Anaemia secondary to critical illness: an unexplained phenomenon

Jehovah's Witness Needing Critical Care: A Narrative Review on the Expanding Arsenal

Present day Jehovah's Witness (JW) religion accounts for 8.5 million followers. A tenant feature of the JW faith is religious objection to transfusions of blood and blood products. Interpatient variability, as it pertains to blood and blood products may occur; hence, a confidential interview will determine which products individual may consent to (Marsh and Bevan, 2002). This belief and practice place great restrictions on treating medical professionals in scenarios of life-threatening anaemia and active haemorrhage. The review to follow explores the physiological and pathophysiological consequences of severe anaemia. Non-blood transfusion practices are explored, many of which are potentially lifesaving. Particular attention is drawn to the evolving science involving artificial oxygen carriers and their use in emergency situations. A greater safety profile ensures its future use amongst religious objectors to be greatly beneficial. Intravenous iron supplementation has enjoyed a lively debate within the critical care community. A review of recent systematic and meta-analysis supports its use in the ICU; however, more investigation is needed into the complementary use of hepcidin.

Patient, hospital and environmental costs of unnecessary bloodwork: capturing the triple bottom line of inappropriate care in general surgery patients

OBJECTIVE

To characterise the extent of unnecessary care in general surgery inpatients using a triple bottom line approach.

DESIGN

Patients with uncomplicated acute surgical conditions were retrospectively evaluated for unnecessary bloodwork according to the triple bottom line, quantifying the impacts on patients, healthcare costs and greenhouse gas emissions. The carbon footprint of common laboratory investigations was estimated using PAS2050 methodology, including emissions generated from the production, transport, processing and disposal of consumable goods and reagents.

SETTING

Single-centre tertiary care hospital.

PARTICIPANTS

Patients admitted with acute uncomplicated appendicitis, cholecystitis, choledocholithiasis, gallstone pancreatitis and adhesive small bowel obstruction were included in the study. 304 patients met inclusion criteria and 83 were randomly selected for in-depth chart review.

MAIN OUTCOME MEASURES

In each patient population, the extent of over-investigation was determined by comparing ordered laboratory investigations against previously developed consensus recommendations. The quantity of unnecessary bloodwork was measured by number of phlebotomies, tests and blood volume in addition to healthcare costs and greenhouse gas emissions.

RESULTS

76% (63/83) of evaluated patients underwent unnecessary bloodwork resulting in a mean of 1.84 phlebotomies, 4.4 blood vials, 16.5 tests and 18 mL of blood loss per patient. The hospital and environmental cost of these unnecessary activities was $C5235 and 61 kg CO₂e (974 g CO₂e per person), respectively. The carbon footprint of a common set of investigations (complete blood count, differential, creatinine, urea, sodium, potassium) was 332 g CO₂e. Adding a liver panel (liver enzymes, bilirubin, albumin, international normalised ratio/partial thromboplastin time) resulted in an additional 462 g CO₂e.

CONCLUSIONS

We found considerable overuse of laboratory investigations among general surgery patients admitted with uncomplicated acute surgical conditions resulting in unnecessary burden to patients, hospitals and the environment. This study identifies an opportunity for resource stewardship and exemplifies a comprehensive approach to quality improvement.

Can affinity of hemoglobin to oxygen to be a prognostic marker in critically ill COVID-19 patients?

Background

This study's objective is to determine the slope of the hemoglobin oxygen dissociation curve in critically ill patients who have COVID-19 along with blood gas measurements and how mortality might be impacted by this circumstance.

Aim

It has been reported that the hemoglobin oxygen dissociation curve is not different from healthy patients in COVID-19. However, there are insufficient data on the behavior of the curve in patients who require intensive care.

Patients and Methods

This retrospective study was conducted between 01.03.2021 and 01.07.2021 with patients who were followed up due to COVID-19 in adult intensive care unit. P50 and lactate value obtained from in vitro calculated blood gas analysis. The survival status of the patients was recorded.

Results

The mean P50 value at the admission of nonsurvivors was significantly higher than survivors. In correlation analysis, a significant positive correlation was seen between P50, mortality, and lactate level at admission. SpO₂, PaO₂/FiO₂ ratio, and length of stay in intensive care unit were significantly negatively correlated with P50 levels.

Conclusion

A right shift in the hemoglobin oxygen dissociation curve is associated with mortality. Lactate levels were also associated with a right shift. Prospective experimental studies are needed to provide a better understanding of this process.

