Adverse effects of hemorrhagic shock resuscitation with stored blood are ameliorated by inhaled nitric oxide in lambs*

Large Animal Models for Simulating Physiology of Transfusion of Red Cell Concentrates-A Scoping Review of The Literature

Background and Objectives: Transfusion of red cell concentrates is a key component of medical therapy. To investigate the complex transfusion-associated biochemical and physiological processes as well as potential risks for human recipients, animal models are of particular importance. This scoping review summarizes existing large animal transfusion models for their ability to model the physiology associated with the storage of erythrocyte concentrates. Materials and Methods: The electronic databases PubMed, EMBASE, and Web of Science were systematically searched for original studies providing information on the intravenous application of erythrocyte concentrates in porcine, ovine, and canine animal models. Results: A total of 36 studies were included in the analysis. The majority of porcine studies evaluated hemorrhagic shock conditions. Pig models showed high physiological similarities with regard to red cell physiology during early storage. Ovine and canine studies were found to model typical aspects of human red cell storage at 42 days. Only four studies provided data on 24 h in vivo survival of red cells. Conclusions: While ovine and canine models can mimic typical human erythrocyte storage for up to 42 days, porcine models stand out for reliably simulating double-hit pathologies such as hemorrhagic shock. Large animal models remain an important area of translational research since they have an impact on testing new pharmacological or biophysical interventions to attenuate storage-related adverse effects and allow, in a controlled environment, to study background and interventions in dynamic and severe disease conditions.

Cancer- and cardiac-induced cachexia: same fate through different inflammatory mediators?

BACKGROUND

Inflammation is widely recognized as the driving force of cachexia induced by chronic diseases; however, therapies targeting inflammation do not always reverse cachexia. Thus, whether inflammation per se plays an important role in the clinical course of cachectic patients is still a matter of debate.

AIMS

To give new insights into cachexia's pathogenesis and diagnosis, we performed a comprehensive literature search on the contribution of inflammatory markers to this syndrome, focusing on the noncommunicable diseases cancer and cardiovascular diseases.

METHODS

A systematic review was performed in PubMed using the keywords ("cancer" OR "cardiac" cachexia AND "human" OR "patient" AND "plasma" or "serum"). A total of 744 studies were retrieved and, from these, 206 were selected for full-text screening. In the end, 98 papers focusing on circulating biomarkers of cachexia were identified, which resulted in a list of 113 different mediators.

RESULTS

Data collected from the literature highlight the contribution of interleukin-6 (IL-6) and C-reactive protein (CRP) to cachexia, independently of the underlying condition. Despite not being specific, once the diagnosis of cachexia is established, CRP might help to monitor the effectiveness of anti-cachexia therapies. In cardiac diseases, B-type natriuretic peptide (BNP), renin, and obestatin might be putative markers of body wasting, whereas in cancer, growth differentiation factor (GDF) 15, transforming growth factor (TGF)-β1 and vascular endothelial growth factor (VEGF) C seem to be better markers of this syndrome. Independently of the circulating mediators, NF-κB and JAK/STAT signaling pathways play a key role in bridging inflammation with muscle wasting; however, therapies targeting these pathways were not proven effective for all cachectic patients.

CONCLUSION

The critical and integrative analysis performed herein will certainly feed future research focused on the better comprehension of cachexia pathogenesis toward the improvement of its diagnosis and the development of personalized therapies targeting specific cachexia phenotypes.

Nitric oxide: Clinical applications in critically ill patients

Inhaled nitric oxide (iNO) acts as a selective pulmonary vasodilator and it is currently approved by the FDA for the treatment of persistent pulmonary hypertension of the newborn. iNO has been demonstrated to effectively decrease pulmonary artery pressure and improve oxygenation, while decreasing extracorporeal life support use in hypoxic newborns affected by persistent pulmonary hypertension. Also, iNO seems a safe treatment with limited side effects. Despite the promising beneficial effects of NO in the preclinical literature, there is still a lack of high quality evidence for the use of iNO in clinical settings. A variety of clinical applications have been suggested in and out of the critical care environment, aiming to use iNO in respiratory failure and pulmonary hypertension of adults or as a preventative measure of hemolysis-induced vasoconstriction, ischemia/reperfusion injury and as a potential treatment of renal failure associated with cardiopulmonary bypass. In this narrative review we aim to present a comprehensive summary of the potential use of iNO in several clinical conditions with its suggested benefits, including its recent application in the scenario of the COVID-19 pandemic. Randomized controlled trials, meta-analyses, guidelines, observational studies and case-series were reported and the main findings summarized. Furthermore, we will describe the toxicity profile of NO and discuss an innovative proposed strategy to produce iNO. Overall, iNO exhibits a wide range of potential clinical benefits, that certainly warrants further efforts with randomized clinical trials to determine specific therapeutic roles of iNO.

