Postoperative anticoagulation in vascular surgery: Part 1. A retrospective comparison of clinical outcomes for unfractionated heparin versus low-molecular-weight heparin

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Postoperative anticoagulation in vascular surgery: Part 1. A retrospective comparison of clinical outcomes for unfractionated heparin versus low–molecular-weight heparin Carol Ann Gramse, PhD, RN, ANP, CS, Anil Hingorani, MD, and Enrico Ascher, MD The use of postoperative anticoagulation is not uncommon for patients undergoing vascular procedures, whether for adjunctive therapy to the surgical procedure or for resumption of preoperative anticoagulation. Longer postoperative length of stay is necessary to achieve an adequate therapeutic international normalized ratio with traditional protocols that call for the use of unfractionated heparin. We retrospectively examined 195 cases to determine whether low–molecular-weight heparin, specifically enoxaparin, was an effective postoperative replacement for intravenous unfractionated heparin, with the impact on postoperative length of stay. There was no difference in the frequency of complications except for increased incidence of return to surgery for graft thrombosis (n = 11) in patients who received traditional intravenous unfractionated heparin with adjusted-dose warfarin daily (n = 139, P < .02). For all 195 vascular procedures combined, the average postoperative length of stay with use of enoxoparin was shortened with use of enoxaparin (P < .0008). There was a 2-day reduction in the average postoperative length of stay for the femoral-distal procedure group (n = 18, P < .004). In the first part of the article, we summarize our findings and offer new applications and ideas for vascular nurses to consider when postoperative anticoagulation is indicated after vascular procedures. Factors contributing to safe and efficacious postoperative anticoagulation with use of low–molecular-weight heparin, specifically enoxaparin, are presented to the vascular nurse. In the second part, we discuss the roles of members of the vascular team, as well as our experience with use of enoxaparin as implemented in the clinical setting. (J Vasc Nurs 2001;19:42-51)

The use of postoperative anticoagulation is not uncommon for patients undergoing vascular procedures. The vascular nurse should be aware of factors contributing to safe and efficacious postoperative anticoagulation, whether indicated for adjunctive therapy to the surgical procedure or for resumption of preoperative anticoagulation. Patients with peripheral arterial disease (PAD) undergo surgical treatment to correct conditions such as aneurysm, pseudoaneurysm, stenotic lesions, acute arterial occlusion, intimal hyperplasia, and chronically diseased arterial system. In some of these patients, adjunctive long-term anticoagulation is indicated for procedures resulting in extremely disadvantaged run-off, with less than ideal conduits, or with suspected hypercoagulable states. Some patients undergoing revascularization require cessation of warfarin before surgery and resumption after surgery. Patients with a history of atrial fibrillation or flutter, mitral valve replace-

From the Department of Vascular Surgery, Maimonides Medical Center, Brooklyn, New York. Address reprint requests to Carol Ann Gramse, PhD, RN, ANP, CS, Maimonides Medical Center, Department of Vascular Surgery, 4802 Tenth Ave, Brooklyn, NY 11219. Copyright © 2001 by the Society for Vascular Nursing, Inc. 1062-0303/2001/$35.00 + 0 40/1/115784 doi:10.1067/mvn.2001.115784

ment, or prior revascularization surgery require appropriate postoperative management to resume their preoperative level of anticoagulation. There has been increasing pressure for providers and payers to consider the economic aspects of care. One important source of cost has been the postoperative length of stay (LOS) due to anticoagulation. Traditionally, such management after surgery involves the in-hospital use of intravenous unfractionated heparin (UFH), with concurrent use of dose-adjusted warfarin, as the bridge until an adequate international normalized ratio (INR) level is achieved. However, this course of action has contributed to a delay in the postoperative discharge while waiting for the patient to become “therapeutic” on warfarin (Table I). Numerous clinical trials1-4 have reported the safety and efficacy of using a low–molecular-weight heparin (LMWH), specifically enoxaparin. Enoxaparin is approved for clinical use in a variety of venous disorders, such as prevention of deep vein thrombosis (DVT) in patients undergoing hip or knee replacement surgery, abdominal surgery, treatment of DVT without pulmonary embolism (PE) in outpatient settings, and, in conjunction with warfarin, the inpatient treatment of DVT with or without PE (Aventis product literature, Parsippany, NJ, 1999). Furthermore, recent studies have indicated that the possible use of LMWH in acute coronary syndromes suggests that LMWH usage may be extended to areas other than just the venous system.5-7 Despite use of LMWH in prophylaxis and treatment of the venous disorders described above, its role in postoperative vascular surgery remains unclear. Can patients undergoing arterial revascularization who require long-term anticoagulation be treated

