- Email: [email protected]
Extracorporeal Membrane Oxygenation
Ex tracorp oreal Membra ne Ox ygenation Onsy Ayad, MDa,b, Ann Dietrich, MD, FAAP, FACEPb,c,*, Leslie Mihalov, MDb,c KEYWORDS ECMO Respiratory failure Circulatory failure
Extracorporeal membrane oxygenation (ECMO) is an advanced technology that is available at a limited number of facilities. It is a supportive modality that is used in acute severe reversible cardiac or respiratory failure in patients of all ages when there is a high risk for dying from the primary disease despite maximal conventional intensive care supportive measures (Fig. 1). ECMO has been used successfully since the 1970s for neonates with persistent pulmonary hypertension refractory to conventional therapy. Hypothermic cardiopulmonary arrest, failed traditional therapies for respiratory diseases, and protracted resuscitation have also been situations in which ECMO has been effective. Similar to cardiac bypass, ECMO is a means by which venous blood is removed from the patient, oxygenated and ventilated, and returned to the arterial or venous circulation of the patient (Fig. 2). ECMO is labor-intensive and expensive, however, with an estimated total hospital cost of $20,000 to $90,000 per patient, and it should be targeted to patients likely to benefit from the therapy. In 2006, the Extracorporeal Life Support Organization (ELSO) reported a survival rate to intensive care unit (ICU) discharge of 65% in a cohort of 32,905 patients. The current reported survival rates are 77% for neonatal respiratory failure, 56% for pediatric respiratory failure, 53% for adult respiratory failure, 43% for pediatric cardiac failure, and 32% for adult cardiac failure. Early initiation of this technology may be life saving for critically ill patients with specific respiratory or cardiac diseases. Early identification of patients who may benefit from this technology and timely transfer to facilities prepared to use this
a
Nationwide Children’s Hospital, 700 Children’s Drive, Columbus, OH, USA The Ohio State University College of Medicine, 370 West 9th Avenue, Columbus, OH 43210, USA c Section of Pediatric Emergency Medicine, Nationwide Children’s Hospital, 700 Children’s Drive, Columbus, OH, USA * Corresponding author. Section of Emergency Medicine, Nationwide Children’s Hospital, 700 Children’s Drive, Columbus, OH. E-mail address: [email protected] (A. Dietrich). b
Emerg Med Clin N Am 26 (2008) 953–959 doi:10.1016/j.emc.2008.07.010 0733-8627/08/$ – see front matter ª 2008 Elsevier Inc. All rights reserved.
emed.theclinics.com
954
Ayad et al
Fig. 1. ECMO system. (Courtesy of O. Ayad, MD, Columbus, OH).
technology if conventional therapies are not effective may improve outcomes for a select subset of patients. RESPIRATORY DISEASES
ECMO has been used for patients with primary acute hypoxic respiratory failure (AHRF) of various causes. Causes of AHRF include viral pneumonia (most common), bacterial pneumonia, aspiration, acute respiratory distress syndrome (ARDS), postoperative or posttraumatic ARDS, pulmonary hemorrhage, and burn injuries. Cochran and colleagues1 reviewed 10 years of experience with pediatric ECMO used for 27 children and adolescents with life-threatening pulmonary conditions unresponsive to conventional intensive care therapy. Most patients were male, and the mean age of the patients was 28 months. Venoarterial access was ultimately used in all but 1 patient. The most frequent diagnoses were presumed viral pneumonia, respiratory syncytial virus (RSV), bronchiolitis, and pertussis pneumonia. The overall survival rate was 67%. Although the number of patients in any category was limited, patients who had pertussis and documented bacterial pneumonia had higher mortality rates than patients with other diagnoses. The mean duration of ECMO was 12.2 days. Reasons for early termination included unrelenting pulmonary hypertension, multiple organ dysfunction, and intracerebral bleeding.
Extracorporeal Membrane Oxygenation
Fig. 2. Venoarterial ECMO circuit. (From Walker G, Liddell M, Davis C. Extracorporeal life support—state of the art. Paediatr Respir Rev 2003;4(2):147–52; with permission.)
