Expanded application of extracorporeal membrane oxygenation in a pediatric surgery practice

Mechanical Ventilation in Pediatric and Neonatal Patients

Pediatric acute respiratory distress syndrome (PARDS) remains a significant cause of morbidity and mortality, with mortality rates as high as 50% in children with severe PARDS. Despite this, pediatric lung injury and mechanical ventilation has been poorly studied, with the majority of investigations being observational or retrospective and with only a few randomized controlled trials to guide intensivists. The most recent and universally accepted guidelines for pediatric lung injury are based on consensus opinion rather than objective data. Therefore, most neonatal and pediatric mechanical ventilation practices have been arbitrarily adapted from adult protocols, neglecting the differences in lung pathophysiology, response to injury, and co-morbidities among the three groups. Low tidal volume ventilation has been generally accepted for pediatric patients, even in the absence of supporting evidence. No target tidal volume range has consistently been associated with outcomes, and compliance with delivering specific tidal volume ranges has been poor. Similarly, optimal PEEP has not been well-studied, with a general acceptance of higher levels of F_iO₂ and less aggressive PEEP titration as compared with adults. Other modes of ventilation including airway pressure release ventilation and high frequency ventilation have not been studied in a systematic fashion and there is too little evidence to recommend supporting or refraining from their use. There have been no consistent outcomes among studies in determining optimal modes or methods of setting them. In this review, the studies performed to date on mechanical ventilation strategies in neonatal and pediatric populations will be analyzed. There may not be a single optimal mechanical ventilation approach, where the best method may simply be one that allows for a personalized approach with settings adapted to the individual patient and disease pathophysiology. The challenges and barriers to conducting well-powered and robust multi-institutional studies will also be addressed, as well as reconsidering outcome measures and study design.

Respiratory support with venovenous extracorporeal membrane oxygenation during stent placement for the palliation of critical airway obstruction: case series analysis

BACKGROUND

Venovenous extracorporeal membrane oxygenation (VV ECMO) is used to support gas transfer of patients suffering from respiratory failure during various procedures. The purpose of this study was to evaluate the technical feasibility and safety of fluoroscopic stent placement under respiratory support with VV ECMO in patients with critical airway obstructions.

METHODS

We reviewed the records of 17 patients (14 male and 3 female; mean age: 63 years; range, 30-82 years) who underwent self-expandable metallic stent (SEMS) placement under VV ECMO respiratory support for critical airway obstruction caused by malignant (n=16) or benign (n=1) etiology.

RESULTS

Fluoroscopic placement of SEMS was successful in all patients (100%) with no procedure-related complications. During a mean follow-up of 83 days (range, 10-367 days), 15 (88.2%) of 17 patients showed improvement of Hugh-Jones grades (from 4.7±0.4 to 3.1±0.9, P<0.001). Removal of the endotracheal tube was possible in 11 (84.6%) of 13 patients. Weaning off ECMO was successful in all patients. The ECMO-related and stent-related complication rates were 11.7% (n=2) and 29.4% (n=5), respectively, all successfully managed by additional interventions. Indications for VV ECMO included failure of mechanical ventilation in 13 (76.5%) patients, and orthopnea in 4 (23.5%) patients.

CONCLUSIONS

Fluoroscopic stent placement under VV ECMO respiratory support can be successfully performed in patients with critical airway obstruction, especially in cases of respiratory distress despite ventilation support and an inability to lie in a supine position. However, further studies will be needed to validate the standardized methods and specific indications.