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TABLE I. ANTICOAGULATION—PROCESS AND AGENTS USED AFTER SURGERY Normal hemostasis involves a complex relationship between substances that promote clot formation (platelets, von Willebrand factor, activated clotting factors, and tissue thromboplastin) and substances that either inhibit coagulation (prostacyclin, antithrombin III, protein C) or dissolve a formed clot (tissue plasminogen activator). The coagulation system is called a cascade because each activated factor serves as a catalyst, the end result of which is the formation of a clot-forming substance called fibrin. Damage to blood vessels releases thromboplastin, which activates the extrinsic clotting cascade pathway by activating factors VII and X. The intrinsic clotting cascade pathway is activated when factor XII comes into contact with exposed collagen in damaged blood vessels. Once a clot is formed and fibrin is present, the fibrinolytic system is activated. This system regulates the breakdown of clots and keeps the coagulation system from going out of control. Plasmin is the enzyme, which, when activated by plasminogen, breaks fibrin down. All anticoagulants work in the clotting cascade but do so at different points. Heparin works by binding to antithrombin III, which turns off 3 main activating factors: activated II (also known as thrombin, which is the most sensitive to the actions of heparin), activated X, activated IX. Unfractionated heparin (UFH) given subcutaneously; available multidose vials and tubes; dose = 5000 units subcutaneously every 8 or 12 hours or 100 units/h intravenously; adjust dose and interval as per aPPT and disease; monitor platelets. Low–molecular-weight heparin (LMWH), anti-Factor Xa, given subcutaneously; available multidose vials and prefilled syringes; use of LMWH does not require laboratory monitoring of platelets; LMWHs should not be given if hypersensitive to pork products or to heparin; LMWHs cannot be used interchangeably with UFH or other LMWHs; give deep subcutaneous and rotate injection sites. Dosage as per agents as follows: dalteparin (Fragmin) 100 IU/kg twice daily or 200 IU/kg daily; enoxaparin (Lovenox) 1 mg/kg twice daily; tinzaparin (Innohep) 175 IU/kg daily. Warfarin works by interfering with the proper production of vitamin K. The end result is that the vitamin K needed for the production of clotting factors II, VII, IX, and X is dysfunctional, and this causes the clotting factors to be dysfunctional. Give at same time daily; available in scored tabs; usual maintenance dose 2 to 10 mg daily; adjust dose and interval according to INR and or PT (INR preferred). aPPT, Activated partial thrombinplastin time; PT, prothrombin time; INR, international normalized ratio.

as outpatients with LMWH administered in conjunction with warfarin in a manner analogous to its use in the venous disease processes? We examined our experience with postoperative anticoagulation after vascular procedures when 2 methods of anticoagulation were used as a bridge to achieve an adequate INR level. One purpose of our study was to examine whether LMWH was an effective postoperative replacement for intravenous UFH. An additional purpose was to examine the impact on postoperative LOS.

BACKGROUND Whereas abundant literature exists regarding venous disorders and anticoagulants, the literature is sparse regarding postoperative adjunctive anticoagulation after vascular surgery. In a series of studies, Samama3,8-10 reported that patients had less thrombosis when maintained until day 30 with enoxaparin. Vascular graft patency was assessed postoperatively on day 10 by arterio-graphy and by clinical or anatomic assessment. No significant safety differences were noted, including the incidence of hemorrhage or death up to day 30. The authors concluded that enoxaparin is more effective than UFH with similar tolerance when used for the prevention of early graft thrombosis in patients undergoing femorodistal reconstructive surgery. In another series of studies, Farkas4,11 reported no significant differences between the groups for DVT and arterial graft patency.

There were no incidences of PE. Arterial graft patency was assessed by duplex scanning or angiography. Because there were no differences between the groups for frequency of major postoperative bleeding, minor bleeding, and thrombocytopenia that resolved within 3 days and without discontinuation of therapy, the authors concluded that enoxaparin is as safe and effective as UFH in the prevention of DVT for vascular surgery. Neither the Farkas4,11 or Samama3,8-10 studies on use of enoxaparin every 12 hours in patients undergoing vascular surgery reported its use when administered in conjunction with daily warfarin. In our retrospective review of our experience, we attempted to more adequately examine complications in the postoperative clinical use of enoxaparin as the bridge to achieve an adequate INR level in patients after reconstructive vascular surgery. We looked at complications regarding bleeding, thrombosis, stroke, death up to day 30, return to surgery for graft thrombosis or hematoma, and readmission within 30 days for thrombosis or hematoma.

