Alveolar-arterial oxygen gradients versus the Neonatal Pulmonary Insufficiency Index for prediction of mortality in ECMO candidates

Functional morphometry: non-invasive estimation of the alveolar surface area in extremely preterm infants

BACKGROUND

The main pathophysiologic characteristic of chronic respiratory disease following extremely premature birth is arrested alveolar growth, which translates to a smaller alveolar surface area (SA). We aimed to use non-invasive measurements to estimate the SA in extremely preterm infants.

METHODS

Paired measurements of the fraction of inspired oxygen and transcutaneous oxygen saturation were used to calculate the ventilation/perfusion ratio, which was translated to SA using Fick's law of diffusion. The SA was then adjusted using volumetric capnography.

RESULTS

Thirty infants with a median (range) gestational age of 26.3 (22.9-27.9) weeks were studied. The median (range) adjusted SA was 647.9 (316.4-902.7) cm2. The adjusted SA was lower in the infants who required home oxygen [637.7 (323.5-837.5) cm2] compared to those who did not [799.1 (444.2-902.7) cm2, p = 0.016]. In predicting the need for supplemental home oxygen, the adjusted SA had an area under the receiver operator characteristic curve of 0.815 (p = 0.017). An adjusted SA ≥688.6 cm2 had 86% sensitivity and 77% specificity in predicting the need for supplemental home oxygen.

CONCLUSIONS

The alveolar surface area can be estimated non-invasively in extremely preterm infants. The adjusted alveolar surface area has the potential to predict the subsequent need for discharge home on supplemental oxygen.

IMPACT

We describe a novel biomarker of respiratory disease following extremely preterm birth. The adjusted alveolar surface area index was derived by non-invasive measurements of the ventilation/perfusion ratio and adjusted by concurrent measurements of volumetric capnography. The adjusted alveolar surface area was markedly reduced in extremely preterm infants studied at 7 days of life and could predict the need for discharge home on supplemental oxygen. This method could be used at the bedside to estimate the alveolar surface area and provide an index of the severity of lung disease, and assist in monitoring, clinical management and prognosis.

Functional morphometry to estimate the alveolar surface area using a premature baboon model

The main respiratory pathophysiological process following premature birth is the delayed or arrested alveolar development that translates to a smaller alveolar surface area (S_A). Histological morphometry is the gold standard method to measure the S_A but requires invasive tissue sampling or the removal of the whole organ for analysis. Alternatively, the S_A could be measured in living subjects by "functional morphometry" using Fick's first law of diffusion and noninvasive measurements of the ventilation to perfusion ratio (V̇a/Q̇). We herein aim to describe a novel functional morphometric method to measure S_A using a premature baboon model. We used both functional morphometry and postmortem histological morphometry to measure S_A in 11 premature baboons born at 135 days who received intensive care treatment for 14 days. For the calculation of the S_A by functional morphology, we measured the septal wall thickness using microscopy, the alveolar arterial oxygen gradient using concurrent measurements of arterial pressure of O₂ and CO₂, and pulmonary perfusion using echocardiography and integrated Doppler signals. The median [interquartile range (IQR)] S_A using functional morphometry was 3,100 (2,080-3,640) cm² and using histological morphometry was 1,034 (634-1,210) cm² (left lung only). The S_A measured by functional morphometry was not related to the S_A measured by histological morphometry. Following linear regression analysis, the V̇a/Q̇ significantly predicted the histologically measured S_A (R² = 0.659, P = 0.002). In conclusion, functional measurements of ventilation to perfusion ratio could be used to estimate the alveolar surface area in prematurely born baboons and the ventilation perfusion ratio was the main determinant of the alveolar surface area.NEW & NOTEWORTHY The main morphological characteristic of chronic respiratory disease in prematurely born infants is the impaired/arrested alveolar growth that corresponds to a smaller aggregated alveolar surface area (S_A). This decreased S_A might be the limiting factor later in life affecting exercise capacity and quality of life. There is paucity of sensitive, noninvasive biomarkers to monitor the evolution of neonatal respiratory disease. Our noninvasive functional morphometric S_A might help to bridge the gap between pathophysiology and clinical monitoring.

Highlights from the Extracorporeal Life Support Organization Registry: 2006-2017

Extracorporeal membrane oxygenation (ECMO) is a supportive therapy for patients with severe cardiovascular or respiratory failure refractory to conventional medical therapy. Improvements in ECMO technology, easy access to ECMO devices, and a greater understanding of care of ECMO patients have led to increased utilization of ECMO. The Extracorporeal Life Support Organization (ELSO) registry was established in 1984, to collect data on patients receiving ECMO support to help improve outcomes of these patients. The registry has grown to include over 400 contributing centers from 60 countries with data for more than 90,000 patients. Many investigators have used the ELSO registry to answer clinical questions on outcomes and care of this vulnerable patient population. This report provides a brief summary of 16 peer-reviewed articles that have advanced the knowledge and treatment of neonates, children, and adults supported with ECMO using data from the ELSO registry.

Development and Validation of Extracorporeal Membrane Oxygenation Mortality-Risk Models for Congenital Diaphragmatic Hernia

The purpose of our study was to develop and validate extracorporeal membrane oxygenation (ECMO)–specific mortality risk models for congenital diaphragmatic hernia (CDH). We utilized the data from the Extracorporeal Life Support Organization Registry (2000–2015). Prediction models were developed using multivariable logistic regression. We identified 4,374 neonates with CDH with an overall mortality of 52%. Predictive discrimination (C statistic) for pre-ECMO mortality model was C = 0.65 (95% confidence interval, 0.62–0.68). Within the highest risk group, based on the pre-ECMO risk score, mortality was 87% and 75% in the training and validation data sets, respectively. The pre-ECMO risk score included pre-ECMO ventilator settings, pH, prior diaphragmatic hernia repair, critical congenital heart disease, perinatal infection, and demographics. For the on-ECMO model, mortality prediction improved substantially: C = 0.73 (95% confidence interval, 0.71–0.76) with the addition of on-ECMO–associated complications. Within the highest risk group, defined by the on-ECMO risk score, mortality was 90% and 86% in the training and validation data sets, respectively. Mortality among neonates with CDH needing ECMO can be reliably predicted with validated clinical variables identified in this study. ECMO-specific mortality prediction tools can allow risk stratification to be used in research and quality improvement efforts, as well as with caution for individual case management.

