Association of Severe Hyperoxemia Events and Mortality Among Patients Admitted to a Pediatric Intensive Care Unit

Closed-loop automated oxygen control in late preterm and term, ventilated infants: A randomised controlled trial

AIM

To compare the time spent above the target oxygen saturation range (SpO2 > 96%) and the duration of supplemental oxygen between ventilated infants receiving closed-loop automated oxygen control (CLAC) or manual oxygen control in late preterm and term ventilated infants.

METHODS

Infants were randomised to receive CLAC or manual oxygen control from recruitment and within 24 h of mechanical ventilation until successful extubation.

RESULTS

Forty infants with a median (IQR) gestational age of 37.4 (35.9-38.5) weeks were studied at a corrected postmenstrual age of 37.6 (36.0-38.7) weeks. In infants randomised to CLAC (n = 18) the time spent above the target oxygen saturation range was reduced by 20% (p < 0.001), and the time spent in the target range (92%-96%) was increased by 32% (p < 0.001) and the time spent in hyperoxia was reduced (p = 0.003). CLAC reduced the time spent in hypoxemia (SpO2 < 85%) (p = 0.017) and there were fewer manual adjustments to the inspired oxygen concentration (FiO2) (p < 0.001). There was no significant difference in the duration of supplemental oxygen (p = 0.271).

CONCLUSION

CLAC in ventilated infants born at or near term was associated with reduced time spent in hyperoxemia, more time spent in the target oxygen range, and fewer manual adjustments to the FiO2.

Association of extreme hyperoxemic events and mortality in pediatric critical care: an observational cohort study

Objective

Our aim was to confirm whether extreme hyperoxemic events had been associated with excess mortality in our diverse critical care population.

Methods

Retrospective analysis of 9 years of data collected in the pediatric and cardiothoracic ICUs in Children's Hospital Los Angeles was performed. The analysis was limited to those mechanically ventilated for at least 24 h, with at least 1 arterial blood gas measurement. An extreme hyperoxemic event was defined as a PaO2 of ≥300 torr. Multivariable logistic regression was used to assess the association of extreme hyperoxemia events and mortality, adjusting for confounding variables. Selected a-priori, these were Pediatric Risk of Mortality III predicted mortality, general or cardiothoracic ICU, number of blood gas measurements, as well as an abnormal blood gas measurements (pH < 7.25, pH > 7.45, and PaO2 < 50 torr).

Results

There were 4,003 admissions included with a predicted mortality of 7.1% and an actual mortality of 9.7%. Their care was associated with 75,129 blood gas measurements, in which abnormal measurements were common. With adjustments for these covariates, any hyperoxemic event was associated with excess mortality (p < 0.001). Excess mortality increased with multiple hyperoxemic events (p < 0.046). Additionally, treatment resulting in SpO2 > 98% markedly increased the risk of a hyperoxemic event.

Conclusion

Retrospective analysis of critical care admissions showed that extreme hyperoxemic events were associated with higher mortality. Supplemental oxygen levels resulting in SpO2 > 98% should be avoided.

Pa o2 and Mortality in Neonatal Extracorporeal Membrane Oxygenation: Retrospective Analysis of the Extracorporeal Life Support Organization Registry, 2015-2020

OBJECTIVES

Extracorporeal life support can lead to rapid reversal of hypoxemia but the benefits and harms of different oxygenation targets in severely ill patients are unclear. Our primary objective was to investigate the association between the Pa o2 after extracorporeal membrane oxygenation (ECMO) initiation and mortality in neonates treated for respiratory failure.

DESIGN

Retrospective analysis of the Extracorporeal Life Support Organization (ELSO) Registry data, 2015-2020.

PATIENTS

Newborns supported by ECMO for respiratory indication were included.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Pa o2 24 hours after ECMO initiation (H24 Pa o2 ) was reported. The primary outcome was 28-day mortality. We identified 3533 newborns (median age 1 d [interquartile range (IQR), 1-3]; median weight 3.2 kg [IQR, 2.8-3.6]) from 198 ELSO centers, who were placed on ECMO. By 28 days of life, 731 (20.7%) had died. The median H24 Pa o2 was 85 mm Hg (IQR, 60-142). We found that both hypoxia (Pa o2 < 60 mm Hg) and moderate hyperoxia (Pa o2 201-300 mm Hg) were associated with greater adjusted odds ratio (aOR [95% CI]) of 28-day mortality, respectively: aOR 1.44 (95% CI, 1.08-1.93), p = 0.016, and aOR 1.49 (95% CI, 1.01-2.19), p value equals to 0.045.