Old, older, the oldest: red blood cell storage and the potential harm of using older red blood cell concentrates

PURPOSE OF REVIEW

Over the last decades, clinical studies have suggested that transfusion of red blood cells (RBCs) might negatively impact patient outcomes. Even though large randomized clinical trials did not show differences in mortality when transfusing fresh versus standard-issue RBC units, data imply that RBCs at the very end of storage could elicit negative effects.

RECENT FINDINGS

Certain alterations of RBCs during cold storage -- such as an increase of potassium and lactate in the storage solution -- have been discovered a century ago. In recent years, proteomic and metabolomic studies have shed more light into pathophysiological changes of RBCs during storage and have helped to specify the definition of old blood. These advancements are now utilized to increase the quality of stored RBCs and devise therapeutic strategies (e.g. nitric oxide, haptoglobin, or reduction of the iron load) when transfusing old blood.

SUMMARY

Further research to improve the quality of RBC units and to study populations potentially at risk is warranted. Until the question whether transfusion of old blood is detrimental for specific patient populations has been answered, a deliberate use of RBC transfusion should be implemented.

Transfusion of standard-issue packed red blood cells induces pulmonary vasoconstriction in critically ill patients after cardiac surgery-A randomized, double-blinded, clinical trial

BACKGROUND

Experimental and volunteer studies have reported pulmonary vasoconstriction during transfusion of packed red blood cells (PRBCs) stored for prolonged periods. The primary aim of this study was to evaluate whether transfusion of PRBCs stored over 21 days (standard-issue, siPRBCs) increases pulmonary artery pressure (PAP) to a greater extent than transfusion of PRBCs stored for less then 14 days (fresh, fPRBCs) in critically ill patients following cardiac surgery. The key secondary aim was to assess whether the pulmonary vascular resistance index (PVRI) increases after transfusion of siPRBCs to a greater extent than after transfusion of fPRBCs.

METHODS

The study was performed as a single-center, double-blinded, parallel-group, randomized clinical trial. Leukoreduced PRBCs were transfused while continuously measuring hemodynamic parameters. Systemic concentrations of syndecan-1 were measured to assess glycocalyx injury. After randomizing 19 patients between January 2014 and June 2016, the study was stopped due to protracted patient recruitment.

RESULTS

Of 19 randomized patients, 11 patients were transfused and included in statistical analyses. Eight patients were excluded prior to transfusion, 6 patients received fPRBCs (10±3 storage days), whereas 5 patients received siPRBCs (33±4 storage days). The increase in PAP (7±3 vs. 2±2 mmHg, P = 0.012) was greater during transfusion of siPRBCs than during transfusion of fPRBCs. In addition, the change in PVRI (150±89 vs. -4±37 dyn·s·cm-5·m2, P = 0.018) was greater after transfusion of siPRBCs than after transfusion of fPRBCs. The increase in PAP correlated with the change of systemic syndecan-1 concentrations at the end of transfusion (R = 0.64,P = 0.034).

CONCLUSION

Although this study is underpowered and results require verification in larger clinical trials, our findings suggest that transfusion of siPRBCs increases PAP and PVRI to a greater extent than transfusion of fPRBCs in critically ill patients following cardiac surgery. Glycocalyx injury might contribute to pulmonary vasoconstriction associated with transfusion of stored blood.

Inhaled nitric oxide

Nitric oxide (NO) is a gas that induces relaxation of smooth muscle cells in the vasculature. Because NO reacts with oxyhaemoglobin with high affinity, the gas is rapidly scavenged by oxyhaemoglobin in red blood cells and the vasodilating effects of inhaled NO are limited to ventilated regions in the lung. NO therefore has the unique ability to induce pulmonary vasodilatation specifically in the portions of the lung with adequate ventilation, thereby improving oxygenation of blood and decreasing intrapulmonary right to left shunting. Inhaled NO is used to treat a spectrum of cardiopulmonary conditions, including pulmonary hypertension in children and adults. However, the widespread use of inhaled NO is limited by logistical and financial barriers. We have designed, developed and tested a simple and economic NO generation device, which uses pulsed electrical discharges in air to produce therapeutic levels of NO that can be used for inhalation therapy. LINKED ARTICLES: This article is part of a themed section on Nitric Oxide 20 Years from the 1998 Nobel Prize. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.2/issuetoc.