The oxygen dissociation curve of blood in COVID-19

COVID-19 hinders oxygen transport to the consuming tissues by at least two mechanisms: In the injured lung, saturation of hemoglobin is compromised, and in the tissues, an associated anemia reduces the volume of delivered oxygen. For the first problem, increased hemoglobin oxygen affinity [left shift of the oxygen dissociation curve (ODC)] is of advantage, for the second, however, the contrary is the case. Indeed a right shift of the ODC has been found in former studies for anemia caused by reduced cell production or hemolysis. This resulted from increased 2,3-bisphosphoglycerate (2,3-BPG) concentration. In three investigations in COVID-19, however, no change of hemoglobin affinity was detected in spite of probably high [2,3-BPG]. The most plausible cause for this finding is formation of methemoglobin (MetHb), which increases the oxygen affinity and thus apparently compensates for the 2,3-BPG effect. However, this "useful effect" is cancelled by the concomitant reduction of functional hemoglobin. In the largest study on COVID-19, even a clear left shift of the ODC was detected when calculated from measurements in fresh blood rather than after equilibration with gases outside the body. This additional "in vivo" left shift possibly results from various factors, e.g., concentration changes of Cl-, 2,3-BPG, ATP, lactate, nitrocompounds, glutathione, glutamate, because of time delay between blood sampling and end of equilibration, or enlarged distribution space including interstitial fluid and is useful for O2 uptake in the lungs. Under discussion for therapy are the affinity-increasing 5-hydroxymethyl-2-furfural (5-HMF), erythropoiesis-stimulating substances like erythropoietin, and methylene blue against MetHb formation.

Decreased total iron binding capacity upon intensive care unit admission predicts red blood cell transfusion in critically ill patients

Introduction

Red blood cell (RBC) transfusion is associated with poor clinical outcome in critically ill patients. We investigated the predictive value of biomarkers on intensive care units (ICU) admission for RBC transfusion within 28 days.

Methods

Critically ill patients (n = 175) who admitted to our ICU with organ dysfunction and an expected stay of ≥ 48 hours, without hemorrhage, were prospectively studied (derivation cohort, n = 121; validation cohort, n = 54). Serum levels of 12 biomarkers (hemoglobin, creatinine, albumin, interleukin-6 [IL-6], erythropoietin, Fe, total iron binding capacity [TIBC], transferrin, ferritin, transferrin saturation, folate, and vitamin B12) were measured upon ICU admission, days 7, 14, 21 and 28.

Results

Among the 12 biomarkers measured upon ICU admission, levels of hemoglobin, albumin, IL-6, TIBC, transferrin and ferritin were statistically different between transfusion and non-transfusion group. Of 6 biomarkers, TIBC upon ICU admission had the highest area under the curve value (0.835 [95% confidence interval] = 0.765–0.906) for predicting RBC transfusion (cut-off value = 234.5 μg/dL; sensitivity = 0.906, specificity = 0.632). This result was confirmed in validation cohort, whose sensitivity and specificity were 0.888 and 0.694, respectively. Measurement of these biomarkers every seven days revealed that albumin, TIBC and transferrin were statistically different between groups throughout hospitalization until 28 days. In validation cohort, patients in the transfusion group had significantly higher serum hepcidin levels than those in the non-transfusion group (P = 0.004). In addition, joint analysis across derivation and validation cohorts revealed that the serum IL-6 levels were higher in the transfusion group (P = 0.0014).

Conclusion

Decreased TIBC upon ICU admission has high predictive value for RBC transfusion unrelated to hemorrhage within 28 days.

Acute Inflammation and Metabolism

Inflammation is an adaptive process to the noxious stimuli that the human body is constantly exposed to. From the local inflammatory response to a full-blown systemic inflammation, a wide complex sequence of events occurs. Persistent immunosuppression and catabolism may ensue, until multiple organ failure finally sets in. And since clinically useful and specific biomarkers are lacking, diagnosis may come late. A thorough understanding of these events (how they begin, how they evolve, and how to modulate them) is imperative, but as yet poorly studied. This review aims to consolidate current knowledge of these events so that the management of these patients is not only evidence-based, but also built on an understanding of the inner workings of the human body in health and in disease.

Anaemia and transfusion triggers in critically ill patients - What we have learnt thus far

Anaemia is a common finding in critically ill patients, the cause of which is multi-factorial including: sepsis, haemolysis (and disseminated intravascular coagulation), iatrogenic blood loss secondary to laboratory sampling, post-operative anaemia, bone marrow suppression/failure, decreased production of erythropoietin, anaemia secondary to drugs/toxins, overt or occult blood loss, functional iron deficiency, poor nutrition and haemodilution. Anaemia is associated with deleterious outcomes including increased risk of cardiac-related morbidity and mortality and decrease in oxygen-carrying capacity in the face of increased metabolic demands. There is a growing body of evidence, which demonstrates that packed red blood cell transfusions are associated with poorer outcomes. Clinicians therefore need to weigh the potential benefit of treating anaemia against the desire to avoid unnecessary transfusions. We explored current literature regarding transfusion triggers and morbidity and mortality associated with packed red blood cell transfusions transfusion, concentrating on studies that have been conducted in critical care patients. In addition, we reflected on trials which considered the viability of iron transfusion and erythropoietin in critically unwell patients.

