Mechanical ventilation aggravates transfusion-related acute lung injury induced by MHC-I class antibodies

Transfusion increased skin blood flow when initially low in volume-resuscitated patients without acute bleeding

Background

Alterations in skin blood flow is a marker of inadequate tissue perfusion in critically ill patients after initial resuscitation. The effects of red blood cell transfusions (RBCT) on skin perfusion are not described in this setting. We evaluated the effects of red blood cell transfusions on skin tissue perfusion in critically ill patients without acute bleeding after initial resuscitation.

Methods

A prospective observational study included 175 non-bleeding adult patients after fluid resuscitation requiring red blood cell transfusions. Using laser Doppler, we measured finger skin blood flow (SBF) at skin basal temperature (SBFBT), together with mean arterial pressure (MAP), heart rate (HR), hemoglobin (Hb), central venous pressure (CVP), lactate, and central or mixed venous oxygen saturation before and 1 h after RBCT. SBF responders were those with a 20% increase in SBFBT after RBCT.

Results

Overall, SBFBT did not significantly change after RBCT [from 79.8 (4.3-479.4) to 83.4 (4.9-561.6); p = 0.67]. A relative increase equal to or more than 20% in SBFBT after RBCT (SBF responders) was observed in 77/175 of RBCT (44%). SBF responders had significantly lower SBFBT [41.3 (4.3-279.3) vs. 136.3 (6.5-479.4) perfusion units; p < 0.01], mixed or central venous oxygen saturation (62.5 ± 9.2 vs. 67.3% ± 12.0%; p < 0.01) and CVP (8.3 ± 5.1 vs. 10.3 ± 5.6 mmHg; p = 0.03) at baseline than non-responders. SBFBT increased in responders [from 41.3 (4.3-279.3) to 93.1 (9.8-561.6) perfusion units; p < 0.01], and decreased in the non-responders [from 136.3 (6.5-479.4) to 80.0 (4.9-540.8) perfusion units; p < 0.01] after RBCT. Pre-transfusion SBFBT was independently associated with a 20% increase in SBFBT after RBCT. Baseline SBFBT had an area under receiver operator characteristic of 0.73 (95% CI, 0.68-0.83) to predict SBFBT increase; A SBFBT of 73.0 perfusion units (PU) had a sensitivity of 71.4% and a specificity of 70.4% to predict SBFBT increase after RBCT. No significant differences in SBFBT were observed after RBCT in different subgroup analyses.

Conclusion

The skin blood flow is globally unaltered by red blood cell transfusions in non-bleeding critically ill patients after initial resuscitation. However, a lower SBFBT at baseline was associated with a relative increase in skin tissue perfusion after RBCT.

Does donor sex influence the potential for transfusion with washed packed red blood cells to limit transfusion-related immune responses in preterm newborns?

OBJECTIVE

To evaluate the association of donor sex with transfusion-associated recipient immune responses in preterm newborns receiving unwashed and washed blood.

DESIGN

A cohort study using data collected during the Effect of Washed versus Unwashed Packed Red Blood Cell Transfusion on Immune Responses in the Extremely Preterm Newborn randomised trial.

SETTING

Participants were recruited from two South Australian hospitals between September 2015 and December 2020.

PATIENTS

Preterm newborns (<29 weeks).

INTERVENTIONS

Transfusion with unwashed and washed packed red blood cells (PRBCs) from either exclusively male or any female donor for the first three transfusions.

MAIN OUTCOMES MEASURES

The primary outcome was the change from baseline in post-transfusion plasma cytokine concentrations, specifically interferon gamma, interleukin (IL)-1β, IL-6, IL-8, IL-10, IL-12, IL-17A and tumour necrosis factor (TNF).

RESULTS

In total, 153 newborns were evaluated. By the third transfusion, the magnitude of pretransfusion to post-transfusion change in cytokines between the groups differed for IL-6 (p=0.003), IL-12 (p=0.008), IL-17A (p=0.003) and TNF (p=0.007). On post hoc comparison, compared with the unwashed-any female donor group, IL-6 (p<0.05), IL-12 (p<0.05) and IL-17A (p<0.01) were lower in the washed-exclusively male donor group, and IL-6 (p<0.01), IL-12 (p<0.05) and TNF (p<0.01) were lower in the washed-any female donor group.

CONCLUSION

These findings suggest that transfusion with unwashed PRBCs from female donors is associated with an increased recipient immune response, an effect that can be ameliorated with pretransfusion washing. Larger randomised controlled studies confirming this mechanistic link between donor sex and transfusion-associated morbidity are warranted.

TRIAL REGISTRATION NUMBER

ACTRN12613000237785.

Red Blood Cell Donor Sex Associated Effects on Morbidity and Mortality in the Extremely Preterm Newborn

Transfusion exposure increases the risk of death in critically ill patients of all ages. This was thought to relate to co-morbidities in the transfusion recipient. However, donor characteristics are increasingly recognised as critical to transfusion recipient outcome with systematic reviews suggesting blood donor sex influences transfusion recipient health. Originally focusing on plasma and platelet transfusions, retrospective studies report greater risks of adverse outcomes such as transfusion related acute lung injury in those receiving products from female donors. There is increasing awareness that exposure to red blood cells (RBCs) poses a similar risk. Recent studies focusing on transfusion related outcomes in extremely preterm newborns report conflicting data on the association between blood donor sex and outcomes. Despite a renewed focus on lower versus higher transfusion thresholds in neonatal clinical practice, this group remain a heavily transfused population, receiving on average 3-5 RBC transfusions during their primary hospital admission. Therefore, evidence supporting a role for better donor selection could have a significant impact on clinical outcomes in this high-risk population. Here, we review the emerging evidence for an association between blood donor sex and clinical outcomes in extremely preterm newborns receiving one or more transfusions.

