Ultrasound evaluation of deep venous thrombosis

The incidence of deep venous thrombosis in high-risk Indian neurosurgical patients: Need for early chemoprophylaxis?

INTRODUCTION

Deep venous thrombosis (DVT) is thought to be less common in Asians than in Caucasian population. The incidence of DVT in high-risk groups, especially the neurosurgical (NS) patients, has not been well studied. This leaves no firm basis for the start of early prophylactic anticoagulation within first 5 postoperative days in Indian NS patients. This is a prospective observational study to determine the early occurrence of DVT in the NS patients.

PATIENTS AND METHODS

We screened 137 consecutive high-risk NS patients based on inclusion and exclusion criteria. The femoral veins were screened using Doppler ultrasound on day 1, 3, and 5 of admission into the NS Intensive Care Unit (ICU) at tertiary center from South India.

RESULTS

Among 2887 admissions to NICU 147 patients met inclusion criteria. One hundred thirty seven were screened for DVT. There was a 4.3% (6/137) incidence of DVT with none of the six patients having signs or symptoms of pulmonary embolism. Among the risk factors studied, there was a significant association with femoral catheterization and a probable association with weakness/paraparesis/paraplegia. The mortality in the study group was 10.8% with none attributable to DVT or pulmonary embolism.

CONCLUSION

There is a low incidence of DVT among the high risk neurosurgical population evaluated within the first 5 days of admission to NICU, limiting the need for early chemical thrombo-prophylaxis in these patients. With strict protocols for mechanical prophylaxis with passive leg exercise, early mobilization and serial femoral Doppler screening, heparin anticoagulation can be restricted within the first 5 days of ICU admission in high risk patients.

Venous thromboembolism following microsurgical breast reconstruction: an objective analysis in 225 consecutive patients using low-molecular-weight heparin prophylaxis

BACKGROUND

Free flap breast reconstruction involves major risk factors for postsurgical venous thromboembolism. The main study objectives were (1) to estimate objectively the incidence of symptomatic and asymptomatic lower extremity deep vein thrombosis in patients who received postoperative thromboprophylaxis after free flap breast reconstruction, (2) to evaluate the safety of low-molecular-weight heparin postoperatively, and (3) to assess the incidence of symptomatic pulmonary embolism or sudden death.

METHODS

A cohort study of 225 consecutive patients who underwent abdominally based free flap breast reconstruction at a single cancer center was conducted. The postoperative thromboprophylaxis regimen was based on the American College of Chest Physicians guidelines. A study group of 118 patients systematically underwent bilateral lower extremity duplex ultrasound before hospital discharge to assess objectively the status of the lower extremity deep venous system. A retrospective cohort of 107 women who were not systematically screened for deep vein thrombosis was used for comparison.

RESULTS

The incidence of postoperative deep vein thrombosis confirmed by duplex ultrasound was 3.4 percent in the study group, all events being clinically silent. Bleeding complications in the entire patient sample were estimated at 5.3 percent. Partial flap loss and total flap loss rates were 2.7 and 1.9 percent, respectively. No venous thromboembolism event was diagnosed in the control group.

CONCLUSIONS

This report shows that the objective incidence of deep vein thrombosis was 3.4 percent within 5 postoperative days in this patient population. The authors' findings support the use of triple thromboprophylaxis and demonstrate that low-molecular-weight heparin is a safe and effective method for prevention of venous thromboembolism in this population.

Early Deep Vein Thrombosis: Incidence in Asian Stroke Patients

Introduction: Deep venous thrombosis (DVT) is thought to be less common in Asians than in the Caucasian population. The incidence of asymptomatic DVT in high-risk groups in the Asian population has not been well studied. While DVT incidence among Caucasian stroke patients has been extensively studied and the need for prophylaxis established, the lack of data in Asian patients leaves physicians with no firm basis for adopting prophylactic protocols in the local population. Our aim was to prospectively establish the incidence of early DVT in immobilised stroke patients in a heterogenous Asian population. Materials and Methods: We screened 44 patients with significant hemiplegia from acute stroke. Doppler ultrasound, the currently accepted method of investigation for DVT, was used to study patients on admission and at 1 week post-stroke. While there was no standard prophylactic regime in use, none of the patients received heparin and only 2 were given compression stockings. Results: The incidence of DVT at 1 week was 2.4%. Review at 1 month detected another patient with DVT, bringing the overall incidence at 1 month to 4.8%. This is lower than in Caucasian populations, but is similar to another local study on a different group of high-risk patients. Conclusion: The low incidence of early DVT in hospitalised stroke patients of Asian ethnicity does not justify routine screening for this population. Further research to validate this should ideally include a comparison test for DVT as ultrasound may have inherently lower sensitivity in an asymptomatic population. Key words: Doppler ultrasound

