[雙語翻譯]醫(yī)學(xué)外文翻譯--下肢深靜脈血栓和肺栓塞的預(yù)防（英文）

1、Prevention of deep vein thrombosis and pulmonary embolusTom MartinCaroline OliverAbstractVenous thromboembolism is common in the perioperative period. Difficul-ties with diagnosis and the risks of treatment make preventi

2、on a clinicalimperative. Preoperative risk assessment and appropriate prophylaxis isimportant to minimize morbidity and mortality. A range of mechanicaland pharmacological interventions have been shown to significantly r

3、educethe risk. A number of anaesthetic interventions are also recommended.Newer oral anticoagulants have been recommended for use after specifichigh-risk procedures.Keywords anticoagulation; deep vein thrombosis; pulmona

4、ry embolus;thromboprophylaxis; venous thromboembolismThrombus formation in the deep veins of the dependentextremities carries significant morbidity. Treatment of deepvein thrombosis (DVT) exposes patients to further risk

5、 andrepresents a considerable burden on healthcare resources.Migration of clot fragments can result in pulmonary embolism(PE) which may be fatal. These conditions, collectively termedvenous thromboembolism (VTE), can be

6、difficult to diagnoseaccurately. Thus prevention of this condition is a clinicalimperative and one that has been the subject of recent UKGuidance.1IncidenceVTE accounts for 25,000 deaths annually in England. ManyDVTs are

7、 clinically silent and the published incidence is likelyto be a significant underestimate. Routine ultrasonography ofpatients after major surgical procedures reveals that, withoutprophylaxis, the incidence of DVT is 29%.

8、 The risk isparticularly high after orthopaedic surgery with an estimated40% developing DVT and 5% suffering PE. In the absence ofmalignancy, the lowest risk of VTE is after gynaecological,head and neck and laparoscopic

9、abdominal surgery.AetiologyFactors promoting the formation and propagation of thrombus inthe vascular system may be broadly divided into three groupsknown as Virchow’s Triad (Figure 1). The major risk factors forVTE are:

10、C Malignancy or cancertreatmentC Obesity (body mass index?30 kg/m2)C Pregnancy and puerperiumC Acute medical illnessC Recent myocardial infarctionor strokeC Major surgeryC Trauma (major or lowerextremity)C ImmobilityC In

11、creasing ageC Inflammatory bowel diseaseC Personal or family historyof VTEC Oestrogen-containing oralcontraception or hormonereplacement therapy in lastfour weeksC Varicose veins withassociated phlebitisC Central venous

12、catheterizationC Severe infectionC DehydrationC Inherited or acquiredthrombophiliaC Nephrotic syndromeC ParaproteinaemiaDiagnosisClinical diagnosis of DVT is unreliable as a variety of otherconditions may be clinically i

13、ndistinguishable (e.g. cellulitis,superficial thrombophlebitis or chronic venous insufficiency).More often the condition is unrecognized due to a lack of overtmanifestations. The assay for D dimer (a fibrin degradationpr

14、oduct) has a very low positive predictive value in the post-operative population. The use of a risk-scoring tool based onclinical findings and a D dimer assay may be useful to guideinitial management. Contrast venography

15、 may be used to defin-itively diagnose a DVT, but this test is invasive and carries a riskof venous thrombosis. Duplex ultrasonography is a commonlyused non-invasive method of diagnosis but carries significantresource im

16、plications. Computerized tomography (CT) andmagnetic resonance imaging (MRI) are both sensitiveand specific but their use is precluded in the clinical setting bycost.Pulmonary embolism may be equally difficult to diagnos

17、e dueto the low specificity of clinical examination, electrocardiog-raphy, chest radiography and ventilation:perfusion scanning.Learning objectivesAfter reading this article, you should:C be aware of the prevalence of ve

18、nous thromboembolism in theperioperative period and its attendant complicationsC be able to stratify patients according to their risk of peri-operative venous thromboembolismC understand the mechanism by which methods of

19、 preventionoperate and the evidence for their use.Tom Martin MBBS BSc(Hons) FRCA is a Specialty Registrar at the BristolSchool of Anaesthesia, UK. Conflicts of interest: none declared.Caroline Oliver FRCA is a Consultant

20、 in Anaesthesia and Critical Care atFrenchay Hospital, Bristol, UK. Her special interest is neuroanaesthesiaand critical care. Conflicts of interest: none declared.PERIOPERATIVE CAREANAESTHESIA AND INTENSIVE CARE MEDICIN

21、E 10:12 580 ? 2009 Elsevier Ltd. All rights reserved.weight heparin (LMWH) acts predominantly by the inhibition ofFactor Xa which catalyses conversion of prothrombin tothrombin. In contrast to UFH, prophylaxis with LMWH

