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Deep venous thrombosis prophylaxis - epidemiological study in a medical school hospital
(Portuguese PDF version)

Ana Luiza Valiente Engelhorn¹, Antônio César Franco Garcia², Maria Fernanda Cassou³, Leonardo Birckholz³, Carlos Alberto Engelhorn⁴

1. Graduate student, Universidade Federal do Paraná (UFPR).
2. Angiologist and Vascular Surgeon.
3. Undergraduate student, School of Medicine of the Pontifícia Universidade Católica do Paraná.
4. Associate Professor, Pontifícia Universidade Católica do Paraná.

Correspondence:
Dra. Ana Luiza Valiente Engelhorn
Rua Deputado Heitor Alencar Furtado, 1720/901
CEP 81200-110 - Curitiba - PR
E-mail: engelhor@bsi.com.br

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ABSTRACT

Objectives: Deep venous thrombosis is a frequent and severe disease that can lead to pulmonary embolism and postthrombotic syndrome. Although there are prevention protocols available to all medical professionals, many patients are not receiving prophylaxis as a routine. The objective of this study is to verify whether the venous thrombosis prophylaxis is being used correctly in a school hospital.

Methods: A prospective study was performed with 228 patients of different specialties, admitted to the Santa Casa de Misericórdia de Curitiba Hospital. They were placed in two groups, clinical (70.18%) and surgical patients (29.82%). We analyzed how prophylaxis was used in each patient. Clinical, pharmacological and surgical factors were researched and these data were used to establish the risk stratification according to the classification recommended by the Brazilian Society of Angiology and Vascular Surgery. The statistical study was carried out in a descriptive manner.

Results: Among the 228 patients, 91 were at low risk for deep venous thrombosis, 70 were at medium risk and 67 showed a high risk. One hundred and ninety-nine (87.28%) patients did not receive venous thrombosis prophylaxis and 29 (12.72%) did. Only 18.57% of the medium-risk patients and 20.90% of high-risk patients received the prophylaxis.

Conclusions: Although the deep venous thrombosis prophylaxis is a proven and well known strategy, it is not being used in patients at potential risk for such disease.

Key words: venous thrombosis, prophylaxis, pulmonary embolism
Palavras-chave: trombose venosa, profilaxia, embolia pulmonar.

J Vasc Br 2002;1(2):97-102.

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INTRODUCTION

Deep venous thrombosis (DVT) is a severe, commonly observed entity that usually occurs as a result of other surgical or clinical disorders. It can also affect previously healthy individuals.¹ DVT can lead to pulmonary embolism and postthrombotic syndrome. Pulmonary embolism is the major cause of preventable deaths in hospitalized patients.² Although the incidence rates of pulmonary embolism and DVT have decreased in the last few decades, they are still a public health problem, especially in the elderly.³,⁴ The European Consensus Statement on the Prevention of Thromboembolism estimates an incidence of 160 cases of DVT and 60 cases of pulmonary embolism each year per every 100,000 inhabitants in western countries.⁵

In the last two decades, deep venous thrombosis prophylaxis has been regarded as a well-established and efficacious strategy. North-American and European group studies have defined detailed recommendations to be used with all kinds of hospitalized patients.⁶,⁷ Although there are prevention protocols available to all medical professionals, many of them do not use them as a routine procedure.⁸

The objective of this study is to verify whether the venous thrombosis prophylaxis is being used correctly and on a routine basis in a school hospital.

PATIENTS AND METHODS

Patients

A prospective study including 228 patients (116 males and 112 females) admitted to the Irmandade Santa Casa de Misericórdia de Curitiba, a general school hospital, was conducted from June 5 to June 21, 2001. The hospital is affiliated with the Pontifícia Universidade Católica do Paraná and has beds for up to 251 patients. The age of patients ranged between 15 and 95 years (mean of 38 years). Patients of different specialties, such as clinical medicine, orthopedics, general surgery, gynecology, urology, and vascular surgery (Table 1), were included in the study. The inclusion criteria for these specialties were literature reports of significant DVT rates described in patients of such specialties, permission of the head of each service for conducting the study and patient agreement to investigation and treatment. The patients were placed in two groups: clinically treated patients (70.18%) and surgically treated patients (29.82%). Surgically treated patients were those who had already been submitted to some surgical intervention during their hospital stay. The exclusion criteria were outpatients, not admitted to the Santa Casa de Misericórdia de Curitiba hospital, and refusal of the patient to participate in the study. No written consent was obtained from the patients; only verbal consent was obtained. Each patient was included in the study and assessed only once.

Table 1 - Definition of abdominal aortic diameter disorders

Specialty	Frequency	Percentage
Gynecology	17	7.46%
General surgery	92	40.35%
Clinical medicine	56	24.56%
Urology	20	8.77%
Orthopedics	24	10.53%
Vascular surgery	19	8.33%
Total	228	100.00%

Methods

Clinical, pharmacological and surgical factors were researched and these data were used to establish the risk stratification according to a previously defined protocol. Table 2 shows the study protocol data obtained from the medical history of each patient and from an interview with the patient. The classification recommended by the Brazilian Society of Angiology and Vascular Surgery (SBACV) was used to define the risk group for each patient⁹ (Tables 3A and 3B).

