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    Nov
  • Implementation and Evaluation of a Warfarin Dosing Service for Rehabilitation Medicine: Report from a Pilot Project: RESULTS part 2

rehabilitation medicine

Data Obtained during Pilot Project for Rehabilitation Warfarin Dosing Service (2003-2004)

A total of 33 patients were followed through the pilot project for the rehabilitation warfarin dosing service during the 5-month study period. A group of 33 patients who underwent physician dosing on other units during this period served as the concurrent control group. Tables 5 to 8 compare results for the concurrent control group with those of the patients treated through the warfarin dosing service (pilot project group).

The concurrent control group had fewer women than the pilot project group, a similar mean age but a greater age range, and similar body weight (Table 5). In both groups, the primary reason for admission was rehabilitation after major orthopedic surgery. Slightly more patients in the pilot project group had cardiovas­cular disease, and more of these patients had a history of gastrointestinal problems. The mean duration of the hospital stay was 22.2 days for the concurrent control group and 26.9 for the pilot project group.

Warfarin therapy at acute care facilities before admission to the rehabilitation unit was of shorter duration among patients in the concurrent control group than among those in the pilot project group (8.4 and 12.9 days, respectively) (Table 6), and mean duration of warfarin therapy in the rehabilitation unit was also shorter for patients in the concurrent control group (22.2 and 26.9 days, respectively). In both groups, the most common indication for warfarin was DVT prophylaxis.
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Table 5. Characteristics of Patients in Concurrent Control Group and Patients Receiving Warfarin Dosing Service (Pilot Project Group)


Characteristic



No. (%)
of Patients or Mean (Range)
Concurrent Control Warfarin Dosing Service (Physician Dosing)


No. of patients


33


33


Age (yr)


71


(34-96)


72


(47-88)


Sex


Men


8


(24)


6


(18)


Women


25


(76)


27


(82)


Body weight (kg)


68.7


(36.0-118.1)


70.5


(47.3-111.1)


Length of stay (days)


22.2


(4-70)


26.9


(5-94)


Reason for
rehabilitation


Orthopedic surgery


31


(94)


32


(97)


Amputation


2


(6)


1


(3)


Medical history


Deep vein thrombosis or
pulmonary embolism


3


(9)


4


(12)


Cardiovascular diseaset


13


(39)


14


(42)


Gastrointestinal
disease or peptic ulcer disease


6


(18)


12


(36)


Cancer


3


(9)


2


(6)



*Patients in the concurrent
control group were treated on other units during the period of the pilot
project (October
16, 2003,
to March
18, 2004).
tCoronary artery disease, ischemic
heart disease, cerebrovascular accident.

In terms of warfarin management, most patients in both the concurrent control group and the pilot project group were receiving transition dosing (Table 6). Physician dosing in the concurrent control group was associated with a mean of 9.9 warfarin orders per patient, whereas dosing through the pilot project was associated with 9.3 orders per patient (Table 6). The number of concurrent medications was similar in the 2 groups (12.8 and 13.6 in the concurrent control and pilot project groups, respectively), and patients in each group had a mean of 2.4 drug interactions during the hospital stay. The most common drug interactions were acetaminophen (30 [91%] of patients in the concurrent control group and 26 [79%] of those in the pilot project group), statins (10 [30%] and 9 [27%]), and antibiotics (7 [21%] and 7 [21%]).
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Table 6. Warfarin Use Before and During Admission for Concurrent Control and Pilot Project Groups


Characteristic


No.
(%)
of Patients or Mean
(Range) Concurrent Control Warfarin Dosing Service (Physician Dosing)
(n
= 33)

(n

= 33)


Duration of therapy before admission (days)


8.4


(3-20)


12.9


(5-49)


Duration of warfarin therapy on unit (days)


22.2


(4-70)


26.9


(5-94)


Indication for warfarin


Atrial fibrillation


5


(15)


4


(12)


DVT prophylaxis


27


(82)


27


(82)


DVT treatment


1


(3)


2


(6)


CVA prophylaxis


6


(18)


3


(9)


Type of warfarin therapy*


Initiation


0


0


Maintenance


6


(18)


5


(15)


Transition


27


(82)


28


(85)


No. of medications during admission


12.8


(6-19)


13.6


(6-23)


No. of warfarin interactions during admission


2.4


(1-4)


2.4


(1-4)


No. of orders for warfarin during admissiont


328


(9.9)


308


(9.3)

Mean baseline INR on admission was therapeutic in the 2 groups, with a range from subtherapeutic to supratherapeutic (Table 7). The number of INR results obtained per patient during the hospital stay was similar (9.9 and 9.3), and the time to reach the first therapeutic INR was about 3 days in each group. The proportion of INR results within the therapeutic range was lower in the concurrent control group than in the pilot project group (50.9% and 67.9%, respectively); conversely, greater proportions of INR results were subtherapeutic (33.2% and 22.7%) and supratherapeutic (14.9% and 9.4%) (Table 7). No vitamin K or fresh frozen plasma (FFP) was required for patients in either group.