METHODS Our retrospective study was submitted for approval by our Institutional Review Board. It included a review of procedures listed in the vascular surgery service database of an academic medical center. The review included only procedures that resulted in inpatient admissions (eg, carotid endarterectomy, infrainguinal bypass, balloon angioplasty, stenting, patch angioplasty,

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and thrombectomy). The vascular procedures were subdivided into 4 subgroups: femoral-popliteal, femoral-distal, carotid endarterectomy, and other. Other included debridements, arteriovenous fistulas, embolectomies, patch angioplasties, iliofemoral bypasses, and axillobifemoral bypasses. Because enoxaparin can be given on both an inpatient and outpatient basis with full anticoagulation,2,12-16 we compared traditional UFH anticoagulation with the use of enoxaparin as the bridge to achieve adequate INR levels. Patients who required postoperative anticoagulation therapy were identified as having either adjunctive long-term anticoagulation or resumption of levels of long-term anticoagulation before surgery. When the patient was hemodynamically stable, postoperative anticoagulation therapy was initiated 8 to 24 hours after the vascular procedure. On the basis of type of anticoagulation therapy received, patients were assigned to a treatment group of either Type I therapy or Type II therapy. Type I therapy consisted of only traditional intravenous UFH in which the initial UFH dose (100 units/h) was adjusted as per daily activated partial thrombinplastin time (aPTT) levels to maintain a therapeutic goal 1.5 to 2.5 times the control. When the therapeutic PTT goal was achieved, the patient received warfarin daily with dosage adjusted as per daily prothrombin time (PT)/INR. When the therapeutic INR goal of 2.0 to 3.0 was achieved, the UFH was discontinued and the patient was discharged. Type II therapy consisted of either enoxaparin 1 mg/kg every 12 hours subcutaneously, or patients initially received intravenous UFH that was then switched to enoxaparin 1 mg/kg every 12 hours before discharge. Patients also received wafarin daily with dosage adjusted as per daily PT/INR. Patients had outpatient follow-up to discontinue the LMWH when the therapeutic INR goal of 2.0 to 3.0 was achieved. Safety was defined as incidences of bleeding, hematoma, stroke, expiration, thrombocytopenia, return to surgery for graft thrombosis or hematoma, and readmission with 30 days for hematoma or thrombosis. The assessment of arterial graft patency was measured by arterial graft duplex after the procedure at 1 week, 3 months, 6 months, 9 months, 12 months, and every 6 months thereafter. Hematoma was assessed by clinical examination of the surgical site. Elevated INR was defined as >3.5. Minor hemorrhage was measured by a decrease in hematocrit. Major hemorrhage was quantitated by blood transfusions after 8 hours of completion of the procedure. In addition, we attempted to measure the economic impact for the provider and the payer by examining the potential cost benefits related to the LOS. Hospital LOS was measured as actual postoperative LOS after the procedure to discharge from our facility. The complication rates and the average postoperative LOS were compared with both types of anticoagulation therapy. Differences were examined by using the χ2, 2-tailed Fisher exact test, and 2-tailed alternate t test for frequency contingency tables. Significance was set at P < .05.

FINDINGS

Demographics From May 1998 to February 2000, our review of the vascular surgery database revealed 2453 inpatient procedures (eg,

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debridements, arteriovenous fistulas, embolectomies, patch angioplasties, iliofemoral bypasses, axillobifemoral bypasses, greenfield filter placement, carotid endarterectomies, infrainguinal bypasses, such as femoral-arterial, tibial, or femoralpopliteal, balloon angioplasties, and stent placements) were performed. The vascular procedures were subdivided into four subgroups: femoral-popliteal (38%, n = 74), femoral-distal (34%, n = 67), carotid endarterectomy (10%, n = 20), and other (17%, n = 34). The sample consisted of 58.4% men and 41.5% women, with an average age of 71 years, ranging from 41 to 91 years. The most frequently reported comorbidities included hypertension (56%, n = 109), diabetes (50%, n = 97), or both of these conditions (31%, n = 61). The age, sex, and comorbidity distributions were not statistically different between the various subgroups. Postoperative anticoagulation was initiated after 8.3% (n = 205) procedures. However, since 10 patients were given only warfarin and received neither UFH nor LMWH, these patients were not included in the final data analysis (n = 195). Adjunctive therapy was the most frequently indicated reason for postoperative anticoagulation (79%, n = 154), with resumption of preoperative therapy (21%, n = 41) the reason for the remaining patients. Type I therapy (UFH) was given following 71% (n = 139) procedures and Type II (LMWH) therapy was given following 29% (n = 56) procedures.

