You are in: eMedicine Specialties > Pediatrics: Cardiac Disease and Critical Care Medicine > Cardiothoracic Surgery Extracorporeal Membrane OxygenationArticle Last Updated: Jun 14, 2006AUTHOR AND EDITOR INFORMATIONSection 1 of 11
  Author: Edwin Rodriguez-Cruz, MD, Assistant Professor, Department of Pediatrics, San Juan Bautista Medical School and Medical Center; Consulting Interventional/Clinical Pediatric Cardiologist, Department of Prediatrics, Hospital El Maestro and San Juan Bautista Medical Center; Consulting Interventional/Clinical Pediatric Cardiologist, Department of Cardiology, Cardiovascular Center of Puerto Rico and the Caribbean and Veterans Affairs Hospital and Medical Center of Puerto Rico Edwin Rodriguez-Cruz is a member of the following medical societies: American College of Cardiology, American College of Physicians-American Society of Internal Medicine, American Heart Association, American Medical Association, American Society of Echocardiography, Puerto Rico Medical Association, Society of Cardiac Angiography and Interventions, and Society of Pediatric Echocardiography Coauthor(s): Henry Walters III, MD, Associate Professor of Surgery, Wayne State University School of Medicine; Chief, Department of Surgery, Division of Cardiovascular Surgery, Children's Hospital of Michigan; Sanjeev Aggarwal, MD, MBBS, Staff Physician, Department of Pediatrics, Children's Hospital of Michigan Editors: Daniel S Schwartz, MD, FACS, Clinical Assistant Professor of Cardiothoracic Surgery, New York University School of Medicine; Consulting Staff, Department of Surgery, Division of Thoracic Surgery, North Shore University Hospital/Long Island Jewish Medical Center; Mary L Windle, PharmD, Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy, Pharmacy Editor, eMedicine.com, Inc; Mary C Mancini, MD, PhD, Director of Cardiothoracic Transplantation, Professor, Department of Surgery, Louisiana State University Health Sciences Center; Daniel Rauch, MD, FAAP, Director, Pediatric Hospitalist Program, Associate Professor, Department of Pediatrics, New York University School of Medicine; Steven R Neish, MD, SM, Director of Pediatric Cardiology Fellowship Program, Department of Pediatrics, Baylor College of Medicine Author and Editor Disclosure Synonyms and related keywords: extracorporeal membrane oxygenation, ECMO, extracorporeal life support, ECLS, oxygenation support, venoarterial bypass, venovenous bypass, oxygenator INTRODUCTIONSection 2 of 11
  The term extracorporeal membrane oxygenation (ECMO) was initially used to describe long-term extracorporeal support that focused on the function of oxygenation. Subsequently, in some patients, the emphasis shifted to carbon dioxide removal and the term extracorporeal carbon dioxide removal was coined. Later, extracorporeal support began to be used as postoperative support in patients following cardiac surgery. Other variations of its capabilities have been tested and used over the last few years, making it an important tool in the armamentarium of life and organ support measures for clinicians. With all of these uses for extracorporeal circuitry, a new term, extracorporeal life support (ECLS), has come into vogue to describe this technology. The differences between ECMO and cardiopulmonary bypass are as follows:
HISTORY OF EXTRACORPOREAL MEMBRANE OXYGENATIONSection 3 of 11
In May 1953, Gibbon used artificial oxygenation and perfusion support for the first successful open heart operation. In 1954, Lillehei developed the cross-circulation technique by using slightly anesthetized adult volunteers as live cardiopulmonary bypass apparatuses during the repair of certain congenital cardiac disorders. In 1955, at the Mayo Clinic, Kirklin et al improved on Gibbon's device and successfully repaired an atrial septal defect. In 1965, Rashkind and coworkers were the first to use a bubble oxygenator as support in a neonate dying of respiratory failure. In 1969, Dorson and colleagues reported the use of a membrane oxygenator for cardiopulmonary bypass in infants. In 1970, Baffes et al reported the successful use of extracorporeal membrane oxygenation (ECMO) as support in infants with congenital heart defects who were undergoing cardiac surgery. In 1975, Bartlett et al were the first to successfully use ECMO in neonates with severe respiratory distress. MECHANICS OF EXTRACORPOREAL MEMBRANE OXYGENATIONSection 4 of 11
