Definition of thrombocytopenia: platelet count < 100,000 per µL
Exclusions:
(1) previous history of thrombocytopenia
(2) hypersplenism
(3) platelet count < 100,000 per µL when admitted to the ICU
(4) mechanical heart valve
(5) cardiopulmonary bypass during surgery
Risk factors for thrombocytopenia identified on multivariate analysis:
(1) presence of nonhead injury (not head injury only - patients with head injury only have less bleeding than if there is non-head injury)
(2) age (about a third of patients < 50 developed thrombocytopenia vs three quarters of those >= 50 years of age)
where:
• Thrombocytopenia was associated with a higher Trauma Score (odds ratio 1.36, which is low). The authors ascribed this to the weighting for the Glasgow Coma Score, which would give a patient with a head injury a lower score. However, since the Trauma Score is intended for triage it may have little relevance for patients in the ICU. I would think the admitting APACHE and daily scores would be more informative.
Additional factors:
(1) Dilutional coagulopathy following transfusion with a large volume of packed RBCs without platelet transfusion. The need for transfusion tended to parallel the seriousness of nonhead injury.
(2) The development of DIC would be associated with thrombocytopenia. Criteria for DIC were given but DIC is not listed in the results of univariate analysis in Table 1 (page 287). The definition of DIC (PT > 12.4 seconds, fibrinogen < 200 mg/dL, fibrin split products > 0.4 µg/mL, and oozing from wounds) was not as stringent as I have seen elsewhere and which would combine both mild, moderate and severe forms.
Drug-induced thrombocytopenia was not an important cause, so that there is not usually a need to discontinue or switch medications. An exception to this might be if the person was receiving a drug that had caused thrombocytopenia in the past.