Association of Veterinary Hematology and Transfusion Medicine (AVHTM) transfusion reaction small animal consensus statement (TRACS). Part 3: Diagnosis and treatment

OBJECTIVE

To systematically review available evidence to develop guidelines for diagnosis and treatment of transfusion-associated reactions in dogs and cats.

DESIGN

Standardized and systemic evaluation of the literature (identified through Medline via PubMed and Google Scholar searches) was carried out for identified transfusion reaction types in dogs and cats. The available evidence was evaluated using PICO (Population, Intervention, Comparison, Outcome) questions generated for each reaction type. The evidence was categorized by level of evidence (LOE) and quality (Good, Fair, or Poor). Guidelines, diagnostic, and treatment algorithms were generated based on the evaluation of the evidence. Consensus on the final guidelines was achieved through Delphi-style surveys. Draft recommendations were disseminated through veterinary specialty listservs for review and comments, which were evaluated and integrated prior to final publication.

RESULTS

Medline via PubMed and Google Scholar databases were searched. There were 14 Population Intervention Comparison Outcome questions identified and corresponding worksheets were developed focusing on the diagnosis and treatment of transfusion-associated reactions in dogs and cats. Fourteen guidelines and four algorithms were developed with a high degree of consensus.

CONCLUSIONS

This systematic evidence evaluation process yielded recommended diagnostic and treatment algorithms for use in practice. However, significant knowledge gaps were identified, demonstrating the need for additional research in veterinary transfusion medicine.

Transfusion in the mechanically ventilated patient

Red blood cell transfusions are a frequent intervention in critically ill patients, including in those who are receiving mechanical ventilation. Both these interventions can impact negatively on lung function with risks of transfusion-related acute lung injury (TRALI) and other forms of acute respiratory distress syndrome (ARDS). The interactions between transfusion, mechanical ventilation, TRALI and ARDS are complex and other patient-related (e.g., presence of sepsis or shock, disease severity, and hypervolemia) or blood product-related (e.g., presence of antibodies or biologically active mediators) factors also play a role. We propose several strategies targeted at these factors that may help limit the risks of associated lung injury in critically ill patients being considered for transfusion.

rIL-35 prevents murine transfusion-related acute lung injury by inhibiting the activation of endothelial cells

BACKGROUND

Transfusion-related acute lung injury (TRALI) is an important cause of death associated with transfusion, and no specific clinical treatments are available. Endothelial cells are believed to play an important role in the development of TRALI. This study investigated whether IL-35, an endothelial stabilizing cytokine could regulate the severity of antibody-mediated TRALI in vivo.

STUDY DESIGN AND METHODS

Human microvascular endothelial cells (HMVECs) were cultured in vitro, rIL-35(2 μg/mL) was added before HMVECs activation, and HMVECs were fully activated by LPS (0.5 μg/mL). Then cells were collected for flow cytometry analysis. We used a previously established "two-event" mouse model of TRALI with naive and lipopolysaccharide (LPS)-injected mice as controls. rIL-35(100 μg/kg) was injected into the tail vein for 3 consecutive days before the induction of the TRALI model. Samples were collected 2 hours after TRALI induction and tested for lung tissue myeloperoxidase activity, total protein levels, lung tissue histology, endothelial cell activation assay, and cytokine assay.

RESULTS

In vitro culture of HMVECs with rIL-35 verified that rIL-35 inhibited endothelial cells. In a mouse model, prophylactic administration of rIL-35 prevented pulmonary edema, increased lung protein levels, and reduced polymorphonuclear neutrophil accumulation in the lung.

CONCLUSIONS

This work suggests that antibody-mediated murine TRALI can be prevented by rIL-35, and that rIL-35 appears to work by inhibiting the activation of lung endothelial cells.

Using arterial-venous oxygen difference to guide red blood cell transfusion strategy

Background

Guidelines recommend a restrictive red blood cell transfusion strategy based on hemoglobin (Hb) concentrations in critically ill patients. We hypothesized that the arterial-venous oxygen difference (A-V O_2diff), a surrogate for the oxygen delivery to consumption ratio, could provide a more personalized approach to identify patients who may benefit from transfusion.

Methods

A prospective observational study including 177 non-bleeding adult patients with a Hb concentration of 7.0–10.0 g/dL within 72 h after ICU admission. The A-V O_2diff, central venous oxygen saturation (ScvO₂), and oxygen extraction ratio (O₂ER) were noted when a patient’s Hb was first within this range. Transfusion decisions were made by the treating physician according to institutional policy. We used the median A-V O_2diff value in the study cohort (3.7 mL) to classify the transfusion strategy in each patient as “appropriate” (patient transfused when the A-V O_2diff > 3.7 mL or not transfused when the A-V O_2diff ≤ 3.7 mL) or “inappropriate” (patient transfused when the A-V O_2diff ≤ 3.7 mL or not transfused when the A-V O_2diff > 3.7 mL). The primary outcome was 90-day mortality.

Results

Patients managed with an “appropriate” strategy had lower mortality rates (23/96 [24%] vs. 36/81 [44%]; p = 0.004), and an “appropriate” strategy was independently associated with reduced mortality (hazard ratio [HR] 0.51 [95% CI 0.30–0.89], p = 0.01). There was a trend to less acute kidney injury with the “appropriate” than with the “inappropriate” strategy (13% vs. 26%, p = 0.06), and the Sequential Organ Failure Assessment (SOFA) score decreased more rapidly (p = 0.01). The A-V O_2diff, but not the ScvO₂, predicted 90-day mortality in transfused (AUROC = 0.656) and non-transfused (AUROC = 0.630) patients with moderate accuracy. Using the ROC curve analysis, the best A-V O_2diff cutoffs for predicting mortality were 3.6 mL in transfused and 3.5 mL in non-transfused patients.

