Tolerance of anemia: understanding the adaptive physiological mechanisms which promote survival

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.

Hypervolemia suppresses dilutional anaemic injury in a rat model of haemodilution

Background and Objectives

Haemodilution leads to complications in clinical practice. It is exactly unknown whether this damage is caused by the fluid or by the stretching of the vascular bed. We aimed to compare two different haemodilution techniques at the same anaemic level.

Methods

Normovolemic or hypervolemic haemodilution was performed on twelve adult male Wistar rats. In the normovolemic procedure, blood was withdrawn and instantaneously administered with similar amounts of 6% hydroxyethyl starch (HES 130/0.4). Fluid was administered without withdrawing blood in the hypervolemic procedure. In both models, a 25% haematocrit level was targeted and kept at this level for 90 min to deepen the anaemia effect. Besides haemodynamics measurement, renal function (creatinine, blood urea nitrogen) and injury (tissue norepinephrine, malondialdehyde) were evaluated. Also, systemic hypoxia (lactate), oxidative stress (malondialdehyde, ischaemia-modified albumin), inflammation (tumour necrosis factor-alpha [TNF-α]), osmotic stress, adrenal stress (norepinephrine, epinephrine), and vascular stretching (atrial natriuretic peptide [ANP]) were assessed.

Results

Arterial pressure in the normovolemic group was lower than in the hypervolemic group. Serum creatinine, blood urea nitrogen, and lactate levels were higher in the normovolemic group. Tissue norepinephrine and malondialdehyde levels were higher in the normovolemic group. Serum ANP, malondialdehyde, ischaemia-modified albumin, free haemoglobin, syndecan-1, and TNF-α were higher in both groups compared to respective baseline.

Conclusions

Normovolemic haemodilution may lead to hypoxic kidney injury. The hypervolemic state may be advantageous if fluid is to be administered. Thus, the effect of the fluid itself can be relatively masked.

Methemoglobin as a marker of acute anemic stress in cardiac surgery

Biological evidence supports plasma methemoglobin as a biomarker for anemia-induced tissue hypoxia. In this translational planned substudy of the multinational randomized controlled transfusion thresholds in cardiac surgery (TRICS-III) trial, which included adults undergoing cardiac surgery requiring cardiopulmonary bypass with a moderate-to-high risk of death, we investigated the relationship between perioperative hemoglobin concentration (Hb) and methemoglobin; and evaluated its association with postoperative outcomes. The primary endpoint was a composite of death, myocardial infarction, stroke, and severe acute kidney injury at 28 days. We observe weak non-linear associations between decreasing Hb and increasing methemoglobin, which were strongest in magnitude at the post-surgical time point. Increased levels of post-surgical methemoglobin were associated with a trend toward an elevated risk for stroke and exploratory neurological outcomes. Our generalizable study demonstrates post-surgical methemoglobin may be a marker of anemia-induced organ injury/dysfunction, and may have utility for guiding personalized approaches to anemia management. Clinicaltrials.gov registration NCT02042898.

Use of blood products during the first months of COVID-19 pandemic period: A single center report

The novel coronavirus (SARS-CoV-2) outbreak exerted a serious effect on healthcare. Between 1st of January and May 31, 2020 due to the special regulations in Hungary, the number of reported COVID-19 infections were relatively low (3876 cases). The inpatient and outpatient care and the blood supply were significantly affected by the implemented regulations. The aim of this study was to evaluate the use of blood products amid the first five months of the pandemic situation. This investigation has observed a significant reduction of hospitalizations (37.35%). Analyzing individually the included units, pre-transfusion hemoglobin concentrations of transfused patients presented slight modifications, which were not statistically significant. The special regulations resulted major changes in the frequency of diagnoses at admissions in case of the Department of Surgery, while in case of the other specialities (Division of Hematology and Department of Anesthesiology and Intensive Therapy), there were no major changes compared to pre-pandemic period. Considering each department separately, transfused red blood cell concentrates (RBC) per patient, and the proportion of transfused patients did not change significantly. However, the combination of these modifications resulted in the significant decrease in RBC transfusions (p < 0.0001) compared to the pre-pandemic baseline. With regard to platelet and fresh frozen plasma (FFP), their usage was significantly reduced (44.40% platelet concentrates and 34.27% FFP). Our results indicate that the pandemic had an important effect on the blood product usage at the included departments by introducing different patient care policies and the temporary deferral of the elective surgical interventions. Despite the challenging circumstances of blood collection and blood product supply, the hospitalized patients received adequate care.

Exercise and anemia in cancer patients: could make the difference?

