Role of iron in anaemic critically ill patients: it's time to investigate!

Iron Metabolism in the Recovery Phase of Critical Illness with a Focus on Sepsis

Iron is an essential nutrient for humans and microbes, such as bacteria. Iron deficiency commonly occurs in critically ill patients, but supplementary iron therapy is not considered during the acute phase of critical illness since it increases iron availability for invading microbes and oxidative stress. However, persistent iron deficiency in the recovery phase is harmful and has potential adverse outcomes such as cognitive dysfunction, fatigue, and cardiopulmonary dysfunction. Therefore, it is important to treat iron deficiency quickly and efficiently. This article reviews current knowledge about iron-related biomarkers in critical illness with a focus on patients with sepsis, and provides possible criteria to guide decision-making for iron supplementation in the recovery phase of those patients.

Iron deficiency diagnosed using hepcidin on critical care discharge is an independent risk factor for death and poor quality of life at one year: an observational prospective study on 1161 patients

Background

Iron deficiency is difficult to diagnose in critically ill patients, but may be frequent and may impair recovery. Measurement of hepcidin could help in the diagnosis of iron deficiency. We aim to assess if iron deficiency diagnosed using hepcidin is associated with poorer outcome one year after an intensive care unit stay.

Methods

We used the prospective FROG-ICU, multicentre (n = 28 ICUs), observational cohort study of critically ill survivors followed up one year after intensive care unit discharge. Iron deficiency was defined as hepcidin < 20 ng/l, ferritin < 100 ng/l or soluble transferrin receptor (sTfR)/log(ferritin) > 0.8, measured in blood drawn at intensive care unit discharge. Main outcomes were one-year all-cause mortality and poor quality of life (defined as a Short Form 36 (SF-36) score below the median).

Results

Among the 2087 patients in the FROG-ICU cohort, 1570 were discharged alive and 1161 had a blood sample available at intensive care unit discharge and were included in the analysis. Using hepcidin, 429 (37%) patients had iron deficiency, compared to 72 (6%) using ferritin alone and 151 (13%) using the sTfR/log(ferritin) ratio. Iron deficiency diagnosed according to low hepcidin was an independent predictor of one-year mortality (OR 1.51 (1.10–2.08)) as was high sTfR/log ferritin ratio (OR = 1.95 (1.27–3.00)), but low ferritin was not. Severe ID, defined as hepcidin < 10 ng/l, was also an independent predictor of poor one-year physical recovery (1.58 (1.01–2.49)).

Conclusions

Iron deficiency, diagnosed using hepcidin, is very frequent at intensive care unit discharge and is associated with increased one-year mortality and poorer physical recovery. Whether iron treatment may improve these outcomes remains to be investigated.

Electronic supplementary material

The online version of this article (10.1186/s13054-018-2253-0) contains supplementary material, which is available to authorized users.

Serum iron levels are an independent predictor of in-hospital mortality of critically ill patients: a retrospective, single-institution study

Objective

This study aimed to examine the relationship between serum iron levels and in-hospital mortality in critically ill patients.

Methods

We retrospectively studied 250 critically ill patients who received treatment at the intensive care unit between June 2015 and May 2017. Blood chemistry and hepatic and renal function were measured. Kaplan–Meier survival curves were plotted according to serum iron levels. Correlations between serum iron levels and other variables were analyzed.

Results

A total of 165 (66.0%) patients had abnormally low serum iron levels (<10.6 μmol/L). Patients who died during hospitalization had markedly higher Acute Physiology and Chronic Health Evaluation II scores and significantly lower serum iron levels compared with those who survived. Cumulative survival was significantly lower in patients with low serum iron levels than in those with normal serum iron levels in subgroup analysis of older patients (n = 192). Multivariate regression analysis showed that, after adjusting for relevant factors, low serum iron levels remained an independent risk for in-hospital mortality (odds ratio 2.014; 95% confidence interval 1.089, 3.725).

Conclusions

Low serum iron levels are present in a significant proportion of critically ill patients and are associated with higher in-hospital mortality, particularly in older patients.