Iron and inflammation - the gut reaction

Anemia is a frequent complication of many inflammatory disorders, including inflammatory bowel disease. Although the pathogenesis of this problem is multifactorial, a key component is the abnormal elevation of the hormone hepcidin, the central regulator of systemic iron homeostasis. Investigations over the last decade have resulted in important insights into the role of hepcidin in iron metabolism and the mechanisms that lead to hepcidin dysregulation in the context of inflammation. These insights provide the foundation for novel strategies to prevent and treat the anemia associated with inflammatory diseases.

Extracellular histones induce erythrocyte fragility and anemia

Extracellular histones have been shown to play an important pathogenic role in many diseases, primarily through their cytotoxicity toward nucleated cells and their ability to promote platelet activation with resultant thrombosis and thrombocytopenia. In contrast, little is known about the effect of extracellular histones on erythrocyte function. We demonstrate in this study that histones promote erythrocyte aggregation, sedimentation, and using a novel in vitro shear stress model, we show that histones induce erythrocyte fragility and lysis in a concentration-dependent manner. Furthermore, histones impair erythrocyte deformability based on reduced passage of erythrocytes through an artificial spleen. These in vitro results were mirrored in vivo with the injection of histones inducing anemia within minutes of administration, with a concomitant increase in splenic hemoglobin content. Thrombocytopenia and leukopenia were also observed. These findings suggest that histones binding to erythrocytes may contribute to the elevated erythrocyte sedimentation rates observed in inflammatory conditions. Furthermore, histone-induced increases in red blood cell lysis and splenic clearance may be a significant factor in the unexplained anemias seen in critically ill patients.

The UK Cardiac and Vascular Surgery Interventional Anaemia Response (CAVIAR) Study: protocol for an observational cohort study to determine the impact and effect of preoperative anaemia management in cardiac and vascular surgical patients

INTRODUCTION

Preoperative anaemia is linked to poor postsurgical outcome, longer hospital stays, greater risk of complications and mortality. Currently in the UK, some sites have developed anaemia clinics or pathways that use intravenous iron to correct iron deficiency anaemia prior to surgery as their standard of care. Although intravenous iron has been observed to be effective in a variety of patient settings, there is insufficient evidence in its use in cardiac and vascular patients. The aim of this study is to observe the impact and effect of anaemia and its management in patients undergoing cardiac and vascular surgery. In addition, the UK Cardiac and Vascular Surgery Interventional Anaemia Response (CAVIAR) Study is also a feasibility study with the aim to establish anaemia management pathways in the preoperative setting to inform the design of future randomised controlled trials.

METHODS AND ANALYSIS

The UK CAVIAR Study is a multicentre, stepped, observational study, in patients awaiting major cardiac or vascular surgery. We will be examining different haematological variables (especially hepcidin), functional capacity and patient outcome. Patients will be compared based on their anaemia status, whether they received intravenous iron in accordance to their hospital's preoperative pathway, and their disease group. The primary outcomes are the change in haemoglobin levels from baseline (before treatment) to before surgery; and the number of successful patients recruited and consented (feasibility). The secondary outcomes will include changes in biomarkers of iron deficiency, length of stay, quality of life and postoperative recovery.

ETHICS AND DISSEMINATION

The study protocol was approved by the London-Westminster Research Ethics Committee (15/LO/1569, 27 November 2015). NHS approval was also obtained with each hospital trust. The findings of the study will be published in peer-reviewed journals.

TRIAL REGISTRATION NUMBER

Clinical Trials registry (NCT02637102) and the ISRCTN registry (ISRCTN55032357).

Epidemiology of RBC Transfusions in Patients With Severe Acute Kidney Injury: Analysis From the Randomized Evaluation of Normal Versus Augmented Level Study

OBJECTIVE

To assess the epidemiology and outcomes associated with RBC transfusion in patients with severe acute kidney injury requiring continuous renal replacement therapy.

DESIGN

Post hoc analysis of data from a multicenter, randomized, controlled trial.

SETTING

Thirty-five ICUs in Australia and New Zealand.

PATIENTS

Cohort of 1,465 patients enrolled in the Randomized Evaluation of Normal versus Augmented Level replacement therapy study.

INTERVENTIONS

Daily information on morning hemoglobin level and amount of RBC transfused were prospectively collected in the Randomized Evaluation of Normal versus Augmented Level study. We analyzed the epidemiology of such transfusions and their association with clinical outcomes.

