Restrictive or Liberal Transfusion Strategy in Myocardial Infarction and Anemia

Year in Review 2023: Noteworthy Literature in Cardiothoracic Critical Care

This article reviews noteworthy investigations and society recommendations published in 2023 relevant to the care of critically ill cardiothoracic surgical patients. We reviewed 3,214 articles to identify 18 publications that add to the existing literature across a variety of topics including resuscitation, nutrition, antibiotic management, extracorporeal membrane oxygenation (ECMO), neurologic care following cardiac arrest, coagulopathy and transfusion, steroids in pulmonary infections, and updated guidelines in the management of acute respiratory distress syndrome (ARDS).

Year in Review 2023: Noteworthy Literature in Cardiac Anesthesiology

Notable clinical research published in 2023 related to cardiac anesthesia included studies focused on resuscitation and pharmacology, regional anesthesia, technological advances, and novel gene therapies. We reviewed 241 articles to identify 25 noteworthy studies that represent the most significant research related to cardiac anesthesia from the past year. Overall, improvements in clinical practice have enabled decreased morbidity and mortality with a renewed focus on mechanical circulatory support and transplantation.

Advances in Clinical Cardiology 2023: A Summary of Key Clinical Trials

INTRODUCTION

Over the course of 2023, numerous key clinical trials with valuable contributions to clinical cardiology were published or presented at major international conferences. This review seeks to summarise these trials and reflect on their clinical context.

METHODS

The authors collated and reviewed clinical trials presented at major cardiology conferences during 2023 including the American College of Cardiology (ACC), European Association for Percutaneous Cardiovascular Interventions (EuroPCR), European Society of Cardiology (ESC), Transcatheter Cardiovascular Therapeutics (TCT), American Heart Association (AHA), European Heart Rhythm Association (EHRA), Society for Cardiovascular Angiography and Interventions (SCAI), TVT-The Heart Summit (TVT) and Cardiovascular Research Technologies (CRT). Trials with a broad relevance to the cardiology community and those with potential to change current practice were included.

RESULTS

A total of 80 key cardiology clinical trials were identified for inclusion. Key trials in acute coronary syndrome (ACS) and antiplatelet management such as HOST-IDEA, T-PASS and STOP-DAPT3 were included in addition to several pivotal interventional trials such as ORBITA 2, MULTISTARS-AMI, ILUMIEN-IV, OCTIVUS and OCTOBER. Additionally, several trials evaluated new stent design and technology such as BIOSTEMI, PARTHENOPE and TRANSFORM. Structural intervention trials included long-term data from PARTNER 3, new data on the durability of transcatheter aortic valve intervention (TAVI), in addition to major new trials regarding transcatheter tricuspid valve intervention from TRISCEND II. Heart failure (HF) and prevention covered several key studies including DAPA-MI, STEP-HF, ADVOR, DICTATE HF and CAMEO-DAPA. In cardiac devices and electrophysiology, several trial exploring novel ablation strategies in atrial fibrillation (AF) such as PULSED AF and ADVENT were presented with further data evaluating the efficacy of anticoagulation in subclinical AF in NOAH-AFNET 6, FRAIL AF and AZALEA-TIMI 71.

CONCLUSION

This article presents a summary of key clinical cardiology trials published and presented during the past year and should be of interest to both practising clinicians and researchers.

Leading digit bias in hemoglobin thresholds for red cell transfusion

BACKGROUND

Leading digit bias is a heuristic whereby humans overemphasize the left-most digit when evaluating numbers (e.g., 9.99 vs. 10.00). The bias might affect the interpretation of hemoglobin results and influence red cell transfusion in hospitalized patients.

STUDY DESIGN AND METHODS

Adults who received a red cell transfusion while registered at the University Health Network (Toronto, Canada) between January 1, 2016 and January 1, 2022 (n = 6 years) were included. The primary analysis excluded apheresis, red cell disorders, radiology suites, and operating rooms. The primary comparison was a regression discontinuity analysis of transfusion occurrence above and below the hemoglobin threshold of 79 g/L (local units). Additional analyses tested other leading digit and control thresholds (71, 81, and 91 g/L). Secondary analyses explored temporal covariates and clinical subgroups.

