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  • 2019-04
  • br Perioperative risk assessment of thromboembolism The curr

    2019-04-15


    Perioperative risk assessment of thromboembolism The current thromboembolic risk stratification is largely based on indirect evidence from studies outside of the perioperative setting involving patients with a mechanical substance p valve, chronic atrial fibrillation or venous thromboembolism who either did not receive anticoagulation ( i.e., placebo-treated group in atrial fibrillation trials) or received less-effective treatment (e.g., aspirin-treated group in mechanical heart valve trials) [2]. Table 1 is a simplified risk stratification scheme for perioperative thromboembolism. Patients are classified as high risk (annual risk>10%), moderate risk (annual risk 5% to 10%), and low risk (annual risk<5%) for thromboembolism. An estimate of individual patient risk for perioperative thromboembolism is subjective but should consider both the baseline risk and the individual patient factors. For patients who are already on chronic warfarin therapy, most of them should have been considered by their physicians as moderate to high risk for thromboembolism.
    Current management options
    Risk of thromboembolism with short-term interruption of warfarin therapy A systematic review of perioperative anticoagulation suggested that risk of stroke for patients in whom warfarin was withheld might be substantially higher than would be predicted based on annual thromboembolic rates of patients with atrial fibrillation or a mechanical heart valve [5]. In a prospective, observational cohort study, 1293 episodes of warfarin therapy interruption in 1024 patients for an outpatient invasive procedure were included [6]. Warfarin therapy was withheld for ≤5 days in 83.8% of the episodes. Seven patients (0.7%) experienced postprocedural thromboembolic events. All those patients with arterial events were in atrial fibrillation with CHADS2 score of ≥2. In our study, 114 patients on chronic warfarin therapy had anticoagulation temporarily interrupted for CIED surgery without bridging therapy. Among them, 4 patients with atrial fibrillation and CHADS score ≥3 experienced a transient ischemic attack (TIA) even though these patients continued to receive aspirin [7]. Although it is generally safe for low risk patients, a short period of interruption of warfarin therapy during the periprocedural period in patients with moderate to high risk factors could potentially expose them to a small, but real thromboembolic threat.
    Risk of pocket hematoma on bridging therapy with heparin or LMWH A substantial risk of pocket hematoma related to bridging therapy with therapeutic dose of heparin or LMWH has been consistently observed in patients undergoing device surgery. In a retrospective cohort study, Wiegand et al. reported that patients who received bridging therapy, with a therapeutic dose of heparin, had a higher incidence of pocket hematoma as compared to the group who did not receive such treatment (10.7% vs. 2.9%; p<0.001) [8]. In a randomized trial, Michaud et al. demonstrated up to 10-fold greater risk of pocket hematoma after device implantation in patients who received intravenous heparin than in patients who did not receive such therapy [9]. The risk was similar whether heparin therapy was initiated 6h or 24h after surgery. Marquie et al. confirmed that the postoperative use of heparin of any type conferred a 14-fold increased risk for pocket hematoma [10]. Similar findings were reported by us and other authors [7,11]. Robinson et al. showed that omission of LMWH the night before procedure did not reduce hematoma rates, but omission of postoperative LMWH dramatically reduced the occurrence of hematoma [12]. Several studies also demonstrated that bridging therapy is associated with a longer hospital stay after the procedure [7,13,14]. This finding is expected, as a patient on bridging therapy with intravenous heparin must be kept in the hospital until their INR reaches the therapeutic range. Although subcutaneous LMWH could be self-administered, many of these patients were unable to do so and required transfer to a transitional facility. In addition, patients who developed a pocket hematoma stayed in the hospital longer for observation, transfusion, or surgical evacuation [15]. More importantly. the development of pocket hematoma often lead to withhold anticoagulation therapy for a prolonged time and thus potentially increase the risk for thromboembolism in these patients.