It is time to reconsider the risks of transfusing RhD negative females of childbearing potential with RhD positive red blood cells in bleeding emergencies

A prehospital protocol for transfusion of low-titer O-positive whole blood in patients with hemorrhagic shock in Los Angeles County: Modeling the risk of hemolytic disease of the fetus and newborn

BACKGROUND

The Los Angeles Development and Rapid Operationalization of Prehospital Blood (LA-DROP) pilot will protocolize prehospital administration of low titer O-positive whole blood (LTO + WB) to patients with hemorrhagic shock in Los Angeles County (LAC). We sought to quantify the risk of death from hemolytic disease of the fetus and newborn (HDFN) associated with RhD-negative alloimmunization in females of childbearing potential (FCPs) as a result of LA-DROP.

STUDY DESIGN AND METHODS

Retrospective data from LAC EMS databases were used in combination with estimates from published literature to assign probability distributions to each event in the sequence required for a transfusion of LTO + WB to result in a death from HDFN. Markov chain Monte Carlo simulation was used to derive risk estimates.

RESULTS

We estimated that the proposed prehospital transfusion strategy would result on average in one death from HDFN for every 10,000 transfusions in the overall population (95% confidence interval [CI] 6000-25,000) and for every 1800 transfusions in FCPs (95% CI 1000-4300). Based on the projected annual volume of transfusions under LA-DROP, this would result in one death due to HDFN approximately every 26 years (95% CI 15-64).

DISCUSSION

The estimated per-transfusion risk of HDFN is similar to previously published work from other populations. The estimated frequency of deaths from HDFN associated with LA-DROP is lower than some previously published calculations, likely because of narrower eligibility criteria for transfusion.

Use of an anti-D-alloimmunization kinetics model to correct the interval censored D-alloimmunization rate following red blood cell transfusions

INTRODUCTION

The rate of D-alloimmunization amongst RhD-negative recipients of RhD-positive red blood cell (RBC) transfusions is not certain. Recipients with a short duration between the index RhD-positive transfusion and the last antibody detection test that did not show anti-D might become D-alloimmunized in the future. A regression model was developed to predict how often such patients might develop D-alloimmunization in the future to help account for the immunohematological uncertainty that accompanies having short serological follow up periods.

METHODS

Using the published literature on recipients who were intentionally transfused with RhD-positive RBCs and serially followed with antibody screens, as well as unpublished datasets, a regression model was constructed to demonstrate the timing of D-alloimmunization for recipients who became D-alloimmunized within 6 months following the index transfusion. The model was then applied to a series of RhD-negative hospitalized recipients of at least one unit of RhD-positive RBCs who did not become D-alloimmunized but who had fewer than 6 months of serological follow up to weight their contribution to the D-alloimmunization rate.

RESULTS

Overall, the rate of D-alloimmunization was 21/105 (20.0%). There were 39 patients whose last documented antibody screen was performed between 14 days and 6 months after the index RhD-positive transfusion, and these patients were entered into the weighted model. After applying the model, the D-alloimmunization rate rose to 26.3%.

CONCLUSION

Using a weighted model can help reduce the immunohematological uncertainty that accompanies the inclusion of patients with relatively short serological follow up in studies of RBC alloimmunization.

Adrenaline for traumatic cardiac arrest: A post hoc analysis of the PARAMEDIC2 trial

Introduction

There is controversy about the effectiveness of adrenaline in traumatic cardiac arrest. This study reports the patient characteristics and outcomes of adults with trauma-related out of hospital cardiac arrest treated with adrenaline or placebo.

Methods

This post-hoc, sub-group analysis of the Pre-hospital Randomised Assessment of Adrenaline in Cardiac Arrest-2 (PARAMEDIC-2) trial explored the effect of adrenaline on survival to hospital admission, longer-term survival and neurological outcomes amongst adults with trauma related out of hospital cardiac arrest. Individual patients were randomised through opening a single treatment pack which contained either 10 doses of 1 mg adrenaline or 0.9% saline placebo. Treating clinicians, investigators, outcome assessors and patients were blinded to treatment allocation. The primary outcome was survival to 30 days post cardiac arrest.

Results

123 of 8,014 enrolled patients (1.5%) sustained a traumatic cardiac arrest (66 in the adrenaline arm and 57 in the placebo arm). Three times as many patients were admitted to hospital alive in the adrenaline arm 16/66 (24.2%) compared to 5/56 (8.9%) in the placebo arm, unadjusted odds ratio 3.3 (95% confidence interval 1.1 to 9.6), p = 0.03; adjusted odd ratio 5.6 (95% CI 1.6 to 20.4), p = 0.009. A single patient, in the adrenaline arm, survived beyond 30 days (1/66 (1.5%) compared to 0/57 (0%)), who also experienced a favourable neurological outcome.

Conclusion

Adrenaline was associated with a trebling of the rate of survival to hospital admission. These data support the use of adrenaline in trauma related out of hospital cardiac arrest.

Registration

ISRCTN73485024.

Evolution of whole blood trauma resuscitation in childbearing age females: practice patterns and trends

Background

The use of low titer group O whole blood (LTOWB) for resuscitation of patients with traumatic hemorrhage is becoming increasingly common. Practices regarding the administration of RhD-positive LTOWB to childbearing age females (CBAFs) vary between institutions due to concerns about RhD alloimmunization. This study examined practices related to LTOWB transfusion as they pertain to age and sex.

Methods

This was a secondary analysis of the Shock, Whole blood, and Assessment of TBI (traumatic brain injury) trial, a prospective, multicenter observational cohort study where outcomes following LTOWB transfusion were analyzed at seven level 1 trauma centers between 2018 and 2021, as well as a survey on transfusion practices at these centers conducted in 2023. The proportion of patients who received LTOWB or components was examined over the course of the study and grouped by age and sex, and the RhD group of injured CBAFs was documented.

Results

A total of 1046 patients were evaluated: 130 females aged <50 years (CBAFs), 77 females aged ≥50 years; 661 males aged <50 years, and 178 males aged ≥50 years. Among them, 26.2% of CBAFs received RhD-positive LTOWB, whereas 57.1%-66.3% of other sex/age groups received LTOWB. The proportion of CBAFs who received LTOWB increased significantly throughout the 4 years of this study. Except for older women in years 2 and 4, CBAFs were significantly less likely to receive LTOWB than all other groups for the study period and individual years. Among the 33 CBAFs who received LTOWB and for whom an RhD type was available, 4/33 (12.1%) were RhD-negative, while 9/95 (9.5%) CBAFs who received component therapy were RhD-negative. RhD blood product selection practices varied considerably between institutions.

Conclusions

Many institutions transfused LTOWB to CBAFs. Policies regarding RhD product selection varied. Of the total cohort, the proportion of RhD-negative CBAFs who received LTOWB increased over time but remained lower than all other groups.

