Alteration of red cell aggregability and shape during blood storage

A single assay for multiple storage-sensitive red blood cell characteristics by means of infrared spectroscopy

BACKGROUND

To maintain a high quality of red blood cells (RBCs), RBC characteristics must be followed during storage under blood bank conditions. By means of infrared (IR) spectroscopy, several characteristics can be measured simultaneously.

STUDY DESIGN AND METHODS

IR spectra were acquired for samples from RBCs that were collected and stored according to Dutch blood bank procedures for a period of up to 50 days. Spectra of the soluble cell components were acquired separately after hypotonic lysis of the cells, followed by centrifugation. Characteristic vibrational bands were analyzed with respect to storage time-dependent changes in peak position and in intensity.

RESULTS

A decrease in corresponding peak intensities indicates that RBCs lose protein and lipid during storage. Changes in protein secondary structure during storage are largely confined to integral membrane proteins and membrane-associated proteins. A concurrent decrease in lipid packing density probably reflects the gradual change in cellular shape from discoidal to globular. By integration over a narrow range, storage-dependent changes in intracellular adenosine triphosphate (ATP) and glucose levels could be estimated. ATP levels decrease during storage, but stay above the required 75% of the initial level after 35 days of storage. Glucose concentrations stay well above 5 mmol/L over the entire storage period.

CONCLUSION

IR spectroscopy is a promising technique to follow structural and metabolic changes in RBCs during storage under blood bank conditions. Several variables can be determined rapidly in a single measurement.

Transfusion of aged packed red blood cells results in decreased tissue oxygenation in critically injured trauma patients

BACKGROUND

Blood transfusion is a common event in the treatment of injured patients. The effect of red blood cell transfusion on tissue oxygenation is unclear. The transfusion of older blood has been shown to be detrimental in retrospective studies. This study aims to study the effect of the age of the blood transfused on the tissue oxygenation using near infrared spectroscopy.

METHODS

Thirty-two critically injured trauma patients for whom a blood transfusion had been ordered were recruited. Each patient had a transcutaneous probe placed on the thenar eminence. The probe was placed 1 hour before the transfusion and left in place until 4 hours after transfusion. Tissue oxygen saturation (Sto2) was recorded every 2 minutes. The Sto2 area under the curve (AUC) over time periods was calculated. A control group (n = 16), not transfused, was recruited. The transfusion group was divided into two groups by blood age. One group received blood less than 21 days old, (new blood, n = 15) and the other received blood 21 days old or greater (old blood, n = 17). The data were analyzed for significance with Kendall's W and Wilcoxon's signed rank test (p < 0.05).

RESULTS

Baseline characteristics such were not significantly different between groups. The baseline AUC did not differ between groups. The old blood group demonstrated a significant decline in Sto2 comparing its baseline period to its transfusion period (p < 0.05). There was no similar decline in the control group or the new blood group. The posttransfusion period AUC for the old blood group was also lower versus baseline (p = 0.06). There was a moderate correlation between increasing age of blood and decrease in oxygenation (r = 0.5).

CONCLUSIONS

There was a decrease in peripheral tissue oxygenation in patients receiving older red blood cells. There was no oxygenation decrease in patients receiving blood less than 21 days. This indicates that factors in stored blood may influence the peripheral vasculature and oxygen delivery.

Transfusion of stored red blood cells adhere in the rat microvasculature

BACKGROUND

Ex vivo storage of red blood cells (RBCS) for transfusions is associated with a "storage lesion," which decreases RBC deformability and increases RBC adhesiveness to vascular endothelium. This may impair microcirculatory flow with deleterious effects on oxygen delivery after transfusion. Previous studies have shown that human RBCs adhere to endothelial monolayers in vitro with prolonged storage and is reduced by prestorage leukoreduction (LR). The objective of this study was to determine whether duration of RBC storage and LR influence RBC adhesion in vivo in capillaries.

STUDY DESIGN AND METHODS

Rat RBCs were collected and stored in CPDA-1 under standard blood bank conditions. Three RBC products were compared: 1) fresh RBCs, less than 24 hours of storage (n = 6); 2) non leukoreduced (NLR) RBCs stored for 7 days (n = 6); and 3) prestorage LR RBCs stored for 7 days (n = 6). RBCs were labeled with fluorescein isothiocyanate (FITC) 24 hours before transfusion and reinjected in an isovolemic manner into healthy rats. The FITC-labeled RBCs were visualized in the extensor digitorum longus muscle using intravital video microscopy (20 x magnification). The number of RBCs adherent in capillaries was counted 1 hour after transfusion in 10 random fields and the median values were compared with one-way analysis of variance.

