Introduction: Longer packed red blood cell (PRBC) storage time has been associated with adverse outcomes in transfused critically ill adults and children. We have shown that PRBCs with longer storage times are immunosuppressive in vitro. We have also shown that reduced innate immune function is associated with adverse outcomes in critically injured children.
Hypothesis: Among critically injured children who have been transfused, longer PRBC storage time will be associated with reduced innate immune function over time as evidenced by a decreased ability to produce TNFα upon ex vivo whole blood stimulation.
Methods: Whole blood was serially sampled from pediatric trauma patients in the PICU upon enrollment and stimulated with LPS (500pg/ml) for 4 hrs at 37C. Supernatants were analyzed for TNFα by chemiluminescence. Transfusion and clinical data were recorded. Data represent median (IQR).
Results: 80 critically injured patients (age: 10 [5-14] yrs; gender: 66% male; PRISM: 2 [0-5]) were prospectively studied. By post-trauma day (PTD) 1, 24 (30%) of these patients (age: 11.7 [4.5-14] yrs; gender: 71% male; PRISM: 4 [2-8]) had been transfused (donor exposures: 2 [1-3]; volume transfused: 13 [10-23] mL/kg; average PRBC storage time: 15 [10-18] days). Patients who were transfused by PTD1 had a higher Injury Severity Score on admission (22 [17-30] vs. 15 [9-24], p=0.0011) and had lower TNFα production capacity on PTD1 (461 [284-911] pg/ml vs 1024 [592-1445], p=0.002) than those who were not. For those transfused by PTD1, longer PRBC storage time (volume-weighted average age of all PRBC transfused per patient) was associated with lower TNFα production capacity at PTD 5-6 (p<0.05) and a trend at PTD 7-8 (p=0.07). In this cohort, PRBC volume (ml/kg) through PTD1 was not associated with TNFα production capacity at any time in the first week after injury (p>0.5).
Conclusions: Our data suggest that longer PRBC storage time, rather than volume transfused, may be associated with reduced innate immune function in transfused critically ill pediatric trauma patients. This finding, if confirmed in larger prospective studies, could lead to changes in blood bank practices targeting normalization of immune function in this population.
(C) 2012 by the Society of Critical Care Medicine and Lippincott Williams & Wilkins