Safety and Efficacy The most frequently occurring complication was need for transfusion after initiation of anticoagulation therapy (Table II). The most frequent indication for return to the operating room was graft thrombosis, and the indication for readmission was most often wound infection. In all procedures, regardless of the type of anticoagulation treatment, there was no difference in the incidence of complications except for the higher incidence of return to surgery for graft thrombosis in patients who received Type I anticoagulation therapy (P < .02) (Table III). Examination of LOS data for all procedures combined (n = 195) revealed that the average postoperative LOS was shortened by 2 days with use of Type II (LMWH) therapy (P < .0008) (Table IV). During this period at our facility, the mean postoperative LOS was 7 days after the procedure to discharge from our facility for patients who received traditional UFH therapy with adjusted-dose warfarin daily. For patients who received enoxaparin 1 mg/kg every 12 hours subcutaneously and adjusted-dose warfarin daily, the mean postoperative LOS was 5 days after the procedure to discharge. Examination of LOS data by procedure subgroups revealed a trend toward a reduced average LOS in 3 of the subgroups, ranging from 1 to 4 days for patients who received Type II therapy (Table IV). The mean postoperative LOS for the femoraldistal procedure group receiving Type II therapy was significantly shorter by 2 days (P < .004). During this period, at our facility, the mean postoperative LOS for patients who received traditional UFH therapy with adjusted-dose warfarin daily was also 7 days after the femoral-distal procedure to discharge. The mean postoperative LOS was 5 days for patients who had under-

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TABLE II. COMPLICATIONS FOLLOWING VASCULAR PROCEDURES

RBC transfusion INR elevated

Group I Fem-pop (n = 74)

Group II Fem-distal (n = 67)

Group III CEA (n = 20)

Group IV Other (n = 34)

All combined (n = 195)

16

22

1

7

46

3

3

3

1

10

6

4

1

0

11

Return to OR for Thrombosis Hematoma

2

2

0

1

5

Failing graft

1

6

0

1

8

Ischemia

1

2

0

1

4

Debridement

2

1

0

4

7

Dehiscence

0

1

0

0

1

Hematoma

4

2

0

2

8

INR elevated

1

1

0

1

3

Readmit within 30 days for

Stenosis

0

4

0

2

6

Thrombosis

0

2

0

1

3

Infection

3

7

0

3

13

Expiration

0

1

0

2

3

Hematoma

0

0

0

1

1

Stroke

0

0

1

0

1

Fem-pop, Femoral-popliteal; Fem-distal, femoral-distal; RBC, red blood cell; INR, international normalized ratio.

gone femoral-distal procedures who received enoxaparin 1 mg/kg every 12 hours subcutaneously and adjusted-dose warfarin daily. Although the mean postoperative LOS (6 days) for both the femoral-popliteal subgroup and the other subgroup was shorter for patients who received Type II therapy than for patients who received Type I therapy (7 days and 10 days, respectively), these values were not significant. The mean postoperative LOS for the carotid endarterectomy subgroup remained the same regardless of type of anticoagulation received (Table IV).

DISCUSSION

Implications for Research in Vascular Nursing The retrospective review of our experience with postoperative anticoagulation supports the suggestion that LMWH use may be extended to areas other than just the venous system. Since LMWH can be given on both an inpatient and outpatient basis with full anticoagulation,2,12-16 it is feasible that post- operative anticoagulation after vascular reconstruction can be accomplished with LMWH as the bridge to achieve adequate INR levels. In the United States, approved LMWH agents include dalteparin (Fragmin), enoxaparin (Lovenox), and tinzaparin (Innohep). Vascular nurses will play a key role with increased use of any LMWH for postoperative anticoagulation, whether for

adjunctive long-term anticoagulation or resumption of levels of long-term anticoagulation before surgery. Because a review of our experience with postoperative anticoagulation with use of enoxaparin supports the suggestion that LMWH use may be extended to areas other than just the venous system, further randomized, prospective, controlled studies are warranted. Vascular nurses may participate in this research in such areas as benefits related to the patient. Vascular nurses could examine factors that promote patient acceptance of increased use of LMWHs. For example, enoxaparin self-injections may improve patient satisfaction (patient preference for self-care, earlier return home, greater independence, and improved quality of life). Vascular nursing research could explore the difference in patient satisfaction between once-daily and twice-daily LMWHs. In addition, issues of patient anxiety, patient refusal, patient noncompliance, or inability to learn self-injection technique have not been addressed in data reviewed from our experience. Barriers such as cost of LMWH injection, monitoring laboratory results and dose-adjustment orders for warfarin, inconsistency in home care health insurance coverage, variability in requirements of prescription plan coverage, and variability in sufficient supply and/or appropriate dosages in community pharmacies were not addressed in our review. Vascular nursing research can contribute to this area by exploring strategies to

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TABLE III. COMPLICATIONS FOLLOWING VASCULAR PROCEDURES BY TYPE OF ANTICOAGULATION THERAPY RECEIVED N = 195 TYPE I UFH (n = 139)

