Blood transfusions increase circulating plasma free hemoglobin levels and plasma nitric oxide consumption: a prospective observational pilot study

Carbon nitride reinforced chitosan/sodium alginate hydrogel as high-performance adsorbents for free hemoglobin removal in vitro and in vivo

Removing free hemoglobin generated during extracorporeal circulation remains a challenge. Currently, there is no adsorbent with specificity and good biosafety for removing hemoglobin. In this study, a new chitosan/sodium alginate/carbon nitride (CS/SA/C3N4) hydrogel adsorbent was prepared by blending SA with C3N4 to drop into CS/CaCl2 solution. The physicochemical properties of CS/SA/C3N4 hydrogel were evaluated using some techniques, including scanning electron microscope, Zeta potential measurement, and thermogravimetric analysis. Hemoglobin adsorption in vitro, stability, hemocompatibility, cell compatibility, inflammatory reaction and blood extracorporeal circulation in vivo were also evaluated. The findings revealed that the CS/SA/C3N4-0.4 % hydrogel exhibited an impressive adsorption capacity of 142.35 mg/g for hemoglobin. The kinetic data of hemoglobin adsorption were well-described by pseudo second-order model, while the isothermal model data conformed to the Langmuir model. The hardness and modulus of CS/SA/C3N4-0.4 % was 11.7 KPa and 94.66 KPa respectively, which indicated robust resistance to breakage. CS/SA/C3N4 demonstrated excellent hemocompatibility, biocompatibility and anti-inflammatory properties. In addition, the results of in vivo rabbit extracorporeal blood circulation experiment demonstrated that CS/SA/C3N4 could adsorb free hemoglobin from blood while maintaining high biosafety standard. Consequently, CS/SA/C3N4 hydrogel emerges as a promising candidate for use as a hemoglobin adsorbent in extracorporeal blood circulation system.

Plasma Nitric Oxide Consumption Is Elevated and Associated With Adverse Outcomes in Critically Ill Patients

OBJECTIVES

Impaired nitric oxide (NO) bioavailability may contribute to microvascular dysfunction in sepsis. Excessive plasma NO consumption has been attributed to scavenging by circulating cell-free hemoglobin. This may be a mechanism for NO deficiency in sepsis and critical illness. We hypothesized that plasma NO consumption is high in critically ill patients, particularly those with sepsis, acute respiratory distress syndrome (ARDS), shock, and in hospital nonsurvivors. We further hypothesized that plasma NO consumption is correlated with plasma cell-free hemoglobin concentration.

DESIGN

Retrospective cohort study.

SETTING

Adult ICUs of an academic medical center.

PATIENTS AND SUBJECTS

Three hundred sixty-two critically ill patients and 46 healthy control subjects.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Plasma NO consumption was measured using reductive chemiluminescence and cell-free hemoglobin was measured with a colorimetric assay. Mean (95% CI) plasma NO consumption (µM) was higher in critically ill patients versus healthy control subjects (3.9 [3.7-4.1] vs 2.1 [1.8-2.5]), septic versus nonseptic patients (4.1 [3.8-4.3] vs 3.6 [3.3-3.8]), ARDS versus non-ARDS patients (4.4 [4.0-4.9] vs 3.7 [3.6-3.9]), shock vs nonshock patients (4.4 [4.0-4.8] vs 3.6 [3.4-3.8]), and hospital nonsurvivors versus survivors (5.3 [4.4-6.4] vs 3.7 [3.6-3.9]). These relationships remained significant in multivariable analyses. Plasma cell-free hemoglobin was weakly correlated with plasma NO consumption.

CONCLUSIONS

Plasma NO consumption is elevated in critically ill patients and independently associated with sepsis, ARDS, shock, and hospital death. These data suggest that excessive intravascular NO scavenging characterizes sepsis and adverse outcomes of critical illness.

High level of intraoperative lactate might predict acute kidney injury in aortic arch surgery via minimally invasive approach in patients with type A dissection

Background

A high incidence of acute kidney injury (AKI) has been recorded in total arch replacement (TAR) combined with frozen elephant trunk (FET) implantation in patients with acute type A dissection (ATAAD) via median sternotomy approach with some risk factors. However, the independent risk factors for AKI via a minimally invasive approach have not yet been identified.

Methods

A total of 207 patients with ATAAD were enrolled from January 2018 and November 2019 and were divided into AKI and non-AKI groups. The current surgical strategy was TAR combined with FET via a single upper hemisternotomy approach, a minimally invasive method. An increase in the serum creatinine (Cr) level to ≥2 times the baseline level 48 h post-surgery was defined as AKI. The morbidity of AKI was investigated with a step-by-step backward multivariate analysis of its independent risk factors and a receiver-operating characteristic curve analysis.

Results

Postoperative AKI was observed in 39 (18.8%) patients, and the total hospital mortality was 8.7%. Univariate analysis found that preoperative Cr, weight, circulatory arrest time ≥60 min, intraoperative highest lactate (Lac), and intraoperative transfusion had significant differences between the two groups. However, multivariate step-by-step backward logistic regression analysis identified intraoperative highest Lac and transfusion as independent risk factors for postoperative AKI and intraoperative highest Lac was identified as the most critical independent risk factor estimated by the partial chi-square statistic minus the predicted degrees of freedom with 4.3 mmol/L as the optimal cut-off point for prediction for AKI.

Conclusions

Intraoperative highest Lac and transfusion were independent risk factors for postoperative AKI, which led to high hospital mortality. Moreover, intraoperative highest Lac was the most critical independent risk factor and high level of intraoperative highest Lac (4.3 mmol/L) might predict for postoperative AKI.

Impact of fluid balance and blood transfusion during extracorporeal circulation on outcome for acute type A aortic dissection surgery

BACKGROUND

In thoracic aortic surgery, fluid replacement and blood transfusion during extracorporeal circulation (ECC) are associated with increased coagulopathy, elevated inflammatory response, and end-organ dysfunction. The optimal strategy has not been established in this regard. The aim of this study was to evaluate the effect of the fluid balance during ECC in thoracic aortic dissection surgery on outcome.

METHODS

Between 2009 and 2020, 358 patients suffering from acute type A aortic dissection (ATAAD) underwent aortic surgery at our heart center. In-hospital mortality, major complications (postoperative stroke, respiratory failure, heart failure, acute renal failure), and follow-up mortality were assessed. Logistic regression analysis was used to identify whether fluid balance and blood transfusion during ECC were risk factors for occurring adverse events.

RESULTS

The in-hospital mortality amounted to 20.4%. Major complications included temporary neurologic deficit in 13.4%, permanent neurologic deficit in 6.1%, acute renal failure in 32.7%, prolonged ventilation for respiratory failure in 17.9%, and acute heart failure in 10.9% of cases. At a mean of 42 months after discharge of 285 survivors, follow-up mortality was 13.3%. Multivariate analysis revealed major complications as well as the risk of in-hospital and follow-up mortality to increase with fluid balance and blood transfusion during ECC.

CONCLUSIONS

Fluid balance and blood transfusion during ECC present with predictive potential concerning the risk of postoperative adverse events.

Association between in-ICU red blood cells transfusion and 1-year mortality in ICU survivors

BACKGROUND

Impact of in-ICU transfusion on long-term outcomes remains unknown. The purpose of this study was to assess in critical-care survivors the association between in-ICU red blood cells transfusion and 1-year mortality.

METHODS

FROG-ICU, a multicenter European study enrolling all-comers critical care patients was analyzed (n = 1551). Association between red blood cells transfusion administered in intensive care unit and 1-year mortality in critical care survivors was analyzed using an augmented inverse probability of treatment weighting-augmented inverse probability of censoring weighting method to control confounders.

