Pediatric applications of extracorporeal membrane oxygenation

Extra-corporeal membrane oxygenation in paediatric acute respiratory distress syndrome: overrated or underutilized?

Extracorporeal membrane oxygenation (ECMO) is a modified form of cardiopulmonary bypass which may provide support for severe cardiorespiratory failure including paediatric acute respiratory distress syndrome (PARDS). While ECMO was initially demonstrated to successfully support neonates with severe respiratory failure, the use of ECMO has expanded rapidly to support both paediatric and adult respiratory failure. Extracorporeal Life Support Organization (ELSO) registry data shows that the use of ECMO for paediatric respiratory failure has expanded rapidly over the past decades with increasing use of venovenous ECMO. Despite the increasing complexity of children supported by ECMO for ARDS, outcomes have remained consistent with survival to hospital discharge greater than 50%. ECMO complications are still common and potentially devastating, especially neurological complications. There is grade 1 evidence to support the use of ECMO in both neonatal and adult respiratory failure but evidence in paediatric respiratory failure is confined to case series and case-control studies. While there are no published guidelines for use of ECMO in PARDS, in particular no clearly defined inclusion and exclusion criteria, current evidence suggests that children with severe ARDS may benefit from ECMO support, with survival to hospital discharge equivalent or better than conventional management in children with severe ARDS.

Extracorporeal membrane oxygenation for refractory cardiac arrest

Extracorporeal cardiopulmonary resuscitation (ECPR) is the use of rapid deployment venoarterial (VA) extracorporeal membrane oxygenation to support systemic circulation and vital organ perfusion in patients in refractory cardiac arrest not responding to conventional cardiopulmonary resuscitation (CPR). Although prospective controlled studies are lacking, observational studies suggest improved outcomes compared with conventional CPR when ECPR is instituted within 30–60 min following cardiac arrest. Adult and pediatric patients with witnessed in-hospital and out-of-hospital cardiac arrest and good quality CPR, failure of at least 15 min of conventional resuscitation, and a potentially reversible cause for arrest are candidates. Percutaneous cannulation where feasible is rapid and can be performed by nonsurgeons (emergency physicians, intensivists, cardiologists, and interventional radiologists). Modern extracorporeal systems are easy to prime and manage and are technically easy to manage with proper training and experience. ECPR can be deployed in the emergency department for out-of-hospital arrest or in various inpatient units for in-hospital arrest. ECPR should be considered for patients with refractory cardiac arrest in hospitals with an existing extracorporeal life support program, able to provide rapid deployment of support, and with resources to provide postresuscitation evaluation and management.

Extracorporeal membrane oxygenation for severe acute respiratory failure

Extracorporeal membrane oxygenation (ECMO) is a technique for providing life support, in case the natural lungs are failing and are not able to maintain a sufficient oxygenation of the body's organ systems. ECMO technique was an adaptation of conventional cardiopulmonary bypass techniques and introduced into treatment of severe acute respiratory distress syndrome (ARDS) in the 1970s. The initial reports of the use of ECMO in ARDS patients were quite enthusiastic, however, in the following years it became clear that ECMO was only of benefit in newborns with acute respiratory failure. In neonates treated with ECMO, survival rates of 80% could be achieved. In adult patients with ARDS, two large randomized controlled trials (RCTs) published in 1979 and 1994 failed to show an advantage of ECMO over conventional treatment; survival rates were only 10% and 33%, respectively, in the ECMO groups. Since then, ECMO technology as well as conventional treatment of adult ARDS have undergone further improvements. In conventional treatment lung-protective ventilation strategies were introduced and ECMO was made safer by applying heparin-coated equipment, membranes and tubings. Many ECMO centres now use these advanced ECMO technology and report survival rates in excess of 50% in uncontrolled data collections. The question, however, of whether the improved ECMO can really challenge the advanced conventional treatment of adult ARDS is unanswered and will need evaluation by a future RCT.

The impact of extracorporeal membrane oxygenation on survival in pediatric patients with acute respiratory failure. Pediatric Critical Care Study Group

OBJECTIVE

Extracorporeal membrane oxygenation (ECMO) has been used with increasing frequency in the treatment of acute respiratory failure in pediatric patients. Our objective in this study was to test the hypothesis that ECMO improves outcome in pediatric patients with acute respiratory failure.