INTRODUCTION

Anemia is one of the most common hematological manifestations occurring in cancer patients, related to a poorer prognosis. Among supportive care in cancer, exercise is emerging as a crucial tool demonstrating to reduce mortality risk, as well as to counteract several diseases and treatment-related adverse events. Nevertheless, the effect of exercise on anemia in cancer is still a relatively unexplored area.

AREA COVERED

Six studies investigated the impact of exercise on anemia trajectory in cancer patients, with intriguing results. The potential mechanisms by which exercise may modulate the blood system are heterogenous, including bone marrow stimulation, improvements in the hematopoietic microenvironment, and control of both inflammation and hormones levels. Although training and/or living at high altitudes is a recognized method to increase erythropoiesis, the effect of a hypoxic external environment on tumor progression should be clarified before considering this strategy in cancer patients.

EXPERT OPINION

Although the available investigations about exercise in anemic patients with cancer are few, exercise emerges as an important supportive oncological care capable of assisting patients maintain their autonomy. Our special report offers several suggestions to address future research in this field and determine the real contribution of an active lifestyle on this condition.

The prognostic effect of hemoglobin on patients with cancer cachexia: a multicenter retrospective cohort study

OBJECTIVES

To clarify the influence of hemoglobin on cancer cachexia and to determine whether hemoglobin affects the prognosis or quality of life of patients with cancer cachexia and whether these effects are caused by an interaction between hemoglobin and other factors.

MATERIAL AND METHODS

This study was a multicenter cohort of 2715 patients with cancer cachexia diagnosed from June 2012 to December 2019. The primary outcomes and measures were overall survival (OS) time and all-cause mortality. The association between hemoglobin and all-cause mortality was evaluated using hazard ratios (HRs) and the restricted cubic spline model with a two-sided p-value. Optimal stratification was used to determine the threshold value. We also evaluated the cross-classification of hemoglobin and each variable with survival.

RESULTS

Among the 2715 participants diagnosed with cancer cachexia, 1592 (58.6%) were male, and the mean (SD) age was 58.8 (11.7) years. The optimal cutoff point for hemoglobin as a predictor of cancer cachexia mortality was 140 g/L for males and 101 g/L for females in our research. The decrease in hemoglobin was positively correlated with all-cause mortality. These associations were consistent across cancer subtypes. In the multivariable analysis, after adjusting for sex, age, TNM stage, tumor type, radiotherapy, chemotherapy, Karnofsky performance status score, and other factors, patients diagnosed with cancer cachexia who had low hemoglobin levels were more likely to have a worse prognosis (HR 2.40; 95% CI, 1.12-1.51).

CONCLUSION

Our results suggested that the proposed hemoglobin cutoff point would be valuable for prognostic prediction in patients with cancer cachexia, especially for long-term prognosis.

Guidelines on the intraoperative transfusion of red blood cells: a protocol for systematic review

INTRODUCTION

A significant proportion of red blood cell (RBC) transfusions are administered intraoperatively; yet there is limited evidence to guide transfusion decisions in this setting. The objective of this systematic review is to explore the availability, quality and content of clinical practice guidelines (CPGs) reporting on the indication for allogenic RBC transfusion during surgery.

METHODS

Major electronic databases (MEDLINE, EMBASE and CINAHL), guideline clearinghouses and Google Scholar, will be systematically searched from inception to January 2019 for CPGs pertaining to indications for intraoperative allogenic RBC transfusion. Characteristics of eligible guidelines will be reported in a summary table. The AGREE II instrument will be used to appraise the quality of identified guidelines. Recommendations advising on indications for intraoperative RBC transfusion will be manually extracted and presented to allow for comparison of similarities and/or discrepancies in the literature.

ETHICS AND DISSEMINATION

The results of this systematic review will be disseminated through relevant conferences and peer-reviewed journals.

TRIAL REGISTRATION NUMBER

CRD42018111487.

The Liver and Small Intestine Can Partly Compensate Severe Normovolemic Hemodilution in a Rat Model

BACKGROUND

Knowing the individual critical hematocrit for every organ is essential in operative scenarios in which extensive blood losses are expected. In the past, experimental settings were very heterogeneous resulting in the publication of widely differing values even for one organ in the same species. This study aimed to investigate the compensatory capacity of the liver and the small intestine in a rat model of severe normovolemic hemodilution.

MATERIALS AND METHODS

Male rats were subjected to a stepwise hemodilution with a succinylated gelatin-containing solution to a final hematocrit of 10%, being observed for additional 150 min. During the course of the experiment, blood glucose and L-lactate, as well as D-lactate and intestinal fatty acid-binding protein-2 measurements, were performed eight times in total. The amino acids alanine and glutamine were measured during dilution and at the end of the experiment (four times in total). Hemodilutional effects on the blood and oxygen supply of the liver and the small intestine were measured in a minimally invasive manner.