Other studies have tried to predict which patients would not benefit from ECMO. An A-a gradient of greater than 450 mm Hg for more than 16 hours and a mean airway pressure of greater than 23 cm H2O were highly predictive of mortality.2,3 This differs from the results noted by Cochran and colleagues,1 who found a survival rate of 67% in a pediatric population with a mean A-a gradient of 580 mm Hg and a mean airway pressure of 29.9 cm H2O. It has been demonstrated that the earlier the referral, especially before significant barotrauma or volutrauma, the better is the outcome.1 ECMO survival also varies, depending on the etiology of the respiratory failure. Survival is highest in cases of aspiration pneumonia (65%) and lowest in Pneumocystis pneumonia (41%) and pertussis (30%). In one series, when all patients were stratified into mortality risk quartiles (based on oxygenation index and pediatric risk of mortality [PRISM] score), the proportion of deaths among ECMO-treated patients in the 50% to 75% mortality risk quartile was less than half of the proportion in non–ECMO-treated patients (28.6% vs. 71.4%; P < .05; Fig. 3).3 REFRACTORY CIRCULATORY FAILURE
Initially, the use of ECMO was contraindicated for patients who had septicemia because of concerns that contamination of the circuit would result in certain death. Several studies have not supported these concerns.4–6 The American College of Critical Care Medicine has published guidelines regarding the management of septic shock in children.7 The recommendation is to consider ECMO for children who are unresponsive to all conventional treatment. Septic shock frequently has a different hemodynamic manifestation in neonates, infants and children, and adults. In
955
Ayad et al
Actual Mortality
956
100 90 80 70 60 50 40 30 20 10 0
ECMO Non-ECMO
<25
25-50
50-75
>75
Predicted Mortality Fig. 3. ARDS: Pediatric ECMO. (From Green TP, Timmons OD, Fackler JC, et al. The impact of extracorporeal membrane oxygenation on survival in pediatric patients with acute respiratory failure. Crit Care Med 1996;24:323–9; with permission.)
neonates, most have persistent pulmonary hypertension. In infants and young children, decreased left ventricular function and low cardiac output are more common, and in adults, the pattern is usually distributive shock. ECMO may be particularly advantageous in children with impaired ventricular function. Studies used to establish these recommendations had fewer than 13 patients in each series, however.5,6 A more recent review of 45 children who received venoarterial ECMO for hemodynamic support has added more credibility to the recommendations, with a 47% survival rate to hospital discharge. The use of ECMO in children with septic shock and multiple organ failure is controversial, with some institutions not placing these patients on ECMO because of dismal survival rates. Potential indications for ECMO support in refractory circulatory failure include failure to wean from cardiopulmonary bypass, cardiopulmonary failure after surgical repair, severe ventricular failure (eg, in myocarditis and cardiomyopathy), severe hypoxemia in cyanotic congenital heart disease if surgery is temporarily contraindicated, a bridge for cardiac transplantation, and refractory septic shock. CARDIAC ARREST
The use of ECMO for patients who have cardiac arrest is increasing in frequency. The survival rate after pediatric cardiopulmonary arrest is dismal. Young and Seidel reported a 13% survival to hospital discharge.8 Out-of-hospital arrests had the worst survival rates at 8.4%, whereas in-ICU or in-hospital arrests had slightly better survival rates (20% and 24%, respectively). In a 5.5-year study examining factors predictive of survival to hospital discharge for pediatric ICU arrests, de Mos and colleagues9 found high in-hospital mortality and morbidity rates and that the use of postarrest ECMO within 24 hours was associated with reduced mortality; the overall survival rate increased to 25%. Factors associated with mortality included the presence of renal dysfunction and an epinephrine infusion at the time of the arrest. Alsoufi and colleagues10 reported on pediatric patients who had refractory cardiac arrest (N 5 80, age range: 1 day to 17.6 years). Most patients had cardiac disease (71 [88.8%] of 80). Criteria for initiation of ECMO included a witnessed arrest in a pediatric patient, (including infants and children), lack of recovery of cardiac function within 5 to 10 minutes of institution of cardiopulmonary resuscitation (CPR), absence of coexisting conditions that would preclude survival, and ability to institute ECMO within a short period (25–40 minutes). The median duration of CPR for patients with a favorable
