Validation of an inexpensive B-mode ultrasound device for detection of deep vein thrombosis

Resident performed two-point compression ultrasound is inadequate for diagnosis of deep vein thrombosis in the critically III

Doppler ultrasonography is a standard in diagnosis of deep vein thrombosis (DVT) but is often delayed. Clinician-performed focused vascular sonography (FVS) has proven to accurately diagnose DVT in the ambulatory and emergency room settings. Whether trained medical residents can perform quality FVS in the critically ill is unknown. Medical residents were trained in a 2-hour module in FVS assessing for complete compressibility of common femoral and popliteal veins. Residents imaged consecutive medical ICU and intermediate care patients awaiting comprehensive, sonographer-performed and radiologist-interpreted examinations. Sensitivity, specificity, positive and negative predictive values of the focused examination were calculated against the comprehensive study. Fleiss Kappa (κ), the degree of agreement between resident and radiologist, was calculated. Time savings was measured. Nineteen residents performed 143 studies on 75 patients. Twelve patients had above-the-knee DVTs, a prevalence of 16 %. All 6 common femoral and 7 of 9 popliteal vein DVTs were identified. None of 6 isolated superficial femoral DVTs were identified. Sensitivity for above-the-knee DVT was 63 %, specificity 97 %. Sensitivity for common femoral and popliteal DVT was 86 %, specificity 97 %. Residents showed substantial agreement with radiologists for diagnosis of DVT (κ = 0.70, SE 0.114, p < 0.001).Time from order of a formal ultrasound to a radiologist's read averaged 14.7 h. The two-point compression ultrasound method demonstrated insufficient sensitivity in a cohort of critically ill medical patients due to a high-incidence of superficial femoral DVT. However, residents demonstrated substantial agreement with radiologists for the diagnosis of clinically relevant DVT after a 2-hour course. FVS should include the superficial femoral vein and is associated with a significant time savings.

Accuracy of ultrasonography performed by critical care physicians for the diagnosis of DVT

BACKGROUND

DVT is common among critically ill patients. A rapid and accurate diagnosis is essential for patient care. We assessed the accuracy and timeliness of intensivist-performed compression ultrasonography studies (IP-CUS) for proximal lower extremity DVT (PLEDVT) by comparing results with the formal vascular study (FVS) performed by ultrasonography technicians and interpreted by radiologists.

METHODS

We conducted a multicenter, retrospective review of IP-CUS examinations performed in an ICU by pulmonary and critical care fellows and attending physicians. Patients suspected of having DVT underwent IP-CUS, using a standard two-dimensional compression ultrasonography protocol for the diagnosis of PLEDVT. The IP-CUS data were collected prospectively as part of a quality-improvement initiative. The IP-CUS interpretation was recorded and timed at the end of the examination on a standardized report form. An FVS was then ordered, and the FVS result was used as the criterion standard for calculating sensitivity and specificity. Time delays between the IP-CUS and FVS were recorded.

RESULTS

A total of 128 IP-CUS were compared with an FVS. Eighty-one percent of the IP-CUS were performed by fellows with <2 years of clinical ultrasonography experience. Prevalence of DVT was 20%. IP-CUS studies yielded a sensitivity of 86% and a specificity of 96% with a diagnostic accuracy of 95%. Median time delay between the ordering of FVS and the FVS result was 13.8 h.

CONCLUSIONS

Rapid and accurate diagnosis of proximal lower extremity DVT can be achieved by intensivists performing compression ultrasonography at the bedside.

Ultrasound in the detection of venous thromboembolism

Venous thrombosis is a common disease process leading to tens of thousands of deaths per year. Despite prophylactic efforts, venous thromboembolic disease is a common and serious complication in critical care patients. Difficulty and delay in obtaining diagnostic imaging studies to rule out deep venous thrombosis is exacerbated by increased susceptibility that critically ill patients have to thromboembolism. Lower extremity venous ultrasound use by clinicians has been well studied and has proven both reliable and efficient. Evaluation of the upper extremities can be more challenging and requires a higher degree of technical skill. However, both can be integrated into an overall scheme of prevention, screening, and rapid diagnosis of thromboembolic disease and its complications. This article delves into available literature and describes performance of both applications in a critical care setting.

Lower-extremity Doppler for deep venous thrombosis--can emergency physicians be accurate and fast?

Clinical diagnosis of lower-extremity (LE) deep venous thrombosis (DVT) requires confirmation by an imaging study before committing the patient to anticoagulation therapy. Studies have shown that demonstrating compressibility of leg veins under ultrasound is accurate for ruling out DVTs when performed by vascular specialists. Although LE Doppler has become the preferred test for diagnosing DVTs, it is not always available 24 hours per day.

OBJECTIVES

To evaluate the accuracy and speed with which emergency physicians (EPs) could perform LE color duplex ultrasonography for the detection of DVT.

METHODS

Patients presenting to an urban community emergency department (ED) between August 1, 1998, and March 3, 1999, were enrolled into this prospective study. The EPs, who underwent brief and standardized training, scanned patients at high risk for DVT with leg pain, swelling, or both. Physicians performed color duplex ultrasound examinations with compression at the common femoral and popliteal veins. The time until completion of the ED scan was recorded with a standardized method. The vascular laboratory performed a complete duplex ultrasound examination within eight hours.

RESULTS

One hundred twelve patients were enrolled in the study, with 34 positive for DVT. The median examination time was 3 minutes 28 seconds (95% CI = 2 min 45 sec to 4 min 2 sec; IQR 3 min 9 sec). Times ranged from 1:02 to 18:20 minutes. The ED results had a high correlation with vascular laboratory studies, giving a kappa of 0.9 and a 98% agreement (95% CI = 95.4% to 100%).

CONCLUSION

Emergency physicians can perform LE duplex ultrasound examinations accurately and quickly.