Conclusions

In anemic, non-bleeding critically ill patients, transfusion may be associated with lower 90-day mortality and morbidity in patients with higher A-V O_2diff.

Trial registration

ClinicalTrials.gov, NCT03767127. Retrospectively registered on 6 December 2018.

Risk factors, management and prevention of transfusion-related acute lung injury: a comprehensive update

Introduction: Despite mitigation strategies that include the exclusion of females from plasma donation or the exclusion of females with a history of pregnancy or known anti-leukocyte antibody, transfusion-related acute lung injury (TRALI) remains a leading cause of transfusion-related morbidity and mortality. Areas covered: The definition of TRALI is discussed and re-aligned with the new Berlin Diagnostic Criteria for the acute respiratory distress syndrome (ARDS). The risk factors associated with TRALI are summarized as are the mitigation strategies to further reduce TRALI. The emerging basic research studies that may translate to clinical therapeutics for the prevention or treatment of TRALI are discussed. Expert opinion: At risk patients, including the genetic factors that may predispose patients to TRALI are summarized and discussed. The re-definition of TRALI employing the Berlin Criteria for ARDS will allow for increased recognition and improved research into pathophysiology and mitigation to reduce this fatal complication of hemotherapy.

A consensus redefinition of transfusion-related acute lung injury

BACKGROUND

Transfusion-related acute lung injury (TRALI) is a serious complication of blood transfusion and is among the leading causes of transfusion-related morbidity and mortality in most developed countries. In the past decade, the pathophysiology of this potentially life-threatening syndrome has been increasingly elucidated, large cohort studies have identified associated patient conditions and transfusion risk factors, and preventive strategies have been successfully implemented. These new insights provide a rationale for updating the 2004 consensus definition of TRALI.

STUDY DESIGN AND METHODS

An international expert panel used the Delphi methodology to develop a redefinition of TRALI by modifying and updating the 2004 definition. Additionally, the panel reviewed issues related to TRALI nomenclature, patient conditions associated with acute respiratory distress syndrome (ARDS) and TRALI, TRALI pathophysiology, and standardization of reporting of TRALI cases.

RESULTS

In the redefinition, the term "possible TRALI" has been dropped. The terminology of TRALI Type I (without an ARDS risk factor) and TRALI Type II (with an ARDS risk factor or with mild existing ARDS) is proposed. Cases with an ARDS risk factor that meet ARDS diagnostic criteria and where respiratory deterioration over the 12 hours before transfusion implicates the risk factor as causative should be classified as ARDS. TRALI remains a clinical diagnosis and does not require detection of cognate white blood cell antibodies.

CONCLUSIONS

Clinicians should report all cases of posttransfusion pulmonary edema to the transfusion service so that further investigation can allow for classification of such cases as TRALI (Type I or Type II), ARDS, transfusion-associated circulatory overload (TACO), or TRALI or TACO cannot distinguish or an alternate diagnosis.

Role of the Purinergic Receptor P2XR4 After Blunt Chest Trauma in Cigarette Smoke-Exposed Mice

Both acute and chronic lung injury are associated with up-regulation of the pulmonary expression of the purinergic receptors P2XR4 and P2XR7. Genetic deletion or blockade of P2XR7 attenuated pulmonary hyperinflammation, but simultaneous P2XR4 up-regulation compensated for P2XR7 deletion. Therefore, we tested the hypothesis whether genetic P2XR4 deletion would attenuate the pulmonary inflammatory response and thereby improve organ function after blunt chest trauma in mice with and without pretraumatic cigarette smoke (CS) exposure.After 3 weeks to 4 weeks of exposure to CS, anesthetized wildtype or P2XR4 mice (n = 32) underwent a blast wave-induced blunt chest trauma followed by 4 h of lung-protective mechanical ventilation, fluid resuscitation, and noradrenaline support to maintain mean arterial pressure >55 mm Hg. Hemodynamics, lung mechanics, gas exchange, and acid-base status were measured together with blood and tissue cytokine and chemokine concentrations, heme oxygenase-1, B-cell lymphoma-extra large (Bcl-xL), endogenous nuclear factor-κB inhibitor (IκBα) expression, nitrotyrosine formation, purinergic receptor expression, and histological scoring.Despite a significant increase in the histopathology score in both CS-exposed groups, neither CS exposure nor P2XR4 deletion had any significant effect on post-traumatic pulmonary function and inflammatory response. However, P2XR4 deletion was associated with attenuated impairment of glucose homeostasis and acid-base-status after CS exposure and chest trauma.In conclusion, genetic P2XR4 deletion failed to attenuate the acute post-traumatic pulmonary inflammatory response. The improved glucose homeostasis and acid-base-status after CS exposure in the P2XR4 group was possibly due to less alveolar hypoxia-induced right ventricular remodeling resulting in preserved liver metabolic capacity.

Interaction between peri-operative blood transfusion, tidal volume, airway pressure and postoperative ARDS: an individual patient data meta-analysis

Background

Transfusion of blood products and mechanical ventilation with injurious settings are considered risk factors for postoperative lung injury in surgical Patients.

Methods

A systematic review and individual patient data meta-analysis was done to determine the independent effects of peri-operative transfusion of blood products, intra-operative tidal volume and airway pressure in adult patients undergoing mechanical ventilation for general surgery, as well as their interactions on the occurrence of postoperative acute respiratory distress syndrome (ARDS). Observational studies and randomized trials were identified by a systematic search of MEDLINE, CINAHL, Web of Science, and CENTRAL and screened for inclusion into a meta-analysis. Individual patient data were obtained from the corresponding authors. Patients were stratified according to whether they received transfusion in the peri-operative period [red blood cell concentrates (RBC) and/or fresh frozen plasma (FFP)], tidal volume size [≤7 mL/kg predicted body weight (PBW), 7-10 and >10 mL/kg PBW] and airway pressure level used during surgery (≤15, 15-20 and >20 cmH₂O). The primary outcome was development of postoperative ARDS.

