Correspondence
Anticoagulation and Elective Surgery
N Engl J Med 1997; 337:938-940September 25, 1997
- Article
To the Editor:
In their review of the management of anticoagulation before and after elective surgery, Kearon and Hirsh (May 22 issue)1 assert that in patients with mechanical heart valves, anticoagulation should be discontinued perioperatively. They assume that the “temporary discontinuation of warfarin . . . exposes patients to a risk of thromboembolism equivalent to one day without anticoagulation before surgery and another day without anticoagulation after surgery.” Although this may be possible when patients have an international normalized ratio (INR) between 2.0 and 3.0, it does not seem likely for patients with an INR between 2.5 and 3.5. At this higher level, patients will need a longer time without warfarin preoperatively and a longer time with warfarin postoperatively, thus increasing the length of their time at risk for thromboembolism.
Patients with mechanical valves in the mitral position are considered to have a high risk of thromboembolism and therefore require an INR between 2.5 and 3.5. Two studies, both retrospective reviews, have examined how these patients fare without anticoagulation in the perioperative period. In their report of patients with prosthetic valves who required surgery, Katholi et al. noted that 2 of 10 patients with mitral or combined mechanical valves had fatal strokes when anticoagulation was discontinued three to five days preoperatively.2 Tinker and Tarhan noted that among 74 patients with mitral or combined mechanical valves, none had embolic events in the absence of anticoagulation.3 But interpreting the results of the latter study is difficult, because it is not clear for how many days patients with mitral valves did not receive anticoagulants.
An alternative approach for patients who have mechanical mitral valves or who are otherwise at high risk for thromboembolism is to stop warfarin five days before surgery and start intravenous heparin or low-molecular-weight heparin once the INR becomes subtherapeutic. Heparin may then be restarted on the second postoperative day. This technique permits the patient to be without anticoagulants for only one day. Waiting until the second day to start anticoagulation should decrease postoperative bleeding.
3 ReferencesJohn Spandorfer, M.D.
Geno Merli, M.D.
Jefferson Medical College, Philadelphia, PA 191071
Kearon C ,Hirsh J . Management of anticoagulation before and after elective surgery. N Engl J Med 1997;336:1506-1511
Full Text | Web of Science | Medline2
Katholi RE ,Nolan SP ,McGuire LB . Living with prosthetic heart valves: subsequent noncardiac operations and the risk of thromboembolism or hemorrhage. Am Heart J 1976;92:162-167
CrossRef | Web of Science | Medline3
Tinker JH ,Tarhan S . Discontinuing anticoagulant therapy in surgical patients with cardiac valve prostheses: observations in 180 operations. JAMA 1978;239:738-739
CrossRef | Web of Science | Medline
To the Editor:
Kearon and Hirsh suggested that it was safe to stop anticoagulation in patients with nonvalvular atrial fibrillation who were scheduled for elective surgery and that the risk of thromboembolism did not justify the use of either preoperative or postoperative intravenous heparin. As the authors noted, the average risk of thromboembolism in this population is 4.5 percent per year without anticoagulation, but the risk is variable and depends on the presence of certain factors.1 The risk of thromboembolism is considerably higher among patients who have had a transient ischemic attack or stroke within the previous three months (12 percent per year),2 and even higher (17.6 percent per year) among patients who have two or three risk factors (a history of thromboembolism, hypertension, or recent congestive heart failure).3 Patients with nonrheumatic atrial fibrillation are therefore not a homogeneous population in terms of their risk of thromboembolism, and a one-rule-fits-all approach to the perioperative management of anticoagulation may not be appropriate. Management should be stratified according to an individual patient's risk of thromboembolism as compared with the risk of surgical bleeding. Given that a stroke in patients with atrial fibrillation is fatal or is associated with a severe neurologic deficit in over 60 percent of cases,4 there is a persuasive argument for a more aggressive approach to prophylaxis against thromboembolism, including the use of both preoperative and postoperative intravenous heparin, in high-risk patients.
4 ReferencesStuart M. Lowson, M.B., B.S.
Eric W. Hanson, M.D.
University of Virginia Health Sciences Center, Charlottesville, VA 22906-00101
Risk factors for stroke and efficacy of antithrombotic therapy in atrial fibrillation: analysis of pooled data from five randomized controlled trialsArch Intern Med 1994;154:1449-1457[Erratum, Arch Intern Med 1994;154:2254.]
