Characterization of reactions after exclusive transfusion of white cell-reduced cellular blood components

Results of a randomised controlled trial between an ORC collagen hemostatic agent and a carrier-bound fibrin sealant

INTRODUCTION

Despite ongoing optimisation of surgical techniques, hemostasis continues to be a fundamental challenge in many operations today. This randomised controlled trial compared the efficacy of a new hemostatic agent made of oxidised regenerated cellulose and collagen (ORC-Coll) with that of a conventional carrier-bound fibrin sealant (CBFS).

METHODS

Hemostasis was investigated representatively in the case of post-thyroidectomy bleeding from the resection surface. To demonstrate that ORC-Coll (mediCipio® A) has at least the same hemostatic efficacy as CBFS (Tachosil®), the volume of drainage fluid at the time of drain removal was used as the primary endpoint in a non-inferiority test with a significance level of 5%. The secondary endpoints included number and size of hemostatic agents required, adhesion of the hemostatic agent to the bleeding surface, intraoperative hemostatic effect, duration of drainage and adverse events during a six-month follow-up period.

RESULTS

A total of 150 patients (ORC-Coll: 75; CBFS: 75) were included. After operation, total volume of drainage fluid was 68.20±44.56mL in the ORC group and 68.21±40.20mL in the CBFS group. The non-inferiority of ORC-Coll compared to CBFS with regard to hemostatic efficacy was shown at a significance level of 5%. The results demonstrated effectiveness in achieving hemostasis without adverse events.

CONCLUSIONS

ORC-Coll is an effective hemostatic agent and barrier sealant without blood components, which ensures reliable prevention of intra- and postoperative bleeding. With use of the new technique, any risks associated with the use of human blood components are a priori eliminated.

Cytokines in Platelet Concentrates

There are many cytokines that have been shown to increase in platelet concentrates during storage including: proinflammatory cytokines, chemokines, and transforming growth factor β. The concentrations of these cytokines can be variable depending on the method of platelet preparation, and the leukocyte and/or platelet concentration in the product. The clinical significance of these cytokines is questionable; however, clinical data suggests that tike proinflammatory cytokines may play an important role in causing febrile non-hemolytic transfusion reactions. The clinical data to support a causative role in these reactions includes: correlational studies where high concentrations of proinflammatory cytokines were associated with a higher frequency of reactions; observational studies showing that the transfusion of platelet products with high leukocyte counts have a higher likelihood of causing reactions; and, experimental studies where products with low cytokine levels seldom cause FNHTR. The clinical relevance of chemokines and other growth factors detected in platelet concentrates remains inconclusive.

Haemovigilance of reactions associated with red blood cell transfusion: comparison across 17 Countries

BACKGROUND AND OBJECTIVES

The recent establishment of the National Healthcare Safety Network Hemovigilance Module in the United States affords an opportunity to compare results with those of other developed nations.

MATERIALS AND METHODS

Using data from national haemovigilance systems, reactions associated with red blood cell (RBC) transfusion and residual risks of transfusion-transmitted infectious diseases were assembled from 17 nations. Country-specific rates of adverse events were pooled using random-effects Poisson regression.

RESULTS

Febrile non-haemolytic and delayed serologic transfusion reactions were the most frequent adverse events reported after RBC transfusion, occurring in 26 patients per 100 000 RBC units and 25 patients per 100 000 RBC units administered, respectively. Rates of allergic, febrile non-haemolytic and delayed haemolytic transfusion reactions in the United States were significantly greater than the pooled rates from other countries. Frequencies of adverse events generated from the national haemovigilance programme in the United States were considerably lower than when obtained through active surveillance.

CONCLUSION

Haemovigilance reports of adverse events in the United States are comparable to, or greater than, reports from other developed countries. Rates generated from haemovigilance programmes are lower than those obtained through active surveillance. The lack of universal leucoreduction of RBC units may be a contributing factor to the higher rate of some adverse events in the United States.

T-cell suppression by red blood cells is dependent on intact cells and is a consequence of blood bank processing

BACKGROUND

Red blood cells (RBCs) suppress T-cell responsiveness through a mechanism requiring cell-cell contact. Questions remain as to whether this effect is an allogeneic response, related to cell death, or dependent on particular components of the RBCs.

STUDY DESIGN AND METHODS

Peripheral T cells were isolated from healthy donors and exposed to stored allogeneic RBCs or autologous RBCs after processing. RBCs were lysed by hypotonic solvent to produce cellular ghosts. Tritiated thymidine proliferation assays were utilized. Cultures were saturated with interleukin (IL)-2 to determine whether impaired IL-2 synthesis played a role.

RESULTS

T-cell proliferation was suppressed by both autologous and allogeneic RBCs. RBC membrane integrity does enhance T-cell suppression. T-cell death is not responsible for the suppressive changes. IL-2 synthesis is suppressed in RBC-exposed T cells but addition of exogenous IL-2 does not rescue proliferative capabilities. Proliferation of T cells was inhibited with RBC exposure but mitigated with the addition of fresh RBCs.

CONCLUSIONS

T-cell suppression is enhanced by intact RBCs but this effect is unrelated solely to alloantigens. Neither apoptosis nor necrosis of T cells contributes to this phenomenon. IL-2 synthesis is suppressed after RBC exposure as a consequence of T-cell inhibition, but is not the primary cause of suppression. Fresh RBCs do not mediate T-cell suppression, indicating that changes in the RBC and development of the storage lesion may occur during initial blood bank processing.