Results

Seventeen investigations were included (3,659 patients). Postoperative ARDS occurred in 40 (7.2%) patients who received at least one blood product compared to 40 patients (2.5%) who did not [adjusted hazard ratio (HR), 2.32; 95% confidence interval (CI), 1.25-4.33; P=0.008]. Incidence of postoperative ARDS was highest in patients ventilated with tidal volumes of >10 mL/kg PBW and having airway pressures of >20 cmH₂O receiving both RBC and FFP, and lowest in patients ventilated with tidal volume of ≤7 mL/kg PBW and having airway pressures of ≤15 cmH₂O with no transfusion. There was a significant interaction between transfusion and airway pressure level (P=0.002) on the risk of postoperative ARDS.

Conclusions

Peri-operative transfusion of blood products is associated with an increased risk of postoperative ARDS, which seems more dependent on airway pressure than tidal volume size.

Reporting transfusion-related acute lung injury by clinical and preclinical disciplines

BACKGROUND

Disciplines involved in diagnosing transfusion-related acute lung injury (TRALI) report according to a "one-hit" theory. However, studies showed that patients with an underlying condition are at increased risk of the development of TRALI. We investigated whether accumulating evidence on the "two-hit" theory has changed the practice of reporting TRALI.

MATERIALS AND METHODS

Departments of haematology, haemovigilance, transfusion medicine, intensive care and anaesthesiology from all Dutch hospitals with at least five beds equipped for mechanical ventilation were invited to participate in an online survey. Using clinical vignettes with conjoint analysis we investigated the effect of patients' age, admission diagnosis, type and number of transfusions and presence of risk factors for acute lung injury on TRALI reporting. A positive β-coefficient indicated a higher likelihood of reporting TRALI.

RESULTS

We received 129 questionnaires (response rate 74%). Respondents were more likely to report TRALI in younger patients, if symptoms developed within 2 hours of transfusion and if patients had received multiple transfusions. Sepsis and the presence of a risk factor for acute lung injury reduced the inclination to report. Transfusion medicine physicians and haemovigilance staff no longer took the age of transfusion products into account in their diagnostic considerations on TRALI.

DISCUSSION

We conclude that the multidisciplinary team involved in TRALI reporting, still considers TRALI a "one-hit" event, despite accumulating evidence that supports the "two-hit" theory. These results suggest that the patients most at risk of developing TRALI are not reported to the blood bank.

Is platelet transfusion associated with hospital-acquired infections in critically ill patients?

BACKGROUND

Platelets are commonly transfused to critically ill patients. Reports suggest an association between platelet transfusion and infection. However, there is no large study to have determined whether platelet transfusion in critically ill patients is associated with hospital-acquired infection.

METHODS

We conducted a multi-centre study using prospectively maintained databases of two large academic intensive care units (ICUs) in Australia. Characteristics of patients who received platelets in ICUs between 2008 and 2014 were compared to those of patients who did not receive platelets. Association between platelet administration and infection (bacteraemia and/or bacteriuria) was modelled using multiple logistic regression and Cox regression, with blood components as time-varying covariates. A propensity covariate adjustment was also performed to verify results.

RESULTS

Of the 18,965 patients included, 2250 (11.9%) received platelets in ICU with a median number of 1 platelet unit (IQR 1-3) administered. Patients who received platelets were more severely ill at ICU admission (mean Acute Physiology and Chronic Health Evaluation III score 65 (SD 29) vs 52 (SD 25), p < 0.01) and had more comorbidities (31% vs 19%, p < 0.01) than patients without platelet transfusion. Invasive mechanical ventilation (87% vs 57%, p < 0.01) and renal replacement therapy (20% vs 4%, p < 0.01) were more frequently administered in patients receiving platelets than in patients without platelets. On univariate analysis, platelet transfusion was associated with hospital-acquired infection in the ICU (7.7% vs 1.4%, p < 0.01). After adjusting for confounders, including other blood components administered, patient severity, centre, year, and diagnosis category, platelet transfusions were independently associated with infection (adjusted OR 2.56 95% CI 1.98-3.31, p < 0.001). This association was also found in survival analysis with blood components as time-varying covariates (adjusted HR 1.85, 95% CI 1.41-2.41, p < 0.001) and when only bacteraemia was considered (adjusted OR 3.30, 95% CI 2.30-4.74, p <0.001). Platelet transfusions remained associated with infection after propensity covariate adjustment.

CONCLUSIONS

After adjustment for confounders, including patient severity and other blood components, platelet transfusion was independently associated with ICU-acquired infection. Further research aiming to better understand this association and to prevent this complication is warranted.

The Epidemiology of Transfusion-related Acute Lung Injury Varies According to the Applied Definition of Lung Injury Onset Time

RATIONALE

Research that applies an unreliable definition for transfusion-related acute lung injury (TRALI) may draw false conclusions about its risk factors and biology. The effectiveness of preventive strategies may decrease as a consequence. However, the reliability of the consensus TRALI definition is unknown.

OBJECTIVES

To prospectively study the effect of applying two plausible definitions of acute respiratory distress syndrome onset time on TRALI epidemiology.

METHODS

We studied 316 adults admitted to the intensive care unit and transfused red blood cells within 24 hours of blunt trauma. We identified patients with acute respiratory distress syndrome, and defined acute respiratory distress syndrome onset time two ways: (1) the time at which the first radiographic or oxygenation criterion was met, and (2) the time both criteria were met. We categorized two corresponding groups of TRALI cases transfused in the 6 hours before acute respiratory distress syndrome onset. We used Cohen's kappa to measure agreement between the TRALI cases and implicated blood components identified by the two acute respiratory distress syndrome onset time definitions. In a nested case-control study, we examined potential risk factors for each group of TRALI cases, including demographics, injury severity, and characteristics of blood components transfused in the 6 hours before acute respiratory distress syndrome onset.