RESULTS

Among the 1551 ICU-survivors, 42% received at least one unit of red blood cells while in intensive care unit. Patients in the transfusion group had greater severity scores than those in the no-transfusion group. According to unweighted analysis, 1-year post-critical care mortality was greater in the transfusion group compared to the no-transfusion group (hazard ratio (HR) 1.78, 95% CI 1.45-2.16). Weighted analyses including 40 confounders, showed that transfusion remained associated with a higher risk of long-term mortality (HR 1.21, 95% CI 1.06-1.46).

CONCLUSIONS

Our results suggest a high incidence of in-ICU RBC transfusion and that in-ICU transfusion is associated with a higher 1-year mortality among in-ICU survivors. Trial registration ( NCT01367093 ; Registered 6 June 2011).

Hemolytic anemia blunts the cytokine response to transfusion of older red blood cells in mice and dogs

BACKGROUND

Transfusion of red blood cells (RBCs) stored for longer durations induces hemolysis and inflammatory cytokine production in murine and canine models. Despite immune system activation by stored RBCs, human randomized trials suggest that fresher RBC transfusions do not improve clinical outcomes. We hypothesized that underlying recipient hemolysis may affect cytokine responses to older RBC transfusions.

STUDY DESIGN AND METHODS

C57BL/6 mouse cohorts were infused with anti-TER119 antibody to induce hemolysis, rabbit anti-platelet antiserum to induce immune thrombocytopenia (ITP), or appropriate control antibodies. Two days later, mice were transfused with fresh or stored RBCs. Furthermore, in a prospective, randomized, blinded trial, 38 client-owned dogs with primary autoimmune hemolytic anemia (AIHA) and two dogs with ITP, requiring RBC transfusion, were enrolled and randomized to receive fresh (≤7 days) or old (≥21 days) stored RBC transfusions. Monocyte chemoattractant protein (MCP)-1 levels were assessed at defined times after transfusion.

RESULTS

Prior immune-mediated hemolysis blunted the MCP-1 response to stored RBC transfusion in mice (361 ± 111 pg/ml vs. 6836 ± 1528 pg/ml in mice with immune hemolysis vs. ITP, respectively; mean ± SD; p < .0001). Although hemolysis markers increased after transfusion of older RBCs, the cytokine response was also muted in dogs with AIHA. No differences in morbidity or mortality were evident comparing dogs randomized to fresh or old RBCs.

CONCLUSION

These data suggest that underlying hemolysis blunts inflammatory responses to old RBC transfusions. The canine data support randomized trial results suggesting a lack of clinical benefit with fresh RBC transfusions in subjects with underlying, baseline hemolysis.

Blood Transfusion and Acute Kidney Injury After Total Aortic Arch Replacement for Acute Stanford Type A Aortic Dissection

AIM

To evaluate the effect of packed red blood cells (pRBCs), fresh frozen plasma (FFP), and platelet concentrate (PC) transfusions on acute kidney injury (AKI) in patients with acute Stanford type A aortic dissection (ATAAD) with total arch replacement (TAR).

METHOD

From December 2015 to October 2017, 421 consecutive patients with ATAAD undergoing TAR were included in the study. The clinical data of the patients and the amount of pRBCs, FFP, and PC were collected. Acute kidney injury was defined using the Kidney Disease: Improving Global Outcomes (KDIGO) criteria. Logistic regression was used to identify whether pRBCs, FFP, and platelet transfusions were risk factors for KDIGO AKI, stage 3 AKI, and AKI requiring renal replacement therapy (RRT).

RESULTS

The mean ± standard deviation age of the patients was 47.67±10.82 years; 77.7% were men; and the median time from aortic dissection onset to operation was 1 day (range, 0-2 days). The median transfusion amount was 8 units (range, 4-14 units) for pRBCs, 400 mL (range, 0-800 mL) for FFP, and no units (range, 0-2 units) for PC. Forty-one (41; 9.7%) patients did not receive any blood products. The rates of pRBC, PC, and FFP transfusions were 86.9%, 49.2%, and 72.9%, respectively. The incidence of AKI was 54.2%. Considering AKI as the endpoint, multivariate logistic regression showed that pRBCs (odds ratio [OR], 1.11; p<0.001) and PC transfusions (OR, 1.28; p=0.007) were independent risk factors. Considering KDIGO stage 3 AKI as the endpoint, multivariate logistic regression showed that pRBC transfusion (OR, 1.15; p<0.001), PC transfusion (OR, 1.28; p<0.001), a duration of cardiopulmonary bypass (CPB) ≥293 minutes (OR, 2.95; p=0.04), and a creatinine clearance rate of ≤85 mL/minute (OR, 2.12; p=0.01) were independent risk factors. Considering RRT as the endpoint, multivariate logistic regression showed that pRBC transfusion (OR, 1.12; p<0.001), PC transfusion (OR, 1.33; p=0.001), a duration of CPB ≥293 minutes (OR, 3.79; p=0.02), and a creatinine clearance rate of ≤85 mL/minute (OR, 3.34; p<0.001) were independent risk factors.

CONCLUSIONS

Kidney Disease: Improving Global Outcomes-defined stage AKI was common after TAR for ATAAD. Transfusions of pRBCs and PC increased the incidence of AKI, stage 3 AKI, and RRT. Fresh frozen plasma transfusion was not a risk factor for AKI.

Toxic effects of cell-free hemoglobin on the microvascular endothelium: implications for pulmonary and nonpulmonary organ dysfunction

Levels of circulating cell-free hemoglobin are elevated during hemolytic and inflammatory diseases and contribute to organ dysfunction and severity of illness. Though several studies have investigated the contribution of hemoglobin to tissue injury, the precise signaling mechanisms of hemoglobin-mediated endothelial dysfunction in the lung and other organs are not yet completely understood. The purpose of this review is to highlight the knowledge gained thus far and the need for further investigation regarding hemoglobin-mediated endothelial inflammation and injury to develop novel therapeutic strategies targeting the damaging effects of cell-free hemoglobin.

Evaluation of cellular changes in blood stored for transfusion at Bungoma County Referral Hospital, Kenya

Introduction

during the storage of transfusion blood, it may undergo a series of cellular changes that in speculation could be the reason behind the risk of using prolonged stored blood. It's important therefore to monitor the cellular changes that may reduce its survival and function. The objective was to assess the cellular changes in whole blood stored for transfusion at Bungoma county referral hospital.

Methods

a single center, prospective and observational study design involving 20 randomly selected donor blood units in citrate phosphate dextrose adenine (CPDA-1) anticoagulant was employed, cellular changes were evaluated for 35 days. The changes were tested using the Celtac F Haematology analyzer. Statistical Analysis of variance was employed in the descriptive statistics. All the investigation was executed using statistical package for social sciences (SPSS V.23). Results were regarded as significant at P<0.05. Results were presented in tables and charts.

Results

at the end of the 35 days blood storage at blood bank conditions, WBC, RBC, platelets counts and MCHC decreased significantly (P<0.0001, =0.0182, <0.0001, =0.0035). The MCV, HCT and MCH increased significantly (P <0.0001, =0.0003, =0.0115) while HGB had insignificant variance (P =0.4185).

Conclusion

platelets, WBC, RBC counts, and indices are significantly altered in stored blood especially when stored over two weeks based on most of the cellular components analyzed in this study. The study, therefore, recommends the utilization of fresh blood to avoid the adverse outcome of cellular changes of reserved blood.