Retrospective evaluation of adverse transfusion reactions following blood product transfusion from a tertiary care hospital: A preliminary step towards hemovigilance

Background:

The goal of hemovigilance is to increase the safety and quality of blood transfusion. Identification of the adverse reactions will help in taking appropriate steps to reduce their incidence and make blood transfusion process as safe as possible.

Aims:

To determine the frequency and type of transfusion reactions (TRs) occurring in patients, reported to the blood bank at our institute.

Materials and Methods:

A retrospective review of all TRs reported to the blood bank at the All India Institute of Medical Sciences, between December 2007 and April 2012 was done. All the TRs were evaluated in the blood bank and classified using standard definitions.

Results:

During the study period a total of 380,658 bloods and blood components were issued by our blood bank. Out of the total 196 adverse reactions reported under the hemovigilance system, the most common type of reaction observed was allergic 55.1% (n = 108), followed by febrile non-hemolytic transfusion reaction (FNHTR) 35.7% (n = 70). Other less frequently observed reactions were Anaphylactoid reactions 5.1% (n = 10), Acute non-immune HTRs 2.6% (n = 5), Circulatory overload 0.5% (n = 1), Transfusion related acute lung injury 0.5% (n = 1), Delayed HTRs 0.5% (n = 1). Not a single case of bacterial contamination was observed.

Conclusion:

The frequency of TRs in our patients was found to be 0.05% (196 out of 380,658). This can be an underestimation of the true incidence because of under reporting. It should be the responsibility of the blood transfusion consultant to create awareness amongst their clinical counterpart about safe transfusion practices so that proper hemovigilance system can be achieved to provide better patient care.

Why implement universal leukoreduction?

The improvement of transfusion medicine technology is an ongoing process primarily directed at increasing the safety of allogeneic blood component transfusions for recipients. Over the years, relatively little attention had been paid to the leukocytes present in the various blood components. The availability of leukocyte removal (leukoreduction) techniques for blood components is associated with a considerable improvement in various clinical outcomes. These include a reduction in the frequency and severity of febrile transfusion reactions, reduced cytomegalovirus transfusion-transmission risk, the reduced incidence of alloimmune platelet refractoriness, a possible reduction in the risk of transfusion-associated variant Creutzfeldt-Jakob disease transmission, as well as reducing the overall risk of both recipient mortality and organ dysfunction, particularly in cardiac surgery patients and possibly in other categories of patients. Internationally, 19 countries have implemented universal leukocyte reduction (ULR) as part of their blood safety policy. The main reason for not implementing ULR in those countries that have not appears to be primarily concerns over costs. Nonetheless, the available international experience supports the concept that ULR is a process that results in improved safety of allogeneic blood components.

Noninfectious complications of blood transfusion

CONTEXT

Serious noninfectious complications are far more likely to occur than viral disease transmission from blood component transfusion.

OBJECTIVE

To compile a comprehensive list of the noninfectious risks of transfusion, examples of published risk estimates, and summaries of recent information regarding cause, prevention, or management of noninfectious transfusion risks.

DATA SOURCES

Information was obtained from peer-reviewed English-language medical journal publications since 1990.

CONCLUSIONS

Early complications, although potentially more serious, usually occur less frequently (<1 in 1000 transfusions) than late complications, which often affect more than 1% of recipients. Areas of active investigation and discussion include acute hemolytic reactions, transfusion-related acute lung injury, red cell alloimmunization, platelet transfusion refractoriness, and transfusion immunosuppression. Continued effort toward research and education to promote recognition and prevention of noninfectious complications associated with blood components is warranted.

Acetaminophen and diphenhydramine premedication for allergic and febrile nonhemolytic transfusion reactions: good prophylaxis or bad practice?

Febrile nonhemolytic and allergic reactions are the most common transfusion reactions, but usually do not cause significant morbidity. In an attempt to prevent these reactions, US physicians prescribe acetaminophen or diphenhydramine premedication before more than 50% of blood component transfusions. Acetaminophen and diphenhydramine are effective therapies for fever and allergy, respectively, so their use in transfusion has some biologic rationale. However, these medications also have potential toxicity, particularly in ill patients, and in the studies performed to date, they have failed to prevent transfusion reactions. Whether the benefits of routine prophylaxis with acetaminophen and diphenhydramine outweigh their risks and cost requires reexamination, particularly in light of the low reaction rates reported at many institutions even when premedication is not prescribed.

Optimizing platelet transfusion therapy

Platelet transfusions are widely used. Prophylactic transfusions are employed in severely thrombocytopenic patients without evidence of bleeding, but no randomized trial data prove the safety or efficacy of this approach. Randomized trials have demonstrated the equivalence of transfusion triggers of 10,000 and 20,000/microl for prophylactic transfusions. The former threshold is potentially safer for the patient, conservative of donor resources and leads to lower costs, with perhaps a slightly greater risk of minor hemorrhage. Randomized trials have demonstrated the equivalence of pheresis or whole blood-derived platelet transfusions. The former present a lower risk for infectious agents, and the latter are less expensive and a more efficient use of limited donor resources. Randomized trials prove that leukoreduced and ABO identical platelet transfusions reduce the risks of HLA alloimmunization and platelet transfusion refractoriness (both leukoreduction and ABO matching), transfusion reactions (leukoreduction) and CMV transmission (leukoreduction). Leukoreduction and ABO matching of platelet transfusions also have been associated in preliminary observational studies with reduced morbidity and mortality in surgical patients and reduced infections in patients with leukemia. These results require further investigation. Future challenges include (1) determining the best approach to bacterial contamination of platelets, whether by detection methods or pathogen inactivation and (2) determining the threshold for prophylactic platelet transfusions in thrombocytopenic patients undergoing surgery or invasive procedures.

