- How do we determine risk of venous thromboembolism (VTE) in patients scheduled for surgery?
- Do all surgical patients require VTE prevention?
- Is aspirin adequate to prevent VTE in low-risk hospitalized patients?
- Which anticoagulant is appropriate for a patient scheduled for total knee replacement?
These important questions are answered in a guideline developed by a committee of the American College of Chest Physicians, which considered the following prophylaxis recommendations: early ambulation, aspirin, graduated compression stockings, intermittent pneumatic compression, low-dose unfractionated heparin, low-molecular-weight heparin, or oral antithrombotic agents.
The committee categorized recommendations by type of surgical procedure and risk status. In this summary, the recommendations are reorganized by strength of recommendation.
Three outcomes were regarded:
- Efficacy of various prophylactic strategies
- Rates and relative risk of venous thromboembolism outcomes—ie, fatal pulmonary embolism, symptomatic deep vein thrombosis, pulmonary embolism, or asymptomatic proximal deep vein thrombosis
- Cost-effectiveness of prophylaxis.
The committee used a rating scheme that accounted for both the risk/benefit ratio (clear or unclear) and the strength of the supporting recommendation (A, B, C). The grades of evidence were altered to correspond to the grades of recommendation of the Oxford Centre for Evidence-Based Medicine. (For an explanaton of these grades.)
Relevant recommendations
This guideline is clinically relevant because of the high mortality associated with pulmonary embolus complicating VTE.
It offers a practical, tabulated guide, listed by surgical procedure performed. It is pertinent to hospitalized patients under the care of family physicians. The rationale for each recommendation is clear and well supported by the referenced literature. The objectives of the guideline were met and the outcome measures were appropriate.
The guideline is weakened by the lack of cost-effectiveness considerations.
Determining surgical risk
| Surgery + | Patient age (yr) + | Risk factors = | Level of risk |
|---|---|---|---|
| Minor | < 40 | No | Low |
| Minor | Any | Yes* | Moderate |
| 40–60 | No | ||
| Major | < 40 | No | |
| Minor | > 60 | No | High |
| > 60 | Yes* | ||
| Major | > 40 | No | |
| > 40 | Yes* | ||
| Major | > 40 | Prior VTE, cancer, hypercoagulable states, hip/knee arthoplasty, hip fracture, major trauma, spinal injury | Very high |
*Additional risk factors: immobility, stroke, paralysis, trauma, obesity, varicose veins, cardiac dysfunction, indwelling central venous catheter, inflammatory bowel disease, nephrotic syndrome, pregnancy, estrogen use, congenital thrombophilic abnormalities
- For all risk groups of patients, aspirin is not recommended for prophylaxis (strength of recommendation [SOR]: A)
- Every hospital should have an appropriate thromboembolic event prevention strategy, determined by proper risk assessment (SOR: D)
- Antithrombotics should be used with caution before invasive spinal or epidural procedures (SOR: C)
Grade A Recommendations
- Low-dose unfractionated heparin (LDUH), low-molecular-weight heparin (LMWH), graduated compression stockings (GCS), or intermittent pneumatic compression (IPC) for moderate-risk surgery patients
- LDUH, LMWH, or IPC for higher-risk general surgery
- Twice-daily LDUH for major gynecological surgery for benign disease
- Three-times-daily dose LDUH for gynecological surgery for malignancy
- LMWH or warfarin for 7–10 days for total hip or total knee replacement surgery; continue for longer periods in higher-risk patients. Adjusted-dose intravenous heparin is an acceptable alternative, but more difficult to manage
- Aspirin alone is not acceptable for hip fracture patients
- IPC with GCS for intracranial surgery; LDUH or postoperative LMWH are acceptable alternatives
- LMWH or intravenous heparin for the acute myocardial infarction patient (for the VTE prevention indication)
- LDUH or LMWH for immobilized stroke patient. GCS if anticoagula tion is contraindicated
- LDUH or LMWH for medical patients with cancer, bedrest, congestive heart failure, or severe lung disease
Grade B Recommendations
- LDUH, GCF, IPC, or LMWH for open urologic procedures
- IPC for total knee replacement
- LMWH or warfarin for hip fracture; an alternative is IPC
- LMWH for acute spinal cord injury. Alternative GCS or IPC in combination with LMWH or LDUH, if LMWH is contraindicated
Grade C Recommendations
- Early ambulation (with no antithrombotic agents) for low-risk surgery patients or uncomplicated gynecologic procedures
- LDUH, LMWH, or IPC for higher-risk surgery patients
- For very-high-risk surgery patients, LDUH or LMWH combined with GCS or IPC.Some patients may benefit from post-hospital LMWH or warfarin
- Daily LDUH or IPC for major gynecologic procedures for benign disease
- LDUH plus GCS or LMWH for gynecologic surgery for malignancy
- Early ambulation for low risk urologic and gynecologic procedures
- High-risk urologic procedures GCS plus with LDUH or LMWH
- GCS or IPC added to antithrombotic drugs for total hip replacement
Guideline development and evidence review
Literature searches were performed for each patient group. Criteria for inclusion included relevant patient group, sample size of at least 10 patients per group, verified deep vein thrombosis, and patients with adequate outcome assessments.
In considering baseline risk of thrombosis, only either prospective cohort studies or control groups of randomized trials were considered. For prophylaxis efficacy recommendations, only randomized trials were considered. The consensus group analyzed data from 630 sources before making these recommendations.
Sources for this guideline
Sixth ACCP Consensus Conference on Antithrombotic Therapy
The Consensus Conference guidelines can be found at:
Geerts WH, et al. Prevention of thromboembolism. Chest 2001; 119:132S–175S. Available at: www.chestjournal.org/content/vol119/1_suppl/index. shtml. Accessed on December 16, 2003.