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Reality check: use of deep venous thrombosis prophylaxis: from theory to practice #
(Portuguese PDF version)

Antonio César Franco Garcia, Bárbara Vicente de Souza, Dalton Espíndola Volpato, Luciane Mônica Deboni, Marina Vicente de Souza, Roberta Martinelli, Scheila Gechele *

* Centro Hospitalar Unimed (CHU), Universidade da Região de Joinville (UNIVILLE), Joinville, SC, Brazil.

# Study performed at the Centro Hospitalar Unimed, Joinville, Brazil.

Correspondence:
Bárbara Vicente de Souza
Rua Euzébio de Queiros, 287/403, Glória
CEP 89203-100 - Joinville, SC, Brazil
Phone: +55 47 9119.3649
E-mail: barbaralegal@yahoo.com.br

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ABSTRACT

Objective: To assess physicians' knowledge of the indications of chemoprophylaxis for deep venous thrombosis and to compare it to the practical use in their patients.

Methods: Clinical, medicinal and surgical factors for deep venous thrombosis were studied in all patients hospitalized at the Centro Hospitalar Unimed de Joinville, for 40 consecutive days, stratifying risk according to the Norms of Clinical Guidance of the Brazilian Society of Angiology and Vascular Surgery. We verified if patients indicated for chemoprophylaxis for deep venous thrombosis were receiving it. Afterward, the physicians of the patients included in the test answered a questionnaire about deep venous thrombosis.

Results: 239 patients were studied (57 low risk, 124 moderate risk, and 58 high risk for deep venous thrombosis). 76% of the sample (183/239) was not receiving chemoprophylaxis for deep venous thrombosis. 27% of moderate-risk patients (34/124) and 38% of high-risk patients (22/58) received prophylaxis. Of the 91 interviewed physicians, the questionnaire showed that all have the theoretical knowledge of the risk factors and prevention methods of deep venous thrombosis, and 92.3% theoretically know how to use them. Most (57.14%) affirmed always using prophylaxis with risk patients, 38.46% reported knowing the incidence of deep venous thrombosis, and 72.53% had already treated cases of deep venous thrombosis.

Conclusion: Chemoprophylaxis for deep venous thrombosis is underused in patients indicated for receiving it. The physicians showed a good knowledge of the issue, but the reported theory does not correspond to the reality practiced by such professionals.

Key-words: prophylaxis, venous thrombosis, risk factors.

J Vasc Br 2005;4(1):35-41

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The development of the venous thrombus depends on the triad described by Virchow in 1856, which considers venous stasis, hypercoagulable state, and vessel wall injury as responsible for the thrombotic process. After 150 years, the statement remains true, but the knowledge of the relative role of each of these factors increased the understanding of the thrombotic phenomenon, allowing the diagnosis and identification of individuals with higher risk of developing thrombosis, thus aiding in the more rational management of such patients.¹

Deep venous thrombosis (DVT) is a very frequent disease, mainly as complications of other surgical and clinical affections. However, it can also spontaneously occur in apparently healthy people.²

The incidence of the venous thrombosis is estimated to be in 0.6 cases/1,000 inhabitants/year. In special cases, such as the surgical correction of femur fracture, the incidence of DVT diagnosed by phlebography can reach 62.5%, where half is present before the surgical act.³ In a survey made among Brazilian physicians in order to know their opinion on DVT, it was verified that only 15.6% of the 300 interviewed physicians reported having good information on the incidence of this affection in the country. The most cited reason by the interviewees to justify the non-use of prophylaxis is the lack of information, with 34% of answers, followed by the lack of medical knowledge (18.4%), fear of bleeding and hemorrhage (8.3%), and, finally, lack of proper prophylactic stockings (7.5%).⁴

It is known that the occurrence of DVT can lead to severe complications, such as pulmonary embolism and post-thrombotic syndrome.⁵ Approximately 10% of symptomatic pulmonary embolisms cause death within an hour after it begins.⁶ If left without treatment, around 30% of patients initially with a non-fatal pulmonary embolism will have a fatal recurrence.⁷ Venous thromboembolism is cited as the most common cause of morbidity among hospitalized patients in the USA.^7,8 Pulmonary embolism can be the most common cause of avoidable death in hospitals.⁹