Universal leukodepletion of blood components results in a significant reduction of febrile non-hemolytic but not allergic transfusion reactions

BACKGROUND

Universal leukodepletion of blood components to prevent acute non-hemolytic transfusion reactions (NHTRs) is still a subject of debate.

PATIENTS AND METHODS

Transfusion-associated NHTRs observed at our hospital in the last 6 years were retrospectively analyzed. Buffy-coat depleted red blood cells (bc-RBCs), and if indicated, leucodepleted post-storage (ld-RBCs) were initially used. In April 1997, universal leukodepletion was implemented at our hospital, and thereafter only prestorage ld-RBCs were used. All platelet concentrates transfused during this time were prestorage filtered single-donor apheresis platelets (SDAPs).

RESULTS

A total of 163,090 blood products were transfused from April 1995 to April 2001 (bc-RBC: n=34,040 units; ld-RBC: n=66,967; SDAP: n=14,516; FFP: n=47,567). The number of post-transfusion febrile NHTRs occurring with each blood product was 65 (0.19%) for bc-RBCs, 8 (0.16%) for post-storage ld-RBCs, 16 (0.03%) for prestorage ld-RBCs, 16 (0.11%) for SDAPs, and 10 (0.02%) for FFP. Allergic reactions (n=116) were most frequently observed after SDAP transfusion (0.32%) and occurred at a similarly low rate after transfusion of all other blood components (0.03-0.08%).

CONCLUSION

In conclusion, acute NHTRs rarely occur after the use of leukodepleted blood components. Prestorage appears to be more effective than post-storage leukodepletion in preventing febrile reactions following a blood transfusion.

Factors influencing moderate to severe reactions to PLT transfusions: experience of the TRAP multicenter clinical trial

BACKGROUND

During the Trial to Reduce Alloimmunization to Platelets (TRAP Trial), data were prospectively collected for 8769 PLT transfusions regarding the frequency of moderate to severe PLT transfusion reactions.

STUDY DESIGN AND METHODS

At seven centers, 598 patients were randomly assigned to receive unmodified pooled random-donor PLT concentrates (PCs), UV-B-irradiated PCs, filtered PCs, or filtered random-donor apheresis PLTs.

RESULTS

Moderate to severe transfusion reactions were an increase in temperature of at least 2 degrees C, chills with rigors, extensive urticaria, dyspnea, cyanosis, or bronchospasm. These reactions occurred with 2.2 percent of the transfusions in 22 percent of the patients. Transfusion reactions were associated with WBC counts of more than 5 x 10(6) per transfusion (p = 0.002) and transfusions stored for more than 48 hours (p = 0.02). PLT counts before transfusion were significantly lower for transfusions associated with reactions (p = 0.005). Neither UV-B irradiation nor apheresis PLTs independently influenced reaction rates. The PLT increment at 1 hour after transfusion was lower for transfusions associated with reactions (p = 0.004), and the frequency of reactions was higher in PLT refractory patients (p < 0.001).

CONCLUSIONS

The provision of either fresh and/or WBC-reduced PLTs may decrease the frequency of PLT transfusion reactions and improve PLT transfusion efficacy.

[Fever-shivers reaction and standard platelet concentrates transfusion: a prospective study]

Fever-shivers reaction (FSR) is the most frequent transfusion immediate incident related to platelet transfusions. The aim of our prospective study was to assess the frequency of the different immediate incidents, especially the frequency and the causes of the FSR, observed during the transfusion of standard platelet concentrates (SPC). For each FSR, analysis of causes included: a bacterial culture of the implicated SPC, a blood culture and HLA antibody screening (lymphocytotoxicity assay) among the patients. In the study period, 34 patients were followed during 74 transfusions. Ten immediate incidents were noted; FSR: N = 8, erythema-urticaria: N = 1 and nausea-vomit: N = 1. The FSR was observed in 6 patients who received 56 SPC. Analysis of causes of this reaction revealed that: HLA antibodies were present in one patient; bacterial contamination was not found neither among the patients nor in the implicated SPC, and the risk of the FSR occurrence rose with increased storage time of the SPC transfused. Indeed, a significant difference was noted between the mean age of the SPC implicated in the FSR and the mean age of those not implicated (P = 0,0028). In conclusion, the FSR is a frequent incident observed during SPC transfusions. In the majority of cases, the cause of this reaction was not identified. Further studies will be necessary to better understand the physiological mechanisms of the FSR.

Biologic activity of RANTES in apheresis PLT concentrates and its involvement in nonhemolytic transfusion reactions

BACKGROUND

RANTES, one of the PLT-derived biologic response modifiers, accumulates in PLT concentrates (PCs) during storage and may play a causative role in nonhemolytic transfusion reactions (NHTRs) after PC transfusion.