MEASUREMENTS AND MAIN RESULTS

Forty-two of 113 patients with acute respiratory distress syndrome were TRALI cases per the first acute respiratory distress syndrome onset time definition and 63 per the second definition. There was slight agreement between the two groups of TRALI cases (κ = 0.16; 95% confidence interval, -0.01 to 0.33) and between the implicated blood components (κ = 0.15, 95% confidence interval, 0.11-0.20). Age, Injury Severity Score, high plasma-volume components, and transfused plasma volume were risk factors for TRALI when applying the second acute respiratory distress syndrome onset time definition but not when applying the first definition.

CONCLUSIONS

The epidemiology of TRALI varies when applying two plausible definitions of acute respiratory distress syndrome onset time to severely injured trauma patients. A TRALI definition that standardizes acute respiratory distress syndrome onset time might improve reliability and align efforts to understand epidemiology, biology, and prevention.

Blunt Chest Trauma in Mice after Cigarette Smoke-Exposure: Effects of Mechanical Ventilation with 100% O2

Cigarette smoking (CS) aggravates post-traumatic acute lung injury and increases ventilator-induced lung injury due to more severe tissue inflammation and apoptosis. Hyper-inflammation after chest trauma is due to the physical damage, the drop in alveolar PO₂, and the consecutive hypoxemia and tissue hypoxia. Therefore, we tested the hypotheses that 1) CS exposure prior to blunt chest trauma causes more severe post-traumatic inflammation and thereby aggravates lung injury, and that 2) hyperoxia may attenuate this effect. Immediately after blast wave-induced blunt chest trauma, mice (n=32) with or without 3-4 weeks of CS exposure underwent 4 hours of pressure-controlled, thoraco-pulmonary compliance-titrated, lung-protective mechanical ventilation with air or 100 % O₂. Hemodynamics, lung mechanics, gas exchange, and acid-base status were measured together with blood and tissue cytokine and chemokine concentrations, heme oxygenase-1 (HO-1), activated caspase-3, and hypoxia-inducible factor 1-α (HIF-1α) expression, nuclear factor-κB (NF-κB) activation, nitrotyrosine formation, purinergic receptor 2X₄ (P2XR₄) and 2X₇ (P2XR₇) expression, and histological scoring. CS exposure prior to chest trauma lead to higher pulmonary compliance and lower PaO₂ and Horovitz-index, associated with increased tissue IL-18 and blood MCP-1 concentrations, a 2-4-fold higher inflammatory cell infiltration, and more pronounced alveolar membrane thickening. This effect coincided with increased activated caspase-3, nitrotyrosine, P2XR₄, and P2XR₇ expression, NF-κB activation, and reduced HIF-1α expression. Hyperoxia did not further affect lung mechanics, gas exchange, pulmonary and systemic cytokine and chemokine concentrations, or histological scoring, except for some patchy alveolar edema in CS exposed mice. However, hyperoxia attenuated tissue HIF-1α, nitrotyrosine, P2XR₇, and P2XR₄ expression, while it increased HO-1 formation in CS exposed mice. Overall, CS exposure aggravated post-traumatic inflammation, nitrosative stress and thereby organ dysfunction and injury; short-term, lung-protective, hyperoxic mechanical ventilation have no major beneficial effect despite attenuation of nitrosative stress, possibly due to compensation of by regional alveolar hypoxia and/or consecutive hypoxemia, resulting in down-regulation of HIF-1α expression.

Antibody-mediated transfusion-related acute lung injury; from discovery to prevention

Transfusion-related acute lung injury (TRALI), a syndrome of respiratory distress caused by blood transfusion, is the leading cause of transfusion-related mortality. The majority of TRALI cases have been related to passive infusion of human leucocyte antigen (HLA) and human neutrophil antigen (HNA) antibodies in donor blood. In vitro, ex vivo and in vivo animal models have provided insight in TRALI pathogenesis. The various classes of antibodies implicated in TRALI appear to have different pathophysiological mechanisms for the induction of TRALI involving endothelial cells, neutrophils, monocytes and, as very recently has been discovered, lymphocytes. The HLA and HNA-antibodies are found mainly in blood from multiparous women as they have become sensitized during pregnancy. The incidence of TRALI has decreased rapidly following the introduction of a male-only strategy for plasma donation. This review focuses on pre-clinical and clinical studies investigating the pathophysiology of antibody-mediated TRALI.

Advances in ventilator-associated lung injury: prevention is the target

Mechanical ventilation (MV) is the main supportive treatment in respiratory failure due to different etiologies. However, MV might aggravate ventilator-associated lung injury (VALI). Four main mechanisms leading to VALI are: 1) increased stress and strain, induced by high tidal volume (VT); 2) increased shear stress, i.e. opening and closing, of previously atelectatic alveolar units; 3) distribution of perfusion and 4) biotrauma. In severe acute respiratory distress syndrome patients, low VT, higher levels of positive end expiratory pressure, long duration prone position and neuromuscular blockade within the first 48 hours are associated to a better outcome. VALI can also occur by using high VT in previously non injured lungs. We believe that prevention is the target to minimize injurious effects of MV. This review aims to describe pathophysiology of VALI, the possible prevention and treatment as well as monitoring MV to minimize VALI.

Novel swine model of transfusion-related acute lung injury

BACKGROUND

Transfusion-related acute lung injury (TRALI) is a life-threatening complication of blood transfusion. Antibodies against human leukocyte antigens in donors' plasma are the major causes of TRALI. Several animal models of TRALI have been developed, and the mechanism underlying TRALI development has been extensively investigated using rodent models. Although sheep models of nonimmune TRALI have been developed, large-animal models of antibody-mediated TRALI are not yet available.