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.

Extracorporeal Membrane Oxygenation for the Treatment of Neonatal Respiratory Failure

This review discusses the use of extracorporeal membrane oxygenation (ECMO) for the treatment of respiratory failure in neonates. After briefly reviewing the early history of neonatal ECMO, the authors describe the respiratory diagnoses most often treated with ECMO and the manner in which affected neonates are deemed to have “failed” conventional therapies and thus require ECMO. After reviewing the most common indications for ECMO, factors that influence the timing of conversion to extracorporeal life support, as well as criteria that may exclude patients from receiving ECMO therapy, are described. At the conclusion of this article, the authors discuss the long-term outcomes of neonates whose respiratory disease was treated with ECMO and the costs associated with that care.

Respiratory failure and extracorporeal membrane oxygenation

Conventional treatment of respiratory failure involves positive pressure ventilation with high concentrations of inspired oxygen. If adequate gas exchange still cannot be achieved extracorporeal membrane oxygenation (ECMO) may be an option. The general indication for ECMO for respiratory insufficiency is a reversible pulmonary disease, which cannot be managed by conventional means. ECMO is a modified heart-lung machine. Blood is withdrawn from a central vein in the patient and pumped through an artificial oxygenator back to the patient, either to a central artery (veno-arterial ECMO) or to a central vein (veno-venous ECMO). Total gas exchange can be achieved through the extracorporeal system, and the lungs do not have to be subjected to high-pressure ventilation. To date over 21,500 neonates have been treated with ECMO with an overall survival to hospital discharge of 76%. Meconium aspiration syndrome carries the highest survival (94%), whereas congenital diaphragmatic hernia on ECMO only has a survival of 52%. A total of 3500 pediatric patients (30 days to 18 years) have been treated with ECMO with a survival of 56%. Aspiration and viral pneumonia are the pediatric diagnoses with the highest survival rates. Randomized controlled studies have shown a significant advantage of ECMO with regard to survival in neonates. In the pediatric age group, nonrandomized studies have shown lower mortality in ECMO-treated patients.

Update on extracorporeal membrane oxygenation

Extracorporeal membrane oxygenation (ECMO) consists of the application of intermediate-term cardiopulmonary bypass for the treatment of potentially reversible heart and/or lung failure in the neonate, child, and adult. Applications in the neonate include congenital diaphragmatic hernia, pulmonary hypertension, meconium aspiration syndrome, and pre- and post-operative congenital heart surgery support. In the older child, myocarditis, infections, and respiratory failure (RSV and ARDS) are the most frequent indications, in addition to peri-operative cardiac surgical support. A review of the institutional experiences at the University of Louisville spanning a 15-year period and comparison international data will be presented, along with a pertinent review of the literature. Technical considerations, complications, and long-term outcomes will be reviewed, and the potential interface between ECMO and other, less invasive technologies, i.e., high-frequency ventilation, replacement surfactant, and nitric oxide, will be discussed.

Nitric oxide further attenuates pulmonary hypertension in magnesium-treated piglets

BACKGROUND

Persistent pulmonary hypertension of the newborn (PPHN) commonly appears as a complication of several pulmonary and non-pulmonary diseases. The hypoxia possibly inhibits Ca2+ +/- dependent K+ channels, thus resulting in membrane depolarization of pulmonary smooth muscle cells, which leads to the opening of Ca2+ channels and Ca2+ entry, resulting in contraction of the vascular smooth muscle. However, magnesium (Mg2+) is an antagonist of Ca2+. We studied the effect of magnesium sulfate on the treatment of hypoxia-induced pulmonary hypertension and compared to the site of action of nitric oxide (NO).

METHODS

Zero-day-old piglets were used in each experiment. The effects of Mg2+ were tested in each hypoxic, normoxic and hyperoxic states. Once the desired physical state was achieved, Mg2+ was administered at a dose of 100 mg/kg approximately every 10 min. In order to determine the exact mechanism of the Mg2+, Nw-nitro-l-arginine (LNNA), a NO synthase-inhibitor, was administered simultaneously with Mg2+ in some of the experiments.

RESULTS

There was a significant correlation between the percent reduction of the pulmonary arterial pressure (PAP) caused by magnesium and the level of oxygen (O2) present in the pulmonary artery. The greatest amount of reduction was seen in the hypoxic condition where the least amount of O2 is found. A further reduction in the PAP was seen when NO was given at the end of the Mg2+ trials. There was no significant reduction seen in the systemic arterial pressure.

CONCLUSIONS

Inhaled NO further reduced the PAP in piglets already treated with Mg2+.