RESULTS

Stored RBCs showed increased levels of adherence in capillaries compared to their fresh counterparts (p < 0.05). Prestorage LR decreased RBC adherence to levels equivalent to those of fresh RBCs (p < 0.05 for stored LR vs. stored NLR).

CONCLUSION

Rat RBCs stored under conditions that closely mimicked clinical transfusion adhere in capillaries. The decreased RBC adherence with LR suggest a direct effect of white blood cells or their byproducts on RBC deformability and/or adhesiveness to microvascular endothelium. Further study will examine the mechanism of adherence and the impact it has on microcirculatory flow and oxygen delivery in the critically ill host.

The association of perioperative red blood cell transfusions and decreased long-term survival after cardiac surgery

BACKGROUND

Exposure to red blood cell (RBC) transfusions has been associated with increased mortality after cardiac surgery. We examined long-term survival for cardiac surgical patients who received one or two RBC units during index hospitalization.

METHODS

Nine thousand seventy-nine consecutive patients undergoing coronary artery bypass graft, valve, or coronary artery bypass graft/valve surgery at eight centers in northern New England during 2001-2004 were examined after exclusions. A probabilistic match between the regional registry and the Social Security Administration's Death Master File determined mortality through June 30, 2006. Cox Proportional Hazard and propensity methods were used to calculate adjusted hazard ratios.

RESULTS

Thirty-six percent of patients (n = 3254) were exposed to one or two RBC units. Forty-three percent of RBCs were given intraoperatively, 56% in the postoperative period and 1% were preoperative. Patients transfused were more likely to be anemic, older, smaller, female and with more comorbid illness. Survival was significantly decreased for all patients exposed to 1 or 2 U of RBCs during hospitalization for cardiac surgery compared with those who received none (P < 0.001). After adjustment for patient and disease characteristics, patients exposed to 1 or 2 U of RBCs had a 16% higher long-term mortality risk (adjusted hazard ratios = 1.16, 95% CI: 1.01-1.34, P = 0.035).

CONCLUSIONS

Exposure to 1 or 2 U of RBCs was associated with a 16% increased hazard of decreased survival after cardiac surgery.

Noninfectious serious hazards of transfusion

As infectious complications from blood transfusion have decreased because of improved donor questionnaires and sophisticated infectious disease blood screening, noninfectious serious hazards of transfusion (NISHOTs) have emerged as the most common complications of transfusion. The category of NISHOTs is very broad, including everything from well-described and categorized transfusion reactions (hemolytic, febrile, septic, and allergic/urticarial/anaphylactic) to lesser known complications. These include mistransfusion, transfusion-related acute lung injury, transfusion-associated circulatory overload, posttransfusion purpura, transfusion-associated graft versus host disease, microchimerism, transfusion-related immunomodulation, alloimmunization, metabolic derangements, coagulopathic complications of massive transfusion, complications from red cell storage lesions, complications from over or undertransfusion, and iron overload. In recent years, NISHOTs have attracted more attention than ever before, both in the lay press and in the scientific community. As the list of potential complications from blood transfusion grows, investigators have focused on the morbidity and mortality of liberal versus restrictive red blood cell transfusion, as well as the potential dangers of transfusing "older" versus "younger" blood. In this article, we review NISHOTs, focusing on the most recent concerns and literature.

Loss of red cell chemokine scavenging promotes transfusion-related lung inflammation

Red cell transfusions are associated with the development of acute lung injury in the critically ill. Recent evidence suggests that storage induced alterations of the red blood cell (RBC) collectively termed the "storage lesion" may be linked with adverse biologic consequences. Using a 2-event model of systemic endotoxemia followed by a secondary challenge of RBC transfusion, we investigated whether purified RBC concentrates from syngeneic C57BL/6 mice altered inflammatory responses in murine lungs. Transfusion of RBCs stored for 10 days increased neutrophil counts, macrophage inflammatory protein-2 (MIP-2) and chemokine (KC) concentrations in the airspaces, and lung microvascular permeability compared with transfusion of less than 1-day-old RBCs. Because RBCs have been shown to scavenge inflammatory chemokines through the blood group Duffy antigen, we investigated the expression and function of Duffy during storage. In banked human RBCs, both Duffy expression and chemokine scavenging function were reduced with increasing duration of storage. Transfusion of Duffy knockout RBCs into Duffy wild-type endotoxemic mice increased airspace neutrophils, inflammatory cytokine concentrations, and lung microvascular permeability compared with transfusion of Duffy wild-type RBCs. Thus, reduction in erythrocyte chemokine scavenging is one functional consequence of the storage lesion by which RBC transfusion can augment existing lung inflammation.

