Transfusion of red blood cells in venoarterial extracorporeal membrane oxygenation: A multicenter retrospective observational cohort study.

BACKGROUND: Evidence-based recommendations for transfusion in patients with venoarterial extracorporeal membrane oxygenation (VA ECMO) are scarce. The current literature is limited to single-center studies with small sample sizes, therefore complicating generalizability. This study aims to create an overview of red blood cell (RBC) transfusion in VA ECMO patients. METHODS: This international mixed-method study combined a survey with a retrospective observational study in 16 centers. The survey inventoried local transfusion guidelines. Additionally, retrospective data of all adult patients with a VA ECMO run >24 h (January 2018 until July 2019) was collected of patient, ECMO, outcome, and daily transfusion parameters. All patients that received VA ECMO for primary cardiac support were included, including surgical (i.e., post-cardiotomy) and non-surgical (i.e., myocardial infarction) indications. The primary outcome was the number of RBC transfusions per day and in total. Univariable logistic regressions and a generalized linear mixed model (GLMM) were performed to assess factors associated with RBC transfusion. RESULTS: Out of 419 patients, 374 (89%) received one or more RBC transfusions. During a median ECMO run of 5 days (1st-3rd quartile 3-8), patients received a median total of eight RBC units (1st-3rd quartile 3-17). A lower hemoglobin (Hb) prior to ECMO, longer ECMO-run duration, and hemorrhage were associated with RBC transfusion. After correcting for duration and hemorrhage using a GLMM, a different transfusion trend was found among the regimens. No unadjusted differences were found in overall survival between either transfusion status or the different regimens, which remained after adjustment for potential confounders. CONCLUSION: RBC transfusion in patients on VA ECMO is very common. The sum of RBC transfusions increases rapidly after ECMO initiation, and is dependent on the Hb threshold applied. This study supports the rationale for prospective studies focusing on indications and thresholds for RBC transfusion.

Plasma Transfusion and Procoagulant Product Administration in Extracorporeal Membrane Oxygenation: A Secondary Analysis of an International Observational Study on Current Practices.

OBJECTIVES: To achieve optimal hemostatic balance in patients on extracorporeal membrane oxygenation (ECMO), a liberal transfusion practice is currently applied despite clear evidence. We aimed to give an overview of the current use of plasma, fibrinogen concentrate, tranexamic acid (TXA), and prothrombin complex concentrate (PCC) in patients on ECMO. DESIGN: A prespecified subanalysis of a multicenter retrospective study. Venovenous (VV)-ECMO and venoarterial (VA)-ECMO are analyzed as separate populations, comparing patients with and without bleeding and with and without thrombotic complications. SETTING: Sixteen international ICUs. PATIENTS: Adult patients on VA-ECMO or VV-ECMO. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Of 420 VA-ECMO patients, 59% (n = 247) received plasma, 20% (n = 82) received fibrinogen concentrate, 17% (n = 70) received TXA, and 7% of patients (n = 28) received PCC. Fifty percent of patients (n = 208) suffered bleeding complications and 27% (n = 112) suffered thrombotic complications. More patients with bleeding complications than patients without bleeding complications received plasma (77% vs. 41%, p < 0.001), fibrinogen concentrate (28% vs 11%, p < 0.001), and TXA (23% vs 10%, p < 0.001). More patients with than without thrombotic complications received TXA (24% vs 14%, p = 0.02, odds ratio 1.75) in VA-ECMO, where no difference was seen in VV-ECMO. Of 205 VV-ECMO patients, 40% (n = 81) received plasma, 6% (n = 12) fibrinogen concentrate, 7% (n = 14) TXA, and 5% (n = 10) PCC. Thirty-nine percent (n = 80) of VV-ECMO patients suffered bleeding complications and 23% (n = 48) of patients suffered thrombotic complications. More patients with than without bleeding complications received plasma (58% vs 28%, p < 0.001), fibrinogen concentrate (13% vs 2%, p < 0.01), and TXA (11% vs 2%, p < 0.01). CONCLUSIONS: The majority of patients on ECMO receive transfusions of plasma, procoagulant products, or antifibrinolytics. In a significant part of the plasma transfused patients, this was in the absence of bleeding or prolonged international normalized ratio. This poses the question if these plasma transfusions were administered for another indication or could have been avoided.

The interaction of thrombocytopenia, hemorrhage, and platelet transfusion in venoarterial extracorporeal membrane oxygenation: a multicenter observational study.

