procedures) for patients who were less than seventy-five years old and 16 per cent (twelve of seventy-seven procedures) for patients who were seventy-five years old or more (p < 0.0001). No patient had a major bleeding complication. Twenty-nine other patients who had an additional risk factor for thrombosis, such as a history of deep venous thrombosis, were managed with intermittent pneumatic compression and low-dose warfarin. The prevalence of proximal deep venous thrombosis in this group of patients was 19 per cent (six of thirty-one procedures). Intraoperative and postoperative intermittent pneumatic compression, combined with the use of a regional anesthetic, was found to be highly effective in the prevention of proximal deep venous thrombosis after total hip replacement. Despite the limitations inherent in comparisons among series, it is noteworthy that the prevalence of proximal thrombosis in our series was similar to the reported prevalences in several large series of patients who had a total hip replacement and were managed with either low-dose warfarin or low-molecular-weight heparin. However, there was no risk of major postoperative bleeding in the current study.

	Introduction

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The utilization of some form of effective prophylaxis against deep venous thrombosis after total hip replacement is essential because the operation is associated with a high risk of that complication and fatal pulmonary embolism^2,4,8. Effective means of prophylaxis include pharmacological anticoagulation therapy with warfarin^6,19 or low-molecular-weight heparin^1,6,9,13 and mechanical measures such as intermittent pneumatic compression of the thigh and calf^5,19 and of the plantar venous plexus³.

In a meta-analysis of fifty-six trials involving methods to prevent deep venous thrombosis in 8000 patients who had total hip replacement, Imperiale and Speroff found that the risk of proximal thrombosis was 5 per cent in patients who had been managed with warfarin and 6 per cent in patients who had been managed with low-molecular-weight heparin. Dextran, heparin, and intermittent pneumatic compression were also found to reduce the risk compared with the risk in the control groups, but aspirin was not effective⁷. Those authors concluded that low-molecular-weight heparin and intermittent pneumatic compression were both effective for the prevention of a pulmonary embolism, low-molecular-weight heparin was superior to all other methods for the prevention of proximal and distal thrombi, and low-molecular-weight heparin and warfarin were the most effective for protection from a proximal thrombus. Although warfarin and low-molecular-weight heparin were most effective for the prevention of a proximal thrombus, they were also associated with the highest risk of clinically important bleeding (1.3 per cent for warfarin and 1.8 per cent for low-molecular-weight heparin).

In an earlier randomized, prospective study of 217 patients, I found no significant difference (chi square, p = 0.8, beta = 0.20) in the prevalence of proximal deep venous thrombosis after total hip replacement when intermittent pneumatic compression had been used alone (12 per cent) or in combination with the oral administration of aspirin (10 per cent) or low-dose warfarin (9 per cent)¹⁹. On the basis of these findings, I concluded that the use of intermittent pneumatic compression alone was safe for patients who had no risk factors for the development of deep venous thrombosis other than the hip replacement itself. I also believed that it would be prudent to manage patients who were at a greater risk, because of a history of thrombosis or pulmonary embolism or another risk factor, with both intermittent pneumatic compression and low-dose warfarin, as the addition of low-dose warfarin had resulted in a slightly lower prevalence of proximal deep venous thrombosis than the use of intermittent pneumatic compression alone.

The purpose of the investigation was to determine the efficacy of prophylaxis with intermittent pneumatic compression, with or without low-dose warfarin, in reducing the prevalence of proximal deep venous thrombosis.

	Materials and Methods

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A prospective study was done on a consecutive series of 314 patients (353 hips), at least forty years old, who had a primary or revision total hip arthroplasty between October 1989 and January 1995. Patients who were known to have an additional risk factor for the development of a thrombus, such as a history of thromboembolic disease or varicose veins, were managed with intermittent pneumatic compression and low-dose warfarin. All other patients were managed with intermittent pneumatic compression alone.

Two hundred and eighty-nine patients (322 total hip arthroplasties) were managed with intermittent pneumatic compression alone, and twenty-nine were managed with intermittent pneumatic compression as well as low-dose warfarin. Four patients who were managed with intermittent pneumatic compression alone were managed with intermittent pneumatic compression as well as low-dose warfarin after a subsequent total hip replacement.