CONCLUSIONS

Early hypoxia or moderate hyperoxia after ECMO initiation are each associated with greater odds of 28-day mortality among neonates requiring ECMO for respiratory failure.

Hyperoxemia among Pediatric Intensive Care Unit Patients Receiving Oxygen Therapy

Supratherapeutic oxygen levels consistently cause oxygen toxicity in the lungs and other organs. The prevalence and severity of hyperoxemia among pediatric intensive care unit (PICU) patients remain unknown. This was the first study to examine the prevalence and duration of hyperoxemia in PICU patients receiving oxygen therapy. This is a retrospective chart review. This was performed in a setting of 36-bed PICU in a quaternary-care children's hospital. All the patients were children aged <18 years, admitted to the PICU for ≥24 hours, receiving oxygen therapy for ≥12 hours who had at least one arterial blood gas during this time. There was no intervention. Of 5,251 patients admitted to the PICU, 614 were included in the study. On average, these patients received oxygen therapy for 91% of their time in the PICU and remained hyperoxemic, as measured by pulse oximetry, for 65% of their time on oxygen therapy. Patients on oxygen therapy remained hyperoxemic for a median of 38 hours per patient and only 1.1% of patients did not experience any hyperoxemia. Most of the time (87.5%) patients received oxygen therapy through a fraction of inspired oxygen (FiO 2 )-adjustable device. Mean FiO 2 on noninvasive support was 0.56 and on invasive support was 0.37. Mean partial pressure of oxygen (PaO 2 ) on oxygen therapy was 108.7 torr and 3,037 (42.1%) of PaO 2 measurements were >100 torr. Despite relatively low FiO 2 , PICU patients receiving oxygen therapy are commonly exposed to prolonged hyperoxemia, which may contribute to ongoing organ injury.

Early Hyperoxemia and 2-year Outcomes in Infants with Hypoxic-ischemic Encephalopathy: A Secondary Analysis of the Infant Cooling Evaluation Trial

OBJECTIVE

To determine the causal relationship between exposure to early hyperoxemia and death or major disability in infants with hypoxic-ischemic encephalopathy (HIE).

STUDY DESIGN

We analyzed data from the Infant Cooling Evaluation (ICE) trial that enrolled newborns ≥35 weeks' gestation with moderate-severe HIE, randomly allocated to hypothermia or normothermia. The primary outcome was death or major sensorineural disability at 2 years. We included infants with arterial pO2 measured within 2 hours of birth. Using a directed acyclic graph, we established that markers of severity of perinatal hypoxia-ischemia and pCO2 were a minimally sufficient set of variables for adjustment in a regression model to estimate the causal relationship between arterial pO2 and death/disability.

RESULTS

Among 221 infants, 116 (56%) had arterial pO2 and primary outcome data. The unadjusted analysis revealed a U-shaped relationship between arterial pO2 and death or major disability. Among hyperoxemic infants (pO2 100-500 mmHg) the proportion with death or major disability was 40/58 (0.69), while the proportion in normoxemic infants (pO2 40-99 mmHg) was 20/48 (0.42). In the adjusted model, hyperoxemia increased the risk of death or major disability (adjusted risk ratio 1.61, 95% CI 1.07-2.00, P = .03) in relation to normoxemia.

CONCLUSION

Early hyperoxemia increased the risk of death or major disability among infants who had an early arterial pO2 in the ICE trial. Limitations include the possibility of residual confounding and other causal biases. Further work is warranted to confirm this relationship in the era of routine therapeutic hypothermia.

Perspectives of Health Care Personnel on the Benefits of Bronchiolitis Interventions

OBJECTIVES

Many interventions in bronchiolitis are low-value or poorly studied. Inpatient bronchiolitis management is multidisciplinary, with varying degrees of registered nurse (RN) and respiratory therapist (RT) autonomy. Understanding the perceived benefit of interventions for frontline health care personnel may facilitate deimplementation efforts. Our objective was to examine perceptions surrounding the benefit of common inpatient bronchiolitis interventions.

METHODS

We conducted a cross-sectional survey of inpatient pediatric RNs, RTs, and physicians/licensed practitioners (P/LPs) (eg, advanced-practice practitioners) from May to December of 2021 at 9 university-affiliated and 2 community hospitals. A clinical vignette preceded a series of inpatient bronchiolitis management questions.

