Higher pulmonary dead space may predict prolonged mechanical ventilation after cardiac surgery

Novel approaches to capturing and using continuous cardiorespiratory physiological data in hospitalized children

Continuous cardiorespiratory physiological monitoring is a cornerstone of care in hospitalized children. The data generated by monitoring devices coupled with machine learning could transform the way we provide care. This scoping review summarizes existing evidence on novel approaches to continuous cardiorespiratory monitoring in hospitalized children. We aimed to identify opportunities for the development of monitoring technology and the use of machine learning to analyze continuous physiological data to improve the outcomes of hospitalized children. We included original research articles published on or after January 1, 2001, involving novel approaches to collect and use continuous cardiorespiratory physiological data in hospitalized children. OVID Medline, PubMed, and Embase databases were searched. We screened 2909 articles and performed full-text extraction of 105 articles. We identified 58 articles describing novel devices or approaches, which were generally small and single-center. In addition, we identified 47 articles that described the use of continuous physiological data in prediction models, but only 7 integrated multidimensional data (e.g., demographics, laboratory results). We identified three areas for development: (1) further validation of promising novel devices; (2) more studies of models integrating multidimensional data with continuous cardiorespiratory data; and (3) further dissemination, implementation, and validation of prediction models using continuous cardiorespiratory data. IMPACT: We performed a comprehensive scoping review of novel approaches to capture and use continuous cardiorespiratory physiological data for monitoring, diagnosis, providing care, and predicting events in hospitalized infants and children, from novel devices to machine learning-based prediction models. We identified three key areas for future development: (1) further validation of promising novel devices; (2) more studies of models integrating multidimensional data with continuous cardiorespiratory data; and (3) further dissemination, implementation, and validation of prediction models using cardiorespiratory data.

Volumetric Capnography in Pediatric Extracorporeal Membrane Oxygenation: A Case Series

The kinetics of carbon dioxide elimination (VCO2) may be used as a surrogate for pulmonary blood flow. As such, we can apply a novel use of volumetric capnography to assess hemodynamic stability in patients requiring extracorporeal membrane oxygenation (ECMO). We report our experience of pediatric patients requiring ECMO support who were monitored using volumetric capnography. We describe the use of VCO2 and its association with successful decannulation. This is a prospective observational study of pediatric patients requiring ECMO support at The Children's Hospital at Montefiore from 2017 to 2019. A Respironics NM3 monitor was applied to each patient. Demographics, hemodynamic data, blood gases, and VCO2 (mL/min) data were collected. Data were collected immediately prior to and after decannulation. Over the course of the study period, seven patients were included. Predecannulation VCO2 was higher among patients who were successfully decannulated than nonsurvivors (109 [35, 230] vs. 12.4 [7.6, 17.2] mL/min), though not statistically significant. Four patients (57%) survived without further mechanical support; two (29%) died, and one (14%) was decannulated to Berlin. Predecannulation VCO2 appears to correlate with hemodynamic stability following decannulation. This case series adds to the growing literature describing the use of volumetric capnography in critical care medicine, particularly pediatric patients requiring ECMO. Prospective studies are needed to further elucidate the use of volumetric capnography and optimal timing for ECMO decannulation.

The Use of Alveolar Dead Space Fraction to Predict Postoperative Outcomes after Pediatric Cardiac Surgery: A Retrospective Study

