The Effect of Platelet Transfusion on Death in the Intensive Care Unit

Background: Thrombocytopenia is a common complication of critical illness and an independent risk factor for death in the intensive care unit (ICU). Whether platelet transfusions modify the risk of death in critically ill patients is unknown.

Methods: Adult patients admitted to ICU who received one or more platelet transfusion over a 10-year period (2006 - 2015) from 3 academic hospitals in Canada were analyzed from a blood transfusion registry. Oncology patients were excluded. Contemporaneous non-transfused ICU patients were used as controls. Data from the registry were validated by integrity checks with medical records and laboratory information systems. We estimated the effect of platelet transfusion on mortality in ICU adjusted for baseline and time-varying covariates including multi-organ dysfunction score (MODS) and severity of thrombocytopenia using a stratified cox proportional hazards model. Significance was set at p<0.05 for all analyses.

Results: Of 43,234 non-oncology patients admitted to ICU, 5,621 (13.0%) received one or more platelet transfusion. Compared with non-transfused controls, transfused patients had lower platelet counts (median, 82 x10⁹/L vs. 163 x10⁹/L); were more often admitted after surgery (90.7% vs. 46.9%) especially cardiac surgery (86.8% of surgeries vs. 60.6%); and had higher unadjusted mortality (10.7% vs. 6.5%). Using regression analysis adjusted for covariates (nadir platelet count, red blood cell transfusion, need for hemodialysis) and stratified by age, baseline MODS score (available for 66.2% of patients) and need for invasive mechanical ventilation, platelet transfusions were associated with a lower risk of death in ICU [hazard ratio (HR)= 0.66; 95% confidence interval (CI), 0.46 - 0.96; p= 0.028; n= 26,404 with all available data]. A similar effect was observed in the subgroup of cardiac surgery patients (HR= 0.50; 95% CI, 0.26 - 0.98; p=0.044; n= 10,676) but not all surgical patients (HR = 0.73; 95% CI, 0.46 - 1.17; p= 0.188; n= 14,461).

Conclusion:After adjusting for illness severity, thrombocytopenia and other confounders common among critically ill patients, platelet transfusions were associated with improved survival in the population of mostly cardiac surgery patients. This potential protective effect of platelet transfusions requires further evaluation in prospective studies.