Recommendations on RBC Transfusion in Infants and Children With Acquired and Congenital Heart Disease From the Pediatric Critical Care Transfusion and Anemia Expertise Initiative

OBJECTIVES

To present the recommendations and supporting literature for RBC transfusions in critically ill children with acquired and congenital heart disease developed by the Pediatric Critical Care Transfusion and Anemia Expertise Initiative.

DESIGN

Consensus conference series of 38 international, multidisciplinary experts in RBC transfusion management of critically ill children.

METHODS

Experts developed evidence-based and, when evidence was lacking, expert-based clinical recommendations and research priorities for RBC transfusions in critically ill children. The cardiac disease subgroup included three experts. Electronic searches were conducted using PubMed, EMBASE, and Cochrane Library databases from 1980 to May 2017. Agreement was obtained using the Research and Development/UCLA appropriateness method. Results were summarized using the Grading of Recommendations Assessment, Development, and Evaluation method.

RESULTS

Twenty-one recommendations were developed and reached agreement. For children with myocardial dysfunction and/or pulmonary hypertension, there is no evidence that transfusion greater than hemoglobin of 10 g/dL is beneficial. For children with uncorrected heart disease, we recommended maintaining hemoglobin greater than 7-9.0 g/dL depending upon their cardiopulmonary reserve. For stable children undergoing biventricular repairs, we recommend not transfusing if the hemoglobin is greater than 7.0 g/dL. For infants undergoing staged palliative procedures with stable hemodynamics, we recommend avoiding transfusions solely based upon hemoglobin, if hemoglobin is greater than 9.0 g/dL. We recommend intraoperative and postoperative blood conservation measures. There are insufficient data supporting shorter storage duration RBCs. The risks and benefits of RBC transfusions in children with cardiac disease requires further study.

CONCLUSIONS

We present RBC transfusion management recommendations for the critically ill child with cardiac disease. Clinical recommendations emphasize relevant hemoglobin thresholds, and research recommendations emphasize need for further understanding of physiologic and hemoglobin thresholds and alternatives to RBC transfusion in subpopulations lacking pediatric literature.

A multicenter, randomized clinical trial of IV iron supplementation for anemia of traumatic critical illness*

OBJECTIVE

To evaluate the efficacy of IV iron supplementation of anemic, critically ill trauma patients.

DESIGN

Multicenter, randomized, single-blind, placebo-controlled trial.

SETTING

Four trauma ICUs.

PATIENTS

Anemic (hemoglobin < 12 g/dL) trauma patients enrolled within 72 hours of ICU admission and with an expected ICU length of stay of more than or equal to 5 days.

INTERVENTIONS

Randomization to iron sucrose 100 mg IV or placebo thrice weekly for up to 2 weeks.

MEASUREMENTS AND MAIN RESULTS

A total of 150 patients were enrolled. Baseline iron markers were consistent with functional iron deficiency: 134 patients (89.3%) were hypoferremic, 51 (34.0%) were hyperferritinemic, and 64 (42.7%) demonstrated iron-deficient erythropoiesis as evidenced by an elevated erythrocyte zinc protoporphyrin concentration. The median baseline transferrin saturation was 8% (range, 2-58%). In the subgroup of patients who received all six doses of study drug (n = 57), the serum ferritin concentration increased significantly for the iron as compared with placebo group on both day 7 (808.0 ng/mL vs 457.0 ng/mL, respectively, p < 0.01) and day 14 (1,046.0 ng/mL vs 551.5 ng/mL, respectively, p < 0.01). There was no significant difference between groups in transferrin saturation, erythrocyte zinc protoporphyrin concentration, hemoglobin concentration, or packed RBC transfusion requirement. There was no significant difference between groups in the risk of infection, length of stay, or mortality.

CONCLUSIONS

Iron supplementation increased the serum ferritin concentration significantly, but it had no discernible effect on transferrin saturation, iron-deficient erythropoiesis, hemoglobin concentration, or packed RBC transfusion requirement. Based on these data, routine IV iron supplementation of anemic, critically ill trauma patients cannot be recommended (NCT 01180894).