Hemolysis in patients with Extracorporeal Membrane Oxygenation therapy for severe Acute Respiratory Distress Syndrome - a systematic review of the literature

The Acute Respiratory Distress Syndrome (ARDS) is common in patients on the Intensive Care Unit and associated with significant mortality rates. In situations of severe respiratory insufficiency and failure of all possible conservative therapeutic approaches, veno-venous extracorporeal membrane oxygenation (VV ECMO) is used as a final option for temporary replacement of pulmonary function. ARDS as well as sepsis and VV ECMO treatment are all associated with intravascular hemolysis. The extent and relevance of intravascular hemolysis in the context of ARDS therapy is unclear. This systematic review aims to summarize the current evidence on the incidence and associated complications of intravascular hemolysis in adult patients with ARDS and treatment with VV ECMO. The databases MEDLINE, EMBASE and Web of Science were systematically searched and 19 publications fulfilled inclusion criteria. The incidence of hemolysis in patients with ARDS and treatment with VV ECMO ranged from 0 to 41% with survivors showing lower incidences and less severe hemolysis. A pump head thrombosis and high blood flows (≥3 l/min) as well as use of dual-lumen cannulas but not different pump models were associated with increased hemolysis. In conclusion, intravascular hemolysis in patients with ARDS and treatment with VV ECMO is a common and relevant complication that appears associated with increased mortality. Apart from ECMO hardware-settings, no additional possible causes for increased red cell breakdown such as disease severity, duration of ECMO therapy, or number and quality of red blood cell transfusions were investigated. Further research is needed to determine the origin and relevance of intravascular hemolysis in patients with ARDS and treatment with VV ECMO.

In vitro iatrogenic hemolysis of canine packed red blood cells during various rapid transfusion techniques

OBJECTIVE

To evaluate which rapid blood administration technique causes the least iatrogenic hemolysis in canine packed red blood cells (pRBCs) as determined by plasma free hemoglobin (fHb) and percent hemolysis (% hemolysis).

DESIGN

Prospective in vitro randomized study.

SETTING

Private referral center.

ANIMALS

None.

INTERVENTIONS

Thirteen units of canine pRBCs were divided equally into 5 aliquots, resulting in 65 trials. The aliquots of each unit were subjected to the following administration techniques: gravity-driven (control), an infusion pump at maximal rate, application of a pressure bag, manual compression, and syringe bolus. Plasma fHb and % hemolysis were recorded before and after each trial. Rate of administration (mL/s) was calculated for each method.

MEASUREMENTS AND MAIN RESULTS

Compared to the control, there were no significant increases in % hemolysis or plasma fHb noted among any of the trial methods. The manual compression and syringe bolus methods resulted in the fastest transfusion rates, whereas the infusion pump was not faster than the gravity-driven method. Despite a storage time of ≤14 days, 15% of pRBC units had unsuitable (>0.8%) hemolysis before even being subjected to the trials.

CONCLUSIONS

Commonly used rapid infusion techniques in small animal transfusion medicine do not cause significant iatrogenic hemolysis of canine pRBCs in vitro, although a significant risk is present in stored blood. This suggests that if an expedited transfusion is needed, any method described in this study could be considered, although stored pRBCs should be tested for unsuitable levels of hemolysis prior to transfusion.

Mixing commonly used crystalloid solutions with red blood cells in five common additives does not negatively impact hemolysis, aggregometry, or deformability

BACKGROUND

Literature is beginning to challenge the belief that it is unsafe to coinfuse red blood cells (RBCs) with solutions other than isotonic saline. We recently showed that additive-free RBCs tolerated coincubation with Plasma-Lyte or catecholamines dissolved in normal saline (NS), though 5% dextrose in water (D5W) promoted hemolysis. Herein, we evaluate the effect of coincubating crystalloids on additive-preserved RBC hemolysis, aggregation, and membrane deformability.

STUDY DESIGN AND METHODS

RBCs were coincubated 5 minutes with plasma, NS, Plasma-Lyte, lactated Ringer's (LR) or D5W (1 mL PRBC +131.3 μL solution). Samples were then assessed for hemolysis (free hemoglobin), aggregation (critical shear stress [mPa]), and membrane deformability (elongation index [EI]). Significance (P ≤ .05) by t test or ANOVA with post-hoc Tukey-Kramer test.

RESULTS

Additive-prepared RBCs coincubated with crystalloid instead of plasma demonstrated: (a) no increase in hemolysis as indicated by plasma free hemoglobin levels that is likely to be clinically relevant; (b) no increase, but in some cases a decrease, in aggregation as indicated by critical shear stress; and (c) in some combinations, a deterioration in deformability. When present, the deformability decrease was likely clinically insignificant in degree, and always returned to normal when the crystalloid was subsequently diluted out with plasma.

CONCLUSION

Our data suggest that additive-prepared RBCs coincubated for 5 minutes with any of four common crystalloids demonstrate no clinically relevant increased lysis, increased aggregation, or decreased deformability.

Spatial and temporal patterns of nitric oxide diffusion and degradation drive emergent cerebrovascular dynamics

Nitric oxide (NO) is a gaseous signaling molecule that plays an important role in neurovascular coupling. NO produced by neurons diffuses into the smooth muscle surrounding cerebral arterioles, driving vasodilation. However, the rate of NO degradation in hemoglobin is orders of magnitude higher than in brain tissue, though how this might impact NO signaling dynamics is not completely understood. We used simulations to investigate how the spatial and temporal patterns of NO generation and degradation impacted dilation of a penetrating arteriole in cortex. We found that the spatial location of NO production and the size of the vessel both played an important role in determining its responsiveness to NO. The much higher rate of NO degradation and scavenging of NO in the blood relative to the tissue drove emergent vascular dynamics. Large vasodilation events could be followed by post-stimulus constrictions driven by the increased degradation of NO by the blood, and vasomotion-like 0.1-0.3 Hz oscillations could also be generated. We found that these dynamics could be enhanced by elevation of free hemoglobin in the plasma, which occurs in diseases such as malaria and sickle cell anemia, or following blood transfusions. Finally, we show that changes in blood flow during hypoxia or hyperoxia could be explained by altered NO degradation in the parenchyma. Our simulations suggest that many common vascular dynamics may be emergent phenomena generated by NO degradation by the blood or parenchyma.

Respiratory conditions in coronavirus disease 2019 (COVID-19): Important considerations regarding novel treatment strategies to reduce mortality

A novel virus named 2019 novel coronavirus (2019-nCoV/SARS-CoV-2) causes symptoms that are classified as coronavirus disease (COVID-19). Respiratory conditions are extensively described among more serious cases of COVID-19, and the onset of acute respiratory distress syndrome (ARDS) is one of the hallmark features of critical COVID-19 cases. ARDS can be directly life-threatening because it is associated with low blood oxygenation levels and can result in organ failure. There are no generally recognized effective treatments for COVID-19, but treatments are urgently needed. Anti-viral medications and vaccines are in the early developmental stages and may take many months or even years to fully develop. At present, management of COVID-19 with respiratory and ventilator support are standard therapeutic treatments, but unfortunately such treatments are associated with high mortality rates. Therefore, it is imperative to consider novel new therapeutic interventions to treat/ameliorate respiratory conditions associated with COVID-19. Alternate treatment strategies utilizing clinically available treatments such as hyperbaric oxygen therapy (HBOT), packed red blood cell (pRBC) transfusions, or erthropoiesis-stimulating agent (ESA) therapy were hypothesized to increase oxygenation of tissues by alternative means than standard respiratory and ventilator treatments. It was also revealed that alternative treatments currently being considered for COVID-19 such as chloroquine and hydroxychloroquine by increasing hemoglobin production and increasing hemoglobin availability for oxygen binding and acetazolamine (for the treatment of altitude sickness) by causing hyperventilation with associated increasing levels of oxygen and decreasing levels of carbon dioxide in the blood may significantly ameliorate COVID-19 respiratory symptoms. In conclusion, is recommend, given HBOT, pRBC, and ESA therapies are currently available and routinely utilized in the treatment of other conditions, that such therapies be tried among COVID-19 patients with serious respiratory conditions and that future controlled-clinical trials explore the potential usefulness of such treatments among COVID-19 patients with respiratory conditions.

