The care of critically ill children after hematopoietic SCT: a North American survey

The Physiological Basis of High-Frequency Oscillatory Ventilation and Current Evidence in Adults and Children: A Narrative Review

High-frequency oscillatory ventilation (HFOV) is a type of invasive mechanical ventilation that employs supra-physiologic respiratory rates and low tidal volumes (V_T) that approximate the anatomic deadspace. During HFOV, mean airway pressure is set and gas is then displaced towards and away from the patient through a piston. Carbon dioxide (CO₂) is cleared based on the power (amplitude) setting and frequency, with lower frequencies resulting in higher V_T and CO₂ clearance. Airway pressure amplitude is significantly attenuated throughout the respiratory system and mechanical strain and stress on the alveoli are theoretically minimized. HFOV has been purported as a form of lung protective ventilation that minimizes volutrauma, atelectrauma, and biotrauma. Following two large randomized controlled trials showing no benefit and harm, respectively, HFOV has largely been abandoned in adults with ARDS. A multi-center clinical trial in children is ongoing. This article aims to review the physiologic rationale for the use of HFOV in patients with acute respiratory failure, summarize relevant bench and animal models, and discuss the potential use of HFOV as a primary and rescue mode in adults and children with severe respiratory failure.

Organizational characteristics of European pediatric onco-critical care: An international cross-sectional survey

BACKGROUND

Intensified treatment protocols have improved survival of pediatric oncology patients. However, these treatment protocols are associated with increased treatment-related morbidity requiring admission to pediatric intensive care unit (PICU). We aimed to describe the organizational characteristics and processes of care for this patient group across PICUs in Europe.

METHODS

A web-based survey was sent to PICU directors or representative physicians between February and June 2021.

RESULTS

Responses were obtained from 77 PICUs of 12 European countries. Organizational characteristics were similar across the different countries of Europe. The median number of PICU beds was 12 (IQR 8-16). The majority of the PICUs was staffed by pediatric intensivists and had a 24/7 intensivist coverage. Most PICUs had a nurse-to-patient ratio of 1:1 or 1:2. The median numbers of yearly planned and unplanned PICU admissions of pediatric cancer patients were 20 (IQR 10-45) and 10 (IQR 10-30, respectively. Oncology specific practices within PICU were less common in participating centres. This included implementation of oncology protocols in PICU (30%), daily rounds of PICU physicians on the wards (13%), joint mortality and morbidity meetings or complex patients' discussions (30% and 40%, respectively) and participation of parents during clinical rounds (40%).

CONCLUSION

Our survey provides an overview on the delivery of critical care for oncology patients in PICU across European countries. Multidisciplinary care for these vulnerable and challenging patients remains complex and challenging. Future studies need to determine the effects of differences in PICU organization and processes of care on patients' outcome.

Outcomes of Children Who Present to the Emergency Department After Hematopoietic Cell Transplantation

OBJECTIVES

Our primary objective was to describe emergency department (ED) presentation, treatment, and outcomes for children after hematopoietic cell transplantation (HCT). Our secondary objective was to identify factors associated with serious infection in this population.

METHODS

This is a retrospective review of HCT patients who presented to our university children's hospital ED from January 1, 2011, to June 30, 2013. Emergency department presentation, treatment, and outcomes were described. Descriptive statistics were used to compare children with definite serious infection with those without serious infection. Multiple binary logistic regression was performed for risk factors associated with definite serious infection.

RESULTS

Fifty-four HCT patients (132 encounters) presented to our ED. Most were transplanted for a malignant (46%) or metabolic (36%) diagnosis and were recipients of bone marrow (51%) or umbilical cord blood (45%). Fever was the most common complaint (25%). Emergency department laboratory (64%) or imaging (58%) studies were frequently obtained. Admission was common (n = 70/132, 53%), with 79% (n = 55) of admissions to intensive care or bone marrow transplant units. Thirty-five encounters had definite serious infection, 5 had probable serious infection, and 92 had no serious infection. Fever (P < 0.001) and high-risk white blood cell (WBC) count of less than 5 or greater than 15 k/μL (P < 0.001) were associated with definite serious infection. Fever (odds ratio = 8.84, 95% confidence interval = 2.92-26.73) and high-risk WBC (odds ratio = 6.67, 95% confidence interval = 2.24-19.89) remained significantly associated with definite serious infection in our regression model.