Level of evidence

3.

Optimizing O red blood cell concentrate usage in the emergency department in the era of patient blood management

BACKGROUND

Emergency transfusion may require the availability of O-negative red blood cell concentrates without pre-transfusion testing. At the Cliniques Universitaires Saint-Luc, the emergency department was used to having access to two decentralized O-negative red blood cell concentrates. This study aims to analyze the consumption of O-negative red blood cell concentrates in emergency situations both before and after the implementation of a novel strategy aiming at optimizing stocks. This strategy provides a combined allocation of one unit of O-positive red blood cell concentrate and one unit of O-negative red blood cell concentrate decentralized in the emergency department and reserve the transfusion of the negative unit only to under 45-year-old women and under 20-year-old men.

MATERIALS AND METHODS

A retrospective study was conducted of the transfusion and medical records of all patients who received immediate transfusions in the emergency department without pre-transfusion testing between 2008 and 2022.

RESULTS

A total of 193 patients received O red blood cell concentrates without pre-transfusion testing in emergency situations between 2008 and 2022. During the first 24 h of hospitalization, 354 O-negative units were transfused. Mean ratios of number of O-negative bags between 2008 and 2020 was 1.98 unit/patient. After implementation of the new strategy, the ratio in 2021 was 1.46 unit/patient and drastically decreased in 2022 to 0.79 unit/patient.

CONCLUSION

In situations of emergency, allocating O-negative units only for women younger than 45 years and men younger than 20 years could have saved 85% of O-negative red blood cell concentrates transfused (303/354) yet balancing the immunological risk. Limiting the number of delocalized units of O-negative red blood cell concentrates in the emergency department seems to lower O-negative consumption. With this strategy, the units spared could have been transfused to patients with greater needs (e.g., sickle cell patients or chronically transfused patients).

Survey of pediatric massive transfusion protocol practice at United States level I trauma centers: An AABB Pediatric Transfusion Medicine Subsection study

BACKGROUND

Trauma remains the leading cause of pediatric mortality in the United States. Although use of massive transfusion protocols (MTPs) in this population is widespread, optimal pediatric resuscitation is not well established. We sought to assess contemporary pediatric MTP practice in the United States.

STUDY DESIGN AND METHODS

A web-based survey was designed by the Association for the Advancement of Blood & Biotherapies (AABB) Pediatric Transfusion Medicine Subsection and distributed to select American College of Surgeons (ACS) Level I Verified pediatric trauma centers. The survey assessed current MTP policy, implementation, and recent changes in practice.

RESULTS

Response rate was 55% (22/40). Almost half of the respondents were from the South. The median RBC:plasma ratio was 1 (interquartile range 1-1.5). Protocolized fibrinogen supplementation was common while integration of antifibrinolytic therapy into MTPs was infrequent. Viscoelastic testing (VET) was available at most sites, 71% (15/21, one site did not respond), and was generally utilized on an ad-hoc basis. Roughly, a third of sites had changed their MTP in the past 3 years due to blood supply issues, and about a third reported having group O Whole Blood on-site.

CONCLUSION

MTP practice is similar throughout the United States. Though fibrinogen supplementation is common-other emerging interventions such as antifibrinolytic therapy or utilization of routine viscoelastic testing-are not widespread. Pediatric transfusion medicine experts must continue to follow practice change, as contemporary large trials begin to characterize new supportive modalities to optimize resuscitation in pediatric trauma patients.

RhD-Alloimmunization in Adult and Pediatric Trauma Patients

The actual risk of providing RhD-positive units to RhD-negative recipients remains debatable. There is no standard of care in the United States (US) to guide transfusion decisions regarding RhD type for patients with an unknown blood type, except for women of childbearing age and neonates. The risk of alloantibody formation by an RhD-negative patient exposed to RhD-positive blood is reported to be from 3% to 70%. Due to such wide variations, this review was undertaken to determine the prevalence of anti-D alloimmunization in trauma patients who are RhD-negative and were transfused RhD-positive blood products. This study used the "Preferred Reporting Items for Systematic Reviews and Meta-Analyses" (PRISMA) approach to answer the question, "In trauma patients who were transfused blood, what is the prevalence of alloimmunization to the D-antigen?" The review included all published articles through April 3, 2022 in databases. Articles published after the search period found by the authors were added to the manuscript if they addressed the primary question and there was unanimous consensus. There were 1683 full-text articles that met the search criteria, with 19 studies meeting eligibility criteria. In addition, 57 references were added after the search period had closed. The incidence of anti-D alloimmunization in adult trauma patients receiving whole blood varied from 7.8% to 42.7%. In contrast, incidence varied in patients receiving red blood cells (RBCs), from 0 to 94%, depending on number of categories analyzed. Anti-D alloimmunization with platelet transfusions varied from 0% to 19%. The alloimmunization rate increased with age and was detected only in children older than 5 years. Recent guidelines recommend the administration of Rh immune globulin (RhIG) to all traumatically injured patients who are both RhD-negative and pregnant. However, there is no specific guidance focused on the RhD-negative patient, pregnant or nonpregnant, and who have received RhD-positive red blood cells (RBC) and platelets. While numerous studies have attempted to evaluate the frequency of RhD alloimmunization rate in trauma settings, emerging data suggests that many factors affect this phenomenon. Additionally, the role of RhIG administration in cases of RhD-incompatible transfusions within the trauma setting adds complexity. As our trajectory propels us towards precision medicine and tailored transfusion practices, gaining a big data approach becomes indispensable.

Management Considerations for Air Medical Transport Programs Transfusing RhD-Positive Red Blood Cell-Containing Products to Females of Childbearing Potential

Recent years have seen increased discussion surrounding the benefits of damage control resuscitation, prehospital transfusion (PHT) of blood products, and the use of whole blood over component therapy. Concurrent shortages of blood products with the desire to provide PHT during air medical transport have prompted reconsideration of the traditional approach of administering RhD-negative red cell-containing blood products first-line to females of childbearing potential (FCPs). Given that only 7% of the US population has blood type O negative and 38% has O positive, some programs may be limited to offering RhD-positive blood products to FCPs. Adopting the practice of giving RhD-positive blood products first-line to FCPs extends the benefits of PHT to such patients, but this practice does incur the risk of future hemolytic disease of the fetus and newborn (HDFN). Although the risk of future fetal mortality after an RhD-incompatible transfusion is estimated to be low in the setting of acute hemorrhage, the number of FCPs who are affected by this disease will increase as more air medical transport programs adopt this practice. The process of monitoring and managing HDFN can also be time intensive and costly regardless of the rates of fetal mortality. Air medical transport programs planning on performing PHT of RhD-positive red cell-containing products to FCPs should have a basic understanding of the pathophysiology, prevention, and management of hemolytic disease of the newborn before introducing this practice. Programs should additionally ensure there is a reliable process to notify receiving centers of potentially RhD-incompatible PHT because alloimmunization prophylaxis is time sensitive. Facilities receiving patients who have had PHT must be prepared to identify, counsel, and offer alloimmunization prophylaxis to these patients. This review aims to provide air medical transport professionals with an understanding of the pathophysiology and management of HDFN and provide a template for the early management of FCPs who have received an RhD-positive red cell-containing PHT. This review also covers the initial workup and long-term anticipatory guidance that receiving trauma centers must provide to FCPs who have received RhD-positive red cell-containing PHT.