Rapid-inflation intermittent pneumatic compression for prevention of deep venous thrombosis

BACKGROUND

Current treatment regimens that are designed to prevent deep venous thrombosis in patients undergoing orthopaedic procedures rely predominantly on drug prophylaxis alone. The purpose of this randomized clinical study was to evaluate the effectiveness of a mechanical adjunct to chemoprophylaxis that involves intermittent compression of the legs.

METHODS

During a twenty-two month period, 1803 patients undergoing a variety of orthopaedic procedures were prospectively randomized to receive either chemoprophylaxis alone or a combination of chemoprophylaxis and mechanical prophylaxis. Nine hundred and two patients were managed with low-molecular-weight heparin alone, and 901 were managed with low-molecular-weight heparin and intermittent pneumatic compression of the calves for varying time periods. Twenty-four percent of the patients underwent total hip or knee joint replacement. Screening for deep venous thrombosis was performed on the day of discharge with duplex-color-coded ultrasound.

RESULTS

In the chemoprophylaxis-only group, fifteen patients (1.7%) were diagnosed with a deep venous thrombosis; three thromboses were symptomatic. In the chemoprophylaxis plus intermittent pneumatic compression group, four patients (0.4%) were diagnosed with deep venous thrombosis; one thrombosis was symptomatic. The difference between the groups with regard to the prevalence of deep venous thrombosis was significant (p = 0.007). In the chemoprophylaxis plus intermittent pneumatic compression group, no deep venous thromboses were found in patients who received more than six hours of intermittent pneumatic compression daily.

CONCLUSIONS

Venous thrombosis prophylaxis with low-molecular-weight heparin augmented with a device that delivers rapid-inflation intermittent pneumatic compression to the calves was found to be significantly more effective for preventing deep venous thrombosis when compared with a treatment regimen that involved low-molecular-weight heparin alone.

Sonography for Deep Venous Thrombosis

Deep venous thrombosis (DVT) is a one of the most common problems facing the clinician in medicine today. It is often asymptomatic and goes undiagnosed with potentially fatal consequences. Ultrasound has become the "gold standard" in the diagnosis of deep venous thrombosis and with proper attention to technique sensitivity of this test is approximately 97%. An understanding of anatomy, pathophysiology, and risk factors is important. Thrombus formation usually begins beneath a valve leaflet below the knee. Approximately 40% will resolve spontaneously, 40% will become organized, and 20% will propagate. Whether or not a calf vein thrombus is identified, a repeat examination in 7 to 10 days is recommended in patients with risk factors or when deep venous thrombosis is suspected. The three main risk factors for thrombus formation are age greater than 75 years, previous history of deep venous thrombosis, and underlying malignancy. Other diagnostic studies include the contrast venogram, CT or MRI venogram, Tc99m Apcitide study, and the laboratory test D-Dimer. The D-Dimer study is being used more frequently as a screening test with 99% sensitivity in detecting thrombus, whether deep venous thrombosis or pulmonary embolism. However, specificity is only approximately 50% with many conditions leading to false-positive exams. Therefore, a negative examination is useful in avoiding other diagnostic studies, but a positive one may be misleading. Conditions that can lead to a false-positive examination include, but are not limited to diabetes, pregnancy, liver disease, heart conditions, recent surgery, and some gastrointestinal diseases. Like the sonogram, two negative D-Dimer studies a week apart exclude the diagnosis of deep venous thrombosis. Compression sonography with color Doppler remains the best overall test for deep venous thrombosis. It is easy to perform, less expensive than most "high tech" studies, can be performed as a portable examination, and is highly reliable when done properly.

