Preliminary report: extracorporeal lung support for neonatal acute respiratory failure

Tidal Flow Perfusion for the Artificial Placenta: A Paradigm Shift

The modalities of vascular access for the extracorporeal artificial placenta (AP) have undergone many iterations over the past decade. We hypothesized that single lumen cannulation (SLC) of the jugular vein using tidal flow extracorporeal life (ECLS) support is a feasible alternative to venovenous (VV) umbilical-jugular cannulation and double lumen cannulation (DLC) and can maintain fetal circulation, stable hemodynamics, and adequate gas exchange for 24 hours. After in vitro evaluation of the tidal flow system, six preterm lambs at estimated gestational age 118-124 days (term 145 days) were delivered and underwent VV-ECLS. Three were supported using DLC and three with SLC utilizing tidal flow AP support. Hemodynamics, circuit flow, and gas exchange were monitored. Target fetal parameters were as follows: mean arterial pressure 40-60 mmHg, heart rate 140-240 beats per minute (bpm), SatO2% 60-80%, PaO2 25-50 mmHg, PaCO2 30-55 mmHg, oxygen delivery >5 ml O2/dl/kg/min, and circuit flow 100 ± 25 ml/kg/min. All animals survived 24 hours and maintained fetal circulation with stable hemodynamics and adequate gas exchange. Parameters of the tidal flow group were comparable with those of DLC. Single lumen jugular cannulation using tidal flow is a promising vascular access strategy for AP support. Successful miniaturization holds great potential for clinical translation to support extremely premature infants.

Extracorporeal Membrane Oxygenation with Veno-Venous Bypass and Apneic Oxygenation for Treatment of Severe Neonatal Respiratory Failure

Seven newborn infants with life-threatening respiratory failure were treated with veno-venous (V-V) extracorporeal lung support and apneic oxygenation after maximal ventilatory and pharmacological treatment failed. Diagnosis were meconium aspiration syndrome in 3 cases, respiratory distress syndrome in 2, sepsis in 1, congenital diaphragmatic hernia in 1. Before ECMO 6 infants received tolazoline, 4 surfactant, 3 high frequency ventilation, 1 prostaglandin E, 1 epoprostenol, 2 nitric oxide. Newborns were highly hypoxemic at admission and all but one underwent rescue cannulation. V-V bypass was performed with a single lumen single cannula and tidal flow was generated by an alternating clamp using a non-occlusive roller pump. The mean duration of bypass was 162, 4±162.3 hours and infants were extubated 94.5±74.8 hours after decannulation. Five newborns survived and two died. Growth and neurologic development of the older children is normal. The extracorporeal lung support with V-V bypass associated with apneic oxygenation was effective in reversing severe neonatal respiratory failure unresponsive to maximal ventilatory and pharmacological support. An early referral, prior to meeting ECMO criteria, is important in order to avoid hypoxic complications preceding ECMO.

[Particularities of ECMO in acute respiratory distress syndrome in pediatrics]

Les techniques de circulation extracorporelle sont utilisées en pédiatrie dans les syndromes de détresse respiratoire aiguë (SDRA) les plus graves depuis les années 1980. Les données du registre international de l’Extracorporeal Life Support Organization révèlent plus 5 000 enfants placés en extracorporeal membrane oxygenation (ECMO) en 2012 avec une augmentation du nombre de cas annuels depuis l’épidémie de 2009. La survie, de 56 %, est stable alors que le nombre d’enfants avec des comorbidités augmente grâce aux améliorations apportées au matériel. Bien que nous ne disposions pas d’études randomisées, ces résultats encouragent à proposer l’ECMO dans l’arsenal thérapeutique du SDRA de l’enfant. Si les techniques veinoveineuses doivent être privilégiées dans les affections respiratoires, l’ECMO veinoartérielle peut être nécessaire et reste d’une utilisation fréquente chez l’enfant (50 % des cas). En pédiatrie, les particularités techniques sont liées d’une part aux particularités physiologiques de l’enfant et d’autre part aux contraintes dues au matériel proposé selon les différentes catégories d’âge. L’ECMO est une technique de recours lourde qui nécessite une expertise à la fois technique et pédiatrique spécialisée en raison de ce terrain particulier.