RESULTS

A total of 331 surveys were analyzed with a completion rate of 71.9%: 76.5% for RNs, 57.4% for RTs, and 71.2% for P/LPs. Approximately 54% of RNs and 45% of RTs compared with 2% of P/LPs believe albuterol would be "extremely or somewhat likely" to improve work of breathing (P < .001). Similarly, 52% of RNs, 32% of RTs, and 23% of P/LPs thought initiating or escalating oxygen in the absence of hypoxemia was likely to improve work of breathing (P < .001). Similar differences in perceived benefit were observed for steroids, nebulized hypertonic saline, and deep suctioning, but not superficial nasal suctioning. Hospital type (community versus university-affiliated) did not impact the magnitude of these differences.

CONCLUSIONS

Variation exists in the perceived benefit of several low-value or poorly studied bronchiolitis interventions among health care personnel, with RNs/RTs generally perceiving higher benefit. Deimplementation, educational, and quality improvement efforts should be designed with an interprofessional framework.

Neurologic Complications of Critical Medical Illness

OBJECTIVE

This article reviews the neurologic complications encountered in patients admitted to non-neurologic intensive care units, outlines various scenarios in which a neurologic consultation can add to the diagnosis or management of a critically ill patient, and provides advice on the best diagnostic approach in the evaluation of these patients.

LATEST DEVELOPMENTS

Increasing recognition of neurologic complications and their adverse impact on long-term outcomes has led to increased neurology involvement in non-neurologic intensive care units. The COVID-19 pandemic has highlighted the importance of having a structured clinical approach to neurologic complications of critical illness as well as the critical care management of patients with chronic neurologic disabilities.

ESSENTIAL POINTS

Critical illness is often accompanied by neurologic complications. Neurologists need to be aware of the unique needs of critically ill patients, especially the nuances of the neurologic examination, challenges in diagnostic testing, and neuropharmacologic aspects of commonly used medications.

Admission Pao2 and Mortality Among PICU Patients and Select Diagnostic Subgroups

OBJECTIVES

Evaluate the relationship between admission Pao2 and mortality in a large multicenter dataset and among diagnostic subgroups.

DESIGN

Retrospective cohort study.

SETTING

North American PICUs participating in Virtual Pediatric Systems, LLC (VPS), 2015-2019.

PATIENTS

Noncardiac patients 18 years or younger admitted to a VPS PICU with admission Pao2.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Thirteen thousand seventy-one patient encounters were included with an overall mortality of 13.52%. Age categories were equally distributed among survivors and nonsurvivors with the exception of small differences among neonates and adolescents. Importantly, there was a tightly fitting quadratic relationship between admission Pao2 and mortality, with the highest mortality rates seen among hypoxemic and hyperoxemic patients (likelihood-ratio test p < 0.001). This relationship persisted after adjustment for illness severity using modified Pediatric Index of Mortality 3 scores. A similar U-shaped relationship was demonstrated among patients with diagnoses of trauma, head trauma, sepsis, renal failure, hemorrhagic shock, and drowning. However, among the 1,500 patients admitted following cardiac arrest, there was no clear relationship between admission Pao2 and mortality.

CONCLUSIONS

In a large multicenter pediatric cohort, admission Pao2 demonstrates a tightly fitting quadratic relationship with mortality. The persistence of this relationship among some but not all diagnostic subgroups suggests the pathophysiology of certain disease states may modify the hyperoxemia association.

Temporal Patterns in Brain Tissue and Systemic Oxygenation Associated with Mortality After Severe Traumatic Brain Injury in Children

BACKGROUND

Brain tissue hypoxia is an independent risk factor for unfavorable outcomes in traumatic brain injury (TBI); however, systemic hyperoxemia encountered in the prevention and/or response to brain tissue hypoxia may also impact risk of mortality. We aimed to identify temporal patterns of partial pressure of oxygen in brain tissue (PbtO2), partial pressure of arterial oxygen (PaO2), and PbtO2/PaO2 ratio associated with mortality in children with severe TBI.

METHODS

Data were extracted from the electronic medical record of a quaternary care children's hospital with a level I trauma center for patients ≤ 18 years old with severe TBI and the presence of PbtO2 and/or intracranial pressure monitors. Temporal analyses were performed for the first 5 days of hospitalization by using locally estimated scatterplot smoothing for less than 1,000 observations and generalized additive models with integrated smoothness estimation for more than 1,000 observations.

