A Systematic Review and Meta-analysis of Randomized Controlled Trials Comparing Intraoperative Red Blood Cell Transfusion Strategies

Adherence to a restrictive red blood cell transfusion strategy in critically ill patients: An observational study

BACKGROUND

Randomized controlled trials relatively consistently show that restrictive red blood cell (RBC) transfusion strategies are safe and associated with similar outcomes compared to liberal transfusion strategies in critically ill patients. Based on these data, the general threshold for RBC transfusion was changed to 70 g/L at a 9-bed tertiary level intensive care unit in September 2020. Implementation measures included lectures, webinars and feedback during clinical practice. The aim of this study was to investigate how implementation of a restrictive transfusion strategy influenced RBC usage, haemoglobin trigger levels and adherence to prescribed trigger levels.

METHODS

In this registry-based, observational study, critically ill adult patients without massive bleeding were included and divided into a pre-cohort, with admissions prior to the change of transfusion strategy, and a post-cohort, with admissions following the change of transfusion strategy. These cohorts were compared regarding key RBC transfusion-related variables.

RESULTS

In total 5626 admissions were included in the analyses (pre-cohort n = 4373, post-cohort n = 1253). The median volume (interquartile range, IQR) of RBC transfusions per 100 admission days, in the pre-cohort was 6120 (4110-8110) mL versus 3010 (2890-4970) mL in the post-cohort (p < .001). This corresponds to an estimated median saving of 1128 € per 100 admission days after a restrictive RBC transfusion strategy was implemented. In total, 26% of the admissions in the pre-cohort and 19% in the post-cohort (p < .001) received RBC transfusion(s) during days 0-10. Both median (IQR) prescribed trigger levels (determined by intensivist) and actual haemoglobin trigger levels (i.e., levels prior to actual administration of transfusion) were higher in the pre- versus post-cohort (90 [80-100] vs. 80 [72-90] g/L, p < .001 and 89 [82-96] g/L vs. 83 [79-94], p < .001, respectively). Percentage of days without compliance with the prescribed transfusion trigger was higher in the pre-cohort than in the post-cohort (23% vs. 14%, p < .001). Sensitivity analyses, excluding patients with traumatic brain injury, ischemic heart disease and COVID-19 demonstrated similar results.

CONCLUSIONS

Implementation of a restrictive transfusion trigger in a critical care setting resulted in lasting decreased RBC transfusion use and costs, decreased prescribed and actual haemoglobin trigger levels and improved adherence to prescribed haemoglobin trigger levels.

Nonclinical factors affecting intraoperative red blood cell transfusion: a systematic review

PURPOSE

There is significant variability in intraoperative red blood cell (RBC) transfusion practice. We aimed to use the theoretical domains framework (TDF) to categorize nonclinical and behavioural factors driving intraoperative RBC transfusion practice in a systematic review of the literature.

SOURCE

We searched electronic databases from inception until August 2021 to identify studies evaluating nonclinical factors affecting intraoperative RBC transfusion. Using the Mixed Methods Appraisal Tool, we assessed the quality of included studies and identified relevant nonclinical factors, which were coded into TDF domains by two independent reviewers using NVivo (Lumivero, QSR International, Burlington, MA, USA). We identified common themes within domains and sorted domains based on the frequency of reported factors.

PRINCIPAL FINDINGS

Our systematic review identified 18 studies: nine retrospective cohort studies, six cross-sectional surveys, and three before-and-after studies. Factors related to the social influences, behavioural regulation, environmental context/resources, and beliefs about consequences domains of the TDF were the most reported factors. Key factors underlying the observed variability in transfusion practice included the social effects of peers, patients, and institutional culture on decision-making (social influences), and characteristics of the practice environment including case volume, geographic location, and case start time (environmental context/resources). Studies reported variable beliefs about the consequences of both intraoperative transfusion and anemia (beliefs about consequences). Provider- and institutional-level audits, educational sessions, and increased communication between surgeons/anesthesiologists were identified as strategies to optimize intraoperative transfusion decision-making (behavioural regulation).

CONCLUSION

Our systematic review has synthesized the literature on nonclinical and behavioural factors impacting intraoperative transfusion decision-making, categorized using the TDF. These findings can inform evidence-based interventions to reduce intraoperative RBC transfusion variability.

STUDY REGISTRATION

Open Science Framework ( https://osf.io/pm8zs/?view_only=166299ed28964804b9360c429b1218c1 ; first posted, 3 August 2022).

Point-of-care haemoglobin accuracy and transfusion outcomes in non-cardiac surgery at a Canadian tertiary academic hospital: protocol for the PREMISE observational study

INTRODUCTION

Transfusions in surgery can be life-saving interventions, but inappropriate transfusions may lack clinical benefit and cause harm. Transfusion decision-making in surgery is complex and frequently informed by haemoglobin (Hgb) measurement in the operating room. Point-of-care testing for haemoglobin (POCT-Hgb) is increasingly relied on given its simplicity and rapid provision of results. POCT-Hgb devices lack adequate validation in the operative setting, particularly for Hgb values within the transfusion zone (60-100 g/L). This study aims to examine the accuracy of intraoperative POCT-Hgb instruments in non-cardiac surgery, and the association between POCT-Hgb measurements and transfusion decision-making.