Three-week neonatal hypoxia reduces blood CGRP and causes persistent pulmonary hypertension in rats

To increase understanding of persistent pulmonary hypertension, we examined chronic pulmonary effects of hypoxia at birth and their relationships with immunoreactive levels of the potent vasodilator, calcitonin gene-related peptide (CGRP). Rats were born in 10% hypobaric hypoxia, where they remained for 1-2 days, or in 15% hypoxia, where they remained for 21 days. All were then reared in normoxia for 3 mo followed by reexposure to 10% hypoxia for 7 days (H-->H) or continued normoxia (H-->N); age-matched normoxic rats were hypoxic for the last 7 days (N-->H) or normoxic throughout (N-->N). Results are as follows. Pulmonary arterial pressure (P(PA)) in 10% H-->N rats was normal at the end of the experiment (13 wk), but in rats reexposed to hypoxia (H-->H), pressure rose to 19% above N-->H controls. In 15% H-->N rats, P(PA) remained high, similar to that of N-->H rats, and increased further by 40% on reexposure (H-->H). Medial thickness of small pulmonary arteries in 10% H-->H rats also increased by 40% over N-->H controls and was equally high in 15% H-->N and H-->H rats. In N-->H rats from both experiments, right ventricular hypertrophy index (RVH) was increased after hypoxia at 15-16 wk. Also, in the 15% study, RVH remained elevated in H-->N rats and increased in H-->H rats by 19% above N-->H controls. Blood CGRP was reduced by neonate and adult hypoxia, and hypoxic reexposure (H-->H) further lowered blood CGRP in the 15% but not 10% study. Declining left ventricular blood CGRP correlated highly with logarithmically increasing P(PA) in the 15% study (r = -0.81, P = 0.000). In conclusion, 1) short perinatal exposure to 10% O(2) exacerbated pulmonary hypertension with hypoxia later in life, 2) 15% O(2) at birth and for 21 days caused persistent pulmonary hypertension and exacerbation with reexposure, and 3) P(PA) correlated highly with declining blood CGRP levels in the 15% study.

Is prognostication in congenital diaphragmatic hernia possible without sophisticated investigations?

Congenital diaphragmatic hernia is a complex disorder, in which the anatomical defect is only one part of the spectrum of disease. Hypoplasia of lung complicated by pulmonary hypertension and right to left shunting results in serious hypoxemia. Many factors, based on degree of alterations in respiratory physiology and involving analysis of blood gases and acid base systems, have been used in an attempt to prognosticate the outcome. Majority of these investigations are not available in a modest set up like ours. The case records of all 20 patients admitted and operated for congenital diaphragmatic hernia in pediatric surgery unit of Government Medical College Hospital, Jabalpur from 1978 to 1997 were reviewed retrospectively in an attempt to prognosticate without the sophisticated investigations. It was found that even in a very modestly equipped hospital it is possible to prognosticate--to some extent--the outcome in these cases. Major prognosticators found were APGAR score (if child born in hospital), late age of presentation, location of stomach and identification of hernial sac.

New ways to ventilate newborns in acute respiratory failure

Out treatment options for acute neonatal failure have expanded greatly in the last 20 to 30 years. This article reviews patient-triggered ventilation, high frequency ventilation, negative extrathoracic pressure ventilation, nitric oxide therapy, liquid ventilation, extracorporeal membrane oxygenation, and advances in pulmonary function monitoring. The authors present background theories, describe equipment, review clinical strategies, and the results of recent trials.

Does extracorporeal membrane oxygenation benefit neonates with congenital diaphragmatic hernia? Application of a predictive equation

The overall survival of neonates with congenital diaphragmatic hernia (CDH) remains poor despite the advent of extracorporeal membrane oxygenation (ECMO). Attempts at accurately predicting survival have been largely unsuccessful. The purpose of this study was twofold: (1) to identify independent predictors of survival from a cohort of CDH neonates treated at the authors' institution when ECMO was not available and combine them to form a predictive equation, and (2) to apply the equation prospectively in a cohort of CDH neonates, treated at the same institution when ECMO was available, to determine whether ECMO improves outcome. From the clinical data of 62 CDH neonates treated at the authors' center by the same team of university neonatologists and pediatric surgeons between 1983 and 1993 (before ECMO availability), 15 preoperative and seven operative variables were selected as potential independent predictors. When subjected to multivariate, stepwise logistic regression analysis, four variables were identified as statistically significant (P < .05), independent predictors of survival: (1) ventilatory index (VI), (2) best preoperative PaCO2, (3) birth weight (BW), and (4) Apgar score at 5 minutes. When combined via logistic regression analysis, the following predictive equation was formulated: P (probability of survival to discharge) = [1 + e(x)]-1 where x = 4.9 - 0.68 (Apgar) - 0.0032 (BW) + 0.0063 (VI) + 0.063 (PaCO2). Applying a standard cut-off rate of survival at less than 20%, the equation yielded a sensitivity of 94% and a specificity of 82% in identifying the correct outcome of patients treated with conventional ventilatory management. The overall survival rate was 66%. Since the availability of ECMO at the center, 32 CDH neonates were treated using the same conventional ventilatory treatment and surgical repair by the same university staff. The overall survival rate was 69%. The predictive equation was applied prospectively to all neonates to determine predicted outcome, but was not used to decide the treatment method. Eighteen neonates received conventional therapy alone; 16 of 18 survived (89%). Fifteen of the 16 patients who survived had their outcomes predicted correctly (94%). Fourteen neonates did not respond to conventional therapy and required ECMO; 6 of 14 survived (43%). Six of the eight patients predicted to survive, lived (75%). All six patients predicted to die, died despite the addition of ECMO therapy (100%). The mean hospital cost, per ECMO patient who died, was $277,264.75 +/- $59,500.71 (SE). An odds ratio analysis, using the four independent predictors to standardize for degree of illness, was performed to assess the risk associated with adding ECMO therapy. The result was 1.25 (P = 0.75). Although the cohort was not large enough to eliminate significant beta error, the data strongly suggested no advantage of ECMO. At this center, absolute survival rates for neonates with CDH have not been significantly altered since ECMO has become available (66% v 69%). The authors conclude that the predictive equation remains an accurate measurement of survival at their center even when ECMO is used as a salvage therapy. The method of creating a predictive equation may be applied at any institution to determine the potential outcome of CDH neonates and assess the effect of ECMO, or other salvage therapies, on survival rates.

Prediction of mortality in neonates with congenital diaphragmatic hernia treated with extracorporeal membrane oxygenation

OBJECTIVE

To determine if data collected by the Extracorporeal Life Support Organization Registry could be used to identify neonates with congenital diaphragmatic hernia who had a > 90% mortality rate, despite the use of extracorporeal membrane oxygenation (ECMO) support.