RESULTS

A total of 211,872 red cell transfusions were identified over the study period (median pre-transfusion hemoglobin 76 g/L; interquartile range = 69-92 g/L), with 107,790 inpatient transfusions in the primary analysis. The 79 g/L threshold showed 815 fewer red cell units above the threshold (95% confidence interval [CI]: -1215 to -415). The 69 g/L threshold showed 2813 fewer transfused units (95% CI: -4407 to -1220), and 89 g/L showed 40 fewer units (95% CI: -408 to 328). The effect was accentuated during daytime, weekday, and May-June months, persisted in analyses including all transfusions, and was absent at control thresholds.

CONCLUSION

Leading digit bias might have a modest influence on the decision to transfuse red cells. The findings may inform practice guidelines and quasi-experimental study design in transfusion research.

Efficacy and safety of restrictive versus liberal blood transfusion strategies in acute myocardial infarction and anemia: a systematic review and meta-analysis of randomized controlled trials

BACKGROUND

Blood transfusion strategies in patients with acute myocardial infarction (AMI) and anemia are yet to be conclusively identified. Thus, we aim to assess the efficacy and safety of restrictive versus liberal blood transfusion strategies for AMI and anemia.

METHODS

A systematic review and meta-analysis of randomized controlled trials (RCTs) retrieved from PubMed, web of science, SCOPUS, EMBASE, and Cochrane Central Register of Controlled Trials were performed through November 2023. We used RevMan V. 5.4 to pool dichotomous data using risk ratio (RR) and continuous data using mean difference (MD) with a 95% confidence interval (CI). (PROSPERO): ID: CRD42023490692.

RESULTS

We included four RCTs with 4.325 patients. There was no significant difference between both groups regarding MACE whether at 30 days (RR: 0.93 with 95% CI [0.57-1.51], P  = 0.76) or ≥ six months (RR: 1.17 with 95% CI [0.95-1.45], P  = 0.14), all-cause mortality at 30 days (RR: 1.16 with 95% CI [0.95-1.40], P  = 0.14) or ≥ six months (RR: 1.16 with 95% CI [0.88-1.53], P  = 0.28). However, the liberal strategy was significantly associated with increased hemoglobin level change (MD: -1.44 with 95% CI [-1.68 to -1.20], P  < 0.00001). However, the restrictive strategy was significantly associated with a lower incidence of acute lung injury (RR: 0.11 with 95% CI [0.02-0.60], P  = 0.01).

CONCLUSION

There was no significant difference between the restrictive blood transfusion strategy and the liberal blood transfusion strategy regarding the clinical outcomes. However, restrictive blood transfusion strategy was significantly associated with a lower incidence of acute lung injury than liberal blood transfusion strategy.

A novel measure to summarize blood transfusion practice during critical illness

BACKGROUND

Large-scale observational studies have summarized transfusion practice using traditional measures of central tendency (e.g., the mean hemoglobin concentration at the time of transfusion). However, the mean hemoglobin concentration fails to identify specific hemoglobin concentration thresholds that drive practice. In the following brief report, we propose a novel measure of "practice discontinuity" that identifies specific practice-defining hemoglobin thresholds.

STUDY DESIGN AND METHODS

We used the PINC AI Database (2016-2022) to identify adult patients admitted to an intensive care unit with at least one hemoglobin concentration measurement. For each day that hemoglobin was measured, we identified whether the patient received a red blood cell transfusion using hospital charge codes. We defined the "practice discontinuity" measure as the hemoglobin concentration at which there was the largest increase in transfusion use going from a higher to an incrementally lower hemoglobin concentration. We also calculated the mean and median pretransfusion hemoglobin concentrations.

RESULTS

We identified 1,298,367 patients and 4,905,839 patient-days for inclusion. RBC transfusion occurred in a total of 530,654 (10.8%) patient-days. The overall pre-transfusion mean and median hemoglobin concentrations were 8.4 and 8.0 g/dL, respectively. The practice discontinuity measure identified 7.0 g/dL as the hemoglobin concentration at which transfusion use increased the most, from 46.6% of patient-days at a concentration of 7.0 g/dL to 74.8% of patient-days at a concentration of 6.9 g/dL.

DISCUSSION

We propose that future studies of red blood cell transfusion practice consider inclusion of the practice discontinuity measure to more fully summarize clinical practice.

Type 2 Myocardial Infarction-Poorly Understood, Underevaluated, and Too Often Ignored

This Viewpoint discusses diagnosis of type 2 myocardial infarction.