METHODS AND ANALYSIS

PREMISE is an observational prospective method comparison study. Enrolment will occur when adult patients undergoing major non-cardiac surgery require POCT-Hgb, as determined by the treating team. Three concurrent POCT-Hgb results, considered as index tests, will be compared with a laboratory analysis of Hgb (lab-Hgb), considered the gold standard. Participants may have multiple POCT-Hgb measurements during surgery. The primary outcome is the difference in individual Hgb measurements between POCT-Hgb and lab-Hgb, primarily among measurements that are within the transfusion zone. Secondary outcomes include POCT-Hgb accuracy within the entire cohort, postoperative morbidity, mortality and transfusion rates. The sample size is 1750 POCT-Hgb measurements to obtain a minimum of 652 Hgb measurements <100 g/L, based on an estimated incidence of 38%. The sample size was calculated to fit a logistic regression model to predict instances when POCT-Hgb are inaccurate, using 4 g/L as an acceptable margin of error.

ETHICS AND DISSEMINATION

Institutional ethics approval has been obtained by the Ottawa Health Science Network-Research Ethics Board prior to initiating the study. Findings from this study will be published in peer-reviewed journals and presented at relevant scientific conferences. Social media will be leveraged to further disseminate the study results and engage with clinicians.

Intraoperative Blood Management Strategies for Patients Undergoing Noncardiac Surgery: The Ottawa Intraoperative Transfusion Consensus

Importance

There is marked variability in red blood cell (RBC) transfusion during the intraoperative period. The development and implementation of existing clinical practice guidelines have been ineffective in reducing this variability.

Objective

To develop an internationally endorsed consensus statement about intraoperative transfusion in major noncardiac surgery.

Evidence Review

A Delphi consensus survey technique with an anonymous 3-round iterative rating and feedback process was used. An expert panel of surgeons, anesthesiologists, and transfusion medicine specialists was recruited internationally. Statements were informed by extensive preparatory work, including a systematic reviews of intraoperative RBC guidelines and clinical trials, an interview study with patients to explore their perspectives about intraoperative transfusion, and interviews with physicians to understand the various behaviors that influence intraoperative transfusion decision-making. Thirty-eight statements were developed addressing (1) decision-making (interprofessional communication, clinical factors, procedural considerations, and audits), (2) restrictive transfusion strategies, (3) patient-centred considerations, and (4) research considerations (equipoise, outcomes, and protocol suspension). Panelists were asked to score statements on a 7-point Likert scale. Consensus was established with at least 75% agreement.

Findings

The 34-member expert panel (14 of 33 women [42%]) included 16 anesthesiologists, 11 surgeons, and 7 transfusion specialists; panelists had a median of 16 years' experience (range, 2-50 years), mainly in Canada (52% [17 of 33]), the US (27% [9 of 33]), and Europe (15% [5 of 33]). The panel recommended routine preoperative and intraoperative discussion between surgeons and anesthesiologists about intraoperative RBC transfusion as well as postoperative review of intraoperative transfusion events. Point-of-care hemoglobin testing devices were recommended for transfusion guidance, alongside an algorithmic transfusion protocol with a restrictive hemoglobin trigger; however, more research is needed to evaluate the use of restrictive triggers in the operating room. Expert consensus recommended a detailed preoperative consent discussion with patients of the risks and benefits of both anemia and RBC transfusion and routine disclosure of intraoperative transfusion. Postoperative morbidity and mortality were recommended as the most relevant outcomes associated with intraoperative RBC transfusion, and transfusion triggers of 70 and 90 g/L were considered acceptable hemoglobin triggers to evaluate restrictive and liberal transfusion strategies, respectively, in clinical trials.

Conclusions and Relevance

This consensus statement offers internationally endorsed expert guidance across several key domains on intraoperative RBC transfusion practice for noncardiac surgical procedures for which patients are at medium or high risk of bleeding. Future work should emphasize knowledge translation strategies to integrate these recommendations into routine clinical practice and transfusion research activities.

Determining sex-specific preoperative haemoglobin levels associated with intraoperative red blood cell transfusion in cardiac surgery: a retrospective cohort study

BACKGROUND

Anaemic cardiac surgery patients are at greater risk of intraoperative red blood cell transfusion. This study questions the application of the World Health Organization population-based anaemia thresholds (haemoglobin <120 g L-1 in non-pregnant females and <130 g L-1 in males) as appropriate preoperative optimisation targets for cardiac surgery.

METHODS

A retrospective cohort study was conducted on adults ≥18 yr old undergoing cardiopulmonary bypass surgery. Logistic regression was applied to define sex-specific preoperative haemoglobin concentrations with reduced probability of intraoperative red blood cell transfusion for cardiac surgery patients.

