Using arterial-venous oxygen difference to guide red blood cell transfusion strategy

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.

Transfusion increased skin blood flow when initially low in volume-resuscitated patients without acute bleeding

Background

Alterations in skin blood flow is a marker of inadequate tissue perfusion in critically ill patients after initial resuscitation. The effects of red blood cell transfusions (RBCT) on skin perfusion are not described in this setting. We evaluated the effects of red blood cell transfusions on skin tissue perfusion in critically ill patients without acute bleeding after initial resuscitation.

Methods

A prospective observational study included 175 non-bleeding adult patients after fluid resuscitation requiring red blood cell transfusions. Using laser Doppler, we measured finger skin blood flow (SBF) at skin basal temperature (SBFBT), together with mean arterial pressure (MAP), heart rate (HR), hemoglobin (Hb), central venous pressure (CVP), lactate, and central or mixed venous oxygen saturation before and 1 h after RBCT. SBF responders were those with a 20% increase in SBFBT after RBCT.

Results

Overall, SBFBT did not significantly change after RBCT [from 79.8 (4.3-479.4) to 83.4 (4.9-561.6); p = 0.67]. A relative increase equal to or more than 20% in SBFBT after RBCT (SBF responders) was observed in 77/175 of RBCT (44%). SBF responders had significantly lower SBFBT [41.3 (4.3-279.3) vs. 136.3 (6.5-479.4) perfusion units; p < 0.01], mixed or central venous oxygen saturation (62.5 ± 9.2 vs. 67.3% ± 12.0%; p < 0.01) and CVP (8.3 ± 5.1 vs. 10.3 ± 5.6 mmHg; p = 0.03) at baseline than non-responders. SBFBT increased in responders [from 41.3 (4.3-279.3) to 93.1 (9.8-561.6) perfusion units; p < 0.01], and decreased in the non-responders [from 136.3 (6.5-479.4) to 80.0 (4.9-540.8) perfusion units; p < 0.01] after RBCT. Pre-transfusion SBFBT was independently associated with a 20% increase in SBFBT after RBCT. Baseline SBFBT had an area under receiver operator characteristic of 0.73 (95% CI, 0.68-0.83) to predict SBFBT increase; A SBFBT of 73.0 perfusion units (PU) had a sensitivity of 71.4% and a specificity of 70.4% to predict SBFBT increase after RBCT. No significant differences in SBFBT were observed after RBCT in different subgroup analyses.

Conclusion

The skin blood flow is globally unaltered by red blood cell transfusions in non-bleeding critically ill patients after initial resuscitation. However, a lower SBFBT at baseline was associated with a relative increase in skin tissue perfusion after RBCT.

Perioperative Fluid Management

The medical complexity of the geriatric patients has been steadily rising. Still, as outcomes of surgical procedures in the elderly are improving, centers are pushing boundaries. There is also a growing appreciation of the importance of perioperative fluid management on postoperative outcomes, especially in the elderly. Optimal fluid management in this cohort is challenging due to the combination of age-related physiological changes in organ function, increased comorbid burden, and larger fluid shifts during more complex surgical procedures. The current state-of-the-art approach to fluid management in the perioperative period is outlined.

Assessment of oxygen extraction rate changes following red blood cell transfusion in the intensive care unit: a protocol for a prospective observational non-interventional study

INTRODUCTION

Haemoglobin transfusion thresholds have been used in the intensive care unit (ICU) to guide red blood cell transfusion (RBCT) decisions. Recent research has also focused on physiological indicators of tissue oxygenation as trigger points for blood transfusion. This study aims to assess the oxygen extraction rate (O2ER) as a critical indicator of the oxygen delivery-consumption balance in tissues and investigate its potential as a reliable trigger for blood transfusion in ICU patients by analysing clinical outcomes. The utilisation of physiological indicators may expedite the decision-making process for RBCT in patients requiring immediate intervention, while simultaneously minimising the risks associated with unnecessary transfusions.