Patients with congenital heart disease (CHD) that have surgical repair with cardiopulmonary bypass (CPB) reflect a unique population with multiple pulmonary and systemic factors that may contribute to increased alveolar dead space and low cardiac output syndrome. This study aimed to assess and compare changes in the alveolar dead space fraction (AVDSf) in the immediate postoperative period with outcomes in children with CHD who underwent repair on CPB. A single-center retrospective review study of critically ill children with CHD, younger than 18 years of age admitted to the Pediatric Intensive Care Unit (PICU) after undergoing surgical repair on CPB and received invasive mechanical ventilation for at least 24 h. One hundred and two patients were included in the study. Over the first 24 h, mean AVDSf was significantly higher in patients who had longer hospital length of stay (LOS) (> 21 days) p = 0.02, and longer duration of invasive mechanical ventilation (DMV) (> 170 h) p = 0.01. Cross-sectional analyses at 23-24 h revealed that AVDSf > 0.25 predicts mortality and DMV (p = 0.03 and P = 0.02 respectively); however, it did not predict prolonged hospital LOS. For every 0.1 increase in the AVDSf, the odds of mortality, DMV, and hospital LOS increased by 4.9 [95% CI = 1.45-16.60, p = 0.002], 2.06 [95% CI = 1.14-3.71, p = 0.01], and 1.43[95% CI = 0.84-2.45, p = 0.184], respectively. The area under the ROC curve at 23-24 h for AVDSf was 0.868 to predict mortality as an outcome. AVDSf > 0.25 at 23-24 h postoperatively was an independent predictor of mortality with sensitivity and specificity of 83% and 80%, respectively and was superior to other commonly used surrogates of cardiac output. In the immediate postoperative period of pediatric patients with CHD, high AVDSf is associated with longer hospital length of stay and duration of invasive mechanical ventilation. Increased AVDSf values at 23-24 h postoperatively is associated with mortality in patients with CHD exposed to CPB.

Use of Noninvasive Ventilation in Respiratory Failure After Extubation During Postoperative Care in Pediatrics

The purpose of this study was to determine the rate of failure of noninvasive ventilation (NIV) after cardiac surgery in pediatric patients with respiratory failure after extubation and to identify predictive success factors. This was a prospective cohort study of pediatric patients diagnosed with congenital heart disease who underwent heart surgery and used NIV. Data were collected from 170 patients with a median age of 2 months. No patient presented cardiorespiratory arrest nor any other complication during the use of NIV. The success rate for the use of NIV was 61.8%. Subjects were divided for analysis into successful and failed NIV groups. Statistical analysis used Chi-square, Mann-Whitney, and Student's t tests, which were performed after univariate and multivariate logistic regression for p < 0.05. In the multivariate analysis, only the minimal pressure gradient (OR 1.45 with p = 0.007), maximum oxygen saturation (OR 0.88 with p = 0.011), and maximum fraction of inspired oxygen (FiO₂) (OR 1.16 with p < 0.001) influenced NIV failure. The following variables did not present a statistical difference: extracorporeal circulation time (p = 0.669), pulmonary hypertension (p = 0.254), genetic syndrome (p = 0.342), RACHS-1 score (p = 0.097), age (p = 0.098), invasive mechanical ventilation duration (p = 0.186), and NIV duration (p = 0.804). In conclusion, NIV can be successfully used in children who, after cardiac surgery, develop respiratory failure in the 48 h following extubation. Although the use of higher pressure gradients and higher FiO₂ are associated with a greater failure rate for NIV use, it was found to be generally safe.

Dead space fractions in neonates following first-stage palliation for hypoplastic left heart syndrome

PURPOSE

(1) To characterise changes in dead space fraction during the first 120 post-operative hours in neonates undergoing stage 1 palliation for hypoplastic left heart syndrome, including hybrid procedure; (2) to document whether dead space fraction varied by shunt type (Blalock-Taussig shunt and Sano) and hybrid procedure; and (3) to determine the association between dead space fraction and outcomes.

METHODS

Retrospective chart review in neonates undergoing stage 1 palliation for hypoplastic left heart syndrome in a cardiac intensive care unit over a consecutive 30-month period. A linear mixed model was used to determine the differences in dead space over time. Multivariable linear regression and a multivariable linear mixed model were used to assess the association between dead space and outcomes at different time points and over time, respectively.

