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Burden of Illness in ThromboEmbolism in Critical Care (BITEC) study: a multicenter Canadian study


Medical–surgical critically ill patients are at risk of venous thromboembolism (VTE) during their stay in the intensive care unit (ICU). The rates of deep vein thrombosis (DVT) detected by screening ultrasonography (10%), and DVT and pulmonary embolism (PE) identified at autopsy (20%), suggest that many VTE events are clinically undetected. The burden of illness associated with VTE (DVT and/or PE) diagnosed during critical illness is unclear.


The primary objective of this study was to estimate the prevalence and incidence of diagnostically confirmed DVT and PE in medical–surgical ICU patients. The secondary objective was to examine VTE prophylaxis longitudinally, estimating the proportion of VTE events associated with prophylaxis failure versus failure to implement prophylaxis. The tertiary objective was to estimate the morbidity and mortality outcomes of patients with VTE.


A 1-year retrospective observational multicenter cohort study of patients admitted to an ICU during 2000.


Twelve university-affiliated closed medical–surgical ICUs in eight cities in three provinces.


We identified medical–surgical adult ICU patients who had either upper or lower limb DVT or PE in the 24 hours preceding ICU admission up to 48 hours post-ICU admission (prevalent cases), and any time during the ICU admission, or up to 8 weeks following ICU discharge (incident cases). DVT was diagnosed by compression ultrasound of the upper or lower extremity, or venography. PE was diagnosed by ventilation perfusion lung scan, chest computerized tomography, pulmonary angiogram, echocardiogram, S1Q3T3 on EKG, or autopsy. Based on a priori criteria, patients were categorized as definite or indeterminant VTE.


Among over 10,000 patients, 252 patients had definite or indeterminant VTE; these patients were 62.5 (16.7) years of age, with an APACHE II score of 17.6 (7.9). The range of diagnostically confirmed VTE events across centers was wide.

Among patients with incident VTE, either anticoagulant or mechanical prophylaxis occurred in 72.2% (70.2–74.1%) of eligible ICU days. The median ICU length of stay was similar for patients with DVT and PE (DVT, 4.0 days [interquartile range 2, 13]; PE, 4.0 days [interquartile range 2, 7]). ICU mortality was 17.9% and hospital mortality was 30.4% for patients with VTE. Intravenous anticoagulation with unfractionated heparin was the predominant treatment, and treatment complications were infrequent.


The burden of illness associated with diagnostically confirmed DVT and PE in medical–surgical critically ill patients is low in comparison with higher event rates of 10–20% detected by screening ultrasonography and autopsy studies. Most VTE events, although underdiagnosed, are associated with prophylaxis failure rather than failure to prophylax. More active implementation of VTE prevention strategies are needed in the ICU, as well as more rigorous evaluation of VTE prevention strategies.

Table 1


This study was funded by an unrestricted grant from Pharmacia, Inc., the Physicians' Services Incorporated of Ontario, and the Ontario Thoracic Society.

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Patel, R., Griffith, L., Mead, M. et al. Burden of Illness in ThromboEmbolism in Critical Care (BITEC) study: a multicenter Canadian study. Crit Care 8 (Suppl 1), P103 (2004).

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