A pilot study comparing two polymethylpentene extracorporeal membrane oxygenators

OBJECTIVE

We compared two polymethylpentene oxygenators being used in our unit: the Maquet Quadrox-iD paediatric and the Medos Hilite 800LT.

STUDY DESIGN

A mono-centric, prospective pilot study was conducted on ten consecutive newborn patients who had been admitted to our hospital service for extracorporeal circulation (EC) treatment. We examined the rate of oxygen transfer, the CO2 removal capacity and the average sweep gas flow required to produce this result. We also assessed the disturbances of haemostasis, the need for labile blood products and the membrane oxygenator lifetime and cost of use.

CONCLUSIONS

According to our study, it seems to us that Medos Hilite 800LT membrane oxygenators demonstrate greater oxygen transfer and CO2 removal capacity than Maquet Quadrox-iD paediatric membrane oxygenators, at a similar cost. These results lead us to conclude that it is reasonable to continue using Medos Hilite 800LT membrane oxygenators. A broader comparison study would be necessary in order to support these initial results.

Survie et devenir clinique des nouveau-nés mis en assistance respiratoire extracorporelle

OBJECTIVES

To assess the prognosis of newborn infants with refractory hypoxemia who required extracorporeal membrane oxygenation (ECMO).

METHODS

Eighty-nine newborn infants treated by ECMO during more than 24 hours over a 8-year period (1996-2003) were included in this observational cohort study with a 9-month and 24-month evaluation.

RESULTS

Respiratory failure mainly resulted from meconium aspiration syndrome (MAS, 43%), congenital diaphragmatic hernia (CDH, 15%) and sepsis (15%). Overall survival at hospital discharge was 67%. Infants with MAS had the best survival rate (82%) and those with CDH had the worst (46%). Of the remaining 60 survivors, 53% remained oxygen dependent at 28 days and 33% at 45 days. At the age of 2 years, only 1 infant remained oxygen dependent (but did not required oxygen at 3 years) and only 3 infants had significant neurodevelopmental problems. CDH group was associated with a prolonged duration in supplementary oxygen (P<0.001) and a prolonged duration for tube feeding (P=0.01) as compared with other diagnoses. Regarding neurologic outcome, CDH infants had the poorer neurological acquisition rate at 9 months but a very good evolution by the time of the 24-month evaluation.

CONCLUSIONS

Morbidity in ECMO survivors is low considering the severity of illness in the newborn period, mainly related to pulmonary and feeding dysfunctions during the first months, in particular for the CDH group. Outcome at the age of 2 years of CDH infants is most often favourable regarding growth and neurodevelopmental evolution.

Severe respiratory syncytial virus bronchiolitis in children: from short mechanical ventilation to extracorporeal membrane oxygenation

The objective of this study was to describe the characteristics of children who required mechanical ventilation (MV) or extracorporeal membrane oxygenation (ECMO) support for respiratory syncytial virus (RSV) bronchiolitis, and to identify risk factors associated with disease severity assessed by duration of MV, mortality and need for ECMO. Ventilated children under 1 year of age admitted for bronchiolitis were retrospectively studied over the 8-year period 1996-2003. The study population included 151 children. Of these, 38.4% were born prematurely and 8.6% had bronchopulmonary dysplasia (BPD). The mean age at initiation of MV was 61 days (+/-63 days). Infants were ventilated for a mean of 7.8 days (+/-7.5 days). Multivariate analysis revealed that prolonged duration of MV (>6 days, median value) was significantly associated with low gestational age ( P =0.02 for the group <32 weeks), requirement of neonatal oxygen supplementation ( P =0.03), BPD ( P =0.02) and positive tracheal aspiration culture ( P =0.004), in particular for Haemophilus influenzae ( P =0.03). Fourteen infants required ECMO with a mean period of MV before ECMO of 3.9 days (+/-4.5 days). Amongst these infants, the frequency of BPD was significantly higher as compared with the others ( P =0.001). Four infants died (survival rate 71.4%). The mean duration of ECMO for survivors was 12.1 days (+/-3.3 days).