Emergency medicine updates: Lower gastrointestinal bleeding

INTRODUCTION

Lower gastrointestinal bleeding (LGIB) is a condition commonly seen in the emergency department. Therefore, it is important for emergency medicine clinicians to be aware of the current evidence regarding the diagnosis and management of this disease.

OBJECTIVE

This paper evaluates key evidence-based updates concerning LGIB for the emergency clinician.

DISCUSSION

LGIB is most commonly due to diverticulosis or anorectal disease, though there are a variety of etiologies. The majority of cases resolve spontaneously, but patients can have severe bleeding resulting in hemodynamic instability. Initial evaluation should focus on patient hemodynamics, the severity of bleeding, and differentiating upper gastrointestinal bleeding from LGIB. Factors associated with LGIB include prior history of LGIB, age over 50 years, and presence of blood clots per rectum. Computed tomography angiography is the imaging modality of choice in those with severe bleeding to diagnose the source of bleeding and guide management when embolization is indicated. Among stable patients without severe bleeding, colonoscopy is the recommended modality for diagnosis and management. A transfusion threshold of 7 g/dL hemoglobin is recommended based on recent data and guidelines (8 g/dL in those with myocardial ischemia), though patients with severe bleeding and hemodynamic instability should undergo emergent transfusion. Anticoagulation reversal may be necessary. If bleeding does not resolve, embolization or endoscopic therapies are necessary. There are several risk scores that can predict the risk of adverse outcomes; however, these scores should not replace clinical judgment in determining patient disposition.

CONCLUSIONS

An understanding of literature updates can improve the care of patients with LGIB.

A Novel Digital Twin Strategy to Examine the Implications of Randomized Control Trials for Real-World Populations

Randomized clinical trials (RCTs) are essential to guide medical practice; however, their generalizability to a given population is often uncertain. We developed a statistically informed Generative Adversarial Network (GAN) model, RCT-Twin-GAN, that leverages relationships between covariates and outcomes and generates a digital twin of an RCT (RCT-Twin) conditioned on covariate distributions from a second patient population. We used RCT-Twin-GAN to reproduce treatment effect outcomes of the Systolic Blood Pressure Intervention Trial (SPRINT) and the Action to Control Cardiovascular Risk in Diabetes (ACCORD) Blood Pressure Trial, which tested the same intervention but had different treatment effect results. To demonstrate treatment effect estimates of each RCT conditioned on the other RCT patient population, we evaluated the cardiovascular event-free survival of SPRINT digital twins conditioned on the ACCORD cohort and vice versa (SPRINT-conditioned ACCORD twins). The conditioned digital twins were balanced by the intervention arm (mean absolute standardized mean difference (MASMD) of covariates between treatment arms 0.019 (SD 0.018), and the conditioned covariates of the SPRINT-Twin on ACCORD were more similar to ACCORD than a sprint (MASMD 0.0082 SD 0.016 vs. 0.46 SD 0.20). Most importantly, across iterations, SPRINT conditioned ACCORD-Twin datasets reproduced the overall non-significant effect size seen in ACCORD (5-year cardiovascular outcome hazard ratio (95% confidence interval) of 0.88 (0.73-1.06) in ACCORD vs median 0.87 (0.68-1.13) in the SPRINT conditioned ACCORD-Twin), while the ACCORD conditioned SPRINT-Twins reproduced the significant effect size seen in SPRINT (0.75 (0.64-0.89) vs median 0.79 (0.72-0.86)) in ACCORD conditioned SPRINT-Twin). Finally, we describe the translation of this approach to real-world populations by conditioning the trials on an electronic health record population. Therefore, RCT-Twin-GAN simulates the direct translation of RCT-derived treatment effects across various patient populations with varying covariate distributions.

Hemoglobin in large vessel occlusion: Look further than collaterals

BACKGROUND

Abnormal hemoglobin (Hb) levels lead to poorer outcomes in ischemic stroke, though the mechanisms remain elusive. We aimed to study the role of Hb on imaging and clinical outcomes, namely on collaterals as it is a known mediator of infarct growth.

METHODS

Retrospective cohort study of patients with large vessel occlusion ischemic stroke admitted to our center. Demographics, clinical and imaging variables were collected, particularly baseline hemoglobin, presence of anemia and collateral score. Collaterals were scored from 0 to 3 and defined as poor if 0-1. Multivariable analyses were performed for collateral score and clinical outcomes (3-month mortality and good prognosis).