Table 7. INR Results for Concurrent Control and Pilot Project Groups


Characteristic


Mean (Range) Concurrent Control
Warfarin Dosing Service (Physician Dosing) (n

= 33)
(n
= 33)


Baseline INR on admissiont


2.24


(1.05-3.90)


2.19


(1.22-3.98)


No. of INR results during hospital
stay


9.9


(1-31)


9.3


(3-23)


Time to reach first therapeutic INR
(days)


3.0


(0-14)


2.8


(0-10)



INR value


(%

of
results while receiving warfarin)



Therapeutic


(2.0-3.0)


50.9


(0-100)


67.9


(0-100)



Subtherapeutic


(< 2.0)


33.2


(0-100)


22.7


(0-100)



Supratherapeutic


(3.01-3.99)


12.8


(0-50)


9.1


(0-50)



Supratherapeutic


(4.0-6.0)


2.1


(0-20)


0.3


(0-11.1)



Supratherapeutic


(> 6.0)


0


0


Total no. of vitamin K doses


0


0


No. of times FFP given


0


0

Within the concurrent control group, 1 patient experienced fatal pulmonary embolism, 2 patients experienced minor bleeding, and 2 patients experienced major bleeding (Table 8). In contrast, the only adverse outcome in the pilot project group was minor bleeding in 1 patient (Table 8).

Clinical Pharmacy Interventions during the Pilot Project

The new warfarin dosing service required physician referrals and clinical pharmacy resources. Clinical pharmacy interventions during the pilot project included warfarin dosage adjustments, INR monitoring (ordering and follow-up), identification and management of drug interactions, and patient education (Table 9).
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Table 9. Clinical Pharmacy Interventions for Pilot Project Group (n = 33)




Intervention




Result


Adjustments to warfarin
dosing


Total no. and range


308


(1-31)


Mean per patient


9.3


Mean no. (and range) of
INR monitoring


9.3


(3-23)


activities per patient
(orders, follow-up)


Mean no. (and range) of
drug interctions


2.2


(1-4)


identified and managed
per patientt


Patient education
sessions*


Total no. and range


83


(1-5)


Mean per patient


2.5


Clinical pharmacist’s
time for new patient


Initial patient
interview



10-20
min per patient


Monitoring forms



10-20
min per patient


Clinical pharmacist’s
daily time for routine



follow-up (for
1-10
patients)


Reporting INR results


4-48
min daily total


Follow-up patient
interviews


5-45 min daily total


Documentation and
computer entry


2-30 min daily total


Writing warfarin orders


5-16
min daily total



Total time (for
1-10
patients)



16-139
min daily total

Several of these activities can be considered as constituting risk management: routine surveillance for signs and symptoms of bleeding and/or thromboem- bolism, identification and management of interactions between warfarin and other drugs, and achievement and maintenance of therapeutic INR results as quickly and safely as possible. The drugs most frequently involved in interactions with warfarin were acetaminophen, statins, allopurinol, and antibiotics, all of which have a tendency to increase INR and decrease the warfarin requirements.

The clinical pharmacist (T.C.) provided 83 predischarge episodes of patient education for the 33 patients in the pilot project group (Table 9). Examples of counselling included warfarin education; interactions of warfarin with other drugs, diet, and lifestyle; and signs and symptoms of bleeding.
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Clinical pharmacy services were available at all times, either during regular hours or on an on-call basis (evenings, weekends, and statutory holidays). The total daily time required for the warfarin service ranged from 16 to 150 minutes (for 1 to 10 patients).

The clinical pharmacist’s time was spent doing the work-up for new patients and performing routine follow-up for patients in the pilot project (Table 9). Work-up for a new patient involved completing the patient monitoring form and performing an initial patient interview, for a total of 20 to 40 minutes per new patient (Table 9). Routine follow-up included following up on INR results, conducting follow-up interviews with patients, performing documentation and computer entry, and writing warfarin orders, for a total of 16 to 139 minutes daily (for up to 10 patients).

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