METHODS AND ANALYSIS

This prospective, single-centre, observational cohort study will include 65 ICU patients undergoing RBCT. We will evaluate essential markers such as arterial oxygen content, central venous oxygen content, arteriovenous oxygen difference, O2ER and near-infrared spectroscopy before and 15 min after transfusion. The primary outcome is the percentage increase in O2ER between the two groups relative to the initial O2ER level. Secondary outcomes will assess complications and patient outcomes in relation to baseline O2ER. A 90-day comprehensive follow-up period will be implemented for all enrolled patients.

ETHICS AND DISSEMINATION

This study has obtained ethics committee approval from the Izmir Katip Celebi University Non-Interventional Clinical Studies Institutional Review Board. Written informed consent will be obtained from all patients before their enrolment in the study. The findings will be disseminated through publication in peer-reviewed journals and presentation at national or international conferences.

TRIAL REGISTRATION NUMBER

NCT05798130.

Management of severe peri-operative bleeding: Guidelines from the European Society of Anaesthesiology and Intensive Care: Second update 2022

BACKGROUND

Management of peri-operative bleeding is complex and involves multiple assessment tools and strategies to ensure optimal patient care with the goal of reducing morbidity and mortality. These updated guidelines from the European Society of Anaesthesiology and Intensive Care (ESAIC) aim to provide an evidence-based set of recommendations for healthcare professionals to help ensure improved clinical management.

DESIGN

A systematic literature search from 2015 to 2021 of several electronic databases was performed without language restrictions. Grading of Recommendations, Assessment, Development and Evaluation (GRADE) was used to assess the methodological quality of the included studies and to formulate recommendations. A Delphi methodology was used to prepare a clinical practice guideline.

RESULTS

These searches identified 137 999 articles. All articles were assessed, and the existing 2017 guidelines were revised to incorporate new evidence. Sixteen recommendations derived from the systematic literature search, and four clinical guidances retained from previous ESAIC guidelines were formulated. Using the Delphi process on 253 sentences of guidance, strong consensus (>90% agreement) was achieved in 97% and consensus (75 to 90% agreement) in 3%.

DISCUSSION

Peri-operative bleeding management encompasses the patient's journey from the pre-operative state through the postoperative period. Along this journey, many features of the patient's pre-operative coagulation status, underlying comorbidities, general health and the procedures that they are undergoing need to be taken into account. Due to the many important aspects in peri-operative nontrauma bleeding management, guidance as to how best approach and treat each individual patient are key. Understanding which therapeutic approaches are most valuable at each timepoint can only enhance patient care, ensuring the best outcomes by reducing blood loss and, therefore, overall morbidity and mortality.

CONCLUSION

All healthcare professionals involved in the management of patients at risk for surgical bleeding should be aware of the current therapeutic options and approaches that are available to them. These guidelines aim to provide specific guidance for bleeding management in a variety of clinical situations.

Patient Blood Management, Anemia, and Transfusion Optimization Across Surgical Specialties

Patient blood management (PBM) is a systematic, evidence-based approach to improve patient outcomes by managing and preserving a patient's own blood and minimizing allogenic transfusion need and risk. According to the PBM approach, the goals of perioperative anemia management include early diagnosis, targeted treatment, blood conservation, restrictive transfusion except in cases of acute and massive hemorrhage, and ongoing quality assurance and research efforts to advance overall blood health.

Appropriateness of Allogeneic Red Blood Cell Transfusions in Non-Bleeding Patients in a Large Teaching Hospital: A Retrospective Study