Receipt of RhD-positive whole blood for life-threatening bleeding in female children: A survey in alloimmunized mothers regarding minimum acceptable survival benefit relative to risk of maternal alloimmunization to anti-D

BACKGROUND

Low-titer group O whole blood (LTOWB) for treatment of hemorrhagic shock sometimes necessitates transfusion of RhD-positive units due to short supply of RhD-negative LTOWB. Practitioners must choose between using RhD-positive LTOWB when RhD-negative is unavailable against the risk to a female of childbearing potential of becoming RhD-alloimmunized, risking hemolytic disease of the fetus and newborn (HDFN) in future children, or using component therapy with RhD-negative red cells. This survey asked females with a history of red blood cell (RBC) alloimmunization about their risk tolerance of RhD alloimmunization compared to the potential for improved survival following transfusion of RhD-positive blood for an injured RhD negative female child.

STUDY DESIGN AND METHODS

A survey was administered to RBC alloimmunized mothers. Respondents were eligible if they were living in the United States with at least one red cell antibody known to cause HDFN and if they had at least one RBC alloimmunized pregnancy.

RESULTS

Responses from 107 RBC alloimmmunized females were analyzed. There were 32/107 (30%) with a history of severe HDFN; 12/107 (11%) had a history of fetal or neonatal loss due to HDFN. The median (interquartile range) absolute improvement in survival at which the respondents would accept RhD-positive transfusions for a female child was 4% (1%-14%). This was not different between females with and without a history of severe or fatal HDFN (p = .08 and 0.38, respectively).

CONCLUSION

Alloimmunized mothers would accept the risk of D-alloimmunization in a RhD-negative female child for improved survival in cases of life-threatening bleeding.

Ethical considerations in the use of RhD-positive blood products in trauma

BACKGROUND

Prehospital and early in-hospital use of low titer group O whole blood (LTOWB) for life-threatening bleeding has been independently associated with improved survival compared to component therapy. However, when RhD-positive blood products are administered to RhD-negative females of childbearing potential (FCP), there is a small future risk of hemolytic disease of the fetus and newborn (HDFN). This raises important ethical questions that must be explored in order to justify the use of RhD-positive blood products, including LTOWB, both in clinical practice and research.

METHODS

This essay explores the ethical challenges related to RhD-positive blood product administration to RhD-negative or RhD-unknown FCPs as a first-line resuscitation fluid in the trauma setting. These ethical issues include: issues related to decision-making, ethical analysis based on the doctrine of double effect (DDE), and attendant obligations incurred by hospitals that administer RhD-positive blood to FCPs.

RESULTS

Ethical analysis through the use of the DDE demonstrates that utilization of RhD-positive blood products, including LTOWB, in the early resuscitation of FCPs is an ethically appropriate approach. By accepting the risk of HDFN, hospitals generate obligations to promote blood donation, evaluate for alloimmunization and counsel patients on the future risk of HDFN, and maintain an understanding of the ethical rationale for RhD-positive blood transfusion.

Effect of major trauma on the expected number of births in Finnish women: A nationwide population-based public data and register analysis

BACKGROUND

The effect of major trauma on subsequent fertility is poorly described. If women have lower fertility after trauma, they would have a lower risk of anti-D mediated hemolytic disease of the fetus and newborn in a future pregnancy following the transfusion of RhD-positive blood to RhD-negative women during their resuscitation.

STUDY DESIGN AND METHODS

Data was obtained from the Care Register for Health Care, National Medical Birth Register, and open access data from Statistic Finland to evaluate the effect of major trauma (traumatic brain injuries, spine, pelvic, hip/thigh fractures) on the age-specific number of births during years 1998-2018. The total number of births before a specific maternal age for different trauma populations was calculated and these were compared to the corresponding number of births in the general population.

RESULTS

There were 50,923 injured women in this study. All injured women, including when analyzed by the nature of their injury, demonstrated lower expected numbers of births starting at approximately 28 years of age compared to the general population of women in Finland. At age 49, the expected number of births in the general population was approximately 1.8, whereas for all injured women 0.6, women with TBIs and spine fractures 0.6, women with pelvic fractures 0.5, and women with hip or thigh fractures 0.3.

DISCUSSION

Injured women are predicted to have lower fertility rates compared to the general population of Finnish women. The lower fertility rate should be considered when planning a blood product resuscitation strategy for injured women.

Low titer group O whole blood and risk of RhD alloimmunization: Rationale for use in Finland

BACKGROUND

Prehospital low-titer group O whole blood (LTOWB) used for patients with life-threatening hemorrhage is often RhD positive. The most important complication following RhD alloimmunization is hemolytic disease of the fetus and newborn (HDFN). Preceding clinical use of RhD positive LTOWB, we estimated the risk of HDFN due to LTOWB prehospital transfusion in the Finnish population.

STUDY DESIGN AND METHODS

We collected data on prehospital transfusions in Tampere and Helsinki University Hospital areas. Using the mean of reported alloimmunization rates in trauma studies (24%) and a higher reported rate representing trauma patients of 13-50 years old (42.7%), we estimated the risk of HDFN and extrapolated it to the whole of Finland.

RESULTS

We estimated that in Finland, with the current prehospital transfusion rate we would see 1-3 cases of severe HDFN due to prehospital LTOWB transfusions every 10 years, and fetal death due to HDFN caused by LTOWB transfusion less than once in 100 years.

DISCUSSION

The estimated risk of serious HDFN due to prehospital LTOWB transfusion in the Finnish population is similar to previous estimates. As Finland routinely screens expectant mothers for red blood cell antibodies and as the contemporary treatment of HDFN is very effective, we support the prehospital use of RhD positive LTOWB in all patient groups.

Maternal and child life years gained by transfusing low titer group O whole blood in trauma: A computer simulation

BACKGROUND

Using low titer group O whole blood (LTOWB) is increasingly popular for resuscitating trauma patients. LTOWB is often RhD-positive, which might cause D-alloimmunization and hemolytic disease of the fetus and newborn (HDFN) if transfused to RhD-negative females of childbearing potential (FCP). This simulation determined the number of life years gained by the FCP and her future children if she was resuscitated with LTOWB compared with conventional component therapy (CCT).