STUDY DESIGN AND METHODS

To investigate the association of RANTES with NHTRs, the biologic activity of RANTES in the supernatant of stored PC at the intravascular concentration expected after PC transfusion was assessed by examining chemotaxis and histamine release in human basophils. In addition, the levels of RANTES in PCs involved in NHTRs were compared with those in PCs causing no transfusion reactions.

RESULTS

The supernatant of PC diluted to contain 1 nM RANTES significantly increased the migration of and release of histamine from basophils. Neutralizing antibody to RANTES suppressed the PC-triggered migration, but not histamine release. The levels of RANTES in PCs involved in NHTRs after PC transfusion were comparable to those in PCs that did not cause any transfusion reactions.

CONCLUSION

RANTES that accumulated in PCs during storage was biologically active in a basophil chemotaxis assay at the intravascular concentration expected after PC transfusion. However, the NHTRs after PC transfusion were not simply related to the RANTES level in PCs.

Risks associated with transfusion of cellular blood components in Canada

We provide a comprehensive review of risks associated with allogeneic red blood cell and platelet transfusions in Canada. The review focuses on clinically symptomatic noninfectious transfusion risks (acute and delayed hemolytic, febrile nonhemolytic [FNHTR], allergic, volume overload, transfusion-related acute lung injury, graft-versus-host disease, and posttransfusion purpura) and the risk of clinically significant disease from transfusion-transmitted infections. Data sources include information from Canadian Blood Services, Héma-Québec, Health Canada, and the Québec Hemovigilance System as well as published information from research studies and international hemovigilance systems. We estimate that in 2000 the aggregate risk of potentially severe reactions (excluding FNHTR and minor allergic reactions) was 43.2 per 100000 red cell units (95% confidence interval [CI]: 38.7-48.1), affecting 337 recipients, and 125.7 per 100000 platelet pools of 5 units (95% CI: 100.8-154.9), affecting 88 recipients. The most frequent potentially severe outcomes for red cell transfusion were hemolytic reactions and volume overload and for platelet transfusion were major allergic reactions and bacterial contamination. The current risk of human immunodeficiency virus and hepatitis C virus transmission is approximately 1 in 4 million and 1 in 3 million units, respectively. These estimates are useful for decisions concerning transfusion therapy, the informed consent process, and for evaluating efficacy of interventions to reduce risk.

Bacterial Contamination of Blood Components: Risks, Strategies, and Regulation

Bacterial contamination of transfusion products, especially platelets, is a longstanding problem that has been partially controlled through modern phlebotomy practices, refrigeration of red cells, freezing of plasma and improved materials for transfusion product collection and storage. Bacterial contamination of platelet products has been acknowledged as the most frequent infectious risk from transfusion occurring in approximately 1 of 2,000–3,000 whole-blood derived, random donor platelets, and apheresis-derived, single donor platelets. In the US, bacterial contamination is considered the second most common cause of death overall from transfusion (after clerical errors) with mortality rates ranging from 1:20,000 to 1:85,000 donor exposures. Estimates of severe morbidity and mortality range from 100 to 150 transfused individuals each year.

Concern over the magnitude and clinical relevance of this issue culminated in an open letter calling for the “blood collection community to immediately initiate a program for detecting the presence of bacteria in units of platelets.” Thereafter, the American Association of Blood Banks (AABB) proposed new standards to help mitigate transfusion of units that were contaminated with bacteria. Adopted with a final implementation date of March 1, 2004, the AABB Standard reads “The blood bank or transfusion service shall have methods to limit and detect bacterial contamination in all platelet components.”

This Joint ASH and AABB Educational Session reviews the risks, testing strategies, and regulatory approaches regarding bacterial contamination of blood components to aid in preparing practitioners of hematology and transfusion medicine in understanding the background and clinical relevance of this clinically important issue and in considering the approaches currently available for its mitigation, as well as their implementation.

In this chapter, Drs. Hillyer and Josephson review the background and significance of bacterial contamination, as well as address the definitions, conceptions and limitations of the terms risk, safe and safety. They then describe current transfusion risks including non-infectious serious hazards of transfusion, and current and emerging viral risks. In the body of the text, Dr. Blajchman reviews the prevalence of bacterial contamination in cellular blood components in detail with current references to a variety of important studies. He then describes the signs and symptoms of transfusion-associated sepsis and the sources of the bacterial contamination for cellular blood products including donor bacteremia, and contamination during whole blood collection and of the collection pack. This is followed by strategies to decrease the transfusion-associated morbidity/mortality risk of contaminated cellular blood products including improving donor skin disinfection, removal of first aliquot of donor blood, pre-transfusion detection of bacteria, reducing recipient exposure, and pathogen reduction/inactivation. In the final sections, Drs. Vostal, Epstein and Goodman describe the regulations and regulatory approaches critical to the appropriate implementation of a bacterial contamination screening and limitation program including their and/or the FDA’s input on prevention of bacterial contamination, bacterial proliferation, and detection of bacteria in transfusion products. This is followed by a discussion of sampling strategy for detection of bacteria in a transfusion product, as well as the current approval process for bacterial detection devices, trials recommended under “actual clinical use” conditions, pathogen reduction technologies, and bacterial detection and the extension of platelet storage.