RESULTS

A total of 138 intracranial pressure-monitored patients with TBI (median 5.0 [1.9-12.8] years; 65% boys; admission Glasgow Coma Scale score 4 [3-7]; mortality 18%), 71 with PbtO2 monitors and 67 without PbtO2 monitors were included. Distinct patterns in PbtO2, PaO2, and PbtO2/PaO2 were evident between survivors and nonsurvivors over the first 5 days of hospitalization. Time-series analyses showed lower PbtO2 values on day 1 and days 3-5 and lower PbtO2/PaO2 ratios on days 1, 2, and 5 among patients who died. Analysis of receiver operating characteristics curves using Youden's index identified a PbtO2 of 30 mm Hg and a PbtO2/PaO2 ratio of 0.12 as the cut points for discriminating between survivors and nonsurvivors. Univariate logistic regression identified PbtO2 < 30 mm Hg, hyperoxemia (PaO2 ≥ 300 mm Hg), and PbtO2/PaO2 ratio < 0.12 to be independently associated with mortality.

CONCLUSIONS

Lower PbtO2, higher PaO2, and lower PbtO2/PaO2 ratio, consistent with impaired oxygen diffusion into brain tissue, were associated with mortality in this cohort of children with severe TBI. These results corroborate our prior work that suggests targeting a higher PbtO2 threshold than recommended in current guidelines and highlight the potential use of the PbtO2/PaO2 ratio in the management of severe pediatric TBI.

Risk factors for central venous catheter-associated deep venous thrombosis in pediatric critical care settings identified by fusion model

Background

An increase in the incidence of central venous catheter (CVC)-related thrombosis (CRT) has been reported in pediatric intensive care patients over the past decade. Risk factors for the development of CRT are not well understood, especially in children. The study objective was to identify potential clinical risk factors associated with CRT with novel fusion machine learning models.

Methods

Patients aged 0–18 who were admitted to intensive care units from December 2015 to December 2018 and underwent at least one CVC placement were included. Two fusion model approaches (stacking and blending) were used to build a better performance model based on three widely used machine learning models (logistic regression, random forest and gradient boosting decision tree). High-impact risk factors were identified based on their contribution in both fusion artificial intelligence models.

Results

A total of 478 factors of 3871 patients and 3927 lines were used to build fusion models, one of which achieved quite satisfactory performance (AUC = 0.82, recall = 0.85, accuracy = 0.65) in 5-fold cross validation. A total of 11 risk factors were identified based on their independent contributions to the two fusion models. Some risk factors, such as D-dimer, thrombin time, blood acid-base balance-related factors, dehydrating agents, lymphocytes and basophils were identified or confirmed to play an important role in CRT in children.

Conclusions

The fusion model, which achieves better performance in CRT prediction, can better understand the risk factors for CRT and provide potential biomarkers and measures for thromboprophylaxis in pediatric intensive care settings.

Supplementary information

The online version contains supplementary material available at 10.1186/s12959-022-00378-y.

Excessive Oxygen Supplementation in the First Day of Mechanical Ventilation Is Associated With Multiple Organ Dysfunction and Death in Critically Ill Children

OBJECTIVES

To determine if greater cumulative exposure to oxygen despite adequate oxygenation over the first 24 hours of mechanical ventilation is associated with multiple organ dysfunction syndrome at 7 days and inhospital mortality in critically ill children.

DESIGN

Retrospective, observational cohort study.

SETTING

Two urban, academic PICUs.

PATIENTS

Patients less than 18 years old who required mechanical ventilation within 3 days of admission between 2010 and 2018 (Lurie Children's Hospital) or 2010 and 2016 (Comer Children's Hospital).

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

There were 5,406 mechanically ventilated patients, of which 960 (17.8%) had multiple organ dysfunction syndrome on day 7 of admission and 319 died (5.9%) during their hospitalization. Cumulative exposure to greater amounts of supplemental oxygen, while peripheral oxygen saturation was 95% or more during the first 24 hours of mechanical ventilation was independently associated with an increased risk of both multiple organ dysfunction syndrome on day 7 and inhospital mortality after adjusting for confounders. Patients in the highest quartile of cumulative oxygen exposure had an increased odds of multiple organ dysfunction syndrome on day 7 (adjusted odds ratio, 3.9; 95% CI, 2.7-5.9) and inhospital mortality (adjusted odds ratio, 1.7; 95% CI, 1.1-2.9), when compared with those in the lowest quartile of cumulative oxygen exposure after adjusting for age, presence of multiple organ dysfunction syndrome on day 1 of mechanical ventilation, immunocompromised state, and study site.