Older Blood Is Associated With Increased Mortality and Adverse Events in Massively Transfused Trauma Patients: Secondary Analysis of the PROPPR Trial

STUDY OBJECTIVE

The transfusion of older packed RBCs may be harmful in critically ill patients. We seek to determine the association between packed RBC age and mortality among trauma patients requiring massive packed RBC transfusion.

METHODS

We analyzed data from the Pragmatic, Randomized Optimal Platelet and Plasma Ratios trial. Subjects in the parent trial included critically injured adult patients admitted to 1 of 12 North American Level I trauma centers who received at least 1 unit of packed RBCs and were predicted to require massive blood transfusion. The primary exposure was volume of packed RBC units transfused during the first 24 hours of hospitalization, stratified by packed RBC age category: 0 to 7 days, 8 to 14 days, 15 to 21 days, and greater than or equal to 22 days. The primary outcome was 24-hour mortality. We evaluated the association between transfused volume of each packed RBC age category and 24-hour survival, using random-effects logistic regression, adjusting for total packed RBC volume, patient age, sex, race, mechanism of injury, Injury Severity Score, Revised Trauma Score, clinical site, and trial treatment group.

RESULTS

The 678 patients included in the analysis received a total of 8,830 packed RBC units. One hundred patients (14.8%) died within the first 24 hours. On multivariable analysis, the number of packed RBCs greater than or equal to 22 days old was independently associated with increased 24-hour mortality (adjusted odds ratio [OR] 1.05 per packed RBC unit; 95% confidence interval [CI] 1.01 to 1.08): OR 0.97 for 0 to 7 days old (95% CI 0.88 to 1.08), OR 1.04 for 8 to 14 days old (95% CI 0.99 to 1.09), and OR 1.02 for 15 to 21 days old (95% CI 0.98 to 1.06). Results of sensitivity analyses were similar only among patients who received greater than or equal to 10 packed RBC units.

CONCLUSION

Increasing quantities of older packed RBCs are associated with increased likelihood of 24-hour mortality in trauma patients receiving massive packed RBC transfusion (≥10 units), but not in those who receive fewer than 10 units.

Role of heme in lung bacterial infection after trauma hemorrhage and stored red blood cell transfusion: A preclinical experimental study

BACKGROUND

Trauma is the leading cause of death and disability in patients aged 1-46 y. Severely injured patients experience considerable blood loss and hemorrhagic shock requiring treatment with massive transfusion of red blood cells (RBCs). Preclinical and retrospective human studies in trauma patients have suggested that poorer therapeutic efficacy, increased severity of organ injury, and increased bacterial infection are associated with transfusion of large volumes of stored RBCs, although the mechanisms are not fully understood.

METHODS AND FINDINGS

We developed a murine model of trauma hemorrhage (TH) followed by resuscitation with plasma and leukoreduced RBCs (in a 1:1 ratio) that were banked for 0 (fresh) or 14 (stored) days. Two days later, lungs were infected with Pseudomonas aeruginosa K-strain (PAK). Resuscitation with stored RBCs significantly increased the severity of lung injury caused by P. aeruginosa, as demonstrated by higher mortality (median survival 35 h for fresh RBC group and 8 h for stored RBC group; p < 0.001), increased pulmonary edema (mean [95% CI] 106.4 μl [88.5-124.3] for fresh RBCs and 192.5 μl [140.9-244.0] for stored RBCs; p = 0.003), and higher bacterial numbers in the lung (mean [95% CI] 1.2 × 10(7) [-1.0 × 10(7) to 2.5 × 10(7)] for fresh RBCs and 3.6 × 10(7) [2.5 × 10(7) to 4.7 × 10(7)] for stored RBCs; p = 0.014). The mechanism underlying this increased infection susceptibility and severity was free-heme-dependent, as recombinant hemopexin or pharmacological inhibition or genetic deletion of toll-like receptor 4 (TLR4) during TH and resuscitation completely prevented P. aeruginosa-induced mortality after stored RBC transfusion (p < 0.001 for all groups relative to stored RBC group). Evidence from studies transfusing fresh and stored RBCs mixed with stored and fresh RBC supernatants, respectively, indicated that heme arising both during storage and from RBC hemolysis post-resuscitation plays a role in increased mortality after PAK (p < 0.001). Heme also increased endothelial permeability and inhibited macrophage-dependent phagocytosis in cultured cells. Stored RBCs also increased circulating high mobility group box 1 (HMGB1; mean [95% CI] 15.4 ng/ml [6.7-24.0] for fresh RBCs and 50.3 ng/ml [12.3-88.2] for stored RBCs), and anti-HMGB1 blocking antibody protected against PAK-induced mortality in vivo (p = 0.001) and restored macrophage-dependent phagocytosis of P. aeruginosa in vitro. Finally, we showed that TH patients, admitted to the University of Alabama at Birmingham ER between 1 January 2015 and 30 April 2016 (n = 50), received high micromolar-millimolar levels of heme proportional to the number of units transfused, sufficient to overwhelm endogenous hemopexin levels early after TH and resuscitation. Limitations of the study include lack of assessment of temporal changes in different products of hemolysis after resuscitation and the small sample size precluding testing of associations between heme levels and adverse outcomes in resuscitated TH patients.