METHODS

The model simulated 500,000 injured FCPs of each age between 0 and 49 years with LTOWB mortality relative reductions (MRRs) compared with components between 0.1% and 25%. For each surviving FCP, number of life years gained was calculated using her age at injury and average life expectancy for American women. The number of expected future pregnancies for FCPs that did not survive was also based on her age at injury; each future child was assigned the maximum lifespan unless they suffered perinatal mortality or serious neurological events from HDFN.

RESULTS

The LTOWB group with an MRR 25% compared with CCT had the largest total life years gained. The point of equivalence for RhD-positive LTOWB compared to CCT, where life years lost due to severe HDFN was equivalent to life years gained due to FCP survival/future childbearing, occurred at an MRR of approximately 0.1%.

CONCLUSION

In this model, RhD-positive LTOWB resulted in substantial gains in maternal and child life years compared with CCT. A >0.1% relative mortality reduction from LTOWB offset the life years lost to HDFN mortality and severe neurological events.

Implementation of a prehospital whole blood program: Lessons learned

Early blood administration by Emergency Medical Services (EMS) to patients suffering from hemorrhagic shock improves outcomes. Prehospital blood programs represent an invaluable resuscitation capability that directly addresses hemorrhagic shock and mitigates subsequent multiple organ dysfunction syndrome. Prehospital blood programs must be thoughtfully planned, have multiple safeguards, ensure adequate training and credentialing processes, and be responsible stewards of blood resources. According to the 2022 best practices model by Yazer et al, the four key pillars of a successful prehospital program include the following: (1) the rationale for the use and a description of blood products that can be transfused in the prehospital setting, (2) storage of blood products outside the hospital blood bank and how to move them to the patient in the prehospital setting, (3) prehospital transfusion criteria and administration personnel, and (4) documentation of prehospital transfusion and handover to the hospital team.  This concepts paper describes our operational experience using these four pillars to make Maryland's inaugural prehospital ground-based low-titer O-positive whole blood program successful. These lessons learned may inform other EMS systems as they establish prehospital blood programs to help improve outcomes and enhance mass casualty response.

Use of Low-Titer O-Positive Whole Blood in Female Trauma Patients: A Literature Review, Qualitative Multidisciplinary Analysis of Risk/Benefit, and Guidelines for Its Use as a Universal Product in Hemorrhagic Shock

BACKGROUND

Whole blood transfusion is associated with benefits including improved survival, coagulopathy, and decreased transfusion requirements. The majority of whole blood transfusion is in the form of low-titer O-positive whole blood (LTOWB). Practice at many trauma centers withholds the use of LTOWB in women of childbearing potential due to concerns of alloimmunization. The purpose of this article is to review the evidence for LTOWB transfusion in female trauma patients and generate guidelines for its application.

STUDY DESIGN

Literature and evidence for LTOWB transfusion in hemorrhagic shock are reviewed. The rates of alloimmunization and subsequent obstetrical outcomes are compared to the reported outcomes of LTOWB vs other resuscitation media. Literature regarding patient experiences and preferences in regards to the risk of alloimmunization is compared to current trauma practices.

RESULTS

LTOWB has shown improved outcomes in both military and civilian settings. The overall risk of alloimmunization for Rhesus factor (Rh) - female patients in hemorrhagic shock exposed to Rh + blood is low (3% to 20%). Fetal outcomes in Rh-sensitized patients are excellent compared to historical standards, and treatment options continue to expand. The majority of female patients surveyed on the risk of alloimmunization favor receiving Rh + blood products to improve trauma outcomes. Obstetrical transfusion practices have incorporated LTOWB with excellent results.

CONCLUSIONS

The use of whole blood resuscitation in trauma is associated with benefits in the resuscitation of severely injured patients. The rate at which severely injured, Rh-negative patients develop anti-D antibodies is low. Treatments for alloimmunized pregnancies have advanced, with excellent results. Fears of alloimmunization in female patients are likely overstated and may not warrant the withholding of whole blood resuscitation. The benefits of whole blood resuscitation likely outweigh the risks of alloimmunization.

Another piece of the hemolytic disease of the fetus and newborn puzzle after RhD-positive transfusion in trauma resuscitation: the proportion of pregnant women who produce high titer anti-D

Background

After the transfusion of RhD-positive red blood cell (RBC)-containing products to an RhD-negative woman of childbearing potential (WCP) during trauma resuscitation, there are several events that must occur for that WCP to have a future pregnancy affected by hemolytic disease of the fetus and newborn (HDFN). This study identified and quantitated the frequency of a novel event in the sequence from RhD-positive transfusion during trauma resuscitation to an HDFN outcome, that is, the development of a high titer anti-D among women who were D-alloimmunized.

Methods

The transfusion service records at one maternity hospital were searched to locate all anti-D titers that had been performed on pregnant women between 1996 and 2022. The highest titer score during each pregnancy was recorded for this study. The critical titer threshold at this institution was ≥16. Passive anti-D caused by Rh immunoglobulin were excluded from analysis.

Results

There were 97 pregnancies in 85 patients who had an immune-stimulated anti-D; in 60 of 97 (62%) pregnancies, the highest titer score was ≥16. There were 12 patients who had titers performed in two pregnancies during the study period; the correlation between the maximum titer in each pregnancy was not statistically significant (Spearman rank correlation r=0.42, p=0.17).

Conclusion

In this single center study, 62% of D-alloimmunized pregnant women had a high titer antibody. When considering all of the events that must occur for HDFN to happen, the rate of perinatal mortality was calculated to be 0.04% and the rate of perinatal death or serious adverse event from HDFN was 0.24%.

Doing more with less: low-titer group O whole blood resulted in less total transfusions and an independent association with survival in adults with severe traumatic hemorrhage

BACKGROUND

Low-titer group O whole blood (LTOWB) or component therapy (CT) may be used to resuscitate hemorrhaging trauma patients. LTOWB may have clinical and logistical benefits and may improve survival.

OBJECTIVES

We hypothesized LTOWB would improve 24-hour survival in hemorrhaging patients and would be safe and equally efficacious in non-group O compared with group O patients.

METHODS

Adult trauma patients with massive transfusion protocol activations were enrolled in this observational study. The primary outcome was 24-hour mortality. Secondary outcomes included 72-hour total blood product use. A Cox regression determined the independent associations with 24-hour mortality.

