Restrictive versus liberal red blood cell transfusion for cardiac surgery: a systematic review and meta-analysis of randomized controlled trials

What drives variability in postoperative cardiac surgery transfusion rates?

OBJECTIVE

Wide interhospital variation exists in cardiac surgical postoperative transfusion rates. We aimed to compare transfusion rates at 2 hospitals and identify the institutional practice factors, unrelated to patient or operative characteristics, associated with postoperative transfusion rates.

METHODS

Records for adult patients undergoing routine cardiac surgery at 2 hospitals (H and L) from February 2020 to August 2022 were analyzed. Patient and operative characteristics, preoperative and intensive care unit hemoglobin values, and postoperative transfusion rates were compared. Transfusion indication was recorded prospectively. Propensity matching was completed to assess comparability of patient populations.

RESULTS

After propensity matching patients at H and L on age, procedure type, predicted morbidity or mortality, crossclamp time, preoperative hypertension, preoperative heart failure, and preoperative stroke, 2111 patients remained, with similar characteristics except hypertension. Matched results showed no significant differences in mortality, reoperation, or other major outcomes. Hospital H transfused 36% of patients (mean postoperative hemoglobin [Hb] 10.5) with 1483 units of packed red blood cells whereas hospital L transfused 12% of patients (mean postoperative Hb 9.4) with 198 units of packed red blood cells (P < .001). For all patients with a Hb >7.5, hospital H versus L transfused 27% versus 0.9% (P < .001). Hospital L's sole transfusion indication for pretransfusion hemoglobin trigger >7.5 was bleeding versus hospital H, which had multiple indications. When Hb concentration alone was the indication for transfusion, the threshold at hospital H was <7.5 g/dL versus <6 g/dL at hospital L.

CONCLUSIONS

Variation in transfusion rates between hospitals H and L resulted from strict adherence at hospital L to a transfusion trigger of <6 g/dL with narrow indications for transfusions above that Hb concentration.

Prevention of cardiac surgery-associated acute kidney injury: a systematic review and meta-analysis of non-pharmacological interventions

BACKGROUND

Cardiac surgery-associated acute kidney injury (CSA-AKI) is frequent. While two network meta-analyses assessed the impact of pharmacological interventions to prevent CSA-AKI, none focused on non-pharmacological interventions. We aim to assess the effectiveness of non-pharmacological interventions to reduce the incidence of CSA-AKI.

METHODS

We searched PubMed, Embase, Central and clinical trial registries from January 1, 2004 (first consensus definition of AKI) to July 1, 2023. Additionally, we conducted manual screening of abstracts of major anesthesia and intensive care conferences over the last 5 years and reference lists of relevant studies. We selected all randomized controlled trials (RCTs) assessing a non-pharmacological intervention to reduce the incidence of CSA-AKI, without language restriction. We excluded RCTs of heart transplantation or involving a pediatric population. The primary outcome variable was CSA-AKI. Two reviewers independently identified trials, extracted data and assessed risk of bias. Random-effects meta-analyses were conducted to calculate risk ratios (RRs) with 95% confidence intervals (CIs). We used the Grading of Recommendations Assessment, Development, and Evaluation to assess the quality of evidence.

RESULTS

We included 86 trials (25,855 patients) evaluating 10 non-pharmacological interventions to reduce the incidence of CSA-AKI. No intervention had high-quality evidence to reduce CSA-AKI. Two interventions were associated with a significant reduction in CSA-AKI incidence, with moderate quality of evidence: goal-directed perfusion (RR, 0.55 [95% CI 0.40-0.76], I2 = 0%; Phet = 0.44) and remote ischemic preconditioning (RR, 0.86 [0.78-0.95]; I2 = 23%; Phet = 0.07). Pulsatile flow during cardiopulmonary bypass was associated with a significant reduction in CSA-AKI incidence but with very low quality of evidence (RR = 0.69 [0.48; 0.99]; I2 = 53%; Phet < 0.01). We found high quality of evidence for lack of effect of restrictive transfusion strategy (RR, 1.02 [95% CI 0.92; 1.12; Phet = 0.67; I2 = 3%) and tight glycemic control (RR, 0.86 [95% CI 0.55; 1.35]; Phet = 0.25; I2 = 26%).

CONCLUSIONS

Two non-pharmacological interventions are likely to reduce CSA-AKI incidence, with moderate quality of evidence: goal-directed perfusion and remote ischemic preconditioning.

Overtransfusion of packed red blood cells during massive transfusion activation: a potential quality metric for trauma resuscitation

Objectives

The goal of this study was to explore the incidence of overtransfusion in trauma patients requiring massive transfusion protocol (MTP) activation and identify modifiable risk factors. We hypothesized that overtransfusion is common after MTP activation.

