Interventions for preventing venous thromboembolism following abdominal aortic surgery

Perioperative antithrombotic therapy does not increase the incidence of early postoperative thromboembolic complications and bleeding in kidney transplantation - a retrospective study

Perioperative antithrombotic therapy could play a role in preventing thromboembolic complications (TEC) after kidney transplantation (KTx), but little is known on postoperative bleeding risks. This retrospective analysis comprises 2000 single‐organ KTx recipients transplanted between 2011 and 2016 in the two largest transplant centers of the Netherlands. TEC and bleeding events were scored ≤7 days post‐KTx. Primary analyses were for associations of antithrombotic therapy with incidence of TEC and bleeding. Secondary analyses were for associations of other potential risk factors. Mean age was 55 ± 14 years, 59% was male and 60% received a living donor kidney. Twenty‐one patients (1.1%) had a TEC. Multiple donor arteries [OR 2.79 (1.15–6.79)] and obesity [OR 2.85 (1.19–6.82)] were identified as potential risk factors for TEC. Bleeding occurred in 88 patients (4.4%) and incidence varied significantly between different antithrombotic therapies (P = 0.006). Cardiovascular disease [OR 2.01 (1.18–3.42)], pre‐emptive KTx [OR 2.23 (1.28–3.89)], postoperative heparin infusion [OR 1.69 (1.00–2.85)], and vitamin K antagonists [OR 6.60 (2.95–14.77)] were associated with an increased bleeding risk. Intraoperative heparin and antiplatelet therapy were not associated with increased bleeding risk. These regimens appear to be safe for the possible prevention of TEC without increasing the risk for bleeding after KTx.

Primary prophylaxis for venous thromboembolism in patients undergoing cardiac or thoracic surgery

BACKGROUND

Cardiac and thoracic surgery are associated with an increased risk of venous thromboembolism (VTE). The safety and efficacy of primary thromboprophylaxis in patients undergoing these types of surgery is uncertain.

OBJECTIVES

To assess the effects of primary thromboprophylaxis on the incidence of symptomatic VTE and major bleeding in patients undergoing cardiac or thoracic surgery.

SEARCH METHODS

The Cochrane Peripheral Vascular Diseases Group Trials Search Co-ordinator searched the Specialised Register (last searched May 2014) and CENTRAL (2014, Issue 4). The authors searched the reference lists of relevant studies, conference proceedings, and clinical trial registries.

SELECTION CRITERIA

Randomised controlled trials (RCTs) and quasi-RCTs comparing any oral or parenteral anticoagulant or mechanical intervention to no intervention or placebo, or comparing two different anticoagulants.

DATA COLLECTION AND ANALYSIS

We extracted data on methodological quality, participant characteristics, interventions, and outcomes including symptomatic VTE and major bleeding as the primary effectiveness and safety outcomes, respectively.

MAIN RESULTS

We identified 12 RCTs and one quasi-RCT (6923 participants), six for cardiac surgery (3359 participants) and seven for thoracic surgery (3564 participants). No study evaluated fondaparinux, the new oral direct thrombin, direct factor Xa inhibitors, or caval filters. All studies had major study design flaws and most lacked a placebo or no treatment control group. We typically graded the quality of the overall body of evidence for the various outcomes and comparisons as low, due to imprecise estimates of effect and risk of bias. We could not pool data because of the different comparisons and the lack of data. In cardiac surgery, 71 symptomatic VTEs occurred in 3040 participants from four studies. In a study of 2551 participants, representing 85% of the review population in cardiac surgery, the combination of unfractionated heparin with pneumatic compression stockings was associated with a 61% reduction of symptomatic VTE compared to unfractionated heparin alone (1.5% versus 4.0%; risk ratio (RR) 0.39; 95% confidence interval (CI) 0.23 to 0.64). Major bleeding was only reported in one study, which found a higher incidence with vitamin K antagonists compared to platelet inhibitors (11.3% versus 1.6%, RR 7.06; 95% CI 1.64 to 30.40). In thoracic surgery, 15 symptomatic VTEs occurred in 2890 participants from six studies. In the largest study evaluating unfractionated heparin versus an inactive control the rates of symptomatic VTE were 0.7% versus 0%, respectively, giving a RR of 6.71 (95% CI 0.40 to 112.65). There was insufficient evidence to determine if there was a difference in the risk of major bleeding from two studies evaluating fixed-dose versus weight-adjusted low molecular weight heparin (2.7% versus 8.1%, RR 0.33; 95% CI 0.07 to 1.60) and unfractionated heparin versus low molecular weight heparin (6% and 4%, RR 1.50; 95% CI 0.26 to 8.60).

AUTHORS' CONCLUSIONS

The evidence regarding the efficacy and safety of thromboprophylaxis in cardiac and thoracic surgery is limited. Data for important outcomes such as pulmonary embolism or major bleeding were often lacking. Given the uncertainties around the benefit-to-risk balance, no conclusions can be drawn and a case-by-case risk evaluation of VTE and bleeding remains preferable.

A systematic review of Cochrane anticoagulation reviews

CONTEXT

I coauthored a published review of anticoagulation for venous thromboembolism in the Cochrane Database of Systematic Reviews and published a review on the same topic in MedGenMed (now the Medscape Journal of Medicine). In contrast to the article in Medscape, the discussion and conclusions in the Cochrane review were altered appreciably during the review process. Consequently, I decided to critique all anticoagulation drug-related reviews and protocols in the Cochrane database with feedback letters concerning any issues of potential controversy.

EVIDENCE ACQUISITION

Using key words in the search engine of the Cochrane Reviews, I located reviews and protocols involving anticoagulant drugs. I critiqued each anticoagulation review and protocol and sent a total of 57 feedback letters to Cochrane concerning each publication to elicit a response/rebuttal from the authors.

EVIDENCE SYNTHESIS

Cochrane anticoagulation review editors acknowledged receipt of all letters. As of 12 months after receipt of my last letter, the Cochrane authors have replied to 13 of the 57 and agreed with many of my points. Two protocols were withdrawn after my feedback letters were acknowledged. The 58 Cochrane anticoagulation drug reviews, including mine, contained 9 categories of methodological errors (207 total instances) and 4 types of biases (18 total instances). This review of those Cochrane reviews suggests that the effectiveness of anticoagulants for 30 medical indications is questionable.

CONCLUSIONS

The efficacy of anticoagulants for treatment and prophylaxis for 30 current medical indications should be reconsidered by the scientific community and medical regulatory agencies. At least 50,000 people per year worldwide have fatal bleeding due to anticoagulant treatment or prophylaxis for these indications.