Factors associated with hemolysis during extracorporeal membrane oxygenation (ECMO)-Comparison of VA- versus VV ECMO

Venovenous (VV) and venoarterial (VA) extracorporeal membrane oxygenation (ECMO) are effective support modalities to treat critically ill patients. ECMO-associated hemolysis remains a serious complication. The aim was to disclose similarities and differences in VA- and VV ECMO-associated hemolysis. This is a retrospective single-center analysis (January 2012 to September 2018) including 1,063 adult consecutive patients (VA, n = 606; VV, n = 457). Severe hemolysis (free plasma hemoglobin, fHb > 500 mg/l) during therapy occurred in 4% (VA) and 2% (VV) (p≤0.001). VV ECMO showed significantly more hemolysis by pump head thrombosis (PHT) compared to VA ECMO (9% vs. 2%; p≤0.001). Pretreatments (ECPR, cardiac surgery) of patients who required VA ECMO caused high fHb pre levels which aggravates the proof of ECMO-induced hemolysis (median (interquartile range), VA: fHb pre: 225.0 (89.3–458.0); VV: fHb pre: 72.0 (42.0–138.0); p≤0.001). The survival rate to discharge from hospital differed depending on ECMO type (40% (VA) vs. 63% (VV); p≤0.001). Hemolysis was dominant in VA ECMO patients, mainly caused by different indications and not by the ECMO support itself. PHT was the most severe form of ECMO-induced hemolysis that occurs in both therapies with low frequency, but more commonly in VV ECMO due to prolonged support time.

The Results of Cardiac Surgery in Terms of Patient Blood Management in Our Hospital

Objective

Clinic of Anaesthesiology and Reanimation, Türkiye Yüksek İhtisas Training and Research Hospital, beginning in 2014, the patient blood management (PBM) protocol is individualised based on patients' comorbidities, and the threshold for transfusion is 7 g dL^-1 of haemoglobin for patients without comorbidities and 8-9 g dL^-1 for patients with comorbidities. In this study, our aim was to compare patient outcomes, requirement for transfusion and the cost of transfusion between two different periods with and without PBM protocol.

Methods

229 and 283 patients who underwent open-heart surgery using cardiopulmonary bypass during the first 4 months of 2012 and the first 4 months of 2017, respectively, were included in this retrospective, cross-sectional study.

Results

There were no differences between the groups in preoperative data. Blood and blood product usage was observed to be significantly lower at the time of the PBM protocol. The use of packed red blood cells decreased from 2 units to 0and that of fresh frozen plasma decreased from 2 units to 0. In terms of postoperative mortality, there were no differences between the groups.

Conclusion

According to the results of this study, the transfusion of unnecessary blood and blood products was reduced and the cost decreased with PBM protocol. Blood product usage did not affect 30-day mortality. It will be possible to achieve more valuable results if more patients are assessed, PBM protocol is implemented and postoperative results are evaluated in detail.

S100A8 acts as an autocrine priming signal for heme-induced human Mϕ pro-inflammatory responses in hemolytic inflammation

Intravascular hemolysis, in addition to reducing red cell counts, incurs extensive vascular inflammation and oxidative stress. One product of hemolysis, heme, is a potent danger associated molecular pattern (DAMP), activating leukocytes and inducing cytokine expression and processing, among other pro-inflammatory effects. We explored pathways by which heme-induced inflammation may be amplified under sterile conditions. Incubation of human Mϕs, differentiated from CD14⁺ cells, with heme induced time- and concentration-dependent gene and protein expression of S100A8, a myeloid cell-derived alarmin. Human Mϕ stimulation with recombinant S100A8, in turn, induced robust pro-IL-1β expression that was dependent upon NF-κB activation, gene transcription, and partially dependent upon TLR4-mediated signaling. Moreover, heme itself stimulated significant Mϕ pro-IL-1β gene and protein expression via an S100A8-mediated mechanism and greatly amplified S100A8-driven NLRP3 inflammasome-mediated IL-1β secretion. In vivo, induction of acute intravascular hemolysis in mice induced a rapid elevation of plasma S100A8 that could be abolished by hemopexin, a heme scavenger. Finally, plasma S100A8 levels were found to be significantly elevated in patients with the inherited hemolytic anemia, sickle cell anemia, when compared with levels in healthy individuals. In conclusion, we demonstrate that hemolytic processes are associated with S100A8 generation and that some of the inflammatory effects of heme may be amplified by autocrine S100A8 production. Findings suggest a mechanism by which hemolytic inflammation could be propagated via leukocyte priming by endogenous proteins, even in sterile inflammatory environments such as those that occur in the hemolytic diseases. S100A8 may represent a therapeutic target for reducing inflammation in hemolytic disorders.

Total plasma heme concentration increases after red blood cell transfusion and predicts mortality in critically ill medical patients

BACKGROUND

Relationships between red blood cell (RBC) transfusion, circulating cell-free heme, and clinical outcomes in critically ill transfusion recipients are incompletely understood. The goal of this study was to determine whether total plasma heme increases after RBC transfusion and predicts mortality in critically ill patients.

STUDY DESIGN AND METHODS

This was a prospective cohort study of 111 consecutive medical intensive care patients requiring RBC transfusion. Cell-free heme was measured in RBC units before transfusion and in the patients' plasma before and after transfusion.

RESULTS

Total plasma heme levels increased in response to transfusion, from a median (interquartile range [IQR]) of 35 (26-76) μmol/L to 47 (35-73) μmol/L (p < 0.001). Posttransfusion total plasma heme was higher in nonsurvivors (54 [35-136] μmol/L) versus survivors (44 [31-65] μmol/L, p = 0.03). Posttransfusion total plasma heme predicted hospital mortality (odds ratio [95% confidence interval] per quartile increase in posttransfusion plasma heme, 1.76 [1.17-2.66]; p = 0.007). Posttransfusion total plasma heme was not correlated with RBC unit storage duration and weakly correlated with RBC unit cell-free heme concentration.

CONCLUSIONS

Total plasma heme concentration increases in critically ill patients after RBC transfusion and is independently associated with mortality. This transfusion-associated increase in total plasma heme is not fully explained by RBC unit storage age or cell-free heme content. Additional studies are warranted to define mechanisms of transfusion-related plasma heme accumulation and test prevention strategies.

Red blood cell transfusion and outcomes in acute pulmonary embolism

BACKGROUND AND OBJECTIVE

Blood transfusion has been associated with adverse outcomes in certain conditions. This study investigates the prevalence and outcomes of red blood cell (RBC) transfusion in patients with acute pulmonary embolism (PE).

METHODS

Retrospective study of consecutive patients from 2000 to 2012 admitted to a tertiary hospital with a primary diagnosis of acute PE. Transfusion status during the hospital admission was ascertained. Mortality was tracked from a state-wide death database and analysed using multivariable modelling.

RESULTS

A total of 73 patients (5% of all patients admitted with PE) received RBC transfusion during their admission. These patients were significantly older, had more co-morbidities, worse haemodynamics, higher simplified pulmonary embolism severity index scores, and lower plasma sodium and haemoglobin (Hb) levels at admission. Unadjusted mortality for the transfused group was significantly higher at 30-day (19% vs 4%, P < 0.001) and 6-month (40% vs 10%, P < 0.001) follow-up. Multivariable modelling showed RBC transfusion to be a significant independent predictor of mortality at 30-day (odds ratio 3.06, 95% CI: 1.17-8.01, P = 0.02) and 6-month (hazard ratio (HR) 1.97, 95% CI: 1.12-3.46, P = 0.02). Sensitivity analysis confirmed that transfused patients had higher mortality than non-transfused patients in the subgroup of patients with Hb <100 g/L.