Methods

Patients admitted to a level I trauma center from July 2016 to December 2019 and who required MTP activation were selected. The primary outcome was overtransfusion, defined as a hemoglobin (Hg) ≥11 g/dL at 24 hours (±2 hours). A Cox regression model was used to identify independent risk factors for overtransfusion.

Results

140 patients met inclusion criteria. The median age was 39.0 years, with the majority (74.3%) being male. The median (IQR) Injury Severity Score (ISS) was 24.0 (58.0) and 38.4% had a penetrating mechanism. The median (IQR) admission Hg was 12.6 (11.7) g/dL. Overall, 71.4% of patients were overtransfused by the conclusion of MTP, 43.6% 24 hours later, and 29.5% at discharge. Overtransfusion did not correlate with the number of units of blood transfused nor with the duration of MTP. Overtransfused patients at 24 hours after the conclusion of MTP were significantly more likely to present with a penetrating injury (52.5% vs. 27.3%, p=0.003) and have a significantly lower ISS (median (IQR) 18.5 (44.0) vs. 26.0 (58.0), p=0.035.) In a Cox regression model, penetrating mechanism (adjusted HR (AHR): 2.93; adjusted p=0.004) and admission base excess (BE) (AHR: 1.15; adjusted p=0.001) were the only variables independently associated with overtransfusion.

Conclusions

Overtransfusion of trauma patients requiring MTP activation is highly common, leading to overutilization of a limited resource. Penetrating trauma and BE may be modifiable risk factors that can help limit overtransfusion. Overtransfusion should be tracked as a data point by blood banks and trauma centers and be further studied as a potential quality metric for the resuscitation of massively transfused trauma patients.

Level of evidence

III.

Impact of restrictive red blood cell transfusion strategy on thrombosis-related events: A meta-analysis and systematic review

BACKGROUND AND OBJECTIVES

There is an ongoing controversy regarding the risks of restrictive and liberal red blood cell (RBC) transfusion strategies. This meta-analysis assessed whether transfusion at a lower threshold was superior to transfusion at a higher threshold, with regard to thrombosis-related events, that is, whether these outcomes can benefit from a restrictive transfusion strategy is debated.

MATERIALS AND METHODS

We searched PubMed, Cochrane Central Register of Controlled Trials and Scopus from inception up to 31 July 2021. We included randomized controlled trials (RCTs) in any clinical setting that evaluated the effects of restrictive versus liberal RBC transfusion in adults. We used random-effects models to calculate the risk ratios (RRs) and 95% confidence intervals (CIs) based on pooled data.

RESULTS

Thirty RCTs involving 17,334 participants were included. The pooled RR for thromboembolic events was 0.65 (95% CI 0.44-0.94; p = 0.020; I²  = 0.0%, very low-quality evidence), favouring the restrictive strategy. There were no significant differences in cerebrovascular accidents (RR = 0.83; 95% CI 0.64-1.09; p = 0.180; I²  = 0.0%, very low-quality evidence) or myocardial infarction (RR = 1.05; 95% CI 0.87-1.26; p = 0.620; I²  = 0.0%, low-quality evidence). Subgroup analyses showed that a restrictive (relative to liberal) strategy reduced (1) thromboembolic events in RCTs conducted in North America and (2) myocardial infarctions in the subgroup of RCTs where the restrictive transfusion threshold was 7 g/dl but not in the 8 g/dl subgroup (with a liberal transfusion threshold of 10 g/dl in both subgroups).

CONCLUSIONS

A restrictive (relative to liberal) transfusion strategy may be effective in reducing venous thrombosis but not arterial thrombosis.

Platelet Toll-like Receptor 4–Related Innate Immunity Potentially Participates in Transfusion Reactions Independent of ABO Compatibility: An Ex Vivo Study

The role of platelet TLR4 in transfusion reactions remains unclear. This study analyzed platelet TLR4 and certain damage-associated molecular patterns (DAMPs) and evaluated how ABO compatibility affected TLR4 expression after a simulated ex vivo transfusion. A blood bank was the source of donor red blood cells. Blood from patients undergoing cardiac surgery was processed to generate a washed platelet suspension to which the donor blood was added in concentrations 1, 5, and 10% (v/v). Blood-mixing experiments were performed on four groups: a 0.9% saline control group (n = 31); a matched-blood-type mixing group (group M, n = 20); an uncross-matched ABO-specific mixing group (group S, n = 20); and an ABO-incompatible blood mixing group (group I, n = 20). TLR4 expression in the platelets was determined after blood mixing. We evaluated levels of TLR4-binding DAMPs (HMGB1, S100A8, S100A9, and SAA), lipopolysaccharide-binding protein, and endpoint proteins in the TLR4 signaling pathway. In the M, S, and I groups, 1, 5, and 10% blood mixtures significantly increased TLR4 expression (all p < 0.001) in a concentration-dependent manner. Groups M, S, and I were not discovered to have significantly differing TLR4 expression (p = 0.148). HMGB1, S100A8, and S100A9 levels were elevated in response to blood mixing, but SAA, lipopolysaccharide-binding protein, TNF-α, IL-1β, and IL-6 levels were not. Blood mixing may elicit innate immune responses by upregulating platelet TLR4 and DAMPs unassociated with ABO compatibility, suggesting that innate immunity through TLR4-mediated signaling may induce transfusion reactions.