TYPE II LMWH (n = 56)

31

15

.505

7

3

.587

Thrombosis

11

0

.021*

Hematoma

4

1

.554

Failing graft

8

0

.063

Ischemia

4

0

.255

RBC transfusion INR elevated

P value

Return to OR for

Debridement

7

0

.089

Dehiscence

1

0

.713

6

2

.584

Readmit within 30 days for Hematoma INR elevated

1

2

.199

Stenosis

6

0

.127

Thrombosis

1

2

.199

10

3

.761

Expiration

3

0

.360

Hematoma Stroke

1 1

0 0

.713 .713

Infection

UFH, Unfractionated heparin; LMWH, low–molecular-weight heparin; RBC, red blood cell; INR, international normalized ratio. *Fisher exact test/χ2.

remove barriers to discharge planning that involves LMWH. In Part 2, we will amplify these issues and share strategies we used in our experience with enoxaparin for postoperative anticoagulation in our clinical setting. Vascular nurses could participate in research related to the actual cost analyses between the various LMWHs available, cost-benefit analyses, and cost-utility analyses that account for patients’ quality of life to determine potential cost-benefits. Additional economic appraisal outcomes could examine the impact for the provider and the payer. Actual costs of procedures by postoperative LOS can be examined to compare the potential cost benefits of a reduced average LOS. Patient self-injection is likely to be less costly to the health care system than using home care nurses to administer the injection. Use of enoxaparin twice daily and other once-daily LMWHs may reduce home health care costs by reducing the total number of skilled home care visits as patients learn self-injection techniques during the bridge period pending achievement of an adequate INR level. The administration of anticoagulation therapy, with the concomitant monitoring of its effectiveness, and education regarding precautions associated with the indicated medications and relevant lifestyle modifications are fundamental aspects of nursing care and are especially important in the vascular nurse-patient relationship.

Implications for Patient Monitoring by Vascular Nurses In caring for any patient requiring anticoagulation consisting of heparin (UFH or LMWH) or warfarin, vascular nurses should be aware of contraindications for these medications, which include significant active bleeding, history of hemorrhagic disorders, active peptic ulcer disease, concurrent PE, familial bleeding disorder, known lack of clotting factors, pregnancy, recent cerebrovascular hemorrhage, infections, severe uncontrolled hypertension, and severe renal or hepatic disease.17,18 LMWHs should not be given in the setting of hypersensitivity to pork products or to heparin (Table I). Vascular nurses should be aware that LMWHs cannot be used interchangeably with UFH because they differ in their manufacturing process, molecular weight distribution, anti-Xa and anti-IIa activities, units, and dosage. UFH combines with antithrombin to inactivate coagulation factors. It also inhibits thrombin directly by combining with heparin cofactor II (Table I). UFH has decreased bioavailability as a result of binding with plasma, platelets, and endothelial proteins, thus making frequent laboratory monitoring essential, and required daily at minimum. Standards for vascular nursing practice should outline actions to be taken when subtherapeutic and supertherapeutic activated PTT laboratory results are obtained.

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TABLE IV. AVERAGE LENGTH OF STAY FOR ANTICOAGULATION AFTER VASCULAR PROCEDURES All vascular procedures

Fempop

Femdistal

CEA

n = 139 – × 7 ± .42

n = 50 – × 7 ± .57

n = 49 – × 7 ± .7

n = 12 – × 3 ± .58

n = 28 – × 10 ± 1.1

Anticoagulation

n = 56 – × 5 ± .4

n = 24 – × 6 ± .6

n = 18 – × 5 ± .6

n=8 – × 3 ± .35

n=6 – × 6 ± 1.6

Total P

n = 195 .0008*

n = 74 .24

n = 67 .004*

n = 20 1.0

n = 34 .07

Type I UFH Anticoagulation Type II LMWH

Other

Fem-pop, Femoral-popliteal; Fem-distal, femoral-distal; CEA, carotid endarterectomy. *Fisher exact test/χ2.