The prevalence of venous thromboembolism will probably grow in the future, like the population age is growing. More elderly patients are admitted for major surgical procedures, and many patients, young and elderly, are discharged from medical care (including the day of the surgery) before they are able to ambulate normally.¹⁰

Over the past two decades, the prevention of venous thromboembolism has been widely accepted as an efficient strategy and with a good cost-benefit ratio. American¹¹ and European¹² guidelines have recommended prophylaxis for virtually all groups of hospitalized patients. However, despite the favorable results with preventive methods, some patients have not received prophylaxis routinely.¹³

MATERIALS AND METHODS

A prospective study was performed from May 21 to July 1, 2002, including all patients hospitalized at the Centro Hospitalar Unimed (CHU) in Joinville, Brazil (a private hospital with 115 beds). The study was conducted with the protocol approval by the ethics committee, with the permission of the hospital management and with the patients' consent. Patients were stratified by the different specialties, according to the information on the medical chart. They were divided into two classes, clinical and surgical patients, being considered a clinical patient those who had already been submitted to any type of surgical procedure in the current hospitalization. Exclusion criteria were: patients receiving outpatient care (less than 24 hours of hospitalization), non-acceptance, obstetrical patients, and patients under 18 years old. Each patient included in the study was assessed only once. The patient's acceptance was obtained through a consent form provided by the CHU and handed to the patient by the interviewer.

Each patient was assessed and stratified according to DVT risk. Clinical, surgical and medical factors were surveyed, following a previously made protocol (Table 1). It was filled in according to the medical chart and the interview with the patient. Once the form was filled in, patients were grouped in high, moderate and low risk, according to the Norms of Clinical Guidance of the Brazilian Society of Angiology and Vascular Surgery (SBACV).¹⁴ Following the guidance of these norms, the correct indication of prophylaxis for clinical and surgical patients was assessed (Tables 2, 3, and 4).

Table 1 - List of risk factors for deep venous thrombosis

General

Age

Gender

Days hospitalized

Clinical

Cardiac insufficiency

COPD

Renal insufficiency

Hepatic insufficiency

Cerebral vascular accident

Diabetes mellitus

Nephrotic syndrome

Acute myocardial infarction

Arrhythmia

Inflammatory disease of the colon

Immobilization

Obesity

Auto-immune disease

Dehydration

Varices (CEAP)

Arterial insufficiency

Previous deep venous thrombosis

Infection

Neoplasia

Drugs

Oral contraceptive

Hormonal replacement therapy

Costicosteroid

Surgical

Type of surgery

Time of surgery

Type of anesthesia

 

Table 2 - Risk assessment and prophylaxis indicated for clinical patients

Risk	Patient	Prophylaxis
Low	Any disease	Movement in bed; early ambulation.
Moderate	Patients over 65 years old, affected by clinical diseases with no other risk others	5,000 IU of subcutaneous heparin twice a day; low molecular weight heparin at a low dose once a day.
High	Any disease associated to deep venous thrombosis or previous pulmonary embolism; any disease associated to thrombophilia; diseases associated to other risk factors for deep venous thrombosis; myocardial infarction; cerebral vascular accident, bone marrow injury, ICU patients	Subcutaneous low-molecular-weight heparin at a higher dose; 5,000 IU of subcutaneous heparin three times a day; heparin in modified doses (activated partial thromboplastin time = 1.5 every 6 hours after subcutaneous injection); warfarin - maintain international normalized ratio between 2 and 3.

Adapted from Guidelines for Prevention, Diagnosis and Treatment of Deep Venous Thrombosis, 2001.¹⁴

 

Table 3 - Risk assessment and prophylaxis indicated for surgical patients

Risk	Risk factors	Prophylaxis
Low	Patients under 40 years old with no risk factor	Movement in bed; early ambulation.
Moderate	Major surgery in patients from 40 to 60 years old with no risk factor; surgery in patients under 40 years old taking estrogen	5,000 IU of subcutaneous heparin every 12 hours; subcutaneous low-molecular-weight heparin at a low dose once a day; higher risk of hemorrhage: antithrombotic socks
High	Patients over 60 years old; patients from 40 to 60 years old with additional risk factors; major surgery with previous history of deep venous thrombosis or pulmonary embolism; major amputations; major orthopedic surgeries; major surgeries with neoplasia; major surgeries with hypercoagulability; multiple trauma (pelvis, hip or lower limbs)	Subcutaneous low-molecular-weight heparin at a prophylactic dose once a day; 5,000 IU of subcutaneous heparin every 8 hours; higher risk of hemorrhage: intermittent pneumatic compression.