Extracorporeal Membrane Oxygenation
versus unfavorable outcome was 46 minutes versus 41 minutes. Favorable outcomes occurred in 67% of patients who had myocarditis, 50% of those who had cardiomyopathy, 36% following cardiotomy, and 6% of those who had unoperated congenital heart disease. Unfortunately, only 1 (11.1%) of 9 patients who had a noncardiac etiology survived. Several other series have reported favorable outcomes with the use of ECMO for cardiac arrest. In the study by Duncan,11 of 11 children with congenital heart disease and cardiac arrest, 7 (63.6%) survived to hospital discharge and 4 (36.4%) were neurologically intact. A retrospective review of 57 adults receiving ECMO after a cardiac arrest showed improved survival rates (>15 minutes, 32% hospital survival; 15–60 minutes, 48% hospital survival; and >60 minutes, 12% survival).12 Hamrick and colleagues13 failed to find the same results in pediatric patients with a survival rate of only 6%. The duration of arrest before institution of ECMO is controversial, with wide variations in the reported data. A review found no difference between survivors and nonsurvivors regarding length of CPR before cannulation.14 In the adult literature, Chen and colleagues12 reported that more patients survived if the initial CPR duration was less than 60 minutes. Laboratory testing has been postulated to be predictive of survival. In adults, the PaO2 was a predictor of positive neurologic outcome; patients with a PaO2 between 12 and 442 mm Hg predicted a return of consciousness, whereas those who did not regain consciousness had a PaO2 between 34 and 58 mm Hg. Doski and colleagues15 did not find arterial blood gas values to be predictors for survival of pediatric patients. Horisberger and colleagues16 found that the initial base deficit was related to survival in pediatric patients. In this series, 10% of CPR recipients with a base deficit greater than 20 survived 1 year compared with a survival rate of 86% in CPR recipients with a base deficit less than or equal to 15. Ideally, a permanent on-site team is available to allow for early efficient transition to ECMO. Ghez and colleagues17 explored the use of an on-call ECMO response team for patients who had cardiac disease and were undergoing CPR in the pediatric intensive care unit (PICU) or pediatric cardiac catheterization laboratory. Although the study was retrospective and only consisted of 15 episodes in 14 patients, mean CPR time before ECMO was 44 27 minutes, with a 57% survival to discharge. The survival rate improved to 64% in a pediatric study from Boston Children’s Hospital comparing a historical control with patients treated by a rapid-response ECMO team that initiated ECMO within 15 minutes of notification. Rapid-deployment ECMO requires an inhouse dedicated team using a modified ECMO circuit and the capability to initiate cannulation within 10 to 15 minutes of beginning CPR.
HYPOTHERMIC CARDIOPULMONARY ARREST
Initially, extracorporeal circulation was considered the ideal method for resuscitation of hypothermic cardiac arrest. Ruttman and colleagues18,19 studied a consecutive series of 59 patients who had hypothermia and cardiopulmonary arrest. Thirty-four patients were resuscitated by standard extracorporeal circulation, and 25 patients were resuscitated by ECMO. Spontaneous circulation was restored in 32 patients (32 [54.2%] of 59), and 12 (12 [20.3%] of 59) survived. ECMO-assisted resuscitation showed a sixfold higher chance for survival.18 Asphyxia-related hypothermia (avalanche or drowning) was the most predictive adverse factor for survival (relative risk [RR] 5 0.09, 95% confidence interval [CI]: 0.01–0.60). In a subgroup analysis of
957
958
Ayad et al
avalanche victims, ECMO-assisted resuscitation was found to be superior to ECCassisted rewarming with respect to survival (RR 5 7.6, 95% CI: 1.4–50.8).18 COMPLICATIONS OF EXTRACORPOREAL MEMBRANE OXYGENATION
Complications during ECMO are the rule rather than the exception. As of 2005, there was an average of 2.7 complications per case as reported by the ELSO registry. Complications encountered during ECMO can be classified as mechanical or patient related. Mechanical complications include thrombosis in any ECMO circuit component, cannula problems (malposition, kinking, perforation of a vessel, and dislodgement), oxygenator failure, tubing rupture, or pump malfunction. Patient-related complications include surgical or cannula site bleeding, intracranial infarct or bleed, hemolysis, renal insufficiency requiring dialysis or hemofiltration, hypertension, seizures, electrolyte abnormalities, pneumothorax, cardiac dysfunction or arrhythmias, gastrointestinal hemorrhage, and infection. SUMMARY