Vascular nurses should be aware that LMWHs cannot be used interchangeably with other LMWHs because they differ in their molecular weight distribution, anti-Xa and anti-IIa activities, units, and dosage (Table I). LMWH also exerts its effects on clotting factors, but because it acts higher in the clotting cascade, PTT cannot be relied on to measure therapeutic effect. PT or PTT are not required at recommended doses. LMWH binds less than UFH to the nonspecific plasma proteins, endothelial proteins, and platelets. This increases its bioavailability, thus helping to maintain a consistent level of anticoagulation with each dose. It decreases the risk of bleeding and need for extensive laboratory testing and monitoring of INR. Some LMWHs can be administered daily and others require a twice-daily regimen. This may be important as vascular nurses consider available options with patient resources for access to outpatient skilled nursing services. The official prescribing information from Aventis states that patients with moderate renal impairment (creatinine clearance = 30 to 80 mL/min) who received enoxaparin had apparent clearance values of anti-Xa similar to those of healthy subjects. However, patients with severe renal impairment (creatinine clearance <30 mL/min) had 30% lower clearance values. Therefore, recently, as a result of varying bioavailability and reduced renal clearance of LMWHs in patients with severe renal insufficiency, it has been reported that patients should receive one-half normal doses.19 In our retrospective experience, enoxaparin 1 mg/kg every 12 hours subcutaneously was given, with the usual dose ranging 70 to 80 mg every 12 hours subcutaneously. During the 22-month period examined, no dose adjustments were made as per serum creatinine or creatinine clearance, nor were group comparisons made by serum creatinine or creatinine clearance. Currently, we are calculating the creatinine clearance and are adjusting enoxaparin dosages accordingly. The need to adjust enoxaparin dosage for patients in renal failure has not been fully evaluated and warrants consideration in future prospective research.

Implications for Patient Education by Vascular Nurses Vascular nurses play a valuable role in the education of the patient regarding his or her part in long-term anticoagulation

after vascular reconstructive surgery. In patients for whom postoperative anticoagulation is resumptive, vascular nurses can conduct an assessment of the patient’s long-term anticoagulation knowledge base and focus on knowledge deficits identified. In patients for whom postoperative anticoagulation is adjunctive therapy to the surgical procedure, the vascular nurse can help the patient to realize that long-term anticoagulation is necessary as long as the revascularization procedure is functioning. Patient education will be essential for successful outcomes as increased use of this new protocol occurs. Patients will learn that LMWH usage after surgery combined with readiness for discharge can facilitate earlier discharge to rehabilitation or to home with rehabilitation. Patients may need careful explanation and reassurance that outpatient LMWH injections achieve full anticoagulation similar to inpatient UFH intravenously. Our experience revealed that after peripheral vascular surgery, patients placed on enoxaparin can anticipate a reduced hospital stay of 2 to 4 days. In this recent era of cost-containment, it appears that the use of this type of protocol can be particularly beneficial to hospitals and third-party payers. Patients will need to receive instruction on the proper use and technique for self-injection before they administer an injection for the first time, which often will occur on the day of discharge. Vascular nurses may need to be creative in convincing some patients that they are capable of learning self-injection, which is necessary, albeit for a short period. This period may range from 3 to 8 days but will be determined by their outpatient lab work. Some drug companies provide patient education kits that include a booklet and a video reinforcing key points, as well as a sharps disposal container. Patients will need to be instructed that LMWH twice-daily injections will be necessary only until achievement of a therapeutic INR goal. When this occurs, the LMWH injections can be stopped. The vascular nurse should anticipate and be prepared to address questions regarding warfarin. Since oral anticoagulants interact with many other medications, nurses should be aware of those drugs that potentiate oral anticoagulants (eg, salicylates, anabolic steroids, chloramphenicol, and neomycin) and drugs that decrease the anticoagulant effect (eg, phenytoin, barbitu-

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rates, diuretics, and estrogen). Drug interactions can be initiated during in-hospital patient teaching and reinforced in the home care program. Patients should also be instructed regarding food and drug interactions, as well as foods high in vitamin K. In the ongoing evaluation and management of patients requiring anticoagulation after vascular procedures, inpatient nurses play an essential part in initiating patient teaching concerning appropriate responsibilities regarding his or her role in long-term anticoagulation. Nursing compliance with documentation of patient teaching facilitates coordination and implementation of ongoing patient teaching at discharge into a home care program. Home care nurses assume the role of reinforcing information and extending patient teaching to areas that were not covered during the inpatient stay.

UFH therapy can cause thrombocytopenia, the platelet count should be monitored every 1 to 2 days for inpatients. Home care nurses will require knowledge of targeted INR levels and expected therapeutic goal variations appropriate for patients with arrhythmias or valve replacements (INR = 2.5-3.5). Use of LMWH does not require laboratory monitoring of platelets. Moreover, the use of LMWH will have the additional advantage of reducing the number of coagulation laboratory tests required compared with the number required for follow-up of UFH. The need for phlebotomy with this protocol may be significantly reduced since PT can now be measured with a fingerstick method.

