Lung compliance as a measure of lung function in newborns with respiratory failure requiring extracorporeal membrane oxygenation

Lung inflammation and pulmonary function in infants with meconium aspiration syndrome

OBJECTIVE

To evaluate the relationship between inflammation and pulmonary function, we quantified changes in inflammatory cellular profile, pro-inflammatory cytokines, and pulmonary function in intubated neonates with meconium aspiration syndrome (MAS).

METHODS

Sixteen term infants were studied. Tracheal aspirate fluids, obtained within the first 6, 24, 48, and 96 hr of life were used for measurements of: (1) cellular profile changes; (2) mRNA and protein levels for pro-inflammatory cytokines, IL-1beta, IL-6, IL-8, and TNF-alpha, using RT-PCR and ELISA. Using the same time points as above, we determined mean airway pressure, oxygenation index (OI), alveolar-arterial oxygen gradient, and arterial/alveolar oxygen ratio. Baseline tidal volume and pulmonary compliance were obtained.

RESULTS

Birth weight was 3,820 +/- 656 g, gestational age 39.8 +/- 1.4 weeks. Mean airway pressure and OI significantly decreased from the first 6-96 hr of age (P = 0.01, P = 0.027). Cell counts were elevated in the first 6 hr compared to 96 hr (17.4 x 10(6)/ml vs. 1.5 x 10(6)/ml, P < 0.05). Pro-inflammatory cytokines decreased from the first 6-96 hr: IL-1beta (187 vs. 37 pg/ml, P < 0.05); IL-6 (3,469 vs. 150 pg/ml, P < 0.05); IL-8 (16,230 vs. 6,334 pg/ml, P = 0.01).

CONCLUSIONS

MAS is associated with an inflammatory response characterized by the presence of elevated cell count and pro-inflammatory cytokines which significantly decreased by 96 hr of life. This decrease in lung inflammation has a positive correlation with corresponding decreases in mean airway pressure and oxygenation index, two parameters associated with improved pulmonary function.

ECMO for neonatal respiratory failure

Extracorporeal membrane oxygenation (ECMO) has been offered as a life-saving technology to newborns with respiratory and cardiac failure refractory to maximal medical therapy. ECMO has been used in treatment of neonates with a variety of cardio-respiratory problems, including meconium aspiration syndrome (MAS), persistent pulmonary hypertension of the neonate (PPHN), congenital diaphragmatic hernia (CDH), sepsis/pneumonia, respiratory distress syndrome (RDS), air leak syndrome, and cardiac anomalies. For this group of high-risk neonates with an anticipated mortality rate of 80% to 85%, ECMO has an overall survival rate of 84%, with recent data showing nearly 100% survival in many diagnostic groups. This article reviews the current selection criteria for ECMO and the clinical management of neonates on ECMO, and discusses the long-term outcome of neonates treated with ECMO.

Measurement of the ductal L-R shunt during extracorporeal membrane oxygenation in the lamb

OBJECTIVE

In neonates, initially a ductal shunt is often observed during veno-arterial extracorporeal membrane oxygenation (ECMO). Depending on the degree of pulmonary hypertension in these patients, the ductal shunt will be right to left (R-L), left to right (L-R), or bidirectional. A ductal L-R shunt will possibly lead to pulmonary hyperperfusion and interact with ECMO weaning. The aim of this study was to give more insight in this ductal L-R shunt during ECMO by quantification of this shunt in relation to cardiac output and ECMO flow.

METHODS

In 7 lambs, closure of the duct was prevented by infiltration of the ductal wall with 10% formaline. This patent duct could be closed using a vesselloop around the duct. Ultrasound flowprobes were installed around the pulmonary artery, ascending aorta, and around the ECMO circulation tube. Right and left ventricular output and ECMO flow were measured. Ductus flow was defined as ductal left to right shunt (Qduct L-R) = flow in ascending aorta (Qao) - flow in central pulmonary artery (Qpa) and Qduct R-L = Qpa = Qao.