Pathophysiology and diagnosis of deep venous thrombosis

Lower-limb deep venous thrombosis (DVT) affects between 1% to 2% of hospitalized patients. These thrombi disrupt the vascular integrity of the lower limbs and are the source of emboli that kill approximately 200,000 patients each year in the United States. The causes of thrombosis include vessel wall damage, stasis or low flow, and hypercoagulability. These factors favor clot formation by disrupting the balance of the opposing coagulative and fibrinolytic systems. The symptoms and signs of venous thrombosis are caused by obstruction to venous outflow, vascular inflammation, or pulmonary embolization. About 70% of patients referred for clinically suspected venous thrombosis, however, do not have the diagnosis confirmed by objective testing. Among the 30% who have venous thrombosis, about 85% have proximal vein thrombosis, and the remainder have thrombosis confined to the calf. Physicians cannot rely on signs and symptoms to make the diagnosis of DVT and must depend on imaging studies to guide treatment. Patients with proximal vein thrombosis who are inadequately treated have a 47% frequency of recurrent venous thromboembolism over 3 months. In contrast, clinically detectable recurrence occurs in less than 2% of patients with proximal vein thrombosis if an adequate anticoagulant response is achieved. Of the diagnostic procedures for DVT, venography is the only invasive test of proven value, and ultrasonographic (US) studies are the most commonly used noninvasive modaity. Other procedures are occasionally used to diagnose DVT, including impedance plethysmography, computed tomography, and magnetic resonance imaging. US examinations are noninvasive, they are rapidly obtained, and they can be performed serially. In symptomatic patients, venous US is sensitive and specific for proximal DVT; however, US is insensitive to calf vein thrombosis and to asymptomatic DVT occurring after surgery. Patients with symptoms of recurrent DVT also can present a difficult diagnostic problem. Only about 20% to 30% of these individuals actually have the disease; the rest have symptoms arising from chronic venous insufficiency or from any of the causes of lower extremity pain. After an acute episode, up to 50% of patients have compression ultrasound abnormalities for 6 months that are indistinguishable from the original findings of DVT. Hence, there are a significant number of patients and clinical circumstances in which the diagnosis of DVT is difficult. 99mTc-radiolabeled peptides that target the molecular biology of thrombosis should aid in the management of the disease, particularly in asymptomatic patients at high risk, in patients with recurrent symptoms, in patients with active DVT in the calf and/or pelvis, and in patients with intermediate- or low-probability lung scans.

Imaging evaluation of suspected pulmonary embolism

Venous thromboembolism (VTE) is a common disorder that is difficult to diagnose clinically but carries significant morbidity and mortality if untreated. Additionally, although demonstrated to be of benefit in cases of proven deep vein thrombosis (DVT) and pulmonary embolism (PE), anticoagulation therapy is not without risk. Because the clinical exam is known to be unreliable for the detection of both DVT and PE, many imaging modalities have been used in the diagnostic imaging algorithm for the detection of VTE, including chest radiography, ventilation/perfusion (V/Q) scintigraphy, pulmonary angiography, and recently, spiral computed tomography (CT) and magnetic resonance imaging (MRI). Chest radiographic findings in acute PE include focal oligemia, vascular enlargement, atelectasis, pleural effusions, and air space opacities representing pulmonary hemorrhage or infarction. The chest radiograph can occasionally be suggestive of PE but is more often nonspecifically abnormal. The main use of the chest radiograph in the evaluation of suspected PE is to exclude entities that may simulate PE and to assist in the interpretation of V/Q scintigraphy. Lower extremity venous compression ultrasonography (CU) is both sensitive and specific for the diagnosis of femoropopliteal DVT, and the value of negative CU results has been established in outcomes studies. However, the reliability of CU for the detection of isolated calf vein thrombosis is not well established, and the clinical significance of such thrombi is debatable. Additional methods such as color and spectral Doppler analysis are also useful in the diagnostic evaluation of DVT but are best considered as adjuncts to the conventional CU examination rather than as primary diagnostic modalities themselves. Compression ultrasonography and Doppler techniques are useful in the evaluation of suspected upper extremity DVT; spectral Doppler waveform analysis is particularly useful to assess for the patency of veins that cannot be directly visualized and compressed with conventional gray-scale sonography. V/Q scintigraphy has been the initial modality obtained in patients suspected of PE for a number of years. Although many studies have investigated the role of V/Q scintigraphy in the evaluation of VTE, the Prospective Investigation of Pulmonary Embolism Diagnosis (PIOPED) study has provided the most useful information regarding the utility of V/Q scintigraphy in this setting. A high probability scan interpretation is sufficient justification to institute anticoagulation, and a normal perfusion scan effectively excludes the diagnosis of PE. A normal/near normal scan interpretation also carries a sufficiently low prevalence of angiographically proven PE to withhold anticoagulation. Although the prevalence of PE in the setting of low probability scan interpretations is low and several outcomes studies have demonstrated a benign course in untreated patients with low probability scan results, patients with inadequate cardiopulmonary reserve do not necessarily have good outcomes. Such patients deserve more aggressive evaluation. Patients with intermediate probability scan results have a 20% to 40% prevalence of angiographically proven PE and thus require further investigation. The radionuclide investigation of DVT includes such techniques as radionuclide venography and thrombus-avid scintigraphy. Although these methods have not been as thoroughly evaluated as CU, studies thus far have indicated encouraging results, and further investigations are warranted. Pulmonary angiography has been the gold standard for the diagnosis of PE for decades. Studies have indicated that angiography has probably been underutilized by referring physicians for the evaluation of suspected PE, likely because of the perception of significant morbidity and mortality associated with the procedure. (ABSTRACT TRUNCATED)

