Systematic Review and Meta-Analysis of Effects of Transfusion on Hemodynamic and Oxygenation Variables

LASSO-Based Machine Learning Algorithm for Prediction of PICS Associated with Sepsis

Introduction

This study aims to establish a comprehensive, multi-level approach for tackling tropical diseases by proactively anticipating and managing Persistent Inflammation, Immunosuppression, and Catabolism Syndrome (PICS) within the initial 14 days of Intensive Care Unit (ICU) admission. The primary objective is to amalgamate a diverse array of indicators and pathogenic microbial data to pinpoint pivotal predictive variables, enabling effective intervention specifically tailored to the context of tropical diseases.

Methods

A focused analysis was conducted on 1733 patients admitted to the ICU between December 2016 and July 2019. Utilizing the Least Absolute Shrinkage and Selection Operator (LASSO) regression, disease severity and laboratory indices were scrutinized. The identified variables served as the foundation for constructing a predictive model designed to forecast the occurrence of PICS.

Results

Among the subjects, 13.79% met the diagnostic criteria for PICS, correlating with a mortality rate of 38.08%. Key variables, including red-cell distribution width coefficient of variation (RDW-CV), hemofiltration (HF), mechanical ventilation (MV), Norepinephrine (NE), lactic acidosis, and multiple-drug resistant bacteria (MDR) infection, were identified through LASSO regression. The resulting predictive model exhibited a robust performance with an Area Under the Curve (AUC) of 0.828, an accuracy of 0.862, and a specificity of 0.977. Subsequent validation in an independent cohort yielded an AUC of 0.848.

Discussion

The acquisition of RDW-CV, HF requirement, MV requirement, NE requirement, lactic acidosis, and MDR upon ICU admission emerges as a pivotal factor for prognosticating PICS onset in the context of tropical diseases. This study highlights the potential for significant improvements in clinical outcomes through the implementation of timely and targeted interventions tailored specifically to the challenges posed by tropical diseases.

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.

Haemoglobin value and red blood cell transfusions in prolonged weaning from mechanical ventilation: a retrospective observational study

INTRODUCTION

The role of haemoglobin (Hb) value and red blood cell (RBC) transfusions in prolonged weaning from mechanical ventilation (MV) is still controversial. Pathophysiological considerations recommend a not too restrictive transfusion strategy, whereas adverse effects of transfusions are reported. We aimed to investigate the association between Hb value, RBC transfusion and clinical outcome of patients undergoing prolonged weaning from MV.

METHODS

We performed a retrospective, single-centred, observational study including patients being transferred to a specialised weaning unit. Data on demographic characteristics, comorbidities, current and past medical history and the current course of treatment were collected. Weaning failure and mortality were chosen as primary and secondary endpoint, respectively. Differences between transfused and non-transfused patients were analysed. To evaluate the impact of different risk factors including Hb value and RBC transfusion on clinical outcome, a multivariate logistic regression analysis was used.

RESULTS

184 patients from a specialised weaning unit were analysed, of whom 36 (19.6%) failed to be weaned successfully. In-hospital mortality was 18.5%. 90 patients (48.9%) required RBC transfusion during the weaning process, showing a significantly lower Hb value (g/L) (86.3±5.3) than the non-transfusion group (95.8±10.5). In the multivariate regression analysis (OR 3.24; p=0.045), RBC transfusion was associated with weaning failure. However, the transfusion group had characteristics indicating that these patients were still in a more critical state of disease.

CONCLUSIONS

In our analysis, the need for RBC transfusion was independently associated with weaning failure. However, it is unclear whether the transfusion itself should be considered an independent risk factor or an additional symptom of a persistent critical patient condition.

Pathophysiology, mechanisms, and managements of tissue hypoxia

Oxygen is needed to generate aerobic adenosine triphosphate and energy that is required to support vital cellular functions. Oxygen delivery (DO₂) to the tissues is determined by convective and diffusive processes. The ability of the body to adjust oxygen extraction (ERO₂) in response to changes in DO₂ is crucial to maintain constant tissue oxygen consumption (VO₂). The capability to increase ERO₂ is the result of the regulation of the circulation and the effects of the simultaneous activation of both central and local factors. The endothelium plays a crucial role in matching tissue oxygen supply to demand in situations of acute drop in tissue oxygenation. Tissue oxygenation is adequate when tissue oxygen demand is met. When DO₂ is severely compromised, a critical DO₂ value is reached below which VO₂ falls and becomes dependent on DO₂, resulting in tissue hypoxia. The different mechanisms of tissue hypoxia are circulatory, anaemic, and hypoxic, characterised by a diminished DO₂ but preserved capacity of increasing ERO₂. Cytopathic hypoxia is another mechanism of tissue hypoxia that is due to impairment in mitochondrial respiration that can be observed in septic conditions with normal overall DO₂. Sepsis induces microcirculatory alterations with decreased functional capillary density, increased number of stopped-flow capillaries, and marked heterogeneity between the areas with large intercapillary distance, resulting in impairment of the tissue to extract oxygen and to satisfy the increased tissue oxygen demand, leading to the development of tissue hypoxia. Different therapeutic approaches exist to increase DO₂ and improve microcirculation, such as fluid therapy, transfusion, vasopressors, inotropes, and vasodilators. However, the effects of these agents on microcirculation are quite variable.

