Deep venous thrombosis in medical–surgical ICU patients: prevalence, incidence and risk factors

Objective

To estimate the prevalence, the incidence, and the baseline and time-dependent risk factors for lower limb deep vein thrombosis (DVT).

Design

Longitudinal cohort study conducted from January 2001 to January 2002.

Setting

Fifteen-bed medical–surgical closed multidisciplinary ICU in Hamilton, Canada.

Methods

We enrolled consecutive consenting patients age ≥ 18 years if they were expected to be in ICU for ≥ 72 hours. Patients were excluded if they had an admitting diagnosis of trauma, orthopedic surgery, cardiac surgery, pregnancy, or if they were undergoing withdrawal of life support. All patients underwent lower limb compression ultrasonography on admission, twice weekly, and with any clinical suspicion of VTE. Investigations for upper limb DVT were performed only if signs or symptoms of DVT were present. We recorded risk factors for DVT on ICU admission and daily thereafter. All patients received VTE prophylaxis. We present prevalence and incidence data as proportions and 95% confidence intervals (CIs). To identify baseline and time-dependent independent risk factors for lower limb DVT, we used backwards stepwise elimination Cox regression analysis.

Results

Of 261 patients, we identified lower limb DVT in seven (2.7%, 95% CI = 1.1–5.5) patients on admission to the ICU, in 25 (9.6%, 6.3–13.8) patients over the course of the ICU stay, and in four (1.5%, 0.4–3.9) following ICU discharge. Upper limb DVTs were found in three patients (1.1%, 0.2–3.3) all related to central venous catheterization. We found two independent baseline risk factors for DVT: personal or family history of DVT (hazard ratio [HR] 3.95 [1.53–10.15]), and dialysis dependent renal failure (HR 3.71, 1.24–11.08). The two time-dependent risk factors were vasopressor use (HR 2.70, 1.03–7.07) and platelet administration (HR 3.08, 1.15–8.20).

Conclusions

In medical–surgical critically ill patients, the prevalence of lower limb DVT at ICU admission was 3%, and the incidence of ICU-acquired DVT was 11%. Patients with an increased risk of ICU-acquired DVT are those with a personal or family history of DVT, pre-ICU dialysis dependence, vasopressor use and platelet administration.