Table 2 - Risk factors for deep venous thrombosis

	Clinical factors	Medication	Surgical factors
Age Sex Length of stay (days)	Heart failure COPD* Kidney failure Liver failure Stroke Diabetes Nephrotic syndrome Acute myocardial infarction Arrhythmia Inflammatory bowel disease Immobilization Obesity Autoimmune disease Dehydration Varicose veins (CEAP classification) Arterial insufficiency Previous deep venous thrombosis Infection Neoplasia	Oral contraceptives Hormone replacement Corticosteroids	Type of surgery Surgical timing Type of anesthesia

*COPD = Chronic obstructive pulmonary disease

Table 3A - Risk categories for thromboembolic disease in surgically treated patients*

Low risk	Surgeries on patients < 40 years, with no other risk factors; Minor surgeries (< 30 min with no need for prolonged rest) in patients > 40 years without any other risk but age.
Medium risk	Major surgeries (general, urological or gynecological) in patients aged 40-60 years, without additional risk factors; Surgeries on patients < 40 years under estrogen therapy.
High risk	General surgery on patients > 60 years General surgery on patients aged 40-60 years with additional risk factors; Major surgery on patients with past history of DVT or PE or thrombophilia; Major amputations; Larger orthopedic surgeries; Major surgeries on patients with malignant neoplasia; Major surgeries on patients with other hypercoagulable states; Multiple trauma with fracture of the pelvis, hip or lower limbs.

*adapted from Caiafa, 2001⁹

Table 3B - Risk categories for thromboembolic disease in clinically treated patients*

Low risk	Any patient.
Medium risk	Patients > 65 years, confined to bed due to clinical diseases, with no other risk factors.
High risk	Any disease associated with previous DVT or PE; Any disease associated with thrombophilia; Myocardial infarction; Diseases associated with other risk factors for DVT; Stroke; Bone marrow injury; ICU patients.

*adapted from Caiafa, 2001⁹

The correct deep venous thrombosis prophylaxis was analyzed according to SBACV recommendations and according to the literature.⁶,^9-12 The recommendations for low-risk patients are moving the lower limbs while on bed and early walking. For medium-risk patients, the use of low-dose subcutaneous heparin (5,000 IU every 12 hours) or low molecular weight heparin once a day (lowest prophylactic dose), combined or not with graduated compression stockings, is recommended. For high-risk patients, it is recommended that subcutaneous low-dose unfractionated heparin (5,000 IU every eight hours) or subcutaneous low molecular weight heparin once a day (largest prophylactic dose) be used in combination with intermittent pneumatic compression in high-risk patients.

The statistical analysis was carried out in a descriptive manner, and the prophylaxis rate was calculated for each specialty, for clinical and surgical patients and for each group at risk for DVT.

RESULTS

Among the 228 analyzed patients, 91 (39.91%) showed to be at low risk for deep venous thrombosis, 70 (30.70%) were at medium risk and only 67 patients (29.39%) showed a high risk. One hundred and ninety-nine (87.28%) patients did not receive venous thrombosis prophylaxis and 29 (12.72%) did. These rates did not vary when we categorized the patients into clinically treated (12.5% received prophylaxis) and surgically treated (13.24% received prophylaxis).

Only 13 patients (13.68%) with moderate risk and six patients (28.57%) with high risk for DVT received prophylaxis. Therefore, of the 137 patients indicated for pharmacological prophylaxis (medium and high risk), only 27 received it (19.7%). The results are shown in detail in Table 4.

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

		Prophylaxis
Patient	Risk	No	Yes	Total
Clinical	Low	76	2	78
		97.43%	2.57%
	Medium	33	12	45
		73.33%	26.67%
	High	31	6	37
		83.78%	16.22%
Surgical	Low	11	0	11
		100.00%	0.00%
	Medium	24	1	25
		96.00%	4.00%
	High	24	8	32
		75.00%	25.00%
Total		199	29	228

Of all the specialties included in the study, gynecology was the only one that did not use the deep venous thrombosis prophylaxis in any of the patients. Clinical medicine used the prophylaxis in 32.14% of the patients (highest rate). The prophylaxis rate for the analyzed specialties is shown in Figure 1. No statistically significant difference was observed as to the use of prophylaxis between the analyzed specialties. We have to consider that not all the patients received indication for pharmacological prophylaxis; however, the use of prophylaxis even in patients with medium and high risk for venous thrombosis was not satisfactory.

Figure 1 - Rate of prophylaxis in the analyzed medical specialties.

