Advances in critical care of the pediatric hematopoietic stem cell transplant patient

Extracorporeal membrane oxygenation in children receiving haematopoietic cell transplantation and immune effector cell therapy: an international and multidisciplinary consensus statement

Use of extracorporeal membrane oxygenation (ECMO) in children receiving haematopoietic cell transplantation (HCT) and immune effector cell therapy is controversial and evidence-based guidelines have not been established. Remarkable advancements in HCT and immune effector cell therapies have changed expectations around reversibility of organ dysfunction and survival for affected patients. Herein, members of the Extracorporeal Life Support Organization (ELSO), Pediatric Acute Lung Injury and Sepsis Investigators (PALISI) Network (HCT and cancer immunotherapy subgroup), the Pediatric Diseases Working Party of the European Society for Blood and Marrow Transplantation (EBMT), the supportive care committee of the Pediatric Transplantation and Cellular Therapy Consortium (PTCTC), and the Pediatric Intensive Care Oncology Kids in Europe Research (POKER) group of the European Society of Pediatric and Neonatal Intensive Care (ESPNIC) provide consensus recommendations on the use of ECMO in children receiving HCT and immune effector cell therapy. These are the first international, multidisciplinary consensus-based recommendations on the use of ECMO in this patient population. This Review provides a clinical decision support tool for paediatric haematologists, oncologists, and critical care physicians during the difficult decision-making process of ECMO candidacy and management. These recommendations can represent a base for future research studies focused on ECMO selection criteria and bedside management.

Extracorporeal Membrane Oxygenation Candidacy in Pediatric Patients Treated With Hematopoietic Stem Cell Transplant and Chimeric Antigen Receptor T-Cell Therapy: An International Survey

Introduction

Pediatric patients who undergo hematopoietic cell transplant (HCT) or chimeric antigen receptor T-cell (CAR-T) therapy are at high risk for complications leading to organ failure and the need for critical care resources. Extracorporeal membrane oxygenation (ECMO) is a supportive modality that is used for cardiac and respiratory failure refractory to conventional therapies. While the use of ECMO is increasing for patients who receive HCT, candidacy for these patients remains controversial. We therefore surveyed pediatric critical care and HCT providers across North America and Europe to evaluate current provider opinions and decision-making and institutional practices regarding ECMO use for patients treated with HCT or CAR-T.

Methods

An electronic twenty-eight question survey was distributed to pediatric critical care and HCT providers practicing in North America (United States and Canada) and Europe through the Pediatric Acute Lung Injury and Sepsis Investigators (PALISI) Network and individual emails. Responses to the survey were recorded in a REDCap^® database.

Results

Two-hundred and ten participants completed the survey. Of these, 159 (76%) identified themselves as pediatric critical care physicians and 47 (22%) as pediatric HCT physicians or oncologists. The majority (99.5%) of survey respondents stated that they would consider patients treated with HCT or CAR-T therapy as candidates for ECMO support. However, pediatric critical care physicians identified more absolute and relative contraindications for ECMO than non-pediatric critical care physicians. While only 0.5% of respondents reported that they consider HCT as an absolute contraindication for ECMO, 6% of respondents stated that ECMO is contraindicated in HCT patients within their institution and only 23% have an institutional protocol or policy to guide the evaluation for ECMO candidacy of these patients. Almost half (49.1%) of respondents would accept a survival to hospital discharge of 20-30% for pediatric HCT patients requiring ECMO as adequate.

Conclusions

ECMO use for pediatric patients treated with HCT and CAR-T therapy is generally acceptable amongst physicians. However, there are differences in the evaluation and decision-making regarding ECMO candidacy amongst providers across medical specialties and institutions. Therefore, multidisciplinary collaboration is an essential component in establishing practice guidelines and advancing ECMO outcomes for these patients.

Declining mortality rates in children admitted to ICU following HCT

We aimed to assess short- and long-term mortality, including factors associated with mortality, for children referred to a pediatric intensive care unit (ICU) at Rigshospitalet, Denmark, following haematopoietic cell transplantation (HCT). Data regarding admission to ICU and mortality following HCT for children below 16 years of age between 2000 and 2017 were retrospectively analyzed. We identified 55 ICU admissions in 39 patients following 46 HCTs. The overall in-ICU, in-hospital, 3-month, and 1-year mortality rates were 33.3%, 43.6%, 46.2%, and 51.3%, respectively. Patients admitted from 2000 to 2010 had a 3-month mortality of 63.2% and 1-year mortality of 68.4%, compared to 30% and 35% (P = .040 and P = .039) for patients admitted from 2011 to 2017. The main reason for ICU admission was respiratory failure (78.2%). Mechanical ventilation (MV) was associated with a higher long-term mortality (P = .044), and use of inotropes or vasopressors was associated with increased mortality at all times (all P > .006). Extracorporeal life support, renal replacement therapy, longer ICU stay, and longer time with MV were not associated with increased mortality. Over the past two decades, mortality was significantly reduced in pediatric HCT patients admitted to the ICU. The cause is probably multifactorial and warrants further studies. Our findings support admissions of critically ill pediatric HCT patients to intensive care with encouraging outcomes of even long-term admissions.

