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Cochrane Database of Systematic Reviews Protocol - Intervention

Anticoagulation for thrombotic prophylaxis in knee arthroscopy

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Abstract

This is a protocol for a Cochrane Review (Intervention). The objectives are as follows:

To asses the effectiveness and safety of thromboprophylaxis to reduce the incidence of deep vein thrombosis (DVT) in patients undergoing knee arthroscopy.

Background

Deep venous thrombosis (DVT) occurs when a blood clot develops within the venous system, typically in the lower limbs. The characteristic symptoms are limb pain and edema but often DVT is asymptomatic. The risk of developing DVT depends on multiple factors including a previous history of DVT, immobilization, increasing age, surgery, trauma, and any hypercoagulable state. Deep vein thrombosis of the deep calf veins is referred to as distal thrombosis; thrombosis at, or above the popliteal vein is considered to be proximal DVT. Distal DVT becomes important if it extends proximally (up to 28%) (Kearon 2003), and can increase the chance of developing pulmonary embolism (PE) (up to 56 %) (Hollerwerger 2000). Ten per cent of symptomatic pulmonary embolisms may be fatal (Kearon 2003). Other complications of DVT include the risk of developing pulmonary hypertension (cumulative incidence 3.8 % at two years) (Pengo 2004); post‐thrombotic syndrome (PTS) (20% to 50 %) (Kahn 2002) characterized by chronic persistent pain, swelling, and other signs in the affected limb; increased risk of recurrent venous thromboembolism; and venous ulcers (5% to 10%) (Kahn 2002).

Clinical diagnosis of DVT may be difficult in the absence of symptoms and consequently it is often under diagnosed (50 % of DVT cases are symptomatic) (Delis 2001). The clinical significance of those who are not diagnosed remains unknown. Sonography is used as a diagnostic method with moderate sensitivity and specificity for DVT. Phlebography is the gold standard diagnostic method for DVT. It has good specificity and sensitivity, but it is difficult to justify its use as a screening method in a low risk population.

Orthopedic surgery increases the risk of deep venous thrombosis. Knee arthroscopy is a frequently performed surgical procedure in orthopedics, traditionally carried out on a young population, but this indication is now extending to older patients. Arthroscopically‐assisted surgery may be used for the treatment of a variety of pathologies with different technical requirements for example, washout, meniscectomy (removal of cartilage from the knee joint), anterior/posterior cruciate ligament repairment, lateral release, chondroplasty (repair of cartilage), articular debridement (removal of dead or infected material), synovial resection, and tibial plateau fractures. Some of these may be considered minimally‐invasive procedures; other procedures necessitate tourniquet use, extended surgical time, and cause more soft tissue and bone damage. General anesthesia, subarachnoid blockade, femoral blockade, intrarticular or combined anesthesia may be performed, each carrying independent risks.

The incidence of DVT in patients who undergo venographically‐screened, knee arthroscopy, is reported to be as high as 17.9% (Demers 1998). Nevertheless, some studies report an incidence of clinically diagnosed DVT of 0.6 % (Dahl 2000). When ultrasound is performed, other studies report an incidence of 4.1% (Wirth 2001), and 15.6 % (Michot 2002).

Surgeons agree that thromboprophylaxis should be use in moderate and high risk patients who undergo surgery. Graduated elastic stockings and intermittent pneumatic compression are mechanical devices used to prevent DVT, the latter often used in patients immobilized in bed. There are different opinions about what pharmacologic prophylaxis should be used in knee arthroscopy, depending on the incidence in each trial.

Objectives

To asses the effectiveness and safety of thromboprophylaxis to reduce the incidence of deep vein thrombosis (DVT) in patients undergoing knee arthroscopy.

Methods

Criteria for considering studies for this review

Types of studies

Randomized clinical trials (RCTs) and controlled clinical trials (CCTs), whether blinded or not (i.e. double blinded, single blinded or unblinded).

Types of participants

Males and females over 18 years old undergoing knee arthroscopy. Trials of arthroscopic‐assisted osteosynthesis of tibial plateau fractures will be excluded.

Types of interventions

All type of interventions, whether mechanical or pharmacological, single or in combination, used to prevent DVT in patients undergoing knee arthroscopy.