Limited efficacy of universal leucodepletion in reducing the incidence of febrile nonhaemolytic reactions in red cell transfusions

This article demonstrates a 62% reduction in the number of febrile nonhaemolytic transfusion reactions (FNHTRs) and 50% reduction in febrile reaction rate associated with red cell transfusions following graded introduction of universal leucodepletion. Though this is a statistically significant reduction (P = 0.009), it shows limited efficacy in abrogating this complication. We also found a reduction in the proportion of cases of FNHTRs with lymphocytotoxic antibodies over the period studied from 54% in 1998, 28% in 1999 to 23% in 2000. This corresponds to a relative increase in the number of febrile reactions without human leucocyte antigen (HLA) antibodies following full implementation of universal leucodepletion, as the total number of reported reactions actually fell considerably during the period. The increase in the number of cases without HLA antibodies was directly proportional to the increase in the number of leucodepleted units used.

Bacterial contamination of platelet concentrates: incidence, significance, and prevention

Severe transfusion reactions associated with bacteria and/or their products, during or following a blood transfusion, were one of the earliest recognized complications of allogeneic blood transfusions. Bacterial contamination of blood products has thus been a problem for many decades and at present is likely the most common microbiological cause of transfusion-associated morbidity and mortality. Transfusion-associated sepsis due to contaminated platelet concentrates appears to be much more common than that due to contaminated red blood cells. The overall incidence of contaminated cellular blood products is approximately 1 in 3,000. However, transfusion to a recipient of a contaminated platelet unit may not necessarily be associated with clinically apparent morbidity, because the majority of contaminated platelet units contain relatively few organisms. In a minority of instances, contaminated units contain large numbers of potentially virulent bacteria, as well as endotoxins, and their transfusion is often associated with significant recipient morbidity and mortality. The incidence of severe septic episodes has not been clearly established, but is probably of the order of 1 per 50,000 platelet units transfused. With heightened awareness in recent years of the possibility that platelet transfusion-associated septic episodes can occur, a variety of measures have been proposed, and in some cases implemented, to try to prevent and control this transfusion risk.

[Analysis of 516 reports of reactions after the transfusion of labile blood products]

BACKGROUND

In order to assess the implemented preventive measures of transfusion reactions (TR) and to make a study of residual reactions, we analyzed 516 TR reports from 14 hospitals, for three years since 1996 to 1998.

METHODS

Clinical signs were classified according to seven etiologic categories. Systematic anti-erythrocyte and anti-leucocyte detection, as well as bacterial control of the returned bag were performed.

RESULTS

The TR incidence is 3.7 per 1.000 products. Platelet concentrates (PC) provoke 7.4 TR per 1.000 transfusions, and red cell concentrates (RCC) 3.8. There are as many TR with apheresis platelets (AP), pre-storage leuco-depleted, as with random platelets, post-storage leuco-depleted, and as many with leuco-depleted RCC as with non leuco-depleted RCC. Leuco-depleted AP provoke more allergic reactions than other blood components. TR with AP are much more frequent in children than in adults. Plasma removal from AP before transfusion decreases reaction frequency.

CONCLUSIONS

The lack in efficacy failure of pre-storage deleucocytation in TR prevention should be due to related patient factors. Etiology of AP allergic reactions deserves further study. PC suspension in synthetic medium before transfusion is an efficient means for RT decreasing. Hemovigilance system has to be improved so that all TR be reported.

Donor neutrophil function after plateletpheresis

BACKGROUND

Neutrophils are important mediators of inflammation and may be activated by foreign surfaces in apheresis systems. Because most of the WBCs are returned to the donor, it was investigated whether artificial activation leads to altered donor neutrophil function.

STUDY DESIGN AND METHODS

Three apheresis systems (Amicus, Autopheresis-C, and CS-3000; all: Baxter Fenwal) were investigated. Preapheresis and postapheresis blood samples were drawn from 10 volunteer donors, with all three apheresis systems used in random order for each donor. Changes in neutrophil phagocytic ability, oxidative burst, and expression of L-selectin and CD11b were measured by flow cytometry, and plasma concentrations of myeloperoxidase and lactoferrin were measured by EIA. Complement activation was evaluated by quantification of C3bc and the terminal complement complex by EIA.

RESULTS

Neutrophil expression of L-selectin increased after apheresis (p = 0.02), and the production of oxygen radicals was reduced (p = 0.01). This effect was possibly a result of priming. Complement was not activated. There were no significant differences in neutrophil function after apheresis with any of the three apheresis systems.

CONCLUSIONS

Neutrophil function was altered after apheresis, although to a very small extent, and contact between neutrophils and the foreign surface in the apheresis systems is found to be a biotolerant procedure.

Platelets expressing P-selectin and platelet-derived microparticles in stored platelet concentrates bind to PSGL-1 on filtrated leukocytes

The levels of interleukin-6 and platelet-derived microparticles (PMPs) were measured in the blood of 137 patients with side effects from platelet concentrate (PC) transfusion with leukocyte removal filtration, P-selectin-expressing platelet and PMPs in stored PC before and after the filtration, and filtered leukocytes positive for P-selectin glycoprotein ligand-1. The side effects, which were observed in 203 transfusions for 84 patients with hematologic disease and 53 patients with nonhematologic disease with no significant difference between the two groups, included urticaria (75.9%), erythema (18.7%), and fever (17.2%), but no anaphylactic reactions. The levels of interleukin-6 and PMP correlated in both groups, and were significantly higher in the hematologic disease group than in the nonhematologic disease group. The level of PMP, but not interleukin-6, was significantly higher for patients testing positive for allergic reaction than for those testing negative. In the stored PC prior to filtration, the level of interleukin-6 was normal. The level of P-selectin-expressing platelets and PMPs was elevated before filtration, but was significantly lower after filtration. Taken together, the results suggest that PMP is involved in the generation of transfusion reactions, and indicate that both platelets and PMP displaying P-selectin bind to P-selectin glycoprotein ligand-1 of leukocytes retained by the leukocyte filter.