In summary, ECMO is an important tool to provide oxygen delivery and carbon dioxide removal in addition to cardiac support for patients with intractable reversible respiratory or cardiovascular collapse unresponsive to conventional treatment. Even though ECMO can be a life-saving modality, it is expensive and labor-intensive and carries a significant complication risk. Early recognition and prompt referral of patients who may benefit from ECMO in addition to careful patient selection, continuous communication between ECMO centers and their referral base, and meticulous care can improve the outcome of these critically ill patients who previously had no chance of survival. REFERENCES
1. Cochran JB, Habib DM, Webb S, et al. Pediatric extracorporeal membrane oxygenation (ECMO): a review of the first ten years of experience at the Medical University of South Carolina. J S C Med Assoc 2005;101(4):104–7. 2. Tamburro RF, Bugnitz MC, Stidham GL. Alveolar-arterial oxygen gradient as a predictor of outcome in patients with nonneonatal pediatric respiratory failure. J Pediatr 1991;119(6):935–8. 3. Green TP, Timmons OD, Fackler JC, et al. The impact of extracorporeal membrane oxygenation on survival in pediatric patients with acute respiratory failure. Pediatric Critical Care Study Group. Crit Care Med 1996;24(2):323–9. 4. MacLaren G, Butt W, Best D, et al. Extracorporeal membrane oxygenation for refractory septic shock in children: one institution’s experience. Pediatr Crit Care Med 2007;8(5):1–5. 5. Beca J, Butt W. Extracorporeal membrane oxygenation for refractory septic shock in children. Pediatrics 1994;93(5):726–9. 6. Goldman AP, Kerr SJ, Butt W, et al. Extracorporeal support for intractable cardiorespiratory failure due to meningococcal disease. Lancet 1997;349(9050):466–9. 7. Carcillo JA, Fields AI, American College of Critical Care Medicine Task Force Committee Members. Clinical practice parameters for hemodynamic support of pediatric and neonatal patients in septic shock. Crit Care Med 2002;30(6): 1365–78. 8. Young KD, Seidel JS. Pediatric cardiopulmonary resuscitation: a collective review. Ann Emerg Med 1999;33(2):195–205.
Extracorporeal Membrane Oxygenation
9. de Mos N, van Litsenburg RR, McCrindle B, et al. Pediatric in-intensive-care-unit cardiac arrest: incidence, survival, and predictive factors. Crit Care Med 2006; 34(4):1209–15. 10. Alsoufi B, Al-Radi OO, Nazer RI, et al. Survival outcomes after rescue extracorporeal cardiopulmonary resuscitation in pediatric patients with refractory cardiac arrest. J Thorac Cardiovasc Surg 2007;134(4):952–9. 11. Duncan BW. Mechanical circulatory support in children: extracorporeal membrane oxygenation and ventricular assist devices. Expert Rev Med Devices 2005;2(3):239–41. 12. Chen YS, Chao A, Yu HY, et al. Analysis and results of prolonged resuscitation in cardiac arrest patients rescued by extracorporeal membrane oxygenation. J Am Coll Cardiol 2003;41(2):197–203. 13. Hamrick SE, Gremmels DB, Keet CA, et al. Neurodevelopmental outcome of infants supported with extracorporeal membrane oxygenation after cardiac surgery. Pediatrics 2003;111(6 Pt 1):e671–5. 14. Morris MC, Wernovsky G, Nadkarni VM. Survival outcomes after extracorporeal cardiopulmonary resuscitation instituted during active chest compressions following refractory in-hospital pediatric cardiac arrest. Pediatr Crit Care Med 2004;5(5):440–6. 15. Doski JJ, Butler TJ, Louder DS, et al. Outcome of infants requiring cardiopulmonary resuscitation before extracorporeal membrane oxygenation. J Pediatr Surg 1997;32(9):1318–21. 16. Horisberger T, Fischer E, Fanconi S. One-year survival and neurological outcome after pediatric cardiopulmonary resuscitation. Intensive Care Med 2002;28(3): 365–8 [Epub 2002 Feb 13]. 17. Ghez O, Fouilloux V, Charpentier A, et al. Absence of rapid deployment extracorporeal membrane oxygenation (ECMO) team does not preclude resuscitation ECMO in pediatric cardiac patients with good results. ASAIO J 2007;53(6):692–5. 18. Ruttmann E, Weissenbacher A, Ulmer H, et al. Prolonged extracorporeal membrane oxygenation-assisted support provides improved survival in hypothermic patients with cardiocirculatory arrest. J Thorac Cardiovasc Surg 2007;134(3): 594–600. 19. Available at: http://www.elso.med.umich.edu/Registry.htm. Accessed April 15, 2008.