CONCLUSIONS

We provide evidence that large volume resuscitation with stored blood, compared to fresh blood, in mice increases mortality from subsequent pneumonia, which occurs via mechanisms sensitive to hemopexin and TLR4 and HMGB1 inhibition.

Parenteral irons versus transfused red blood cells for treatment of anemia during canine experimental bacterial pneumonia

BACKGROUND

No studies have been performed comparing intravenous (IV) iron with transfused red blood cells (RBCs) for treating anemia during infection. In a previous report, transfused older RBCs increased free iron release and mortality in infected animals when compared to fresher cells. We hypothesized that treating anemia during infection with transfused fresh RBCs, with minimal free iron release, would prove superior to IV iron therapy.

STUDY DESIGN AND METHODS

Purpose-bred beagles (n = 42) with experimental Staphylococcus aureus pneumonia rendered anemic were randomized to be transfused RBCs stored for 7 days or one of two IV iron preparations (7 mg/kg), iron sucrose, a widely used preparation, or ferumoxytol, a newer formulation that blunts circulating iron levels.

RESULTS

Both irons increased the alveolar-arterial oxygen gradient at 24 to 48 hours (p = 0.02-0.001), worsened shock at 16 hours (p = 0.02-0.003, respectively), and reduced survival (transfusion 56%; iron sucrose 8%, p = 0.01; ferumoxytol 9%, p = 0.04). Compared to fresh RBC transfusion, plasma iron measured by non-transferrin-bound iron levels increased with iron sucrose at 7, 10, 13, 16, 24, and 48 hours (p = 0.04 to p < 0.0001) and ferumoxytol at 7, 24, and 48 hours (p = 0.04 to p = 0.004). No significant differences in cardiac filling pressures or performance, hemoglobin (Hb), or cell-free Hb were observed.

CONCLUSIONS

During canine experimental bacterial pneumonia, treatment of mild anemia with IV iron significantly increased free iron levels, shock, lung injury, and mortality compared to transfusion of fresh RBCs. This was true for iron preparations that do or do not blunt circulating free iron level elevations. These findings suggest that treatment of anemia with IV iron during infection should be undertaken with caution.

Risk Factors and Clinical Outcomes Associated with Perioperative Transfusion-associated Circulatory Overload

BACKGROUND

Transfusion-associated circulatory overload remains underappreciated in the perioperative environment. The authors aimed to characterize risk factors for perioperative transfusion-associated circulatory overload and better understand its impact on patient-important outcomes.

METHODS

In this case-control study, 163 adults undergoing noncardiac surgery who developed perioperative transfusion-associated circulatory overload were matched with 726 transfused controls who did not develop respiratory complications. Univariate and multivariable logistic regression analyses were used to evaluate potential risk factors for transfusion-associated circulatory overload. The need for postoperative mechanical ventilation, lengths of intensive care unit and hospital stay, and mortality were compared.

RESULTS

For this cohort, the mean age was 71 yr and 56% were men. Multivariable analysis revealed the following independent predictors of transfusion-associated circulatory overload: emergency surgery, chronic kidney disease, left ventricular dysfunction, previous β-adrenergic receptor antagonist use, isolated fresh frozen plasma transfusion (vs. isolated erythrocyte transfusion), mixed product transfusion (vs. isolated erythrocyte transfusion), and increasing intraoperative fluid administration. Patients who developed transfusion-associated circulatory overload were more likely to require postoperative mechanical ventilation (73 vs. 33%; P < 0.001) and experienced prolonged intensive care unit (11.1 vs. 6.5 days; P < 0.001) and hospital lengths of stay (19.9 vs. 9.6 days; P < 0.001). Survival was significantly reduced (P < 0.001) in transfusion recipients who developed transfusion-associated circulatory overload (1-yr survival 72 vs. 84%).