Interferon-complement loop in transplant-associated thrombotic microangiopathy

Transplant-associated thrombotic microangiopathy (TA-TMA) is an important cause of morbidity and mortality after hematopoietic stem cell transplantation (HSCT). The complement inhibitor eculizumab improves TA-TMA, but not all patients respond to therapy, prompting a search for additional targetable pathways of endothelial injury. TA-TMA is relatively common after HSCT and can serve as a model to study mechanisms of tissue injury in other thrombotic microangiopathies. In this work, we performed transcriptome analyses of peripheral blood mononuclear cells collected before HSCT, at onset of TA-TMA, and after resolution of TA-TMA in children with and without TA-TMA after HSCT. We observed significant upregulation of the classical, alternative, and lectin complement pathways during active TA-TMA. Essentially all upregulated genes and pathways returned to baseline expression levels at resolution of TA-TMA after eculizumab therapy, supporting the clinical practice of discontinuing complement blockade after resolution of TA-TMA. Further analysis of the global transcriptional regulatory network showed a notable interferon signature associated with TA-TMA with increased STAT1 and STAT2 signaling that resolved after complement blockade. In summary, we observed activation of multiple complement pathways in TA-TMA, in contrast to atypical hemolytic uremic syndrome (aHUS), where complement activation occurs largely via the alternative pathway. Our data also suggest a key relationship between increased interferon signaling, complement activation, and TA-TMA. We propose a model of an "interferon-complement loop" that can perpetuate endothelial injury and thrombotic microangiopathy. These findings open opportunities to study novel complement blockers and combined anti-complement and anti-interferon therapies in patients with TA-TMA and other microangiopathies like aHUS and lupus-associated TMAs.

Complement in Pathophysiology and Treatment of Transplant-Associated Thrombotic Microangiopathies

Transplant-associated thrombotic microangiopathy (TA-TMA) is a form of microangiopathy specifically occurring in the context of hematopoietic stem cell transplantation. Similarly, to other microangiopathies, TA-TMA is characterized by hemolytic anemia, thrombocytopenia, and organ failure due to endothelial injury. Although its clinical association with medications (eg, calcineurin inhibitors), immune reactions (eg, graft vs host disease) or infectious complications is well established, the pathophysiology remains largely unknown. Recent data have highlighted the role of complement in the pathophysiology of TA-TMA, which are frequently associated with a functional impairment (either inherited or acquired) of the endogenous regulation of the complement classic and alternative pathway. This manuscript will review the data supporting the involvement of complement in the pathophysiology of TA-TMA, as well as the clinical data supporting the use of anticomplement agents in this rare condition.

Team-based approach to identify cardiac toxicity in critically ill hematopoietic stem cell transplant recipients

INTRODUCTION

We observed pulmonary hypertension (PH), pericardial effusions, and left ventricular systolic dysfunction (LVSD) in multiple critically ill hematopoietic stem cell transplant (HSCT) recipients. We implemented routine structured echocardiography screening for HSCT recipients admitted to the pediatric intensive care unit (PICU) using a standardized multidisciplinary process.

METHODS

HSCT recipients admitted to the PICU with respiratory distress, hypoxia, shock, and complications related to transplant-associated thrombotic microangiopathy were screened on admission and every 1-2 weeks thereafter. Echocardiography findings requiring intervention and/or further screening included elevated right ventricular pressure, LVSD, and moderate to large pericardial effusions. All echocardiograms were compared to the patient's routine pretransplant echocardiogram.

RESULTS

Seventy HSCT recipients required echocardiography screening over a 3-year period. Echo abnormalities requiring intervention and/or further screening were found in 35 (50%) patients. Twenty-four (34%) patients were noted to have elevated right ventricular pressure; 14 (20%) were at risk for PH, while 10 (14%) had PH. All patients with PH were treated with pulmonary vasodilators. LVSD was noted in 22 (31%) patients; 15/22 (68%) received inotropic support. Moderate to large pericardial effusions were present in nine (13%) patients, with six needing pericardial drain placement.

DISCUSSION

Echocardiographic abnormalities are common in critically ill HSCT recipients. Utilization of echocardiogram screening may allow for early detection and timely intervention for cardiac complications in this high-risk cohort.