959
Extracorporeal membrane oxygenation (ECMO) is an advanced technology that is available at a limited number of facilities. It is a supportive modality that is used in acute severe reversible cardiac or respiratory failure in patients of all ages when there is a high risk for dying from the primary disease despite maximal conventional intensive care supportive measures (Fig. 1). ECMO has been used successfully since the 1970s for neonates with persistent pulmonary hypertension refractory to conventional therapy. Hypothermic cardiopulmonary arrest, failed traditional therapies for respiratory diseases, and protracted resuscitation have also been situations in which ECMO has been effective. Similar to cardiac bypass, ECMO is a means by which venous blood is removed from the patient, oxygenated and ventilated, and returned to the arterial or venous circulation of the patient (Fig. 2). ECMO is labor-intensive and expensive, however, with an estimated total hospital cost of $20,000 to $90,000 per patient, and it should be targeted to patients likely to benefit from the therapy. In 2006, the Extracorporeal Life Support Organization (ELSO) reported a survival rate to intensive care unit (ICU) discharge of 65% in a cohort of 32,905 patients. The current reported survival rates are 77% for neonatal respiratory failure, 56% for pediatric respiratory failure, 53% for adult respiratory failure, 43% for pediatric cardiac failure, and 32% for adult cardiac failure. Early initiation of this technology may be life saving for critically ill patients with specific respiratory or cardiac diseases. Early identification of patients who may benefit from this technology and timely transfer to facilities prepared to use this
a
Nationwide Children’s Hospital, 700 Children’s Drive, Columbus, OH, USA The Ohio State University College of Medicine, 370 West 9th Avenue, Columbus, OH 43210, USA c Section of Pediatric Emergency Medicine, Nationwide Children’s Hospital, 700 Children’s Drive, Columbus, OH, USA * Corresponding author. Section of Emergency Medicine, Nationwide Children’s Hospital, 700 Children’s Drive, Columbus, OH. E-mail address: [email protected] (A. Dietrich). b
Emerg Med Clin N Am 26 (2008) 953–959 doi:10.1016/j.emc.2008.07.010 0733-8627/08/$ – see front matter ª 2008 Elsevier Inc. All rights reserved.
emed.theclinics.com
954
Ayad et al
Fig. 1. ECMO system. (Courtesy of O. Ayad, MD, Columbus, OH).
technology if conventional therapies are not effective may improve outcomes for a select subset of patients. RESPIRATORY DISEASES
ECMO has been used for patients with primary acute hypoxic respiratory failure (AHRF) of various causes. Causes of AHRF include viral pneumonia (most common), bacterial pneumonia, aspiration, acute respiratory distress syndrome (ARDS), postoperative or posttraumatic ARDS, pulmonary hemorrhage, and burn injuries. Cochran and colleagues1 reviewed 10 years of experience with pediatric ECMO used for 27 children and adolescents with life-threatening pulmonary conditions unresponsive to conventional intensive care therapy. Most patients were male, and the mean age of the patients was 28 months. Venoarterial access was ultimately used in all but 1 patient. The most frequent diagnoses were presumed viral pneumonia, respiratory syncytial virus (RSV), bronchiolitis, and pertussis pneumonia. The overall survival rate was 67%. Although the number of patients in any category was limited, patients who had pertussis and documented bacterial pneumonia had higher mortality rates than patients with other diagnoses. The mean duration of ECMO was 12.2 days. Reasons for early termination included unrelenting pulmonary hypertension, multiple organ dysfunction, and intracerebral bleeding.
Extracorporeal Membrane Oxygenation
Fig. 2. Venoarterial ECMO circuit. (From Walker G, Liddell M, Davis C. Extracorporeal life support—state of the art. Paediatr Respir Rev 2003;4(2):147–52; with permission.)