CONCLUSION

The data suggest that gestational age, requirement of neonatal oxygen supplementation, bronchopulmonary dysplasia and tracheal colonisation with Haemophilus influenzae are correlated with prolonged mechanical ventilation in children with bronchiolitis. Only bronchopulmonary dysplasia was associated with a need for extracorporeal membrane oxygenation that may provide lifesaving support in infants refractory to conventional management.

Évolution sur 15 ans de l’assistance respiratoire extra-corporelle dans la prise en charge des détresses respiratoires néonatales sévères

Over the last decade, several new therapies including exogenous surfactant therapy, inhaled nitric oxide and high-frequency ventilation have become available for the treatment of neonatal pulmonary failure. The aim of this retrospective study was to evaluate to what extent these modalities have impacted the use of neonatal extracorporeal membrane oxygenation at our institution and to discuss the role of ECMO in 2003 in the management of newborn infants with refractory hypoxemia.

POPULATION AND METHODS

Two hundred and twenty six newborn infants treated by ECMO before 15 days of life and during more than 24 h in our intensive care unit were retrospectively included from two time periods (group 1: 1988-1993 and group 2: 1996-2003).

RESULTS

As compared with the first group, the number of newborns supported by ECMO in the second group has clearly diminished and their severity has increased. Overall survival rate was 80% in the first group and 69% in the second group. Meconium aspiration syndrome remains the major indication for ECMO (44%). Pulmonary sequelae, assessed by bronchopulmonary dysplasia rate (41%) are more frequent that neurologic sequelae (4.8%).

CONCLUSION

ECMO remains an useful technique in the management of newborn infants with refractory hypoxemia, with a consideration to institute ECMO early in order to increase survival rate.

Abolition of breathing rhythmicity in lambs by CO2 unloading in the first hours of life

The mechanisms responsible for the maintenance of regular breathing after initiation of breathing at birth are still poorly understood. This study was designed to test the hypothesis that removing the chemical CO2 drive would abolish breathing rhythmicity in lambs in the first hours of life. A technique of graded CO2 removal through a veno-venous extracorporeal circuit was used in five unanesthetized lambs aged from 4 to 12 hours. In all lambs, CO2 unloading invariably resulted in sustained central apnea, after a decrease in Paco, of 6.9 +/- 5.7 Torr. We were unable to find a significant relationship between the decrease in PaCO2 and PaO2 (range 35-275 Torr) at onset of apnea. During apnea, the passage from behavioral quiet sleep to arousal or to active sleep was marked by transient and weak breathing movements. We conclude that the CO2 drive, but not the behavioral states, is a major factor for maintaining breathing rhythmicity in lambs in the first hours of life.

[Current aspects of acute respiratory distress syndrome in children]

Acute respiratory distress syndrome (ARDS) is a frequent condition in pediatric intensive care units. The mortality remains high despite advances in conventional mechanical ventilation and aetiological treatment. Several animal studies have documented lung injury during mechanical ventilation with high tidal volume, and clinical investigations have shown that in human ARDS, most ventilation is distributed to the small areas of remaining aerated lung resulting in overdistension of these areas and lung injury ("baby lung" theory). Nevertheless the usefulness of extrapulmonary gas exchange remains much debated. New ventilatory strategies have been developed in order to reduce ventilator-induced lung injury and to improve systemic oxygenation but multicentric randomized clinical trials are needed before these strategies can be validated.

Simulation models in the planning of health care facilities: an application in the case of neonatal extracorporeal membrane oxygenation

OBJECTIVES

To investigate whether modelling techniques can be used in the planning of health care facilities for patients requiring neonatal extracorporeal membrane oxygenation (ECMO).