Role of Duplex Imaging in Intermnediate Category Ventilation Peffusion Scans

Clinical diagnosis of pulmonary embolus (PE) is difficult. Pulmonary angiography is still the gold standard for diagnosing PE, and ventilation perfusion (VQ) lung scans are used as a screening test. With normal VQ scans, PE can be ruled out. High probability VQ scans have high positive accuracy. The authors conducted a retrospective analysis of 45 patients who underwent intermediate VQ scans. Of the 45 patients who had intermediate VQ scans performed, 37 (82%) had venous duplex imaging (VDI) conducted, with 7 found to be positive for deep vein thrombosis. Of the 45 patients who had intermediate VQ scans performed, 12 (27%) had pulmonary angiograms performed, 7 (58%) of which were positive for PE. Six of these seven patients also had VDI conducted, all of which were negative. In total, of the 22 patients found to have a clinical discharge diagnosis of PE, 13 had either VDI studies or pulmonary angiographies positive for PE. These results indicate that a positive VDI study substantiates a diagnosis of PE. However, negative VDI study does not rule out pulmonary embolus.

Noninvasive venous testing in the diagnosis of pulmonary embolism: the impact on decisionmaking

PURPOSE

To characterize the use and utility of lower extremity noninvasive venous testing (NIVT) in the diagnosis of pulmonary embolism (PE).

METHODS

The study is a retrospective case series of consecutive patients in whom PE was suspected who were referred to a large, urban tertiary care center for NIVT. The main outcome measures of the study were the rate of positive results of NIVT, the amount of new information provided by NIVT, and the frequency of management changes that were attributable to NIVT.

RESULTS

Forty-one of 450 patients (9%) had deep venous thrombosis (DVT) by NIVT. The prevalence of DVT by NIVT among patients not evaluated by ventilation/perfusion (V/Q) scanning was 8%. The prevalence of DVT by NIVT among patients with a high-probability V/Q scan result before NIVT was 39%, but no management decisions in this group were based on a positive NIVT result and only two decisions were based on negative NIVT results. The prevalence of DVT according to NIVT among patients who had a negative "diagnostic" (low, or very low probability, or normal) result of V/Q scan before NIVT was 2%. The overall frequency of management changes attributed to NIVT was only 2.5%. In the remaining 97% of patients, management was determined by the result of V/Q scanning or of subsequent pulmonary arteriography.

CONCLUSIONS

In patients in whom PE is suspected, results of NIVT are usually negative for acute DVT. Management decisions are almost always based on V/Q scan or results of pulmonary arteriography and not on NIVT. The utility of NIVT to identify DVT in these patients appears limited, and a more selective approach to its application for the diagnosis of PE should be considered.