Risks associated with fresh whole blood and red blood cell transfusions in a combat support hospital

OBJECTIVE

Fresh whole blood (FWB) and red blood cells (RBCs) are transfused to injured casualties in combat support hospitals. We evaluated the risks of FWB and RBCs transfused to combat-related casualties.

DESIGN

Retrospective chart review.

SETTING

Deployed U.S. Army combat support hospitals.

SUBJECTS

Donors of FWB and recipients of FWB and RBCs.

MEASUREMENTS AND RESULTS

The storage age of RBCs at transfusion was measured as an indicator of overall risk associated with the storage lesion of RBCs between January 2004 and December 2004 at one combat support hospital. Between April 2004 and December 2004, FWB was prescreened only at one combat support hospital for human immunodeficiency virus, hepatitis C virus, and hepatitis B surface antigen before transfusion. To estimate the general incidence of infectious agent contamination in FWB units, samples collected between May 2003 and February 2006 were tested retrospectively for human immunodeficiency virus, hepatitis B surface antigen, hepatitis C virus, and human lymphotropic virus. Results were compared between FWB samples prescreened and not prescreened for infectious agents before transfusion. At one combat support hospital in 2004, 87 patients were transfused 545 units of FWB and 685 patients were transfused 5,294 units of RBCs with a mean age at transfusion of 33 days (+/- 6 days). Retrospective testing of 2,831 samples from FWB donor units transfused in Iraq and Afghanistan between May 2003 and February 2006 indicated that three of 2,831 (0.11%) were positive for hepatitis C virus recombinant immunoblot assay, two of 2,831 (0.07%) were positive for human lymphotropic virus enzyme immunoassay, and none of 2,831 were positive for both human immunodeficiency virus 1/2 and hepatitis B surface antigen by Western blot and neutralization methods, respectively. The differences in the incidence of hepatitis C virus contamination of FWB donor units between those prescreened for hepatitis C virus (zero of 406; 0%) and not prescreened (three of 2,425; 0.12%) were not significant (p = .48).

CONCLUSIONS

The risk of infectious disease transmission with FWB transfusion can be minimized by rapid screening tests before transfusion. Because of the potential adverse outcomes of transfusing RBCs of increased storage age to combat-related trauma patients, the risks and benefits of FWB transfusions must be balanced with those of transfusing old RBCs in patients with life-threatening traumatic injuries.

Increased mortality, postoperative morbidity, and cost after red blood cell transfusion in patients having cardiac surgery

BACKGROUND

Red blood cell transfusion can both benefit and harm. To inform decisions about transfusion, we aimed to quantify associations of transfusion with clinical outcomes and cost in patients having cardiac surgery.

METHODS AND RESULTS

Clinical, hematology, and blood transfusion databases were linked with the UK population register. Additional hematocrit information was obtained from intensive care unit charts. Composite infection (respiratory or wound infection or septicemia) and ischemic outcomes (myocardial infarction, stroke, renal impairment, or failure) were prespecified as coprimary end points. Secondary outcomes were resource use, cost, and survival. Associations were estimated by regression modeling with adjustment for potential confounding. All adult patients having cardiac surgery between April 1, 1996, and December 31, 2003, with key exposure and outcome data were included (98%). Adjusted odds ratios for composite infection (737 of 8516) and ischemic outcomes (832 of 8518) for transfused versus nontransfused patients were 3.38 (95% confidence interval [CI], 2.60 to 4.40) and 3.35 (95% CI, 2.68 to 4.35), respectively. Transfusion was associated with increased relative cost of admission (any transfusion, 1.42 times [95% CI, 1.37 to 1.46], varying from 1.11 for 1 U to 3.35 for >9 U). At any time after their operations, transfused patients were less likely to have been discharged from hospital (hazard ratio [HR], 0.63; 95% CI, 0.60 to 0.67) and were more likely to have died (0 to 30 days: HR, 6.69; 95% CI, 3.66 to 15.1; 31 days to 1 year: HR, 2.59; 95% CI, 1.68 to 4.17; >1 year: HR, 1.32; 95% CI, 1.08 to 1.64).

CONCLUSIONS

Red blood cell transfusion in patients having cardiac surgery is strongly associated with both infection and ischemic postoperative morbidity, hospital stay, increased early and late mortality, and hospital costs.

Blood banking-induced alteration of red blood cell flow properties

BACKGROUND

Blood banking procedures are associated with damage to red blood cell (RBC) membranes, which can impair their flow properties, namely, their deformability, aggregability, and adherence to endothelial cells (ECs) and thus possibly introducing a circulatory risk to recipients. This study was undertaken to comprehensively explore the effect of cold storage and gamma irradiation on RBC flow properties.