RESULTS

In 6 of 7 lambs a ductal L-R shunt was observed with a mean shunt of 44% (range, 11 to 79) of left ventricular output (Qduct L-R/Qao). Comparison with ECMO flow (Qduct L-R/Qecmo) showed a mean shunt of 76% (range 15 to 230). When compared with the total systemic circulating volume (Qpa + flow in the ECMO circuit [Qecmo]), the mean ductal L-R shunt showed a percentage of 51% (range, 7% to 142%).

CONCLUSIONS

During ECMO, mostly a ductal L-R shunt is observed in this lamb model. This ductal shunt is hemodynamically important. The percentages of this shunt in comparison with left ventricular output, and total circulating volume will support the idea that a ductal L-R shunt during ECMO could be another deteriorating factor in the often critical circulation of the neonate on veno-arterial ECMO.

The influence of ductal left-to-right shunting during extracorporeal membrane oxygenation

BACKGROUND/PURPOSE

The aim of this study was to analyze whether a ductal left-to-right (L-R) shunt will prolong extracorporeal membrane oxygenation (ECMO) in neonates with severe pulmonary hypertension. This report discusses the onset and termination of a ductal L-R shunt and its potential influences on ECMO when pulmonary hypertension decreases during venoarterial bypass.

METHODS

Twenty-nine neonates were monitored during veno-arterial ECMO, using bedside echocardiography with 12-hour interval observations.

RESULTS

Up to 43% of the patients showed this type of shunt already after 12 hours on bypass. In total, this type of ductal shunt was found between 12 and 72 hours on ECMO in 62% of the patients. After 72 hours, the ductal L-R shunt no longer was detected. In 38% of the patients, no ductal L-R shunt was found during ECMO. Comparisons between these 2 patient groups showed a significantly longer ECMO duration in patients with ductal L-R shunt (P <.007). The mean prolongation time was 46 hours. Also, a significant decrease of left atrium to aorta ratio (P <.01) was observed during ECMO in the ductus group after closure of the duct, illustrating the decrease in volume load for the left heart and lungs.

CONCLUSIONS

Ductal L-R shunting is related with a substantial prolongation of the ECMO course (mean prolongation of almost 2 days). The authors suggest that on one side, the ductal L-R shunt will lead to pulmonary hypercirculation and on the other side, postductal stealing from the descending aortic circulation will lead to prerenal failure. Possibly because of interactions with pulmonary and renal function, a ductal L-R shunt will, among other factors, interfere with weaning from ECMO, resulting in a prolonged bypass time.

The current status of neonatal extracorporeal membrane oxygenation

Marked changes have occurred in the practice of neonatal extracorporeal membrane oxygenation (ECMO) since the first survivor in 1975. Coagulation management has been markedly refined, new catheters allow ECMO to be done either in a venoarterial or venovenous (VV) mode, depending on cardiac function in the infant. A new design of the VV catheter will allow this technique to be used in more infants in the future. New therapies for respiratory failure have changed the complexion of the population being treated with ECMO. The 34 to 36 week gestation infant with respiratory distress syndrome and/or pulmonary hypertension rarely needs ECMO therapy due to the effectiveness of surfactant and high frequency oscillation. Present day survival for infants treated with ECMO for many diagnostic categories ranges between 90% to 100%. The effects of new interventions must be evaluated with regard to their effect on morbidity when being considered prior to ECMO. Neuro-developmental outcome is encouraging, but does indicate that ECMO and the near-miss ECMO patients need to be followed closely into school age. The number of patients being treated per ECMO center has dropped significantly over the last 10 years from 18 to 9. This brings forward the question about regional needs for ECMO Centers and how to assure that centers have enough patients to maintain their clinical competencies. The challenge for the future is where to place ECMO as a therapy. Should it remain a rescue therapy? Or should there now be a trial comparing ECMO to conventional therapies, with morbidity and cost of care as the outcome variables?