DESIGN

We retrospectively reviewed data reported to the Extracorporeal Life Support Organization Registry on neonates with congenital diaphragmatic hernia.

PATIENTS

Data regarding 1,089 neonates with congenital diaphragmatic hernia reported to the Extracorporeal Life Support Organization Registry between 1980 and 1992 formed the basis of this study. All of the neonates studied had been treated with ECMO. This patient population includes neonates with right- and left-sided diaphragmatic hernia. This registry does not include neonates with congenital diaphragmatic hernia who were not treated with ECMO.

MEASUREMENTS AND MAIN RESULTS

Of 1,089 neonates with congenital diaphragmatic hernia, 679 (62%) survived. There were no differences between the two groups in gender or in the year they were treated. Survival rate did not significantly increase over the years between 1980 and 1992. When compared with survivors, nonsurvivors were more immature (38 +/- 2 vs. 39 +/- 2 wks; p = .01), had lower birth weights (3.0 +/- 0.5 vs. 3.21 +/- 0.53 kg; p = .001), were more often prenatally diagnosed (42% vs. 32%; p = .03), were cannulated at a younger age (31 +/- 54 vs. 40 +/- 50 hrs; p = .01), and had more severe respiratory compromise (higher peak pressures and PaCO2, lower PaO2 values). Multivariate analysis showed that arterial pH and PaO2 just before ECMO, and birth weight, had the highest discriminant coefficients. By using these variables in a discriminant function (D[fx] = 0.68 x pH + 0.62 x birth weight + 0.29 x PaO2; using standardized coefficients and variables), we could identify neonates who died with a sensitivity of 62%, a specificity of 63%, a positive-predictive value of 50%, and a negative-predictive value of 74%. No single variable or combination of variables yielded better results.

CONCLUSIONS

Although a number of factors identify neonates with diaphragmatic hernia as being at higher risk of dying despite ECMO support, data currently collected by the neonatal Extracorporeal Life Support Organization Registry do not allow clinicians to effectively discriminate nonsurvivors from survivors.

Magnesium sulphate as an alternative and safe treatment for severe persistent pulmonary hypertension of the newborn

Eleven newborns admitted consecutively to the neonatal unit with respiratory failure and severe persistent pulmonary hypertension (PPHN) were included in a clinical trial to assess the efficacy of magnesium sulphate (MgSO4) in the treatment of PPHN. A loading dose of 200 mg/kg MgSO4 was given over 20 minutes, followed by a continuous infusion of 20-150 mg/kg/hour to obtain a magnesium blood concentration between 3.5 and 5.5 mmol/l. Mean (SD) duration of treatment was 75.5 (19.8) hours. No other vasodilatory drug was administered before or during the treatment and patients were not hyperventilated. Mean (SEM) PaO2 values significantly increased from 42.6 (8.8) before treatment to 70.3 (24.1) mm Hg after 24 hours, with no change in pH or PCO2. Oxygen index and alveolar-arterial oxygen gradient (A-aDO2) were significantly lower after 24 hours; respectively, 46.8 (15.2) to 28.0 (9.0) and 624.3 (11.3) to 590 (58) mm Hg. Mean airway pressure could be significantly reduced from 19.5 (3.1) to 13.9 (3.9) cm H2O after 72 hours. Mean ventilatory time support was 131 hours and mean total oxygen dependency 10 days. No systemic hypotension nor any other adverse effect were noted. All infants survived and the neurodevelopmental assessment was normal at 6 and 12 months of age. It is concluded that magnesium sulphate is a non-aggressive and low-cost treatment of short duration which is easy to apply. It may have a role in the various treatment of PPHN.

The use of extracorporeal life support in pediatric burn patients with respiratory failure

Respiratory failure is the most common cause of death after thermal injury and may be caused by inhalation injury, acute respiratory distress syndrome (ARDS) or pneumonia. ARDS is usually associated with sepsis; however, it may also occur during burn shock, especially in patients that have a delayed or inadequate fluid resuscitation. During the past 24 months, five pediatric burn patients underwent extracorporeal life support (ECLS) for respiratory failure unresponsive to optimal medical management. The mean age of the patients was 26 months (range, 8.5 to 48 months), with a mean burn size of 46% TBSA (> 95% third degree). The etiology of the respiratory failure included severe bronchospasm in a 22-month-old former premature infant with bronchopulmonary dysplasia; three patients with ARDS; and one patient with a severe inhalation injury. All five patients required greater than 56 cm H2O peak pressures and 100% FIO2 at the time of beginning ECLS. The oxygenation index (OI) ranged from 45 to 180. Three (60%) of the patients survived. In the three patients who ultimately survived, significant improvements in pulmonary and hemodynamic parameters occurred within 96 hours of ECLS. The two patients who died showed no improvement and were removed from ECLS at 10 and 11 days; both expired within hours. The patients who expired developed significant hemodynamic instability, coagulopathy, and hemorrhage from their burn wounds. The extent and degree of burn injury did not seem to alter the outcome. Indications for considering ECLS in the pediatric burn patient are unmanageable, life threatening pulmonary insufficiency in patients that undergo a relative short course of pre-ECLS ventilator support.(ABSTRACT TRUNCATED AT 250 WORDS)

