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  • Implementation and Evaluation of a Warfarin Dosing Service for Rehabilitation Medicine: Report from a Pilot Project: DISCUSSION

Previous studies throughout North America have yielded strong evidence that inpatient and outpatient warfarin dosing services and clinics staffed by qualified personnel are associated with better patient outcomes and anticoagulation management. This study was performed to determine whether a pilot project at Providence Healthcare would support a hospital-wide inpatient warfarin dosing service.

The goals and objectives for the warfarin dosing service, listed above, were met during the 5-month period of the pilot project. Anticoagulation therapy provided during the pilot project was safe and effective, as indicated by maintenance of the INR within the therapeutic range for most INR tests, lower frequency of negative outcomes, and prevention of DVT and pulmonary embolism.

Qualified Personnel

The 12 consensus guidelines of the Anticoagulation Guidelines Task Force indicate that qualified personnel in anticoagulation management may be physicians, nurses, pharmacists, or other health care professionals who have completed specialized anticoagulation training, education, and certification. This group strongly recommends that providers of anticoagulation care have the Certified Anticoagulation Care Provider (CACP) designation, currently available only in the United States.
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Since 2002, a 4-day anticoagulation workshop for clinical pharmacists has been available in Canada for warfarin training, education, and certification.33 The workshop contains 7 modules with content similar to the CACP material. Participants receive a certificate of completion after passing a 4-h written exam. As of June 2004, 6 pharmacists at Providence Healthcare had been certified and available to provide hospital-wide warfarin management; these pharmacists report to an on-site medical supervisor when needed.

Similarities among the Study Groups

Data for the 3 study groups (2 control and 1 intervention) showed that Providence Healthcare routinely admitted patients for rehabilitation after orthopedic surgery. These elderly, primarily female patients had a higher risk of thromboembolism and/or bleeding because of concurrent diseases, polypharmacy, prolonged hospital stay, and other factors, and were similar to study groups described elsewhere. Warfarin management required about 10 INR tests per patient, and about 11% of these tests indicated supratherapeutic INR (i.e., increased risk of bleeding). Clearly, anticoagulation management must be a high priority at this institution. These results support a standardized warfarin dosing service. The 3 study groups showed similar characteristics:

  • warfarin therapy before admission in most patients (mean duration 11 days)
  • warfarin primarily for DVT prophylaxis
  • primarily transition dosing (i.e., fluctuating warfarin doses and INR results because of various factors such as drug interactions)
  • mean of 2 interactions with other drugs (usually acetaminophen, statins, or antibiotics)
    target INR 2.0-3.0 for all patients
  • no readmissions to Providence Healthcare for DVT, pulmonary embolism, or cerebrovascular accident (as of March 2004)
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Favourable Results with Warfarin Dosing Service

The warfarin dosing service was safer and more effective than dosing provided by physicians, for both the baseline and concurrent control groups. The limitations of the evaluation of the warfarin dosing service were the small sample size (33 patients), the short study period (5 months), the fact that there was only 1 certified anticoagulation pharmacist at the time of the pilot project, and the lack of a statistical analysis (i.e., the observed differences may have been due to chance).

The warfarin dosing service was associated with slightly fewer warfarin orders than the control groups; a slightly faster time to therapeutic INR; a greater proportion of INR results within the therapeutic range; lower propor­tions of subtherapeutic and supratherapeutic INR results; fewer adverse outcomes; no use of vitamin K or fresh frozen plasma; no new diagnoses of DVT, pulmonary embolism, or cerebrovascular accident; and no deaths.

The warfarin dosing service started on October 16, 2003, was a pilot project — a service new to the institution and to its physicians, nurses, and pharmacists. Therefore, as with any new service, it was to be expected that additional time would be required to learn the protocols and provide the services. With experience and greater patient numbers, efficiencies in the delivery of the service may be expected.
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