Extracorporeal membrane oxygenation exposes infants to the plasticizer, di(2-ethylhexyl)phthalate

OBJECTIVES

To determine the exposure to, and evaluate the potential toxicity from, the plasticizer, di(2-ethylhexyl)phthalate (DEHP) during extracorporeal membrane oxygenation (ECMO) therapy.

DESIGN

Protocol 1 consisted of a prospective comparison of three ECMO circuit designs in vitro. Protocol 2 consisted of a prospective, comparative clinical study evaluating DEHP plasma concentrations in ECMO vs. non-ECMO patients with respiratory failure.

SETTING

Neonatal intensive care unit at The Children's National Medical Center, Washington, DC.

PATIENTS

In protocol 2, 28 consecutive term infants were referred for ECMO therapy. Eighteen infants required ECMO; ten control patients received conventional ventilation and improved without ECMO.

INTERVENTIONS

In protocol 1, three ECMO circuit designs were primed in vitro with normal saline, albumin, and human blood, which was maintained at 37 degrees C and recirculated at 400 mL/min for 48 hrs. Plasma samples were obtained at time 0, 1 hr, and every 6 hrs. In protocol 2, ventilatory and cardiovascular management of the patients in the study was conducted by the attending physician. Patients were placed on ECMO when they met the institutional criteria for ECMO therapy. Daily plasma concentrations for DEHP were collected until 3 days after decannulation from bypass in the ECMO group. Control patients were sampled daily until extubation. Evidence of cardiac, liver, or lung toxicity was evaluated by Chest Radiographic Scores, liver function studies, and echocardiograms obtained on day 1, day 3, and the day of decannulation in the ECMO group, or at the time of extubation in the control group. Sedation, blood product transfusions as indicated, antibiotics, and hyperalimentation were administered to all patients.

MEASUREMENTS AND MAIN RESULTS

All DEHP plasma concentrations were measured by gas chromatography. In protocol 1, three circuits were studied: circuit A (small surface area); circuit B (larger surface area); and circuit C (surface area of A but with heparin-bonded tubing in the circuit). DEHP leached from circuit A at 0.32 +/- 0.12 microgram/ mL/hr, compared with 0.57 +/- 0.14 microgram/mL/hr from circuit B (p < .05). This amount of DEHP extrapolates in the ECMO patient to a potential exposure of 20 to 70 times that exposure from other medical devices or procedures, such as transfusions, dialysis, or short-term cardiopulmonary bypass. Circuit C showed almost no leaching from the circuit; DEHP concentrations decreased at a rate of 0.2 +/- 0.04 microgram/mL/ hr. In protocol 2, DEHP was undetected in the control patients. DEHP concentrations in ECMO patients were greater in the early course of ECMO. However, most patients cleared this compound from the plasma before decannulation. In contrast to the in vitro results in protocol 1, the average highest concentration at any time on bypass was 8.3 +/- 5.7 micrograms/mL or 2 mg/kg.

CONCLUSIONS

DEHP leaches from ECMO circuits, with potential exposure concentrations related to the surface area of the tubing in the ECMO circuit. Heparin bonding of the tubing eliminates this risk. Although significant concentrations of DEHP leach from the nonheparin-bonded circuits over time, our in vivo studies showed that the DEHP plasma concentrations were less than the previously reported values and do not correlate with any observable short-term toxicity. This compound may be either efficiently metabolized by the newborn, or redistributed into various tissues. Although signs of toxicity were not found in this study, long-term complications from chronic exposure to DEHP have not been determined.