Inactivation of WBCs in RBC suspensions by photoactive phenothiazine dyes: comparison of dimethylmethylene blue and MB

BACKGROUND

The transfusion of blood components containing WBCs can cause unwanted complications, which include virus transmission, transfusion-associated GVHD, alloimmunization, febrile reactions, and immunomodulation. Phototreatment with 4 microM of dimethylmethylene blue (DMMB) and 13 J per cm(2) of white light irradiation has previously been shown to be an effective way to inactivate different models of enveloped and nonenveloped viruses in RBC suspensions, with minimum damage to RBCs. The present study compares WBC photoinactivation in buffy coat after DMMB or MB phototreatment under virucidal conditions.

STUDY DESIGN AND METHODS

Buffy coat diluted to 30-percent Hct was treated with the dye and white light. Isolated WBCs were assayed for cell proliferation and viability by an assay using a tetrazolium compound, limiting dilution analysis, DNA fragmentation, and flow cytometry assays.

RESULTS

DMMB and 2.5 J per cm(2) of light phototreatment can inactivate T cells to the limit of detection by limiting dilution analysis (>4.76 log reduction). No WBC proliferation activity was observed after DMMB and 3.8 J per cm(2) of light. DNA degradation after DMMB phototreatment was light dependent. In addition, DMMB phototreatment induced apoptosis in WBCs. In contrast, MB phototreatment under virucidal conditions did not cause significant changes in the viability of WBCs. Neither DNA degradation nor signs of apoptosis were observed after MB phototreatment.

CONCLUSION

DMMB phototreatment inactivates T-lymphocytes, the cells that cause GVHD.

Rational manipulation of oxygen delivery

BACKGROUND

Optimization of oxygen delivery remains the best method to prevent and the only way to treat common intensive care unit syndromes such as sepsis, multiple organ dysfunction, and acute lung injury. This paper reviews the elements of oxygen delivery, describes how clinical interventions work through those elements to alter oxygen delivery, reviews theoretical and empirical data relating to manipulation of each element, and distinguishes between therapeutic means and clinical endpoints in the care of the critically ill.

MATERIALS AND METHODS

Recent literature is reviewed. Relevant equations are detailed. Computer models and patient data illustrate key points.

RESULTS

Clinical interventions intended to improve oxygen delivery all work through at least one of seven variables (oxygen saturation, hemoglobin concentration, heart rate, mean arterial blood pressure, systemic vascular resistance, end-diastolic volume, and ejection fraction). Because interventions that increase oxygen delivery are always accompanied by physiologic costs, cavalier application of any therapy in the intensive care unit may actually decrease oxygen delivery, harming the critically ill patient. Various clinical indicators may be used as endpoints to guide therapy.

CONCLUSIONS

While a systematic consideration of the elements of oxygen delivery reveals weaknesses in experimental evidence guiding optimal treatment of shock, reasonable strategies as well as avoidable pitfalls emerge from the data. Furthermore, facility with each of the elements of oxygen delivery makes ICU management easier to teach and to apply.

The utility of < or =3-day-old whole-blood platelets in reducing the incidence of febrile nonhemolytic transfusion reactions

BACKGROUND

Febrile nonhemolytic transfusion reactions (FNHTRs) to platelet transfusions have been linked to the presence of cytokines in supernatant plasma. Cytokine concentration is directly related to WBC content and storage time. This study evaluated the effect of limiting the storage time of random-donor platelet concentrates on the FNHTR rate.

STUDY DESIGN AND METHODS

FNHTR rates were calculated retrospectively for single-donor apheresis platelet (SDP) and pooled random-donor platelet (PP) transfusions given during three consecutive 5-month study periods (November 1995 to February 1997) to patients on a single hematology/oncology/bone marrow transplant unit. Transfusion practice policies were: Baseline Period, SDPs preferred; Study Period A, PPs preferred; and Study Period B, < or =3-day-old PPs preferred. FNHTR rates were calculated from physicians' interpretations of reported reactions and the total number of SDP and PP transfusions in each period. SDPs were collected on two cell separators. All platelet components were filtered at issue in the laboratory by WBC-reduction filters.

RESULTS

FNHTR rates for PP transfusions were: baseline, 11.1 percent (3/27); Study Period A, 4.6 percent (22/481); and Study Period B, 1.1 percent (3/282). The rates for SDP transfusions were 0. 15 percent (1/650), 0.75 percent (2/267), and 0.36 percent (1/273), respectively. The FNHTR rate for < or =3-day-old PPs was significantly less than the rate for older PPs (p = 0.0086 for Study Period A vs. Study Period B), and was not significantly different than that for SDPs (p = 0.33 for PPs vs. SDPs in Study Period B).

CONCLUSION

Limiting transfusion of PPs to those stored </=3 days is an effective strategy in reducing the rate of FNHTR and results in an FNHTR rate comparable to that seen with SDPs.