One hundred and fifty-eight women and 131 men were managed with intermittent pneumatic compression alone. The average age was sixty-six years (range, forty to ninety-three years), the average height was 169 centimeters (range, 135 to 196 centimeters), and the average weight was seventy-four kilograms (range, thirty-four to 145 kilograms). Of the 322 arthroplasties, 242 were primary replacements and eighty were revision procedures (nine for failure of an endoprosthesis and seventy-one for failure of the total hip replacement). One arthroplasty was performed with cement, 225 were so-called hybrid arthroplasties, and ninety-six were performed without cement. Thirty-one of the revision femoral components were inserted with cement and forty-nine, without cement. The preoperative diagnoses that led to the 242 primary procedures were osteoarthrosis (183 hips), osteonecrosis (twenty-four hips), acute fracture of the femoral neck (twelve hips), congenital dysplasia (six hips), rheumatoid arthritis (six hips), and miscellaneous conditions (eleven hips).

Eighteen women and eleven men were managed with intermittent pneumatic compression and low-dose warfarin. The average age was seventy-one years (range, fifty-two to ninety-three years), the average height was 167 centimeters (range, 127 to 193 centimeters), and the average weight was seventy-five kilograms (range, forty-six to 130 kilograms). Twenty primary and eleven revision procedures were done in these patients. Eighteen patients (nineteen hips) had a history of deep venous thrombosis or pulmonary embolism, and one patient (one hip) had large venous varicosities in the lower extremities. The risk factors in the other ten patients (eleven hips) included the performance of a contralateral total hip replacement one week before the index procedure or a bilateral one-stage total hip replacement (three patients [four hips]); congestive heart failure (two patients [two hips]); and prolonged immobilization preoperatively for an acute fracture of the femoral neck, a history of transient ischemic attacks, an intraoperative arterial injury, obesity, and advanced age (one patient [one hip] each).

I prefer the use of a regional anesthetic when medically feasible because of the excellent relief of postoperative pain that is afforded by the continuous epidural infusion of pain medication and because of previous reports that indicated a lower prevalence of deep venous thrombosis in patients who had been given a regional anesthetic^10-12,16,17. However, the final decision as to the type of anesthetic was made by the anesthesiologist after evaluation of the patient. A regional anesthetic was used in 233 of the 322 procedures performed in the patients who were managed with intermittent pneumatic compression alone. (Epidural anesthesia was used in 148 operations; epidural anesthesia in conjunction with general anesthesia, in sixty-four; and spinal anesthesia, in twenty-one.) A general anesthetic only was used during the remaining eighty-nine procedures. The patients who had regional anesthesia and those who had general anesthesia were similar with respect to age, height, weight, gender distribution, and the type of fixation used for the femoral component (Table I). A regional anesthetic was used during twenty-three of the thirty-one procedures performed in the patients who were managed with intermittent pneumatic compression and low-dose warfarin, and a general anesthetic was used during the other eight procedures.

Sequential compression was begun before the incision was made. The tubing from the sterile compression sleeve was attached to the drapes in such a way as to avoid contamination of the operative field by the unsterile tubing from the compression pump. Because of the modification of the thigh portion of the sterile sleeve, it did not extend over the incision in the hip unless a complex revision procedure required exposure of the middle or distal aspect of the femur. After the osteotomy of the femoral neck had been performed, great care was taken to avoid extreme internal rotation of the lower extremity for prolonged periods of time so as not to occlude venous return by torsion of the femoral vein, which occurs when the extremity is in this position. At the end of the procedure, the elastic stocking was pulled onto the thigh and a new, non-sterile thigh-high compression sleeve was placed on the limb.

A balanced suspension splint was used to elevate and stabilize the ipsilateral lower extremity above the level of the heart until the second postoperative day, at which time the patient began to walk. Sequential intermittent pneumatic compression was reinstituted in the recovery room and was continued throughout the hospital stay, except during physical therapy and when the patient bathed, until duplex ultrasonography was performed. The elastic stockings were worn all of the time except during bathing, and the patients were encouraged to continue to wear them for at least two weeks after discharge from the hospital or until there was no edema at the ankle.