CONCLUSION

RBC transfusion in patients hospitalized with acute PE is rare and appears to be associated with increased risk of short- and long-term mortality, independent of Hb level on admission. This finding underscores the need for future randomized controlled studies on the impact of RBC transfusion in the management of patients admitted with acute PE. [Correction added on 4 May 2018, after first online publication: the word 'serum' was changed to 'plasma' throughout the article where appropriate.].

Pathophysiology and Management of Acute Respiratory Distress Syndrome in Children

Acute respiratory distress syndrome (ARDS) is a syndrome of noncardiogenic pulmonary edema and hypoxia that accompanies up to 30% of deaths in pediatric intensive care units. Pediatric ARDS (PARDS) is diagnosed by the presence of hypoxia, defined by oxygenation index or Pao₂/Fio₂ ratio cutoffs, and new chest infiltrate occurring within 7 days of a known insult. Hallmarks of ARDS include hypoxemia and decreased lung compliance, increased work of breathing, and impaired gas exchange. Mortality is often accompanied by multiple organ failure. Although many modalities to treat PARDS have been investigated, supportive therapies and lung protective ventilator support remain the mainstay.

Expediting red blood cell transfusions by syringing causes significant hemolysis

BACKGROUND

Techniques commonly used to expedite blood transfusions include pneumatically pressurizing red blood cell (RBC) bags or manual syringing its contents. We compared these techniques on RBC hemolysis using a simulated transfusion model.

STUDY DESIGN AND METHODS

Fifteen warmed RBC units that were 12.3 ± 4.3 (95% confidence interval [CI], 10.1-14.5) days old were each subjected to two experimental rapid transfusion techniques. RBCs from each technique were directed through 18- and 22-gauge cannulas attached to blood administration sets. One technique involved RBC bag pressurization to 300 mmHg. The other employed a 20-mL syringe to effect forceful, manual aspiration from the RBC bag followed by forceful, manual RBC injection. The control group was gravity driven without cannulas. Free hemoglobin (Hb) concentrations were measured and percent hemolysis was calculated.

RESULTS

Free Hb concentrations and percent hemolysis (median [95% CI]) were similar in the control (0.05 [0.03-0.08] g/dL and 0.13% [0.09%-0.17%], respectively) and pressurized experiments (0.06 [0.05-0.09] g/dL; 0.14% [0.12%-0.22%]), respectively. Syringing resulted in 10-fold higher free Hb concentrations (0.55 [0.38-0.92] g/dL) and percent hemolysis (1.28% [1.03%-2.15%]) than when employing the control (p < 0.0001) or pressurization (p < 0.0001) techniques. Cannula sizes studied did not affect hemolysis.

CONCLUSION

Forceful manual syringing caused significant hemolysis and high free Hb concentrations. Pressurizing RBC bags induced no more hemolysis than after gravity-facilitated transfusions. Syringing to expedite RBC transfusions should be avoided in favor of pneumatic RBC bag pressurization.

Point-of-care washing of allogeneic red blood cells for the prevention of transfusion-related respiratory complications (WAR-PRC): a protocol for a multicenter randomised clinical trial in patients undergoing cardiac surgery

INTRODUCTION

The transfusion-related respiratory complications, transfusion-related acute lung injury (TRALI) and transfusion-associated circulatory overload (TACO), are leading causes of transfusion-related morbidity and mortality. At present, there are no effective preventive strategies with red blood cell (RBC) transfusion. Although mechanisms remain incompletely defined, soluble biological response modifiers (BRMs) within the RBC storage solution may play an important role. Point-of-care (POC) washing of allogeneic RBCs may remove these BRMs, thereby mitigating their impact on post-transfusion respiratory complications.

METHODS AND ANALYSIS

This is a multicenter randomised clinical trial of standard allogeneic versus washed allogeneic RBC transfusion for adult patients undergoing cardiac surgery testing the hypothesis that POC RBC washing is feasible, safe, and efficacious and will reduce recipient immune and physiologic responses associated with transfusion-related respiratory complications. Relevant clinical outcomes will also be assessed. This investigation will enrol 170 patients at two hospitals in the USA. Simon's two-stage design will be used to assess the feasibility of POC RBC washing. The primary safety outcomes will be assessed using Wilcoxon Rank-Sum tests for continuous variables and Pearson chi-square test for categorical variables. Standard mixed modelling practices will be employed to test for changes in biomarkers of lung injury following transfusion. Linear regression will assess relationships between randomised group and post-transfusion physiologic measures.

ETHICS AND DISSEMINATION

Safety oversight will be conducted under the direction of an independent Data and Safety Monitoring Board (DSMB). Approval of the protocol was obtained by the DSMB as well as the institutional review boards at each institution prior to enrolling the first study participant. This study aims to provide important information regarding the feasibility of POC washing of allogeneic RBCs and its potential impact on ameliorating post-transfusion respiratory complications. Additionally, it will inform the feasibility and scientific merit of pursuing a more definitive phase II/III clinical trial.

REGISTRATION

ClinicalTrials.gov registration number is NCT02094118 (Pre-results).

Morphology, membrane nanostructure and stiffness for quality assessment of packed red blood cells

Transfusion of packed red blood cells (PRBC) to patients in critical states is often accompanied by post-transfusion complications. This may be related with disturbance of properties of PRBC and their membranes during long-term storage in the hemopreservative solution. The purpose of our work is the study of transformation of morphology, membranes stiffness and nanostructure for assessment of PRBC quality, in vitro. By atomic force microscopy we studied the transformation of cell morphology, the appearance of topological nanodefects of membranes and by atomic force spectroscopy studied the change of membrane stiffness during 40 days of storage of PRBC. It was shown that there is a transition period (20–26 days), in which we observed an increase in the Young’s modulus of the membranes 1.6–2 times and transition of cells into irreversible forms. This process was preceded by the appearance of topological nanodefects of membranes. These parameters can be used for quality assessment of PRBC and for improvement of transfusion rules.

Risk of Postoperative Venous Thromboembolism Among Pregnant Women

Venous thromboembolism (VTE) is a critical complication after surgery. Although pregnancy is a known risk factor of VTE, available data on the risk of postoperative VTE are scarce. Using the American College of Surgeons National Surgical Quality Improvement Program database between 2006 and 2012, we matched 2,582 pregnant women to 103,640 nonpregnant women based on age, race, body mass index, and modified Rogers score. Pregnant women, compared with matched nonpregnant women, experienced higher incidence of VTE (0.5% vs 0.3%; odds ratio 1.93, 95% confidence interval 1.1 to 3.37, p = 0.02). Pregnant women also showed higher risk of pneumonia, ventilator dependence ≥48 hours, bleeding, and sepsis than did the counterparts. In conclusion, pregnancy was associated with higher risk of VTE after surgery as well as other postoperative complications. The absolute risk difference was small, and careful evaluation against the potential risk and benefit should be given when surgical treatment is considered among pregnant women.

Transfusion-related immunomodulation and cancer

Blood and blood-component therapy triggers immunological reactions in recipients. Transfusion-related immunomodulation [TRIM] is an important complex biological immune reaction to transfusion culminating in immunosuppression. The mechanisms underlying TRIM include the presence of residual leukocytes and apoptotic cells, the transfusion of immunosuppressive cytokines either present in donor components or generated during blood processing, the transfer of metabolically active growth factor-loaded microparticles and extracellular vesicles and the presence of free hemoglobin or extracellular vesicle-bound hemoglobin. TRIM variables include donor-specific factors as well as processing variables. TRIM may explain, at least in part, the controversial negative clinical outcomes observed in cancer patients receiving transfusion in the context of curative-intent surgeries. The use of novel technologies including metabolomics and proteomics on stored blood may pave the way for a deeper understanding of TRIM in general and its impact on cancer progression.