RESULTS

Thirty-four neonates received either a Blalock-Taussig shunt (20.5%), Sano shunt (59%), or hybrid procedure (20.5%). Hospital mortality was 8.8%. Dead space fractions in patients undergoing the hybrid procedure were significantly lower on day 1 (p = 0.01) and day 2 (p = 0.02) and increased over time. A dead space fraction &gt;0.6 on post-operative days 3-5 was significantly associated with decreased duration of mechanical ventilation in all surgical groups (p 0.6 on post-operative days 3-5 was associated with lower duration of mechanical ventilation in all surgical groups. A more comprehensive, prospective assessment of dead space in this delicate patient population would likely be beneficial in improving outcomes.

Association of dead space ventilation and prolonged ventilation after repair of tetralogy of Fallot with pulmonary atresia

BACKGROUND

We set out to determine whether patients with tetralogy of Fallot with pulmonary atresia and major aortopulmonary collateral arteries (TOF/PA/MAPCA) are at risk for elevated dead space ventilation fraction (VD/VT), and whether this is associated with prolonged mechanical ventilation. We hypothesized that elevated VD/VT (>20%) in the first 24 hours after unifocalization surgery is associated with increased risk for prolonged mechanical ventilation (>7 days).

METHODS

All patients with TOF/PA/MAPCA undergoing unifocalization surgery between January 2003 and December 2015 were included in this study. Average VD/VT was calculated over the first 24 hours after surgery. Demographic and surgical data were collected. Outcome data included duration of mechanical ventilation. Patients were separated into 2 groups: elevated VD/VT and normal DVSF. Groups were compared using the Student t test, Wilcoxon rank-sum test, and χ² test. Univariable and multivariable regression analyses were performed with VD/VT as a continuous variable to test for association.

RESULTS

Of the 265 included patients, 127 (48%) had an elevated VD/VT. The 2 groups did not differ significantly in any demographic characteristic. Patients with an elevated VD/VT had longer cardiopulmonary bypass times (P = .03), were more likely to have delayed sternal closure, and more likely to have prolonged respiratory failure (odds ratio, 2.2; 95% confidence interval, 1.2-4.0; P = .007). The percent VD/VT was associated with duration of mechanical ventilation in univariable (P < .001) and multivariable (P < .001) regression analyses when controlled for age, weight and bypass time.

CONCLUSIONS

Elevated postoperative VD/VT is associated with prolonged mechanical ventilation in patients with TOF/PA/MAPCA following unifocalization. Elevated postoperative VD/VT may be an early indicator of patients who will require prolonged duration of mechanical ventilation, allowing optimization of medical management to promote better outcomes.

Pulmonary Dead Space Fraction and Extubation Success in Children After Cardiac Surgery

OBJECTIVES

1) Determine the correlation between pulmonary dead space fraction and extubation success in postoperative pediatric cardiac patients; and 2) document the natural history of pulmonary dead space fractions, dynamic compliance, and airway resistance during the first 72 hours postoperatively in postoperative pediatric cardiac patients.

DESIGN

A retrospective chart review.

SETTING

Cardiac ICU in a quaternary care free-standing children's hospital.

PATIENTS

Twenty-nine with balanced single ventricle physiology, 61 with two ventricle physiology.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

We collected data for all pediatric patients undergoing congenital cardiac surgery over a 14-month period during the first 72 hours postoperatively as well as prior to extubation. Overall, patients with successful extubations had lower preextubation dead space fractions and shorter lengths of stay. Single ventricle patients had higher initial postoperative and preextubation dead space fractions. Two-ventricle physiology patients had higher extubation failure rates if the preextubation dead space fraction was greater than 0.5, whereas single ventricle patients had similar extubation failure rates whether preextubation dead space fractions were less than or equal to 0.5 or greater than 0.5. Additionally, increasing initial dead space fraction values predicted prolonged mechanical ventilation times. Airway resistance and dynamic compliance were similar between those with successful extubations and those who failed.

