To ensure that the relationship between the maximum age of blood and mortality did not differ for specific subgroups, interactions between the age of RBCs and all other covariates were explored.ResultsPatients and participating centersA total of 47 ICUs participated in the study (Australia, n = 36; New Zealand, n = 11). All ICU types were represented: 28 tertiary ICUs, Dasatinib Src inhibitor 10 metropolitan ICUs, four rural ICUs and five private ICUs.In total, 757 patients received one or more units of RBCs. Their demographic and clinical data are shown in Table Table1.1. According to their APACHE III diagnostic classification, 416 (55.0%) were operative patients and 341 (45.0%) were nonoperative patients. The largest diagnostic groups were cardiac surgery patients (194, 25.6%), bacterial pneumonia (36, 4.

8%), septic shock or sepsis (56, 7.3%), gastrointestinal neoplasm (23, 3.0%), nonoperative gastrointestinal bleeding (21, 3.2%), trauma (50, 6.6%), and operative gastrointestinal bleeding (15, 2.0%). The number of transfusions and the age of RBCs are included in Table Table11.Table 1Patient characteristics (n = 757) and transfusion detailsAge of RBCs and hospital mortalityThe mean (median, standard error) pretransfusion hemoglobin level was 7.8 (7.7, 0.03) g/dl. The ages of the oldest RBCs and unadjusted hospital mortalities for the quartiles of the whole study population (n = 757), and hospital mortalities for the quartiles of those included in the multivariate analysis (n = 713) according to maximum RBC age, are shown in Table Table2.2. The hospital mortality in the lowest quartile (Quartile 1) was 25/189 (13.

2%) versus 121/568 (21.3%) in Quartiles 2 to 4, with a significant (P = 0.01) unadjusted absolute risk reduction of 8.1% (95% CI = 2.2 to 14.0%) in hospital mortality.Table 2Unadjusted mortality rates according to quartiles of maximum age of red cellsAdjustment for confounding factorsIn these 713 patients, there was no significant independent association with hospital mortality and the maximum age of RBCs as a continuous variable (univariate OR 1.02, 95% CI = 1.003 to 1.04, P = 0.025; multivariate OR = 1.02, 95% CI = 0.99 to 1.04, P = 0.15), but there was a statistically significant difference in mortality Carfilzomib between quartiles of maximum age of RBCs at both the univariate level (P = 0.01) and the multivariate level (P = 0.03). Day 11 was the 25th percentile of the oldest RBC transfused (not the 25th percentile of all transfused RBCs). When compared with the lowest quartile (Quartile 1), exposure to the combination of three quartiles (Quartiles 2 to 4) of maximum age of RBCs was associated with an increased risk of hospital mortality (adjusted OR = 2.01, 95% CI = 1.07 to 3.77).