Implications for Nursing Management in Immediate and Ongoing Postoperative Period

In summary, we have shown LMWH, specifically enoxaparin, to be a safe and effective alternative for postoperative anticoagulation after vascular surgical procedures. At the same time, its use can significantly reduce the mean postoperative LOS after vascular reconstructive procedures. In our review, enoxaparin therapy shortened the mean postoperative LOS for all combined vascular procedures (P < .0008). Additional research in this area, including that conducted by vascular nurses, is needed. Vascular nurses play a valuable role in the education of the patient regarding his or her role in long-term anticoagulation after vascular reconstructive surgery. Integrated nursing and physician management, both in the immediate postoperative period and with ongoing monitoring and evaluation, is essential to reduce morbidity and mortality in the provision of cost-effective, quality care to the patient who requires postoperative anticoagulation after vascular reconstruction.

Immediate postoperative period. Our review revealed that postoperative anticoagulation was indicated in 4 out of 5 surgical procedures for adjunctive therapy reasons. This means that immediate and ongoing postoperative assessment of the bypass is essential to ensure graft patency and functioning. Integrated nursing and physician management, both in the immediate postoperative period and with ongoing monitoring and evaluation, is essential to reduce morbidity and mortality in the provision of cost-effective, quality care. In the evaluation and care of the patient in the immediate postoperative period, hypotension and tachycardia can signal signs of hemorrhage. Nurses should immediately report these developments to the physician. These changes can indicate a potential return to the operating room for surgery to explore areas of bleeding at the anastomoses or previously undetected injuries during surgery. Patients may require transfusions to stabilize hemodynamics. In the immediate postoperative period, neurovascular signs are paramount. A pale, cold, pulseless, and painful extremity can signal signs of thrombosis or occlusion of the revascularized area. These changes may result in an unplanned return to the operating room to explore the revascularization surgery. After vascular procedures, nurses should be aware of variations in vital signs and patient monitoring that represent changes in hemodynamic stability. Whereas the surgeon’s postoperative orders usually specify when the anticoagulation will begin, appropriate and accurate nursing assessments contribute to the safe implementation of the order. Vascular nurses must be able to balance accurate and timely initiation of the postoperative anticoagulation with the patient’s overall hemodynamic stability. When anticoagulants drugs are administered, vascular nurses need to monitor patients for evidence of bleeding at numerous sites, including bruises, nosebleeds, hematuria, and bleeding gums. Administration of pain medications as ordered is important to decrease anxiety. Efforts should be made to reduce numerous venipunctures because of prolonged bleeding. Ongoing postoperative period. Collaboration with the physician about physical assessment findings, as well as laboratory data, is crucial. Nurses need to be knowledgeable about laboratory results, especially clotting factors such as PT and PTT times to determine the coagulation status of the patient. Since

CONCLUSIONS

REFERENCES 1. Decousus H, Leizorovicz A, Parent FP, et al. A clinical trial of vena caval filters in the prevention of pulmonary embolism in patients with proximal deep vein thrombosis. N Engl J Med 1998;338:409-15. 2. Levine M, Gent M, Hirsh J, et al. A comparison of low-molecular-weight heparin administered primarily at home with unfractionated heparin administered in the hospital for proximal deep-vein thrombosis. N Engl J Med 1996;334: 677-81. 3. Samama CM, Combe S, Ill P. Are low-molecular-weight heparins useful for the prophylaxis and treatment of arterial thrombi? Haemostasis 1996;26(Suppl 2):57-64. 4. Farkas J, Chapuis S, Combe S, et al. Low-molecular weight heparin vs unfractionated heparin in the prevention of postoperative deep vein and arterial thrombosis after vascular surgery, a prospective randomized trial [abstract]. 16th World Congress of the International Union of Angiology; 1992 Sept 13-18; Paris, France. 5. Goodman SG. Low-molecular-weight heparin in patients with non–ST-segment elevation acute coronary syndrome: role in the emergency department. J Emerg Med 2000;19:S3-S11. 6. Kaul S, Shah PK. Low–molecular-weight heparin in acute coronary syndrome: evidence for superior or equivalent efficacy compared with unfractionated heparin? J Am Coll Cardiol 2000;35:1699-712.

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7. Eikelboom JW, Anand SS, Malmberg K, et al. Unfractionated heparin and low–molecular-weight heparin in acute coronary syndrome without ST elevation: a meta-analysis. Lancet 2000;355:1936-42. 8. Samama CM, Gigou F, Ill P. Low-molecular weight heparin vs unfractionated heparin in femorodistal reconstructive surgery: a multi-center open randomized study. Ann Vasc Surg 1995;9(Suppl):S45-S53. 9. Samama CM, Barre, E Combe S, et al. A pilot study on the use of a low-molecular weight heparin (enoxaparin) in arterial reconstructive surgery. Semin Thromb Hemost 1991;17: 367-70. 10. Samama CM, for the ENOXART Group Study. Low-molecular weight heparin (enoxaparin) versus unfractionated heparin during and after arterial reconstructive surgery: a multi-center randomized study [abstract]. Thromb Haemost 1993;69:546. 11. Farkas J, Chapuis S, Combe S, et al. A randomized controlled trial of a low-molecular weight heparin (enoxaparin) to prevent deep vein thrombosis in patients undergoing vascular surgery. Eur J Vasc Surg 1993;7:554-60. 12. Bergqvist D, Hedner U, Sjorin E, et al. Anticoagulant effects

