Prevalence and Incidence of Arterial and Venous Thrombosis in Critically Ill Patients.
Authors: Lim Wendy , Crowther Mark A. , Devereaux P. J. , Cook Deborah J. 
Published: October 2019

Abstract
Background: Critically ill patients have multiple risk factors for developing thrombosis, yet little is known about the prevalence and incidence of arterial and venous thrombotic events in this patient population. The development of thrombosis is likely to be frequently unrecognized and thus untreated, which may affect clinical outcomes.
Purpose: To document the prevalence and incidence of clinically recognized thrombotic events in critically ill adult patients.
Methods: We undertook a retrospective chart review of 208 patients from a cohort of 261 critically ill patients admitted to a medical-surgical intensive care unit (ICU) who were enrolled in a prospective cohort study evaluating the prevalence and incidence of deep vein thrombosis (DVT) using twice weekly ultrasound screening. All other thrombotic events were diagnosed based on clinical suspicion and confirmed by conventional diagnostic tests.
Data extraction: We reviewed daily medical records during the patient’s ICU admission for signs and symptoms of thrombosis, and abstracted laboratory and radiologic data.
Results: At the time of ICU admission, ultrasound screening revealed DVT in 7 of 261 patients (prevalence 2.7%, 95% CI 1.1–5.4%) but only 3 cases (42.9%) were clinically suspected. During the ICU stay, 25 patients developed DVT (incidence 9.6%, 95% CI 6.3–13.8%), but only 3 (12.0%) were clinically suspected. Pulmonary embolism was clinically recognized on admission in 4 of 208 patients (prevalence 1.9%, 95% CI 0.5–4.9%); and was diagnosed in 1 patient during ICU stay (incidence 0.5%, 95% CI 0.0–2.6%). For arterial events, 3 of 208 patients were admitted with ischemic stroke, and 3 developed this complication in the ICU (prevalence and incidence 1.4%, 95% CI 0.3–4.2%). Cardiac troponin I was measured at least once in the first 24 hours of admission in 90% of patients. Elevated cardiac troponin I levels were observed in 69 of 208 patients on admission to ICU (prevalence 33.2%, 95% CI 26.8–40.0%) and 15 patients developed elevations in cardiac troponin I during their ICU stay (incidence 7.2%, 95% CI 4.1–11.6%). A diagnosis of an acute coronary syndrome (ACS) (based on troponin I level, and either ECG changes or initiation of treatment for myocardial ischemia) was made in 54 of 208 patients (prevalence 26.0%, 95% CI 20.1–32.5%). Fifteen patients (7.2%, 95% 4.1–11.6%) had elevated cardiac troponin I levels without any further testing. During the ICU stay, the incidence of ACS was 5.3% (95% CI 2.7–9.3%) and isolated elevated troponin I levels were found in 1.9% (95% CI 0.5–4.9%).
Conclusions: Thrombotic events in critically ill patients occurs frequently and may often be unrecognized. Typical diagnostic tests for thromboembolism have not been properly evaluated in the critically ill; moreover, the predictive value for the diagnosis of myocardial infarction has not been determined in these patients. Additional studies evaluating the long term outcome and efficacy of interventions for critically ill patients with thrombotic events is required.