CONCLUSIONS

Perioperative transfusion-associated circulatory overload was associated with a protracted hospital course and increased mortality. Efforts to minimize the incidence of transfusion-associated circulatory overload should focus on the judicious use of intraoperative blood transfusions and nonsanguineous fluid therapies, particularly in patients with chronic kidney disease, left ventricular dysfunction, chronic β-blocker therapy, and those requiring emergency surgery.

Exposure of Stored Packed Erythrocytes to Nitric Oxide Prevents Transfusion-associated Pulmonary Hypertension

BACKGROUND

Transfusion of packed erythrocytes stored for a long duration is associated with increased pulmonary arterial pressure and vascular resistance. Prolonged storage decreases erythrocyte deformability, and older erythrocytes are rapidly removed from the circulation after transfusion. The authors studied whether treating stored packed ovine erythrocytes with NO before transfusion could prevent pulmonary vasoconstriction, enhance erythrocyte deformability, and prolong erythrocyte survival after transfusion.

METHODS

Ovine leukoreduced packed erythrocytes were treated before transfusion with either NO gas or a short-lived NO donor. Sheep were transfused with autologous packed erythrocytes, which were stored at 4°C for either 2 ("fresh blood") or 40 days ("stored blood"). Pulmonary and systemic hemodynamic parameters were monitored before, during, and after transfusion. Transfused erythrocytes were labeled with biotin to measure their circulating lifespan. Erythrocyte deformability was assessed before and after NO treatment using a microfluidic device.

RESULTS

NO treatment improved the deformability of stored erythrocytes and increased the number of stored erythrocytes circulating at 1 and 24 h after transfusion. NO treatment prevented transfusion-associated pulmonary hypertension (mean pulmonary arterial pressure at 30 min of 21 ± 1 vs. 15 ± 1 mmHg in control and NO-treated packed erythrocytes, P < 0.0001). Washing stored packed erythrocytes before transfusion did not prevent pulmonary hypertension.

CONCLUSIONS

NO treatment of stored packed erythrocytes before transfusion oxidizes cell-free oxyhemoglobin to methemoglobin, prevents subsequent NO scavenging in the pulmonary vasculature, and limits pulmonary hypertension. NO treatment increases erythrocyte deformability and erythrocyte survival after transfusion. NO treatment might provide a promising therapeutic approach to prevent pulmonary hypertension and extend erythrocyte survival.

Haptoglobin or Hemopexin Therapy Prevents Acute Adverse Effects of Resuscitation After Prolonged Storage of Red Cells

BACKGROUND

Extracellular hemoglobin and cell-free heme are toxic breakdown products of hemolyzed erythrocytes. Mammals synthesize the scavenger proteins haptoglobin and hemopexin, which bind extracellular hemoglobin and heme, respectively. Transfusion of packed red blood cells is a lifesaving therapy for patients with hemorrhagic shock. Because erythrocytes undergo progressive deleterious morphological and biochemical changes during storage, transfusion of packed red blood cells that have been stored for prolonged intervals (SRBCs; stored for 35-40 days in humans or 14 days in mice) increases plasma levels of cell-free hemoglobin and heme. Therefore, in patients with hemorrhagic shock, perfusion-sensitive organs such as the kidneys are challenged not only by hypoperfusion but also by the high concentrations of plasma hemoglobin and heme that are associated with the transfusion of SRBCs.

METHODS

To test whether treatment with exogenous human haptoglobin or hemopexin can ameliorate adverse effects of resuscitation with SRBCs after 2 hours of hemorrhagic shock, mice that received SRBCs were given a coinfusion of haptoglobin, hemopexin, or albumin.

RESULTS

Treatment with haptoglobin or hemopexin but not albumin improved the survival rate and attenuated SRBC-induced inflammation. Treatment with haptoglobin retained free hemoglobin in the plasma and prevented SRBC-induced hemoglobinuria and kidney injury. In mice resuscitated with fresh packed red blood cells, treatment with haptoglobin, hemopexin, or albumin did not cause harmful effects.

CONCLUSIONS

In mice, the adverse effects of transfusion with SRBCs after hemorrhagic shock are ameliorated by treatment with either haptoglobin or hemopexin. Haptoglobin infusion prevents kidney injury associated with high plasma hemoglobin concentrations after resuscitation with SRBCs. Treatment with the naturally occurring human plasma proteins haptoglobin or hemopexin may have beneficial effects in conditions of severe hemolysis after prolonged hypotension.

Perioperative Red Blood Cell Transfusion: What We Do Not Know

Objective:

Blood transfusion saves lives but may also increase the risk of injury. The objective of this review was to evaluate the possible adverse effects related to transfusion of red blood cell (RBC) concentrates stored for prolonged periods.

