Venous Thromboembolism: Application and Effectiveness of the American College of Chest Physicians 2001 Guidelines for Prophylaxis

Venous thromboembolism (VTE), which encompasses both deep vein thrombosis (DVT) and pulmonary embolism (PE), is a major cause of morbidity and mortality in hospitalized patients.¹ It has been estimated that more than 450,000 patients are hospitalized annually in the United States for VTE.¹ Furthermore, because only one in every three cases of VTE is detected, the actual incidence in the United States may be about 1,350,000 annually.¹ An analysis of data from the International Cooperative Pulmonary Embolism Registry revealed a crude 3-month mortality rate from VTE as high as 17.5%.² Venous thromboembolism has few specific symptoms and is clinically “silent” in most patients, making diagnosis difficult and unreliable.¹ For this reason, prophylactic treatment methods are recommended for patients at risk for VTE.³

In general, the translation of clinical trial data to routine clinical practice is a gradual process involving the creation of evidence-based guidelines that are updated regularly. The Sixth American College of Chest Physicians (ACCP) Consensus Conference on Antithrombotic Therapy (2001) published evidence-based guidelines concerning the use of VTE prophylaxis, which were subsequently updated in 2004.^3,4 The ACCP guidelines recommend mechanical and pharmacologic methods of prophylaxis based on specific VTE risk factors, such as prolonged immobility, cancer, or major surgery.³ Mechanical prophylaxes include thromboembolic deterrent stockings, intermittent pneumatic compression, and inferior vena cava filters. Anticoagulation therapy with low–molecular weight heparin is a common pharmacologic prophylaxis.

Studies have shown that the implementation of these and other guidelines for VTE prophylaxis is inadequate or inconsistent.^5–9 For example, Arnold et al⁷ analyzed 253 VTE cases diagnosed at a Montreal general hospital and showed that 68% of patients with an indication for VTE prophylaxis had not received prophylaxis in accordance with the ACCP 1995 guidelines. Of these patients, 48% had not received prophylaxis at all.⁷

Physicians' nonadherence to the guidelines may be due to factors such as lack of awareness or knowledge of the guidelines, a perception that VTE prophylaxis is ineffective, or the view that VTE is not a significant problem.^10–12 Swan and Spigelman¹¹ found that surgeons may underestimate the post-surgical risk of VTE because of a lack of awareness regarding patient readmissions with VTE. Consequently, VTE is believed to be a rare occurrence.¹¹

Hospital and clinical practice audits as well as educational programs have increased the adoption of new guidelines in some instances.^13–15 New protocols and audit procedures in the Scottish Intercollegiate Guidelines Network on the prevention of VTE was shown to increase the number of at-risk patients who were prescribed the correct prophylaxis, from 55% to 96%.¹⁴ Similarly, a pharmacy-based educational program designed to promote VTE prophylaxis guidelines significantly increased the level of appropriate prophylaxis from 59% to 70% of patients.¹⁵

The objective of this study was to evaluate the extent to which the ACCP 2001 guidelines on VTE prophylaxis are adhered to in clinical practice by determining whether patients admitted to a medical center with an objective diagnosis of VTE had received adequate VTE prophylaxis. Adequate prophylaxis was determined by comparing the prophylaxis regimens used with those recommended by the ACCP 2001 guidelines for specific indications and risk groups.

Methods

Results

Patients and Demographics

Between June 2002 and May 2003, 44 patients at the Nassau University Medical Center (East Meadow, NY) received an objective diagnosis of VTE. The study group comprised 25 (56.8%) medical and 19 (43.1%) surgery patients. There were 29 (65.9%) patients with DVT, 17 (38.6%) patients with PE, and 2 (10.5%) patients with both forms of VTE. Most surgery patients were in the high-risk group (12 [63.2%]). There were no surgery patients in the low-risk group. Most patients (35 [79.5]) had three or fewer risk factors for VTE (Table 1).

Table 1

Baseline Characteristics of Patients With Venous Thromboembolism by Risk Classification According to the American College of Chest Physicians 2001 Guidelines ³ (N=44)

Risk Classification	No. (%) *
▪ Medical Patients	25 (56.8)
□ ≤3 Risk factors	35 (79.5)
□ >3 Risk factors	7 (15.9)
▪ Surgery patients	19 (43.1)
□ Low risk	0
□ Moderate risk	2 (10.5)
□ High risk	12 (63.2)
□ Very high risk	5 (26.3)

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Of the 44 patients with VTE, 17 (38.6%) received inadequate prophylaxis (no prophylaxis at all, inadequate anticoagulation, or incorrect treatment with subcutaneous heparin but no mechanical device) according to the recommendations of the ACCP 2001 guidelines, and were therefore classified as having potentially preventable VTE. Twenty-seven (61.4%) patients were classified as having nonpreventable VTE after receiving prophylaxis in accordance with the ACCP 2001 guidelines. The incidents of VTE and the adequacy of prophylaxis received are summarized in Table 2 by risk group. Most patients with VTE in the very-high-risk surgery group had not received adequate prophylaxis and, therefore, had potentially preventable VTE (4 of 5 patients; >αγϵδ 40 y with multiple VTE risk factors). In general, adequate VTE prophylaxis rates were lower among surgery patients compared with medical patients (52.6% vs 68%, respectively).