Iron accelerates hemoglobin oxidation increasing mortality in vascular diseased guinea pigs following transfusion of stored blood

Non-transferrin-bound iron (NTBI) and free hemoglobin (Hb) accumulate in circulation following stored RBC transfusions. This study investigated transfusion, vascular disease, and mortality in guinea pigs after stored RBC transfusion alone and following cotransfusion with apo-transferrin (apo-Tf) and haptoglobin (Hp). The effects of RBC exchange transfusion dose (1, 3, and 9 units), storage period (14 days), and mortality were evaluated in guinea pigs with a vascular disease phenotype. Seven-day mortality and the interaction between iron and Hb as cocontributors to adverse outcome were studied. Concentrations of iron and free Hb were greatest after transfusion with 9 units of stored RBCs compared with fresh RBCs or stored RBCs at 1- and 3-unit volumes. Nine units of stored RBCs led to mortality in vascular diseased animals, but not normal animals. One and 3 units of stored RBCs did not cause a mortality effect, suggesting the concomitant relevance of NTBI and Hb on outcome. Cotransfusion with apo-Tf or Hp restored survival to 100% following 9-unit RBC transfusions in vascular diseased animals. Our data suggest that increases in plasma NTBI and Hb contribute to vascular disease-associated mortality through iron-enhanced Hb oxidation and enhanced tissue injury.

Blood transfusions may impair endothelium-dependent vasodilatation during coronary artery bypass surgery

OBJECTIVE

The hemolytic product free-hemoglobin (fHb) reduces nitric oxide (NO) bioavailability. The present study aims to establish whether administration of different blood transfusions result in increased circulating fHb levels and NO consumption with effects on arterial NO-dependent blood flow in patients undergoing CABG surgery.

METHODS

Ninety-five consecutive patients undergoing elective CABG surgery were prospectively divided in four groups based on blood transfusion requirements during surgery: stored blood cells (SBC, n. 21), intraoperative autologous salvaged blood (ASB, n. 25), SBC and ASB (n.22), no transfusion (control, n. 27). Blood samples were collected before and after intervention to analyse plasma levels of fHb and NO consumption. Endothelium-dependent relaxation was assessed in left internal mammary artery (LIMA) rings harvested before chest closure. Peripheral artery tonometry was assessed after intervention.

RESULTS

Transfusions with SBC increased plasma fHb (p<0.05). Transfusions of ASB resulted in higher plasma fHb compared to SBC (p<0.01). fHb concentrations directly correlated with NO consumption (r=0.65, p<0.001). Maximal endothelium-dependent relaxation in LIMA was significantly attenuated in SBC and ASB patients compared to control (15.2±3.1% vs 21.1±2.5% vs 43±5.0% respectively; p<0.01). Significant correlations were identified between the aortic pressure wave velocity, plasma fHb concentration and NO consumption (p<0.01).

CONCLUSIONS

Intraoperative blood transfusions and particularly autologous salvaged blood impair endothelium-dependent relaxation through NO scavenging by fHb. These findings obtained in vitro and in vivo provide new insights into the adverse relation between blood transfusions and patient outcome.

Pulmonary and Systemic Vascular Resistances After Cardiopulmonary Bypass: Role of Hemolysis

OBJECTIVES

Prolonged cardiopulmonary bypass (CPB) is associated with hemolysis, resulting in increased plasma oxyhemoglobin and vascular nitric oxide depletion. The authors hypothesized that hemolysis associated with CPB would reduce nitric oxide bioavailability, resulting in high pulmonary and systemic vascular resistances that after CPB would normalize gradually over time, due to clearance of plasma oxyhemoglobin. The authors also investigated whether prolonged CPB (≥140 min) produced increased levels of hemolysis and greater pulmonary and systemic vasoconstriction.

DESIGN

Prospective cohort study.

SETTING

Single-center university hospital.

PATIENTS

The study comprised 50 patients undergoing elective cardiac surgery requiring CPB.

INTERVENTIONS

Plasma hemoglobin and plasma nitric oxide consumption were measured before surgery and after CPB. Pulmonary and systemic hemodynamics were measured after CPB. The effects of short (<140 min) and prolonged (≥140 min) CPB on these parameters were considered.

MEASUREMENTS AND MAIN RESULTS

Pulmonary and systemic vascular resistances and plasma hemoglobin and nitric oxide consumption were highest at 15 minutes after CPB and then decreased over time. Pulmonary and systemic vascular resistances and plasma hemoglobin and plasma nitric oxide consumption were higher in patients requiring prolonged CPB. The reduction in plasma nitric oxide consumption from 15 minutes to 4 hours after CPB was correlated independently with the reductions in pulmonary and systemic vascular resistances.

CONCLUSIONS

Prolonged CPB was associated with increased plasma hemoglobin and plasma nitric oxide consumption and pulmonary and systemic vascular resistances. The reduction in plasma nitric oxide consumption at 4 hours after CPB was an independent predictor of the concomitant reductions in pulmonary and systemic vascular resistances.

The controversy over the age of blood: what do the clinical trials really teach us?

Red blood cell transfusions have been used in clinical practice for decades and represent the most common therapeutic procedure performed in hospitalised patients. Depending on the storage solution and national regulatory requirements, red blood cells can be stored in the refrigerator up to 42 days before transfusion. We reviewed five of the most recent randomised clinical trials that examined clinical outcomes in specific patient populations. Although these studies provide some comfort regarding our current standard of care, they do not address whether the oldest blood is associated with harm in certain patient populations.

Postoperative goal-directed therapy and development of acute kidney injury following major elective noncardiac surgery: post-hoc analysis of POM-O randomized controlled trial

Background: The role of goal-directed therapy (GDT) in preventing creatinine rise following noncardiac surgery is unclear. We performed a post-hoc analysis of a randomized controlled trial to assess the relationship between postoperative optimization of oxygen delivery and development of acute kidney injury (AKI)/creatinine rise following noncardiac surgery.

Methods: Patients were randomly assigned immediately postoperatively to receive either fluid and/or dobutamine therapy to maintain/restore their preoperative oxygen delivery, or protocolized standard care (oxygen delivery only recorded). Primary end point was serial changes in postoperative creatinine within 48 h postoperatively. Secondary outcomes were development of AKI (KDIGO criteria) and minimal creatinine rise (MCR; no decline from preoperative creatinine), related to all-cause morbidity and length of stay.

Results: Postoperative reductions in serum creatinine were similar (P = 0.76) in patients randomized to GDT [10 µmol/L (95% confidence interval, CI: 17 to −1); n = 95] or protocolized care [8 µmol/L (95% CI: 17 to −6); n = 92]. Postoperative haemodynamic management was not associated with the development of MCR [78/187 (41.7%)] or AKI [13/187; (7.0%)]. Intraoperative requirement for norepinephrine was more likely in patients who developed postoperative rises in creatinine [relative risk (RR): 1.66 (95% CI: 1.04–2.67); P = 0.04], despite similar volumes of intraoperative fluid being administered. Persistently higher lactate during the intervention period was associated with AKI (mean difference: 1.15 mmol/L (95% CI: 0.48–1.81); P = 0.01]. Prolonged hospital stay was associated with AKI but not MCR [RR: 2.71 (95% CI: 1.51–4.87); P = 0.0008].

Conclusion: These data provide further insights into how perioperative haemodynamic alterations relate to postoperative increases in creatinine once systemic inflammation is established.

B-type natriuretic peptide and plasma hemoglobin levels following transfusion of shorter-storage versus longer-storage red blood cells: Results from the TOTAL randomized trial

BACKGROUND

Prior studies have suggested that transfusion of stored red blood cells (RBCs) with increased levels of cell-free hemoglobin might reduce the bioavailability of recipient nitric oxide (NO) and cause myocardial strain.