Data Sources:

The data used in this review were mainly from PubMed articles published in English up to February 2015.

Study Selection:

Clinical and basic research articles were selected according to their relevance to this topic.

Results:

The ex vivo changes to RBC that occur during storage are collectively called storage lesion. It is still inconclusive if transfusion of RBC with storage lesion has clinical relevance. Multiple ongoing prospective randomized controlled trials are aimed to clarify this clinical issue. It was observed that the adverse events related to stored RBC transfusion were prominent in certain patient populations, including trauma, critical care, pediatric, and cardiac surgery patients, which leads to the investigation of underlying mechanisms. It is demonstrated that free hemoglobin toxicity, decreasing of nitric oxide bioavailability, and free iron-induced increasing of inflammation may play an important role in this process.

Conclusion:

It is still unclear whether transfusion of older RBC has adverse effects, and if so, which factors determine such clinical effects. However, considering the magnitude of transfusion and the widespread medical significance, potential preventive strategies should be considered, especially for the susceptible recipients.

Effects of Aged Stored Autologous Red Blood Cells on Human Endothelial Function

RATIONALE

A major abnormality that characterizes the red cell "storage lesion" is increased hemolysis and reduced red cell lifespan after infusion. Low levels of intravascular hemolysis after transfusion of aged stored red cells disrupt nitric oxide (NO) bioavailabity, via accelerated NO scavenging reaction with cell-free plasma hemoglobin. The degree of intravascular hemolysis post-transfusion and effects on endothelial-dependent vasodilation responses to acetylcholine have not been fully characterized in humans.

OBJECTIVES

To evaluate the effects of blood aged to the limits of Food and Drug Administration-approved storage time on the human microcirculation and endothelial function.

METHODS

Eighteen healthy individuals donated 1 U of leukopheresed red cells, divided and autologously transfused into the forearm brachial artery 5 and 42 days after blood donation. Blood samples were obtained from stored blood bag supernatants and the antecubital vein of the infusion arm. Forearm blood flow measurements were performed using strain-gauge plethysmography during transfusion, followed by testing of endothelium-dependent blood flow with increasing doses of intraarterial acetylcholine.

MEASUREMENTS AND MAIN RESULTS

We demonstrate that aged stored blood has higher levels of arginase-1 and cell-free plasma hemoglobin. Compared with 5-day blood, the transfusion of 42-day packed red cells decreases acetylcholine-dependent forearm blood flows. Intravascular venous levels of arginase-1 and cell-free plasma hemoglobin increase immediately after red cell transfusion, with more significant increases observed after infusion of 42-day-old blood.

CONCLUSIONS

We demonstrate that the transfusion of blood at the limits of Food and Drug Administration-approved storage has a significant effect on the forearm circulation and impairs endothelial function. Clinical trial registered with www.clinicaltrials.gov (NCT 01137656).

Transfused older stored red blood cells improve the clinical course and outcome in a canine lethal hemorrhage and reperfusion model

BACKGROUND

In canine models, transfused older stored red blood cells (RBCs) hemolyze in vivo resulting in significantly increased intravascular cell-free hemoglobin (CFH) and non-transferrin-bound iron (NTBI). During canine bacterial pneumonia with septic shock, but not in controls, older stored RBCs were associated with significantly increased lung injury and mortality. It is unknown if in shock without infection transfusion of older RBCs will result in similar adverse effects.

STUDY DESIGN AND METHODS

Two-year-old purpose-bred beagles (n = 12) were transfused similar quantities of either older (42-day) or fresher (7-day) stored universal donor canine RBCs 2.5 hours after undergoing controlled hemorrhage (55 mL/kg).

RESULTS

With older transfused RBCs, CFH (p < 0.0001) and NTBI (p = 0.004) levels increased, but lung injury (p = 0.01) and C-reactive protein levels (p = 0.002) declined and there was a trend toward lower mortality (18% vs. 50%). All three deaths after transfused fresher RBCs resulted from hepatic fractures. Lowered exogenous norepinephrine requirements (p < 0.05) and cardiac outputs (p < 0.05) after older transfused RBCs were associated with increased CFH levels that have known vasoconstrictive nitric oxide scavenging capability.

CONCLUSIONS

In hemorrhagic shock, older RBCs altered resuscitation physiology but did not worsen clinical outcomes. Elevated CFH may lower norepinephrine requirements and cardiac outputs ameliorating reperfusion injuries. With hemorrhagic shock, NTBI levels persist in contrast to the increased clearance, lung injury, and mortality in the previously reported infection model. These preclinical data suggest that whereas iron derived from older RBCs promotes bacterial growth, worsening septic shock mortality during infection, release of CFH and NTBI during hemorrhagic shock is not necessarily harmful.

