Fear of major bleeding complications is unsubstantiated. There is ample evidence from placebo-controlled, blinded trials and meta-analysis that the risk of clinically important bleeding does not increase. Moreover, detailed analysis demonstrates that low-dose heparin has a good risk-to-benefit ratio and is cost-effective.
Low-molecular-weight heparins
These drugs are fragments of unfractionated heparin that vary in size from 4,500 to 6,500 daltons. Low-molecular-weight heparin (LMWH) has more anti-Xa and less antithrombin activity than unfractionated heparin and thus has less of an effect on partial thromboplastin time. LMWH may also lead to fewer bleeding complications.7
Once-daily dosing is possible. An increased half-life of 4 hours for LMWH produces greater bioavailability than with low-dose heparin. This allows once-daily dosing.
Pick one: Convenience or cost
Randomized controlled trials have compared LMWH to unfractionated heparin in gynecologic surgical patients. In all studies, DVT occurred in similar, low numbers of women regardless of the heparin used. Bleeding complications also were similar.8
A meta-analysis of general surgery and gynecologic surgery patients from 32 trials likewise found daily LMWH to be as effective as unfractionated heparin in DVT prophylaxis, without any difference in hemorrhagic complications.9
The choice of drugs often boils down to convenience versus cost: Prophylactic LMWH can be given once a day (compared with 2 or 3 times for unfractionated heparin), but is much more expensive.
Mechanical prophylactic methods
External pneumatic compression rivals low-dose heparin. The largest body of literature on mechanical methods to reduce postoperative venous stasis involves intermittent leg compression by pneumatically inflated sleeves placed around the calf or leg during surgery and after. A number of devices and sleeve designs are available, none of which has proven to be superior to the others.
In my experience, calf compression during and after gynecologic surgery lowers the incidence of DVT to a level seen with low-dose heparin. Besides increasing venous flow and pulsatile emptying of the calf veins, pneumatic compression appears to augment endogenous fibrinolysis, which may stimulate lysis of very early thrombi.10
How long is best for external compression? The optimal duration of postoperative external pneumatic compression is unclear. It may be effective when used in the operating room and for the first 24 hours postoperatively in patients with benign conditions who will ambulate on the first day after surgery.11,12
In women undergoing major surgery for gynecologic malignancy, it reduces the incidence of postoperative venous thromboemboli by nearly 3-fold, but only if calf compression is applied intraoperatively and for the first 5 postoperative days.13,14 These women may remain at risk because of stasis and a hypercoagulable state for a longer time than general surgical patients.
External pneumatic leg compression has no serious side effects or risks and is slightly more cost-effective than prophylactic drugs.15 However, to be fully effective, this method must be used consistently, in compliance with the protocol, when the patient is not ambulating.
Stockings can be a help or hazard. Controlled studies of graduated pressure stockings are limited but suggest modest benefit with careful fitting.16 Poorly fitted stockings that roll down the leg may create a tourniquet effect at the knee or mid-thigh. Another disadvantage of the stockings: The limited sizes available do not allow a perfect fit for all patients. This is especially true in obese patients.
The simplicity of elastic stockings and the absence of serious side effects are probably why stockings are often included in routine postoperative care.
Don’t overlook basic precautions. Although they may offer only modest benefit, short preoperative hospital stays and early postoperative ambulation are recommended.
Another basic strategy: elevating the foot of the bed to raise the calf above heart level. This allows gravity to drain the calf veins and should further reduce stasis.
How to detect VTE
DVT has nonspecific signs and symptoms
When DVT occurs in the lower extremities, harbingers such as pain, edema, and erythema are relatively nonspecific; 50% to 80% of patients exhibiting them do not have DVT. Conversely, approximately 80% of patients with symptomatic pulmonary emboli have no signs or symptoms of thrombosis in the lower extremities.
Because of this lack of specificity, additional tests are needed to establish DVT.
Diagnostic studies
A definitive diagnosis of DVT and pulmonary embolism is mandatory because diagnosis based on clinical symptoms and signs alone is frequently wrong. Strategies to reduce the use of ultrasound or spiral CT scanning have been put forward. These studies have evaluated outpatients using algorithms that utilize clinical probability (“clinical decision rule”) and D-dimer levels.
This strategy has been very accurate and avoids the use of ultrasound or spiral CT in low-risk patients. For example, individuals with a low probability score have an incidence of DVT below 5%, so ultrasound is unnecessary. This diagnostic strategy relies on the recognition of elevated D-dimer levels. Unfortunately, D-dimer is increased by a variety of nonthrombotic disorders, including recent surgery, hemorrhage, trauma, pregnancy, and cancer. Therefore, we cannot recommend the use of this strategy for the postoperative gynecologic surgery patient.17,18