Table 2

Patient Diagnosis of Venous Thromboembolism and Adequacy of Prophylaxis Received According to the American College of Chest Physicians 2001 Guidelines ³ (N=44)

	Incidence, No. *			Adequacy of Prophylaxis, No. (%)
Patient Group	DVT	PE	Adequate	Inadequate
▪ Surgery patients	13	9	10 (52.6)	9 (47.4)
□ Low risk	0	0	0	0
□ Moderate risk	0	2	2 (100.0)	0
□ High risk	12	3	7 (58.3)	5 (41.7)
□ Very high risk	1	4	1 (20.0)	4 (80.0)
▪ Medical patients	16	8	17 (68.0)	8 (32.0)
Total	29	17	27 (61.4)	17 (38.6)

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Table 3 presents the details of VTE cases in which VTE prophylaxis was considered inadequate. Six (14%) patients received no prophylaxis, 7 (16%) patients were ordered sequential thromboembolic deterrent stockings but received no anticoagulation therapy, 2 (5%) patients received inferior vena cava filters with either heparin or sequential thromboembolic deterrent stockings but did not receive adequate anticoagulation, and 2 (5%) patients received subcutaneous heparin with no mechanical device.

Table 3

Patients Who Received Inadequate Prophylaxis for Venous Thromboembolism According to the American College of Chest Physicians 2001 Guidelines ³ (N=44)

		Prophylaxis
Indications for Prophylaxis	Risk Factors	Recommended	Received
▪ Medical patients*
□ With risk factors
— Patient 1	Pregnancy; S/P termination of pregnancy; right knee trauma	LMWH as soon as considered safe	None
— Patient 2	Immobilization	IVC filter can be used but not first line (grade 1C)	None
— Patient 3	Immobilization; sickle cell disease	LDUH, LMWH, ES, or IPC	Sequential TEDS
— Patient 4	Immobilization	LMWH or adjusted-dose warfarin: alternative, LDUH	Sequential TEDS due to GI bleeding
— Patient 5	Immobilization	LMWH or adjusted-dose warfarin: alternative, LDUH	Sequential TEDS
□ Trauma
— Patient 6	Immobilization; open head injury	LDUH, LMWH, ES, or IPC	Sequential TEDS
▪ Surgical patients†
□ With risk factors
— Patient 7	Obesity; gastric bypass surgery in the past month; immobilization	IPC device with or without ES	None
— Patient 8	Right femoral angioplasty in the past month	NA	None
□ Trauma with risk factors
— Patient 9	Surgery secondary to trauma; immobilization; central venous catheter; obesity	LMWH as soon as considered safe	IVC filters without adequate anticoagulation
— Patient 15	Exploratory laparotomy	LDUH, LMWH, ES	IVC
□ High risk
— Patient 10	Right AKA in the past month; immobilization	LDUH, LMWH, ES, or IPC	None due to GI bleeding
— Patient 11	Pregnancy	LDUH, LMWH, ES, or IPC	None due to pregnancy
□ Higher risk
— Patient 12	Subtotal colectomy in the past month; prostatic carcinoma; immobilization	LMWH or adjusted-dose warfarin: alternative is LDUH	Sequential TEDS
— Patient 13	Right tibial ORIF in the past month due to trauma; immobilization	LMWH or adjusted-dose warfarin: alternative is LDUH	Sequential TEDS
□ Very high risk
— Patient 14	Laparoscopic cholecystectomy in the past month; carcinoma of the labium; immobilization; obesity	IPC with or without ES; (grade 1A) LDUH or postoperative LMWH may be acceptable alternatives (grade 2A); higher risk patients: ES or IPC with LDUH or postoperative LMWH (grade 1B)	Sequential TEDS
— Patient 15	Exploratory laparotomy in the past month; gastric carcinoma; central venous catheter	LDUH, LMWH, ES, or IPC	IVC filter; subcutaneous heparin 5000 U every 12 hours
— Patient 16	Cystectomy, prostatectomy, and appendectomy in the past month; immobilization; stage II squamous cell carcinoma of the bladder; current chemotherapy	LDUH, LMWH with mechanical method	Subcutaneous heparin 5000 U every 12 hours (ES or IPC)
— Patient 17	Surgery in the past month; breast carcinoma; immobilization; trauma; chemotherapy (tamoxifen)	Pharmacologic with mechanical method	Subcutaneous heparin 5000 U every 12 hours

^{[*] [*] [†]}

Patients and their VTE risk factors are further described in Table 4. The prevalence of VTE risk factors was similar in the potentially preventable and nonpreventable categories, with the exception of surgery, which was more common in the preventable category, and central venous catheter lines, which was more common in the nonpreventable category. The most common risk factor in both categories was immobility. Other common risk factors included surgery, trauma, and cancer. Figure 1 lists risk factors that are commonly overlooked.