Sleep Disturbances in Acutely Ill Patients with Cancer

Intensive care units may place acutely ill patients with cancer at additional risk for sleep loss and associated negative effects. Research suggests that communication about sleep in patients with cancer is suboptimal and sleep problems are not regularly assessed or adequately treated throughout the cancer trajectory. However, many sleep problems and fatigue can be managed effectively. This article synthesizes the current literature regarding the prevalence, cause, and risk factors that contribute to sleep disturbance in the context of acute cancer care. It describes the consequences of poor sleep and discusses appropriate assessment and treatment options.

Pediatric Hematopoietic Stem Cell Transplant and Intensive Care: Have Things Changed?

OBJECTIVES

Mortality for pediatric patients who require intensive care posthematopoietic stem cell transplant still remains high. Previously at our institution, survival rates were 44% for patients who required mechanical ventilation posthematopoietic stem cell transplant. We conducted a review of patients to identify whether there has been any improvement in survival over the past 12 years and to identify any risk factors that contribute to mortality.

DESIGN

Retrospective chart review.

SETTING

PICU and hematopoietic stem cell transplant unit of a single tertiary children's hospital.

PATIENTS

Children less than 18 years old undergoing hematopoietic stem cell transplant who required admission to the ICU between January 2000 and December 2011.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

There were 350 separate admissions to the ICU for 206 patients posthematopoietic stem cell transplant. Median Age was 9.3 years (range, 1-17 yr). Median time from hematopoietic stem cell transplant to admission was 35 days (interquartile range, 13-152 d), and 59% of patients were male. Survival to ICU discharge for all admissions was 75%, which equated to 57% of all patients. Of the admissions that required invasive mechanical ventilation, 48% survived to ICU discharge, with a survival to ICU discharge of 36% if there was more than one admission requiring mechanical ventilation. Survival to ICU discharge was 33% if renal replacement therapy was required. Mechanical ventilation, inotrope/vasopressor use, and number of organ dysfunction within an admission were predictors of mortality. Having an underlying malignant condition or an autologous hematopoietic stem cell transplant was associated with a more favorable outcome.

CONCLUSIONS

This is the largest single-center series for pediatric patients who require intensive care posthematopoietic stem cell transplant and demonstrates that this group of patients still faces high mortality. There has been an improvement in survival for those patients who require renal replacement therapy and also for patients who require mechanical ventilation more than once; however, the need for mechanical ventilation still remains a significant predictor of mortality.

The genetic fingerprint of susceptibility for transplant-associated thrombotic microangiopathy

Transplant-associated thrombotic microangiopathy (TA-TMA) occurs frequently after hematopoietic stem cell transplantation (HSCT) and can lead to significant morbidity and mortality. There are no data addressing individual susceptibility to TA-TMA. We performed a hypothesis-driven analysis of 17 candidate genes known to play a role in complement activation as part of a prospective study of TMA in HSCT recipients. We examined the functional significance of gene variants by using gene expression profiling. Among 77 patients undergoing genetic testing, 34 had TMA. Sixty-five percent of patients with TMA had genetic variants in at least one gene compared with 9% of patients without TMA (P < .0001). Gene variants were increased in patients of all races with TMA, but nonwhites had more variants than whites (2.5 [range, 0-7] vs 0 [range, 0-2]; P < .0001). Variants in ≥3 genes were identified only in nonwhites with TMA and were associated with high mortality (71%). RNA sequencing analysis of pretransplantation samples showed upregulation of multiple complement pathways in patients with TMA who had gene variants, including variants predicted as possibly benign by computer algorithm, compared with those without TMA and without gene variants. Our data reveal important differences in genetic susceptibility to HSCT-associated TMA based on recipient genotype. These data will allow prospective risk assessment and intervention to prevent TMA in highly susceptible transplant recipients. Our findings may explain, at least in part, racial disparities previously reported in transplant recipients and may guide treatment strategies to improve outcomes.