RESULTS

In total, 348 patients were included (CT, n = 180; LTOWB, n = 168). Demographics were similar between cohorts. Unadjusted 24-hour mortality was reduced in LTOWB vs CT: 8% vs 19% (P = .003), but 6-hour and 28-day mortality were similar. In an adjusted analysis with multivariable Cox regression, LTOWB was independently associated with reduced 24-hour mortality (hazard ratio, 0.21; 95% CI, 0.07-0.67; P = .004). LTOWB patients received significantly less 72-hour total blood products (80.9 [41.6-139.3] mL/kg vs 48.9 [25.9-106.9] mL/kg; P < .001). In stratified 24-hour survival analyses, LTOWB was associated with improved survival for patients in shock or with coagulopathy. LTOWB use in non-group O patients was not associated with increased mortality, organ injury, or adverse events.

CONCLUSION

In this hypothesis-generating study, LTOWB use was independently associated with improved 24-hour survival, predominantly in patients with shock or coagulopathy. LTOWB also resulted in a 40% reduction in blood product use which equates to a median 2.4 L reduction in transfused products.

Not as "D"eadly as once thought - the risk of D-alloimmunization and hemolytic disease of the fetus and newborn following RhD-positive transfusion in trauma

The use of blood products to resuscitate injured and massively bleeding patients in the prehospital and early in-hospital phase of the resuscitation is increasing. Using group O red blood cells (RBC) and low titer group O whole blood (LTOWB) avoids an immediate hemolytic reaction from recipient's naturally occurring anti-A and - B, but choosing the RhD type for these products is more nuanced and requires the balancing of product availability and survival benefit against the risk of D-alloimmunization, especially in females of childbearing potential (FCP) due to the possible future occurrence of hemolytic disease of the fetus and newborn (HDFN). Recent models have estimated the risk of fetal/neonatal death from HDFN resulting from D-alloimmunization of an FCP during her trauma resuscitation at between 0-6.5% depending on her age at the time of the transfusion and other societal factors including trauma mortality, her age when she becomes pregnant, frequency of different RHD genotypes in the population, and the probability that the woman will have children with different fathers; this is counterbalanced by an approximately 24% risk of death from hemorrhagic shock. This review will discuss the different models of HDFN outcomes following RhD-positive transfusion as well as the results of recent surveys where the public was asked about their preferences for urgent transfusion in light of the risks of fetal/neonatal adverse events.

Whole Blood Administration for Obstetric-Related Hemorrhage During Prehospital Transport

BACKGROUND

Whole blood transfusion has been used for resuscitation in trauma patients; however, case reports of whole blood transfusion for obstetric-related hemorrhage are limited. Whole blood transfusion typically is accomplished with low titer O-positive whole blood, and, despite success in trauma, use in persons with childbearing potential is of concern due to risk of alloimmunization.

CASE

We present a case series of patients who received low titer O-positive whole blood for obstetric hemorrhage. One patient was Rh-negative and received immune globulin treatment after whole blood transfusion. All patients survived to hospital discharge. None experienced transfusion-related complications.

CONCLUSION

Whole blood can be successfully administered both in and out of the hospital setting, even for obstetric hemorrhage. The benefits of easily administered balanced resuscitation, limited donor exposure, and improved patient outcomes likely outweigh potential alloimmunization, especially in resource-limited settings. Addressing concerns of alloimmunization cannot be accomplished without more research, and we encourage others to investigate using whole blood in this population.

Quality improvement review of O positive blood in emergency transfusion

BACKGROUND

We recently introduced a policy to use O positive red cells in emergency transfusions for males >16 years of age and females >50 years of age. Here, we investigate changes in emergency transfusion practice and rates of red cell alloimmunization with the use of O positive blood for emergency transfusion.

STUDY DESIGN AND METHODS

State-wide retrospective review of emergency transfusions between June 2020 and June 2021. The laboratory information system and patient medical records were used to collect demographic details, indications for transfusion, usage of O positive and O negative blood and rates of alloimmunization.

RESULTS

There were 2354 red cell units transfused to 1013 patients (male = 59%, average age = 53 years) during the 12-month period. O positive units accounted for 46.9% (1103 units) of emergency transfusions. However, 726 (30.8%) O negative units were transfused to patients without a mandatory indication for O negative blood. Twenty-eight patients (2.9%) had a red cell alloantibody prior to transfusion including anti-E (n = 10), anti-D (n = 4), and anti-K (n = 4). One patient with prior anti-D had mild delayed hemolysis. There were 19 patients (4.3%, median follow-up 22 days) who developed a red cell alloantibody after emergency transfusion and include anti-E (n = 10), anti-D (n = 7), and anti-C (n = 5).

DISCUSSION

The use of O positive blood for emergency transfusion has saved 1103 O negative red cell units with no detriment to patient outcome. There remains potential to optimize use of O positive blood in emergency transfusion and to understand red cell alloimmunization rates in a prospective fashion.

Immunohematological testing and transfusion management of the prenatal patient

The primary indication for immunohematological testing in the prenatal patient is to detect and identify maternal red cell antibodies. If there are antibodies that are expected to hemolyze the fetus' red cells, their strength of reactivity must be tested, and the fetus' antigen status determined. After delivery, testing is performed to assess the extent of fetomaternal hemorrhage, as a large hemorrhage may require other therapeutic interventions. Another major role for immunohematological testing is to select blood components appropriately when intrauterine transfusion is required for fetal anemia resulting from maternal alloimmunization or some other cause. Supplementation with molecular methods has transformed the practice of immunohematology, particularly as it applies to typing for the D antigen of the Rh blood group system. Notwithstanding the advances in testing, close coordination and communication between the transfusion service and the obstetrics service are the foundation for ensuring the finest care for prenatal patients, and for new mothers and their infants. This review describes testing and transfusion practices for prenatal patients, using case presentations to highlight the management of selected immunohematological findings. It also includes a discussion of key patient management topics that are currently unresolved.

Current advances in 2022: A critical review of selected topics by the Association for the Advancement of Blood and Biotherapies (AABB) Clinical Transfusion Medicine Committee

BACKGROUND

The Association for the Advancement of Blood and Biotherapies Clinical Transfusion Medicine Committee (CTMC) composes a summary of new and important advances in transfusion medicine (TM) on an annual basis. Since 2018, this has been assembled into a manuscript and published in Transfusion.

STUDY DESIGN AND METHODS

CTMC members selected original manuscripts relevant to TM that were published electronically and/or in print during calendar year 2022. Papers were selected based on perceived importance and/or originality. References for selected papers were made available to CTMC members to provide feedback. Members were also encouraged to identify papers that may have been omitted initially. They then worked in groups of two to three to write a summary for each new publication within their broader topic. Each topic summary was then reviewed and edited by two separate committee members. The final manuscript was assembled by the first and senior authors. While this review is extensive, it is not a systematic review and some publications considered important by readers may have been excluded.

RESULTS

For calendar year 2022, summaries of key publications were assembled for the following broader topics within TM: blood component therapy; infectious diseases, blood donor testing, and collections; patient blood management; immunohematology and genomics; hemostasis; hemoglobinopathies; apheresis and cell therapy; pediatrics; and health care disparities, diversity, equity, and inclusion.