CONCLUSIONS

Greater cumulative exposure to excess supplemental oxygen in the first 24 hours of mechanical ventilation is independently associated with an increased risk of multiple organ dysfunction syndrome on day 7 of admission and inhospital mortality in critically ill children.

Association Between Hyperoxemia and Increased Cell-Free Plasma Hemoglobin During Cardiopulmonary Bypass in Infants and Children

OBJECTIVES

To determine potential risk factors for severe hemolysis during pediatric cardiopulmonary bypass and examine whether supraphysiologic levels of oxygen and cardiopulmonary bypass duration are associated with hemolysis.

DESIGN

Prospective observational study.

SETTING

Cardiac ICU in a university-affiliated children's hospital.

PATIENTS

Greater than 1 month to less than 18 years old patients undergoing cardiopulmonary bypass for cardiac surgery.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Plasma samples from 100 patients to assess cell-free plasma hemoglobin levels were obtained at start cardiopulmonary bypass, at the end of cardiopulmonary bypass, and 2 and 24 hours after reperfusion. Arterial blood gas samples were obtained before and every 30 minutes during cardiopulmonary bypass. Patient demographics and laboratory data were collected from the electronic medical record. Plasma hemoglobin levels peaked at the end of cardiopulmonary bypass and haptoglobin levels continued to fall throughout all time points. There were 44 patients with severe hemolysis (change in cell-free plasma hemoglobin > 50 mg/dL). Younger age (odds ratio/sd 0.45 [95% CI, 0.25-0.81]) and higher mean Pao2 × cardiopulmonary bypass duration (31.11 [1.46-664.64]) were identified as risk factors for severe hemolysis in multivariable analysis. Severe hemolysis was associated with longer hospital and ICU lengths of stay as well as acute kidney injury.

CONCLUSIONS

We observed younger age and the exposure to both oxygen and duration of cardiopulmonary bypass as risk factors for hemolysis. Oxygen delivery through the cardiopulmonary bypass circuit is an easily modifiable risk factor. Its role in the production of reactive oxygen species that could alter the erythrocyte membrane deserves further examination in larger prospective studies.

Association of Arterial Hyperoxia With Outcomes in Critically Ill Children: A Systematic Review and Meta-analysis

IMPORTANCE

Oxygen supplementation is a cornerstone treatment in pediatric critical care. Accumulating evidence suggests that overzealous use of oxygen, leading to hyperoxia, is associated with worse outcomes compared with patients with normoxia.

OBJECTIVES

To evaluate the association of arterial hyperoxia with clinical outcome in critically ill children among studies using varied definitions of hyperoxia.

DATA SOURCES

A systematic search of EMBASE, MEDLINE, Cochrane Library, and ClinicalTrials.gov from inception to February 1, 2021, was conducted.

STUDY SELECTION

Clinical trials or observational studies of children admitted to the pediatric intensive care unit that examined hyperoxia, by any definition, and described at least 1 outcome of interest. No language restrictions were applied.

DATA EXTRACTION AND SYNTHESIS

The Meta-analysis of Observational Studies in Epidemiology guideline and Newcastle-Ottawa Scale for study quality assessment were used. The review process was performed independently by 2 reviewers. Data were pooled with a random-effects model.

MAIN OUTCOMES AND MEASURES

The primary outcome was 28-day mortality; this time was converted to mortality at the longest follow-up owing to insufficient studies reporting the initial primary outcome. Secondary outcomes included length of stay, ventilator-related outcomes, extracorporeal organ support, and functional performance.

RESULTS

In this systematic review, 16 studies (27 555 patients) were included. All, except 1 randomized clinical pilot trial, were observational cohort studies. Study populations included were post-cardiac arrest (n = 6), traumatic brain injury (n = 1), extracorporeal membrane oxygenation (n = 2), and general critical care (n = 7). Definitions and assessment of hyperoxia differed among included studies. Partial pressure of arterial oxygen was most frequently used to define hyperoxia and mainly by categorical cutoff. In total, 11 studies (23 204 patients) were pooled for meta-analysis. Hyperoxia, by any definition, showed an odds ratio of 1.59 (95% CI, 1.00-2.51; after Hartung-Knapp adjustment, 95% CI, 1.05-2.38) for mortality with substantial between-study heterogeneity (I2 = 92%). This association was also found in less heterogeneous subsets. A signal of harm was observed at higher thresholds of arterial oxygen levels when grouped by definition of hyperoxia. Secondary outcomes were inadequate for meta-analysis.