STUDY DESIGN AND METHODS

To develop a swine model of TRALI, male Clawn strain miniature pigs were used. A monoclonal antibody (MoAb) against swine leukocyte antigens (SLAs) Class I (4G8, 0.3 or 1.0 mg/kg body weight [BW]) and a control antibody (1.0 mg/kg BW) were injected into the peripheral vein after priming with or without 1 μg/kg BW lipopolysaccharide (LPS; n = 3 each). Lung injury was assessed using PaO2 /FiO2 (P/F) ratio and by chest X-ray imaging. Histopathologic analysis was also conducted.

RESULTS

Lung injury could be induced by injecting 4G8 at an amount of 1.0 mg/kg BW, after LPS. The P/F ratio 90 minutes after the administration of 4G8 significantly decreased (p < 0.05). Bilateral infiltration was shown in chest X-ray imaging. Lung injury was confirmed by histopathologic analysis.

CONCLUSION

Lung injury in pigs was successfully induced by anti-SLA MoAb. Priming with LPS is a prerequisite for inducing lung injury and the amount of the antibody is a critical condition.

The effect of C1-inhibitor in a murine model of transfusion-related acute lung injury

BACKGROUND AND OBJECTIVE

Transfusion-related acute lung injury (TRALI) is the leading cause of transfusion-related morbidity and mortality. Specific therapy is lacking. We assessed whether C1-inhibitor attenuates lung injury in a 'two-hit' TRALI model.

METHODS

Mice were primed with lipopolysaccharide, subsequently TRALI was induced by MHC-I antibodies. In the intervention group, C1-inhibitor was infused concomitantly. Mice were supported with mechanical ventilation. After 2 h, mice were killed, lungs were removed and bronchoalveolar lavage fluid (BALF) was obtained.

RESULTS

Injection of MHC-I antibodies induced TRALI, illustrated by an increase in wet-to-dry ratio of the lungs, in BALF protein levels and in lung injury scores. TRALI was further characterized by complement activation, demonstrated by increased BALF levels of C3a and C5a. Administration of C1-inhibitor resulted in increased pulmonary C1-inhibitor levels with high activity. C1-inhibitor reduced pulmonary levels of complement C3a associated with improved lung injury scores. However, levels of pro-inflammatory mediators were unaffected.

CONCLUSION

In a murine model of TRALI, C1-inhibitor attenuated pulmonary levels of C3a associated with improved lung injury scores, but with persistent high levels of inflammatory cytokines.

Transfusion-related acute lung injury: a clinical review

Three decades ago, transfusion-related acute lung injury (TRALI) was considered a rare complication of transfusion medicine. Nowadays, the US Food and Drug Administration acknowledge the syndrome as the leading cause of transfusion-related mortality. Understanding of the pathogenesis of TRALI has resulted in the design of preventive strategies from a blood-bank perspective. A major breakthrough in efforts to reduce the incidence of TRALI has been to exclude female donors of products with high plasma volume, resulting in a decrease of roughly two-thirds in incidence. However, this strategy has not completely eradicated the complication. In the past few years, research has identified patient-related risk factors for the onset of TRALI, which have empowered physicians to take an individualised approach to patients who need transfusion.

Methylprednisolone fails to attenuate lung injury in a mouse model of transfusion related acute lung injury

BACKGROUND

Transfusion-related acute lung injury (TRALI) is the leading cause of transfusion-related morbidity and mortality. Anecdotally, TRALI patients have been treated with corticosteroids. However, evidence for its therapeutic rationale in TRALI is lacking. We determined the effects of corticosteroids on lung injury in a "two-hit" mouse model of antibody-mediated TRALI.

STUDY DESIGN AND METHODS

BALB/c mice were primed with lipopolysaccharide, after which TRALI was induced by injecting major histocompatibility complex (MHC)-I antibody against H2K(d) . Mice infused with phosphate-buffered saline served as controls. Simultaneously, one group of TRALI mice was infused with methylprednisolone (MPS; 2 mg/kg). Mice were supported by mechanical ventilation for 2 hours, after which bronchoalveolar lavage fluid (BALF) and lung homogenate were obtained. Statistics were obtained by one-way analysis of variance or Kruskal-Wallis.

RESULTS

Injection of MHC-I antibodies resulted in TRALI, indicated by pulmonary edema and increased BALF levels of protein and the proinflammatory mediators macrophage inflammatory protein-2, keratinocyte-derived chemokine, and interleukin (IL)-6. Administration of MPS did not affect the amount of edema nor pulmonary protein and chemokine levels. MPS reduced systemic inflammatory reaction as well as IL-6 levels in the BALF.

CONCLUSION

In a two-hit model of antibody-mediated TRALI, MPS attenuated the IL-6 host response, but failed to prevent the development of lung injury.

Age of red blood cells and transfusion in critically ill patients

Red blood cells (RBC) storage facilitates the supply of RBC to meet the clinical demand for transfusion and to avoid wastage. However, RBC storage is associated with adverse changes in erythrocytes and their preservation medium. These changes are responsible for functional alterations and for the accumulation of potentially injurious bioreactive substances. They also may have clinically harmful effects especially in critically ill patients. The clinical consequences of storage lesions, however, remain a matter of persistent controversy. Multiple retrospective, observational, and single-center studies have reported heterogeneous and conflicting findings about the effect of blood storage duration on morbidity and/or mortality in trauma, cardiac surgery, and intensive care unit patients. Describing the details of this controversy, this review not only summarizes the current literature but also highlights the equipoise that currently exists with regard to the use of short versus current standard (extended) storage duration red cells in critically ill patients and supports the need for large, randomized, controlled trials evaluating the clinical impact of transfusing fresh (short duration of storage) versus older (extended duration of storage) red cells in critically ill patients.