In hemodynamically stable patients, both anemia and red blood cell (RBC) transfusion may be detrimental to patients; hence, a decision regarding RBC transfusion should be based on thorough risk-benefit assessment. According to hematology and transfusion medicine organizations, RBC transfusion is indicated when recommended hemoglobin (Hb) triggers are met, and symptoms of anemia are present. The aim of our study was to examine the appropriateness of RBC transfusions in non-bleeding patients at our institution. We performed a retrospective analysis of all RBC transfusions performed between January 2022 and July 2022. The appropriateness of RBC transfusion was based on the most recent Association for the Advancement of Blood and Biotherapies (AABB) guidelines and some additional criteria. The overall incidence of RBC transfusions at our institution was 10.2 per 1000 patient-days. There were 216 (26.1%) RBC units appropriately transfused and 612 (73.9%) RBC units that were transfused with no clear indications. The incidence of appropriate and inappropriate RBC transfusions were 2.6 and 7.5 per 1000 patient-days, respectively. The most frequent clinical situations when RBC transfusion was classified as appropriate were: Hb < 70 g/L plus cognitive problems/headache/dizziness (10.1%), Hb < 60 g/L (5.4%), and Hb < 70 g/L plus dyspnea despite oxygen therapy (4.3%). The most frequent causes of inappropriate RBC transfusions were: no Hb determination pre-RBC transfusion (n = 317) and, among these, RBC transfused as a second unit in a single-transfusion episode (n = 260); absence of anemia sings/symptoms pre-transfusion (n = 179); and Hb concentration ≥80 g/L (n = 80). Although the incidence of RBC transfusions in non-bleeding inpatients in our study was generally low, the majority of RBC transfusions were performed outside recommended indications. Red blood cell transfusions were evaluated as inappropriate mainly due to multiple-unit transfusion episodes, absence of anemia signs and/or symptoms pre- transfusion, and liberal transfusion triggers. There is still the need to educate physicians on appropriate indications for RBC transfusion in non-bleeding patients.

P(v-a)CO2/C(a-v)O2 as a red blood cell transfusion trigger and prognostic indicator for sepsis-related anaemia: protocol for a prospective cohort study

INTRODUCTION

Red blood cell (RBC) transfusion primarily aims to improve oxygen transport and tissue oxygenation. The transfusion strategy based on haemoglobin concentration could not accurately reflect cellular metabolism. The ratio of venous-arterial carbon dioxide tension difference to arterial-venous oxygen content difference (P(v-a)CO₂/C(a-v)O₂) is a good indicator of cellular hypoxia. We aim to explore the influence of P(v-a)CO₂/C(a-v)O₂ as an RBC transfusion trigger on outcomes in septic shock patients.

METHODS AND ANALYSIS

The study is a single-centre prospective cohort study. We consecutively enrol adult septic shock patients requiring RBC transfusion at intensive care unit (ICU) admission or during ICU stay. P(v-a)CO₂/C(a-v)O₂ will be recorded before and 1 hour after each transfusion. The primary outcome is ICU mortality. Binary logistic regression analyses will be performed to detect the independent association between P(v-a)CO₂/C(a-v)O₂ and ICU mortality. A cut-off value for P(v-a)CO₂/C(a-v)O₂ will be obtained by maximising the Youden index with the receiver operator characteristic curve. According to this cut-off value, patients included will be divided into two groups: one with the P(v-a)CO₂/C(a-v)O₂ >cut-off and the other with the P(v-a)CO₂/C(a-v)O₂ ≤cut off. Differences in clinical outcomes between the two groups will be assessed after propensity matching.

ETHICS AND DISSEMINATION

The study has been approved by the Institutional Review Board of Affiliated Hospital of Weifang Medical University (wyfy-2021-ky-059). Findings will be disseminated through conference presentations and peer-reviewed journals.

TRIAL REGISTRATION NUMBER

ChiCTR2100051748.

The Impact of Red Blood Cell Transfusion on Blood Lactate in Non-Bleeding Critically Ill Patients-A Retrospective Cohort Study

Anemia should preferably be managed without red blood cell transfusion (RBCT); instead, therapy should be focused on causes of anemia along with efforts to minimize blood loss. Lactate could potentially be used as a physiologic RBCT trigger, although there are some limitations to its interpretation. The aim of our study was to analyze the impact of RBCT on blood lactate with consideration of factors known to increase its concentration and to assess the usefulness of blood lactate as a potential physiologic RBCT trigger. We performed a retrospective analysis of all RBCT episodes in non-bleeding critically ill patients. We retrieved demographic data, data on RBCT itself (duration, type of RBC, volume of RBC, age of RBC), laboratory parameters (lactate, hemoglobin, glucose, total bilirubin), and factors potentially increasing lactate. We analyzed 77 RBCTs with elevated pre-RBCT lactate. The median age of patients was 66 (IQR 57–73) years and the distribution of sexes was even. The named factors potentially influencing lactate had no impact on its concentration. The median pre-post RBCT lactate was 2.44 (IQR 2.08–3.27) and 2.13 (IQR 1.75–2.88) mmol/L, respectively (p < 0.01); the median decrease was 0.41 (IQR 0.07–0.92) mmol/L. We conclude that RBCT did not normalize mildly elevated lactate. Common causes of elevated lactate probably had no impact on its concentration. Therefore lactate may have a limited role as a physiologic RBCT trigger in non-bleeding severely anemic critically ill patients.