CONCLUSIONS

Initial postoperative dead space fraction correlates with the length of mechanical ventilation in two ventricle patients but not in single ventricle patients. Lower preextubation dead space fractions are a strong predictor of successful extubation in two ventricle patients after cardiac surgery, but may not be as useful in single ventricle patients.

Measurement of Dead Space Fraction Upon ICU Admission Predicts Length of Stay and Clinical Outcomes Following Bidirectional Cavopulmonary Anastomosis

OBJECTIVES

Increased alveolar dead space fraction has been associated with prolonged mechanical ventilation and increased mortality in pediatric patients with respiratory failure. The association of alveolar dead space fraction with clinical outcomes in patients undergoing bidirectional cavopulmonary anastomosis for single ventricle congenital heart disease has not been reported. We describe an association of alveolar dead space fraction with postoperative outcomes in patients undergoing bidirectional cavopulmonary anastomosis.

DESIGN

In a retrospective case-control study, we examined for associations between alveolar dead space fraction ([PaCO2 - end-tidal CO2]/PaCO2), arterial oxyhemoglobin saturation, and transpulmonary gradient upon postoperative ICU admission with a composite primary outcome (requirement for surgical or catheter-based intervention, death, or transplant prior to hospital discharge, defining cases) and several secondary endpoints in infants following bidirectional cavopulmonary anastomosis.

SETTINGS

Cardiac ICU in a tertiary care pediatric hospital.

PATIENTS

Patients undergoing bidirectional cavopulmonary anastomosis at our institution between 2011 and 2016.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Of 191 patients undergoing bidirectional cavopulmonary anastomosis, 28 patients were cases and 163 were controls. Alveolar dead space fraction was significantly higher in the case (0.26 ± 0.09) versus control group (0.17 ± 0.09; p < 0.001); alveolar dead space fraction at admission was less than 0.12 in 0% of cases and was greater than 0.28 in 35% of cases. Admission arterial oxyhemoglobin saturation was significantly lower in the case (77% ± 12%) versus control group (83% ± 9%; p < 0.05). Sensitivity and specificity for future case versus control assignment was best when prebidirectional cavopulmonary anastomosis risk factors, admission alveolar dead space fraction (AUC, 0.74), and arterial oxyhemoglobin saturation (AUC, 0.65) were combined in a summarial model (AUC, 0.83). For a given arterial oxyhemoglobin saturation, the odds of becoming a case increased on average by 181% for every 0.1 unit increase in alveolar dead space fraction. Admission alveolar dead space fraction and arterial oxyhemoglobin saturation were linearly associated with prolonged ICU length of stay, hospital length of stay, duration of mechanical ventilation, and duration of thoracic drainage (p < 0.001 for all).

CONCLUSIONS

Following bidirectional cavopulmonary anastomosis, alveolar dead space fraction in excess of 0.28 or arterial oxyhemoglobin saturation less than 78% upon ICU admission indicates an increased likelihood of requiring intervention prior to hospital discharge. Increasing alveolar dead space fraction and decreasing arterial oxyhemoglobin saturation are associated with increased lengths of stay.

Continuous Capnography in Pediatric Intensive Care

Capnography or end-tidal carbon dioxide (Etco₂) monitoring has a variety of uses in the pediatric intensive care setting. The ability to continuously measure exhaled carbon dioxide can provide vital information about airway, breathing, and circulation in critically ill pediatric patients. Capnography has diagnosis-specific applications for pediatric patients with congenital heart disease, reactive airway disease, neurologic emergencies, and metabolic derangement. This modality allows for noninvasive monitoring and has become the standard of care. This article reviews the basic principles and clinical applications of Etco₂ monitoring in the pediatric intensive care unit.

Higher Dead Space Is Associated With Increased Mortality in Critically Ill Children

OBJECTIVE

Elevated dead space has been consistently associated with increased mortality in adults with respiratory failure. In children, the evidence for this association is more limited. We sought to investigate the association between dead space and mortality in mechanically ventilated children.

