Platelet Transfusions in a Medical- Surgical Intensive Care Unit.

Background: The benefits and harms of platelet transfusions in critically ill patients are unclear.

Objectives: To describe the frequency of, indications for, and effects of platelet transfusions in patients admitted to a medical- surgical intensive care unit (ICU).

Design: Single center cohort study (January 2001 to January 2002).

Methods: We identified all patients who developed thrombocytopenia (platelet count <150 x 10⁹/l) during their ICU admission from a prospective study which enrolled consecutive adults admitted to ICU with an expected length of stay ≥72 hours, and which excluded patients with trauma, orthopedic surgery, cardiac surgery, pregnancy, or receiving palliative care. Retrospectively, using a priori criteria, bleeding severity and the indications for platelet transfusions were assessed; 23.7% of bleeding events and 89.5% of transfusion indications were reviewed in duplicate independently. Initial agreement was calculated using Cohen’s unweighted kappa and all assessments of bleeding severity and transfusion indications were adjudicated by third person.

Results: Of 261 ICU patients, 118 (45.2%) had thrombocytopenia. Initial agreement between primary reviewers for assessments of bleeding severity was good (k= 0.69), and for indications for platelet transfusions was poor (k=0.35); consensus was achieved in all cases. One third of thrombocytopenic patients had major bleeding (37/118, 31.4%), and one fifth had minor bleeding (24/118, 20.3%). Among thrombocytopenic patients, 27/118 (22.9%) received a total of 76 platelet transfusions, 24 (31.6%) of which were administered to treat bleeding, and 52 (68.4%) of which were to prevent bleeding. Of the prophylactic platelet transfusions, 18/52 (34.6%) preceded invasive procedures. The mean ± SD platelet count prior to therapeutic platelet transfusions was 54 ± 40 x10⁹/l; for peri-procedural transfusions, 55 ± 38 x10⁹/l; and for other prophylactic platelet transfusions, 37 ± 21 x10⁹/l. Most transfusions (69/76, 91%) were administered as pools of 5.2 ± 1.2 random donor platelets, and few (7/76, 9.2%) were apheresis platelets. A single platelet transfusion (pool of 5 random donor units or 1 apheresis unit) resulted in a platelet increment of 14 ± 29 x10⁹/l at 6.6 ± 5.9 hours following transfusion. No rise in platelet count was observed following 17 transfusions given to 13 patients.

Conclusions: Platelet transfusions are frequently administered to thrombocytopenic critically ill patients, and, although the indication is not always clear, the most common reason is to prevent bleeding. Nearly half of transfused ICU patients were refractory to one or more platelet transfusion. Further prospective studies are needed on the indications for, and effects of, platelet transfusions in the ICU setting.