The Underestimated Role of Platelets in Severe Infection a Narrative Review

Beyond their role in hemostasis, platelets have emerged as key contributors in the immune response; accordingly, the occurrence of thrombocytopenia during sepsis/septic shock is a well-known risk factor of mortality and a marker of disease severity. Recently, some studies elucidated that the response of platelets to infections goes beyond a simple fall in platelets count; indeed, sepsis-induced thrombocytopenia can be associated with—or even anticipated by—several changes, including an altered morphological pattern, receptor expression and aggregation. Of note, alterations in platelet function and morphology can occur even with a normal platelet count and can modify, depending on the nature of the pathogen, the pattern of host response and the severity of the infection. The purpose of this review is to give an overview on the pathophysiological interaction between platelets and pathogens, as well as the clinical consequences of platelet dysregulation. Furthermore, we try to clarify how understanding the nature of platelet dysregulation may help to optimize the therapeutic approach.

Transfusion thresholds for guiding red blood cell transfusion

BACKGROUND

The optimal haemoglobin threshold for use of red blood cell (RBC) transfusions in anaemic patients remains an active field of research. Blood is a scarce resource, and in some countries, transfusions are less safe than in others because of inadequate testing for viral pathogens. If a liberal transfusion policy does not improve clinical outcomes, or if it is equivalent, then adopting a more restrictive approach could be recognised as the standard of care.  OBJECTIVES: The aim of this review update was to compare 30-day mortality and other clinical outcomes for participants randomised to restrictive versus liberal red blood cell (RBC) transfusion thresholds (triggers) for all clinical conditions. The restrictive transfusion threshold uses a lower haemoglobin concentration as a threshold for transfusion (most commonly, 7.0 g/dL to 8.0 g/dL), and the liberal transfusion threshold uses a higher haemoglobin concentration as a threshold for transfusion (most commonly, 9.0 g/dL to 10.0 g/dL).

SEARCH METHODS

We identified trials through updated searches: CENTRAL (2020, Issue 11), MEDLINE (1946 to November 2020), Embase (1974 to November 2020), Transfusion Evidence Library (1950 to November 2020), Web of Science Conference Proceedings Citation Index (1990 to November 2020), and trial registries (November 2020). We  checked the reference lists of other published reviews and relevant papers to identify additional trials. We were aware of one trial identified in earlier searching that was in the process of being published (in February 2021), and we were able to include it before this review was finalised.

SELECTION CRITERIA

We included randomised trials of surgical or medical participants that recruited adults or children, or both. We excluded studies that focused on neonates. Eligible trials assigned intervention groups on the basis of different transfusion schedules or thresholds or 'triggers'. These thresholds would be defined by a haemoglobin (Hb) or haematocrit (Hct) concentration below which an RBC transfusion would be administered; the haemoglobin concentration remains the most commonly applied marker of the need for RBC transfusion in clinical practice. We included trials in which investigators had allocated participants to higher thresholds or more liberal transfusion strategies compared to more restrictive ones, which might include no transfusion. As in previous versions of this review, we did not exclude unregistered trials published after 2010 (as per the policy of the Cochrane Injuries Group, 2015), however, we did conduct analyses to consider the differential impact of results of trials for which prospective registration could not be confirmed.   DATA COLLECTION AND ANALYSIS: We identified trials for inclusion and extracted data using Cochrane methods. We pooled risk ratios of clinical outcomes across trials using a random-effects model. Two review authors independently extracted data and assessed risk of bias. We conducted predefined analyses by clinical subgroups. We defined participants randomly allocated to the lower transfusion threshold as being in the 'restrictive transfusion' group and those randomly allocated to the higher transfusion threshold as being in the 'liberal transfusion' group.