DISCUSSION

This Committee Report reviews and summarizes important publications and advances in TM published during calendar year 2022, and maybe a useful educational tool.

The females have spoken: A patient-centered national survey on the administration of emergent transfusions with the potential for future fetal harm

BACKGROUND

Traumatic hemorrhage is the leading cause of preventable death. Early in the resuscitation, only RhD-positive red blood cells are likely to be available, which poses a small risk of causing harm to a future fetus if transfused to an RhD-negative females of childbearing age (CBA), that is, 15 to 49 years old. We sought to characterize how the population, in particular females of CBA, felt about emergency blood administration vis-a-vis potential future fetal harm.

METHODS

A national survey was performed using Facebook advertisements in three waves from January 2021 to January 2022. The advertisements directed users to the survey site with seven demographic questions and four questions on accepting transfusion with differing probabilities for future fetal harm (none/any/1:100/1:10,000). Acceptance of transfusion questions were scored on 3-point Likert scale (likely/neutral/unlikely). Only completed responses by females were analyzed.

RESULTS

Advertisements were viewed 16,600,430 times by 2,169,805 people with 15,396 advertisement clicks and 2,873 surveys initiated. Most (2,256 of 2,873 [79%]) were fully completed. Majority (2,049 of 2,256 [90%]) of respondents were female. Eighty percent of females (1,645 of 2,049) were of CBA. Most females responded "likely" or "neutral" when asked whether they would accept a lifesaving transfusion if the following risk of fetal harm were present: no risk (99%), any risk (83%), 1:100 risk (85%), and 1:10,000 risk (92%). There were no differences between females of CBA versus non-CBA with respect to the likelihood of accepting lifesaving transfusion with any potential for future fetal harm ( p = 0.24).

CONCLUSION

This national survey suggests that most females would accept lifesaving transfusion even with the potential low risk of future fetal harm.

LEVEL OF EVIDENCE

Prognostic and Epidemiological; Level IV.

Resuscitative practices and the use of low-titer group O whole blood in pediatric trauma

ABSTRACT

Increasing rates of penetrating trauma in the United States makes rapid identification of hemorrhagic shock, coagulopathy, and early initiation of balanced resuscitation in injured children of critical importance. Hemorrhagic shock begins early after injury and can be challenging to identify in children, as hypotension is a late sign that a child is on the verge of circulatory collapse and should be aggressively resuscitated. Recent data support shifting away from crystalloid and toward early resuscitation with blood products because of worse coagulopathy and clinical outcomes in injured patients resuscitated with crystalloid. Multicenter studies have found improved survival in injured children who receive balanced resuscitation with higher fresh frozen plasma: red blood cell ratios. Whole blood is an efficient way to achieve balanced resuscitation in critically injured children with limited intravenous access and decreased exposure to multiple donors. Administration of cold-stored, low-titer O-negative whole blood (LTOWB) appears to be safe in adults and children and may be associated with improved survival in children with life-threatening hemorrhage. Many pediatric centers use RhD-negative LTOWB for all female children because of the risk of hemolytic disease of the fetus and newborn (0-6%); however. there is a scarcity of LTOWB compared with the demand. Low risks of hemolytic disease of the fetus and newborn affecting a future pregnancy must be weighed against high mortality rates in delayed blood product administration in children in hemorrhagic shock. Survey studies involving key stakeholder's opinions on pediatric blood transfusion practices are underway. Existing pediatric-specific literature on trauma resuscitation is often limited and underpowered; multicenter prospective studies are urgently needed to define optimal resuscitation products and practices in injured children in an era of increasing penetrating trauma.

Optimizing systems to manage postpartum hemorrhage

Systems to optimize the management of postpartum hemorrhage must ensure timely diagnosis, rapid hemodynamic and hemostatic resuscitation, and prompt interventions to control the source of bleeding. None of these objectives can be effectively completed by a single clinician, and the management of postpartum hemorrhage requires a carefully coordinated interprofessional team. This article reviews systems designed to standardize hemorrhage diagnosis and response.

Modelling the outcomes of different red blood cell transfusion strategies for the treatment of traumatic haemorrhage in the prehospital setting in the United Kingdom

BACKGROUND AND OBJECTIVES

The limited supply and increasing demand of group O RhD-negative red blood cells (RBCs) have resulted in other transfusion strategies being explored by blood services that carry potential risks but may still provide an overall benefit to patients. Our aim was to analyse the potential economic benefits of prehospital transfusion (PHT) against no PHT.

MATERIALS AND METHODS

The impact of three PHT strategies (RhD-negative RBC, RhD-positive RBC and no transfusion) on quality-adjusted-life-years (QALYs) of all United Kingdom trauma patients in a given year and the subset of patients considered most at risk (RhD-negative females <50 years old), was modelled.

RESULTS

For the entire cohort and the subset of patients, transfusing RhD-negative RBCs generated the most QALYs (141,899 and 2977, respectively), followed by the RhD-positive RBCs (141,879.8 and 2958.8 respectively), and no prehospital RBCs (119,285 and 2503 respectively). The QALY difference between RhD-negative and RhD-positive policies was smaller (19.2, both cohorts) than RhD-positive and no RBCs policies in QALYs term (22,600 all cohort, 470 for a subset), indicating that harms from transfusing RhD-positive RBCs are lower than harms associated with no RBC transfusion. A survival increase from PHT of 0.02% (entire cohort) and 0.7% (subset cohort) would still make the RhD-positive strategy better in QALYs terms than no PHT.

CONCLUSION

While the use of RhD-positive RBCs carries risks, the benefits measured in QALYs are higher than if no PHT are administered, even for women of childbearing potential. Group O RhD-positive RBCs could be considered when there is a national shortage of RhD-negative RBCs.

Attitudes of American adult women toward accepting RhD-mismatched transfusions in bleeding emergencies

BACKGROUND

There is an increasing literature demonstrating the benefits of prehospital and early in-hospital transfusions. RhD-positive products might only be available during these phases, which could pose consequences for future pregnancies if D-alloimmunization occurs. This survey measured the willingness of females to accept urgent but incompatible transfusions in light of the potential for future pregnancy complications.

METHODS

A survey was designed to assess the willingness of females ≥18 years of age to accept urgent incompatible transfusions when different absolute risk reductions in maternal mortality were presented along with a static rate of 0.3%-4.0% risk of harm to future pregnancies. The survey was sent electronically to women who are part of the Washington University Research Enhancement Core database.

RESULTS

A total of 4896 delivered survey email invitations were distributed and 325 (6.6%) responses were received; 16 responses were excluded leaving 309 responses for analysis. Most of the responding women were White, college-educated, and lived in Missouri. At least 90% of the respondents would accept an urgent incompatible transfusion when the absolute risk reduction in maternal mortality was ≥4%. Women without a college degree, who lived in Illinois, who were not able to have children appeared to be less willing than their counterparts to receive an incompatible transfusion when the absolute risk reduction in maternal mortality was low.

