Thrombocytopenia in the critically ill: prevalence, incidence, risk factors, and clinical outcomes.

Purpose: The aim of this cohort study was to describe the prevalence, incidence, and risk factors for thrombocytopenia in the intensive care unit (ICU) and to evaluate the impact of thrombocytopenia on mortality with further comparisons amongst major diagnostic categories.

Methods: Patients admitted to the ICU from 1997-2011 for cardiac, medical, surgical, and trauma conditions were included. The presence of a platelet count < 100 × 10(9)·L(-1) on admission day or its appearance during ICU stay were considered as prevalent and incident thrombocytopenia, respectively. Risk factors for thrombocytopenia and the influence of thrombocytopenia on mortality were also analyzed.

Results: This study included 20,696 patients. Prevalent and incident thrombocytopenia occurred in 13.3% and 7.8% of patients, respectively, with associated mortality rates of 14.3% and 24.7%, respectively, compared with 10.2% in the group with normal platelet count (P < 0.001). After adjustments, thrombocytopenia remained associated with an increased risk of mortality (odds ratio 1.25; 95% confidence interval 1.20 to 1.31; P < 0.001). The greatest impact of thrombocytopenia on mortality was observed in the cancer, respiratory, digestive, genitourinary, and infectious diagnostic categories. Independent risk factors included age, female sex, admission platelet counts and hemoglobin, mechanical ventilation, days of hospitalization prior to ICU admission, liver cirrhosis, hypersplenism, coronary bypass grafting, intra-aortic balloon pump placement, acute hepatitis, septic shock, and pulmonary embolism or deep vein thrombosis.

Conclusions: Thrombocytopenia in the ICU is associated with an independent risk of mortality that varies greatly depending on diagnostic admission category.