STUDY DESIGN AND METHODS

RBC flow properties were monitored as a function of shear stress with a computerized cell flow properties analyzer. Because we had previously studied storage effect on RBC aggregability (Transfusion 1999;39:277-81), here we determined the storage effect on RBC adherence and deformability, by measuring them before (control) and during storage. Gamma irradiation effect on RBC aggregability, adherence, and deformability was determined before (control) and after irradiation.

RESULTS

Cold storage significantly elevated the number of adherent RBCs and the strength of their interaction with ECs, and was marked by decreased RBC deformability as early as 2 weeks into the storage period. The elevation of RBC-EC interaction was well correlated with translocation of phosphatidylserine to the RBC surface. Gamma irradiation induced an immediate and marked increase in the number of rigid cells, but did not affect RBC adherence and aggregability.

CONCLUSION

RBC flow properties appear to be especially sensitive to cold storage and gamma irradiation because they are impaired long before the expiration date. Because impaired RBC flow properties facilitate circulatory disorders, the potential circulatory risk of transfusion RBC with blood banking-impaired rheology should be considered.

Blood tranfusion in critically ill patients: state of the art

Anemia is one of the most common abnormal findings in critically ill patients, and many of these patients will receive a blood transfusion during their intensive care unit stay. However, the determinants of exactly which patients do receive transfusions remains to be defined and have been the subject of considerable debate in recent years. Concerns and doubts have emerged regarding the benefits and safety of blood transfusion, in part due to the lack of evidence of better outcomes resulting from randomized studies and in part related to the observations that transfusion may increase the risk of infection. As a result of these concerns and of several studies suggesting better or similar outcomes with a lower transfusion trigger, there has been a general tendency to decrease the transfusion threshold from the classic 10 g/dL to lower values. In this review, we focus on some of the key studies providing insight into current transfusion practices and fueling the current debate on the ideal transfusion trigger.

Storage-dependent remodeling of the red blood cell membrane is associated with increased immunoglobulin G binding, lipid raft rearrangement, and caspase activation

BACKGROUND

The elucidation of the storage lesion is important for the improvement of red blood cell (RBC) storage. Ex vivo storage is also a model system for studying cell-signaling events in the senescence and programmed cell death of RBCs. The membrane hosts critical steps in these mechanisms and undergoes widespread remodeling over the storage period.

STUDY DESIGN AND METHODS

Fresh and CPDA-stored RBCs from 21 blood donors were evaluated as whole cells, membrane ghosts, and cytoskeletons by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, immunoblotting, immunofluorescence microscopy, and in situ assays. Band 3 content, immunoglobulin G (IgG) content, specific protein movement to and from the membrane, and caspase system activation were measured.

RESULTS

During storage, Band 3 protein was aggregated and its content decreased as did the content of several lipid raft-related proteins. IgG binding to the membrane increased. Sorcin and synexin moved from the cytosol to the membrane, stomatin and flotillins left the membrane, the Fas protein was oligomerized, and caspase was activated.

CONCLUSION

The remodeling of the RBC membrane during storage includes loss and oxidative cross-linking of Band 3 as well as IgG binding. This process occurs with lipid raft development and loss and is probably driven by caspase activation. Oxidative injury appears to be an important driver of RBC aging during storage.

An economic analysis of costs associated with development of a cell salvage program

BACKGROUND

The increasing cost of blood products and associated risks of transfusion have lead to a heightened interest in techniques which reduce or replace allogeneic blood transfusion. The use of cell salvage is being explored in a number of institutions. We present financial information which may be useful to institutions that are considering the addition of a cell salvage service.

METHODS

A review of the cell salvage data from 2328 patients was used to estimate the average cost of a packed red blood cell unit equivalent processed by cell salvage equipment. In addition, an analysis was performed to assess the break-even point of establishing a cell salvage service.

RESULTS

Initial capital outlay to establish a cell salvage service at this institution was $103,551. The annual fixed operating cost was $250,943. The average cost of transfusion of an allogeneic packed red blood cell unit was $200. For an equivalent cell salvage unit, the cost was $89.46. The payback period was 1.9 mo.

CONCLUSION

This analysis suggests that cell salvage can be significantly less expensive than allogeneic blood. The cost of cell salvage in other institutions will vary depending upon case volume, expected levels of blood loss per case, and initial investment costs. A step-by-step formula is provided to assist in the evaluation of a cell salvage service in hospitals of various sizes.