Of the twenty-nine patients who were managed with adjunctive low-dose warfarin, twenty-eight were given the first dose (ten milligrams) on the night before the operation. The patient who had an intraoperative arterial injury was first given the warfarin on the day of the operation. For all patients, the daily dose was adjusted so that the prothrombin time was 1.2 to 1.3 times the control value or the international normalized ratio was between 2 and 3. The warfarin therapy was discontinued when the patient was discharged from the hospital, if no thrombi were detected by surveillance with ultrasound.

Surveillance testing for proximal deep venous thrombi was done on all patients before they were discharged from the hospital. Duplex ultrasonography was carried out on the involved limb only. The contralateral lower extremity was not examined with ultrasonography because in a previous study in which intermittent pneumatic compression was used bilaterally for prophylaxis after hip replacement, the prevalence of proximal thrombi in the contralateral lower extremity had been very low (one in 152 patients)²⁰. Ultrasonography was usually performed on the day before or the day of discharge (average, five days postoperatively; range, three to nine days postoperatively). The femoral and popliteal veins and the veins in the proximal portion of the calf were visualized. Complete compressibility of the veins was the main criterion for a negative examination. Venous Doppler signals (spontaneous, phasic, and augmented) were noted concurrently. In a previous prospective study of the accuracy of duplex ultrasonography for the detection of proximal deep venous thrombi, investigators at my institution found that ultrasonography had a sensitivity of 89 per cent and a specificity of 100 per cent compared with ascending venography²⁰.

	Results

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Intermittent Pneumatic Compression and Stockings Alone
Compliance by the patients with this form of prophylaxis was good. Proximal deep venous thrombosis was found, before the patient was discharged from the hospital, after twenty (6 per cent) of the 322 arthroplasties that had been done with intermittent pneumatic compression alone. One patient who had pain in the chest on the second postoperative day was evaluated with a ventilation-perfusion lung scan, and the scan indicated a low probability of pulmonary embolism. However, no other patient had clinical symptoms of an embolism.

A proximal thrombus was found after three (4 per cent) of the eighty revision arthroplasties and after seventeen (7 per cent) of the 242 primary hip replacements. The twenty patients who had a proximal thrombus were significantly older (average age, seventy-two years) than the remaining 269 patients (average age, sixty-five years) (p = 0.009). The prevalence of proximal deep venous thrombosis was 4 per cent (ten of 233 operations) for the patients who had had regional anesthesia, compared with 11 per cent (ten of eighty-nine operations) for the patients who had had general anesthesia; this difference was significant (p = 0.02).

Stepwise regression analysis with use of six variables (age, weight, operative time, type of anesthetic, gender, and type of arthroplasty [primary or revision]) was done to determine significant risk factors for the development of proximal deep venous thrombosis. Increasing age of the patient (p = 0.009) and general anesthesia (p = 0.03) were both significant risk factors. The prevalence was 3 per cent (eight of 245 procedures) for patients who were less than seventy-five years old, compared with 16 per cent (twelve of seventy-seven procedures) for patients who were seventy-five years old or more (p < 0.0001). When the factors of increased age and general anesthesia were combined, the risk of proximal deep venous thrombosis was very high. The prevalence was 26 per cent (six of twenty-three procedures) for patients who were seventy-five years old or more and had had general anesthesia, compared with 11 per cent (six of fifty-four procedures) for patients of the same age who had had regional anesthesia.

A wound hematoma developed in one patient, but it resolved without operative evacuation; only two units of blood was transfused during the patient's hospitalization. There were no other bleeding complications.

Three patients were diagnosed with proximal deep venous thrombosis after they had been discharged, despite normal findings on venous ultrasonography on the fourth or fifth postoperative day. These patients, all men, were forty-two, fifty-three, and fifty-five years old, and all had had a hip replacement without cement. Pain and swelling in the calf developed within two weeks after they had been discharged; repeat ultrasonography demonstrated a thrombus in the popliteal or femoral vein in the ipsilateral lower extremity, which may have been propagated by a thrombus in a calf vein. The three patients were managed with formal anticoagulation therapy consisting of heparin administered intravenously followed by long-term treatment with warfarin.