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of two types of low–molecular-weight heparin administered subcutaneously. Thromb Res 1983;32:381-91. 13. Boneu B. Low molecular weight heparin therapy: is monitoring needed? Thromb Haemost 1994;72:330-4. 14. Kessler CM. Low molecular weight heparins: practical considerations. Semin Hematol 1997;34(Suppl 4):35-42. 15. Wells PS, Kovacs M, Bormanis J, et al. Expanding eligibility for outpatient treatment of deep venous thrombosis and pulmonary embolism with low molecular weight heparin. Arch Intern Med 1998;158:1809-12. 16. Laposata M, Green D, Van Cott E, et al. The clinical use and laboratory monitoring of low molecular weight heparin, danaparoid, hirudin and related compounds, and argatroban. Arch Pathol Lab Med 1998;122:799-807. 17. Gutierrez K. Pharmacotherapeutics: clinical decision-making in nursing. Philadelphia (PA): WB Saunders; 1999. p. 7744-89. 18. Smeltzer S, Bare B. Brunner and Suddarth’s textbook of medical-surgical nursing. 8th ed. Philadelphia (PA): Lippincott; 1996. p. 759. 19. Brater DC. Heparin (low molecular weight): pharmacokinetics and dose adjustment. Available from http://www.uptodate.com. Accessed July 31, 2000.

WRITING AWARD The Journal of Vascular Nursing Article Award honors nurse authors for their efforts to create a publishable manuscript. Manuscripts will be judged for accuracy of content, relevance to vascular nursing practice, and excellence of writing style. All feature articles published in the Journal of Vascular Nursing during the calendar year will be considered for the JVN Article Award. The award recipient will be given a plaque commemorating the award and a cash prize donated by Mosby. The award and cash prize will presented at the annual symposium. Annoucement of the award recipient will appear in the Journal of Vascular Nursing and in SVN...prn.

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JOURNAL OF VASCULAR NURSING

JUNE 2001

Postoperative anticoagulation in vascular surgery: Part 1. A retrospective comparison of clinical outcomes for unfractionated heparin versus low–molecular-weight heparin Contact Hours: 1.0 Test ID: JVN162

Minimum Passing Score: 70% Test Processing Fee: $10.00

OBJECTIVES: 1. Describe the uses of postoperative anticoagulation therapy. 2. Identify different anticoagulation medications used postoperatively. 3. Discuss the impact on length of stay with various anticoagulant uses.

1.

Type I therapy involved: a. UFH dose of 100 u/h until PTT 1.5-2.5 times control b. UFH and warfarin for PTT 5.0 times control c. PTT level 3.5-5.5 times control with combination d. enoxaparin 1 mg/kg q 12 h subcutaneously and daily warfarin

2.

Type II therapy involved: a. UFH dose of 100 u/h until PTT 1.5-2.5 times control b. UFH and warfarin for PTT 5.0 times control c. PTT level 3.5-5.5 times control with combination d. enoxaparin 1 mg/kg q 12 h subcutaneously and daily warfarin Safety was determined by all of the following EXCEPT: a. readmission after 60 days b. return to surgery c. bleeding d. stroke

3.

4.

5.

Which of the following was NOT a characteristic of the population studied? a. average age 71 years b. 50% with COPD c. 50% diabetics d. 56% hypertensive What was the most frequently occurring complication? a. need for pacemaker insertion b. need for nursing home monitoring c. need for transfusion d. need for change in anticoagulant medication

6.

How did the use of enoxaparin affect the length of stay? a. increased LOS by 2 days b. decreased LOS by 2 days c. no change d. other complications impacted the LOS

7.

Contraindications for the use of anticoagulation therapy include all of the following EXCEPT: a. infection b. uncontrolled hypertension c. venous clotting risk d. renal disease

8.

Which medications should be monitored with PTT values? a. UFH b. LMWH c. both d. neither

9.

Which of the following potentiate oral anticoagulants? a. phenytoin b. diuretics c. estrogen d. neomycin

10.

Which of the following decrease the effects of oral anticoagulation therapy? a. salicylates b. anabolic steroids c. barbiturates d. chloramphenicol