DESIGN

Single-center retrospective review.

SETTING

Tertiary care pediatric critical care unit.

PATIENTS

Seven hundred twelve mechanically ventilated children with an arterial catheter.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

The end-tidal alveolar dead space fraction ((PaCO2-PETCO2)/PaCO2), a dead space marker, was calculated with each arterial blood gas. The initial end-tidal alveolar dead space fraction (first arterial blood gas after intubation) (per 0.1 unit increase: odds ratio, 1.59; 95% CI, 1.40-1.81) and day 1 mean end-tidal alveolar dead space fraction (odds ratio, 1.95; 95% CI, 1.66-2.30) were associated with mortality. The relationship between both initial and day 1 mean end-tidal alveolar dead space fraction and mortality held in multivariate modeling after controlling for any of the following individually: PaO2/FIO2, oxygenation index, 24-hour maximal inotrope score, and Pediatric Risk of Mortality III (all p<0.01), although end-tidal alveolar dead space fraction was no longer significant after controlling for the combination of oxygenation index, 24-hour maximal inotrope score, and Pediatric Risk of Mortality III. In 217 children with acute hypoxemic respiratory failure, initial end-tidal alveolar dead space fraction (per 0.1 unit increase odds ratio, 1.38; 95% CI, 1.14-1.67) and day 1 mean end-tidal alveolar dead space fraction (per 0.1 unit increase odds ratio, 1.60; 95% CI, 1.27-2.0) were associated with mortality. Day 1 mean end-tidal alveolar dead space fraction remained associated with mortality after controlling individually for any of the following in multivariate models: PaO2/FIO2, oxygenation index, and 24-hour maximal inotrope score (p≤0.02), although end-tidal alveolar dead space fraction was no longer significant after controlling for the combination of oxygenation index, 24-hour maximal inotrope score, and Pediatric Risk of Mortality III.

CONCLUSIONS

Increased dead space is associated with higher mortality in critically ill children, although it is no longer independently associated with mortality after controlling for severity of oxygenation defect, inotrope use, and severity of illness. However, because end-tidal alveolar dead space fraction is easy to calculate at the bedside, it may be useful for risk stratification and severity-of-illness scores.

Pulmonary deadspace and postoperative outcomes in neonates undergoing stage 1 palliation operation for single ventricle heart disease

OBJECTIVES

Increased pulmonary dead space fraction (VD/VT) has been associated with prolonged mechanical ventilation after surgery for congenital heart disease. The association of VD/VT with clinical outcomes in neonates undergoing stage 1 palliation for single ventricle congenital heart disease has not been reported. We describe changes in VD/VT, differences in VD/VT based on shunt type (right ventricle to pulmonary artery conduit vs modified Blalock-Taussing shunt) and association of VD/VT with postoperative outcomes in patients undergoing stage 1 palliation.

DESIGN

Retrospective chart review for demographic, hemodynamics, outcome information, and VD/VT values were collected at 6-hour intervals during the first 48 postoperative hours in neonates undergoing stage 1 palliation. VD/VT was calculated using mixed expired CO2 (PeCO2) obtained from capnography and paired arterial blood gas CO2 values.

SETTING

Cardiac ICU in a tertiary care pediatric hospital.

PATIENTS

Newborns with single ventricle congenital heart disease undergoing stage 1 palliation during 2003-2004.

MEASUREMENTS AND MAIN RESULTS

Of the 51 patients, 31 had right ventricle to pulmonary artery and 20 had Blalock-Taussing shunt. Although VD/VT was lower in the Blalock-Taussing shunt group over all time points (p = 0.02), maximal VD/VT on day 1 (0.49 ± 0.07) and on day 2 (0.46 ± 0.08) were not different between the shunt groups. VD/VT decreased significantly over time in both shunt groups (p = 0.001 for right ventricle to pulmonary artery; p < 0.001 for Blalock-Taussing shunt). Higher maximal VD/VT during first 48 postoperative hours was independently associated with fewer ventilator (β = -26.6; p = 0.035) and hospital-free days in the first month after stage 1 palliation (β = -40.4; p = 0.002) after adjusting for potential confounders in a multivariable linear regression model.