Intensive Care Unit Admissions Among Children After Hematopoietic Stem Cell Transplantation: Incidence, Outcome, and Prognostic Factors

We retrospectively analyzed posttransplantation events in 299 children who underwent hematopoietic stem cell transplantation between 2005 and 2011 in order to ascertain the incidence of life-threatening complications requiring pediatric intensive care unit (PICU) admission, the contributing risk factors, and the patient's long-term survival. Sixty-eight patients (23%) were admitted to the PICU. Risks factors associated with higher cumulative incidence of PICU admission on univariate analysis were nonmalignant disease, status at transplantation, type of transplant, source of stem cell, engraftment syndrome (ES), veno-occlusive disease, acute graft versus host disease (GvHD), chronic GvHD, thrombotic microangiopathy, bronchiolitis obliterans, hemorrhagic cystitis, and posterior reversible encephalopathy syndrome (PRES). On multivariate analysis, only ES, acute GvHD, transplant-associated thrombotic microangiopathy (TA-TMA), and PRES were statistically significant. The variables that had a negative impact on survival, on univariate analysis, were allogeneic transplant, age, male sex, a high O-PRISM score, a high O-PRISM3 score, engraftment failure, acute GvHD, TA-TMA, hemorrhagic cystitis, and PRES. On multivariate analysis, only age, allogeneic transplant, engraftment failure, acute GvHD, TA-TMA, and hemorrhagic cystitis had a negative impact on survival. In conclusion, our report provides new findings regarding life-threatening complications after hematopoietic transplantation for PICU admission and survival after that in a pediatric population.

Long-Lasting Impact of Neonatal Exposure to Total Body Gamma Radiation on Secondary Lymphoid Organ Structure and Function

The acute period after total body irradiation (TBI) is associated with an increased risk of infection, principally resulting from the loss of hematopoietic stem cells, as well as disruption of mucosal epithelial barriers. Although there is a return to baseline infection control coinciding with the apparent progressive recovery of hematopoietic cell populations, late susceptibility to infection in radiation-sensitive organs such as lung and kidney is known to occur. Indeed, pulmonary infections are particularly prevalent in hematopoietic cell transplant (HCT) survivors, in both adult and pediatric patient populations. Preclinical studies investigating late outcomes from localized thoracic irradiation have indicated that the mechanisms underlying pulmonary delayed effects are multifactorial, including exacerbated and persistent production of pro-inflammatory molecules and abnormal cross-talk among parenchymal and infiltrating immune and inflammatory cell populations. However, in the context of low-dose TBI, it is not clear whether the observed exacerbated response to infection remains contingent on these same mechanisms. It is possible instead, that after systemic radiation-induced injury, the susceptibility to infection may be independently related to defects in alternative organs that are revealed only through the challenge itself; indeed, we have hypothesized that this defect may be due to radiation-induced chronic effects in the structure and function of secondary lymphoid organs (SLO). In this study, we investigated the molecular and cellular alterations in SLO (i.e., spleen, mediastinal, inguinal and mesenteric lymph nodes) after TBI, and the time points when there appears to be immune competence. Furthermore, due to the high incidence of pulmonary infections in the late post-transplantation period of bone marrow transplant survivors, particularly in children, we focused on outcomes in mice irradiated as neonates, which served as a model for a pediatric population, and used the induction of adaptive immunity against influenza virus as a functional end point. We demonstrated that, in adult animals irradiated as neonates, high endothelial venule (HEV) expansion, generation of follicular helper T cells (TFH) and formation of splenic germinal centers (GC) were rapidly and, more importantly, persistently impaired in SLO, suggesting that the early-life exposure to sublethal radiation had long-lasting effects on the induction of humoral immunity. Although the neonatal TBI did not affect the overall outcome from influenza infection in the adults at the earlier time points assessed, we believe that they nonetheless contribute significantly to the increased mortality observed at subsequent late time points. Furthermore, we speculate that the detrimental and persistent impact on the induction of CD4 T- and B-cell responses in the mediastinal lymph nodes will decrease the animals' ability to respond to other aerial pathogens. Since many of these pathogens are normally cleared by antibodies, our findings provide an explanation for the susceptibility of survivors of childhood HCT to life-threatening respiratory tract infections. These findings have implications regarding the need for increased monitoring in pediatric hematopoietic cell transplant patients, since they indicate that there are ongoing and cumulative defects in SLO, which, importantly, develop during the immediate and early postirradiation period when patients may appear immunologically competent. The identification of changes in immune-related signals may offer bioindicators of progressive dysfunction, and of potential mechanisms that could be targeted so as to reduce the risk of infection from extracellular pathogens. Furthermore, these results support the potential susceptibility of the pediatric population to infection after sublethal irradiation in the context of a nuclear or radiological event.

Pulmonary hypertension after hematopoietic stem cell transplantation

Pulmonary hypertension (PH) is a potentially fatal complication of hematopoietic stem cell transplantation (HSCT). Given its nonspecific clinical presentation, it is likely that this clinical entity is underdiagnosed after HSCT. Data describing the incidence, risk factors, and etiology of PH in HSCT recipients are minimal. Physicians caring for HSCT recipients should be aware of this severe post-transplant complication because timely diagnosis and treatment may allow improved clinical outcomes. We summarize the pathophysiology, clinical presentation, diagnosis, and management of PH in HSCT recipients.