CONCLUSION

This survey demonstrated that adult women are highly likely to be open to accept urgent incompatible blood transfusions during a bleeding emergency when the absolute risk reduction in maternal mortality was ≥4%.

The Norwegian blood preparedness project: A whole blood program including civilian walking blood banks for early treatment of patients with life-threatening bleeding in municipal health care services, ambulance services, and rural hospitals

Background

Civilian and military guidelines recommend early balanced transfusion to patients with life‐threatening bleeding to improve survival. To provide the best care to patients with hemorrhagic shock in regions with reduced access to evacuation, blood preparedness must be ensured also on a municipal health care level. The primary aim of the Norwegian Blood Preparedness project is to enable rural hospitals, prehospital ambulance services, and municipal health care services to start early balanced blood transfusions for patients with life‐threatening bleeding regardless of etiology.

Study Design and Methods

The project is designed based on three principles: (1) Early balanced transfusion should be provided for patients with life‐threatening bleeding, (2) Management of an emergency requires a planned and rehearsed day‐to‐day system for blood preparedness, and (3) A decentralized system is needed to ensure local self‐sufficiency in an emergency. We developed a system for education and training in blood‐based resuscitation with a focus on the municipal health care service.

Results

In this publication, we describe the implementation of emergency whole blood collections from a preplanned civilian walking blood bank in the municipal health care service. This includes donor selection, whole blood collection, emergency transfusion and quality assessment of practice.

Conclusion

We conclude that implementation of a Whole Blood based emergency transfusion program is feasible on all health care levels and that a preplanned civilian walking blood bank should be considered in locations were prolonged transport‐times may reduce access to blood transfusion for patients with life threatening bleeding.

Rate of D-alloimmunization in trauma does not depend on the number of RhD-positive units transfused: The BEST collaborative study

BACKGROUND

Evidence indicates the life-saving benefits of early blood product transfusion in severe trauma resuscitation. Many of these products will be RhD-positive, so understanding the D-alloimmunization rate is important.

METHODS

This was a multicenter, retrospective study whereby injured RhD-negative patients between 18-50 years of age who received at least one unit of RhD-positive red blood cells (RBC) or low titer group O whole blood (LTOWB) during their resuscitation between 1 January, 2010 through 31 December, 2019 were identified. If an antibody detection test was performed ≥14 days after the index RhD-positive transfusion then basic demographic information was collected, including whether the patient became D-alloimmunized. The overall D-alloimmunization rate, and the rate stratified by the number of units transfused, were calculated.

RESULTS

Data were collected from nine institutions. Five institutions reported fewer than 10 eligible patients each and were excluded. From the remaining four institutions, all from the USA, there were 235 eligible patients; 77 (random effects estimate: 32.7%; 95% CI: 19.1-50.1%) became D-alloimmunized. Three of the institutions reported D-alloimmunization rates ≥38.6%, while the remaining institution's rate was 12.2%. In both random and fixed-effects models, the rate of D-alloimmunization was not significantly different between those who received one RhD-positive unit and those who received multiple RhD-positive units.

CONCLUSION

In this large, multicenter study of injured patients, the overall rate of D-alloimmunization fell within the range previously reported. The rate of D-alloimmunization did not increase as the number of transfused RhD-positive units increased. These data can help to inform RhD type selection decisions.

THOR-AABB Working Party Recommendations for a Prehospital Blood Product Transfusion Program

The evidence for the lifesaving benefits of prehospital transfusions is increasing. As such, emergency medical services (EMS) might increasingly become interested in providing this important intervention. While a few EMS and air medical agencies have been providing exclusively red blood cell (RBC) transfusions to their patients for many years, transfusing plasma in addition to the RBCs, or simply using low titer group O whole blood (LTOWB) in place of two separate components, will be a novel experience for many services. The recommendations presented in this document were created by the Trauma, Hemostasis and Oxygenation Research (THOR)-AABB (formerly known as the American Association of Blood Banks) Working Party, and they are intended to provide a framework for implementing prehospital blood transfusion programs in line with the best available evidence. These recommendations cover all aspects of such a program including storing, transporting, and transfusing blood products in the prehospital phase of hemorrhagic resuscitation.

Hemostatic Resuscitation in Children

Trauma is a major source of morbidity and mortality for children worldwide; life-threatening hemorrhage is a primary cause of preventable death. Essential interventions in children with life-threatening hemorrhage include hemostatic resuscitation and mechanical control of bleeding. Herein we review pediatric hemostatic resuscitation, a strategy that addresses both hemorrhagic shock and the coagulopathic complications described in patients with major hemorrhage. Some components of hemostatic resuscitation may include: early and aggressive resuscitation with blood products, minimizing crystalloid and hemodilution, antifibrinolytic adjuncts such as tranexamic acid, and the novel use of low-titer group O whole-blood (LTOWB) transfusion in injured children. The following selection of important publications address the current state of hemostatic resuscitation strategies in pediatric trauma patients as well as the remaining knowledge gaps and areas for further research.

Epidemiology of Massive Transfusion - A Common Intervention in Need of a Definition

While massive transfusion (MT) recipients account for a small proportion of all transfused patients, they account for approximately 10% of blood products issued. Furthermore, MT events pose organizational and logistical challenges for health care providers, laboratory and transfusion services. Overall, the majority of MT events are to support major bleeding in surgical patients, trauma and gastrointestinal hemorrhage. The clinical context in which the bleeding event occurred, the number of blood products required, patient age and comorbidities are the most important predictors of outcomes for short- and long-term survival. These data are important to inform blood services, clinicians and health care providers in order to improve care and outcomes for patients with major bleeding. There is no standard accepted definition of MT, with most definitions based on number of blood components administered within a certain time-period or activation of MT protocol. The type of definition used has implications for the clinical characteristics of MT recipients included in epidemiological and interventional studies. In order to understand trends in incidence of MT, variation in blood utilization and patient outcomes, and to harmonize research outcomes, a standard and universally accepted definition of MT is urgently required.

Survey of the RhD selection and issuing practices for uncrossmatched blood products at pediatric trauma hospitals in the United States: The BEST collaborative study

BACKGROUND

As evidence demonstrating the importance of early transfusions in trauma resuscitation accumulates, when RhD-negative products might not be available, it is important to understand the nature of the RhD-type of products provided to bleeding pediatric patients of potentially unknown RhD-type.

METHODS

A survey link was electronically sent to the transfusion service medical director and/or laboratory manager at American pediatric Level I and Level II hospitals inquiring about their practices for selecting RhD-type of uncrossmatched red blood cells (RBC) or low titer group O whole blood (LTOWB) for boys and girls.