Washing of stored red blood cells by an autotransfusion device before transfusion

BACKGROUND AND OBJECTIVES

The use of an autotransfusion device to wash blood of the incision site is increasing. After washing, this blood is retransfused without side effects caused by activated plasma factors and cell release products. This procedure could be extended to washing of donor blood, which may be particularly useful for red blood cells (RBCs) stored for more than 4 weeks that contain high concentrations of free haemoglobin, potassium, lactate and other metabolites. It is not known whether stored RBCs can withstand the cell washing procedure with the use of an autotransfusion device, while keeping their primary functions intact. The objective of this study was to determine the quality of RBCs, after cell washing in comparison to untreated RBCs.

MATERIALS AND METHODS

RBCs were studied in terms of integrity (free haemoglobin), stored energy (2,3-diphosphoglycerate, adenosine triphosphate), metabolites (lactate, potassium) and physical characteristics (osmotic resistance, aggregability, deformability).

RESULTS

After washing, free lactate and potassium were significantly reduced as compared to the levels before washing. The osmotic resistance of RBCs slightly improved, whereas aggregation capacity reduced after washing. Fifteen per cent of haemoglobin was lost during washing. The deformability and free haemoglobin levels remained unchanged.

CONCLUSION

Washing stored blood before transfusion may be of benefit, because the waste products are effectively removed from the stored RBC.

Red cell transfusions and guidelines: a work in progress

Blood transfusion utilization continues to rise, yet it has never undergone prospective safety and efficacy testing. Recent data regarding oxygen delivery, microcirculation, and inflammation all point toward potential problems with allogeneic transfusion. Outcome data from retrospective data bases are sobering, calling to question the present practices of red cell transfusion.

The mechanism of the dextran-induced red blood cell aggregation

In order to clarify the mechanism of dextran-induced aggregation, the effect of the ionic strength (I) on the minimal shear stress (tau(c)) required to rupture RBC doublets was studied for suspensions with the external media containing 76 and 298 kDa dextrans. At low and high ionic strengths, tau(c) increases with increasing I, whereas at intermediate I values, tau(c) versus I dependencies reveal a plateau step. The non-monotonous shape of these curves disagrees with the depletion model of RBC aggregation and is consistent with the predictions of the bridging mechanism. Literature reports point out that elastic behavior of dextran molecules in low and high I regions is fairly typical of Hookean springs and hence predict an increase in tau(c) with increasing I. A plateau step is accounted for by the enthalpic component of the dextran elasticity due to the shear-induced chair-boat transition of the dextran's glucopyranose rings. A longer plateau step for suspensions with a higher molecular weight dextran is explained by a larger contribution of the enthalpic component to the dextran elasticity. Thus, the results reported in this study provide evidence that RBC aggregation is caused by the formation of dextran bridges between the cells.

MICROVASCULAR PERSPECTIVE OF OXYGEN-CARRYING AND -NONCARRYING BLOOD SUBSTITUTES

The development of an alternative to natural blood has evolved from the initial goal of replicating blood properties to the current objective of formulating a fluid that can be used to replace blood while preserving microvascular function and delivering oxygen. The properties of this fluid are counterintuitive and different from blood because it has high viscosity, oxygen affinity, and a low oxygen carrier concentration when compared with blood. The optimal oxygen carrier devised presently is poly-ethylene-conjugated human hemoglobin, a material demonstrated to be vasoinactive and void of the toxicities present in previous hemoglobin formulations. A feature of this material is that it is effective in small quantities, and therefore amplifies the equivalent supply of blood derived from blood donations.

Cardiovascular collapse due to massive pulmonary thromboembolism during orthotopic liver transplantation

Severe pulmonary thromboembolism has been occasionally reported during orthotopic liver transplantation, with fatal outcomes occurring in about 50% of cases because of low cardiac output and multiple organ failure. Perioperative alterations in coagulation, insertion of pulmonary artery and other invasive catheters, administration of antifibrinolytic agents, and repeated ischemic insults may all promote the formation of intravascular/cardiac blood clots. We present a case of intraoperative right ventricular failure associated with the presence of a large thrombus wrapped around the pulmonary artery catheter. Identification of risk factors for intraoperative pulmonary thromboembolism warrants a prophylactic medical approach including selective blood component therapy and administration of antifibrinolytics guided by bedside coagulation tests as well as noninvasive hemodynamic monitoring.

Does Insulin-Like Growth Factor 1 Contribute in Red Blood Cell Transfusions to the Pathogenesis of Retinopathy of Prematurity during Retinal Neovascularization?

BACKGROUND

Red blood cell (RBC) transfusions are associated with the development of retinopathy of prematurity (ROP). During the period of retinal neovascularization a rise of insulin-like growth factor 1 (IGF-1) may trigger rapid growth of new blood vessels.

OBJECTIVES

To study endocrine factors in RBC transfusions that might be of importance for ROP.