Entry criteria for extracorporeal membrane oxygenation In neonates with congenital diaphragmatic hernia treated with high-frequency oscillatory ventilation

Although respiratory management with high-frequency oscillatory ventilation (HFOV) has generally been used for neonates with congenital diaphragmatic hernia (CDH), entry criteria for extracorporeal membrane oxygenation (ECMO) based on data from patients who underwent HFOV have not yet been reported. To establish entry criteria for ECMO in such patients, we retrospectively studied 36 neonates with CDH treated by HFOV in our institutions between 1986 and 1994. From the admission records, preductal and postductal arterial blood gas data and HFOV ventilation conditions for 72 h after admission were extracted. Oxygenation index (01) and alveolar-arterial oxygen gradient (A-aD02) time interval combinations were calculated. Patients were divided into two groups: candidates for ECMO (n = 22) who underwent ECMO (n = 18) or died without ECMO (n = 4); and non-candidates (n = 14), who survived without ECMO. Blood gas data in patients placed on ECMO were comparable to those in patients who died without ECMO: mean pre- and postductal OI for 4 h > 30, postductal A-aD02 ≥620 mmHg for 4 h, postductal A-aD02 ≥580 mmHg for 8 h, and postductal A-aD02 ?550 mmHg for 12 h showed better sensitivity with a specificity of more than 90% compared to entry criteria that had previously been used in our institutions: a postductal OI >40 for 4 h and postductal A-aDO2 ≥610 mmHg for 8 h. In addition, a combination of preand postductal OI >30 for 4 h indicated a sensitivity of 95.5% and a specificity of 92.9%.

Measurement of lung volumes and pulmonary mechanics during weaning of newborn infants with intractable respiratory failure from extracorporeal membrane oxygenation

Newborn infants with intractable respiratory failure who require extracorporeal membrane oxygenation (ECMO) experience diffuse pulmonary atelectasis shortly after initiation of ECMO. Atelectasis is likely due to the primary lung injury and the reduction of applied inspiratory ventilator pressure when the respirator settings are changed to the "rest settings." These pathophysiologic changes result in a decrease in lung compliance and lung volumes. We hypothesized that improving lung functions observed during ECMO and indicated by an increase in lung volumes will predict successful weaning from ECMO. Sixteen infants (mean +/- SEM: gestational age, 40.3 +/- 0.3 weeks; birth weight, 3.5 +/- 0.1 kg) with meconium aspiration syndrome (n = 13), sepsis (n = 2), and persistent pulmonary hypertension (n = 1) were studied. We measured passive respiratory system mechanics and lung volumes initially during full ECMO support (115 +/- 18 h on ECMO, Study I), and then within 24 h prior to weaning from ECMO (Study II). Respiratory system compliance (Crs), respiratory system resistance (Rrs), functional residual capacity (FRC), and tidal volume (VT) were measured. Prior to Study I lung volumes were too small to be detected. Crs increased between Study I and Study II (0.41 +/- 0.05 to 0.63 +/- 0.05 mL/cmH2O/kg, P < 0.05), and VT increased between Study I and Study II (5.6 +/- 0.6 to 10.4 +/- 0.8 mL/kg, P = 0.0005). FRC increased from 3.6 +/- 1.0 to 7.9 +/- 0.9 mL/kg (P = 0.0001). There was no change in Rrs (88 +/- 8 to 89 +/- 6 cm H2O/L/s, P = 0.9). The combination of Crs > 0.5 mL/cmH2O/kg and FRC > 5 mL/kg was a better predictor (P = 0.0002) of readiness to wean from ECMO than either Crs (> 0.5 mL/cmH2O/kg, P = 0.057) or FRC (> 5 mL/kg, P = 0.007) alone. The combination of FRC and Crs had a sensitivity of 73.3% and specificity of 100% for successful decannulation. We conclude that repeated measurements of FRC and Crs can assess lung recovery and may assist in establishing criteria for successful weaning from ECMO.