22、is moreeffective at preventing VTE and may be given once daily. Inaddition, there is reduced incidence of heparin-inducedthrombocytopoenia (HIT) and a lower incidence of bleeding. Asa result, LMWH has become the mainstay

23、 of pharmacologicalthromboprophylaxis and should be considered for all but themost straightforward procedures. The use of LMWH combinedwith a mechanical intervention reduces risk of DVT by 71%.AspirinAspirin inhibits pla

24、telet function by irreversible inhibition ofcyclooxygenase-1 (COX-1). Although it has some efficacy inreducing the risk of VTE in surgical patients, it is less effectivethan LMWH and may be associated with more bleeding

25、events.There appears to be no additional benefit in combining aspirinwith LMWH.WarfarinAdjusted-dose warfarin therapy reduces the risk of DVT and PEand its efficacy is comparable to aspirin. However, it requirescareful d

26、osing and regular monitoring in addition to signifi-cantly increasing risk of major bleeding. As such it is notpractical for routine prevention of VTE in the perioperativepopulation.DextransDextrans inhibit red cell and

27、platelet adhesion as well as poten-tiating antithrombin. Preparations of large molecular weightdextrans (e.g. dextran 60 or 70) are poorly excreted and mayexert an antithrombotic action that lasts for several days. Theya

28、re administered as a colloid and must be given in volumesexceeding 1.5 l in order to achieve an anticoagulant effect. Theiruse may be complicated by allergic reactions in up to 4% ofpatients and their efficacy of VTE pre

29、vention is comparable toaspirin. For these reasons they are rarely used for this indicationalone.FondaparinuxFondaparinux is an antithrombin activator and thereby selec-tively inhibits Factor Xa. It exerts a similar anti

30、coagulant effect toheparin but without the risk of HIT, making it an alternative forpatients unable to take LMWH.Danaparoid and lepirudinDanaparoid inhibits Factors Xa and IIa and has an anticoagulantaction similar to LM

31、WH. Lepirudin is a direct thrombin inhibitor.Both are licensed for prevention of VTE in patients with HIT.Hip- and knee- replacement surgeryThis constitutes the greatest risk of perioperative VTE afterelective surgery. A

32、ccordingly, these patients benefit fromthromboprophylaxis that extends beyond hospital discharge. Thelogistical difficulties of managing LMWH administration outsidehospital have been recently overcome by the development

33、ofa number of directly acting oral anticoagulants.Dabigatran and rivaroxabanDabigatran is an oral direct thrombin inhibitor. Rivaroxaban isa direct Factor Xa inhibitor. Each has been recently recommendedfor the primary p

34、revention of VTE following total hip- or knee-replacement surgery.3,4 Treatment should continue for two weeksfollowing knee replacement and five weeks following hipreplacement. Each are at least as effective as LMWH in p

35、reventingVTE but may be associated with greater risk of significant bleeding.Anaesthesia and VTEA number of anaesthetic interventions may reduce the risk ofperioperative VTE. When positioning patients for surgery, useful

36、measures include the use of heel pads to avoid calf veincompression and the elevation of limbs to promote venousreturn. IPC devices are ideally suited for use during generalanaesthesia. Avoidance of dehydration reduces t

37、he risk ofhypercoagulability.The sole use of neuraxial blockade has been associated witha reduction in post-operative VTE after hip surgery. This benefitappears to be lost when a combined technique is used. It issuggeste

38、d that other regional techniques may carry similaradvantages. However, it is important to consider the timing ofanticoagulation in relation to any regional technique, in partic-ular, neuraxial blockade. AREFERENCES1 NICE

39、 Clinical guideline 46. Reducing the risk of venous thrombo-embolism in inpatients undergoing surgery. National Institute ofClinical Excellence; April 2007.2 Geerts WH, Bergqvist D, Pineo GF, et al. Prevention of venous

40、thrombo-embolism; American College of Chest Physicians evidence-based clinicalpractice guidelines (8th Edition). Chest 2008; 133: 381Se453.3 NICE technology appraisal guidance 157. Dabigatran etexilate for theprevention

41、of venous thromboembolism after hip or knee replacementsurgery in adults. National Institute of Clinical Excellence; September 2008.4 NICE technology appraisal guidance 170. Rivaroxaban for the preven-tion of venous thro

42、mboembolism after total hip or total knee replace-ment in adults. National Institute of Clinical Excellence; April 2009.PERIOPERATIVE CAREANAESTHESIA AND INTENSIVE CARE MEDICINE 10:12 582 ? 2009 Elsevier Ltd. All rights