Intermittent Pneumatic Compression and Stockings with Low-Dose Warfarin
The prevalence of proximal deep venous thrombosis was 19 per cent (six of thirty-one procedures) for the twenty-nine patients who had had prophylaxis with intermittent pneumatic compression and low-dose warfarin. No patient had clinical symptoms of a pulmonary embolism. The prevalence of proximal deep venous thrombosis was two of eight procedures for patients who had had general anesthesia, compared with 17 per cent (four of twenty-three procedures) for patients who had had regional anesthesia. The average age of the six patients who had deep venous thrombosis was not significantly different from the average age of those who did not (seventy-one compared with seventy-two years).

	Discussion

Top Abstract Introduction Materials and Methods Results Discussion References

 
In the present study, the prevalence of proximal deep venous thrombosis after total hip replacement was 6 per cent for a consecutive series of patients who were managed with the intraoperative and postoperative use of intermittent pneumatic compression and elastic stockings alone. The presence of thrombi was determined by duplex ultrasonography, performed on the involved limb an average of five days postoperatively. This prevalence was low and compares favorably with the findings for large series of patients who were managed with low-molecular-weight heparin or warfarin.

In a multicenter study, Colwell et al. found a 4 per cent prevalence of proximal thrombosis in 272 patients who had been managed with two different doses of low-molecular-weight heparin (enoxaparin). Hull et al.⁶ and Levine et al. both reported a 5 per cent prevalence of proximal thrombosis, in 332 patients who had been managed with logiparin and in 258 patients who had been managed with enoxaparin, respectively. In studies of low-dose warfarin, Hull et al.⁶ found a 4 per cent prevalence of proximal thrombosis in 340 patients, and the RD Heparin Arthroplasty Group reported a 6 per cent prevalence in 174 patients. In all of these studies of the efficacy of low-molecular-weight heparin and warfarin, the thrombi were identified with bilateral ascending venography that was performed once between the seventh and fourteenth days postoperatively. The prevalence of proximal thrombosis in the current study might have been greater than 6 per cent if testing had been done later than an average of five days postoperatively, but I could not justify a longer hospital stay for these patients.

Although the efficacy of low-molecular-weight heparin and warfarin is excellent, the bleeding complications associated with these anticoagulants are not inconsequential. In the three studies of low-molecular-weight heparin just mentioned^1,6,9, the prevalence of major bleeding complications was 2.8 to 4 per cent, despite the fact that the initial dose of heparin was not administered until twelve to twenty-four hours postoperatively. In the two studies of low-dose warfarin^6,13, a major bleeding complication occurred in 1.5 and 5 per cent of the patients, despite the maintenance of an international normalized ratio of 2 to 3 or a prothrombin time that was 1.2 to 1.5 times the control value. In the current series of 322 total hip arthroplasties, intermittent pneumatic compression resulted in no instances of major bleeding as defined in these other studies.

This study was performed to investigate a mechanical method of prophylaxis for deep venous thrombosis; namely, intermittent pneumatic compression and elastic stockings. However, I believe that other factors in the management of these patients should be mentioned because they may have contributed to the low prevalence of proximal thrombosis. Two of these factors were related to the operative technique itself. First, the intermittent pneumatic compression was begun intraoperatively for all patients with the use of a sterile compression sleeve. Intraoperative prophylaxis against thrombosis was shown to be highly effective in a study by Sharrock et al., in which sixty patients (sixty total hip arthroplasties) were managed with intraoperative administration of heparin and adjunctive epidural anesthesia with controlled hypotension and oral administration of aspirin postoperatively. Those authors reported an extremely low prevalence of proximal thrombosis (2 per cent), according to findings on venography performed on the seventh postoperative day. From the results of that study, one may infer that a high proportion of isolated femoral thrombi identified after total hip replacement developed intraoperatively. An advantage of prophylaxis with intermittent pneumatic compression is that it may be initiated intraoperatively; the intraoperative use of low-molecular-weight heparin is not recommended by its manufacturers, and warfarin is difficult to use intraoperatively. The second factor related to the operative technique was the avoidance of prolonged intervals of extreme internal rotation of the lower extremity during preparation of the femoral canal and insertion of the prosthesis; this reduced the length of time that the femoral vein was kinked. Stamatakis et al. postulated that isolated thrombi in the femoral vein, which frequently occur after total hip replacement, are produced by this mechanism. Those investigators performed intraoperative venography and found that the common femoral vein becomes occluded during extreme rotation at the hip during either a posterior or a transtrochanteric approach. This finding was also corroborated by the results of intraoperative Doppler studies performed by my colleagues and me²¹. Blood flowed through the kinked common femoral vein during external pneumatic compression of the calf and thigh by the sterile compression sleeve.