Adapted from Guidelines for Prevention, Diagnosis and Treatment of Deep Venous Thrombosis, 2001.14

 

Table 4 - Results obtained in each risk group for deep venous thrombosis

Patient	Risk	Prophylaxis
		No		Yes		Total
		n	%	n	%
Clinical	Low	34	100	0	0	34
	Moderate	31	53.4	27	46.5	58
	High	17	56.6	13	43.6	30
Surgical	Low	23	100.0	0	0	23
	Moderate	59	89.4	7	10.6	66
	High	19	67.8	9	31.1	28
Total		183	76.6	56	23.4	239

χ² = 0.12; P = 0.12.

 

Afterward, from May 20 to June 10, 2003, a close-ended questionnaire was applied, which contained questions concerning the opinion, knowledge and conduct for DVT to all physicians giving care to the hospitalized patients included in the study. The physicians answered the questionnaire at the presence of the interviewer, handing it back at the same moment. The questionnaire contained questions related to DVT and three hypothetical cases with alternatives concerning the correct prophylactic conduct to be used. Each hypothetical case was created based on the same classification used to the hospitalized patients. Thus, three cases were created (one high risk, one moderate risk, and one low risk) for DVT focusing clinical specialties and three more cases, following the same classification, for surgical specialties.

The results obtained with the questionnaires were correlated to the practice applied by the physicians on their hospitalized patients. The qui-square test was used for the statistical analysis of dichotomous variables, being considered significant the P values lower than 0.05.

RESULTS

During the period of patients' inclusion in the study, 105 physicians had hospitalized a patient at the CHU. Of these, most, 91 (86.67%), agreed to answer the questionnaire. 10 disagreed to answer the questionnaire, three were not located and one was retired. Of the total of physicians who answered the questionnaire, 52 were surgeons and 39 were clinicians.

All interviewees reported knowing the prevention methods and risk factors related to DVT. Most reported knowing how to use the prevention methods (92.3%) and already having a DVT case among their patients (72.53%). However, 38.46% reported knowing the incidence of DVT in Brazil (Table 5).

Table 5 - Medical knowledge concerning deep venous thrombosis

Medical knowledge	n	%	Surgeons (%)	Clinicians (%)	P
Knows the incidence	35	38.46	36.54	41.02	NS
Knows risk factors	91	100	100	100	NS
Knows prevention methods	91	100	100	100	NS
Knows how to use prevention methods	84	92.30	92.30	92.30	NS
Deep venous thrombosis in patients	66	72.56	63.46	84.61	NS

 

Regarding the frequency of prophylaxis use for DVT, 57.14% reported always using the same prevention methods (Table 6).

Table 6 - Physicians' answers concerning frequency of use of prophylaxis for deep venous thrombosis in their patients

Frequency of use of prophylaxis	n	%	Surgeons (%)	Clinicians (%)	P
Always	52	57.14	53.84	61.54	NS
Frequently	26	28.57	32.69	23.07	NS
Occasionally	6	6.59	5.77	7.69	NS
Rarely	5	5.49	9.61	0	NS
Never	2	2.19	0	5.13	NS

 

239 patients were included in the study, 94 (39.33%) male and 145 (60.67%) female. The patients' age varied from 18 to 100 years old with a mean of 51.87 (± 17.4 years old) and mode of 37 years old. Of the total, 122 (51.05%) were clinical patients and 117 (48.95%) were surgical patients. According to risk stratification, 57 (23.85%) were classified as low risk, 124 (51.88%) as moderate risk and 58 (24.27%) as high risk for DVT (Figure 1). Of the total patients, 56 (23.43%) received prophylaxis and 183 (76.57%) did not. Of the 182 patients who should receive prophylaxis (moderate and high risk), 56 (30.77%) received it and 126 (69.23%) did not receive prophylaxis. Any patient who did not need prophylaxis received it.