Number and Type of Blood Products are Negatively Associated With Outcomes Following Cardiac Surgery

BACKGROUND

The association between blood transfusion and adverse outcome is documented in cardiac surgery. However, the incremental significance of each unit transfused, whether red blood cell (RBC) or non-RBC, is uncertain. This study examined the relationship of patient outcomes with type and number of blood product units transfused.

METHODS

Statewide data from adult cardiac surgery patients were included (N=24,082). Relationship with blood transfusion was assessed for morbidity and 30-day mortality using total number of RBC and non-RBC units transfused, specific type of non-RBC units, and different combinations of transfusion (only RBC, only non-RBC, RBC+non-RBC). Multivariable logistic regressions examined these associations.

RESULTS

Median age was 66 years (30% female) with 51% of patients transfused (31%-66% across hospitals). Risk-adjusted analyses found each blood product unit associated with 9%, 7%, and 4% greater odds for 30-day mortality, major morbidity, and minor morbidity (all P<0.001). Odds for 30-day mortality were 13% greater with each RBC unit (P<0.001) and 6% greater for each non-RBC unit (P<0.001). Each unit of fresh frozen plasma (P<0.001) and platelets (P<0.001) increased odds for 30-day mortality, but no effect for cryoprecipitate (P=0.725). Odds for 30-day mortality were lower for non-RBC only (OR=0.52, P=0.030) and greater for RBC+non-RBC (OR=2.98, P<0.001) compared to RBC only transfusion.

CONCLUSIONS

Independent of center variability on transfusion methods, each additional unit transfused was associated with increased odds for complications, with RBC transfusion carrying greater risk compared to non-RBC. Comprehensive evidence-based clinical approaches and coordination are needed to guide each blood transfusion event following cardiac surgery.

Effect of Blood Product Transfusion on Perioperative Outcomes After Heart Transplantation

OBJECTIVE(S)

The objective of this study was to identify transfusion-related in-hospital outcomes in orthotopic heart transplantation (OHT) recipients.

DESIGN

Retrospective chart review.

SETTING

Tertiary care hospital.

PARTICIPANTS

Adult OHT recipients undergoing transplantation between January 2010 and December 2016.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

The primary composite outcome was occurrence of any of the following events during admission for OHT: (1) graft dysfunction requiring mechanical circulatory support (MCS); (2) respiratory failure requiring tracheostomy; (3) renal failure requiring hemodialysis; (4) 30-day mortality; (5) complication requiring readmission to intensive care unit; (6) sepsis; and (7) stroke. The authors evaluated these outcomes in relation to all blood component transfusions received intraoperatively and in the first 24 hours postoperatively. The study included 197 patients and the primary composite outcome was present in 72 (36.6%). After adjusting for propensity score, red blood cell (RBC) transfusion was associated with composite outcomes (odds ratio [OR] 1.17, 95% confidence interval [CI] 1.05-1.31, p = 0.004), postoperative MCS use (OR 1.36, 95% CI 1.18-1.58, p < 0.001), acute renal failure requiring hemodialysis (OR 1.21, 5% CI 1.06-1.38, p = 0.004), and 30-day mortality (OR 1.29, 95% CI 1.05-1.59, p = 0.02). Fresh frozen plasma was associated with composite outcome (OR 1.07, 95% CI [1.003-1.15], p = 0.042) and renal failure (OR 1.08, 95% CI 1.08 [1.002-1.17], p = 0.04).

CONCLUSIONS

Intra- and postoperative transfusions (first 24 hours) of RBC and FFP were associated with adverse postoperative composite outcomes in patients undergoing OHT.

The Year in Cardiothoracic Critical Care: Selected Highlights from 2019

In 2019, cardiothoracic and vascular critical care remained an important focus and subspecialty. This article continues the annual series to review relevant contributions in postoperative critical care that may affect the cardiac anesthesiologist. Herein, the pertinent literature published in 2019 is explored and organized by organ system.