DESIGN

Multicenter, retrospective cohort analysis.

SETTING

Forty one pediatric intensive care units participated in the study under the auspices of the Pediatric Critical Care Study Group.

PATIENTS

All pediatric patients admitted to the participating institutions with acute respiratory failure during 1991 were included. Patients with congenital heart disease, contraindications to ECMO, or incomplete data were excluded, yielding a data set of 331 patients from 32 hospitals.

INTERVENTIONS

Conventional mechanical ventilation, high-frequency ventilation, and extracorporeal membrane oxygenation.

MEASUREMENTS AND MAIN RESULTS

Multivariate logistic regression analysis was used to identify factors associated with survival. In a second analysis, pairs of ECMO and non-ECMO patients, matched by severity of disease and respiratory diagnosis, were compared. The use of ECMO (p = .0082), but not the use of high-frequency ventilation, was associated with a reduction in mortality. Other factors independently associated with mortality included oxygenation index (p < .0001), Pediatric Risk of Mortality score (PRISM) (p < .0001) and the Paco2 (p = .045). In 53 diagnosis- and risk-matched pairs, there was a significantly lower mortality rate (26.4% vs. 47.2%; p < .01) in the ECMO-treated patients. When all patients were stratified into mortality risk quartiles on the basis of oxygenation index and PRISM score, the proportion of deaths among ECMO-treated patients in the 50% to 75% mortality risk quartile was less than half the proportion in the non-ECMO treated patients (28.6% vs. 71.4% p < .05)> No effect was seen in the other quartiles.

CONCLUSIONS

The use of ECMO was associated with an improved survival in pediatric patients with respiratory failure. The lack of association of outcome with treatment in the ECMO-capable hospital or with another tertiary technology (i.e. high-frequency ventilation) suggests that ECMO itself was responsible for the improved outcome. Further studies of this procedure are warranted but require broad-based multi-institutional participation to provide sufficient statistical power and sensitivity to demonstrate efficacy.

Probability of survival after prolonged extracorporeal membrane oxygenation in pediatric patients with acute respiratory failure. Extracorporeal Life Support Organization

OBJECTIVE

Extracorporeal membrane oxygenation (ECMO) has been used with increasing frequency for respiratory failure that is unresponsive to conventional therapy. We examined the relationship between duration of ECMO and outcome to understand whether prolonged ECMO (duration of the procedure for > 14 days) was more commonly associated with futile therapy or eventual recovery.

DESIGN

A cohort study of all patients reported to the Pediatric ECMO Registry for Acute Respiratory Failure of the Extracorporeal Life Support Organization.

SETTING

Tertiary hospitals (n = 83) capable of providing extracorporeal support for pediatric patients.

PATIENTS

Children (n = 382) between the ages of 1 wk and 18 yrs of age with severe respiratory failure.

INTERVENTIONS

Extracorporeal membrane oxygenation.

MEASUREMENTS AND MAIN RESULTS

The death or live hospital discharge of ECMO-treated patients, together with the post-ECMO mechanical ventilation course, were examined as a function of duration of ECMO and of pre-ECMO respiratory status. The occurrence of complications and the causes of death were also noted. The criteria used to initiate ECMO, as well as the determination of the futility of further ECMO, were determined by local practice at individual centers. There were 382 patients treated with ECMO, of whom 184 (48%) survived. The proportional survival in the patients treated for the longest duration was similar to the overall group. The cause of death was given for 168 patients: 32 neurologic deaths; nine deaths due to ECMO complications; and 30 deaths due to nonpulmonary organ failure. There were 97 deaths due to elective ECMO termination; 80 of these deaths occurred after the determination of the futility of anticipating pulmonary recovery. The latter deaths occurred at widely varying durations of ECMO, with a median of 282 hrs. However, at that same duration, 47 eventual survivors (26% of all survivors) continued to receive ECMO. By discriminant analysis, the survival rate was independently related (r2 = .18; p < .0001) to peak ventilator inspiratory pressure before ECMO and duration of intubation before ECMO, patient age, and the occurrence of several complications.

