Norris, Philip J.

ABSTRACT The concentration of cells is a key component of modern blood tests. Given the biomarker potential of extracellular vesicles (EVs) in blood, we aimed to establish reference ranges for blood cell‐derived EVs using flow cytometry. To address the orders‐of‐magnitude variability in reported EV concentrations between different flow cytometers (FCMs), we first validated a calibration methodology to enable reproducible EV concentration measurements. The methodology was evaluated in an interlaboratory comparison study and shows that calibration reduces the median absolute deviation of EV concentrations measured on 25 different FCMs from 67 % to 25 %–31 %. The calibration methodology was then used to determine reference ranges of erythrocyte‐, leukocyte‐, and platelet‐derived EVs in human blood plasma in a cohort of healthy individuals ( n = 224). This study demonstrates that calibration enables comparable concentration measurements of blood cell‐derived EVs, thereby bringing EVs one step closer to clinical applications.

Background: Transfusion-related acute lung injury (TRALI) and transfusion-associated circulatory overload (TACO) are leading causes of transfusion-related morbidity and mortality. Soluble factors in erythrocyte supernatant may increase risk for these complications. The authors hypothesized that point-of-care allogeneic erythrocyte washing may be an effective intervention to mitigate elevations in soluble factors as well as physiologic responses associated with transfusion-associated respiratory complications in the setting of cardiac surgery. Methods: This is a two-center, nonblinded, randomized clinical trial evaluating point-of-care washed versus standard issue allogeneic erythrocyte transfusions administered during or on the day of cardiac surgery. The primary analysis was performed via modified intention to treat. The primary outcomes assessed were changes in intermediate markers of lung injury as well as cardiopulmonary physiologic responses to erythrocyte transfusion. Secondary outcomes included the duration of intensive care unit and hospital stay, durations of mechanical ventilation and oxygen supplementation, presence of TRALI or TACO, and mortality. Results: Among 154 analyzed patients (81 washed, 73 standard issue), the median age was 66 yr, and 77 (50.0%) were women. The median (interquartile range) number of allogeneic erythrocyte units transfused on the day of surgery was 3.0 (2.0 to 5.0) in the washed erythrocyte group and 3.0 (2.0 to 4.0) in the standard issue group (P = 0.13). No between-group differences were identified in any of the assessed recipient lung injury biomarkers (all P values > adjusted alpha). Durations of intensive care unit stay (median [interquartile range], 3.0 [2.0 to 5.0] vs. 3.0 [2.0 to 4.0] days; P = 0.117) and hospital length of stay (12.0 [9.0 to 17.0] vs. 12.0 [9.0 to 17.0] days; P = 0.801) were similar, as were the number of ventilator-free days at day 28 (27.0 [27.0 to 27.0] vs. 27.0 [26.0 to 27.0]; P = 0.699) and oxygen-free days at day 28 (24.0 [19.0 to 26.0] vs. 24.0 [22.0 to 26.0]; P = 0.400). No significant differences were noted in mortality rate or in incidence rates for TRALI, TACO, and acute kidney injury. Conclusions: Among patients undergoing cardiovascular surgery with high risk of erythrocyte transfusion, point-of-care washing of allogeneic erythrocyte transfusions did not mitigate changes in intermediate markers of lung injury or cardiopulmonary physiologic responses to erythrocyte transfusion and was not associated with improved clinical outcomes.

BACKGROUND: Patients who develop ARDS from medical or traumatic causes typically present after the inciting event has already occurred. Postoperative ARDS is unique in that the inciting insult potentially responsible for ARDS is known ahead of time, which provides an opportunity to study the early pathophysiology of ARDS. The objective of this study was to better understand the early pathophysiology of postoperative ARDS through a temporal analysis of key biomarkers of interest. METHODS: We performed a case-control study of adults undergoing elective thoracic, aortic vascular, or cardiac surgery, which placed them at increased risk of developing postoperative ARDS. Biomarkers were measured at baseline, 2 h, and 6 h after the key intraoperative event believed to be responsible for ARDS. RESULTS: Of the 467 subjects enrolled, 26 developed ARDS and were matched to non-ARDS controls 1:2 based on age, sex, surgical procedure, and surgical lung injury prediction score. Patients with ARDS were more likely to have lower preoperative albumin ( P = .029), longer surgery ( P = .007), larger amounts of intraoperative fluid ( P = .036), and higher intraoperative peak inspiratory pressures ( P = .006). Baseline plasminogen activator inhibitor-1 levels were higher in the ARDS group ( P = .03). Changes in postoperative biomarker levels from baseline were greater in the ARDS group for interleukin-8 (baseline to 6 h, P = .02) and surfactant protein-D (baseline to 2 h, P = .009). CONCLUSIONS: Our study supported the hypothesis that dysregulated coagulation, inflammation, and epithelial injury are pathophysiologic features of early postoperative ARDS. Interleukin-8, plasminogen activator-1, and surfactant protein-D may help predict development of postoperative ARDS.