Extracorporeal membrane oxygenation apparatus The extracorporeal membrane oxygenation (ECMO) apparatus consists of a blood pump with raceway tubing, a venous reservoir, a membrane oxygenator, and a countercurrent heat exchanger (see Image 1). The blood pump is either a simple roller pump (most common) or a constrained vortex centrifugal pump. The roller pump causes less hemolysis and is used for neonatal ECMO. The venous reservoir is used with the roller pump for neonatal ECMO. The oxygenator is responsible for exchanging both oxygen and carbon dioxide, and it is central to the successful performance of prolonged ECMO. Three types of commercial artificial lungs are available: bubble, membrane, and hollow-fiber devices. The heat exchanger warms the blood using a countercurrent mechanism. Blood is exposed to warm water that circulates within metal tubing. Safety devices and monitors
EXTRACORPOREAL MEMBRANE OXYGENATION PROCEDURESection 5 of 11
The extracorporeal membrane oxygenation (ECMO) circuit is primed with the freshest blood available. The acid-base balance and blood gas of the primer are adjusted appropriately. Differences between venoarterial ECMO and venovenous ECMO are presented in the table below. The standard ECMO procedure used in most neonatal ICUs is venoarterial bypass. In this situation, a cannula is placed through the right jugular vein into the right atrium. Blood is drained to a venous reservoir located 3-4 feet below heart level. The blood is actively pumped by a roller pump through the oxygenator, where gas exchange occurs via countercurrent flow of blood and gas. Next, the blood is warmed to body temperature by the heat exchanger before returning to the patient through a cannula placed through the right carotid artery into the aortic arch. Systemic anticoagulation therapy with heparin is administered throughout the bypass circuit, with frequent monitoring of activated clotting time (ACT), which should be maintained at 180-240 seconds. In venovenous bypass, a double-lumen cannula is placed through the right jugular vein into the right atrium. Desaturated blood is withdrawn from the right atrium through the outer fenestrated venous catheter wall, and oxygenated blood is returned through the inner lumen of the catheter and is angled to direct blood across the tricuspid valve. Differences Between Venoarterial and Venovenous Extracorporeal Membrane Oxygenation
In certain patients with cardiac or respiratory failure who have recently undergone cardiac surgery, transthoracic cannulation of the right atrial appendage and the aortic arch can be used as an alternative to neck cannulation. Transthoracic cannulation allows left heart decompression by cannulation of the left atrium. This is useful in patients with primary left heart failure. INDICATIONS AND CONTRAINDICATIONSSection 6 of 11
Neonatal extracorporeal membrane oxygenationIndications Patients with the following two major neonatal diagnoses require the use of extracorporeal membrane oxygenation (ECMO):
Selection criteria
*Failure to meet these criteria is a relative contraindication for ECMO. Qualifying patient criteria for extracorporeal membrane oxygenation Qualifying criteria are applied only when the infant has reached maximal ventilatory support of 100% oxygen (fraction of inspired oxygen [FiO2] equals 1) with peak inspiratory pressures (PIP) often as high as 35 cm H2O.