Prevalence of iron deficiency on ICU discharge and its relation with fatigue: a multicenter prospective study

INTRODUCTION

Prevalence of iron deficiency (ID) at intensive care (ICU) admission is around 25 to 40%. Blood losses are important during ICU stay, leading to iron losses, but prevalence of ID at ICU discharge is unknown. ID has been associated with fatigue and muscular weakness, and may thus impair post-ICU rehabilitation. This study assessed ID prevalence at ICU discharge, day 28 (D28) and six months (M6) after and its relation with fatigue.

METHODS

We conducted this prospective, multicenter observational study at four University hospitals ICUs. Anemic (hemoglobin (Hb) less than 13 g/dL in male and less than 12 g/dL in female) critically ill adult patients hospitalized for at least five days had an iron profile taken at discharge, D28 and M6. ID was defined as ferritin less than 100 ng/L or less than 300 ng/L together with a transferrin saturation less than 20%. Fatigue was assessed by numerical scale and the Multidimensional Fatigue Inventory-20 questionnaire at D28 and M6 and muscular weakness by a hand grip test at ICU discharge.

RESULTS

Among 107 patients (men 77%, median (IQR) age 63 (48 to 73) years) who had a complete iron profile at ICU discharge, 9 (8.4%) had ID. At ICU discharge, their hemoglobin concentration (9.5 (87.7 to 10.3) versus 10.2 (92.2 to 11.7) g/dL, P =0.09), hand grip strength (52.5 (30 to 65) versus 49.5 (15.5 to 67.7)% of normal value, P =0.61) and visual analog scale fatigue scale (57 (40 to 80) versus 60 (47.5 to 80)/100, P =0.82) were not different from non-ID patients. At D28 (n =80 patients) and M6 (n =78 patients), ID prevalence increased (to 25 and 35% respectively) while anemia prevalence decreased (from 100% to 80 and 25% respectively, P <0.0001). ID was associated with increased fatigue at D28, after adjustment for main confounding factors, including anemia (regression coefficient (95%CI), 3.19 (0.74 to 5.64), P =0.012). At M6, this association disappeared.

CONCLUSIONS

The prevalence of ID increases from 8% at discharge to 35% six months after prolonged ICU stay (more than five days). ID was associated with increased fatigue, independently of anemia, at D28.

The use of erythropoiesis-stimulating agents in the intensive care unit

Anemia is common in critically ill patients, but treatment with red blood cell transfusions can have unwanted effects. Limiting the occurrence and severity of anemia by using erythropoietic agents (iron and/or recombinant erythropoietin), therefore, remains an attractive option during the intensive care unit stay but also after hospital discharge. Moreover, these agents may have additional beneficial properties. In this article the authors review the rationale for the administration of iron and/or erythropoietin in critically ill patients.

Prevention of siderophore- mediated gut-derived sepsis due to P. aeruginosa can be achieved without iron provision by maintaining local phosphate abundance: role of pH

Background

During extreme physiological stress, the intestinal tract can be transformed into a harsh environment characterized by regio- spatial alterations in oxygen, pH, and phosphate concentration. When the human intestine is exposed to extreme medical interventions, the normal flora becomes replaced by pathogenic species whose virulence can be triggered by various physico-chemical cues leading to lethal sepsis. We previously demonstrated that phosphate depletion develops in the mouse intestine following surgical injury and triggers intestinal P. aeruginosa to express a lethal phenotype that can be prevented by oral phosphate ([Pi]) supplementation.

Results

In this study we examined the role of pH in the protective effect of [Pi] supplementation as it has been shown to be increased in the distal gut following surgical injury. Surgically injured mice drinking 25 mM [Pi] at pH 7.5 and intestinally inoculated with P. aeruginosa had increased mortality compared to mice drinking 25 mM [Pi] at pH 6.0 (p < 0.05). This finding was confirmed in C. elegans. Transcriptional analysis of P. aeruginosa demonstrated enhanced expression of various genes involved in media alkalization at pH 6.0 and a global increase in the expression of all iron-related genes at pH 7.5. Maintaining the pH at 6.0 via phosphate supplementation led to significant attenuation of iron-related genes as demonstrated by microarray and confirmed by QRT-PCR analyses.

