Pharmacy & Therapeutics - February 2008 - (Page 109)

Management of Acute Venous Thromboembolism • Another 34 patients (22.7%) were immobile at the time of the VTE. The documented and preselected past medical history components that we analyzed included heart failure, cancer, MI, and CVAs. About one-third of our patients ((34.7%; n = 52) had a history of cancer. As shown in Table 1, 23 patients (15.3%) had heart failure, 21 patients (14%) had a history of MI, and 13 patients (8.7%) had a history of CVA. We recorded the use of five concomitant medications that had the potential to increase the INR or the risk of bleeding. Aspirin was used most frequently, with 21 patients (14%) using aspirin concurrently during warfarin therapy. Eight more patients (5.3%) received metronidazole; seven patients (4.7%), fluconazole; six patients (4%), amiodarone; and five patients (3.3%), sulfamethoxazole/trimethoprim (see Table 1). Eighty-one patients (54%) stayed with warfarin therapy for more than six months. Of these patients, 48 (57%) were being treated for a first-time DVT, a PE, or both. As presented in Table 2, 32 patients (21.3%) continued taking warfarin for three months or less, and 28 patients (18.7%) continued taking warfarin for more than three months but for six months or less. Twenty patients (13.3%) experienced a major bleeding event, 29 patients (19.3%) had a minor bleeding episode, and 101 patients (67.3%) did not experience any bleeding (Table 3). The mean baseline hemoglobin was suboptimal at 12.8 ± 2.25 g/dL (normal range = 13.5–17.5 g/dL). The mean baseline platelet count was within the normal range at 243.9 ± 124.6 K/cm3 (normal range = 150–450 K/cm3) (see Table 1). Of the 20 patients who experienced a major bleeding episode, nine patients (45%) experienced a drop in hemoglobin of 2 g/dL or more, nine patients (45%) needed a transfusion of more than 2 units of red blood cells, and six patients (30%) experienced bleeding in a critical (retroperitoneal or intracranial) site. As shown in Table 2, most subjects were started on warfarin 5 mg daily; 104 patients (69.3%), on 5 mg daily; 11 patients (7.3%), on 7.5 mg; and 21 patients (14%), on 10 mg daily. Another three patients (2%) received a starting dose of less than 5 mg. The initial warfarin dose was unknown in two patients (1.3%). Seventy-six patients received enoxaparin, and 73 of these (96.1%) received an appropriate initial dose. Eighty-four patients received UFH; of these patients, 46 (54.7%) received the correct bolus and infusion rate of UFH, according to our weight-based heparin formulation. Dosing of UFH was inappropriate in 38 patients (45.3%) (see Table 2). The mean duration of heparin therapy was seven days, and 40% of the patients received heparin for less than five days. The INR at the time of heparin discontinuation was unknown in 19 patients (12.7%), was below 1.9 in 29 patients (19.3%), and was 1.9 or higher in 102 patients (68%). Ten patients (6.7%) had an INR of 2 when heparin was stopped (see Table 2). When we compared the patient groups with major bleeding and without bleeding, there was a statistically significant difference between the two groups in the number of patients with an INR greater than 3 at the time of bleeding (P 5 days INR at discontinuation of heparin Unknown <1.9 ≥1.9 Starting warfarin dose 5 mg 7.5 mg 10 mg Other Starting enoxaparin dose 0.8–1.2 mg/kg 1.2 mg/kg Starting bolus and CI heparin dose Appropriate per weight-based heparin protocol Inappropriate per heparin protocol Duration of warfarin therapy Never started warfarin > 0 to ≤ 3 months > 3 to ≤ 6 months > 6 to ≤ 12 months > 12 months 5 (3.3) 50 (33.3) 85 (56.7) 19 (6.7) 29 (12.7) 102 (68) 104 (69.3) 11 (7.3) 21 (14) 11 (9.3) 73 (96.1) 3 (3.9) 46 (54.7) 38 (45.3) 9 (6) 32 (21.3) 28 (18.7) 29 (19.3) 52 (34.7) CI = continuous infusion; INR = International Normalized Ratio. the bleeding event. Cancer tended to be associated with a risk of major bleeding (P = 0.0627). No other statistically significant differences were identified when we compared the major bleeding and non-bleeding groups according to these variables: (1) baseline hemoglobin and platelet counts, (2) CrCl, (3) age older than 65 years, (4) a history of CVA or heart failure, and (5) the duration of warfarin therapy of more than six months in those patients with a first-time DVT and/or a PE. Similarly, we did not identify any statistically significant differences between the recurrence and non-recurrence groups when we assessed these variables: an INR below 1.9 at the time of heparin discontinuation, a history of cancer, a duration of warfarin therapy for less than three months, and a hypercoagulable state. A total of 21 patients (14%) had a recurrent episode within one year of their VTE (see Table 3). DISCUSSION Our primary objective was to evaluate the appropriateness of VTE management at our institution according to published standard practice guidelines. Whenever practice deviates from evidence-based standard guidelines, it can place patients at risk for adverse outcomes. We discovered these divergences: Vol. 33 No. 2 • February 2008 • P&T® 109

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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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