METHODS

In a micro-simulation model the number of patients that will have to be referred to facilities abroad is estimated for any number of neonatal ECMO patients presenting annually for treatment in The Netherlands, and any number of ECMO facilities. The inputs to the model consist of the number of ECMO facilities, the number of patients presenting annually, the duration of treatment and the date on which patients present for ECMO treatment. The model is estimated on data from The Netherlands for 1992, during which 29 patients were treated in three facilities. Several future scenarios are modelled, principally one in which a potential increase to 56 patients per year is foreseen.

RESULTS

The model indicates that, if such an increase takes place, no additional ECMO facilities will be necessary in The Netherlands if between three and four referrals annually to centres outside the region (or abroad) are considered acceptable and feasible. In that situation, it is expected that on 22 occasions each year two patients will be treated simultaneously, for a total of 81 days. On ten occasions, all three facilities will be occupied at the same time, for 21 days in total. On 199 days, at least one of the facilities will be occupied.

CONCLUSION

The current study shows that the acceptability and feasibility of patient referrals to ECMO centres abroad is an important issue which health care planners will have to consider. The study also shows that modelling techniques can provide information that is useful to policy-makers in the planning of health care facilities.

A cost-effectiveness analysis of neonatal ECMO using existing evidence

A cost-effectiveness analysis is part of the U.K. ECMO Trial. In preparation for this analysis, existing evidence on the costs and effectiveness of neonatal ECMO was evaluated. ECMO appears to be more costly but may be more or less effective than conventional treatment. No case can be made for introducing ECMO before trial results are available.

Reduction of ventilator settings allowed by intravenous oxygenator (IVOX) in ARDS patients

OBJECTIVE

To evaluate the possibility of reducing ventilator settings to "safe" levels by extrapulmonary gas exchange with IVOX in ARDS patients.

DESIGN

Uncontrolled open clinical study.

SETTING

Medical Intensive Care Unit of a University Hospital.

PATIENTS

6 patients with ARDS who entered into IVOX phase II clinical trials.

INTERVENTIONS

The end-point of this study was to reduce ventilator settings from the initial values, recorded on the day of inclusion, to the following: peak inspiratory pressure < 40 cmH2O, mean airway pressure < 25 cmH2O and tidal volume < 10 ml/kg. Trials to achieve this goal were made on volume-controlled ventilation within the 24 h before and after IVOX insertion. Comparison of the results achieved during these trials used Wilcoxon test.

RESULTS

Before IVOX implantation reduction of ventilator settings was not possible in the 6 patients, despite a non-significant increase in PaO2/FIO2 was achieved. IVOX permitted significant decrease in PaCO2 (from 60.5 +/- 15 to 52 +/- 11 mmHg; p = 0.02) before any modification of the ventilatory mode. After IVOX insertion, a significant decrease of the ventilator settings was performed: peak and mean airway pressures dropped from 44 +/- 10 to 36.8 +/- 6.7; p = 0.02 and from 26.3 +/- 5.6 to 22.5 +/- 3.9 cmH2O; p = 0.02, respectively. Concommitantly, PaCO2 remained unchanged and PaO2/FIO2 increased significantly from 93 +/- 28 to 117 +/- 52; p = 0.04. The interruption of oxygen flow on IVOX was associated with a slight decrease of the oxygen variables. Tolerance of IVOX was satisfactory. However, a significant decrease both in cardiac index and in pulmonary wedge pressures (from 4.5 +/- 1.2 to 3.4 +/- 9; p = 0.03 and from 16 +/- 5 to 11 +/- 2; p = 0.04, respectively) was observed.

CONCLUSION

Gas exchange achieved by IVOX allowed reduction of ventilator settings in 6 ARDS patients in whom previous attempts have failed. CO2 removal by the device, may explain these results. Efficacy of IVOX on arterial oxygenation was uncertain.

Health care technology in France

The French health care system combines freedom of medical practice with nation-wide social security. The system is centrally regulated with specific attention to technology. Prices and budgets are also regulated. Despite these controls, concerns about quality of care began to appear in France in the 1970s. At the same time, increasing costs became an issue. Health care technology assessment has been under discussion as part of the solution to these problems since the early 1980s, but little was done until 1989, when a national agency was established to develop and coordinate health care technology assessment in France. In 1991, a new law on hospitalization strengthened the role of the government in health care and required extensive evaluation activities. The law has made legal requirements for the health care system and the government at all levels, as well as establishing specific institutions and public grants to support evaluation and related activities. While further evolution of the health care system is inevitable, it seems clear that technology assessment is becoming one of the key tools for addressing problems of quality of care and rising costs.