RESULTS

There were 55/117 (47.0%) analyzable responses; 43/55 (78.2%) from Level I and 12/55 (21.8%) from Level II hospitals. For in hospital transfusions, 51/55 (92.7%) of centers use only RhD-negative blood products to resuscitate girls ≤18 years old while 30/55 (54.5%) of centers do the same for boys ≤18 years old. Most centers 41/55(74.5%) store RBCs and/or LTOWB in in-hospital remote refrigerators; 27 store only RhD-negative RBCs and 2 store only RhD-negative LTOWB units in these refrigerators. A total of 24/55 (43.6%) centers have RBCs and/or LTOWB available on road ambulances or helicopters for prehospital transfusion; 12 transport only RhD-negative RBCs and two transport only RhD-negative LTOWB. Most centers, 35/55 (63.6%), address the prophylaxis of an RhD-negative female recipient of RhD-positive transfusion on a case-by-case basis.

CONCLUSION

While there is some variability, most of the responding pediatric trauma centers routinely utilized RhD-negative RBCs for emergency transfusion for patients ≤18 years old of unknown RhD-type.

Transfusion support during mass casualty events

Transfusion support is an essential element of modern emergency healthcare. Blood services together with hospital transfusion teams are required to prepare for, and respond to, mass casualty events as part of wider healthcare emergency planning. Preparedness is a constant collaborative process that actively identifies and manages potential risks, to prevent such events becoming a 'disaster'. The aim of transfusion support during incidents is to provide sufficient and timely supply of blood components and diagnostic services, whilst maintaining support to other patients not involved in the event.

Pre-hospital transfusion of post-traumatic hemorrhage: Medical and regulatory aspects

Data of good methodological quality have recently become available to support prehospital use of transfusion in the severe trauma setting. Consistent with recent guidelines for the implementation of damage control resuscitation in the hospital in this setting and in the wake of numerous cohort study data from wartime medicine, they are now guided by recent guidelines for the use of freeze-dried plasma. The main difficulties to overcome in order to implement a practice are of a regulatory and logistic nature.

Safety profile of low-titer group O whole blood in pediatric patients with massive hemorrhage

BACKGROUND

Low-titer Group O Whole Blood (LTOWB) is used with increasing frequency in adult and pediatric trauma and massive bleeding transfusion protocols. There is a risk of acute hemolytic reactions in non-group O recipients due to the passive transfusion of anti-A and anti-B in the LTOWB. This study investigated the hemolysis risk among pediatric recipients of LTOWB.

STUDY DESIGN AND METHODS

Blood bank records were queried for pediatric recipients of LTOWB between June 2016 and August 2020 and merged with clinical data. The primary outcome was laboratory evidence of hemolysis as manifested by changes in lactate dehydrogenase (LDH), haptoglobin, total bilirubin, reticulocyte count, potassium, and creatinine. Per protocol, these values were collected on hospital days 0-2 for recipients of LTOWB. Transfusion reactions were reported to the hospital's blood bank.

RESULTS

Forty-seven children received LTOWB transfusion between 2016 and 2020; 21 were group O and 26 were non-group O. The groups were comparable in terms of the total volume of transfused blood products, demographics, and clinical outcomes. The most common indication for LTOWB transfusion was hemorrhagic shock due to trauma. There were no clinically or statistically significant differences in baseline, post-transfusion day 1, or post-transfusion day 2 hemolysis markers between the group O and non-group O LTOWB recipients. There were no adverse events or transfusion reactions reported.

DISCUSSION

Use of up to 40 ml/kg of LTOWB appears to be serologically safe for children in hemorrhagic shock.

Rate of RhD-alloimmunization after the transfusion of multiple RhD-positive primary red blood cell-containing products

INTRODUCTION

Early transfusion reduces mortality in bleeding patients. In this setting, RhD-positive blood products might be transfused. This study determined the association between the RhD-alloimmunization rate and the number of RhD-positive products transfused.

METHODS

RhD-negative patients between 13 and 50 years who were transfused with ≥1 RhD-positive red blood cell (RBC) or whole blood units between January 1, 2000 and December 31, 2019 in a healthcare network were identified. Study patients had to have had at least one antibody detection test performed ≥14 days after the index RhD-positive transfusion and not receive RhIg. Patients were stratified into groups that received 1, 2, 3-5, 6-10, 11-20, and >20 RhD-positive transfusions and the RhD-alloimmunization rate was determined for each group.

RESULTS

There were 335 patients included; 52/335 (15.5%) were females. Overall, there were 117/335 (34.9%, CI: 29.8%-40.3%) recipients who became RhD-alloimmunized. There was no significant dosage effect in the RhD-alloimmunization rates as the exposure to RhD-positive units increased from one RhD-positive unit to more than 20 RhD-positive units (p = .270 for non-parametric trend test). In an exploratory analysis, patients who received 100% of their RhD-positive transfusions within 72 h of the index transfusion had a significantly higher rate of RhD-alloimmunization compared to those who were transfused over a longer period of time (42.3% vs. 21.4%, respectively; p = .001).

CONCLUSION

These results suggest that there may not be an increased RhD-alloimmunization risk with transfusing multiple RhD-positive units after one RhD-positive unit has been transfused. These findings need confirmation in larger studies.

Anti-D alloimmunization in Rh(D) negative adults with severe traumatic injury

INTRODUCTION

Widely varying rates of alloimmunization associated with transfusing uncrossmatched RBC products to trauma patients as part of hemostatic resuscitation have been reported. We characterized the rates of RBC alloimmunization in our severely injured Rh(D) negative trauma population who received uncrossmatched Rh(D) positive RBC products.

METHODS

In a 10-year retrospective analysis to assess Rh(D) alloimmunization risks, Rh(D) negative adult trauma patients initially requiring uncrossmatched group O Rh(D) positive RBC products with either RBC units or low titer group O whole blood as part of massive transfusion protocol (MTP) activation were identified. Only those Rh(D) negative patients whose initial antibody screenings were negative were included. Duration of serologic follow-up from date of MTP activation to either date of anti-D detection or most recent negative antibody screening was calculated.

RESULTS

There were 129 eligible Rh(D) negative trauma patients identified. Median injury severity score was 25. Anti-D was detected in 10 (7.8%) patients after a median of 161.5 days; the median duration of serologic follow-up in those who did not have anti-D detected was 220 days. Patients who had anti-D detected were less severely injured and received fewer Rh(D) positive RBC products versus those who did not.

DISCUSSION

In our severely injured adult trauma patients with MTP activation requiring uncrossmatched group O Rh(D) positive RBC products, the rate of anti-D detection was low. Additional studies are necessary to determine generalizability of these findings and fully characterize alloimmunization risks in trauma patients with varying extents of injury.