Incidence and Risk of Venous Thromboembolism in Critical Care: A Population-based Observational Cohort Study

Venous thromboembolism (VTE) remains an important complication of critical illness, but contemporary population-level estimates of clinically recognized VTE and ICU-associated risk are limited.

To quantify 90-day VTE incidence in ICU vs non-ICU hospitalizations, estimate the adjusted association between ICU exposure and VTE, and identify factors associated with VTE within the ICU cohort.

We conducted a population-based cohort study using linked health administrative data in Ontario, Canada (ICES). We included patients aged ≥16 years and randomly selected one hospitalization per patient. ICU exposure was identified using discharge abstract special care unit codes. Clinically recognized VTE within 90 days was identified using ICD-10-CA diagnosis codes with confirmatory imaging/procedure codes in the same encounter or within ±7 days. We estimated cumulative incidence with death as a competing risk and fit cause-specific Cox models to estimate adjusted hazard ratios (aHRs), including an ICU-restricted model with ICU therapies and ICU length-of-stay.

Among 4,821,130 index hospitalizations, 575,155 (11.9%) had ICU exposure. Ninety-day VTE occurred in 43,913 (0.9%) overall and was higher in ICU vs non-ICU hospitalizations (1.6% vs 0.8%; Gray's test P < 0.001). Hospitalizations involving ICU exposure were associated with higher VTE hazard after adjustment (aHR 1.38, 95% CI 1.34-1.43). In the ICU cohort, higher VTE risk was associated with prior VTE, cancer, recent surgery, prolonged ICU stay, extracorporeal membrane oxygenation, and traumatic brain injury.

Hospitalizations involving ICU exposure were associated with higher 90-day clinically recognized VTE risk, and risk was concentrated in identifiable high-risk ICU subgroups, supporting risk stratification and risk-enriched future studies.