Other studies have tried to predict which patients would not benefit from ECMO. An A-a gradient of greater than 450 mm Hg for more than 16 hours and a mean airway pressure of greater than 23 cm H2O were highly predictive of mortality.2,3 This differs from the results noted by Cochran and colleagues,1 who found a survival rate of 67% in a pediatric population with a mean A-a gradient of 580 mm Hg and a mean airway pressure of 29.9 cm H2O. It has been demonstrated that the earlier the referral, especially before significant barotrauma or volutrauma, the better is the outcome.1 ECMO survival also varies, depending on the etiology of the respiratory failure. Survival is highest in cases of aspiration pneumonia (65%) and lowest in Pneumocystis pneumonia (41%) and pertussis (30%). In one series, when all patients were stratified into mortality risk quartiles (based on oxygenation index and pediatric risk of mortality [PRISM] score), the proportion of deaths among ECMO-treated patients in the 50% to 75% mortality risk quartile was less than half of the proportion in non–ECMO-treated patients (28.6% vs. 71.4%; P < .05; Fig. 3).3 REFRACTORY CIRCULATORY FAILURE
Initially, the use of ECMO was contraindicated for patients who had septicemia because of concerns that contamination of the circuit would result in certain death. Several studies have not supported these concerns.4–6 The American College of Critical Care Medicine has published guidelines regarding the management of septic shock in children.7 The recommendation is to consider ECMO for children who are unresponsive to all conventional treatment. Septic shock frequently has a different hemodynamic manifestation in neonates, infants and children, and adults. In
955
Ayad et al
Actual Mortality
956
100 90 80 70 60 50 40 30 20 10 0
ECMO Non-ECMO
<25
25-50
50-75
>75
Predicted Mortality Fig. 3. ARDS: Pediatric ECMO. (From Green TP, Timmons OD, Fackler JC, et al. The impact of extracorporeal membrane oxygenation on survival in pediatric patients with acute respiratory failure. Crit Care Med 1996;24:323–9; with permission.)
neonates, most have persistent pulmonary hypertension. In infants and young children, decreased left ventricular function and low cardiac output are more common, and in adults, the pattern is usually distributive shock. ECMO may be particularly advantageous in children with impaired ventricular function. Studies used to establish these recommendations had fewer than 13 patients in each series, however.5,6 A more recent review of 45 children who received venoarterial ECMO for hemodynamic support has added more credibility to the recommendations, with a 47% survival rate to hospital discharge. The use of ECMO in children with septic shock and multiple organ failure is controversial, with some institutions not placing these patients on ECMO because of dismal survival rates. Potential indications for ECMO support in refractory circulatory failure include failure to wean from cardiopulmonary bypass, cardiopulmonary failure after surgical repair, severe ventricular failure (eg, in myocarditis and cardiomyopathy), severe hypoxemia in cyanotic congenital heart disease if surgery is temporarily contraindicated, a bridge for cardiac transplantation, and refractory septic shock. CARDIAC ARREST
The use of ECMO for patients who have cardiac arrest is increasing in frequency. The survival rate after pediatric cardiopulmonary arrest is dismal. Young and Seidel reported a 13% survival to hospital discharge.8 Out-of-hospital arrests had the worst survival rates at 8.4%, whereas in-ICU or in-hospital arrests had slightly better survival rates (20% and 24%, respectively). In a 5.5-year study examining factors predictive of survival to hospital discharge for pediatric ICU arrests, de Mos and colleagues9 found high in-hospital mortality and morbidity rates and that the use of postarrest ECMO within 24 hours was associated with reduced mortality; the overall survival rate increased to 25%. Factors associated with mortality included the presence of renal dysfunction and an epinephrine infusion at the time of the arrest. Alsoufi and colleagues10 reported on pediatric patients who had refractory cardiac arrest (N 5 80, age range: 1 day to 17.6 years). Most patients had cardiac disease (71 [88.8%] of 80). Criteria for initiation of ECMO included a witnessed arrest in a pediatric patient, (including infants and children), lack of recovery of cardiac function within 5 to 10 minutes of institution of cardiopulmonary resuscitation (CPR), absence of coexisting conditions that would preclude survival, and ability to institute ECMO within a short period (25–40 minutes). The median duration of CPR for patients with a favorable
Extracorporeal Membrane Oxygenation