RESULTS

In the liver and the small intestine, there were no substantial changes in the blood flow of the microcirculation. Plasma glucose and lactate levels rose transiently, whereas lactate values did not exceed the upper threshold of aerobic metabolism. Plasma levels of the amino acids alanine and glutamine rose significantly and stayed elevated, whereas D-lactate and intestinal fatty acid-binding protein-2 were not significantly increased at any point during the whole experimental time compared to the initial value.

CONCLUSIONS

Severe hemodilution with a succinylated gelatin-containing solution is tolerated at a profoundly low hematocrit value of 10% during the experimental phase of 150 min.

Pathogenesis and Treatment Options of Cancer Related Anemia: Perspective for a Targeted Mechanism-Based Approach

Cancer-related anemia (CRA) is a common sign occurring in more than 30% of cancer patients at diagnosis before the initiation of antineoplastic therapy. CRA has a relevant influence on survival, disease progression, treatment efficacy, and the patients' quality of life. It is more often detected in patients with advanced stage disease, where it represents a specific symptom of the neoplastic disease, as a consequence of chronic inflammation. In fact, CRA is characterized by biological and hematologic features that resemble those described in anemia associated to chronic inflammatory disease. Proinflammatory cytokine, mainly IL-6, which are released by both tumor and immune cells, play a pivotal action in CRA etiopathogenesis: they promote alterations in erythroid progenitor proliferation, erythropoietin (EPO) production, survival of circulating erythrocytes, iron balance, redox status, and energy metabolism, all of which can lead to anemia. The discovery of hepcidin allowed a greater knowledge of the relationships between immune cells, iron metabolism, and anemia in chronic inflammatory diseases. Additionally, chronic inflammation influences a compromised nutritional status, which in turn might induce or contribute to CRA. In the present review we examine the multifactorial pathogenesis of CRA discussing the main and novel mechanisms by which immune, nutritional, and metabolic components affect its onset and severity. Moreover, we analyze the status of the art and the perspective for the treatment of CRA. Notably, despite the high incidence and clinical relevance of CRA, controlled clinical studies testing the most appropriate treatment for CRA are scarce, and its management in clinical practice remains challenging. The present review may be useful to indicate the development of an effective approach based on a detailed assessment of all factors potentially involved in the pathogenesis of CRA. This mechanism-based approach is essential for clinicians to plan a safe, targeted, and successful therapy, thereby promoting a relevant amelioration of patients' quality of life.

Transfusion Decision Making in Pediatric Critical Illness

Transfusion decision making (TDM) in the critically ill requires consideration of: (1) anemia tolerance, which is linked to active pathology and to physiologic reserve, (2) differences in donor RBC physiology from that of native RBCs, and (3) relative risk from anemia-attributable oxygen delivery failure vs hazards of transfusion, itself. Current approaches to TDM (e.g. hemoglobin thresholds) do not: (1) differentiate between patients with similar anemia, but dissimilar pathology/physiology, and (2) guide transfusion timing and amount to efficacy-based goals (other than resolution of hemoglobin thresholds). Here, we explore approaches to TDM that address the above gaps.

Hemodynamic coherence and the rationale for monitoring the microcirculation

This article presents a personal viewpoint of the shortcoming of conventional hemodynamic resuscitation procedures in achieving organ perfusion and tissue oxygenation following conditions of shock and cardiovascular compromise, and why it is important to monitor the microcirculation in such conditions. The article emphasizes that if resuscitation procedures are based on the correction of systemic variables, there must be coherence between the macrocirculation and microcirculation if systemic hemodynamic-driven resuscitation procedures are to be effective in correcting organ perfusion and oxygenation. However, in conditions of inflammation and infection, which often accompany states of shock, vascular regulation and compensatory mechanisms needed to sustain hemodynamic coherence are lost, and the regional circulation and microcirculation remain in shock. We identify four types of microcirculatory alterations underlying the loss of hemodynamic coherence: type 1, heterogeneous microcirculatory flow; type 2, reduced capillary density induced by hemodilution and anemia; type 3, microcirculatory flow reduction caused by vasoconstriction or tamponade; and type 4, tissue edema. These microcirculatory alterations can be observed at the bedside using direct visualization of the sublingual microcirculation with hand-held vital microscopes. Each of these alterations results in oxygen delivery limitation to the tissue cells despite the presence of normalized systemic hemodynamic variables. Based on these concepts, we propose how to optimize the volume of fluid to maximize the oxygen-carrying capacity of the microcirculation to transport oxygen to the tissues.