Complications of neonatal extracorporeal membrane oxygenation

From 1973-1985 to 1988 the average patient complications per case were 1.44 per case and significantly increased during 1990 to 1992 to 2.10 per case (Figure 3). During the same periods patient survival significantly decreased from 84% (1973-1985 to 1988, n = 2463) to 80% (1990 to 1992, n = 4005) (Figure 4). The association between total complication rates and survival rate was examined by regression analysis (Table 5). The correlation of patient complication rate and total complication rate with survival is highly significant; however, causality cannot be established. When comparing different entry criteria (Table 2) for incidence of mechanical and patient complications, no significant differences are apparent. This is not surprising since each of the entry criteria were designed to identify the same patient population. When premature neonates (> 35 weeks) were placed on ECMO, 36% of them had intracranial haemorrhage (ICH) with 62% mortality while only 12% of the neonates < 35 weeks had ICH and a 49% mortality. Similar findings were noted with low birthweight neonates (< 2.2 kg), 28% had ICH with 64% mortality while only 12% of the neonates > 2.2 kg had ICH with a 50% mortality. Selection criteria remain problematic for a variety of reasons. They cannot be viewed as absolute because of variability between centres. What represents likely 80% mortality in one centre may not apply to another. Historical controls are misleading because changing respiratory therapy strategies make historical populations difficult to compare. Also, once an ECMO centre becomes established, a more challenging group of patients will be attracted than previously was the case. Further, a single entry criterion cannot be generalized for all entry diagnoses. Criteria for an 80% predicted mortality is probably not the same for MAS, CHN, PPHN, and sepsis. Subsequent patients registered in the Neonatal ECMO Registry of the Extracorporeal Life Support Organization will address these issues more thoroughly, as specific details of the pre-ECMO condition and therapeutic strategies are collected. This collective review should help to identify trends which require reassessment of technique or patient management.

Predictive capabilities of preoperative and postoperative pulmonary function tests in delayed repair of congenital diaphragmatic hernia

To improve the survival of newborns with congenital diaphragmatic hernia (CHD), preoperative stabilization with conventional ventilatory therapy and extracorporeal membrane oxygenation (ECMO) have been used. Measurements that quantify pulmonary function may allow an accurate assessment of lethal pulmonary hypoplasia and predict outcome. Pulmonary function tests (PFTs) were obtained in 20 infants preoperatively and postoperatively; these included measurements of compliance, dynamic compliance, and tidal volume. Overall survival was 75%. Six surviving infants were initially managed with ventilator therapy alone, followed by repair (group 1). The remaining 14 patients, who were moribund at presentation or whose initial ventilator therapy failed, were placed on ECMO and received repair during bypass; nine survived (group 2), and five died (group 3). Compliance, dynamic compliance, and tidal volume obtained at initial presentation and immediately preoperatively were significantly higher for group 1 as compared with groups 2 and 3. Infants whose initial compliance was greater than 0.25 mL/cm H2O/kg and initial tidal volume was greater than 3.5 mL/kg did not require ECMO. Ultimate improvement in compliance was noted in 5 of 6 patients in group 1, 8 of 8 patients in group 2, and 5 of 5 in group 3. This improvement followed an initial decline in compliance in 9 of 14 survivors, from 15% to 76%. All six patients in group 1 had tidal volumes of more than 4 mL/kg, as did 7 of 9 patients in group 2. Only one patient among the ECMO nonsurvivors (group 3) had a postoperative tidal volume of this magnitude. These data suggest that initial PFTs may predict which infants will require ECMO.(ABSTRACT TRUNCATED AT 250 WORDS)

ECMO for left ventricular assist in a newborn with critical aortic stenosis

Extracorporeal membrane oxygenation (ECMO) has been used in neonates for a variety of disease states including congenital diaphragmatic hernia, meconium aspiration syndrome, sepsis, and postoperative cardiac compromise. To our knowledge, ECMO has not been employed prior to cardiac catheterization in critical aortic stenosis (CAS). We report a neonatal case of CAS where ECMO was used early as a form of left ventricular assist to achieve adequate systemic perfusion and oxygenation and reduce myocardial ischemia. The patient was maintained on ECMO during subsequent attempts at cardiac catheterization, balloon valvuloplasty, and operative valvotomy.

Alveolar-arterial oxygen gradient in acute chest syndrome of sickle cell disease

In 44 episodes of acute chest syndrome of sickle cell disease occurring in 37 children, simple clinical severity score, duration of hospital stay, transfusion data, and alveolar-arterial oxygen gradient were analyzed as indicators of severity of disease. The alveolar-arterial oxygen gradient, measured during breathing of room air, proved, on multivariate analysis, to be the strongest predictor of both clinical severity and the need for blood transfusion.

Do we use the right entry criteria for extracorporeal membrane oxygenation in congenital diaphragmatic hernia?

In a retrospective review we analysed alveolar-arterial oxygen difference (AaDO2) as an entry criterion for extracorporeal membrane oxygenation (ECMO) in neonates with several forms of acute respiratory insufficiency. Although for meconium aspiration syndrome, respiratory distress syndrome, sepsis, and idiopathic pulmonary hypertension of the newborn we found values in accordance with the literature, patients with congenital diaphragmatic hernia (CDH) met 80% mortality criteria with significant lower AaDO2 values. Several patients died before ever reaching usual entry criteria for ECMO, because serious lung deterioration makes AaDO2 values unreliable. Awaiting classical ECMO entry criteria for patients with CDH may at least partially explain the lower survival rate for ECMO in CDH.

Treatment of severe persistent pulmonary hypertension of the newborn with magnesium sulphate

Eight of nine newborn infants with severe persistent pulmonary hypertension of the newborn (PPHN), and a predicted mortality of 100%, and one infant with a predicted mortality greater than 94% based on alveolar-arterial oxygen tension difference [A-a)DO2) were treated with magnesium sulphate (MgSO4) as a life saving therapy after they failed to improve with conventional treatment. Magnesium at high serum concentrations decreases pulmonary pressures and is a muscle relaxant and sedative. Diluted MgSO4.7H2O solution (200 mg/kg) was given intravenously over 20-30 minutes. No changes in the treatment were made after MgSO4. Mean serum magnesium concentration was maintained between 2.88 and 5.67 mmol/l by continuous intravenous infusion (six infants). Baseline arterial oxygen tension (PaO2) and haemoglobin oxygen saturation had mean (SD) values of 4.66 (1.8) kPa and 60.4 (29.7)% respectively, which started to increase one hour after MgSO4 infusion, and increased significantly at six hours to 12.04 (7.07) kPa and 91.8 (10.88)% respectively. Arterial carbon dioxide tension (PaCO2) decreased and pH increased significantly after one hour compared with the baseline value. PaO2 increases are probably secondary to a decrease in pulmonary vascular resistance and pressure, decrease in a right to left shunt, better ventilation:perfusion ratio, and PaCO2 decrease and pH rise. Seven infants survived (77.8%). These results demonstrate the beneficial effect of magnesium in the management of PPHN when other accepted treatment fails, is contraindicated, or not available.