Continued pulmonary recovery observed after discontinuing extracorporeal membrane oxygenation

Extracorporeal membrane oxygenation (ECMO) is a valuable therapy for the treatment of reversible lung disease in neonates. Associated with this treatment, however, are risks for complications that increase with the duration of therapy. We evaluated alveolar-arterial oxygen tension difference P(A-a)O2 pulmonary compliance (CL), and functional residual capacity (FRC) in 20 infants immediately after ECMO was discontinued, and again 24 hours thereafter. We measured CL by pneumotachography and esophageal manometry and FRC by helium dilution. Mean (+/- SEM) values for CL and FRC increased (CL from 0.28 +/- 0.02 to 0.35 +/- 0.03 mL/cmH2O)/kg and FRC from 18.6 +/- 1.4 to 22.2 +/- 1.1 mL/kg; P < 0.05), and P(A-a)O2 and the oxygenation index (OI) decreased (200 +/- 19 to 169 +/- 14 mm Hg and 6.9 +/- 0.44 to 5.4 +/- 0.5, respectively; P < 0.02), over the 24 hour period following ECMO. Nineteen of 20 infants experienced improvement in at least two of these parameters. Improvements were found to be greatest in the infant with the worst lung function immediately after discontinuing ECMO, and in the ten infants who had not received pancuronium bromide for inducing skeletal muscle paralysis, following decannulation from ECMO. These data indicate that improvement in lung function following ECMO will generally continue over the 24 hour period following the termination of cardiopulmonary bypass, and that borderline pulmonary status may not preclude discontinuation of bypass therapy.

Validation of esophageal pressure occlusion test after paralysis

Measurements of respiratory mechanics are frequently made in ventilated infants and children. Esophageal pressure measurements (Pes) using a balloon on a catheter have been used to partition the respiratory mechanics into lung and chest wall components. Appropriate positioning of this balloon is crucial to obtain accurate estimates of pleural pressure. Traditionally, in spontaneously breathing subjects the balloon position is assessed with an occlusion test. In ventilated subjects, it is not always possible to perform an occlusion test prior to paralysis, and even if such a test is performed it may be relevant under conditions of positive pressure ventilation. By occluding the airway opening and applying gentle pressure to the abdomen or rib cage, positive swings in pressure can be measured by both Pes and airway opening pressure (Pao). We compared traditional occlusion tests measured in 16 spontaneously breathing puppies to the positive pressure occlusion test performed after paralysis. In 2 pups we were unable to obtain a reasonable traditional occlusion test (> 15% difference between Pes and Pao) but we obtained 10 traditional occlusion tests in each of the remaining 14 pups (2.1-14 kg). In 11 of these animals delta Pes was within 10% of delta Pao. This compared well to positive pressure occlusion test using abdominal pressure performed after analysis, where delta Pes was within 10% of delta Pao in 10 animals. In 9 of these pups occlusion tests were also performed by applying pressure on the rib cage, where delta Pes was within 10% of delta Pao in 6 animals.(ABSTRACT TRUNCATED AT 250 WORDS)

Improved pulmonary outcome after exogenous surfactant therapy for respiratory failure in term infants requiring extracorporeal membrane oxygenation

A blinded, randomized, controlled study was designed to test whether multiple-dose surfactant therapy would improve pulmonary outcome in term infants with respiratory failure, resulting in a shortened period of extracorporeal membrane oxygenation (ECMO). Infants > or = 34 weeks of gestational age in severe respiratory failure and receiving ECMO were stratified by diagnosis and then randomly assigned to the treatment or the control group. Four doses of modified bovine lung surfactant extract (beractant) were administered to the surfactant group (n = 28), and an equal volume of air was administered to the control group (n = 28). Lung compliance was initially low in both groups; after treatment, values were higher with time in the surfactant group (F = 5.40, p = 0.026). The ECMO treatment period was significantly shorter in the surfactant group (mean +/- SD: 107 +/- 33 hours vs 139 +/- 54 hours for the control group; U = 232, p = 0.023). Tracheal aspirate concentrations of surfactant protein A were low in both groups, and then increased steadily to a higher level in the surfactant group (F = 2.58, p = 0.04). The overall incidence of complications after ECMO was decreased in the surfactant group (18% vs 46% for the control group; chi-square value = 5.004, p = 0.025). Radiographic scores, echocardiographic findings, incidence of intracranial or pulmonary hemorrhage and bronchopulmonary dysplasia, time to extubation, duration of oxygen therapy, and duration of hospitalization did not differ between the two groups. Beractant in this population improved pulmonary mechanics, increased surfactant protein A content in tracheal aspirate, decreased time on ECMO duration, and reduced disease complications.