CONCLUSIONS

Children presenting to the ED after HCT require extensive support and resources, with more than half requiring admission. Fever and high-risk WBC are associated with serious infection.

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.

Risk Factors for Mortality and Pre-ICU Fluid Balance Among Critically Ill Hematopoietic Stem Cell Transplant Patients

OBJECTIVE

To examine if fluid balance surrounding pediatric intensive care unit (PICU) admission in hematopoietic stem cell transplant (HSCT) patients was associated with mortality, ventilator-free days, and intensive care unit (ICU)-free days. To explore other population-specific factors associated with poor outcome.

MATERIALS AND METHODS

Retrospective review of HSCT patients admitted to 2 quaternary PICUs, Children's Hospital Los Angeles and University of California San Francisco Benioff Children's Hospital from January 2009 to December 2014.

RESULTS

Of 144 patients, 92 were identified with complete fluid balance data available. No difference in fluid balance between survivors and nonsurvivors in the 24 hours preceding PICU admission (P = .81) or when the first 24 hours of PICU stay were taken into account (P = .48) was identified. There was no difference in ventilator-free or ICU-free days. Comparing Pediatric Index of Mortality (PIM)-2, Pediatric Risk of Mortality (PRISM)-3, and a multivariable model using independent risk factors identified through multivariable analysis, the receiver operating characteristic plot for the multivariable model (area under the curve = 0.844 [95% confidence interval: 0.77-0.92]) was superior to both PIM-2 and PRISM-3 in discriminating mortality.

CONCLUSIONS

Fluid balance immediately preceding and early in the course of admission was not associated with mortality in PICU HSCT patients. A subset of variables was identified which better discriminated mortality in this cohort than accepted PICU severity of illness scores.

Invasive Mechanical Ventilation and Mortality in Pediatric Hematopoietic Stem Cell Transplantation: A Multicenter Study

OBJECTIVE

To establish the current respiratory practice patterns in pediatric hematopoietic stem cell transplant patients and investigate their associations with mortality across multiple centers.

DESIGN

Retrospective cohort between 2009 and 2014.

SETTING

Twelve children's hospitals in the United States.

PATIENTS

Two hundred twenty-two pediatric allogeneic hematopoietic stem cell transplant recipients with acute respiratory failure using invasive mechanical ventilation.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

PICU mortality of our cohort was 60.4%. Mortality at 180 days post PICU discharge was 74%. Length of PICU stay prior to initiation of invasive mechanical ventilation was significantly lower in survivors, and the odds of mortality increased for longer length of PICU stay prior to intubation. A total of 91 patients (41%) received noninvasive ventilation at some point during their PICU stay prior to intubation. Noninvasive ventilation use preintubation was associated with increased mortality (odds ratio, 2.1; 95% CI, 1.2-3.6; p = 0.010). Patients ventilated longer than 15 days had higher odds of death (odds ratio, 2.4; 95% CI, 1.3-4.2; p = 0.004). Almost 40% of patients (n = 85) were placed on high-frequency oscillatory ventilation with a mortality of 76.5% (odds ratio, 3.3; 95% CI, 1.7-6.5; p = 0.0004). Of the 20 patients who survived high-frequency oscillatory ventilation, 18 were placed on high-frequency oscillatory ventilation no later than the third day of invasive mechanical ventilation. In this subset of 85 patients, transition to high-frequency oscillatory ventilation within 2 days of the start of invasive mechanical ventilation resulted in a 76% decrease in the odds of death compared with those who transitioned to high-frequency oscillatory ventilation later in the invasive mechanical ventilation course.

CONCLUSIONS

This study suggests that perhaps earlier more aggressive critical care interventions in the pediatric hematopoietic stem cell transplant patient with respiratory failure requiring invasive mechanical ventilation may offer an opportunity to improve outcomes.