Doppler echocardiographic assessment of pulmonary circulation in severe respiratory failure of the neonate: an aid for extracorporeal lung support indications

Extracorporeal lung support (ECLS) for newborns with acute respiratory failure has achieved increased popularity over the last decade. However, precise criteria for its implementation remain controversial. The aim of this study was to assess the value of Doppler echocardiography (DE) in 31 neonates with PaO2 of < or = 50 mmHg, FIO2 of 1, and optimal ventilation. Treatment included mechanical ventilation, paralysis, volume loading, vasopressors, and tolazoline. Markers indicative of ECLS (failure of maximal medical therapy, assessed by AaDO2 of more than 610 mm Hg beyond 8 hours and/or an oxygenation index (OI = mean airway pressure x FIO2%/postductal PaO2) of more than 40 beyond 4 to 6 hours) were present in 23 (group 1) and absent in eight (group 2). Shunt direction and systolic pulmonary arterial pressure (sPAP) calculated from tricuspid insufficiency velocity were assessed using DE. At the time of admission, sPAP was significantly higher in group 1 (62.1 v 43.7 mm Hg). On day 1, group 1 differed from group 2 in maximum sPAP value (73.2 v 44.4 mm Hg), PaCO2 (56.1 v 40 mm Hg), right-to-left shunting (85% v 25% of the patients), and pulmonary-to-systemic-pressure systolic ratio (sPAP:sSAP) (1.29 v 0.75). Patients with an sPAP:sSAP ratio of more than 1 and patients with high sPAP associated with high PaCO2 on day 1, all later (average, 10 hours later) fulfilled ECLS criteria; this suggests that DE assessment of pulmonary circulation may yield early and predictive markers of impending ECLS indication. Further confirmation of these results would help avoid unnecessary delays in ECLS implementation in newborns with severe respiratory failure.

Extracorporeal carbon dioxide removal and low-frequency positive-pressure ventilation. Improvement in arterial oxygenation with reduction of risk of pulmonary barotrauma in patients with adult respiratory distress syndrome

Mortality of the adult respiratory distress syndrome (ARDS) remains high and could be increased by pulmonary barotrauma induced by positive-pressure mechanical ventilation. Extracorporeal CO2 removal combined with low-frequency positive-pressure ventilation (ECCO2R-LFPPV) has been proposed to reduce lung injury while supporting respiratory failure. Use of this technique in 23 patients resulted in the following: a dramatic and highly significant increase of PaO2 obtained rapidly with ECCO2R-LFPPV, allowing subsequent reduction in inspired oxygen fraction; a reduction of the risk of barotrauma evidenced by a significant decrease in pressures and insufflated volumes; a survival rate of 50 percent. Bleeding was the only complication related to the technique and was the cause of death in four patients. This method allowed improvement in gas exchange along with reduction of the risk of barotrauma caused by the ventilator.

Respiratory insufficiency as a cause of neonatal death (with aspects on the potential need for ECMO treatment)

In order to identify children with fatal outcome in a neonatal intensive care unit in which only outborns are admitted, a retrospective study over a 10-year period was undertaken. The study was limited to respiratory disorders. The aim of the study was to identify lethal risk factors and thereby the need for improving therapeutic tools. Diagnoses, perinatal history, ventilator settings, blood gases, medical treatment, X-ray findings, head ultrasounds, echocardiograms, laboratory tests, surgical procedures and autopsy findings were evaluated. Severe respiratory insufficiency requiring mechanical ventilation was found in 777 patients and of these babies, 207 (27%) died while still on the ventilator. Fifty-eight patients were excluded for various reasons and thus 149 patients were included in the study. It is concluded that the mortality rate from respiratory insufficiency in the material studied was consistently high over the 10-year period. New therapeutic modalities, one of which is ECMO, are offered nowadays in clinical practice and may improve mortality and morbidity rates.