Types of outcome measures

Primary outcome

  • proximal and distal DVT events diagnosed by venography or sonography;

  • pulmonary embolism diagnosed by V/Q lung scan, spiral computed tomography (CT), or pulmonary angiography;

  • death related to embolic events.

Secondary outcomes

  • reported side/adverse effects;

  • death;

  • major bleeding (overt and associated with requiring transfusion of red blood cells or surgical interventions, and which may lead to permanent disability);

  • minor bleeding (did not meet the above major criteria for intervention for example, hematoma, hemarthrosis, thrombocytopenia (reduction of circulating platelets) of < 80000/mm3 or decrease > 50% of the initial count).

Search methods for identification of studies

All publications describing (or which might describe) RCTs or CCTs of mechanical or pharmacological interventions used to prevent DVT in patients undergoing knee arthroscopy will be sought through the Cochrane Peripheral Vascular Diseases Group Specialized Register. The Peripheral Vascular Diseases Group Register contains citations of trials identified through electronic searches of MEDLINE (1966 to date) and EMBASE (1980 to date), and through handsearching journals and conference proceedings. The full list of journals that have been handsearched, as well as the search strategies for the electronic databases, are described in the 'Search strategies for the identification of studies' section within the editorial information about the Cochrane PVD Group in The Cochrane Library.

We shall also search the following electronic databases according to the methods described in the Cochrane Collaboration Handbook:

(1) the Cochrane Central Register of Controlled Trials (CENTRAL);
(2) MEDLINE from 1966 to date using the search terms "thombotic "[in all fields] AND arthro* [in all fields] AND prophy* [in all fields] OR preven* [in all fields], AND Hepar*`[in all fields] or Low Molecular Heparin[in all fields] combined with the MEDLINE search strategies for randomized controlled trials suggested by the Cochrane Collaboration Handbook;
(3) EMBASE from 1980 to date using similar search strategy;
(4) Lilacs from 1988 to date.

In addition, we shall search the reference list of identified studies, and articles and abstracts of international meetings of Orthopedics, Hematology & Thrombosis journals from the year 1998 to 2004. We intend to contact specialists known to be involved in phlebology and interested in post‐thrombotic syndrome for details of unpublished and ongoing trials. There will be no restriction on language.

Data collection and analysis

Study Selection
J Ramos and G Badariotti will independently screen the initial results of all the databases and references lists to identify citations which seem relevant to our review. Once identified, the citations and abstracts will be checked and, if the inclusion criteria are met, the full text articles will be obtained. Both authors will decide independently on trial inclusion using a standard form. Disagreement will be resolved by consensus.

Quality assessment
J Ramos and G Badariotti will evaluate each trial. The assessment of quality will include:

(1) The quality of allocation concealment categories:
Category A: adequate concealment
Category B: uncertain, indication of adequate
Category C: inadequate concealment

(2) Blinding: we will evaluate if investigators, participants, outcome assessor and data analysts were blinded to the treatment status. For each one we will comment as yes, no, or not stated.

(3) Intention‐to‐treat analysis: we will specify if the analysis was done on an intention‐to‐treat basis (specifically reported by the authors, or confirmed after reading the paper), or if the analysis was done without intention‐to‐treat analysis, or if it was unclear in the article.

(4) Completeness of follow up: we will check the number of participants with data against the number of participants randomized, expressed as a percentage overall, and in each intervention group.

(5) Outcomes definition : we will evaluate how the authors defined DVT and the way in which adverse events were recalled. Differences in outcomes assessment will be taken into account during the analysis, particularly if we find heterogeneity between the trials.

(6) If studies differ considerably by quality, a sensitivity analysis that excludes the low quality studies will be performed.

Data extraction
J Ramos and G Badariotti will extract data independently. Disagreements will be resolved by discussion and when necessary, additional information will be sought from authors of relevant articles.

Data analysis
Dichotomous outcomes will be analysed as relative risks and their 95% confidence intervals recorded. Continuous variables will be analysed using mean differences with 95% confidence interval. The results will be combined using a random‐effects model to assess overall treatment effects. A test of heterogeneity will be performed to assess potential differences between trials. Differences in outcomes assessment will be taken into account to explain for heterogeneity. Sensitivity analysis, will be done to assess whether any individual study excessively influences the analyses.