Cardiac performance in ECMO candidates: echocardiographic predictors for ECMO

Twenty-one neonates with severe respiratory failure, who met criteria in this center for extracorporeal membrane oxygenation (ECMO), underwent echocardiographic examinations to assess the role of cardiac dysfunction in determining the need for ECMO. The echocardiographic indexes of function included peak aortic and pulmonary flow velocity, aortic and pulmonary acceleration, shortening fraction, velocity of circumferential fiber shortening, right ventricular output, and left ventricular output. Patients were offered a staged treatment protocol using high-frequency oscillatory ventilation (HFOV), followed by ECMO if failing HFOV rescue. Nine patients demonstrated progressive deterioration and required ECMO (group 1); 12 patients recovered without ECMO (group 2). There were no significant intergroup differences in AaDO2, age, weight, gestational age, inotropic support, mean airway pressure, systemic blood pressure, or arterial blood gas parameters. Group 1 had significantly lower pulmonary and aortic peak flow velocities, lower pulmonary acceleration, lower shortening fraction, and lower velocity of circumferential fiber shortening (P less than .05). We found that values for peak pulmonary velocity less than 0.70 m/s with pulmonary acceleration less than 14 m/s2 would predict the need for ECMO in 7 of 9 group 1 patients and recovery without ECMO in 11 of 12 group 2 patients (P less than .01, Fisher's Exact test). We conclude that on initial echocardiographic evaluation, cardiac performance was impaired in those patients who subsequently required ECMO compared with a group of patients with similar severity in gas exchange who recovered without ECMO. We speculate that echocardiographic assessment of cardiac performance in ECMO candidates may prove useful in prediction of the subsequent need for ECMO or expedient transfer to an ECMO center.

Timing of surgery in congenital diaphragmatic hernia. Low mortality after pre-operative stabilisation

Eighty-six consecutive patients with congenital diaphragmatic hernia presenting within 6 hours of birth to a regional neonatal surgical unit were reviewed. Patients were managed under a policy of delayed surgery which has evolved during the 6-year study period. Overall survival (to leave hospital) was 70.9%. There were only seven postoperative deaths (10.3% of operations). Analysis of the 25 deaths in the light of postmortem findings and published exclusion criteria indicates that the availability of extracorporeal membrane oxygenation would have made little difference to overall survival.

Comparison of six ECMO selection criteria and analysis of factors influencing their accuracy

This study compared six extracorporeal membrane oxygenation (ECMO) selection criteria in 42 neonates and analyzed factors influencing the accuracy of outcome predictions. The sensitivity of the criteria in identifying fatal cases varied from 0.44 to 0.94 and the specificity of predictions of survival ranged from 0.42 to 0.69. The criterion having the highest sensitivity had the lowest specificity and conversely the criterion with the lowest sensitivity had the highest specificity. Overall accuracy of the criteria, as measured by the total number of correct outcome predictions, differed little among the criteria (23/42 to 27/42 correct predictions). Three factors influenced predictive accuracy: 1) a primary diagnosis of congenital diaphragmatic hernia (CDH) was associated with a greater mortality (P less than 0.001) and a significantly higher positive predictive value (PPV) for all criteria (P = 0.0009-0.012) than that seen in patients with other primary diagnoses; 2) calculating the alveolar-arterial oxygen gradient using an assumed, rather than measured barometric pressure, or estimating oxygenation index using a calculated, rather than a measured, mean airway pressure, increased false positive mortality predictions in non-CDH patients; and 3) requiring a peak inspiratory pressure (PIP) of at least 50 cm H2O in the definition of maximal medical management, rather than a PIP of 20-49 cm H2O, significantly increased the PPV for three of four criteria examined (P = 0.02-0.04). Awareness of these factors may facilitate the identification of neonates who need ECMO to survive.

Congenital diaphragmatic hernia repair on ECMO

Congenital diaphragmatic hernia (CDH) with severe respiratory failure in the first few hours of life continues to be associated with significant mortality. Extracorporeal membrane oxygenation (ECMO) has been successfully used postoperatively to reverse the effects of severe pulmonary hypertension. Since 1984, ECMO has been required in 27 of the patients we treated with CDH. This report describes our experience with six very high-risk patients placed on ECMO prior to the operation who subsequently underwent repair of their diaphragmatic hernias while on ECMO. Two patients presented in extremis, unlikely to survive initial operative repair, and were placed on ECMO prior to the operation. All six patients had immediate respiratory distress after birth with mean Apgars of 2.3 and 3.7. The best pre-ECMO arterial blood gas (postductal) showed mean +/- SEM values of 6.97 +/- 0.1; PO2 = 54.8 +/- 5.9; PCO2 = 79.5 +/- 16.9. Immediately prior to ECMO, the mean +/- SEM ventilatory index (VI = rate x mean airway pressure) was 1,233 +/- 44, with a mean pH of 7.17 +/- 0.05; PO2 = 32 +/- 2.9; PCO2 = 59 +/- 5.3 and a mean AaDO2 of 622 +/- 4.8. The timing of the operative repair averaged 25 hours following initiation of ECMO. Three right-sided and three left-sided hernias were treated. Four were repaired through an abdominal approach, and two via thoracotomy; four required a Gortex patch closure. Postoperative bleeding was not a major problem in these heparinized patients. Four of these six patients survived, and follow-up of 2 months to 3 years shows no significant respiratory compromise.(ABSTRACT TRUNCATED AT 250 WORDS)

The significance of ductal shunting during extracorporeal membrane oxygenation

The purpose of this study was to evaluate the significance and direction of shunts at the level of the foramen ovale or ductus arteriosus in full-term newborns with neonatal respiratory failure who were placed on extracorporeal membrane oxygenation (ECMO). A decrease in left ventricular dimension was expected when infants were placed on ECMO but did not occur. A left-to-right shunt was demonstrated at the ductal level in nine of 12 infants early in the course of ECMO before pulmonary resistance decreased. Presumably, the lack of change in the left ventricular dimension when infants were placed on bypass was due to a left-to-right shunt at the ductal level with ductal flow replacing the right heart output, being drawn into the bypass circuit.