CONCLUSIONS

While the survival rate in pediatric patients receiving ECMO appears related to the severity of lung disease and to the occurrence of ECMO complications, the survival rate in patients treated with ECMO courses of > 2 wks was similar to the survival rate of patients treated for shorter periods of time. ECMO was terminated in some patients for pulmonary futility at durations of ECMO associated with survival in substantial numbers of patients in whom ECMO was continued.

Prolonged extracorporeal support for nonneonatal respiratory failure

Extracorporeal membrane oxygenation (ECMO) is effective for newborns with pulmonary failure unresponsive to conventional therapy. However, ECMO for the older child and adult has been controversial and not widely utilized. Over 4 years, 24 patients (aged 4 months to 16 years; 11 boys, 13 girls) underwent venoarterial ECMO (duration, 7 to 19 days) for respiratory failure. The diagnoses were: viral pneumonia (7), hydrocarbon aspiration (6), sepsis with adult respiratory distress syndrome (ARDS) (2), bacterial pneumonitis (2), tracheal stenosis (1), bilateral pulmonary contusion (1), diaphragmatic hernia with ARDS (1), ketoacidosis with ARDS (1), pulmonary artery injection of hydrocarbon (1), drowning (1), and epiglottis with barotrauma (1). Pre-ECMO blood gas ranges (and means) were PO2 18 to 65 (46), and PCO2 47 to 112 (65). Nineteen patients received dopamine, dobutamine, or other inotrope for associated cardiac and/or renal failure. Cannulation for ECMO was through neck or groin vessels in 17, and sternotomy in 7. ECMO flow rates were 150 to 250 mL/kg/min, to maintain PO2 greater than 100 and PCO2 less than 40. Nine patients (41%) survived ECMO, with eight long-term survivors, (4 hydrocarbon aspiration or injection, 1 pulmonary contusion, 1 viral pneumonia, 1 ARDS, 1 barotrauma), three of whom have mild neurological deficit. All patients with sternotomy, and 8 of 15 with neck and/or groin cannulation, required 1 to 5 explorations for hemorrhage while on ECMO. All survivors had primarily pulmonary failure; patients with combinations of pulmonary, cardiac, and renal failure did not survive. ECMO can be life-saving in the child with isolated pulmonary failure, but its efficacy in patients with multiorgan failure is uncertain.

Effect of preoperative stabilization on respiratory system compliance and outcome in newborn infants with congenital diaphragmatic hernia

To determine whether preoperative stabilization and delay of operative repair of congenital diaphragmatic hernia (CDH) may decrease operative risk, we performed serial pulmonary function tests on 22 newborn infants with CDH and on four infants without pulmonary hypoplasia (two with ileal atresia and two with tracheoesophageal anomalies) who served as control subjects. We used 2 passive respiratory mechanics technique to measure respiratory system compliance. All patients with CDH had respiratory distress immediately after birth, and required mechanical ventilation. Thirteen babies underwent emergency repair (six survived, seven died); nine of them received extracorporeal membrane oxygenation (ECMO) after the operation (two survived, seven died). Operative repair was delayed deliberately for 2 to 11 days in nine infants with severe hypoxemia. Six immediately received ECMO for 4 to 10 days; one died of intraventricular hemorrhage, and five survived and later underwent surgical repair. The seventh patient did not receive ECMO but appeared to have respiratory distress syndrome of infancy and improved after administration of synthetic surfactant. Improvement was seen in two additional infants who received conventional assisted ventilation during a 48-hour delay before surgery, and survived. In all, eight of nine infants who underwent preoperative stabilization survived (p less than 0.05 compared with survival after emergency surgery). Following surgical repair immediately after birth, respiratory system compliance improved only slightly during the first week of life, a time when control infants had a rapid increase in respiratory system compliance (p less than 0.001). In contrast, respiratory system compliance increased nearly twofold in the nine patients undergoing preoperative stabilization (p less than 0.02). Preoperative ECMO was associated with an increase in respiratory system compliance of more than 60% for 1 week, a significant difference from respiratory system compliance among patients undergoing emergency CDH repair (p less than 0.05). These observations provide physiologic evidence of possible benefits of preoperative stabilization before repair of CDH.