Figure 1 - Result of risk stratification for deep venous thrombosis and use of chemoprophylaxis verified at medical prescription for hospitalized patients.

Of the 122 clinical patients, 30 (24.59%) were classified as high risk, 58 (47.54%) as moderate risk and 34 (27.87%) as low risk. Among the clinical patients, of the 88 (72.13%) who needed prophylaxis for DVT, 40 (32.78%) received it. Of the 34 patients who did not need prophylaxis, none received medication. Of the surgical patients, 28 (23.93%) were classified as high risk, 66 (56.41%) as moderate risk and 23 (19.66%) as low risk (Figure 2). Of the 94 patients (80.34%) who needed prophylaxis, 16 (17.02%) received it. Similarly to clinical patients, none of the patients who needed prophylaxis (23) received it. The comparison of the prophylaxis rate used in practice by clinicians and surgeons in patients with absolute indication showed that the clinicians prescribe prophylaxis to their patients more frequently than the surgeons, being this the statistically significant difference (Χ2 = 4.12, P = 0.001) (Figure 3).

Figure 2 - Results obtained in each risk group for deep venous thrombosis in clinical and surgical patients, and prophylaxis rate used in practice by the physicians interviewed.

Figure 3 - Difference in use of prophylaxis for deep venous thrombosis verified at medical prescription among clinical and surgical patients. (χ² = 4.12; P = 0.001).

DISCUSSION

The efficiency of chemoprophylaxis is well documented in the literature.^11,15-17 Meta-analysis studies confirmed that low dosages of heparin reduced the risk of DVT and fatal PE in approximately 66% of cases.¹⁸Prophylaxis is described as being beneficent and, as some patient groups with a high risk for the development of DVT can be identified, it is reasonable and desirable to consider the prevention methods, since they are much superior to the treatment.¹⁵ In our study, however, and in another one by Engelhorn et al.,¹⁹ we can observe that physicians do not submit to prophylaxis the patients with an identified risk for DVT. According to Arnold et al., inadequate prophylaxis is more frequently caused by omission.²⁰ In our study, more than two thirds (69.23%) of patients indicated to receive prophylaxis were neglected and the higher omission occurred in moderate-risk surgical patients. Such data certainly contribute to making the pulmonary thromboembolism still the most common affection in hospitalized patients (1% of hospitalized patients) and the main cause of death, or contributor, in 0.2 and 0.4%, respectively.⁴ In a study made by Menna Barreto et al. at the Hospital das Clínicas, in Porto Alegre, Brazil, it was shown that chemoprophylaxis is employed in only 50% of patients indicated to use it. Another study by Anderson et al. in 16 hospitals in the USA reported that prophylaxis for DVT was administered for approximately one third of high-risk surgical patients.²² In our study, of the 182 patients indicated to receive chemoprophylaxis, only 37.93% of high-risk patients and 27.42% of moderate-risk patients received prophylaxis. The lack of prescription for prophylaxis for patients indicated to receive it was significantly higher in the group of surgical patients, where 83% (78/94) of moderate- and high-risk patients did not receive chemoprophylaxis. In the group of clinical patients, 55% (48/88) of patients indicated for prophylaxis did not receive it (P < 0.05).

This study shows that the non-use of prophylaxis for DVT is not a consequence of the physicians' lack of knowledge of its indications. However, studies have shown that education and awareness programs result in an increase of the use of prophylaxis for DVT in hospitalized patients.⁵ Thus, new strategies must be developed and applied in order to increase the practical use of the physicians' theoretical knowledge in the treatment of their hospitalized patients.

CONCLUSION

Chemoprophylaxis for DVT is being underused by clinicians and surgeons, although the great majority of physicians have shown to have knowledge of prophylaxis and risk factors for DVT. Of the total, among the 81% of patients who presented indication for prophylaxis, 30% received it. The highest lack of prophylaxis is found in moderate-risk patients. Surgeons prescribe prophylaxis less frequently than clinicians.

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