RESULTS

We included 811 patients, 215 (26.5 %) with anemia. Patients with anemia were older, had more comorbidities and more severe strokes. Hemoglobin levels and anemia were not associated with collateral score (OR 0.97, 95 % CI 0.89-1.05, p = 0.414 and OR 0.89, 95 % CI 0.64-1.24, p = 0.487, respectively) nor with poor collaterals (OR 0.96, 95 % CI 0.88-1.05, p = 0.398 and OR 0.86, 95 % CI 0.60-1.23, p = 0.406, respectively). Hb levels were associated with 3-month mortality (OR 0.85, 95 % CI 0.76-0.96, p = 0.008).

CONCLUSION

Hemoglobin or anemia were not found to be associated with collateral status. Our results raise further questions regarding the pathophysiology of anemia and outcomes in ischemic stroke, highlighting the need for future research.

Restrictive vs Liberal Blood Transfusions for Patients with Acute Myocardial Infarction and Anaemia by Heart Failure Status: An RCT Subgroup Analysis

BACKGROUND

Red blood cell transfusion can cause fluid overload. We evaluated the interaction between heart failure (HF) at baseline and transfusion strategy on outcomes in acute myocardial infarction (AMI).

METHODS

We used data from the randomized REALITY trial (https://www.

CLINICALTRIALS

gov/study/NCT02648113), comparing restrictive versus liberal transfusion strategies in patients with AMI and anaemia. HF was defined as history of HF or Killip class > 1 at randomization. Primary outcome was major adverse cardiovascular events (MACE: composite of all-cause death, non-recurrent AMI, stroke, or emergency revascularization prompted by ischaemia) at 30 days.

RESULTS

Among 658 randomized patients, 311 (47.3%) had HF. HF patients had higher rates of MACE at 30 days and 1 year, and higher rates of non-fatal new-onset HF. There was no interaction between HF and effect of randomized assignment on the primary outcome or non-fatal new-onset HF. A liberal transfusion strategy was associated with increased all-cause death at 30 days and at 1 year in HF patients (Pinteraction = 0.009 and P = 0.049, respectively). The main numerical difference in cause of death between restrictive and liberal strategies was death by HF at 30 days (4 vs 11).

CONCLUSIONS

HF is frequent in AMI patients with anaemia and is associated with higher risk of MACE (including all-cause death) and non-fatal new-onset HF. While there was no interaction of HF with effect of transfusion strategy on MACE, a liberal transfusion strategy was associated with higher all-cause death that appears driven by a higher risk of early death due to HF.

Alternative blood transfusion triggers: a narrative review

BACKGROUND

Anemia, characterized by low hemoglobin levels, is a global public health concern. Anemia is an independent factor worsening outcomes in various patient groups. Blood transfusion has been the traditional treatment for anemia; its triggers, primarily based on hemoglobin levels; however, hemoglobin level is not always an ideal trigger for blood transfusion. Additionally, blood transfusion worsens clinical outcomes in certain patient groups. This narrative review explores alternative triggers for red blood cell transfusion and their physiological basis.

MAIN TEXT

The review delves into the physiology of oxygen transport and highlights the limitations of using hemoglobin levels alone as transfusion trigger. The main aim of blood transfusion is to optimize oxygen delivery, necessitating an individualized approach based on clinical signs of anemia and the balance between oxygen delivery and consumption, reflected by the oxygen extraction rate. The narrative review covers different alternative triggers. It presents insights into their diagnostic value and clinical applications, emphasizing the need for personalized transfusion strategies.

CONCLUSION

Anemia and blood transfusion are significant factors affecting patient outcomes. While restrictive transfusion strategies are widely recommended, they may not account for the nuances of specific patient populations. The search for alternative transfusion triggers is essential to tailor transfusion therapy effectively, especially in patients with comorbidities or unique clinical profiles. Investigating alternative triggers not only enhances patient care by identifying more precise indicators but also minimizes transfusion-related risks, optimizes blood product utilization, and ensures availability when needed. Personalized transfusion strategies based on alternative triggers hold the potential to improve outcomes in various clinical scenarios, addressing anemia's complex challenges in healthcare. Further research and evidence are needed to refine these alternative triggers and guide their implementation in clinical practice.