MAIN RESULTS

A total of 48 trials, involving data from 21,433 participants (at baseline), across a range of clinical contexts (e.g. orthopaedic, cardiac, or vascular surgery; critical care; acute blood loss (including gastrointestinal bleeding); acute coronary syndrome; cancer; leukaemia; haematological malignancies), met the eligibility criteria. The haemoglobin concentration used to define the restrictive transfusion group in most trials (36) was between 7.0 g/dL and 8.0 g/dL.  Most trials included only adults; three trials focused on children. The included studies were generally at low risk of bias for key domains including allocation concealment and incomplete outcome data. Restrictive transfusion strategies reduced the risk of receiving at least one RBC transfusion by 41% across a broad range of clinical contexts (risk ratio (RR) 0.59, 95% confidence interval (CI) 0.53 to 0.66; 42 studies, 20,057 participants; high-quality evidence), with a large amount of heterogeneity between trials (I² = 96%). Overall, restrictive transfusion strategies did not increase or decrease the risk of 30-day mortality compared with liberal transfusion strategies (RR 0.99, 95% CI 0.86 to 1.15; 31 studies, 16,729 participants; I² = 30%; moderate-quality evidence) or any of the other outcomes assessed (i.e. cardiac events (low-quality evidence), myocardial infarction, stroke, thromboembolism (all high-quality evidence)). High-quality evidence shows that the liberal transfusion threshold did not affect the risk of infection (pneumonia, wound infection, or bacteraemia). Transfusion-specific reactions are uncommon and were inconsistently reported within trials. We noted less certainty in the strength of evidence to support the safety of restrictive transfusion thresholds for the following predefined clinical subgroups: myocardial infarction, vascular surgery, haematological malignancies, and chronic bone-marrow disorders.

AUTHORS' CONCLUSIONS

Transfusion at a restrictive haemoglobin concentration decreased the proportion of people exposed to RBC transfusion by 41% across a broad range of clinical contexts. Across all trials, no evidence suggests that a restrictive transfusion strategy impacted 30-day mortality, mortality at other time points, or morbidity (i.e. cardiac events, myocardial infarction, stroke, pneumonia, thromboembolism, infection) compared with a liberal transfusion strategy. Despite including 17 more randomised trials (and 8846 participants), data remain insufficient to inform the safety of transfusion policies in important and selected clinical contexts, such as myocardial infarction, chronic cardiovascular disease, neurological injury or traumatic brain injury, stroke, thrombocytopenia, and cancer or haematological malignancies, including chronic bone marrow failure.  Further work is needed to improve our understanding of outcomes other than mortality. Most trials compared only two separate thresholds for haemoglobin concentration, which may not identify the actual optimal threshold for transfusion in a particular patient. Haemoglobin concentration may not be the most informative marker of the need for transfusion in individual patients with different degrees of physiological adaptation to anaemia. Notwithstanding these issues, overall findings provide good evidence that transfusions with allogeneic RBCs can be avoided in most patients with haemoglobin thresholds between the range of 7.0 g/dL and 8.0 g/dL. Some patient subgroups might benefit from RBCs to maintain higher haemoglobin concentrations; research efforts should focus on these clinical contexts.

Transfusion in the mechanically ventilated patient

Red blood cell transfusions are a frequent intervention in critically ill patients, including in those who are receiving mechanical ventilation. Both these interventions can impact negatively on lung function with risks of transfusion-related acute lung injury (TRALI) and other forms of acute respiratory distress syndrome (ARDS). The interactions between transfusion, mechanical ventilation, TRALI and ARDS are complex and other patient-related (e.g., presence of sepsis or shock, disease severity, and hypervolemia) or blood product-related (e.g., presence of antibodies or biologically active mediators) factors also play a role. We propose several strategies targeted at these factors that may help limit the risks of associated lung injury in critically ill patients being considered for transfusion.