In a canine pneumonia model of exchange transfusion, altering the age but not the volume of older red blood cells markedly alters outcome

BACKGROUND

Massive exchange transfusion of 42-day-old red blood cells (RBCs) in a canine model of Staphylococcus aureus pneumonia resulted in in vivo hemolysis with increases in cell-free hemoglobin (CFH), transferrin-bound iron (TBI), non-transferrin-bound iron (NTBI), and mortality. We have previously shown that washing 42-day-old RBCs before transfusion significantly decreased NTBI levels and mortality, but washing 7-day-old RBCs increased mortality and CFH levels. We now report the results of altering volume, washing, and age of RBCs.

STUDY DESIGN AND METHODS

Two-year-old purpose-bred infected beagles were transfused with increasing volumes (5-10, 20-40, or 60-80 mL/kg) of either 42- or 7-day-old RBCs (n = 36) or 80 mL/kg of either unwashed or washed RBCs with increasing storage age (14, 21, 28, or 35 days; n = 40).

RESULTS

All volumes transfused (5-80 mL/kg) of 42-day-old RBCs resulted in alike (i.e., not significantly different) increases in TBI during transfusion as well as in CFH, lung injury, and mortality rates after transfusion. Transfusion of 80 mL/kg RBCs stored for 14, 21, 28, and 35 days resulted in increased CFH and NTBI in between levels found at 7 and 42 days of storage. However, washing RBCs of intermediate ages (14-35 days) does not alter NTBI and CFH levels or mortality rates.

CONCLUSIONS

Preclinical data suggest that any volume of 42-day-old blood potentially increases risks during established infection. In contrast, even massive volumes of 7-day-old blood result in minimal CFH and NTBI levels and risks. In contrast to the extremes of storage, washing blood stored for intermediate ages does not alter risks of transfusion or NTBI and CFH clearance.

Inhaled nitric oxide therapy for extrapulmonary inflammation

Inhaled nitric oxide (iNO) has been used extensively to treat pulmonary hypertension primarily in newborns. This therapy is a safe and effective therapy to improve the matching between airway ventilation and blood oxygenation. A key conceptual component of iNO therapy is that effects are limited to the pulmonary compartment thereby avoiding unwanted systemic effects. The mechanism underlying this model is that any NO entering the blood stream is rapidly oxidized to nitrate, a relatively inert anion that is excreted. Mediating this oxidation is oxyhemoglobin that becomes oxidized to methemoglobin, accumulation of which is limited by erythrocyte methemoglobin reductase. In this article, we discuss studies that dismiss the notion that once in the blood stream iNO is inactivated and show that a surprising result of iNO therapy is the formation of stable NO-derived products that circulate and can elicit NO-dependent signaling in extra-pulmonary tissues. This pathway has the potential to open up new applications for iNO for treatment of systemic diseases associated with loss of NO signaling.

The influence of the storage lesion(s) on pediatric red cell transfusion

PURPOSE OF REVIEW

This article will analyze and evaluate the current evidence regarding the use of older, longer-stored red blood cells (RBCs) for transfusion in pediatric patients and will examine some of the postulated mechanisms of injury related to prolonged refrigerated storage of RBCs and studies reporting clinical outcomes.

RECENT FINDINGS

Three randomized controlled trials and seven observational studies have been conducted entirely in pediatric patients. The outcomes, mortality and morbidity in critically ill patients and children undergoing cardiac surgery, and necrotizing enterocolitis in premature infants, have been inconsistent. However, many of these studies have been confounded by study design, mixed patient populations, red cell preparation, and other factors.

SUMMARY

Further exploration into the possible deleterious effects of older, longer-stored RBC transfusions on mortality and morbidity in different pediatric populations is merited. Understanding the potential mechanisms of injury should help explain the clinical findings.

Autologous transfusion of stored red blood cells increases pulmonary artery pressure

RATIONALE

Transfusion of erythrocytes stored for prolonged periods is associated with increased mortality. Erythrocytes undergo hemolysis during storage and after transfusion. Plasma hemoglobin scavenges endogenous nitric oxide leading to systemic and pulmonary vasoconstriction.

OBJECTIVES

We hypothesized that transfusion of autologous blood stored for 40 days would increase the pulmonary artery pressure in volunteers with endothelial dysfunction (impaired endothelial production of nitric oxide). We also tested whether breathing nitric oxide before and during transfusion could prevent the increase of pulmonary artery pressure.

