Thrombocytopenia In ICU Patients

Thrombocytopenia is defined as a platelet count less than 150X109/L (1). In ICU setting, the defined cut-off point has been lowered to 100X109/L by some authors, with <10000/mL (16).
Unlike in other situations, absolute platelet count alone does not provide sufficient data in characterizing thrombocytopenia in ICU patients. In such cases, the time course of changes in platelet count is also pivotal. For example, a decline more than 50% compared to the baseline value is considered normal after cardiac surgery, but it is abnormal in the second week of ICU stay. It is also true in patients with no rise in platelet count within 5 days after ICU admission. So, it is essential to use both absolute platelet count and its changes during ICU stay to define thrombocytopenia (17).
As stated before, the incidence of thrombocytopenia in ICU patients ranges between 13% and 60% in various studies (1-5); around 20% in medical ICU patients (18), 35% in surgical ICU patients (19), and 45% in trauma ICU patients (5).
Pathophysiology and etiologies of thrombocytopenia
Pathophysiology of thrombocytopenia, in general, can be defined by five mechanisms: (i) hemodilution (20), (ii) elevated levels of platelet consumption (21-24), (iii) the compromise of platelet production (25, 26), (iv) increased platelet sequestration (27, 28), and (v) increased platelet destruction .
The first two mechanisms are considered as the major etiologies of thrombocytopenia in ICU patients (17, 29) (Table
1).