Transfusion-related acute lung injury: a preventable syndrome?

Transfusion-related acute lung injury (TRALI) is the leading cause of transfusion-related morbidity and mortality. Recent insights into the pathophysiology of TRALI have led to various preventive strategies. Strategies in donor management range from antibody testing of sensitized donors to the deferral of female plasma donors altogether. However, knowledge on the efficacy of measures to reduce TRALI is limited. In addition, the various measures may lead to a substantial loss of donors, hampering steady blood supply. Thereby, consensus among countries and blood-collecting facilities regarding the optimal strategy to prevent TRALI is lacking. In this review, the advantages and disadvantages of various preventive measures to prevent TRALI are discussed, related to both patient factors as well as blood component-processing strategies, including transfusion policy, donor management and practices of preparation and storage conditions of blood components.

Transfusion-related acute lung injury: Current understanding and preventive strategies

Transfusion-related acute lung injury (TRALI) is the most serious complication of transfusion medicine. TRALI is defined as the onset of acute hypoxia within 6 hours of a blood transfusion in the absence of hydrostatic pulmonary oedema. The past decades have resulted in a better understanding of the pathogenesis of this potentially life-threating syndrome. The present notion is that the onset of TRALI follows a threshold model in which both patient and transfusion factors are essential. The transfusion factors can be divided into immune and non-immune mediated TRALI. Immune-mediated TRALI is caused by the passive transfer of human neutrophil antibodies (HNA) or human leukocyte antibodies (HLA) present in the blood product reacting with a matching antigen in the recipient. Non-immune mediated TRALI is caused by the transfusion of stored cell-containing blood products. Although the mechanisms behind immune-mediated TRALI are reasonably well understood, this is not the case for non-immune mediated TRALI. The increased understanding of pathways involved in the onset of immune-mediated TRALI has led to the design of preventive strategies. Preventive strategies are aimed at reducing the risk to exposure of HLA and HNA to the recipient of the transfusion. These strategies include exclusion of "at risk" donors and pooling of high plasma volume products and have shown to reduce the TRALI incidence effectively. This review discusses the current understanding of TRALI and preventive strategies available.

A threshold model for the susceptibility to transfusion-related acute lung injury

Transfusion-related acute lung injury (TRALI) is a serious, often life-threatening pulmonary transfusion reaction characterized by non-cardiogenic lung oedema, hypoxemia and respiratory distress in temporal association with blood transfusion. The critical mechanism in TRALI is the sudden increase in permeability of the pulmonary endothelium and the subsequent, often extensive shift of fluid into the alveolae. The rapid clinical recovery seen in most patients makes it likely that this is a temporary phenomenon. Reactive oxygen species released by neutrophils or other cells are attractive candidate mediators of this process. There is experimental and clinical evidence that several pathways can induce barrier breakdown in TRALI, a concept known as the threshold model of TRALI. Surprisingly, neutrophils may not always be required. Other cells may play a role as multipliers or attenuators of TRALI, depending on recipient-related and transfusion-related factors involved. This review will summarize recent findings on pathophysiology, with a focus on newly discovered or disenchanted recipient-related and transfusion-related risk factors for TRALI and will present the threshold model of TRALI as a unifying concept on how TRALI develops.

Mechanical ventilation and the titer of antibodies as risk factors for the development of transfusion-related lung injury

Purpose. Onset of transfusion-related acute lung injury (TRALI) is suggested to be a threshold-event. Data is lacking on the relation between titer of antibodies infused and onset of TRALI. We determined whether onset of TRALI is dependent on the titer of MHC-I antibodies infused in a combined model of ventilator-induced lung injury and antibody-induced TRALl. Methods. BALB/c mice were ventilated for five hours with low (7.5 ml/kg) or high (15 ml/kg) tidal volume. After three hours of MV, TRALI was induced by infusion of 0.5 mg/kg, 2.0 mg/kg or 4.5 mg/kg MHC-I antibodies. Control animals received vehicle. After five hours of MV, animals were sacrificed. Results. MV with high tidal volumes resulted in increased levels of all markers of lung injury compared to animals ventilated with low tidal MV. In ventilator-induced lung injury, infusion of 4.5 mg/kg of antibodies further increased pulmonary wet-to-dry ratio, pulmonary neutrophil influx and pulmonary KC levels, whereas infusion of lower dose of antibodies did not augment lung injury. In contrast, mice ventilated with low tidal volumes did not develop lung injury, irrespective of the dose of antibody used. Conclusions. In the presence of injurious MV, onset of TRALI depends on the titer of antibodies infused.

Lack of evidence of CD40 ligand involvement in transfusion-related acute lung injury

Activated platelets have been implicated in playing a major role in transfusion-related acute lung injury (TRALI), as platelets can trigger neutrophils, resulting in vascular damage. We hypothesized that binding of platelet CD40 ligand (CD40L) to endothelial CD40 is essential in the onset of TRALI. Mice were challenged with monoclonal major histocompatibility complex (MHC)-1 antibody which induced TRALI, evidenced by pulmonary oedema, accompanied by significantly elevated bronchoalveolar fluid (BALF) levels of total protein and elevated plasma levels of keratinocyte-derived chemokine (KC) and macrophage inflammatory protein-2 (MIP-2) compared to infusion of isotype antibody (all Ps < 0·05). Treatment with ciglitazone, which inhibits platelet CD40L expression, had no effect on pulmonary and systemic inflammation compared to controls. In addition, treatment with anti-CD40L antibody, which antagonizes all CD40-CD40L interactions, also did not abrogate the TRALI reaction. Furthermore, levels of soluble CD40L were measured in a cohort of cardiac surgery patients, who were followed prospectively for the onset of TRALI after transfusion. Plasma levels of sCD40L at baseline and at time of developing TRALI did not differ between TRALI patients and controls (transfused cardiac surgery patients not developing acute lung injury) (275 ± 192 versus 258 ± 346 and 93 ± 82 versus 93 ± 123 pg/ml, respectively, not significant). In conclusion, these results do not support the idea that the CD40-CD40L interaction is involved in mediating TRALI.