Febrile and allergic transfusion reactions after the transfusion of white cell-poor platelet preparations

BACKGROUND

Nonhemolytic transfusion reactions (NHTRs) frequently occur after platelet transfusions. White cell (WBC)-derived inflammatory cytokines can cause these reactions, but they are rarely found in WBC-poor platelet preparations. Transfusion reactions were investigated with regard to the residual WBC content in the stored platelet concentrate in two consecutive study periods.

STUDY DESIGN AND METHODS

In the first study period, platelet concentrates were WBC-reduced by bedside filtration. In the second period, all platelet concentrates were filtered before storage. Recipients who experienced transfusion reactions were examined with regard to their main clinical symptoms during and after transfusion. In the supernatant of the involved platelet concentrates, concentrations of interleukin (IL)-1beta, IL-6, IL-8, tumor necrosis factor (TNF)alpha, macrophage inflammatory protein 1alpha, and RANTES were analyzed.

RESULTS

The incidence of transfusion reactions remained steady when the transfusion regimen was changed from bedside filtration to prestorage WBC filtration (1.63% and 1.56%; p = 0.84). In both periods, NHTRs were predominantly of allergic origin. Inflammatory mediators IL-1beta, IL-6, IL-8, and TNFalpha were detectable in only a minority of platelet components involved in NHTRs. Platelet concentrates involved in allergic reactions contained high concentrations of RANTES (668 +/- 223 ng/mL).

CONCLUSIONS

Prestorage WBC filtration did not reduce the incidence of these reactions, and inflammatory cytokines were of minor relevance. The proinflammatory platelet-derived chemokine RANTES, which accumulates even in WBC-reduced platelet concentrates, was associated with allergic transfusion reactions. Platelet-derived mediators may be a key to understanding NHTRs.

Pathophysiology of febrile nonhemolytic transfusion reactions

Most febrile nonhemolytic transfusion reactions (FNHTR) to platelets are caused by cytokines that accumulate in the product during storage. There have been numerous studies that have demonstrated high concentrations of leukocyte- and platelet-derived cytokines in stored platelet products. The mechanism of cytokine accumulation is not understood; however, recent studies have suggested that leukocyte apoptosis and/or monocyte activation during the manufacturing process may play a role. Additional support of cytokines as a cause of FNHTR is provided by a recently published randomized controlled trial that shows that removal of the supernatant plasma from platelets before transfusion significantly lowers the frequency of reactions and eliminates most of the severe reactions associated with platelet transfusions. Although cytokines appear to play a major role in causing platelet reactions, there is little evidence to support their role in causing erythrocyte reactions. Hence, it appears that most febrile nonhemolytic transfusion reactions to erythrocytes are probably the result of an incompatibility between leukocytes in the erythrocyte product and antibodies in the recipient's plasma. Recent studies have confirmed that the concentrations of proinflammatory cytokines in a wide variety of stored erythrocyte products are low. Also, there is no clinical evidence to suggest that the small quantities of cytokines present in stored erythrocyte products contribute to acute reactions to these products when transfused.

Effects of prestorage white cell reduction on platelet aggregate formation and the activation state of platelets and plasma enzyme systems

BACKGROUND

The introduction of prestorage white cell (WBC) reduction in random-donor platelet concentrates in Canada has increased the occurrence of particulate material in PCs. The effects of filtration on platelet activation state and the activation of plasma enzyme systems were assessed.

STUDY DESIGN AND METHODS

Particulate material was examined by light microscopy, electron microscopy, protein electrophoresis, and biochemical analysis. Thirty PCs (10 unfiltered, 20 filtered) were examined during processing and 5-day storage for pH, platelet count and mean volume, morphology, activation marker expression, and hypotonic shock response. Complement activation, thrombin generation, and fibrinolysis were assessed by using specific enzyme immunoassays or chromogenic assays.

RESULTS

By all analyses, the particulate material appeared to be platelet aggregates. Platelets exposed to WBC-reduction filters expressed a significantly higher level of activation markers CD62 and CD63, altered morphology, and increased platelet microparticles throughout the storage period than did unfiltered platelets. Complement activation at the C3 level was significantly increased in filtered units with little evidence of coagulation or fibrinolytic system activation.

CONCLUSION

Exposure of platelets to filters during prestorage WBC reduction increased platelet activation and mildly increased complement activation over the levels during the storage period. These alterations can contribute to the formation of irreversible platelet aggregates during processing.

Antibodies to private and public HLA class I epitopes in platelet recipients

BACKGROUND

Transfusions or pregnancies can cause immunization against private HLA determinants and public epitopes shared by more than one private HLA antigen. HLA antibodies are correlated with febrile transfusion reactions, lower platelet response following platelet transfusion, and an increased rate of renal transplant rejection. Until now, antibody specificities in alloantisera from platelet recipients have been poorly characterized.

STUDY DESIGN AND METHODS

Consecutive serum screens from platelet recipients were analyzed for antibodies against private HLA class I antigens and public HLA epitopes using a serum analysis program based on the 2 x 2 table analysis of correlations. Serum screens of highly immunized patients and of patients with new alloimmunization events were reviewed separately.

RESULTS

Of the serum screens from 566 platelet recipients, 1577 indicated alloimmunization (panel-reactive antibodies >5%). The program assigned a specificity in 1024 of these screens (64.9%) and at least once in 522 of 566 patients (92.2%). In 267 patients, antibodies detecting public epitopes in the combined A- or B-locus cross-reacting groups were found; other public markers were detected in 39 patients. Patterns of reactivity were remarkably less stable than in patient groups previously studied. In many patients, antibodies with apparent private epitope specificity preceded the identification of antibodies against a shared marker of the same cross-reactive group. However, the disappearance of antibodies (whether or not this was followed by a new antibody against a private or public marker belonging to another cross-reacting group) was also observed.