BACKGROUND: Thrombocytopenia, hemorrhage and platelet transfusion are common in patients supported with venoarterial extracorporeal membrane oxygenation (VA ECMO). However, current literature is limited to small single-center experiences with high degrees of heterogeneity. Therefore, we aimed to ascertain in a multicenter study the course and occurrence rate of thrombocytopenia, and to assess the association between thrombocytopenia, hemorrhage and platelet transfusion during VA ECMO. METHODS: This was a sub-study of a multicenter (N = 16) study on transfusion practices in patients on VA ECMO, in which a retrospective cohort (Jan-2018-Jul-2019) focusing on platelets was selected. The primary outcome was thrombocytopenia during VA ECMO, defined as mild (100-150·109/L), moderate (50-100·109/L) and severe (< 50·109/L). Secondary outcomes included the occurrence rate of platelet transfusion, and the association between thrombocytopenia, hemorrhage and platelet transfusion, assessed through mixed-effect models. RESULTS: Of the 419 patients included, median platelet count at admission was 179·109/L. During VA ECMO, almost all (N = 398, 95%) patients developed a thrombocytopenia, of which a significant part severe (N = 179, 45%). One or more platelet transfusions were administered in 226 patients (54%), whereas 207 patients (49%) suffered a hemorrhagic event during VA ECMO. In non-bleeding patients, still one in three patients received a platelet transfusion. The strongest association to receive a platelet transfusion was found in the presence of severe thrombocytopenia (adjusted OR 31.8, 95% CI 17.9-56.5). After including an interaction term of hemorrhage and thrombocytopenia, this even increased up to an OR of 110 (95% CI 34-360). CONCLUSIONS: Thrombocytopenia has a higher occurrence than is currently recognized. Severe thrombocytopenia is strongly associated with platelet transfusion. Future studies should focus on the etiology of severe thrombocytopenia during ECMO, as well as identifying indications and platelet thresholds for transfusion in the absence of bleeding. TRIAL REGISTRATION: This study was registered at the Netherlands Trial Registry at February 26th, 2020 with number NL8413 and can currently be found at https://trialsearch.who.int/Trial2.aspx?TrialID=NL8413.

RBC Transfusion in Venovenous Extracorporeal Membrane Oxygenation: A Multicenter Cohort Study.

OBJECTIVES: In the general critical care patient population, restrictive transfusion regimen of RBCs has been shown to be safe and is yet implemented worldwide. However, in patients on venovenous extracorporeal membrane oxygenation, guidelines suggest liberal thresholds, and a clear overview of RBC transfusion practice is lacking. This study aims to create an overview of RBC transfusion in venovenous extracorporeal membrane oxygenation. DESIGN: Mixed method approach combining multicenter retrospective study and survey. SETTING: Sixteen ICUs worldwide. PATIENTS: Patients receiving venovenous extracorporeal membrane oxygenation between January 2018 and July 2019. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: The primary outcome was the proportion receiving RBC, the amount of RBC units given daily and in total. Furthermore, the course of hemoglobin over time during extracorporeal membrane oxygenation was assessed. Demographics, extracorporeal membrane oxygenation characteristics, and patient outcome were collected. Two-hundred eight patients received venovenous extracorporeal membrane oxygenation, 63% male, with an age of 55 years (45-62 yr), mainly for acute respiratory distress syndrome. Extracorporeal membrane oxygenation duration was 9 days (5-14 d). Prior to extracorporeal membrane oxygenation, hemoglobin was 10.8 g/dL (8.9-13.0 g/dL), decreasing to 8.7 g/dL (7.7-9.8 g/dL) during extracorporeal membrane oxygenation. Nadir hemoglobin was lower on days when a transfusion was administered (8.1 g/dL [7.4-9.3 g/dL]). A vast majority of 88% patients received greater than or equal to 1 RBC transfusion, consisting of 1.6 U (1.3-2.3 U) on transfusion days. This high transfusion occurrence rate was also found in nonbleeding patients (81%). Patients with a liberal transfusion threshold (hemoglobin > 9 g/dL) received more RBC in total per transfusion day and extracorporeal membrane oxygenation day. No differences in survival, hemorrhagic and thrombotic complication rates were found between different transfusion thresholds. Also, 28-day mortality was equal in transfused and nontransfused patients. CONCLUSIONS: Transfusion of RBC has a high occurrence rate in patients on venovenous extracorporeal membrane oxygenation, even in nonbleeding patients. There is a need for future studies to find optimal transfusion thresholds and triggers in patients on extracorporeal membrane oxygenation.

Current challenges in the treatment of severe Clostridium difficile infection: early treatment potential of fecal microbiota transplantation.

