Pharmacy & Therapeutics - February 2008 - (Page 108)

Management of Acute Venous Thromboembolism aged by our facility’s outpatient warfarin clinic for approximately one year after the acute event unless an adequate duration of therapy was fulfilled prior to one year or the patient had died within one year after the acute VTE. We collected the following patient demographic information: • • • • • • age, weight, and sex creatinine and creatinine clearance (CrCl) baseline hemoglobin and platelet counts bleeding status starting warfarin dose and duration of warfarin therapy medical history, including heart failure, cancer, myocardial infarction (MI), and cerebrovascular accident (CVA) • concomitant interacting medications: amiodarone (Cordarone, Wyeth), sulfamethoxazole/trimethoprim (Bactrim, Women First/Nicholas Primalal), fluconazole (Diflucan, Pfizer), metronidazole (Flagyl, Pfizer), and/or aspirin • documented risk factors present at the time of the current VTE such as a hypercoagulable state, trauma, surgery, and/or immobility. (Examples of a hypercoagulable state included cancer, antiphospholipid antibody syndrome, or Factor V Leiden.) If no risk factors were documented, we classified the VTE as idiopathic. The Crockcroft–Gault equation was used to determine CrCl. To assess for appropriateness of initial therapy, we evaluated whether patients: • continued with UFH or LMWH therapy for five days or longer. • had an INR of 1.9 or higher when heparin was stopped. • were given the appropriate starting dose of warfarin. • received the correct dose of enoxaparin (Lovenox, SanofiAventis) or UFH dosing. • continued with warfarin for the appropriate duration of therapy. The current ACCP guidelines recommend that the INR be stable and above 2 when heparin is stopped, but we considered an INR of 1.9 and above at the time of discontinuing heparin to be appropriate, assuming a laboratory variation of ±10%. Our facility’s current dosing guidelines for enoxaparin are 1 mg/kg (actual body weight) subcutaneously every 12 hours: • age younger than 70 years: rounded up to 60/80/100 mg • age older than 70 years: rounded down to 60/80/100 mg To adequately account for this rounding, we considered 0.8 to 1.2 mg/kg to be appropriate. Bleeding was characterized as minor or major. We defined “major” bleeding as a decrease in hemoglobin of 2 g or more, an episode of bleeding requiring the transfusion of more than 2 units of blood, or bleeding occurring in a critical site in the body (e.g., the retroperitoneal cavity or the intracranial space). We limited the definition of “recurrence” to a repeated VTE event occurring within one year after the initial acute episode. The broad definition of recurrence as any repeated VTE was classified as the number of VTE events (a first or a second VTE). We used the SAS 9.1 program (2004) to perform the statistical analysis on predetermined variables. Chi-square tests of independence were used to compare categorical variables of interest in both the recurrence and non-recurrence groups and in the major bleeding and non-bleeding groups. We considered differences to be statistically significant if the associated P value was less than 0.05. RESULTS We collected data from 150 patient charts. The majority of patients were men (n = 146; 97.3%); only four subjects were women (2.7%). The mean age of our subjects was 67.3 (range, 38–89 years of age), and their mean weight was 90.7 kg (range, 53–212 kg or 116.6–466.4 pounds) (see Table 1). Forty-three patients (28.7%) died within one year after the acute VTE was diagnosed. Seventy patients (46.7%) were classified as having idiopathic DVT and/or PE. Documented risk factors for VTE were recorded as follows (see Table 1): • Forty-seven patients (31.3%) had a hypercoagulable state. • Six patients (4%) had recent trauma or underwent surgery. Table 1 Overall Patient Demographics At the VA Medical Center in Fargo Age (years, mean ± SD) Weight (kg, mean ± SD) CrCl (mL/minute, mean ± SD) Baseline Hb (g/dL, mean ± SD) Baseline platelet count (K/cm3, mean ± SD) 67.3 ± 11.5 90.7 ± 23.2 63.3 ± 20 12.8 ± 2.3 243.9 ± 124.7 No. of Patients (%) Indication DVT PE Both DVT and PE Risk factor for DVT and/or PE Hypercoagulable state Trauma or surgery Immobility Idiopathic Past medical history Heart failure Cancer Myocardial infarction Cerebrovascular accident Concomitant interacting medications Amiodarone (Cordarone) Sulfamethoxazole/trimethoprim (Bactrim) Fluconazole (Diflucan) Metronidazole (Flagyl) Aspirin 126 (84) 8 (5.3) 6 (10.7) 47 (31.3) 6 (4) 34 (22.7) 70 (46.7) 23 (15.3) 52 (34.7) 21 (4) 13 (8.7) 6 (4) 5 (3.3) 7 (4.7) 8 (5.3) 21 (14) CrCl = creatinine clearance; DVT = deep vein thrombosis; Hb = hemoglobin; PE = pulmonary embolism. 108 P&T® • February 2008 • Vol. 33 No. 2

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Pharmacy & Therapeutics - February 2008 Contents Editorial Medication Errors Prescription: Washington The Language of (Forgive Us) Change, As P&T Enters the Digital Age New Drugs/Drug News/New Medical Devices Drug Forecast Use and Outcomes of Antifibrinolytic Therapy in Patients Undergoing Cardiothoracic Surgery at 20 Academic Medical Centers in the United States Evaluation of the Management of Acute Venous Thromboembolism and Its Outcomes: One Institution's Experience American Society of Hematology, 49th Annual Meeting Pharmaceutical Approval Update

Pharmacy & Therapeutics - February 2008

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