CONCLUSIONS AND RELEVANCE

These results suggest that, despite methodologic limitations of the studies, hyperoxia is associated with mortality in critically ill children. This finding identifies the further need for prospective observational studies and importance to address the clinical implications of hyperoxia in critically ill children.

Innovations and adaptations in neonatal and pediatric respiratory care for resource constrained settings

Respiratory disease is a leading cause of death in children under 5 years of age worldwide, and most of these deaths occur in low- to middle-income countries (LMICs) where advanced respiratory care technology is often limited. Much of the equipment required to provide advanced respiratory care is unavailable in these areas due to high costs, the need for specialty trained personnel, and myriad other resource constraints that limit uptake and sustainable use of these devices, including reliable access to electricity, sensitive equipment needing frequent maintenance, single-patient-use supplies, and lack of access to sterilization equipment. Compounding the problem, pediatrics is uniquely challenging in that one size does not fit all, or even most patients. Despite these substantial barriers, numerous innovations in respiratory care technology have been made in recent years that have brought increasing access to high quality respiratory care in some of the most remote areas of the world. In this article, we intend to review the global burden of respiratory diseases for children, highlight the prototypical innovations that have been made in bringing respiratory care to LMICs, spotlight some of the technologies being actively developed to improve respiratory care in resource-constrained settings, and conclude with a discussion highlighting areas where further innovation is still needed.

Hyperoxia after pediatric cardiac arrest: Association with survival and neurological outcomes

OBJECTIVE

To evaluate the association between hyperoxia in the first 24 hours after in-hospital pediatric cardiac arrest and mortality and poor neurological outcome.

METHODS

This is a retrospective cohort study of inpatients in a freestanding children's hospital. We included all patients younger than 18 years of age with in-hospital cardiac arrest between December 2012 and December 2019, who achieved return of circulation (ROC) for longer than 20 minutes, survived at least 24 hours after cardiac arrest, and had documented PaO2 or SpO2 during the first 24 hours after ROC. Hyperoxia was defined as having at least one level of PaO2 above 200 mmHg in the first 24 hours after cardiac arrest.

RESULTS

There were 187 patients who met eligibility criteria, of whom 48% had hyperoxia during the first 24 hours after cardiac arrest. In-hospital mortality was 41%, with similar mortality between oxygenation groups (hyperoxia 45% vs no hyperoxia 38%). We did not observe an association between hyperoxia and in-hospital mortality or poor neurological outcome after adjusting for confounders (odds ratio 1.2, 95% confidence interval 0.5-2.8). On sensitivity analysis using two additional cutoffs of PaO2 (>150 mmHg and > 300 mmHg), there was also no association with in-hospital mortality or poor neurological outcome after adjusting for confounders. Similarly, on multivariable logistic regression using SpO2 > 99% as the exposure, there was no difference in the frequency of death or poor neurological outcome at hospital discharge.

CONCLUSION

Hyperoxia after pediatric cardiac arrest was common and was not associated with worse in-hospital outcomes.

Hyperoxemia Is Associated With Mortality in Critically Ill Children

Multiple studies among adults have suggested a non-linear relationship between arterial partial pressure of oxygen (PaO₂) and clinical outcomes. Meta-analyses in this population suggest that high levels of supplemental oxygen resulting in hyperoxia are associated with mortality. This mini-review focuses on the non-neonatal pediatric literature examining the relationship between PaO₂ and mortality. While only one pilot pediatric randomized-controlled trials exists, over the past decade, there have been at least eleven observational studies examining the relationship between PaO₂ values and mortality in critically ill children. These analyses of mixed-case pediatric ICU populations have generally reported a parabolic (“u-shaped”) relationship between PaO₂ and mortality, similar to that seen in the adult literature. However, the estimates of the point at which hyperoxemia becomes deleterious have varied widely (300–550 mmHg). Where attempted, this effect has been robust to analyses restricted to the first PaO₂ value obtained, those obtained within 24 h of admission, anytime during admission, and the number of hyperoxemic blood gases over time. These findings have also been noted when using various methods of risk-adjustment (accounting for severity of illness scores or complex chronic conditions). Similar relationships were found in the majority of studies restricted to patients undergoing care after cardiac arrest. Taken together, the majority of the literature suggests that there is a robust parabolic relationship between PaO₂ and risk-adjusted pediatric ICU mortality, but that the exact threshold at which hyperoxemia becomes deleterious is unclear, and likely beyond the typical target value for most clinical indications. Findings suggest that clinicians should remain judicious and thoughtful in the use of supplemental oxygen therapy in critically ill children.