METHODS

Ugandan children (ages 6-60 months) with severe anemia and lactic acidosis were randomly assigned to receive RBCs stored 1-10 days versus 25-35 days. B-type natriuretic peptide (BNP), vital signs, renal function test results, and plasma hemoglobin were measured. Most children had either malaria or sickle cell disease and were thus at risk for reduced NO bioavailability.

RESULTS

Seventy patients received RBCs stored 1-10 days, and 77 received RBCs stored 25-35 days. The median (interquartile range) cell-free hemoglobin was nearly 3 times higher in longer-storage RBCs (26.4 [15.5-43.4] μmol/L) than in shorter-storage RBCs (10.8 [7.8-18.6] μmol/L), P < .0001. Median (interquartile range) BNP 2 hours posttransfusion was 156 (59-650) pg/mL (shorter storage) versus 158 (59-425) pg/mL (longer storage), P = .76. BNP values 22 hours posttransfusion were 110 (46-337) pg/mL (shorter storage) versus 96 (49-310) pg/mL (longer storage), P = .76. Changes in BNP within individuals from pretransfusion to 2 hours (or 22 hours) posttransfusion were not significantly different between the study groups. BNP change following transfusion did not correlate with the concentration of cell-free hemoglobin in the RBC supernatant. Blood pressure, blood urea nitrogen, creatinine, and change in plasma hemoglobin were not significantly different in the 2 groups.

CONCLUSION

In a randomized trial among children at risk for reduced NO bioavailability, we found that BNP, blood pressure, creatinine, and plasma hemoglobin were not higher in patients receiving RBCs stored for 25-35 versus 1-10 days.

TIMP2•IGFBP7 biomarker panel accurately predicts acute kidney injury in high-risk surgical patients

Supplemental digital content is available in the text.

BACKGROUND

Acute kidney injury (AKI) is an important complication in surgical patients. Existing biomarkers and clinical prediction models underestimate the risk for developing AKI. We recently reported data from two trials of 728 and 408 critically ill adult patients in whom urinary TIMP2•IGFBP7 (NephroCheck, Astute Medical) was used to identify patients at risk of developing AKI. Here we report a preplanned analysis of surgical patients from both trials to assess whether urinary tissue inhibitor of metalloproteinase 2 (TIMP-2) and insulin-like growth factor–binding protein 7 (IGFBP7) accurately identify surgical patients at risk of developing AKI.

STUDY DESIGN

We enrolled adult surgical patients at risk for AKI who were admitted to one of 39 intensive care units across Europe and North America. The primary end point was moderate-severe AKI (equivalent to KDIGO [Kidney Disease Improving Global Outcomes] stages 2–3) within 12 hours of enrollment. Biomarker performance was assessed using the area under the receiver operating characteristic curve, integrated discrimination improvement, and category-free net reclassification improvement.

RESULTS

A total of 375 patients were included in the final analysis of whom 35 (9%) developed moderate-severe AKI within 12 hours. The area under the receiver operating characteristic curve for [TIMP-2]•[IGFBP7] alone was 0.84 (95% confidence interval, 0.76–0.90; p < 0.0001). Biomarker performance was robust in sensitivity analysis across predefined subgroups (urgency and type of surgery).

CONCLUSION

For postoperative surgical intensive care unit patients, a single urinary TIMP2•IGFBP7 test accurately identified patients at risk for developing AKI within the ensuing 12 hours and its inclusion in clinical risk prediction models significantly enhances their performance.

LEVEL OF EVIDENCE

Prognostic study, level I.

Technical-Induced Hemolysis in Patients with Respiratory Failure Supported with Veno-Venous ECMO - Prevalence and Risk Factors

The aim of the study was to explore the prevalence and risk factors for technical-induced hemolysis in adults supported with veno-venous extracorporeal membrane oxygenation (vvECMO) and to analyze the effect of hemolytic episodes on outcome. This was a retrospective, single-center study that included 318 adult patients (Regensburg ECMO Registry, 2009–2014) with acute respiratory failure treated with different modern miniaturized ECMO systems. Free plasma hemoglobin (fHb) was used as indicator for hemolysis. Throughout a cumulative support duration of 4,142 days on ECMO only 1.7% of the fHb levels were above a critical value of 500 mg/l. A grave rise in fHb indicated pumphead thrombosis (n = 8), while acute oxygenator thrombosis (n = 15) did not affect fHb. Replacement of the pumphead normalized fHb within two days. Neither pump or cannula type nor duration on the first system was associated with hemolysis. Multiple trauma, need for kidney replacement therapy, increased daily red blood cell transfusion requirements, and high blood flow (3.0–4.5 L/min) through small-sized cannulas significantly resulted in augmented blood cell trauma. Survivors were characterized by lower peak levels of fHb [90 (60, 142) mg/l] in comparison to non-survivors [148 (91, 256) mg/l, p≤0.001]. In conclusion, marked hemolysis is not common in vvECMO with modern devices. Clinically obvious hemolysis often is caused by pumphead thrombosis. High flow velocity through small cannulas may also cause technical-induced hemolysis. In patients who developed lung failure due to trauma, fHb was elevated independantly of ECMO. In our cohort, the occurance of hemolysis was associated with increased mortality.

Red blood cell transfusion is associated with increased hemolysis and an acute phase response in a subset of critically ill children

In healthy adults, transfusion of older stored red blood cells (RBCs) produces extravascular hemolysis and circulating non-transferrin-bound iron. In a prospective, observational study of critically ill children, we examined the effect of RBC storage duration on the extent of hemolysis by comparing laboratory measurements obtained before, and 4 hr after, RBC transfusion (N = 100) or saline/albumin infusion (N = 20). Transfusion of RBCs stored for longer than 4 weeks significantly increased plasma free hemoglobin (P < 0.05), indirect bilirubin (P < 0.05), serum iron (P < 0.001), and non-transferrin-bound iron (P < 0.01). However, days of storage duration poorly correlated (R(2) <0.10) with all measured indicators of hemolysis and inflammation. These results suggest that, in critically ill children, most effects of RBC storage duration on post-transfusion hemolysis are overwhelmed by recipient and/or donor factors. Nonetheless, we identified a subset of patients (N = 21) with evidence of considerable extravascular hemolysis (i.e., increased indirect bilirubin ≥0.4 mg/dL). In these patients, transfusion-associated hemolysis was accompanied by increases in circulating non-transferrin-bound iron and free hemoglobin and by an acute phase response, as assessed by an increase in median C-reactive protein levels of 21.2 mg/L (P < 0.05). In summary, RBC transfusions were associated with an acute phase response and both extravascular and intravascular hemolysis, which were independent of RBC storage duration. The 21% of transfusions that were associated with substantial hemolysis conferred an increased risk of inducing an acute phase response.

The role of red blood cells and cell-free hemoglobin in the pathogenesis of ARDS

The primary focus of research into the pathophysiology of the acute respiratory distress syndrome (ARDS) has been on the interaction between the lung, underlying causes of ARDS, and the role of white blood cells and platelets in contributing to lung injury. Given a lack of specific therapies for this common complication of critical illness, further insight into the pathophysiology of this syndrome is greatly needed to develop targeted interventions. The red blood cell (RBC) has been reported to undergo deleterious changes in critical illness and be present in the alveoli of patients with ARDS. Release of RBC contents is known to be injurious in other conditions but has only recently been studied in critical illness and ARDS. The contribution of the RBC to ARDS represents a new avenue of research that may produce new, targeted therapies for this deadly syndrome.