Multicenter comparison of conventional venoarterial access versus venovenous double-lumen catheter access in newborn infants undergoing extracorporeal membrane oxygenation

A multicenter trial was designed to compare standard venoarterial (VA) access versus single-catheter, venovenous access using the double-lumen catheter (VV-DLC) for newborns with respiratory failure undergoing extracorporeal membrane oxygenation (ECMO). Twenty-seven ECMO centers participated, each submitting data from the center's most recent VA cases, and data from VV-DLC cases completed upon entering the study. Data from 135 VA ECMO cases and 108 VV-DLC cases were submitted. All diagnoses resulting in neonatal respiratory failure were submitted, including patients with congenital diaphragmatic hernia (24 patients VA bypass, 11 patients VV-DLC bypass). Overall survival in patients undergoing VA bypass was 87%, while survival in patients undergoing VV-DLC bypass was 95%. Eleven patients required conversion from VV-DLC bypass to VA bypass because of insufficient support--10 of these patients survived (91% survival). Average bypass time for newborns undergoing VA bypass was 132 +/- 7.4 hours versus 100 +/- 5.1 hours for those undergoing VV-DLC bypass. Neurologic complications were more common in the VA bypass patients, although the VV patients were more stable. Hemorrhagic, cardiopulmonary, and mechanical complications, other than kinking of the DLC, occurred with approximately equal frequency in each group. In conclusion, in newborns with adequate cardiac function, venovenous ECMO using the DLC can provide the same level of support as conventional VA ECMO, without ligation of the carotid artery.

Partial and massive lung lavages in an infant with severe pulmonary alveolar proteinosis

Pulmonary alveolar proteinosis is a rare disease of unknown etiology, characterized by progressive respiratory failure. Lung lavage has only been applied in a few children. A 6 month old boy suffering from severe pulmonary alveolar proteinosis was treated with three lung lavages. The first two were partial (or unilateral) lavages; a 3.5 mm flexible bronchoscope was introduced adjacent to a no. 3 cuffed endotracheal tube. This procedure allowed selective ventilation of one lung, and contralateral lung lavage. Respiratory improvement was observed during 1 week after the two procedures. At the third lavage we used partial veno-venous extracorporeal circulation because of severe respiratory failure. A significant improvement during the 5 following months was achieved. These results suggest that both partial and total lung lavage can be performed even in young infants and they may control the declining respiratory status in severe pulmonary alveolar proteinosis.

A prospective, multicenter, randomized study of high versus low positive end-expiratory pressure during extracorporeal membrane oxygenation

To test the hypothesis that increased positive end-expiratory pressure (PEEP) could prevent deterioration of pulmonary function and lead to more rapid recovery of lung function, we randomly assigned 74 patients undergoing extracorporeal membrane oxygenation (ECMO) at four centers to receive either high (12 to 14 cm H2O) or low (3 to 5 cm H2O) PEEP. The two groups were similar in terms of weight, gestational age, diagnosis, and pre-ECMO course. All other aspects of care were identical. Dynamic lung compliance was measured at baseline and every 12 hours. Radiographs of the chest were obtained daily. Survival rates were similar in the two groups: 36 of 40 for low PEEP and 34 of 34 for high PEEP. The duration of ECMO therapy was 97.4 +/- 36.3 hours in the high-PEEP group and 131.8 +/- 54.5 hours in the low-PEEP group (p less than 0.01). Dynamic lung compliance throughout the first 72 hours of ECMO was significantly higher in patients receiving high PEEP. Radiographic appearance of the lungs correlated well with lung compliance: patients receiving high PEEP had significant deterioration of the radiographic score less frequently than those receiving low PEEP. High PEEP also was associated with significantly fewer complications. We conclude that PEEP of 12 to 14 cm H2O safely prevents deterioration of pulmonary function during ECMO and results in more rapid lung recovery than traditional lung management with low PEEP.