Insensible water loss from the Jostra Quadrox D oxygenator: an in vitro study

Extracorporeal membrane oxygenation (ECMO) has been shown to improve outcomes in neonatal patients with respiratory and/or cardiac failure. Insensible water loss is defined as water loss via evaporation from the skin and respiration. Fluid and electrolyte balance are a primary concern and very challenging in the neonatal patient population. Hypernatremia can result from untreated insensible water loss, leading to possible cerebral complications. A new type of fiber used in the Jostra Quadrox D oxygenator has recently been approved for use in the United States of America. This oxygenator uses a polymethylpentene closed hollow-fiber technology and has been approved for six hours of continuous use by the Federal Drug Administration. The closed hollow-fiber technology may be advantageous for extended use due to the fact that it is a true membrane and plasma leakage will not occur across its surface. The Jostra Quadrox D is an adult-sized oxygenator with a surface area of 1.8 M2. The aim of this study is to discover what the insensible water loss will be from the Jostra Quadrox D when used at blood flows which would mimic those used for a neonatal ECMO patient. The median insensible water loss from the Quadrox D oxygenator at a gas flow rate of two liters per minute(LPM) was 4.0 ± 0.2 ml/hour, at five LPM was 9.8 ± 0.4 ml/hour and at 10 LPM was 20.6 ± 0.7 ml/hour. The daily evaporative water loss from the Jostra Quadrox D can be estimated to be 48.0 ± 2.1 ml for each LPM of sweep gas with a normal saline pump flow rate of 500 ml/min.

Diverse Morbidity and Mortality Among Infants Treated with Venoarterial Extracorporeal Membrane Oxygenation

Background: Venoarterial extracorporeal membrane oxygenation (VA-ECMO) is utilized for cardiopulmonary failure. We aimed to qualify and quantify the predictors of morbidity and mortality in infants requiring VA-ECMO.

Methods: Data was collected from 170 centers participating in the extracorporeal life support organization (ELSO) registry. Relationships between in-hospital mortality and risk factors were assessed using logistic regression. Survival was defined as being discharged from the hospital.

Results: Six hundred and sixty-two eligible records were reviewed. Mortality occurred in 303 (46%) infants. Congenital diaphragmatic hernia patients (OR=3.83, 95% CI 1.96-7.49, p<0.001), cardiac failure with associated shock (OR= 2.90, 95% CI 1.46-5.77, p=0.002), and pulmonary failure including respiratory distress syndrome (OR=4.06, 95% CI 1.72-9.58, p=0.001) had the highest odds of mortality in this cohort. Birth weight (BW) < 3 kg (OR=1.83, 95% CI 1.21-2.78, p=0.004), E-CPR (OR=3.35, 95% CI 1.57-7.15, p=0.002), hemofiltration (OR=2.04, 95% CI 1.32-3.16, p=0.001), and dialysis (OR=6.13, 95% CI 1.70-22.1, p<0.001) were all independent predictors of mortality.

Conclusion: Infants requiring VA-ECMO experience diverse sequelae and their mortality are high.

Chest computed tomography in children undergoing extra-corporeal membrane oxygenation: a 9-year single-centre experience

We retrospectively reviewed the imaging findings, indications, technique and clinical impact in children who had undergone chest CT while undergoing extra-corporeal membrane oxygenation (ECMO). Radiology and ECMO databases were searched to identify all 19 children who had undergone chest CT (20 scans in total) while on ECMO at our institution between May 2003 and May 2012. We reviewed all CT scans for imaging findings. Chest CT is performed in a minority of children on ECMO (4.5% in our series). Timing of chest CT following commencement of ECMO varied among patient groups but generally it was performed earlier in the neonatal group. Clinically significant imaging findings were found in the majority of chest CT scans. Many scans contained several findings, with most cases demonstrating parenchymal or pleural abnormalities. Case examples illustrate the spectrum of imaging findings, including underlying pathology such as necrotising pneumonia and severe barotrauma, and ECMO-related complications such as tension haemothoraces and cannula migration. The results of chest CT led to a change in patient management in 16 of 19 children (84%). There were no adverse events related to patient transfer. An understanding of scan technique and awareness of potential findings is important for the radiologist to provide prompt and optimal image acquisition and interpretation in appropriate patients.