Systematic reviews and meta-analyses comparing mortality in restrictive and liberal haemoglobin thresholds for red cell transfusion: an overview of systematic reviews

BACKGROUND

There are no overviews of systematic reviews investigating haemoglobin thresholds for transfusion. This is important as the literature on transfusion thresholds has grown considerably in recent years. Our aim was to synthesise evidence from systematic reviews and meta-analyses of the effects of restrictive and liberal transfusion strategies on mortality.

METHODS

This was a systematic review of systematic reviews (overview). We searched MEDLINE, Embase, Web of Science Core Collection, PubMed, Google Scholar, and the Joanna Briggs Institute EBP Database, from 2008 to 2018. We included systematic reviews and meta-analyses of randomised controlled trials comparing mortality in patients assigned to red cell transfusion strategies based on haemoglobin thresholds. Two independent reviewers extracted data and assessed methodological quality. We assessed the methodological quality of included reviews using AMSTAR 2 and the quality of evidence pooled using an algorithm to assign GRADE levels.

RESULTS

We included 19 systematic reviews reporting 33 meta-analyses of mortality outcomes from 53 unique randomised controlled trials. Of the 33 meta-analyses, one was graded as high quality, 15 were moderate, and 17 were low. Of the meta-analyses presenting high- to moderate-quality evidence, 12 (75.0%) reported no statistically significant difference in mortality between restrictive and liberal transfusion groups and four (25.0%) reported significantly lower mortality for patients assigned to a restrictive transfusion strategy. We found few systematic reviews addressed clinical differences between included studies: variation was observed in haemoglobin threshold concentrations, the absolute between group difference in haemoglobin threshold concentration, time to randomisation (resulting in transfusions administered prior to randomisation), and transfusion dosing regimens.

CONCLUSIONS

Meta-analyses graded as high to moderate quality indicate that in most patient populations no difference in mortality exists between patients assigned to a restrictive or liberal transfusion strategy.

TRIAL REGISTRATION

PROSPERO CRD42019120503.

"Risk factors for ventilator-associated pneumonia following cardiac surgery: case-control study"

BACKGROUND

Ventilator-associated pneumonia (VAP) following cardiac surgery is a preventable complication associated with adverse outcomes.

AIMS

We aimed to assess risk factors and outcomes of VAP following cardiac surgery.

METHODS

A matched 1:3 case:control study, including adult patients undergoing cardiac surgery through sternotomy between Sep-2014 to Mar-2017 was conducted in a tertiary-care hospital in Israel. Cases included all patients developing VAP within 30 days after surgery, defined using consensus criteria. Controls were matched for age, gender and surgery type. Operative data were collected prospectively, other data were collected retrospectively. Cox regression was used for adjusted analysis of matched data.

FINDINGS

Out of 946 operated patients, we identified 57 patients with VAP after cardiac surgery (17.7 episodes per 1000 ventilator-days) matched to 149 controls. Significant independent risk factors for VAP included congestive heart failure (OR 2.357 95%CI 1.052-5.281), Chest re-exploration in ICU (OR 10.213 95%CI: 2.235-46.678), preoperative glucose levels (OR 1.1010 per 1 mg/dl increase 95%CI: 1.004-1.019) intraoperative red blood cell transfusions (OR 1.542 per 1 unit 95%CI: 1.109-2.094) and pulmonary hypertension (OR 2.261 95%CI 1.048-6.554). VAP was most commonly caused by Gram-negative pathogens. VAP was associated with higher mortality, longer length of stay, longer need for ventilator support and longer stay in ICU setting.

CONCLUSIONS

Postoperative VAP in cardiac surgery patients is associated with severe clinical outcomes. We identified risk factors that can aid in preventive measures implementation for high risk patients.

Red cell use in trauma

PURPOSE OF REVIEW

Red cell transfusions are commonly used in management of hemorrhage in trauma patients. The appropriate indications and criteria for transfusion are still debated. Here, we summarize the recent findings on the use of red cell transfusion in trauma setting.

RECENT FINDINGS

Recent evidence continues to support the long-established link between allogeneic transfusion and worse clinical outcomes, reinstating the importance of more judicious use of allogeneic blood and careful consideration of benefits versus risks when making transfusion decisions. Studies support restrictive transfusion strategies (often based on hemoglobin thresholds of 7-8 g/dl) in most patient populations, although some argue more caution in specific populations (e.g. patients with traumatic brain injury) and more studies are needed to determine if these patients benefit from less restrictive transfusion strategies. It should be remembered that anemia remains an independent risk factor for worse outcomes and red cell transfusion does not constitute a lasting treatment. Anemia should be properly assessed and managed based on the cause and using hematinic medications as indicated.

SUMMARY

Although the debate on hemoglobin thresholds for transfusion continues, clinicians should not overlook proper management of the underlying issue (anemia).