Conclusion

Taken together, these data demonstrate that increase in pH in distal intestine of physiologically stressed host colonized by P. aeruginosa can lead to the expression of siderophore-related virulence in bacteria that can be prevented without providing iron by maintaining local phosphate abundance at pH 6.0. This finding is particularly important as provision of exogenous iron has been shown to have untoward effects when administered to critically ill and septic patients. Given that phosphate, pH, and iron are near universal cues that dictate the virulence status of a broad range of microorganisms relevant to serious gut origin infection and sepsis in critically ill patients, the maintenance of phosphate and pH at appropriate physiologic levels to prevent virulence activation in a site specific manner can be considered as a novel anti-infective therapy in at risk patients.

Change of transferrin sialylation differs between mild sepsis and severe sepsis and septic shock

OBJECTIVE AND DESIGN

To investigate the association between the severity of sepsis and changes in sialylation of serum proteins we have conducted a single center pilot study.

SUBJECTS AND METHODS

Sialylation of transferrin (with enzyme-linked lectin assay-ELLA) and total serum proteins (with colorimetric assay) as well as serum iron and transferrin levels were measured in 27 patients with sepsis through the first eight days of the disease.

RESULTS

Total serum sialylation increased in the first two days, transferrin sialylation decreased, while serum iron and transferrin fell. Patients who developed severe sepsis had either a small or marked change in transferrin sialylation while in patients with mild sepsis sialylation decreased moderately.

CONCLUSION

We hypothesize that the change in transferrin sialylation could be a reflection of the intensity of inflammatory response which is insufficient if under-expressed and detrimental if over-expressed. This new feature is a potential marker of sepsis severity early in the disease.

Nutritional aspects of care

Malnutrition in the oral and maxillofacial surgery surgical patient can have critical implications in the overall well-being and prognosis of the long-term, hospitalized, ill patient. The OMS should be capable of assessing the patient's nutritional status and nutritional requirements and developing appropriate recommendations for proper nutritional management. Knowledge of the various modalities of nutritional support should be readily available to the OMS practitioner.

RAPID ALTERATIONS IN TRANSFERRIN SIALYLATION DURING SEPSIS

The inflammatory process is associated with alterations in iron metabolism. Transferrin, an acute-phase N-glycosylated glycoprotein, plays an important role in iron transport. Human serum transferrin contains two biantennary glycans, each consisting of 0 to 4 molecules of sialic acid (SA); its SA content is heterogeneous with high concentration of tetrasialotransferrin (4SA) and low amounts of disialo-, trisialo-, penta-, and hexasialotransferrin. The hepatic uptake of iron is greater for desialylated transferrin isoforms (disialotransferrin) than for the other forms. We hypothesized that serum levels of carbohydrate-deficient transferrin (CDT, disialotransferrin) may increase rapidly in septic patients. Blood samples were obtained from critically ill patients with (n = 15) and without (n = 14) documented sepsis and compared with healthy volunteers. The different forms of transferrin were studied by capillary zone electrophoresis; SA concentrations were measured by enzymatic colorimetric assay. There was a significant increase in the proportion of CDT in septic compared with nonseptic patients and volunteers (18.3% [1.3-30.5] vs. 0.7% [0.5-0.9]; P < 0.01 and 0.9% [0.5-1.1]; P < 0.05). Conversely, tri- and tetrasialotransferrin levels were lower in septic patients. Total and free SA concentrations were significantly higher in septic patients than in healthy volunteers. In a sheep model of septic shock secondary to peritonitis, serum free SA was already increased after 15 h. Sepsis is associated with decreased SA content on circulating transferrin and with an increase in blood free SA concentrations. In view of these rapid modifications and the long half-life of transferrin, the most likely explanation is degradation of transferrin by neuraminidase. Further studies including measurement of blood neuraminidase concentration and activity are needed to understand the process and exact role of SA decrease in septic patients.