Background Possible transfusion‐related acute lung injury (p TRALI ) cases by definition have a clear temporal relationship to an alternative recipient risk factor for acute respiratory distress syndrome ( ARDS ). We questioned whether transfusion factors are important for the development of p TRALI . Study Design and Methods In this nested case‐control study, we prospectively identified 145 consecutive patients with p TRALI and randomly selected 163 transfused controls over a 4‐year period at the U niversity of C alifornia at S an F rancisco and the M ayo C linic ( R ochester, M innesota). Results For p TRALI , we found evidence against transfusion being important: receipt of plasma from female donors (odds ratio [ OR ], 0.82; 95% confidence interval [ CI ], 0.29‐2.3; p = 0.70), total number of units transfused ( OR , 0.99; 95% CI , 0.89‐1.10; p = 0.86), and number of red blood cell and whole blood units transfused ( OR , 0.78; 95% CI , 0.59‐1.03; p = 0.079). In contrast, we found that risk for p TRALI was associated with additional recipient factors: chronic alcohol abuse ( OR , 12.5; 95% CI , 2.8‐55; p < 0.001), current smoker ( OR , 4.2; 95% CI , 1.67‐10.8; p = 0.0024), shock before transfusion ( OR , 4.6; 95% CI , 2.0‐10.7; p < 0.001), and positive fluid balance before transfusion ( OR , 1.32/ L ; 95% CI , 1.20‐1.44; p < 0.001). Conclusion Recipient risk factors for ARDS rather than transfusion risk factors predominate in p TRALI .

BackgroundIdentifying antibodies to HLA (anti‐HLA) by solid‐phase assays is used to screen blood donors to mitigate transfusion‐related acute lung injury risk. Various cutoffs for detection assays have been proposed in the literature; however, these do not take into consideration lot‐to‐lot variability of commercially available assays.Study Design and MethodsSamples from 93 nontransfused males were tested using five different lots of a multiplex bead‐based anti‐HLA detection kit. A subset of 17 samples was tested on 5 days using a single lot. An additional 96 samples from donations with varied anti‐HLA levels were tested using kits from two different lots. Results were reported as a normalized background (NBG) ratio.ResultsFor the 93 nontransfused donors, NBG values generated using the reference lot were significantly higher than those obtained with three of the four comparator lots. However, for the 96 samples with low‐, moderate‐, and higher‐level anti‐HLA, Class I (CL‐I) values were 1.4 times lower and Class II (CL‐II) values were 1.2 times lower using the reference versus comparator lot. For CL‐I antibodies the between‐lot standard deviation (SD) was 1.36 (95% confidence interval [CI], 1.19‐1.60), while the between‐day SD was 1.27 (95% CI, 1.08‐1.52). Similarly, for CL‐II antibodies the between‐lot SD was 0.81 (95% CI, 0.70‐0.95), while the between‐day SD was 0.50 (95% CI, 0.43‐0.60).ConclusionsThere is interlot variability in the tested HLA detection assay as well as significant bias between lots. It may be reasonable to develop a new cutoff when a new lot is obtained.

AbstractTransfusion-related acute lung injury (TRALI) is the leading cause of transfusion-related mortality. To determine TRALI incidence by prospective, active surveillance and to identify risk factors by a case-control study, 2 academic medical centers enrolled 89 cases and 164 transfused controls. Recipient risk factors identified by multivariate analysis were higher IL-8 levels, liver surgery, chronic alcohol abuse, shock, higher peak airway pressure while being mechanically ventilated, current smoking, and positive fluid balance. Transfusion risk factors were receipt of plasma or whole blood from female donors (odds ratio = 4.5, 95% confidence interval [CI], 1.85-11.2, P = .001), volume of HLA class II antibody with normalized background ratio more than 27.5 (OR = 1.92/100 mL, 95% CI, 1.08-3.4, P = .03), and volume of anti–human neutrophil antigen positive by granulocyte immunofluoresence test (OR = 1.71/100 mL, 95% CI, 1.18-2.5, P = .004). Little or no risk was associated with older red blood cell units, noncognate or weak cognate class II antibody, or class I antibody. Reduced transfusion of plasma from female donors was concurrent with reduced TRALI incidence: 2.57 (95% CI, 1.72-3.86) in 2006 versus 0.81 (95% CI, 0.44-1.49) in 2009 per 10 000 transfused units (P = .002). The identified risk factors provide potential targets for reducing residual TRALI.