Phospholipid and surfactant protein A concentrations in tracheal aspirates from infants requiring extracorporeal membrane oxygenation

To test the hypothesis that infants with severe respiratory failure and the need for extracorporeal membrane oxygenation (ECMO) are surfactant deficient, we measured the amount of surfactant phospholipids, disaturated phosphatidylcholine, surfactant protein A, and protein in tracheal aspirates from 22 infants, who received ECMO therapy for respiratory failure with meconium aspiration syndrome (n = 18) or pneumonia (n = 4). Tracheal suction material was obtained in a standardized way every 4 hours during the period of ECMO treatment and pooled for 24-hour periods. During ECMO, mean total phospholipid, disaturated phosphatidylcholine, and surfactant protein A values in tracheal aspirates increased and protein values decreased significantly, predominantly during the 72-hour period before infants were weaned from ECMO. Of the 22 infants, 14 had an increase in tracheal aspirate phospholipid values of more than 200% and were found to need a shorter period of ECMO support (p less than 0.005) and post-ECMO ventilatory support (p less than 0.025) than did the eight infants with stationary or only moderate increases in tracheal aspirate phospholipid values, three of whom had pneumonia. We conclude that infants with respiratory failure who require ECMO treatment often have surfactant deficiency. We speculate that surfactant treatment might decrease the need for or the duration of ECMO support.

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.

Serial measurement of pulmonary mechanics assists in weaning from extracorporeal membrane oxygenation in neonates with respiratory failure

Extracorporeal membrane oxygenation (ECMO) is a highly invasive therapy for intractable neonatal respiratory failure, and serious complications may occur with increasing duration of bypass. Weaning from bypass is empirical at present. Thus, there is a need to accurately predict when infants can be successfully decannulated. We hypothesized that pulmonary mechanics would reflect lung recovery and, therefore, predict successful weaning from ECMO. We measured pulmonary mechanics daily in 22 neonates, at gestational age of 37.8 +/- 0.6 weeks (SE) requiring ECMO for severe respiratory failure (oxygen index 66 +/- 6). Pulmonary resistance (Rpul), dynamic compliance (Cdyn), and tidal volume (VT) were measured. Rpul did not predict lung recovery. Cdyn within 24 hours of starting ECMO was 0.3 +/- 0.04 ml/cm H2O. Cdyn within 24 hours of weaning from ECMO was 1.2 +/- 0.09 ml/cm H2O (p less than 0.001). All 22 infants had Cdyn greater than 0.6 ml/cm H2O at the time of decannulation, but four infants (20 percent) with Cdyn less than 0.6 ml/cm H2O could not be weaned from ECMO within 20 hours (p less than 0.01). Thus, a minimum Cdyn of 0.6 ml/cm H2O is associated with successful weaning from ECMO. Cdyn of 0.8 ml/cm H2O provided better overall discrimination between those who could be successfully weaned from ECMO. We conclude that serial measurement of dynamic pulmonary compliance predicts successful weaning from ECMO.