Generation and Export of Red Blood Cell ATP in Health and Disease

Metabolic homeostasis in animals depends critically on evolved mechanisms by which red blood cell (RBC) hemoglobin (Hb) senses oxygen (O₂) need and responds accordingly. The entwined regulation of ATP production and antioxidant systems within the RBC also exploits Hb-based O₂-sensitivity to respond to various physiologic and pathophysiologic stresses. O₂ offloading, for example, promotes glycolysis in order to generate both 2,3-DPG (a negative allosteric effector of Hb O₂ binding) and ATP. Alternatively, generation of the nicotinamide adenine dinucleotide phosphate (NADPH) critical for reducing systems is favored under the oxidizing conditions of O₂ abundance. Dynamic control of ATP not only ensures the functional activity of ion pumps and cellular flexibility, but also contributes to the availability of vasoregulatory ATP that can be exported when necessary, for example in hypoxia or upon RBC deformation in microvessels. RBC ATP export in response to hypoxia or deformation dilates blood vessels in order to promote efficient O₂ delivery. The ability of RBCs to adapt to the metabolic environment via differential control of these metabolites is impaired in the face of enzymopathies [pyruvate kinase deficiency; glucose-6-phosphate dehydrogenase (G6PD) deficiency], blood banking, diabetes mellitus, COVID-19 or sepsis, and sickle cell disease. The emerging availability of therapies capable of augmenting RBC ATP, including newly established uses of allosteric effectors and metabolite-specific additive solutions for RBC transfusates, raises the prospect of clinical interventions to optimize or correct RBC function via these metabolite delivery mechanisms.

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.

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

Background

Guidelines recommend a restrictive red blood cell transfusion strategy based on hemoglobin (Hb) concentrations in critically ill patients. We hypothesized that the arterial-venous oxygen difference (A-V O_2diff), a surrogate for the oxygen delivery to consumption ratio, could provide a more personalized approach to identify patients who may benefit from transfusion.

Methods

A prospective observational study including 177 non-bleeding adult patients with a Hb concentration of 7.0–10.0 g/dL within 72 h after ICU admission. The A-V O_2diff, central venous oxygen saturation (ScvO₂), and oxygen extraction ratio (O₂ER) were noted when a patient’s Hb was first within this range. Transfusion decisions were made by the treating physician according to institutional policy. We used the median A-V O_2diff value in the study cohort (3.7 mL) to classify the transfusion strategy in each patient as “appropriate” (patient transfused when the A-V O_2diff > 3.7 mL or not transfused when the A-V O_2diff ≤ 3.7 mL) or “inappropriate” (patient transfused when the A-V O_2diff ≤ 3.7 mL or not transfused when the A-V O_2diff > 3.7 mL). The primary outcome was 90-day mortality.

Results

Patients managed with an “appropriate” strategy had lower mortality rates (23/96 [24%] vs. 36/81 [44%]; p = 0.004), and an “appropriate” strategy was independently associated with reduced mortality (hazard ratio [HR] 0.51 [95% CI 0.30–0.89], p = 0.01). There was a trend to less acute kidney injury with the “appropriate” than with the “inappropriate” strategy (13% vs. 26%, p = 0.06), and the Sequential Organ Failure Assessment (SOFA) score decreased more rapidly (p = 0.01). The A-V O_2diff, but not the ScvO₂, predicted 90-day mortality in transfused (AUROC = 0.656) and non-transfused (AUROC = 0.630) patients with moderate accuracy. Using the ROC curve analysis, the best A-V O_2diff cutoffs for predicting mortality were 3.6 mL in transfused and 3.5 mL in non-transfused patients.

Conclusions

In anemic, non-bleeding critically ill patients, transfusion may be associated with lower 90-day mortality and morbidity in patients with higher A-V O_2diff.

Trial registration

ClinicalTrials.gov, NCT03767127. Retrospectively registered on 6 December 2018.