METHODS

IGF-1, IGF-2 and their binding proteins 1-3 (IGFBP-1-3) were determined by radioimmunoassays in 7 very-low-birthweight (VLBW) infants with ROP >or= stage 2 receiving a RBC transfusion, in 10 controls (VLBW infants with ROP <or= stage 1, no transfusion), in supernatants of 7 RBCs and of 5 washed RBCs (WRBC).

RESULTS

IGF-1 (mean +/- SD) in infants with ROP was 20.0 +/- 4.2 microg/l, in controls 35.9 +/- 15.2 microg/l (Mann-Whitney U test, p = 0.030). IGF-1 in RBC was 12.88 +/- 5.03 microg/l and in WRBC 0.45 +/- 0.74 microg/l (average of the three-course washing procedure). IGF-2 in infants with ROP was 485.67 +/- 158.73 microg/l, in controls 389.9 +/- 102.8 microg/l (not significant), in RBC 109.50 +/- 117.89 microg/l, in WRBC 61.07 +/- 30.0 microg/l. Except for IGFBP-3 other IGFBPs were barely or not detectable in RBC or WRBC.

CONCLUSIONS

Considering lower IGF-1 concentrations in preterm infants than in adults (factor 20), the IGF-1 in RBC transfusions is equivalent to a single dose of 1 microg/kg IGF-1 (5-10% of the adult dose with proved metabolic responses). Endocrinological relationships between the donor's load and the acceptor's individual features are a new aspect of potential side effects of RBC transfusions. Further research is necessary to clarify the share of the described IGF administration on the development of ROP.

Inflammatory cytokine inhibition of erythropoiesis in patients implanted with a mechanical circulatory assist device

Mechanical circulatory assist devices (MCADs) are increasingly utilized independently of cardiac transplantation in the management of heart failure. Though MCAD use incorporates inherent mechanical risks, the inevitable onset of chronic anemia, with its associated morbidity and mortality, is also a significant concern. MCAD support has been correlated with elevated plasma levels of inflammatory cytokines TNF-alpha, IL-1beta, and IL-6, which have separately been found to inhibit erythropoietin (Epo)-induced erythrocyte (RBC) maturation. Previous analysis of hematological parameters for MCAD-supported patients concluded that an amplified inflammatory response impedes RBC proliferation and recovery from hemolytic anemia. Additional analysis may bolster this assertion. Hemoglobin concentration (HC), RBC distribution width (RDW), mean cell volume (MCV), and cardiac index were retrospectively analysed for 78 MCAD-supported patients implanted for greater than 30 days at the University of Arizona Health Sciences Center from 1996 to 2002. Analysis confirms that the HC, a conventional marker for anemia, declines with MCAD placement and remains below the clinically defined, minimum normal value. Inversely, the RDW rises above maximum normal measure, signifying an increased fraction of juvenile RBCs. The MCV remains unchanged and within normal limits, demonstrating adequate substrate for RBC formation. MCAD performance also stabilizes as adequate perfusion returns. These results further support our previously published conclusion that a sufficient response of erythropoiesis occurs in reaction to the onset of anemia by an increased production of immature RBCs. However, the cells never fully mature and join circulation. The patient's inflammatory cytokine response to the implanted device most likely mediates the chronic MCAD-induced anemia by inhibition of Epo effects.

Pentoxifylline attenuates the increase in whole blood viscosity after transfusion

BACKGROUND

Pentoxifylline improves tissue oxygenation and intestinal blood flow in models of haemorrhagic shock, and it has been used for the treatment of intermittent claudication due to its beneficial effects on haemorheology. We investigated the effects of pentoxifylline on whole blood viscosity during packed red-blood cell transfusion in critically ill adult patients.

METHODS

Twenty critically ill patients were randomly assigned to one of two groups (pentoxifylline group: n = 11, placebo group: n = 9) and prospectively studied. Forty-five minutes before and during the packed red-blood cell transfusion (10 ml min(-1)) over a period of 80 min, 1.5 mg kg(-1) . h(-1) pentoxifylline or placebo were administered intravenously. Haematocrit, plasma fibrinogen concentration, total protein concentration, whole blood viscosity (at a shear rate of 10 s(-1), 50 s(-1), and 100 s(-1)) and plasma viscosity were measured.