Fecal microbiota transplantation (FMT) is a very effective treatment for recurrent Clostridium difficile infection (CDI). Less is known about the application of FMT as a curative treatment of severe or complicated CDI. In this review, we present and discuss evidence supporting the curative use of FMT in severe or complicated CDI. We performed a literature search in PubMed and Embase for studies on the curative use of FMT in severe or complicated CDI. In addition, we describe a patient with severe CDI not responding to initial antibiotic treatment, who was successfully treated with curative FMT. We found 23 reports (12 case reports; 11 case series) about FMT as treatment for severe or complicated CDI. The patients described all had severe or complicated CDI, did not respond to conventional CDI antibiotic treatment and received FMT as last resort treatment. Patients were treated with (sequential) FMT, whether or not followed by additional antibiotic treatment for CDI. FMT, with or without additional antibiotic CDI treatment, appears to be a promising curative treatment option in patients with severe and complicated CDI, or only complicated CDI, who do not respond sufficiently to conventional antibiotic treatment. Treatment with FMT should be considered in these patients before proceeding to emergency bowel surgery.

Expansion of effector T cells associated with decreased PD-1 expression in patients with indolent B cell lymphomas and chronic lymphocytic leukemia.

In patients with chronic lymphocytic leukemia (CLL), numbers of CD8 + CD45RA +/- CD27- effector T cells are expanded. We investigated whether this expansion is also present in other B cell malignancies and the possible mechanism underlying these changes. Whereas an increase in total CD4+and CD8+ T cell numbers was found only in CLL, numbers of CD4+ and CD8+ effector T cells were significantly increased in both CLL and indolent lymphoma, but not aggressive lymphoma and myeloma. Interestingly, PD-1 expression was decreased on effector T cells and inversely correlated with effector T cell numbers, suggesting a functional role for PD-1 in regulating T cell homeostasis. In vitro experiments revealed impaired up-regulation of PD-1 upon T cell activation in the presence of malignant but also healthy B cells. Our data suggest that in CLL and indolent lymphoma, the malignant B cells affect PD-1 expression on effector T cells, resulting in an expansion of these subsets.

Cytomegalovirus-induced effector T cells cause endothelial cell damage.

Human cytomegalovirus (CMV) infection has been linked to inflammatory diseases that involve vascular endothelial cell damage, but definitive proof for a direct cytopathic effect of CMV in these diseases is lacking. CMV infection is associated with a strong increase in both CD4(+) and CD8(+) T cells with constitutive effector functions that can perpetuate systemic inflammation. We investigated whether CMV-induced immune responses could lead to endothelial damage in humans. We found that terminally differentiated effector CD4(+) and CD8(+) T cells, formed during primary CMV infection and maintained throughout latency, express high levels of CX3CR1 and CXCR3. The ligands of these receptors, fractalkine and IP-10, respectively, are expressed by activated endothelial cells. Peripheral blood mononuclear cells (PBMC) stimulated with CMV antigen produced soluble factors that stimulated endothelial cells to produce both chemokines. Finally, effector cells migrated in a fractalkine- and IP-10-dependent fashion to activated endothelial cells and induced apoptosis in endothelial cells that were stimulated by supernatant from CMV-activated PBMC. Our findings offer an explanation for the accumulation of highly differentiated T cells near to the endothelium in CMV-infected individuals that may result in endothelial damage.

Circulating lymphocyte subsets in different clinical situations after renal transplantation.

Phenotypic characterization of T and B lymphocytes allows the discrimination of functionally different subsets. Here, we questioned whether changes in peripheral lymphocyte subset distribution reflect specific clinical and histopathological entities after renal transplantation. Sixty-five renal transplant recipients with either histologically proven (sub)clinical acute rejection or chronic allograft dysfunction, or without abnormalities were studied for their peripheral lymphocyte subset composition and compared with 15 healthy control individuals. Naive, memory and effector CD8(+) T-cell counts were measured by staining for CD27, CD28 and CD45RO/RA. In addition, we studied the CD25(+) CD4(+) T-cell population for its composition regarding regulatory Foxp3(+) CD45RO(+) CD127(-) cells and activated CD45RO(+) CD127(+) cells. Naive, non-switched and switched memory B cells were defined by staining for IgD and CD27. We found a severe decrease in circulating effector-type CD8(+) T cells in recipients with chronic allograft dysfunction at 5 years after transplantation. Percentages of circulating CD25(+) CD127(low) CD4(+) regulatory T cells after transplantation were reduced, but we could not detect any change in the percentage of CD127(+) CD45RO(+) CD4(+) activated T cells in patients at any time or condition after renal transplantation. Regardless of clinical events, all renal transplant recipients showed decreased total B-cell counts and a more differentiated circulating B-cell pool than healthy individuals. The changes in lymphocyte subset distribution probably reflect the chronic antigenic stimulation that occurs in these transplant recipients. To determine the usefulness of lymphocyte subset-typing in clinical practice, large cohort studies are necessary.

Molecular profiling of cytomegalovirus-induced human CD8+ T cell differentiation.