RESULTS

Data on 4384 male and 1676 female patients were analysed. Binarily stratified multivariable logistic regression odds of receiving intraoperative red blood cell transfusion increased in cardiac surgery patients >45 yr old (odds ratio [OR] 1.84; 95% confidence interval [CI] 1.33-2.55), surgery urgency <30 days (OR 2.03; 95% CI 1.66-2.48), combined coronary artery bypass grafting and valve surgery, or other surgery types (OR 2.24; 95% CI 1.87-2.67), and female sex (OR 1.92; 95% CI 1.62-2.28). The odds decreased by 8.4% with each 1 g L-1 increase in preoperative haemoglobin (OR 0.92; 95% CI 0.91-0.92). Logistic regression predicted females required a preoperative haemoglobin concentration of 133 g L-1 and males 127 g L-1 to have a 15% probability of intraoperative transfusion.

CONCLUSIONS

The World Health Organization female anaemia threshold of haemoglobin <120 g L-1 disproportionately disadvantages female cardiac surgery patients. A preoperative haemoglobin concentration ≥130 g L-1 in adult cardiac surgery patients would minimise their overall probability of intraoperative red blood cell transfusion to <15%.

Red Blood Cell Transfusion in Patients With Placenta Accreta Spectrum: A Systematic Review and Meta-analysis

OBJECTIVE

To evaluate red blood cell use during delivery in patients with placenta accreta spectrum.

DATA SOURCES

We searched MEDLINE, EMBASE, CINAHL, Cochrane Central, ClinicalTrials.gov, and Scopus for clinical trials and observational studies published between 2000 and 2021 in countries with developed economies.

METHODS OF STUDY SELECTION

Abstracts (n=4,275) and full-text studies (n=599) were identified and reviewed by two independent reviewers. Data on transfused red blood cells were included from studies reporting means and SDs, medians with interquartile ranges, or individual patient data. The primary outcome was the weighted mean number of units of red blood cells transfused per patient. Between-study heterogeneity was assessed with an I2 statistic. Secondary analyses included red blood cell usage by placenta accreta subtype.

TABULATION, INTEGRATION, AND RESULTS

Of the 599 full-text studies identified, 20 met criteria for inclusion in the systematic review, comprising 1,091 cases of placenta accreta spectrum. The number of units of red blood cells transfused was inconsistently described across studies, with five studies (25.0%) reporting means, 11 (55.0%) reporting medians, and four (20.0%) reporting individual patient data. The weighted mean number of units transfused was 5.19 (95% CI 4.12-6.26) per patient. Heterogeneity was high across studies (I2=91%). In a sensitivity analysis of five studies reporting mean data, the mean number of units transfused was 6.61 (95% CI 4.73-8.48; n=220 patients). Further quantification of units transfused by placenta accreta subtype was limited due to methodologic inconsistencies between studies and small cohort sizes.

CONCLUSION

Based on the upper limit of the CI in our main analysis and the high study heterogeneity, we recommend that a minimum of 6 units of red blood cells be available before delivery for patients with placenta accreta spectrum. These findings may inform future guidelines for predelivery blood ordering and transfusion support.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO, CRD42021240993.

Generating real-world evidence compatible with evidence from randomized controlled trials: a novel observational study design applicable to surgical transfusion research

BACKGROUND

Numerous observational studies have revealed an increased risk of death and complications with transfusion, but this observation has not been confirmed in randomized controlled trials (RCTs). The "transfusion kills patients" paradox persists in real-world observational studies despite application of analytic methods such as propensity-score matching. We propose a new design to address this long-term existing issue, which if left unresolved, will be deleterious to the healthy generation of evidence that supports optimized transfusion practice.

METHODS

In the new design, we stress three aspects for reconciling observational studies and RCTs on transfusion safety: (1) re-definition of the study population according to a stable hemoglobin range (gray zone of transfusion decision; 7.5-9.5 g/dL in this study); (2) selection of comparison groups according to a trigger value (last hemoglobin measurement before transfusion; nadir during hospital stay for control); (3) dealing with patient heterogeneity according to standardized mean difference (SMD) values. We applied the new design to hospitalized older patients (aged ≥60 years) undergoing general surgery at four academic/teaching hospitals. Four datasets were analyzed: a base population before (Base Match-) and after (Base Match+) propensity-score matching to simulate previous observational studies; a study population before (Study Match-) and after (Study Match+) propensity-score matching to demonstrate effects of our design.

RESULTS

Of 6141 older patients, 662 (10.78%) were transfused and showed high heterogeneity compared with those not receiving transfusion, particularly regarding preoperative hemoglobin (mean: 11.0 vs. 13.5 g/dL) and intraoperative bleeding (≥500 mL: 37.9% vs. 2.1%). Patient heterogeneity was reduced with the new design; SMD of the two variables was reduced from approximately 100% (Base Match-) to 0% (Study Match+). Transfusion was related to a higher risk of death and complications in Base Match- (odds ratio [OR], 95% confidence interval [CI]: 2.68, 1.86-3.86) and Base Match+ (2.24, 1.43-3.49), but not in Study Match- (0.77, 0.32-1.86) or Study Match+ (0.66, 0.23-1.89).

CONCLUSIONS

We show how choice of study population and analysis could affect real-world study findings. Our results following the new design are in accordance with relevant RCTs, highlighting its value in accelerating the pace of transfusion evidence generation and generalization.