Birthweight, early passive respiratory system mechanics, and ventilator requirements as predictors of outcome in premature infants with respiratory failure

Early respiratory mechanics have been reported to predict outcome in newborns with respiratory failure. However, it remains unknown whether measurements of pulmonary function add significantly to the predictive value of more readily available variables The present study was designed to answer this question. Passive respiratory system mechanics were measured by an airway occlusion technique in 104 ventilator-dependent premature infants between 6 and 48 hours of life and corrected for infant size. A ventilation index [FiO2 x mean airway pressure (MAP)] was calculated at the time of pulmonary function testing. Poor outcome was defined as death from respiratory failure or need for supplemental oxygen at 28 days. Stepwise logistic function regression examined whether ventilation index and respiratory mechanics added predictive power over and above birthweight. Five infants died, and 45 patients required supplemental oxygen at 28 days. Birthweight was a strong predictor and would have entered the logistic model first in any case. Ventilation index added significantly to the predictive model (P = 0.038). Respiratory system conductance (P = 0.15) and compliance (P = 0.93) entered on the third and last step, respectively. We conclude that in premature infants with respiratory failure, birthweight is a strong predictor of outcome. Early ventilator requirements but not respiratory system mechanics, add significantly to this predictive model.

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.

Pulmonary mechanics and outcome of neonates on ECMO

Deciding when to wean neonates from extracorporal membrane oxygenation (ECMO) can be difficult. The usefulness of simple measurements of pulmonary mechanics e.g., dynamic compliance (Cdyn) has been questioned. We investigated the pulmonary mechanics of eight neonates using the interrupter technique, which allows the partitioning of pulmonary mechanics into compartments representing the conducting airways and more peripheral phenomena (viscoelastic properties and "pendelluft"). Three neonates required ECMO for a congenital diaphragmatic hernia (CDH), two for hyaline membrane disease (HMO), two for meconium aspiration syndrome (MAS), and one for pneumonia. All neonates with MAS, HMD, and pneumonia were successfully weaned from ECMO when their Cdyn was 0.3 mL/cmH2O/kg or greater [mean 0.34 +/- 0.06 (SEM)]. All three neonates with CDH died and their highest Cdyn was 0.21, 0.19, and 0.09 mL/cmH2O/kg respectively (mean, 0.16 +/- 0.037). The airway resistance (Raw) and the slower component of pressure change after interruption (delta Pdiff), a measure of the more peripheral phenomena of the lung, were not significantly different in those neonates who survived and those who did not. The values for delta Pdiff in all patients were higher than those in healthy neonates. However, the Raw was not different. This suggests that the major disturbance in pulmonary mechanics was distal to the conducting airways. Those neonates who were successfully weaned from ECMO had a significantly higher Cdyn 24-48 hours prior to decannulation. Considering the lung as a two-compartment model offers no advantages when compared to the one-compartment model for the prediction of the outcome of a neonate on ECMO.

Extracorporeal membrane oxygenation therapy in neonates with septic shock

Neonatal septic shock has significant morbidity and mortality with current therapeutic measures. At Children's National Medical Center, from June 1984 to October 1986, 10 of 100 patients treated with venoarterial extracorporeal membrane oxygenation (ECMO) had a documented diagnosis of septic shock. All of these infants fulfilled criteria consistent with 80% mortality using conventional intensive medical management. However, the survival rate for the septic neonates in this study was 100%. Compared with other groups of infants treated with ECMO, these septic neonates required significantly more ventilatory support after ECMO and had a higher incidence of chronic lung disease (30% v 12%). The septic neonates were also at higher risk for intracranial hemorrhage than the other infants treated with ECMO (40% v 26%). The necessity for prolonged intubation after ECMO for patients with septic shock suggests that this condition may be associated with additional structural damage not seen with meconium aspiration syndrome or respiratory distress syndrome. Nevertheless, for neonatal patients with septic shock unresponsive to conventional medical management, ECMO must be considered a viable alternative treatment.

Surfactant protein A concentrations in tracheal aspirate fluid from infants requiring extracorporeal membrane oxygenation

To understand the lung abnormalities leading to respiratory failure in infants, we measured 35,000-dalton surfactant protein A concentrations in tracheal aspirate fluid collected daily from 25 infants receiving extracorporeal membrane oxygenation (ECMO). Surfactant protein A concentrations were standardized per milligrams of total protein present in the aspirate. Among the 23 survivors with complete data, the surfactant protein A concentration increased significantly with time (p less than 0.0001). Concurrent increases in lung compliance (p less than 0.0001) and radiographic scores (p less than 0.0001) were also observed. This increase in surfactant protein A content may reflect lung recovery from barotrauma and oxygen toxic effects or be a response to the primary pulmonary disease process. The two infants who did not survive extracorporeal membrane oxygenation failed to demonstrate these trends.