CD8+ T cells play a critical role in the immune response to viral pathogens. Persistent human cytomegalovirus (HCMV) infection results in a strong increase in the number of virus-specific, quiescent effector-type CD8+ T cells with constitutive cytolytic activity, but the molecular pathways involved in the induction and maintenance of these cells are unknown. We show here that HCMV infection induced acute and lasting changes in the transcriptomes of virus-reactive T cells collected from HCMV-seropositive patients at distinct stages of infection. Enhanced cell cycle and metabolic activity was restricted to the acute phase of the response, but at all stages, HCMV-specific CD8+ T cells expressed the Th1-associated transcription factors T-bet (TBX21) and eomesodermin (EOMES), in parallel with continuous expression of IFNG mRNA and IFN-γ-regulated genes. The cytolytic proteins granzyme B and perforin as well as the fractalkine-binding chemokine receptor CX3CR1 were found in virus-reactive cells throughout the response. During HCMV latency, virus-specific CD8+ T cells lacked the typical features of exhausted cells found in other chronic infections. Persistent effector cell traits together with the permanent changes in chemokine receptor usage of virus-specific, nonexhausted, long-lived CD8+ T cells may be crucial to maintain lifelong protection from HCMV reactivation.

Human cytomegalovirus induces systemic immune activation characterized by a type 1 cytokine signature.

Mechanisms underlying the onset and perpetuation of chronic immune activation in individuals without overt infectious or autoimmune diseases are unclear. Cytomegalovirus (CMV) is a persistent virus that induces a permanent increase of highly differentiated, interferon-gamma-secreting effector T cells. We hypothesized that, because of this increase, CMV also induces a systemic inflammatory response. We measured acute phase proteins, cytokines, and chemokines in serum samples from renal transplant recipients who developed a primary CMV infection and healthy CMV serum-positive or -negative individuals. Primary CMV infection induced a clear proinflammatory response that was maintained during latency. This response was characterized by increased levels of acute phase proteins, such as serum amyloid-A and C-reactive protein, and type 1 cytokines, such as interleukin-18, interferon-inducible protein-10, and interferon-gamma. This continuous activation of the immune system may play a role in the pathogenesis of chronic allograft rejection and potentially contribute to the acceleration of chronic diseases.

Cytomegalovirus infection reduces telomere length of the circulating T cell pool.

Short telomeres of circulating leukocytes are a risk factor for age-related diseases, such as atherosclerosis, but the exact mechanisms generating variations in telomere length are unknown. We hypothesized that induction of differentiated T cells during chronic CMV infection would affect T cell telomere length. To test this, we measured the amount of differentiated T cells and telomere length of lymphocytes during primary CMV infection as well as CMV-seropositive and -seronegative healthy individuals. After primary CMV infection, we observed an increase in highly differentiated cells that coincided with a steep drop in telomere length. Moreover, we found in a cohort of 159 healthy individuals that telomere shortening was more rapid in CMV-seropositive individuals and correlated with the amount of differentiated T cells in both CD4(+) T cells and CD8(+) T cells. Finally, we found that telomere length measured in blood leukocytes is correlated with lymphocyte telomere length. Thus, CMV infection induces a strong decrease in T cell telomere length, which can be explained by changes in the composition of the circulating lymphocyte pool.

Cytotoxic human CD4(+) T cells.

The induction of adaptive immune responses critically depends on helper signals provided by CD4(+) T cells. These signals not only license antigen presenting cells (APC) to activate naïve CD8(+) T cells leading to the formation of vast numbers of cytotoxic T lymphocytes but also support the differentiation of B cells into immunoglobulin-secreting plasma cells. Next to these helper functions, a subpopulation of CD4(+) T cells can also directly function as effector cells by executing cytotoxicity in a peptide-specific and MHC class II-restricted manner. Cytotoxic CD4(+) T cells may function in combating pathogens but additionally their presence has been associated with autoimmune disease and vascular damage. On the contrary, the induction of cytotoxic CD4(+) T cells may be a future target for vaccine strategies.

A fingerprint left by cytomegalovirus infection in the human T cell compartment.

Latent infection with human cytomegalovirus (HCMV) is accompanied by a strong increase in the number of resting, effector-type CD4+ and CD8+ T cells with constitutive cytolytic activity in the circulation. Longitudinal studies in kidney transplant recipients revealed that effector cells emerge early after the initial viral burst and acquire their stable phenotype in the months following primary infection. Although it is yet unsettled whether these cells are all specific for CMV encoded or induced antigens, it has become clear that T cell responses to CMV are among the broadest and strongest analyzed so far. We will here summarize the qualities of the effector-type cells found in HCMV carriers and discuss their possible role in CMV-associated pathologies.