Perioperative Anticoagulation in Patients With a Mechanical Heart Valve Who Are Undergoing Elective Noncardiac Surgery: Materials and Methods

In: Mechanical Heart

19 Sep 2014

Survey Methods
The survey was mailed to all members of the Canadian Society of Internal Medicine (n = 420) and the Canadian Cardiovascular Society (n = 540) in July 1997, with a repeat mailing in December 1997 to nonresponders. A priori, criteria were established to exclude returned surveys from the analysis: (1) physician does not manage anticoagulant-related problems in adults; (2) physician no longer resides at the address provided, ie, survey returned to sender; (3) survey was partially completed; and (4) physician has retired from medical practice.Survey Questions
Physicians were asked to provide anticoagulation preferences in four scenarios of patients with a mechanical heart valve who are undergoing elective surgery (Table 1). The scenarios represented four different combinations of risks for TE (high or low) and bleeding (high or low). However, this information was not provided in the survey. For each scenario, physicians were asked to select from a standardized list of preoperative and postoperative anticoagulation options or, if these options were not acceptable, to provide an alternative anticoagulation strategy (Table 2). Options “a” and “b” (preoperative and postoperative) were classified as aggressive anticoagulant management, and options “c” (preoperative and postoperative) and “d” (postoperative) were classified as less aggressive anticoagulant management. We also requested information relating to a respondent’s medical specialty (general internal medicine, cardiology, cardiac surgery, or other) and their frequency of managing anticoagulant-related problems (frequently, infrequently, or not at all). purchase zyrtec

Analysis
The analysis consisted of four parts. (1) Anticoagulation preferences in different scenarios: The proportion of respondents who selected each of the anticoagulation options was determined for each scenario. (2) Effect of TE risk on preoperative and postoperative anticoagulation preferences: The proportion of respondents who preferred aggressive anticoagulant management (ie, options “a” or “b”) was compared in scenario pairs in which the TE risk was high in one scenario and low in the other scenario, and the bleeding risk was the same in both scenarios. (3) Effect of bleeding risk on postoperative anticoagulation preferences: The proportion of respondents who preferred aggressive anticoagulant management (ie, options “a” or “b”) was compared in scenario pairs in which the bleeding risk was high in one scenario and low in the other scenario, and the TE risk was the same in both scenarios. (4) Effect of TE or bleeding risk on the timing of postoperative IV heparin initiation: The proportion of respondents who preferred early heparin initiation, defined as starting heparin within 12 h after surgery, was compared in scenario pairs in which the TE risk was high in one scenario and low in the other scenario, and the bleeding risk was the same in both scenarios; and in scenario pairs in which the bleeding risk was high in one scenario and low in the other scenario, and the TE risk was the same in both scenarios. McNemar’s x2 test was used to compare the proportion of respondents who preferred aggressive anticoagulant management within scenario pairs. Statistical significance was defined as p < 0.05.
Table 1—Clinical Scenarios

1. A 70-year-old woman with a mechanical mitral valve, chronic atrial fibrillation, and a previous stroke 2 years ago is to undergo elective (open) subtotal colectomy for resection of adenocarcinoma of the colon (TE risk, high; bleeding risk, high)
2. A 65-year-old man with a mechanical aortic valve is to undergo elective (open) subtotal colectomy for resection of adenocarcinoma of the colon (TE risk, low; bleeding risk, high)
3. A 75-year-old man with a mechanical mitral valve, a previous stroke 3 years ago, and chronic atrial fibrillation is to undergo elective bilateral inguinal hernia repair (TE risk, high; bleeding risk, low)
4. A 48-year-old woman with a mechanical aortic valve is to undergo elective bilateral inguinal hernia repair (TE risk, low; bleeding risk, low)

Table 2—Anticoagulation Options

Preoperative anticoagulation options
a: Admit to hospital 2 to 4 days preoperatively for full-dose IV heparinj
b: Outpatient full-dose SC heparin or LMWH!
c: Nothing else other than stopping warfarin preoperatively
d: Other
Postoperative anticoagulation options
a: Full-dose in-hospital IV heparin until INR therapeutic! Heparin to be restarted < 6 h postoperatively 6 to 12 h postoperatively > 12 h postoperatively
b: Early discharge home with full-dose SC heparin or LMWH until INR therapeutic!
c: Low-dose in-hospital SC heparin or LMWH until INR therapeutic!
d: Nothing else other than restarting warfarin postoperatively e: Other

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