Thrombocytopenia in the Intensive Care Unit—Diagnostic Approach and Management

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Thrombocytopenia often complicates critical illness and is associated with increased morbidity and mortality. Approaching thrombocytopenia is challenging in the intensive care unit (ICU) because of the multifactorial pathogenesis of this disorder. Interpretation of the platelet count course after ICU admission is helpful to narrow down the cause of thrombocytopenia. Whereas a moderate decrease within the first 3 days is rather typical in severely ill patients, an absent or blunted platelet count increase after 5 days indicates continuing critical illness and a worse outcome. A rapid decrease in platelet counts of more than 50% within 1–2 days, especially if occurring after an intermittent rise, requires immediate attention as it may be a symptom of immune-mediated mechanisms, eg, heparin-induced thrombocytopenia. Treatment should target the underlying disease. Platelet transfusions are indicated in bleeding patients, while there is no strong evidence supporting the usefulness of prophylactic transfusions in ICU patients.

Section snippets

Definition of Thrombocytopenia

Thrombocytopenia is commonly defined as a platelet count <150 × 109/L.1 Some authors apply a cut off of 100 × 109/L for ICU patients7 and others further specify platelet counts <50 × 109/L as severe thrombocytopenia.8 Absolute platelet counts alone are not sufficient to characterize thrombocytopenia in critically ill patients; also, the time course of platelet counts provides important information. For example, a platelet count decline of >50% compared to the baseline value can be normal after

Etiology of Thrombocytopenia

Five major mechanisms can result in thrombocytopenia (Table 1). ICU patients commonly develop thrombocytopenia as a result of (1) hemodilution and/or (2) increased platelet consumption due to massive tissue trauma, bleeding, sepsis, or disseminated intravascular coagulation (DIC), and extracorporeal circuits. Less common are (3) decreased platelet production, (4) increased platelet sequestration, and (5) platelet destruction by immune mechanisms.

Importantly, the in vitro artifact of

Platelet Count Course in Different ICU Patient Populations

The dynamics of the platelet count decrease varies between different patient populations. Therefore, the evaluation of a normal, rather “physiologic” platelet count course needs to be specified in the setting of major surgery, trauma, in patients undergoing minor surgery or medical patients. Typical platelet count courses in patients with different underlying morbidities measured at our institution within prospective studies are displayed in Figure 1.

Pathologic Platelet Count Course and Prognosis in ICU Patients

Several clinical studies demonstrated higher morbidity and mortality if the platelet count recovery is delayed beyond day 4.15, 16, 24, 25, 26 For example, the mortality rate in ICU patients with persistent thrombocytopenia at day 14 was 66%24 compared to 16% in patients with normal or increased platelet counts at this stage. Furthermore, 30-day mortality of post-cardiac surgery patients was 1.3% in those with a recovery of platelet counts >100 × 109/L after day 4 and 12% in patients with

Diagnostic Approach of Thrombocytopenia in Critically Ill Patients

Deviations from the “physiologic” platelet course in severely ill patients, as described above, can be used for diagnostic purposes. Based on the patient population and the onset of thrombocytopenia, specific causes of thrombocytopenia become likely (Table 1).

At ICU admission, postsurgical and trauma patients presenting with thrombocytopenia often have a coagulopathy caused by major blood loss, hemodilution, and/or massive tissue trauma. The severity of thrombocytopenia after surgery or trauma

Therapeutic Platelet Transfusion in the Bleeding Patient

Thrombocytopenia is a risk factor for bleeding, and bleeding symptoms in thrombocytopenic patients are an established trigger for therapeutic platelet transfusions.27 There is no fixed platelet count threshold defined in ICU patients to which the platelet count should rise after transfusion. Based on expert opinion, several guidelines recommend to maintain platelet counts >100 × 109/L in massive bleeding27, 28 or if bleeding occurs at dangerous sites, eg, intracranial hemorrhage.

The bleeding

Trauma

Trauma coagulopathy consists of hemodilution, acidosis, hypothermia, loss and consumption of clotting factors and platelets, and hyperfibrinolysis, which all need concomitant therapy. In massively transfused patients, red blood cell concentrates and plasma alone are not able to restore coagulation. While the optimal ratio between red blood cell concentrates, platelet concentrates, and fresh frozen plasma is highly controversial, a recent study controlling for survival bias suggests a survival

Conclusion

Thrombocytopenia is common in ICU patients during the first 4 days and is correlated with the severity of the underlying illness or tissue damage. A poor prognosis is indicated by platelet counts that do not recover or show a progressive decrease 5 days after admission. The most common causes for a low platelet count in ICU patients are sepsis, massive tissue trauma, and DIC. Treatment should target the underlying disease. In most circumstances, the risk of bleeding associated with

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    Conflict of Interest: The authors have no conflict of interest to declare.

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