Study objectives: To characterize and compare transfusion practices in a broad sample of patients receiving mechanical ventilation (MV) and not receiving MV in the ICU.
Design: Retrospective subgroup analysis from the prospective, multicenter, observational CRIT study.
Setting: Two hundred eighty-four medical, surgical, or medical/surgical ICUs.
Patients: Critically ill adults.
Main results: Of the 4,892 patients enrolled in the CRIT study, 60% were receiving MV on ICU admission or within 48 h after admission for a median of 4 days. Patients receiving MV had higher baseline APACHE (acute physiology and chronic health evaluation) II scores than patients not receiving MV (22.8 ± 7.8 and 14.9 ± 6.4, respectively [mean ± SD]; p < 0.0001). Despite similar baseline hemoglobin levels (11.0 ± 2.3 g/dL and 10.9 ± 2.5 g/dL, p = 0.17), more patients receiving MV underwent transfusions (49% vs 33%, p < 0.0001), and they received significantly more RBCs than patients not receiving MV (p < 0.0001). The principal reason for transfusion in both groups was low hemoglobin level (78.4% and 84.6%, respectively); however, patients receiving MV had higher pretransfusion hemoglobin levels (8.7 ± 1.7 g/dL) than patients not receiving MV (8.2 ± 1.7 g/dL, p < 0.0001). Notably, 40.1% of all transfusions in patients receiving MV were administered after day 3 of the ICU stay, compared to 21.2% in patients not receiving MV (p < 0.0001), and a higher percentage of patients receiving MV remaining in the ICU after day 3 underwent transfusions (33.4% vs 18.3%, p < 0.0001). Mortality was higher (17.2% vs 4.5%, p < 0.0001) and mean hospital (15 days vs 10 days, p < 0.0001) and ICU stays (9 days vs 4 days, p < 0.0001) were longer in the subgroup receiving MV.
Conclusions: Mechanical ventilation appears to be an easily identifiable early marker for allogeneic blood exposure risk in ICU patients. While the longer ICU stays account for much of this risk, patients receiving MV also appear to undergo transfusions at higher hemoglobin thresholds than patients not receiving MV, at least early in the ICU stay. Justification of this relatively liberal transfusion practice in patients receiving MV will require further study.