Updates in the general approach to the pediatric poisoned patient

Poison prevention remains essential to prevent the most vulnerable population from becoming exposed to potentially lethal toxins. The evaluation of a child presumed to have been exposed to a toxic substance should include a precise history of the exposure, a physical examination, and knowledge of current ingestions and recreational practices. New treatments and research guiding therapy continue to evolve. Poison centers and medical toxicologists can be consulted to assist with the diagnosis of medicinal/drug overdoses, for advice about the pitfalls inherent in stabilizing children who have been exposed to toxic compounds, and for treatment recommendations based on the latest research.

Early administration of intratracheal surfactant (calfactant) after hydrocarbon aspiration

Hydrocarbon ingestions account for a substantial number of accidental poisonings; when aspirated, it can lead to severe pneumonitis. Treatment for severe pneumonitis is generally supportive, and outcomes are frequently poor. We report here the case of a 19-month-old girl who was treated successfully with early administration of exogenous surfactant for acute respiratory distress syndrome secondary to aspiration of lamp oil. Approximately 7 hours after aspiration, she required mechanical ventilation and had an oxygenation index (OI) of 13.2. Approximately 10 hours after ingestion, exogenous surfactant (calfactant) was instilled intratracheally, after which her OI improved markedly to 4.3. She received a second dose ∼19 hours after ingestion, after which her OI remained at <5 and she was progressively weaned from mechanical ventilation. She was extubated 64 hours after the ingestion with no residual lung disease. This case illustrates the importance of considering exogenous surfactant therapy early in the course of acute respiratory failure secondary to hydrocarbon aspiration. Because of the putative mechanisms of lung injury involved in hydrocarbon aspiration, surfactant-replacement therapy is a reasonable therapeutic intervention based on pathophysiologic rationale.

Predictors of outcome for children requiring respiratory extra-corporeal life support: implications for inclusion and exclusion criteria

OBJECTIVES

A range of children receive extra-corporeal life support (ECLS) for respiratory failure, but there is little published data on this group. Our aims were: (1) to analyse predictors of outcome and (2) comment on inclusion and exclusion criteria.

DESIGN

Retrospective review.

SETTING

Tertiary ECLS centre.

PATIENTS

A total of 124 children categorised as 'paediatric respiratory ECLS' from July 1992 to December 2005.

RESULTS

Fifty-three percent of children had one or more co-morbid conditions; the median age was 10.1 (IQR 3-34) months; the median ECLS duration was 9 (IQR 5-17) days; survival to discharge was 62% and at 1 year was 59%. Although survival varied according to primary reason for ECLS (range 36-100%), after adjustment for this, the presence of a co-morbid condition was unrelated to mortality (OR = 1.49, 95% CI 0.65, 3.42, P = 0.34) Predictors of mortality were increased pre-ECLS oxygenation index (OR = 1.09, 95% CI 1.00, 1.18, P = 0.05) and shock (OR 2.53, 95% CI 1.21, 5.28, P = 0.01). The relationship between mortality and end organ dysfunction (OR 2.12, 95% CI 0.89, 5.02, P = 0.09) and greater number of pre-ECLS ventilator days (OR 1.10, 95% CI 0.99, 1.22, P = 0.08) was less conclusive.

CONCLUSIONS

Pre-existing co-morbid conditions may predispose children to develop severe respiratory failure but with careful case selection, do not appear to reduce the chance of survival. Severity of pulmonary dysfunction determined by OI and shock were key predictors of outcome and should remain important determinants of referral for ECLS.

The Role of Imaging During Extracorporeal Membrane Oxygenation in Pediatric Respiratory Failure

OBJECTIVE

Extracorporeal membrane oxygenation (ECMO) is increasingly widely used in pediatric respiratory failure. Despite playing a key part in patient management during ECMO, the role of radiology is not widely reported. We discuss the principles of ECMO support and the normal imaging appearances. Radiologic findings arising from the complications of ECMO are highlighted.

CONCLUSION

Radiology has a central role in establishing well-designed imaging protocols and vigilant reporting of ECMO apparatus positions and complications.