Red cell requirements for intensive care units adhering to evidence-based transfusion guidelines

Anemia commonly complicates critical illness. Restrictive transfusion triggers are appropriate in this setting, but no large studies have measured red cell (RBC) requirements for intensive care patients when evidence-based transfusion guidelines are followed consistently.

Data were recorded daily for 1023 of 1042 sequential admissions to 10 intensive care units (ICUs) over 100 days. The sample comprised 44 percent of all ICU admissions in Scotland during this period. RBC transfusions and the occurrence of clinically significant hemorrhage were recorded for every ICU day. Transfusion episodes were classified as either associated with or not associated with hemorrhage. Measures of RBC use were derived for the cohort and for Scotland with national audit data.

A total of 39.5 percent (95% confidence interval [CI], 36.5%-42.5%) of admissions received transfusions. Eighteen percent of admissions received at least one transfusion associated with hemorrhage and 26 percent received at least one transfusion not associated with hemorrhage. The median (interquartile range) transfusion trigger in the absence of hemorrhage was 78 (73-78) g/L. The overall mean RBC use was 1.87 (95% CI, 1.79-1.96) units per admission or 0.34 (95% CI, 0.33-0.36) units per ICU-day. Forty-seven percent of RBCs administered were not associated with clinically significant hemorrhage. Mean RBC requirements for intensive care in Scotland were estimated to be 3950 (95% CI, 3780-4140) per million-adult-population per year. This represented 7 to 8 percent of the Scottish blood supply.

Despite evidence-based transfusion practice, 40 percent of ICU patients receive transfusions, which account for 7 to 8 percent of the national blood supply.