Postoperatively, all of the patients in the present study had elevation of the limb with use of a balanced suspension splint for the initial forty-eight hours postoperatively. This greatly increases the venous return in the lower extremity in patients who are confined to bed. During the first two postoperative days, there was complete compliance by all patients with regard to wearing the compression sleeves and elastic stockings. This resulted in additional protection against venous stasis in both the veins in the calf and the proximal veins.

In the current study, the prevalence of proximal thrombosis was significantly decreased (p = 0.02) for patients who had had regional anesthesia, compared with those who had had general anesthesia, although the type of anesthesia was not randomly assigned. Regional anesthesia lowered the risk of thrombosis by a factor of almost three. Numerous other studies have also shown that regional anesthesia reduces the risk of venous thrombosis in patients who have not had prophylaxis with anticoagulants^10-12,16,17.

A late-occurring symptomatic proximal thrombus was found in 1 per cent (three) of the 289 patients, and I believe that these thrombi were most likely caused by the proximal propagation of a thrombus in a calf vein that was present after the operation but not detected by ultrasonography. Although this was a small percentage, one must be diligent with regard to performing objective testing when pain in the calf develops after total hip replacement in patients who have had no, or a negative result on, testing of the proximal veins. None of the patients in the current study, however, had symptoms of a pulmonary embolism after they had been discharged from the hospital.

The greater prevalence of proximal thrombosis was not unexpected in the small group of patients who were managed with both intermittent pneumatic compression and low-dose warfarin because they had additional risk factors for thrombosis. This prevalence might have been greater if the combination of prophylactic measures had not been used, and the use of low-dose warfarin should not be considered a failure on the basis of these results. To my knowledge, no other studies of patients who had total hip replacement and were at additional risk because of a history of deep venous thrombosis are available for comparison with the present study. I believe that the use of low-dose warfarin is indicated for patients who are at additional risk, because if a thrombus is detected during the hospital stay of a patient who has been managed with perioperative low-dose warfarin and who has a prothrombin time that is within the therapeutic range, the discharge need not be delayed if the thrombus is not extensive or life-threatening from a standpoint of embolization¹⁸.

Because there is a small risk (6 per cent) that a proximal deep venous thrombus will develop, and because intermittent pneumatic compression cannot be continued on an outpatient basis, patients who are managed with this form of prophylaxis without adjunctive outpatient anticoagulation should have surveillance testing for deep venous thrombosis before discharge from the hospital. As most studies of the use of prophylactic intermittent pneumatic compression have demonstrated a low risk of a thrombus in the contralateral lower extremity, testing of only the involved limb is probably safe, and venous ultrasonography with the duplex technique is preferred not only because of its low cost but also because of its reportedly high sensitivity and specificity compared with venography²⁰.

This study clearly indicates that intermittent pneumatic compression should be combined with regional anesthesia in order to maximize its efficacy. This combination provided a safe, highly effective means of protection from proximal deep venous thrombosis and clinical pulmonary embolism in a large prospective series of patients who had a total hip arthroplasty. In fact, the prevalence of proximal deep venous thrombosis in this series was as low as that reported for patients who were managed with either warfarin or low-molecular-weight heparin. Because there is no risk of bleeding complications associated with mechanical prophylaxis, it is safer than warfarin and heparin, which have been shown to cause major bleeding complications in 1.5 to 4 per cent of patients who have had a hip replacement^6,13.

	Footnotes

 
*No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article. No funds were received in support of this study.

1220 University Drive, Suite 202, Menlo Park, California 94025.

	References

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