RESULTS

After the packed red-blood cell transfusion, haematocrit levels increased significantly in both groups (pentoxifylline group: from 26.1 +/- 2.8% to 33.0 +/- 3.2; placebo group: from 24.4 +/- 3.3% to 32.6 +/- 2.6%; means +/- standard deviation). Compared to baseline, whole blood viscosity increased in both groups at all shear rates after the transfusion, but the increase was significantly less in the pentoxifylline group (26 +/- 15% vs. 49 +/- 14%, 23 +/- 11% vs. 39 +/- 12%, and 22 +/- 11% vs. 35 +/- 12% for the pentoxifylline vs. placebo groups at shear rates of 10 s(-1), 50 s(-1), and 100 s(-1), respectively). Plasma viscosity, total protein concentration, and fibrinogen concentration remained unchanged and no significant differences among groups were observed.

CONCLUSIONS

These results suggest that pentoxifylline is effective in attenuating the increase in whole blood viscosity after a transfusion of packed red-blood cells. Plasma viscosity is not influenced by pentoxifylline.

Microvascular perfusion upon exchange transfusion with stored red blood cells in normovolemic anemic conditions

BACKGROUND

Transfusions are intended to augment oxygen-carrying capacity. The ability of fresh and stored red blood cells (RBCs) to maintain microvascular perfusion and oxygen delivery to the tissue has not been directly measured.

STUDY DESIGN AND METHODS

Microvascular responses to exchange transfusion with fresh and stored RBCs after acute isovolemic hemodilution with a plasma expander were investigated with the hamster window chamber model. In-vivo functional capillary density (FCD), blood flow, and high-resolution oxygen distribution in microvascular networks were measured by noninvasive methods.

RESULTS

Exchange transfusion with an RBC suspension after a 60 percent isovolemic hemodilution with dextran 70 (6% MW = 70 kDa) resulted in a hematocrit of 18 percent (5.6 +/- 0.2 g/dL hemoglobin [Hb]). All other systemic variables were unchanged. Stored RBCs (28 days in citrate-phosphate-dextrose-adenine-1) resuspended in fresh frozen plasma matched to the Hct and Hb concentration were exchange transfused until 25 percent of the circulating RBCs were stored RBCs. Stored RBCs reduced microvascular flow and FCD by 63 and 54 percent, respectively, of the level achieved when fresh RBCs were exchange transfused. Microvascular oxygen extraction by the stored RBC was 54 percent lower than that of the fresh RBCs. The tissue oxygen levels were 3.5 and 14.4 mmHg for the stored and fresh RBCs, respectively.

CONCLUSION

Circulation of stored RBCs in a hemodiluted animal resulted in significantly malperfused and underoxygenated microvasculature that was not detectable at the systemic level.

Efficacy of red blood cell transfusion in the critically ill

This article has evaluated the published data regarding the efficacy of RBC transfusions in the critically ill. Taken together, these studies generally support conservative RBC transfusion strategies in critical care to reduce the risk of transfusion-related adverse effects. The TRICC trial has established the safety ofa restrictive transfusion strategy, suggesting that physicians could minimize exposure to allogeneic RBCs by lowering their transfusion threshold. Further research will add to the generalizability of this study and explore the possible mechanism to explain why RBC transfusions do not improve outcomes in the critically ill. Additional studies will be necessary to determine the effects of RBC storage time and the presence of allogeneic leukocytes in allogeneic RBC. The following conclusions are evident: 1. RBC transfusion does not improve tissue oxygen consumption consistently in critically ill patients, either globally or at the level of the micro-circulation. 2. RBC transfusion is not associated with improvements in clinical outcome in the critically ill and may result in worse outcomes in some patients. 3. Specific factors that identify patients who will improve from RBC transfusion are difficult to identify. 4. Lack of efficacy of RBC transfusion likely is related to storage time, increased endothelial adherence of stored RBCs, nitric oxide binding by free hemoglobin in stored blood, donor leukocytes, host inflammatory response, and reduced red cell deformability.

Managing Anemia in the Critically Ill Patient

Anemia of critical illness is a multifactorial condition caused by phlebotomy, ongoing blood loss, and inadequate production of red blood cells. It occurs early in the course of critical illness. Although red blood cell transfusion is the treatment of choice for immediate management of anemia in the intensive care unit, controversy surrounds the most appropriate hemoglobin concentration or hematocrit "trigger." Therapeutic options, including blood-conservation tools, minimization of phlebotomy, erythropoietic agents, and investigational oxygen-carrying agents, may be alternatives to red blood cell transfusions in critically ill patients with anemia. Patient selection for erythropoietic agents will depend on further work dealing with outcomes and the total cost of care in managing the anemia of critical illness.

Effects of storage on efficacy of red cell transfusion: When is it not safe?

OBJECTIVE

To review the literature on red blood cell storage and its relationship to the efficacy of transfusion.