Accuracy of Bedside Paediatric Early Warning System (BedsidePEWS) in a Pediatric Stem Cell Transplant Unit

Hospital mortality in children who undergo stem cell transplant (SCT) is high. Early warning scores aim at identifying deteriorating patients and at preventing adverse outcomes. The bedside pediatric early warning system (BedsidePEWS) is a pediatric early warning score based on 7 clinical indicators, ranging from 0 (all indicators within normal ranges for age) to 26. The aim of this case-control study was to assess the performance of BedsidePEWS in identifying clinical deterioration events among children admitted to an SCT unit. Cases were defined as clinical deterioration events; controls were all the other patients hospitalized on the same ward at the time of case occurrence. BedsidePEWS was retrospectively measured at 4-hour intervals in cases and controls 24 hours before an event (T4-T24). We studied 19 cases and 80 controls. The score significantly increased in cases from a median of 4 at T24 to a median of 14 at T4. The proportion of correctly classified cases and controls was >90% since T8. The area under the curve receiver operating characteristic was 0.9. BedsidePEWS is an accurate screening tool to predict clinical deterioration in SCT patients.

A Critical Care and Transplantation-Based Approach to Acute Respiratory Failure after Hematopoietic Stem Cell Transplantation in Children

Acute respiratory failure contributes significantly to nonrelapse mortality after allogeneic hematopoietic stem cell transplantation. Although there is a trend of improved survival over time, mortality remains unacceptably high. An understanding of the pathophysiology of early respiratory failure, opportunities for targeted therapy, assessment of the patient at risk, optimal use of noninvasive positive pressure ventilation, strategies to improve alveolar recruitment, appropriate fluid management, care of the patient with chronic lung disease, and importantly, a team approach between critical care and transplantation services may improve outcomes.

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Outcomes from acute respiratory failure after hematopoietic stem cell transplantation remain unacceptably high.

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The review focuses on strategies to improve these outcomes.

New Insights Into Multicenter PICU Mortality Among Pediatric Hematopoietic Stem Cell Transplant Patients

OBJECTIVES

Over 2,500 children undergo hematopoietic stem cell transplantation in the United States each year, and up to 35% require PICU support for life-threatening complications. PICU mortality has dropped from 85% to 44%, but interpretation is confounded by significant cohort heterogeneity. Reports conflict regarding outcomes for patients with different underlying hematopoietic stem cell transplantation indications, and the burden of infectious complications for these patients has not been evaluated. We aim to describe infections, critical care interventions, and mortality for pediatric hematopoietic stem cell transplantation patients requiring PICU admission.

DESIGN

A retrospective multicenter cohort analysis.

SETTING

One hundred twelve centers in the Virtual PICU Systems database, January 1, 2009, to June 30, 2012.

PATIENTS

A total of 1,782 admissions for patients who are 21 years old or younger with prior hematopoietic stem cell transplantation.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Pediatric Index of Mortality-2, Pediatric Risk of Mortality-3, transplant indication, infections, interventions, and mortality were recorded from admission through PICU death or discharge. Pediatric hematopoietic stem cell transplantation patients comprised 0.7% of all PICU admissions (1,782/246,346), which resulted in 16.2% mortality compared with 2.4% mortality for non-hematopoietic stem cell transplantation admissions (odds ratio, 7.8; 95% CI, 6.8-8.8; p < 0.001). Mortality for admissions with underlying hematologic malignancy (22.7%) was similar to that of admissions with primary immunodeficiency (19.4%; p = 0.41) but significantly greater than admissions with underlying nonmalignant non-primary immunodeficiency hematologic disease (15.4%; p = 0.020), metabolic disorder (8.1%; p < 0.001), or solid malignancy (5.7%; p < 0.001). Infection was documented in 45.7% of admissions with 22.2% mortality; viral and fungal mortality were 28.5% and 33.7%, respectively. Invasive positive pressure ventilation and renal replacement therapy were used in only 34.6% and 11.9% of admissions, with mortality of 42.5% and 51.9%, respectively.

CONCLUSIONS

PICU mortality for pediatric hematopoietic stem cell transplantation patients may be as low as 16.2% but higher for those receiving intubation (42.5%) or replacement therapy (51.9%). Hematologic malignancy and primary immunodeficiency had greater risk for mortality than other transplant indications. Greater understanding of other risk factors affecting mortality and the need for critical care support is needed.