Table 4

Patient Risk Factors in Preventable vs Nonpreventable Venous Thromboembolism Based on the American College of Chest Physicians 2001 Guidelines for Prophylaxis ³ (N=44)

Risk Factor	Preventable (n=17) *	Nonpreventable (n=27) *
Cancer	5	8
Central venous catheter	2	10
Deep vein thrombosis	0	2
Immobility	13	20
Obesity	3	5
Pregnancy	2	0
Fracture in lower extremity	2	3
Surgery	11	13
Trauma	5	8

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Figure 1.

Commonly unrecognized venous thromboembolism risk factors.

Comment

The main finding of this study was that a substantial proportion of patients with risk factors for VTE and for whom VTE prophylaxis was indicated had not received prophylaxis in line with the ACCP 2001 guidelines. Had adequate prophylaxis been given, those cases of VTE might have been prevented. In most of the preventable VTE cases, inadequate prophylaxis was a result of the failure of surgeons to prescribe appropriate anticoagulation therapy. Other researchers have reported underuse of VTE prophylaxis in at-risk patients and suboptimal compliance with evidence-based guidelines on prophylaxis for VTE.^{5–9,15–17} Arnold et al⁷ reported that the proportion of patients with VTE who received inadequate prophylaxis despite clinical indications was as high as 68%. In a cross-sectional study of 397 patients admitted to a teaching hospital, Vallano et al⁹ found that adherence to VTE prophylaxis guidelines according to patient risk factors was only 42%. Adherence to guidelines was shown to be higher in the surgical and critical care departments compared with the emergency and medical departments. In contrast, we found that VTE prophylaxis rates were generally lower among surgery patients than among medical patients (52% vs 68%). In particular, 80% of the very-high-risk surgery patients had not received adequate VTE prophylaxis.

A large number of patients (27 [61.4%]) in our study developed VTE despite receiving prophylaxis in line with the ACCP 2001 guidelines. Other studies have reported similar findings, and the incidence has been shown to vary according to the indication for prophylaxis.¹⁸

The most common VTE risk factors in our study patients were cancer, immobility, surgery or trauma. In the study by Vallano et al,⁹ the prevalence of certain VTE risk factors—namely, cancer, immobility, and obesity—was shown to be greater in the preventable VTE group compared with the nonpreventable VTE group. With the exception of surgery and central venous catheter lines, we did not see any differences in the prevalence of VTE risk factors between the two groups.

A comprehensive review of the literature has identified a number of barriers to physician adherence to clinical practice guidelines in general,¹⁰ including a lack of awareness or agreement with the recommendations, or a lack of outcome expectancy. With regard to the ACCP 2001 guidelines, a 2002 a survey of physicians across three medical centers in Seattle demonstrated a lack of basic knowledge regarding the current treatment standards for VTE, indicating the need for further education aimed at increasing physician knowledge and awareness of the current guidelines.¹²

Our study is limited by the small number of patients and the lack of statistical analysis. It should also be noted that in some preventable VTE cases, adequate prophylaxis may not have been received as a result of individual patient variables not investigated in this study. Preliminary data suggest that the implementation of the VTE prevention form (Figure 2) created by the lead author (K.J.S.) and used at Nassau University Medical Center has contributed to a substantial decrease in the number of cases of hospital-acquired DVT and PE since its implementation in July 2005 (Appendix).

Conclusion

We have found that during an 11-month period at the Nassau University Medical Center, a substantial proportion of patients with a diagnosis of VTE and with indications for VTE prophylaxis had not received prophylaxis in accordance with the ACCP 2001 guidelines. It is possible that, with adequate prophylaxis, these VTE cases would have been prevented. However, the incidence of VTE despite the use of adequate prophylaxis suggests the need for a reevaluation of the current guidelines. In addition, further efforts must be made to educate physicians about the current guidelines. Auditing of current practices may be a useful tool to assist in physician education.

Figure 2.

Thrombosis Risk Factor Assessment Physicians Order Sheet as created by the primary investigator (K.J.S.) and in use at Nassau University Medical Center (East Meadow, NY).