MEASUREMENTS AND MAIN RESULTS

Overall, 977 patients(66.7%) received a total of 1,192 RBC units. By day 5, 785 of 977 transfused patients (80.4%) had received at least one RBC transfusion. Hemoglobin at randomization was lower in transfused than in nontransfused patients (94 vs 111 g/L; p < 0.001). Mean daily hemoglobin was 88 ± 7 and 99 ± 12 g/L in transfused and nontransfused patients. Among transfused patients, 228 (46.7%) had died by day 90 when compared with 426 (43.6%) of nontransfused patients (p = 0.27). Survivors received on average 316 ± 261 mL of RBC, whereas nonsurvivors received 302 ± 362 mL (p = 0.42). On multivariate Cox regression analysis, RBC transfusion was independently associated with lower 90-day mortality (hazard ratio, 0.55; 95% CI, 0.38-0.79). However, we found no independent association between RBC transfusions and mortality when the analyses were restricted to patients surviving at least 5 days (hazard ratio, 1.29; 95% CI, 0.90-1.85). We found no independent association between RBC transfusion and renal replacement therapy-free days, mechanical ventilator-free days, or length of stay in ICU or hospital.

CONCLUSIONS

In patients with severe acute kidney injury treated with continuous renal replacement therapy, we found no association of RBC transfusion with 90-day mortality or other patient-centered outcomes. The optimal hemoglobin threshold for RBC transfusion in such patients needs to be determined in future randomized controlled trials.

[Hospital-acquired anemia: Facts, consequences and prevention]

Hospital-acquired anemia is common, especially in the most critically ill patients. It may be associated with poor patient outcomes. It may result from increased blood loss, impaired red cell production or reduced red cell life span. Multiple associated factors may contribute simultaneously or sequentially to the decrease in hemoglobin level. Some of them are related to the underlying disease and others are iatrogenic. Clinicians should be aware of the importance and consequences of iatrogenic anemia caused by diagnostic blood sampling. Strategies and measures to minimize iatrogenic blood loss should be prioritized. They may reduce the risk of developing anemia and then red blood cells transfusion requirement.

Anemia in Intensive Care: A Review of Current Concepts

Anemia in patients admitted to an intensive care unit is common and affects almost all critically ill patients. The intensivist is faced with the challenge of treating multifactorial etiologies, mainly bleeding and blood loss due to phlebotomy and decreased erythropoiesis. Red cell transfusion, the most common treatment for anemia, comes with associated risks, which may further reduce the chance of survival of these patients. The best evidence suggests the practice of restrictive RBC transfusion (transfusion at Hb<7 g/dl). In this article, the etiopathogenesis of the anemia in critically ill is reviewed, and current opinion on the pros and cons of various management strategies are discussed with emphasize on restrictive transfusion policy.

Perturbed MafB/GATA1 axis after burn trauma bares the potential mechanism for immune suppression and anemia of critical illness

Patients who survive initial burn injury are susceptible to nosocomial infections. Anemia of critical illness is a compounding factor in burn patients that necessitates repeated transfusions, which further increase their susceptibility to infections and sepsis. Robust host response is dependent on an adequate number and function of monocytes/macrophages and dendritic cells. In addition to impaired RBC production, burn patients are prone to depletion of dendritic cells and an increase in deactivated monocytes. In steady-state hematopoiesis, RBCs, macrophages, and dendritic cells are all generated from a common myeloid progenitor within the bone marrow. We hypothesized in a mouse model of burn injury that an increase in myeloid-specific transcription factor V-maf musculoaponeurotic fibrosarcoma oncogene homolog B at the common myeloid progenitor stage steers their lineage potential away from the megakaryocyte erythrocyte progenitor production and drives the terminal fate of common myeloid progenitors to form macrophages vs. dendritic cells, with the consequences being anemia, monocytosis, and dendritic cell deficits. Results indicate that, even though burn injury stimulated bone marrow hematopoiesis by increasing multipotential stem cell production (Lin^negSca1^poscKit^pos), the bone marrow commitment is shifted away from the megakaryocyte erythrocyte progenitor and toward granulocyte monocyte progenitors with corresponding alterations in peripheral blood components, such as hemoglobin, hematocrit, RBCs, monocytes, and granulocytes. Furthermore, burn-induced V-maf musculoaponeurotic fibrosarcoma oncogene homolog B in common myeloid progenitors acts as a transcriptional activator of M-CSFR and a repressor of transferrin receptors, promoting macrophages and inhibiting erythroid differentiations while dictating a plasmacytoid dendritic cell phenotype. Results from small interfering RNA and gain-of-function (gfp-globin transcription factor 1 retrovirus) studies indicate that targeted interventions to restore V-maf musculoaponeurotic fibrosarcoma oncogene homolog B/globin transcription factor 1 balance can mitigate both immune imbalance and anemia of critical illness.