Acute hemolytic vascular inflammatory processes are prevented by nitric oxide replacement or a single dose of hydroxyurea

Hemolysis and consequent release of cell-free hemoglobin (CFHb) impair vascular nitric oxide (NO) bioavailability and cause oxidative and inflammatory processes. Hydroxyurea (HU), a common therapy for sickle cell disease (SCD), induces fetal Hb production and can act as an NO donor. We evaluated the acute inflammatory effects of intravenous water-induced hemolysis in C57BL/6 mice and determined the abilities of an NO donor, diethylamine NONOate (DEANO), and a single dose of HU to modulate this inflammation. Intravenous water induced acute hemolysis in C57BL/6 mice, attaining plasma Hb levels comparable to those observed in chimeric SCD mice. This hemolysis resulted in significant and rapid systemic inflammation and vascular leukocyte recruitment within 15 minutes, accompanied by NO metabolite generation. Administration of another potent NO scavenger (2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide) to C57BL/6 mice induced similar alterations in leukocyte recruitment, whereas hemin-induced inflammation occurred over a longer time frame. Importantly, the acute inflammatory effects of water-induced hemolysis were abolished by the simultaneous administration of DEANO or HU, without altering CFHb, in an NO pathway-mediated manner. In vitro, HU partially reversed the Hb-mediated induction of endothelial proinflammatory cytokine secretion and adhesion molecule expression. In summary, pathophysiological levels of hemolysis trigger an immediate inflammatory response, possibly mediated by vascular NO consumption. HU presents beneficial anti-inflammatory effects by inhibiting rapid-onset hemolytic inflammation via an NO-dependent mechanism, independently of fetal Hb elevation. Data provide novel insights into mechanisms of hemolytic inflammation and further support perspectives for the use of HU as an acute treatment for SCD and other hemolytic disorders.

Plasma free hemoglobin and microcirculatory response to fresh or old blood transfusions in sepsis

BACKGROUND

Free hemoglobin (fHb) may induce vasoconstriction by scavenging nitric oxide. It may increase in older blood units due to storage lesions. This study evaluated whether old red blood cell transfusion increases plasma fHb in sepsis and how the microvascular response may be affected.

METHODS

This is a secondary analysis of a randomized study. Twenty adult septic patients received either fresh or old (<10 or >15 days storage, respectively) RBC transfusions. fHb was measured in RBC units and in the plasma before and 1 hour after transfusion. Simultaneously, the sublingual microcirculation was assessed with sidestream-dark field imaging. The perfused boundary region was calculated as an index of glycocalyx damage. Tissue oxygen saturation (StO2) and Hb index (THI) were measured with near-infrared spectroscopy and a vascular occlusion test was performed.

RESULTS

Similar fHb levels were found in the supernatant of fresh and old RBC units. Despite this, plasma fHb increased in the old RBC group after transfusion (from 0.125 [0.098-0.219] mg/mL to 0.238 [0.163-0.369] mg/mL, p = 0.006). The sublingual microcirculation was unaltered in both groups, while THI increased. The change in plasma fHb was inversely correlated with the changes in total vessel density (r = -0.57 [95% confidence interval -0.82, -0.16], p = 0.008), De Backer score (r = -0.63 [95% confidence interval -0.84, -0.25], p = 0.003) and THI (r = -0.72 [95% confidence interval -0.88, -0.39], p = 0.0003).

CONCLUSIONS

Old RBC transfusion was associated with an increase in plasma fHb in septic patients. Increasing plasma fHb levels were associated with decreased microvascular density.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01584999.

The pathophysiology and consequences of red blood cell storage

Red cell transfusion therapy is a common treatment modality in contemporary medical practice. Although blood collection and administration is safer and more efficient than ever before, red cells undergo multiple metabolic and structural changes during storage that may compromise their functionality and viability following transfusion. The clinical relevance of these changes is a hotly debated topic that continues to be a matter of intense investigation. In the current review, we begin with an in-depth overview of the pathophysiological mechanisms underlying red cell storage, with a focus on altered metabolism, oxidative stress and red cell membrane damage. We proceed to review the current state of evidence on the clinical relevance and consequences of the red cell storage lesion, while discussing the strengths and limitations of clinical studies.

Hemolysis during cardiac surgery is associated with increased intravascular nitric oxide consumption and perioperative kidney and intestinal tissue damage

Introduction: Acute kidney injury (AKI) and intestinal injury negatively impact patient outcome after cardiac surgery. Enhanced nitric oxide (NO) consumption due to intraoperative intravascular hemolysis, may play an important role in this setting. This study investigated the impact of hemolysis on plasma NO consumption, AKI, and intestinal tissue damage, after cardiac surgery.

Methods: Hemolysis (by plasma extracellular (free) hemoglobin; fHb), plasma NO-consumption, plasma fHb-binding capacity by haptoglobin (Hp), renal tubular injury (using urinary N-Acetyl-β-D-glucosaminidase; NAG), intestinal mucosal injury (through plasma intestinal fatty acid binding protein; IFABP), and AKI were studied in patients undergoing off-pump cardiac surgery (OPCAB, N = 7), on-pump coronary artery bypass grafting (CABG, N = 30), or combined CABG and valve surgery (CABG+Valve, N = 30).

Results: FHb plasma levels and NO-consumption significantly increased, while plasma Hp concentrations significantly decreased in CABG and CABG+Valve patients (p < 0.0001) during surgery. The extent of hemolysis and NO-consumption correlated significantly (r² = 0.75, p < 0.0001). Also, NAG and IFABP increased in both groups (p < 0.0001, and p < 0.001, respectively), and both were significantly associated with hemolysis (R_s = 0.70, p < 0.0001, and R_s = 0.26, p = 0.04, respectively) and NO-consumption (R_s = 0.55, p = 0.002, and R_s = 0.41, p = 0.03, respectively), also after multivariable logistic regression analysis. OPCAB patients did not show increased fHb, NO-consumption, NAG, or IFABP levels. Patients suffering from AKI (N = 9, 13.4%) displayed significantly higher fHb and NAG levels already during surgery compared to non-AKI patients.

Conclusions: Hemolysis appears to be an important contributor to postoperative kidney injury and intestinal mucosal damage, potentially by limiting NO-bioavailability. This observation offers a novel diagnostic and therapeutic target to improve patient outcome after cardiothoracic surgery.

Theoretical modelling of fibrinogen supplementation with therapeutic plasma, cryoprecipitate, or fibrinogen concentrate

Background

We aimed to create a theoretical tool to model the effect of three haemostatic agents containing fibrinogen (therapeutic plasma, cryoprecipitate, and fibrinogen concentrate) on the patient's plasma fibrinogen level.

Methods

A mathematical model was developed step-wise. The relationship between the amount of haemostatic agent and plasma fibrinogen level was plotted for each agent. A fibrinogen concentration simulator (FCS_amount) was developed, where the amount of haemostatic agent was calculated from patient characteristics, agent characteristics, and target plasma fibrinogen level. Refinements were introduced so that (i) FCS_amount would account for in vivo fibrinogen recovery, (ii) circulatory volume would not increase ad infinitum with increasing amounts, and (iii) red blood cells would be included in the simulation if haematocrit decreased below a certain level. A second FCS (FCS_level) was created to calculate fibrinogen levels resulting from specified amounts of haemostatic agents.

Results

Fibrinogen concentration in haemostatic agents has a critical impact on their ability to increase patients' fibrinogen levels. If the target plasma fibrinogen level approaches the concentration of the fibrinogen source, the required amounts increase exponentially; it is impossible to achieve a target above the concentration of the fibrinogen source.

Conclusions

We successfully developed two theoretical tools answering the questions: ‘How much therapeutic plasma, cryoprecipitate, or fibrinogen concentrate would be needed to achieve a specified target fibrinogen level?’ and ‘What would be the resultant fibrinogen level for a specified amount of haemostatic agent?’ The current tools are not intended for clinical application, but they are potentially useful for educational purposes.