The most widely used prophylaxis regimen consisted of subcutaneous unfractionated heparin (5,000 IU every 12 hours), used in 22 of 29 patients who received the prophylaxis. Low molecular weight heparin (two patients), intravenous unfractionated heparin (two patients) and the combination of more than one drug (three patients) were also used as prophylaxis. The correct prophylactic dose, that is, the maximum dosage of low-dose unfractionated heparin (5,000 IU every eight hours) or of low molecular heparin (enoxaparin 40 mg a day or nadroparin 0.6 ml a day), was not prescribed to any of the high-risk patients who received deep venous thrombosis prophylaxis. Moving the lower limbs while on bed or early walking was not prescribed as prophylactic measure.

DISCUSSION

In the late 1960's, the natural history of venous thromboembolism was better explained by Kakkar et al.¹³ Their study showed that the clinical exam of venous thrombosis, when isolated, is not reliable. By using the fibrinogen uptake test and venography, they found out that 50% or more of the confirmed cases of venous thrombosis did not show any clinical signs. The same study, also using the fibrinogen uptake test, showed that the calf muscle veins are usually the origin of thrombi and that these thrombi can extend into the iliofemoral region. They also found that the venous thrombosis that affects the popliteal, femoral and iliofemoral regions tend to cause pulmonary embolism at a higher frequency. Based on these findings, the prophylaxis of deep venous thrombosis and pulmonary embolism has taken a different path, allowing for the development of consensus and recommendations for each risk group.¹⁴

Nevertheless, venous thromboembolism is still the major cause of sudden death in hospitalized patients and the main cause of death among women during gestation and puerperium.¹⁵,¹⁶ Probably, this occurs due to the lack of information about the incidence of thromboembolism, resulting in its underestimation by physicians. In our study, only 18.57% of 70 medium-risk patients and 20.90% of 67 high-risk patients received prophylaxis. We have to consider that our study included a sample of patients from a single school hospital; therefore, the findings should not be applied to other hospitals before further studies are carried out.

Menna-Barreto et al. have conducted a study at Hospital de Clínicas de Porto Alegre and have shown that pharmacological prophylaxis for DVT is used in only 50% of the patients who receive this recommendation, even at teaching hospitals.¹⁷ A survey carried out by Maffei, in 1998, with 300 Brazilian physicians revealed that only 15.6% were fully aware of the incidence of venous thromboembolism.¹⁸

A study conducted in the United States by Anderson et al., with more than 2,000 patients from 16 hospitals, has shown that only one third of the patients received prophylaxis in spite of presenting several risks for DVT. They have also shown that the prophylaxis was more frequently used by school hospitals and in patients submitted to vascular, abdominal and orthopedic surgeries.²

Guillies et al. have assessed fatal cases of pulmonary embolism during one year and concluded that 56% of the patients did not receive prophylaxis in spite of showing risks for DVT and having no contraindication to the use of anticoagulants.¹⁹ Another study, carried out by Bratzler et al., with patients submitted to thoraco-abdominal surgery, showed that only 38% of 419 patients received prophylaxis.²⁰

A possible reason for not using venous thrombosis prophylaxis in surgically treated patients is the concern of surgeons with the risk of bleeding during the surgery, which can be theoretically triggered by the use of anticoagulants. However, data obtained from meta-analyses and randomized double-blind placebo studies have shown that there is no remarkable increase in bleeding with the use of low-dose unfractionated heparin and, especially, with low molecular weight heparin.^21-25 Another reason for not using the prophylaxis is the financial cost it entails. Nevertheless, Bergqvist et al. and Bick have affirmed that the use of prophylaxis, when correctly indicated, is cost-effective.¹,²⁶ In addition, Golhaber et al. have concluded that most deaths from pulmonary embolism in patients hospitalized because of other diseases mainly occur due to the incorrect use of the prophylaxis rather than its absence. In that study, 384 patients were assessed, of whom 272 exclusively had DVT, 62 had pulmonary embolism and 50 presented DVT and pulmonary embolism concomitantly. Most patients were clinically treated and less than one fourth of them had been submitted to general or orthopedic surgery. Of these patients, 52% received venous thrombosis prophylaxis and 13 deaths were caused by pulmonary embolism. Twelve out of these 13 patients were receiving the prophylaxis correctly.²⁷

Educational programs on venous thrombosis prophylaxis are of paramount importance to health professionals. A prospective study carried out by Anderson et al. has demonstrated an increase from 29% to 52% in prophylaxis in hospitalized patients at risk for venous thrombosis, after the implementation of educational measures that aimed at alerting health professionals to the importance of thromboembolism prevalence. The use of prophylaxis was more frequent in hospitals at which the physicians continually participated in educational programs; being aware of the prevalence of thromboembolism in the hospital these physicians work at encouraged them to use the prophylaxis.²⁸ The authors conclude that, although the efficiency of venous thrombosis prophylaxis has been confirmed by several studies, it is not used by most health professionals. The findings of our brief study confirm this by showing that the prophylaxis has not been used in patients at potential risk for DVT.

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