Hyperoxia During Cardiopulmonary Bypass Is Associated With Mortality in Infants Undergoing Cardiac Surgery

OBJECTIVES

Patients undergoing cardiac surgery using cardiopulmonary bypass have variable degrees of blood oxygen tension during surgery. Hyperoxia has been associated with adverse outcomes in critical illness. Data are not available regarding the association of hyperoxia and outcomes in infants undergoing cardiopulmonary bypass. We hypothesize that among infants undergoing cardiac surgery, hyperoxia during cardiopulmonary bypass is associated with greater odds of morbidity and mortality.

DESIGN

Retrospective study.

SETTING

Single center at an academic tertiary children's hospital.

PATIENTS

All infants (< 1 yr) undergoing cardiopulmonary bypass between January 1, 2015, and December 31, 2017, excluding two patients who were initiated on extracorporeal membrane oxygenation in the operating room.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

The study included 469 infants with a median age of 97 days (interquartile range, 14-179 d), weight 4.9 kg (interquartile range, 3.4-6.4 kg), and cardiopulmonary bypass time 128 minutes (interquartile range, 91-185 min). A Pao2 of 313 mm Hg (hyperoxia) on cardiopulmonary bypass had highest sensitivity with specificity greater than 50% for association with operative mortality. Approximately, half of the population (237/469) had hyperoxia on cardiopulmonary bypass. Infants with hyperoxia were more likely to have acute kidney injury, prolonged postoperative length of stay, and mortality. They were younger, weighed less, had longer cardiopulmonary bypass times, and had higher Society of Thoracic Surgeons and the European Association for Cardio-Thoracic Surgery mortality scores. There was no difference in sex, race, preoperative creatinine, single ventricle physiology, or presence of genetic syndrome. On multivariable analysis, hyperoxia was associated with greater odds of mortality (odds ratio, 4.3; 95% CI, 1.4-13.2) but failed to identify an association with acute kidney injury or prolonged postoperative length of stay. Hyperoxia was associated with greater odds of mortality in subgroup analysis of neonatal patients.

CONCLUSIONS

Hyperoxia occurred in a substantial portion of infants undergoing cardiopulmonary bypass for cardiac surgery. Hyperoxia during cardiopulmonary bypass was an independent risk factor for mortality and may be a modifiable risk factor. Furthermore, hyperoxia during cardiopulmonary bypass was associated with four-fold greater odds of mortality within 30 days of surgery. Hyperoxia failed to identify an association with development of acute kidney injury or prolonged postoperative length of stay when controlling for covariables. Validation of our data among other populations is necessary to better understand and elucidate potential mechanisms underlying the association between excess oxygen delivery during cardiopulmonary bypass and outcome.

Maximum Pao2 in the First 72 Hours of Intensive Care Is Associated With Risk-Adjusted Mortality in Pediatric Patients Undergoing Mechanical Ventilation

A relationship between Pao₂ and mortality has previously been observed in single-center studies. We performed a retrospective cohort study of the Pediatric Health Information System plus database including patients less than or equal to 21 years old admitted to a medical or cardiac ICU who received invasive ventilation within 72 hours of admission. We trained and validated a multivariable logistic regression mortality prediction model with very good discrimination (C-statistic, 0.86; 95% CI, 0.79–0.92; area under the precision-recall curve, 0.39) and acceptable calibration (standardized mortality ratio, 0.96; 95% CI, 0.75–1.23; calibration belt p = 0.07). Maximum Pao₂ measurements demonstrated a parabolic (“U-shaped”) relationship with PICU mortality (Box-Tidwell p < 0.01). Maximum Pao₂ was a statistically significant predictor of risk-adjusted mortality (standardized odds ratio, 1.27; 95% CI, 1.23–1.32; p < 0.001). This analysis is the first multicenter pediatric study to identify a relationship between the extremes in Pao₂ values and PICU mortality. Clinicians should remain judicious in the use of oxygen when caring for children.

Early Hyperoxemia and Outcome Among Critically Ill Children

OBJECTIVE

To identify whether a high PaO2 (hyperoxemia) at the time of presentation to the PICU is associated with in-hospital mortality.