METHODS

Fourteen obese adults with endothelial dysfunction were enrolled in a randomized crossover study of transfusing autologous, leukoreduced blood stored for either 3 or 40 days. Volunteers were transfused with 3-day blood, 40-day blood, and 40-day blood while breathing 80 ppm nitric oxide.

MEASUREMENTS AND MAIN RESULTS

The age of volunteers was 41 ± 4 years (mean ± SEM), and their body mass index was 33.4 ± 1.3 kg/m(2). Plasma hemoglobin concentrations increased after transfusion with 40-day and 40-day plus nitric oxide blood but not after transfusing 3-day blood. Mean pulmonary artery pressure, estimated by transthoracic echocardiography, increased after transfusing 40-day blood (18 ± 2 to 23 ± 2 mm Hg; P < 0.05) but did not change after transfusing 3-day blood (17 ± 2 to 18 ± 2 mm Hg; P = 0.5). Breathing nitric oxide decreased pulmonary artery pressure in volunteers transfused with 40-day blood (17 ± 2 to 12 ± 1 mm Hg; P < 0.05).

CONCLUSIONS

Transfusion of autologous leukoreduced blood stored for 40 days was associated with increased plasma hemoglobin levels and increased pulmonary artery pressure. Breathing nitric oxide prevents the increase of pulmonary artery pressure produced by transfusing stored blood. Clinical trial registered with www.clinicaltrials.gov (NCT 01529502).

Towards microfluidic-based depletion of stiff and fragile human red cells that accumulate during blood storage

In this study, the effects of prolonged storage on several biophysical properties of red blood cells (RBCs) were investigated. Single cell deformability was used as an important criterion in determining subgroups of RBCs evolved during storage lesion. A deformability-based microfluidic cell sorting technology was applied, which demonstrates the ability to enrich and separate the less deformable subpopulations of stored blood. These less deformable RBC subpopulations were then associated with other important markers such as osmotic fragility indicating cell integrity as well as microparticle content. This work demonstrates a systematic methodology to both monitor and improve banked blood quality, thereby reducing risks related to blood transfusion.

Alterations of the arginine metabolome in sickle cell disease: a growing rationale for arginine therapy

Low global arginine bioavailability (GAB) is associated with numerous complications of SCD including early mortality. Mechanisms of arginine dysregulation involve a complex paradigm of excess activity of the arginine-consuming enzyme arginase, elevated levels of asymmetric dimethylarginine, altered intracellular arginine transport, and nitric oxide synthase dysfunction. Restoration of GAB through exogenous supplementation is therefore, a promising therapeutic target. Studies of arginine therapy demonstrate efficacy in treating patients with leg ulcers, pulmonary hypertension risk, and pain. Co-administration with hydroxyurea increases levels of nitrite and fetal hemoglobin. Addressing the alterations in the arginine metabolome may result in new strategies for treatment of SCD.

Dose-Dependent Hemodynamic, Biochemical, and Tissue Oxygen Effects of OC99 following Severe Oxygen Debt Produced by Hemorrhagic Shock in Dogs

We determined the dose-dependent effects of OC99, a novel, stabilized hemoglobin-based oxygen-carrier, on hemodynamics, systemic and pulmonary artery pressures, surrogates of tissue oxygen debt (arterial lactate 7.2 ± 0.1 mM/L and arterial base excess -17.9 ± 0.5 mM/L), and tissue oxygen tension (tPO2) in a dog model of controlled severe oxygen-debt from hemorrhagic shock. The dose/rate for OC99 was established from a pilot study conducted in six bled dogs. Subsequently twenty-four dogs were randomly assigned to one of four groups (n = 6 per group) and administered: 0.0, 0.065, 0.325, or 0.65 g/kg of OC99 combined with 10 mL/kg lactated Ringers solution administered in conjunction with 20 mL/kg Hextend IV over 60 minutes. The administration of 0.325 g/kg and 0.65 g/kg OC99 produced plasma hemoglobin concentrations of 0.63 ± 0.01 and 1.11 ± 0.02 g/dL, respectively, improved systemic hemodynamics, enhanced tPO2, and restored lactate and base excess values compared to 0.0 and 0.065 g/kg OC99. The administration of 0.65 g/kg OC99 significantly elevated pulmonary artery pressure. Plasma hemoglobin concentrations of OC99 ranging from 0.3 to 1.1 g/dL, in conjunction with colloid based fluid resuscitation, normalized clinical surrogates of tissue oxygen debt, improved tPO2, and avoided clinically relevant increases in pulmonary artery pressure.