Pediatric extracorporeal membrane oxygenationIndications
Unlike the situation in neonates, when ECMO is considered in a pediatric patient, no clear set of inclusion or exclusion criteria exists. Evaluation of a pediatric patient for ECMO support is largely based on an assessment of the patient's condition and the institutional experience with pediatric ECMO. MANAGEMENTSection 7 of 11
Pulmonary system Extracorporeal membrane oxygenation (ECMO) is used temporarily while awaiting pulmonary recovery. In the classic use of neonatal ECMO, the typical ventilator settings are FiO2 of 21-30%, PIP of 15-25 cm H2O, a positive end-expiratory pressure (PEEP) of 3-5 cm H2O, and intermittent mechanical ventilation (IMV) of 10-20 breaths per minute. In some centers, a high PEEP of 12-14 cm H20 has been used to avoid atelectasis; this has been found to shorten the bypass time in infants. Pulmonary hygiene is strict and requires frequent positional changes, endotracheal suctioning every 4 hours depending on secretions, and a daily chest radiograph. Cardiovascular system Systemic perfusion and intravascular volume should be maintained. Volume status can be assessed clinically by urine output and physical signs of perfusion and by measuring the central venous pressure and the mean arterial blood pressure. Native cardiac output can be enhanced with inotropic agents. An echocardiogram should be performed to exclude any major congenital heart anomaly that may require immediate intervention other than ECMO (eg, obstructed total anomalous pulmonary venous connection). Central nervous system Central nervous system complications are the most serious and are primarily related to the degree of hypoxia and acidosis. Avoiding paralytic agents and performing regular neurologic examinations are recommended. If feasible, a head ultrasound should be obtained before beginning ECMO in a neonate. Reevaluation with serial head ultrasounds may be needed on a daily basis, especially after any major event. In patients with seizures or suspected seizures, aggressive treatment is recommended (eg, phenobarbital). Renal system During the first 24-48 hours on ECMO, oliguria and acute tubular necrosis associated with capillary leak and intravascular volume depletion are common because ECMO triggers an acute inflammatorylike reaction. The diuretic phase, which usually begins within 48 hours, often is one of the earliest signs of recovery. If oliguria persists for 48-72 hours, diuretics are often required to reduce edema. When renal failure does not improve, hemofiltration or hemodialysis filters may be added to the circuit. Hematologic considerations To optimize oxygen delivery, the patient's hemoglobin should be maintained at 12-15 g/dL using packed red blood cells (pRBCs). As a result of platelet consumption during ECMO, platelet transfusions are required to maintain platelet counts above 100,000/mm3. ACT should be maintained at 180-240 seconds to avoid bleeding complications. Infection control Strict aseptic precautions are required. The presence of infection is monitored by obtaining cultures from the circuit at least once a week. Based on institutional experience, the protocol frequency may vary. Other appropriate cultures (eg, fungal and viral) should be sent as needed. Fluids, electrolytes, and nutrition Patients on ECMO require close monitoring of fluids and electrolytes. The high-energy requirements should be met using hyperalimentation techniques. The patient's weight increases in the first 1-3 days on ECMO because of fluid retention. Medications
COMPLICATIONSSection 8 of 11
Mechanical complications
Management of circuit failure Immediately clamp the venous line, open the bridge, and clamp the arterial line to remove the patient from the ECMO. Since the patient is ventilator dependent, immediately bag the patient with 100% oxygen (FiO2=1) or shift the patient back to pre-ECMO ventilator settings. Complications in patientsNeurologic complications
Hemorrhagic complications
Cardiac complications
Pulmonary complications
Renal complications
Gastrointestinal tract complications
Complications resulting from infection and sepsis The ECMO circuit represents a large intravascular foreign body; frequent manipulation increases the risk of sepsis. Metabolic complications
Drug serum concentrations
Differential diagnoses of acute cardiorespiratory decompensation in patients on extracorporeal membrane oxygenation
Weaning or trial period without extracorporeal membrane oxygenationIn patients with a principal pre-ECMO diagnosis of respiratory failure, a trial period without ECMO is scheduled if (1) the patient demonstrates adequate gas exchange and is on reasonable ventilatory settings, and (2) the patient tolerates a pump flow of 10-20 mL/kg/min with the minimum of 200 mL/min. MORTALITY, MORBIDITY, AND LEGAL ISSUESSection 9 of 11
MortalityMortality statistics of extracorporeal membrane oxygenation (ECMO)-treated patients have remained stable over the past decade. Predictors of death include the following:
MorbidityMedical morbidity
Psychosocial morbidity Increased frequency of social problems, academic difficulties at school age, and higher rates of attention deficit disorder are reported in children who received ECMO. The ECMO procedure is dramatic and highly invasive. Families can feel isolated if no other patients are on ECMO in the same institution. At age 1 year, the stress level of the mother of an infant previously on ECMO is the same as the stress level in the family of a preterm infant. By age 5 years, the family stress level is the same as that of the family of a healthy child in whom ECMO was not used. Legal aspects
MULTIMEDIASection 10 of 11
REFERENCESSection 11 of 11
Extracorporeal Membrane Oxygenation excerpt Article Last Updated: Jun 14, 2006 | |||||||||||||||||||||