CONCLUSION

The computerized analysis of microlymphocytotoxicity tests enhances the rate of antibody specification in sera from platelet recipients with lymphocytotoxic antibodies. The identified antibodies should be taken into account in the selection of platelet donors. The data confirm and extend previous observations on HLA class I antibodies and elucidate new alloimmunization events.

Risks, costs, and alternatives to platelet transfusions

The use of platelet transfusions has increased greatly in the past decade and is likely to continue to escalate because of the risks of thrombocytopenia in patients receiving dose-intensive cancer chemotherapy, the increased use of hematopoietic progenitor cell transplantation, and the prevalence of human immunodeficiency virus infection. Despite marked advances in procedures for ensuring the safety of platelets, including intensive donor screening, infectious disease marker testing, and increased use of leukodepletion techniques, platelet transfusions carry a significant risk for immunologic disorders and transmission of bacterial, viral, and perhaps other diseases and can entail a very high cost. In addition, thrombocytopenia has the potential to interfere with delivery of chemotherapy on schedule and at the planned doses, thus potentially compromising treatment outcome. The limitations of platelet transfusions have prompted the development of agents with the potential to stimulate platelet production and thus reduce or eliminate the need for transfusions. Two such agents, interleukin-11 (IL-11) and thrombopoietin (TPO), have demonstrated promise in clinical trials. In November, 1997, IL-11 received FDA approval for the prevention of severe thrombocytopenia in high risk patients receiving myelosuppressive chemotherapy. Thrombopoietic growth factors have the potential to greatly simplify and increase the safety of transfusion medicine.

Safety of the blood supply

Three of four recipients of transfusion in the United States are patients undergoing surgery, and despite promising advances in the development of alternatives to allogeneic blood transfusion, it is likely that for years to come this patient population will remain dependent on blood donated by volunteers. The safety of the blood supply has been questioned seriously since it became known that the human immunodeficiency virus could be transmitted by transfusion. In response to this threat, enforcement of strict donor eligibility criteria, removal of high risk donors from the donor pool, and testing of each donation with a panel of viral markers were instituted which have reduced the infectious risks of allogeneic blood transfusion dramatically during the last decade. The current safety of the blood supply is reviewed and the ongoing efforts to improve the safety of transfusions in the future are summarized briefly.

Manual and automated methods for the determination of leukocyte counts at extreme low levels: comparative evaluation of the Nageotte chamber and the Abbott Cell Dyn 3500 analyser

Leukodepleted or leukocyte-poor blood products (fresh-frozen plasma, packed red cell and platelet concentrates in particular) are widely used in current clinical practice. However, because the monitoring of leukodepletion efficiency is generally carried out (if at all) using the labour-intensive and relatively inaccurate manual Nageotte chamber technique, it is clear that any increased demand for leukodepletion monitoring would be difficult, if not impossible, to meet. As the need to identify an automated alternative to the Nageotte technique is important, this study was undertaken to evaluate such a possibility. White blood cells were enumerated in a representative series of filtered and non-filtered human blood components by both microscopic counting in the Nageotte chamber, and with the Abbott CD3500 automated haematology analyser. For the Nageotte estimate, a single analysis was made in accordance with standard procedures, whereas the automated analysis was achieved by making six replicate counts and determining the mean of four replicates after excluding the highest and lowest estimates. To determine linearity limits of the manual and automated procedures, freshly isolated leukocytes were admixed with cell-free plasma-pheresis plasma. Reasonable reproducibility (mean CV 10% for cell counts exceeding 100 cells/microL) and good linearity (r > 0.9) were observed for CD3500 determinations in four separate experiments. The manual and automated measurements also correlated well (r > 0.9) with no obvious inter-method bias for cell counts up to 40 cells/microL although there was some suggestion of lower absolute CD3500 counts in the range 40-130 cells/microL. For the comparative studies with filtered and non-filtered blood products, no significant method bias was seen with 70 individual red cell concentrates, but systematically higher CD3500 white blood cell counts were observed in the series of 68 platelet concentrates (probably due to the presence of platelet clumps). This study concludes that automation of white cell counts in blood products with the CD3500 analyser is feasible for quality control in the preparation of fresh-frozen plasma and red cell concentrates but is limited for the analysis of filtered platelet concentrates.

The role of cytokines in blood transfusion reactions

Recent advance in the understanding of the mechanism of hemolytic transfusion reactions results from the investigation of cytokine generation in in vitro models of incompatible red blood cell transfusion. Cytokines with pyrogenic and pro-inflammatory activities as well as cytokines with activating properties for granulocytes, monocytes and endothelial cells are produced in both 'intravascular' and 'extravascular' types of hemolytic reactions. It has also been demonstrated that cytokines are generated and accumulated in blood components such as platelet concentrates, during storage. A large part of febrile transfusion reactions results from transfusion of stored platelet concentrates containing high cytokine levels and not from antigen-antibody reactions. Prestorage removal of white blood cells, which generate cytokines during storage, from platelet concentrates reduces strongly the reaction incidence and should be standard practice.