CrossRef | Web of Science | Medline2
European Atrial Fibrillation Trial Study Group
Web of Science | Medline3
The Stroke Prevention in Atrial Fibrillation Investigators
Web of Science | Medline4
Fisher CM . Reducing risks of cerebral embolism. Geriatrics 1979;34:59-61, 65
Web of Science | Medline
To the Editor:
Drs. Kearon and Hirsh recommend that perioperative intravenous heparin not be used in patients with mechanical valves except during the first month after systemic embolism, when, they conclude, the use of only preoperative heparin appears justified. The authors fail to take into consideration the relative risk associated with the various types of mechanical valves (caged ball vs. tilting disk) and the position of the valve (mitral vs. aortic). Nor is it apparent that they account for coexisting cardiac conditions (e.g., left ventricular dysfunction, atrial fibrillation, or recent myocardial infarction). The fourth American College of Chest Physicians Consensus Conference on Antithrombotic Therapy recommends perioperative heparin therapy for patients at high risk for thromboembolism, such as those with mechanical mitral-valve prostheses who are undergoing major surgery.1 In a recent review, Vongpatanasin et al.2 recognized the importance of such factors and recommended perioperative heparin therapy in patients with “caged-ball prosthetic valves, mechanical mitral valves, atrial fibrillation, left atrial thrombus, previous systemic embolization, or severe left ventricular dysfunction.”
Although we agree that there is certainly room for the strategy described by Kearon and Hirsh in selected patients, we wish to emphasize the importance of using clinical judgment and risk assessment in individual patients.
2 ReferencesAlaa Shalaby, M.D.
Syed M. Mohiuddin, M.D.
Creighton University, Omaha, NE 68131-20441
Stein PD ,Alpert JS ,Copeland J ,Dalen JE ,Goldman S ,Turpie AG . Antithrombotic therapy in patients with mechanical and biological prosthetic heart valves. Chest 1995;108:Suppl:371S-379S[Erratum, Chest 1996;109:592.]
CrossRef | Web of Science | Medline2
Vongpatanasin W ,Hillis LD ,Lange RA . Prosthetic heart valves. N Engl J Med 1996;335:407-416
Full Text | Web of Science | Medline
Author/Editor Response
The authors reply:
To the Editor: We agree with Drs. Spandorfer and Merli that patients who have a targeted INR of 2.5 to 3.5 may need a longer time without warfarin before surgery, depending on what the measured INR is about five days preoperatively. If the INR is greater than 3.0, it may mean that an additional daily dose of warfarin has to be withheld, but that should not increase the amount of time preoperatively during which the INR is less than 2.0, since it will take commensurably longer for the initially high INR to return to 2.0. The situation is similar when warfarin is restarted after surgery. If, as Drs. Spandorfer and Merli propose, such patients have an increased risk of thromboembolism while their INR is 2.0 to 2.5, the magnitude of this effect would be extremely small and would not alter our recommendations.
Drs. Spandorfer and Merli, Lowson and Hanson, and Shalaby and Mohiuddin all expressed concern that our recommendations were based on calculations that use the average risk of thromboembolism in patients with mechanical heart valves or atrial fibrillation who are not receiving anticoagulants. We acknowledged this point in our article; however, even in patients with the highest individual risk of arterial embolism (excluding those with embolism within one month after surgery), the argument in favor of administering intravenous heparin preoperatively remains weak, and after major surgery, intravenous heparin is still likely to do more harm than good. As an example, with a base-line risk of arterial embolism of 25 percent per year, one day without anticoagulation is associated with a risk of major embolism of approximately 1 in 2000 (0.05 percent). After major surgery, we estimate that the risk of arterial embolism needs to be about 9 percent per month (108 percent per year) just to offset morbidity from heparin-induced bleeding. Delaying the initiation of intravenous heparin until 24 hours after operation will lessen but not eliminate the associated morbidity. We do recommend the postoperative use of subcutaneous heparin in doses used as prophylaxis against venous thromboembolism in high-risk patients, including patients with arterial indications for anticoagulation.
Randomized, controlled trials assessing the perioperative use of intravenous heparin in patients with different indications for long-term anticoagulation would provide better data on which to base management decisions. Until such trials are performed, debate continues to be appropriate. However, until more reliable data than those on which our analysis is based become available, we stand behind our recommendations.
Clive Kearon, M.D., Ph.D.
Jack Hirsh, M.D.
McMaster University, Hamilton, ON L8V 1C3, Canada- Citing Articles (4)
Citing Articles
1
F. Baudo, F. Cataldo, G. Mostarda, A. Ghirarduzzi, M. Molinatti, V. Pengo, D. Poli, A. Tosetto, E. Tiraferri, E. Morra. (2007) Management of patients on long-term oral anticoagulant therapy undergoing elective surgery: survey of the clinical practice in the Italian anticoagulation clinics. Internal and Emergency Medicine 2:4, 280-284
CrossRef2
Francesco Baudo. (2006) “Bridging” therapy in patients on long-term vitamin K antagonist treatment: a yet unsolved issue. Internal and Emergency Medicine 1:2, 94-95
CrossRef3
Don R. Hirschman, Lesa J. Morby. (2006) A Study of the Safety of Continued Anticoagulation for Cataract Surgery Patients. Nursing Forum 41:1, 30-37
CrossRef4
Antònia Agustí, Pilar Tornos. (2005) Tratamiento anticoagulante crónico durante el período perioperatorio. Medicina Clínica 125:9, 353-355
CrossRef