Color flow mapping to document normal pulmonary venous return in neonates with persistent pulmonary hypertension being considered for extracorporeal membrane oxygenation

This study investigated the value of color flow mapping in documenting normal pulmonary venous return in neonates with persistent pulmonary hypertension who were candidates for extracorporeal membrane oxygenation (ECMO). Forty newborn infants with persistent pulmonary hypertension underwent conventional (two-dimensional and Doppler) echocardiography and color flow mapping. Of 25 candidates for ECMO therapy, 18 subsequently received it. Conventional echocardiography demonstrated normal pulmonary venous return in only 21 of the 40 patients. In all 40, however, color flow mapping demonstrated normal right and left pulmonary venous drainage entering the left atrium. In three other patients with total anomalous pulmonary venous return, conventional echocardiography demonstrated the anomalous pulmonary venous pathways, and color flow mapping did not show jets emanating from the left atrial wall; the left atrium was shown to fill exclusively from right to left shunting through the foramen ovale. We conclude that color flow mapping is superior to conventional echocardiography for verifying normal pulmonary venous return in neonates with persistent pulmonary hypertension.

Right common carotid artery ligation in extracorporeal membrane oxygenation

The effect of right common carotid artery ligation required for arteriovenous extracorporeal membrane oxygenation (ECMO) was investigated in 35 infants. Their neonatal course was reviewed for evidence of right-sided ischemia of the brain, as suggested by the presence of focal seizures, hemiparesis, focal abnormalities on electroencephalography, or infarct or hemorrhage demonstrable on neuroimaging studies. A significant incidence of left focal seizures (9/35) versus right focal seizures (2/35) was noted, suggesting an effect of the carotid ligation on right hemisphere function. Computed tomographic scans (20/35 infants), electroencephalograms (18/35), ultrasound scans (31/35), and neurologic examinations did not reveal an increased incidence of right hemisphere abnormalities. These data suggest that systematic evaluation of the effects of right common carotid ligation should proceed as discussion continues on expanding the use of ECMO.

Selective use of extracorporeal membrane oxygenation in the management of congenital diaphragmatic hernia

Extracorporeal membrane oxygenation (ECMO) provides lung rest for moribund infants with congenital diaphragmatic hernia (CDH) after deterioration from a "honeymoon" period. This suggests that unstable pulmonary hypertension determines demise more than pulmonary hypoplasia. We avoided treating overwhelming pulmonary hypoplasia by using ECMO only if the premoribund condition had been marked by evidence of adequate lung parenchyma as a best preductal PO2 greater than 100 torr and PCO2 less than 50 torr with maximal therapy. Twenty-six CDH infants with respiratory distress within 4 hours survived operation. Five were not ECMO candidates, with best PO2 33 +/- 9, PCO2 157 +/- 30 torr, and died. Seven honeymoon infants, with best PO2 325 +/- 80, PCO2 27 +/- 5, survived without ECMO. Fourteen additional infants had honeymoon 26 +/- 13 hours with PO2 256 +/- 48, PCO2 30 +/- 8 followed by a-AdO2 gradients 600 torr x 16 +/- 4.5 hours despite maximal therapy. All 14 were treated with ECMO for 48 to 210 hours. Arterial blood gas values at initiation were PO2 34 +/- 6, PCO2 59 +/- 19, and pH 7.22 +/- 0.2. Right-to-left shunting due to pulmonary hypertension was documented by oximetry and two-dimensional echo/Doppler examination. Twelve of 14 (86%) ECMO-treated infants survived with normal arterial blood gas values on room air, no right-to-left shunting, and no gross neurologic sequellae to date. Two of 14 died. Improvement on ECMO was marked by positive hyperoxia response and decreased right-to-left shunting.(ABSTRACT TRUNCATED AT 250 WORDS)

Predicting survival in infants with persistent pulmonary hypertension of the newborn

Since persistent pulmonary hypertension of the newborn (PPHN) often occurs as a life-threatening illness, it would be advantageous to identify the highest-risk infants within the first 24 hours of life so that transfer to centers with extracorporeal membrane oxygenation (ECMO) or high-frequency ventilation can be facilitated. Fifty-three infants with PPHN were evaluated retrospectively. A multivariate discriminant analysis of risk factors determined that lowest pH, critical PaCO2, highest inspiratory pressure (PI), maximum ventilator rate, and 5-minute Apgar score were significantly different between the 35 survivors (66%) and the 18 infants (34%) who had died when examined within the first 24 hours of life. A clinical scoring system was designed based on these five criteria, which predicted outcome accurately in 93% of infants. A logistic regression analysis was performed as a check on these results and found that lowest pH, critical PaCO2, and PI predicted outcome with great accuracy. These results suggest that the use of these scoring systems within the first 24 hours of age may help predict outcome in infants with PPHN.