Diagnosis of cancer-associated vascular disorders

BACKGROUND

Unexplained thromboembolism may be an early indicator of the presence of a malignant tumor before signs and symptoms of the tumor itself become obvious.

METHODS

A survey of the MEDLINE data-base was conducted concerning cancer-associated vascular disorders and their role in the diagnosis of hidden cancer. The spectrum of vascular disorders heralding occult cancer and the associated laboratory abnormalities were scrutinized.

RESULTS

Deep venous thrombosis was associated with a significantly higher frequency of malignancy during the first 6 months after diagnosis. Malignancies were found using simple clinical and diagnostic methods; additional screening was not cost-efficient. Other signs associated with deep venous thrombosis that increased the probability of an occult cancer were age older than 50 years, multiple sites of venous thrombosis, associated venous and arterial thromboembolism, thromboembolism resistant to warfarin therapy, and paraneoplastic syndrome. Among vascular syndromes, only cutaneous leukocytoclastic vasculitis presenting after the age of 50 years was consistently associated with cancer. Preliminary data with an antigen specific to tumor tissue, the cancer procoagulant, suggested its possible role as a tumor marker. The sensitivity for all samples analyzed from cancer patients was 80% and the specificity was 83%.

CONCLUSIONS

Data from the literature enabled us to outline clinical clues that might distinguish patients with cancer-associated vasculopathies from those unaffected by malignancies. Preliminary data with an antigen specific to tumor tissue, the cancer procoagulant, suggested its possible role in detecting early stage cancer. However, large-scale prospective studies are not currently available to evaluate the role of these clues and laboratory assays in the diagnosis of early stage cancer.

Aprotinin decreases blood loss in patients undergoing revision or bilateral total hip arthroplasty

Two recent studies have shown decreased blood loss in patients given aprotinin undergoing primary hip replacement surgery. Because patients undergoing bilateral (bTHA) or revision total hip arthroplasty (rTHA) suffer more blood loss than those undergoing primary THA, we studied consecutive patients undergoing bTHA or rTHA who were randomized to receive either a blinded solution of 3.8 x 10(6) Kallikrein inactivation units (KIU) aprotinin (n = 29) or placebo (n = 24) throughout the surgical procedure. Total blood loss, measured as intraoperative suction losses, weight of sponges, and postoperative volumetric drainage, was compared between groups. Aprotinin patients had significantly less total blood loss 1498 +/- 110 mL (mean +/- SEM) versus 2096 +/- 223 (P = 0.022), and transfused patients in the aprotinin group received fewer packed red blood cells than placebo-treated patients (confidence interval for the difference -1.69, -0.07). In addition, assessment of biochemical markers of hepatic and renal function did not disclose any clinically important differences between groups. Patients were also assessed for development of deep venous thrombosis (DVT) by preoperative and predischarge bilateral lower limb compression ultrasound. None of the aprotinin-treated patients and three placebo-treated patients demonstrated DVT. Unless this trend for decreased DVT with aprotinin can be confirmed, it is questionable whether the slight reduction in blood loss justifies routine use of this expensive drug.

Thromboembolism in cancer. Changing trends

The multitude of classic manifestations of paraneoplastic thromboembolism (TE), including new aspects, are reviewed. This emphasizes the complexity of the situation that the physician faces in dealing with paraneoplastic TE. Unexplained TE may serve as a hint for the presence of a hidden tumor. However, efforts to uncover such an underlying malignancy often are unrewarding. The view has been expressed that it is inappropriate to conduct an extensive search for an occult neoplasm unless there are more specific indications. A recent study defined clues that might separate patients with TE and occult cancer from those unaffected by a malignant neoplasm. The study of the hemostatic alterations in patients with cancer underscores the triple role of cancer cells in the pathogenesis of TE: injury to the endothelial lining of blood vessels, activation of platelets, and activation of blood coagulation and depression of anticoagulant functions. The failure of standard anticoagulant treatment in many instances is better understood. Novel approaches to treatment include low-molecular-weight heparin(s) for long-term administration or, alternatively, the initial placement of a Greenfield filter in the vena cava instead of anticoagulant therapy. Either of these may provide superior results in comparison to standard heparin treatment.