A novel in vivo ovine model of transfusion-related acute lung injury (TRALI)

BACKGROUND AND OBJECTIVES

Even with the introduction of specific risk-reduction strategies, transfusion-related acute lung injury (TRALI) continues to be a leading cause of transfusion-related morbidity and mortality. Existing small animal models have not yet investigated TRALI resulting from the infusion of heat-treated supernatant from whole blood platelet concentrates. In this study, our objective was the development of a novel in vivo two-event model of TRALI in sheep.

MATERIALS AND METHODS

Lipopolysaccharide (LPS; 15 μg/kg) as a first event, modelled clinical infection. Transfusion (estimated at 10% of total blood volume) of heat-treated pooled supernatant from date-of-expire human whole blood platelet concentrates (d5-PLT-S/N) was used as a second event. TRALI was defined by both hypoxaemia that developed either during the transfusion or within two hours of its completion and post-mortem histological evidence of pulmonary oedema.

RESULTS

LPS infusion did not cause lung injury itself, but did result in decreased circulating levels of lymphocytes and neutrophils with evidence of the latter becoming sequestered in the lungs. Sheep that received LPS (first event) followed by d5-PLT-S/N (second event) displayed decreased pulmonary compliance, decreased end tidal CO(2) and increased arterial partial pressure of CO(2) relative to control sheep, and 80% of these sheep developed TRALI.

CONCLUSIONS

This novel ovine two-event TRALI model presents a new tool for the investigation of TRALI pathogenesis. It represents the first description of an in vivo large animal model of TRALI and the first description of TRALI caused by transfusion with heat-treated pooled supernatant from human whole blood platelet concentrates.

Transfusion-related acute lung injury: emerging importance of host factors and implications for management

Recent insights from models of transfusion-related acute lung injury (TRALI), and from clinical reports, reveal that host factors are important in TRALI pathogenesis. Predisposing factors with lung neutrophil-priming capacity, such as sepsis and mechanical ventilation, increase susceptibility for a TRALI reaction, and can aggravate the course of disease. These findings may explain the higher incidence of TRALI in the critically ill compared with general hospital populations. The emerging importance of host factors may have implications for TRALI management. Suspected TRALI cases in which another acute lung injury risk factor is present (termed 'possible TRALI' in the consensus definition) should be reported to the blood bank, including patients suffering from an underlying condition. In reporting of TRALI cases, use of the international TRALI consensus definition should be used, rather then national TRALI scoring systems, to ensure a uniform approach, which may decrease variance in estimations of incidence. In terms of treatment of TRALI patients, there is a rationale to apply therapeutic strategies, which have proven to be beneficial in acute lung injury.

The incidence, risk factors, and outcome of transfusion-related acute lung injury in a cohort of cardiac surgery patients: a prospective nested case-control study

Transfusion-related acute lung injury (TRALI) is the leading cause of transfusion-related morbidity and mortality. Both antibodies and bioactive lipids that have accumulated during storage of blood have been implicated in TRALI pathogenesis. In a single-center, nested, case-control study, patients were prospectively observed for onset of TRALI according to the consensus definition. Of 668 patients, 16 patients (2.4%) developed TRALI. Patient-related risk factors for onset of TRALI were age and time on the cardiopulmonary bypass. Transfusion-related risk factors were total amount of blood products (odds ratio [OR] = 1.2; 95% confidence interval [CI], 1.03-1.44), number of red blood cells stored more than 14 days (OR = 1.6; 95% CI, 1.04-2.37), total amount of plasma (OR = 1.2; 95% CI, 1.03-1.44), presence of antibodies in donor plasma (OR = 8.8; 95% CI, 1.8-44), and total amount of transfused bioactive lipids (OR = 1.0; 95% CI, 1.00-1.07). When adjusted for patient risk factors, only the presence of antibodies in the associated blood products remained a risk factor for TRALI (OR = 14.2; 95% CI, 1.5-132). In-hospital mortality of TRALI was 13% compared with 0% and 3% in transfused and nontransfused patients, respectively (P < .05). In conclusion, the incidence of TRALI is high in cardiac surgery patients and associated with adverse outcome. Our results suggest that cardiac surgery patients may benefit from exclusion of blood products containing HLA/HNA antibodies.

The effect of red blood cell transfusion on 90-day mortality in patients with acute lung injury

BACKGROUND

Erythrocyte blood transfusions are commonly given to intensive care unit (ICU) patients. Recent studies have suggested that transfusions may increase, have no effect on, or decrease short-term mortality. These disparate results may reflect different patient populations, diseases, and characteristics; different transfusion triggers and thresholds; or differences in controlling for confounding variables. The aim of this study was to determine the association of transfusion and 90-day mortality in patients with acute lung injury.

METHODS

Retrospective analysis using binary logistic regression and then propensity analysis to control for variables on the day of the transfusion decision. One thousand patients initially enrolled in ARDSNET 05 Fluid and Catheter Treatment Trial.

RESULTS

A total of 361 patients (36%) received transfusions during the 8-day course of the study and by univariable analysis were more likely to be dead by 90 days (131 of 361, 36%, vs. 153 of 639, 24%, P < .001). After multivariable correction using propensity analysis to control for factors present on the day the transfusion was given, transfusion was not associated with mortality. Instead, factors such as hypotension and laboratory values as measured by propensity scores that predicted transfusion on days 1, 2, and 5 were associated with increased mortality, and not transfusion itself.

CONCLUSION

In patients suffering with acute lung injury, transfusion of erythrocytes in the ICU was not associated with 90-day mortality.