CONCLUSIONS

Increased pulmonary dead space exists early after stage 1 palliation operation for single ventricle congenital heart disease. Higher VD/VT during the first 48 postoperative hours was associated with longer duration of ventilation and hospital LOS and may be a useful marker of postoperative outcomes in this population.

[Prognostic markers of mortality after congenital heart defect surgery]

INTRODUCTION

Our aim is to identify risk factors for mortality after surgery for congenital heart disease in children, in order to establish indications for extracorporeal membrane oxygenation (ECMO).

PATIENTS AND METHODS

One hundred and eighty six children underwent cardiac surgery with extracorporeal circulation from April 2007 to June 2009. The following parameters were measured serially during their stay in Paediatric Intensive Care (PICU): Arterial and venous blood pH, pCO2, base excess, oxygen saturation, arterio-venous oxygen saturation difference, oxygen extraction ratio, ventilatory dead space and intrapulmonary shunting.

RESULTS

Hospital mortality was 13,4%. The following risk factors for mortality were identified: age, bypass time, inotropic score, lactate level upon arrival in PICU including its peak value and its rate of variation, mixed venous saturation, base excess, ventilatory dead space, oxygen extraction ratio, and intrapulmonary shunting. However, the strongest predictors of mortality were bypass time, lactate levels upon admission on PICU, and the peak lactate level. Multivariate analysis showed a lactate level of 6.3mmol/l and a high blood lactate for 24hours to be independent predictors of mortality.

CONCLUSIONS

The peak lactate level is a strong predictor of mortality. As such, it would be a useful indicator of the need for ECMO support.

The association between the end tidal alveolar dead space fraction and mortality in pediatric acute hypoxemic respiratory failure

OBJECTIVE

To investigate the relationship of markers of oxygenation, PaO2/FIO2 ratio, SpO2/FIO2 ratio, oxygenation index, oxygen saturation index, and dead space (end tidal alveolar dead space fraction) with mortality in children with acute hypoxemic respiratory failure.

DESIGN

Retrospective.

SETTING

Single-center tertiary care pediatric intensive care unit.

PATIENTS

Ninety-five mechanically ventilated children with a PaO2/FIO2 ratio <300 within 24 hrs of the initiation of mechanical ventilation.

INTERVENTIONS

None.

MAIN RESULTS

The end tidal alveolar dead space fraction, PaO2/FIO2 ratio, SpO2/FIO2 ratio, oxygenation index, and oxygen saturation index were all associated with mortality (p < .02). There was a small correlation between the end tidal alveolar dead space fraction and decreasing PaO2/FIO2 (r2 = .21) and SpO2/FIO2 ratios (r2 = .22), and increasing oxygenation index (r2= .25) and oxygen saturation index (r2 = .24). In multivariate logistic regression modeling, the end tidal alveolar dead space fraction was independently associated with mortality (p < .02). Oxygenation index, oxygen saturation index, and the end tidal alveolar dead space fraction were all acceptable discriminators of mortality with receiver operating characteristic plot area under the curves ≥ 0.7.

CONCLUSIONS

In pediatric acute hypoxemic respiratory failure, easily obtainable pulmonary specific markers of disease severity (SpO2/FIO2 ratio, oxygen saturation index, and the end tidal alveolar dead space fraction) may be useful for the early identification of children at high risk of death. Furthermore, the end tidal alveolar dead space fraction should be considered for risk stratification of children with acute hypoxemic respiratory failure, given that it was independently associated with mortality.