DESIGN

Single-center observational study.

SETTING

Quaternary-care PICU.

PATIENTS

Encounters admitted between January 1, 2009, and December 31, 2018.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Encounters with a measured PaO2 were included. To account for severity of illness upon presentation, we calculated a modified Pediatric Risk of Mortality IV score excluding PaO2 for each encounter, calibrated for institutional data. Logistic regression was used to determine whether hyperoxemia (PaO2 ≥ 300 torr [39.99 kPa]) in the 12 hours surrounding PICU admission was associated with in-hospital mortality. We reperformed our analysis using a cutoff for hyperoxemia obtained by comparisons of observed versus predicted mortality when encounters were classified by highest PaO2 in 50 torr (6.67 kPa) bins. Results are reported as adjusted odds ratios with 95% CIs. Of 23,719 encounters, 4,093 had a PaO2 recorded in the period -6 to +6 hours after admission. Two hundred seventy-four of 4,093 (6.7%) had in-hospital mortality. The prevalence of hyperoxemia increased with rising modified Pediatric Risk of Mortality IV and was not associated with mortality in multivariable models (adjusted odds ratio, 1.38; 95% CI, 0.98-1.93). When using a higher cutoff of hyperoxemia derived from comparison of observed versus predicted rates of mortality of greater than or equal to 550 torr (73.32 kPa), hyperoxemia was associated with mortality (adjusted odds ratio, 2.78; 95% CI, 2.54-3.05).

CONCLUSIONS

A conventional threshold for hyperoxemia at presentation to the PICU was not associated with in-hospital mortality in a model using a calibrated acuity score. Extreme states of hyperoxemia (≥ 73.32 kPa) were significantly associated with in-hospital mortality. Prospective research is required to identify if hyperoxemia before and/or after PICU admission contributes to poor outcomes.

A Low-Resource Oxygen Blender Prototype for Use in Modified Bubble CPAP Circuits

Continuous positive airway pressure (CPAP) is a method of respiratory support used around the world to treat children with lower respiratory tract infections (LRTI) (WHO, 2016, Oxygen Therapy for Children, World Health Organization, Geneva, Switzerland, Report). Bubble continuous positive airway pressure (bCPAP) is an effective form of CPAP that is currently used in both high- and low-resource countries. Low-cost, modified bCPAP devices have been designed as an ideal form of CPAP in low-resource areas (Bjorklund, A. R., Mpora, B. O., Steiner, M. E., Fischer, G., Davey, C. S., and Slusher, T. M., 2018, “Use of a Modified Bubble Continuous Positive Airway Pressure (bCPAP) Device for Children in Respiratory Distress in Low- and Middle-Income Countries: A Safety Study,” Paediatr. Int. Child Health, 39(3), pp. 1–8). However, patients in low-resource settings undergoing bCPAP treatment are often given pure oxygen, which has been linked to retinopathy of prematurity, cardiovascular complications, and patient mortality (Rodgers, J. L., Iyer, D., Rodgers, L. E., Vanthenapalli, S., and Panguluri, S. K., 2019, “Impact of Hyperoxia on Cardiac Pathophysiology,” J. Cell. Physiol., 234(8), pp. 1–9; Ramgopal, S., Dezfulian, C., Hickey, R. W., Au, A. K., Venkataraman, S., Clark, R. S. B., and Horvat, C. M., 2019, “Association of Severe Hyperoxemia Events and Mortality Among Patients Admitted to a Pediatric Intensive Care Unit,” JAMA Network Open, 2(8), p. e199812). This problem is typically avoided by using commercial oxygen blenders, which can titrate down the concentration of oxygen delivered to the minimum needed; however, these blenders can cost nearly 1000 USD and are almost always unavailable in low-resource settings. The lack of available low-cost oxygen blenders compatible with modified bCPAP circuits creates a barrier for low-resource hospitals to be able to provide blended oxygen to patients. There is a need for a low-cost oxygen blender for use in low-resource settings. We propose a passive oxygen blender that operates via entrainment of atmospheric air. The device can easily be assembled in low-resource areas using a 22 gauge hypodermic needle, two 3 cc syringes, tape or super glue, and the materials required for bCPAP—for approximately 1.40 USD per device. The blender has not been clinically tested yet, but can achieve oxygen concentrations as low as 60% with bCPAP levels of 5 cm H2O (490 Pa) when used in a standard bCPAP circuit without a patient.