RESULTS

Well-documented changes occur to the red blood cell product during ex vivo storage. These changes include a reduction in red blood cell deformability, altered red blood cell adhesiveness and aggregability, and a reduction in 2,3-diphosphoglycerate and ATP. Bioactive compounds with proinflammatory effects also accumulate in the storage medium. These changes reduce posttransfusion viability of red blood cells. The clinical effects beyond posttransfusion viability are uncertain, but a growing body of evidence suggests that the storage lesion may reduce tissue oxygen availability, have proinflammatory and immunomodulatory effects, and influence morbidity and mortality. There are no published randomized, control trials examining the effect of storage duration on morbidity and mortality. Leukoreduction improves the quality of stored red blood cell products and in some studies has been shown to reduce morbidity and mortality.

CONCLUSION

Although storage duration influences the quality of red blood cell product, there is currently insufficient evidence to advocate shorter storage periods for red blood cell products.

Automated collection of blood components: their storage and transfusion

The performance of an automated device, the Gambro TRIMA, was evaluated for component production, and an in vivo assessment of the platelets was carried out. Red cell concentrates (RCCs), platelets and plasma were collected and stored according to standard blood bank procedures and evaluated for quality by in vitro measurements. Additionally, single-donor platelets (n=10) were transfused to thrombocytopenic patients after 5 days of storage. Platelet counts were measured after 1 h and the corrected count increment (CCI) was calculated. No significant changes were seen before or after procedure in donor haemoglobin, haematocrit, coagulation factors or platelet count. Return-line samples showed no increase in the level of plasma haemoglobin. Plasma haemoglobin and potassium increased following RBC storage, but there was no change in the red cell number. Platelet aggregation decreased from 52 to 11% (adenosine diphosphate) and the Kunicki morphology score dropped from 379 to 174. Little change was seen in the hypotonic shock response (69-63%) or in the percentage of CD62 expression (4.8-19.8) over time. The CCI averaged 28+/-26 x 10(3) microL(-1) in 10 patients 1 h after transfusion. The TRIMA machine collects RCCs, platelets and plasma in a variety of combinations in one session. For autologous collection, two units of RCC plus platelets can be collected at one time, reducing administrative and testing costs. The platelets have good in vivo recovery, as shown by the CCI values. An added advantage is that the TRIMA machine can be used in hospitals to generate components in times of shortage without the need for a component's laboratory.

Depletion-mediated red blood cell aggregation in polymer solutions

Polymer-induced red blood cell (RBC) aggregation is of current basic science and clinical interest, and a depletion-mediated model for this phenomenon has been suggested; to date, however, analytical approaches to this model are lacking. An approach is thus described for calculating the interaction energy between RBC in polymer solutions. The model combines electrostatic repulsion due to RBC surface charge with osmotic attractive forces due to polymer depletion near the RBC surface. The effects of polymer concentration and polymer physicochemical properties on depletion layer thickness and on polymer penetration into the RBC glycocalyx are considered for 40 to 500 kDa dextran and for 18 to 35 kDa poly (ethylene glycol). The calculated results are in excellent agreement with literature data for cell-cell affinities and with RBC aggregation-polymer concentration relations. These findings thus lend strong support to depletion interactions as the basis for polymer-induced RBC aggregation and suggest the usefulness of this approach for exploring interactions between macromolecules and the RBC glycocalyx.

Influence of storage on red blood cell rheological properties

BACKGROUND

It is known that the age of transfused blood is a risk factor for the development of multiple organ failure in surgical patients. However, the character of hemorrheological changes in stored blood as well as the time when they appear remains disputable. We assumed that blood storage was accompanied by a progressive decrease of RBC deformability and rheological disorders. The degree of rheological disturbances should be directly proportional to the number of RBC with altered geometry.

MATERIALS AND METHODS

Nine packages of RBC kept in adenine saline solution were examined from the 5th to the 42nd day of storage. RBC deformability index (DI) was determined by micropore filtration technique. RBC shape was estimated by means of scanning electron microscopy. Blood clotting time was measured by Sonoclot coagulation analyzer.

RESULTS

Significant alterations of RBC shape started at the second week of storage and progressed during the rest of the storage period. RBC shape changes were accompanied by progressive decrease in DI and increase in hemolysis and acidosis. The correlation index between the percentage of abnormally shaped RBC and DI was -0.81 (P = 0.0258). Blood clotting progressively decreased after 2 weeks of storage, probably due to the exhaustion of some procoagulant plasma factors.

CONCLUSIONS

Serious hemorrheological disorders, including the decrease in RBC deformability secondary to shape abnormalities, acidosis, and the decrease of blood clotting, start already at the second week of storage and progress up to the end of the storage period. Transfusion of packed RBC older than 7 days may contribute to hemorrheological disorders in critically ill patients.