Methods:
Transfusion data:Internal diagnostic coding was used to identify the type, date and number of each blood component transfused during hospitalization. By examining individual transfusion records, we determined the number and timing of leukoreduced and non-leukoreduced units of packed red blood cells (PRBCs), fresh frozen plasma (FFP), platelets and cryoprecipitate that were transfused during hospitalization. In the patients who developed TRALI, we traced each individual unit temporally associated (within 6 hours) with TRALI back to one of six blood suppliers and identified donor gender for plasma containing blood components (FFP and platelets) and age of component from collection to transfusion with regard to PRBCs. All units of FFP, platelets,and PRBCs transfused after the development of ALI were excluded from analysis.
Timing of transfusion and onset of ALI: To differentiate TRALI from ALI we timed the onset of ALI with respect to the initiation of transfused blood products. The time of initiation of each transfused blood component is recorded on each individual transfusion record. Timing of ALI onset was determined by three criteria: 1) evolution of chest x-ray reports describing the new development of bilateral infiltrates. Subsequently, the ICU flow sheet was examinedwithin this radiographic interval for 2) a rapid change in FiO2 (>50% increase in supplemental oxygen over 2 hours). The timing of this change in oxygenation was recorded as the onset of ALI. Confirmation by a subsequent arterial blood gas confirming a PaO2/FiO2 ratio <248 was required. To determine the absence of left atrial hypertension we required 3) a subsequent physician progress note documentingthe development of ALI. ALI developing within 6 hours from the initiation of a transfusion was classified as TRALI (consistent with the consensus definition) while all other ALI events temporally unrelated to transfusion were referred to as non transfusion-related ALI.
Definitions: Baseline values were defined as follows: Hematocrit nadir- lowest hematocrit within 72 hours of admission to ICU; Thrombocytopenia: platelets <100,000/µl within 24 hours of presentation to the ICU; Coagulopathy: International Normalized Ratio (INR) > 1.5 within 24 hours of presentation to the ICU; Albumin: earliest available measurement within 48 hours of admission; Alcohol: admission chart record with mention of current alcohol use. The model for end-stage liver disease (MELD) score is a validated, accepted severity of disease scoring system in patients with chronic liver disease. The MELD score was calculated from the earliest available serum creatinine, bilirubin and INR.