Prediction of Symptomatic Venous Thromboembolism in Critically Ill Patients: The ICU-Venous Thromboembolism Score.

OBJECTIVES

To identify risk factors and develop a prediction score for in-hospital symptomatic venous thromboembolism in critically ill patients.

DESIGN

Retrospective cohort study.

SETTING

Henry Ford Health System, a five-hospital system including 18 ICUs.

PATIENTS

We obtained data from the electronic medical record of all adult patients admitted to any ICU (total 264 beds) between January 2015 and March 2018.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Symptomatic venous thromboembolism was defined as deep vein thrombosis, pulmonary embolism, or both, diagnosed greater than 24 hours after ICU admission and confirmed by ultrasound, CT, or nuclear medicine imaging. A prediction score (the ICU-Venous Thromboembolism score) was derived from independent risk factors identified using multivariable logistic regression. Of 37,050 patients who met the eligibility criteria, 529 patients (1.4%) developed symptomatic venous thromboembolism. The ICU-Venous Thromboembolism score consists of six independent predictors: central venous catheterization (5 points), immobilization greater than or equal to 4 days (4 points), prior history of venous thromboembolism (4 points), mechanical ventilation (2 points), lowest hemoglobin during hospitalization greater than or equal to 9 g/dL (2 points), and platelet count at admission greater than 250,000/μL (1 point). Patients with a score of 0-8 (76% of the sample) had a low (0.3%) risk of venous thromboembolism; those with a score of 9-14 (22%) had an intermediate (3.6%) risk of venous thromboembolism (hazard ratio, 6.7; 95% CI, 5.3-8.4); and those with a score of 15-18 (2%) had a high (17.7%) risk of venous thromboembolism (hazard ratio, 28.1; 95% CI, 21.7-36.5). The overall C-statistic of the model was 0.87 (95% CI, 0.85-0.88).

CONCLUSIONS

Clinically diagnosed symptomatic venous thromboembolism occurred in 1.4% of this large population of ICU patients with high adherence to chemoprophylaxis. Central venous catheterization and immobilization are potentially modifiable risk factors for venous thromboembolism. The ICU-Venous Thromboembolism score can identify patients at increased risk for venous thromboembolism.