Mortality with extracorporeal membrane oxygenation following repair of congenital diaphragmatic hernia in 93 infants

The results of extracorporeal membrane oxygenation (ECMO) following repair of congenital diaphragmatic hernia (CDH) are analyzed for 93 neonates reported to the Neonatal ECMO Registry. Each infant was symptomatic at birth and developed life-threatening hypoxemia after herniorrhaphy. ECMO was used after neonates met criteria predictive of death in individual centers. These included (1) failure of medical therapy to reverse hypoxemia (35 neonates); (2) acute clinical deterioration making death appear likely (37 neonates); (3) AaDO2 greater than 600 for 8 hours (13 neonates); (4) oxygen index score of 51 for 4.8 hours (5 neonates); and (5) cardiac arrest (1 neonate). With ECMO, 52 infants (58%) survived and were discharged. Pre-ECMO arterial blood gas analysis was not predictive of outcome. Mortality was higher in small premature infants. ECMO corrected the hypoxemia, which usually causes death following congenital diaphragmatic herniorrhaphy. Unfortunately, 47 major bleeding complications occurred with 29 deaths. Therefore, improved survival may depend on new methods designed to prevent bleeding.

Extracorporeal membrane oxygenation following repair of congenital diaphragmatic hernias

From 1981 through 1986, 8 newborns with congenital diaphragmatic hernia required herniorrhaphy in the first 8 hours of life. Extracorporeal membrane oxygenation (ECMO) was employed in 7 after they met local criteria predictive of 95% mortality. These criteria were an alveolar-postductal arterial oxygen gradient greater than 600 mm Hg for 12 hours or hemodynamic instability. Four of these 7 patients had unremitting hypoxemia after herniorrhaphy (no "honeymoon" period), 3 of whom survived. One additional patient died, producing a mortality of 29%. ECMO used for 68 to 241 hours (mean, 163 hours) provided reliable oxygenation in all. Deaths resulted from disseminated intravascular coagulation and bleeding, and bleeding and pulmonary failure after ligation of a patent ductus arteriosus. Complications occurred in 6 patients and included bleeding (3), hernia recurrence (3), and air embolism (1). Follow-up ranging from 1 year to 6 years after discharge of the 5 survivors shows normal growth and development in 4. The reported mortality without ECMO following congenital diaphragmatic herniorrhaphy in the first 8 hours of life ranges between 60 and 80%. While bleeding may present problems, survival of newborns with refractory hypoxemia after diaphragmatic repair has improved with ECMO.

Extracorporeal membrane oxygenation for newborn respiratory failure

Jugular vein-carotid artery extracorporeal membrane oxygenation (ECMO) was utilized in 22 newborns (16 male and 6 female) 1 to 12 days old with respiratory failure due to meconium aspiration (12 patients), diaphragmatic hernia (4), persistent fetal circulation (3), hyaline membrane disease (2), and Rh incompatibility (1). Prior to ECMO, all patients had alveolar-arterial O2 pressure gradients greater than 580 mm Hg (predicted mortality greater than 90%), weighed more than 1,800 gm, had a gestation period of longer than 35 weeks, and had no cerebral hemorrhage. The duration of ECMO was 41 to 310 hours (mean, 134.5 hours). Nineteen (86%) of the 22 patients survived ECMO. Death was caused by lung disease (2) and cerebral hemorrhage (1). Four other patients died 6 to 40 days after ECMO of pulmonary hypoplasia (1), pneumonia (1), cerebral edema (1), and hepatorenal failure (1). Complications during ECMO were few and easily managed. Fifteen infants (68%) are alive 1 to 18 months after ECMO. Three have neurological deficit (2 severe, 1 mild). Bayley Developmental Examinations in 4 survivors now more than 12 months old are normal. Extracorporeal membrane oxygenation is an aggressive but effective technique of life support in newborns refractory to conventional respiratory management. Potential complications of ECMO mandate strict aseptic technique, constant monitoring, and multidisciplinary patient management.

Criteria for extracorporeal membrane oxygenation in a population of infants with persistent pulmonary hypertension of the newborn

Extracorporeal membrane oxygenation (ECMO) has been available since 1975 as a therapy of last resort to provide adequate oxygenation for term infants with acute lung disorders that do not respond to maximal medical therapy. Virtually all term infants with serious lung disease have persistent pulmonary hypertension of the newborn (PPHN) characterized by significant right-to-left shunting of blood and severe diffusion defects manifested as increased alveolar-arterial oxygen gradients (AaDO2). Criteria for initiation of ECMO therapy have been developed in several institutions but at the present time there are no universal criteria applicable to all infants with PPHN. We have attempted to establish entry criteria that may be used for different populations of infants with PPHN. Based on a retrospective review of 30 infants with PPHN in our institution, we have defined standards of maximal medical therapy. An alveolar-arterial oxygen difference (AaDO2) of greater than or equal to 610 for 8 hours has been shown to be associated with 79% mortality in this population. This AaDO2/time interval is established as a major criterion for institution of extracorporeal membrane oxygenation.

Extracorporeal membrane oxygenation for newborn respiratory failure

Respiratory failure is the leading cause of death in the newborn. Conventional therapy is very successful with 80% of infants weaned from ventilatory support. For neonates with severe respiratory failure, unresponsive to maximal medical therapy, extracorporeal membrane oxygenation (ECMO) offers an alternative means of management. Venoarterial bypass is achieved by cannulating the right atrium via the internal jugular vein and the aortic arch via the right common carotid artery. A 5-inch roller pump is used to circulate the blood through a 0.4 or 0.8 m2 silicone membrane lung. Management includes heparinization, intravenous alimentation, antibiotic coverage, and reduction of FiO2 and airway pressure. Thirty infants aged 12 to 186 hours were placed on ECMO. Each met strict criteria designed to predict greater than 90% mortality. Time on bypass ranged from 37 to 250 hours. Success, defined by weaning from ECMO and ventilatory support, was achieved in 23. Twenty-one remain alive; 18 have excellent outcome with normal growth and development although follow-up is short (1 to 19 mos). These results corroborate reports from the pioneers of the technique and further support the use of ECMO for neonates with respiratory failure unresponsive to conventional therapy.