Compliance, alveolar-arterial oxygen difference, and oxygenation index changes in patients managed with extracorporeal membrane oxygenation

Eighteen patients with meconium aspiration syndrome who failed conventional management were treated with extracorporeal membrane oxygenation (ECMO) for reversible respiratory failure. Dynamic lung compliance measurements were made prior to, during, and after ECMO support. P(A-a)O2 and oxygenation index (OI) measurements were calculated prior to and after ECMO support. Lung compliance decreased significantly comparing before-ECMO to during-ECMO, and increased significantly comparing during- to after-ECMO, but not comparing before- to after-ECMO measurements. P(A-a)O2 and OI decreased significantly from before to after ECMO. The improvement in oxygenation allowing removal from ECMO does not appear to be related to improved pulmonary mechanics, but may rather be secondary to increased effective pulmonary capillary blood flow.

Doppler echocardiographic evaluation of cardiac performance in infants on prolonged extracorporeal membrane oxygenation

Cardiac performance was evaluated by Doppler echocardiography in 19 infants with persistent pulmonary hypertension before, during and after prolonged extracorporeal membrane oxygenation (ECMO). Systemic arterial pressure was normal before ECMO (67 +/- 12 mm Hg), increased during ECMO (78 +/- 13 mm Hg) and decreased to baseline after ECMO (p less than or equal to 0.01). Heart rate was normal before ECMO and did not change during or after ECMO. The left ventricular shortening fraction was normal before ECMO (37 +/- 11%), decreased after beginning ECMO (25 +/- 11%) and returned to baseline 72 hours after beginning ECMO (p less than or equal to 0.01). Pulmonary arterial and aortic blood flow velocities were normal before ECMO, decreased 30 to 50% during ECMO and increased to baseline 72 hours after beginning ECMO (p less than or equal to 0.01). Stroke volume had an identical trend (p less than or equal to 0.01). Left ventricular velocity of circumferential shortening--an index of contractility--decreased after beginning ECMO (p less than or equal to 0.05). Left ventricular systolic wall stress--an index of systemic afterload--increased after beginning ECMO (p less than or equal to 0.01). A patent ductus arteriosus was present in 13 of 19 infants before ECMO, 16 of 19 infants during ECMO and in none of 19 infants after ECMO. Pulmonary arterial systolic pressure was high before ECMO (72 +/- 25 mm Hg), began to decrease after 48 hours on ECMO (59 +/- 24 mm Hg) and was normal after ECMO (38 +/- 18 mm Hg), p less than or equal to 0.05.(ABSTRACT TRUNCATED AT 250 WORDS)

Gas exchange measurements in neonates treated with extracorporeal membrane oxygenation

Closed-circuit spirometry techniques were used to study gas exchange (oxygen and carbon dioxide transport) across the native lung and membrane lung in ten neonates treated with extracorporeal membrane oxygenation (ECMO). Initially there was negligible oxygen transport across the native lung (0.4 +/- 0.4 mL/kg/min). An increase in native lung oxygen transport (2.0 +/- 1.5 mL/kg/min) at low ventilator settings and high levels of extracorporeal support heralded recovery of the native lung and predicted weaning from ECMO. Measurement of oxygen consumption and carbon dioxide production permitted the energy expenditure to be calculated in these critically ill neonates. The metabolic rates varied widely in each neonate over time and among neonates. (mean 57 +/- 11 kcal/kg/d, range 38 to 80 kcal/kg/d). This emphasizes the need to determine energy expenditure in order to guide nutritional support.