Outcome of invasive mechanical ventilation after pediatric allogeneic hematopoietic SCT: results from a prospective, multicenter registry

Exact data on prognosis of children receiving invasive mechanical ventilation (IMV) after allogeneic hematopoietic SCT (HSCT) is lacking. We therefore started a prospective registry in four European university HSCT centers (Leiden, Paris, Prague and Utrecht) and their pediatric intensive care units (PICUs). The registry started in January 2009. In January 2013, the four centers together had treated a total of 83 admissions with IMV. The case fatality rate in these patients was 52%. Mortality 6 months after PICU discharge was 45%. There were significant differences between centers in the proportion of children who received IMV after HSCT (6-23%, P<0.01), in severity of disease on admission to PICU (predicted mortality 14-37%, P<0.01), in applying noninvasive ventilation before IMV (3-75% of admissions, P<0.01) and in the use of renal replacement therapy (RRT) (8-58% of admissions, P<0.01). Severe impairment in oxygenation, use of RRT and CMV viremia were independent predictors of mortality. Our study shows that mortality in children receiving IMV after HSCT remains high, but has clearly improved compared with older studies. Patient selection and treatment in PICU differed significantly between centers, which underscores the need to standardize and optimize the PICU admission criteria, ventilatory strategies and therapies applied in PICU.

Stem cell transplantation and lung dysfunction

PURPOSE OF REVIEW

To identify factors that impact the incidence and severity of lung dysfunction after haematopoietic stem cell transplantation (HSCT) for preventive and therapeutic purposes.

RECENT FINDINGS

Respiratory failure from lung dysfunction after HSCT is a serious and often fatal transplant-related complication, but recent data reveal decreasing incidence and improving outcome over time. Idiopathic pneumonia syndrome (IPS) and bronchiolitis obliterans are now recognized as part of a spectrum of post-HSCT lung diseases involving both aspects of innate and adaptive immune responses, but may differ in the main lung structure affected: alveolar versus airway epithelium. There exists a strong association between acute graft-versus-host disease (GVHD) and IPS, and bronchiolitis obliterans is pathognomonic of chronic GVHD. Experimental models of IPS and bronchiolitis obliterans have proven useful to test strategies designed to limit lung injury including the effects of allogeneity, chemoradiotherapy and stem cell therapy. Recent advances in critical care practices, early diagnosis and utilizing ARDS Network ventilatory and conservative fluid management recommendations have also contributed to better outcome from lung dysfunction after HSCT.

SUMMARY

Understanding the factors that contribute to post-HSCT lung injury should lead to safer transplant practices that will allow the broader use of HSCT for sicker children with comorbidities.

Clinical outcomes of children receiving intensive cardiopulmonary support during hematopoietic stem cell transplant

OBJECTIVE

We investigated the short-term and 1-year clinical outcomes of 129 children who received intensive cardiopulmonary support during hematopoietic stem cell transplant. Intensive cardiopulmonary support was defined as receiving at least one of the following interventions: continuous positive pressure ventilation, dopamine infusion greater than or equal to 10 mcg/kg/minute, or the use of any other vasoactive infusion. Duration of intensive cardiopulmonary support, survival to hospital discharge, and predictors of these outcome variables were compared with 387 hematopoietic stem cell transplant patients who did not receive intensive support during the same period. We also report the 1-year survival; presence of chronic graft-versus-host disease; and renal, cardiac, and pulmonary function for all patients.

DESIGN

A multicenter retrospective cohort study.

SETTING

The ICU and hematopoietic stem cell transplant unit of nine pediatric tertiary care centers.

PATIENTS

Children undergoing hematopoietic stem cell transplant who required intensive cardiopulmonary support.

INTERVENTIONS

None.

RESULTS

Predictors of the need for intensive support included unrelated donor allogeneic transplant, glomerular filtration rate less than 85 mL/minute/1.73 m, and nonmalignant disease as the indication for transplant. The survival to discontinuation of intensive support for all patients was 62% and 58% for patients who received invasive mechanical ventilatory support. The duration of mechanical ventilation was not predictive of survival. Predictors of intensive support mortality included macroscopic bleeding, engraftment, and pediatric logistic organ dysfunction score greater than one in two domains. Survival to hospital discharge was 50% for the intensive support group and 99% for the nonintensive support group. Overall 1-year survival was 40% in the intensive support population and 65% in the nonintensive support group. There were no significant differences in the survival, rates of chronic graft-versus-host disease, creatinine, forced expiratory volume in 1-minute, cardiac shortening fraction, or performance status in intensive and nonintensive support patients who survived to hospital discharge.

CONCLUSION

Intensive cardiopulmonary support plays an important and potentially life-saving role in the care of pediatric stem cell transplant patients. Survivors of intensive support do not have compromised 1-year survival or organ function compared with children who did not receive intensive support.