versus unfavorable outcome was 46 minutes versus 41 minutes. Favorable outcomes occurred in 67% of patients who had myocarditis, 50% of those who had cardiomyopathy, 36% following cardiotomy, and 6% of those who had unoperated congenital heart disease. Unfortunately, only 1 (11.1%) of 9 patients who had a noncardiac etiology survived. Several other series have reported favorable outcomes with the use of ECMO for cardiac arrest. In the study by Duncan,11 of 11 children with congenital heart disease and cardiac arrest, 7 (63.6%) survived to hospital discharge and 4 (36.4%) were neurologically intact. A retrospective review of 57 adults receiving ECMO after a cardiac arrest showed improved survival rates (>15 minutes, 32% hospital survival; 15–60 minutes, 48% hospital survival; and >60 minutes, 12% survival).12 Hamrick and colleagues13 failed to find the same results in pediatric patients with a survival rate of only 6%. The duration of arrest before institution of ECMO is controversial, with wide variations in the reported data. A review found no difference between survivors and nonsurvivors regarding length of CPR before cannulation.14 In the adult literature, Chen and colleagues12 reported that more patients survived if the initial CPR duration was less than 60 minutes. Laboratory testing has been postulated to be predictive of survival. In adults, the PaO2 was a predictor of positive neurologic outcome; patients with a PaO2 between 12 and 442 mm Hg predicted a return of consciousness, whereas those who did not regain consciousness had a PaO2 between 34 and 58 mm Hg. Doski and colleagues15 did not find arterial blood gas values to be predictors for survival of pediatric patients. Horisberger and colleagues16 found that the initial base deficit was related to survival in pediatric patients. In this series, 10% of CPR recipients with a base deficit greater than 20 survived 1 year compared with a survival rate of 86% in CPR recipients with a base deficit less than or equal to 15. Ideally, a permanent on-site team is available to allow for early efficient transition to ECMO. Ghez and colleagues17 explored the use of an on-call ECMO response team for patients who had cardiac disease and were undergoing CPR in the pediatric intensive care unit (PICU) or pediatric cardiac catheterization laboratory. Although the study was retrospective and only consisted of 15 episodes in 14 patients, mean CPR time before ECMO was 44 27 minutes, with a 57% survival to discharge. The survival rate improved to 64% in a pediatric study from Boston Children’s Hospital comparing a historical control with patients treated by a rapid-response ECMO team that initiated ECMO within 15 minutes of notification. Rapid-deployment ECMO requires an inhouse dedicated team using a modified ECMO circuit and the capability to initiate cannulation within 10 to 15 minutes of beginning CPR.
HYPOTHERMIC CARDIOPULMONARY ARREST
Initially, extracorporeal circulation was considered the ideal method for resuscitation of hypothermic cardiac arrest. Ruttman and colleagues18,19 studied a consecutive series of 59 patients who had hypothermia and cardiopulmonary arrest. Thirty-four patients were resuscitated by standard extracorporeal circulation, and 25 patients were resuscitated by ECMO. Spontaneous circulation was restored in 32 patients (32 [54.2%] of 59), and 12 (12 [20.3%] of 59) survived. ECMO-assisted resuscitation showed a sixfold higher chance for survival.18 Asphyxia-related hypothermia (avalanche or drowning) was the most predictive adverse factor for survival (relative risk [RR] 5 0.09, 95% confidence interval [CI]: 0.01–0.60). In a subgroup analysis of
957
958
Ayad et al
avalanche victims, ECMO-assisted resuscitation was found to be superior to ECCassisted rewarming with respect to survival (RR 5 7.6, 95% CI: 1.4–50.8).18 COMPLICATIONS OF EXTRACORPOREAL MEMBRANE OXYGENATION
Complications during ECMO are the rule rather than the exception. As of 2005, there was an average of 2.7 complications per case as reported by the ELSO registry. Complications encountered during ECMO can be classified as mechanical or patient related. Mechanical complications include thrombosis in any ECMO circuit component, cannula problems (malposition, kinking, perforation of a vessel, and dislodgement), oxygenator failure, tubing rupture, or pump malfunction. Patient-related complications include surgical or cannula site bleeding, intracranial infarct or bleed, hemolysis, renal insufficiency requiring dialysis or hemofiltration, hypertension, seizures, electrolyte abnormalities, pneumothorax, cardiac dysfunction or arrhythmias, gastrointestinal hemorrhage, and infection. SUMMARY
In summary, ECMO is an important tool to provide oxygen delivery and carbon dioxide removal in addition to cardiac support for patients with intractable reversible respiratory or cardiovascular collapse unresponsive to conventional treatment. Even though ECMO can be a life-saving modality, it is expensive and labor-intensive and carries a significant complication risk. Early recognition and prompt referral of patients who may benefit from ECMO in addition to careful patient selection, continuous communication between ECMO centers and their referral base, and meticulous care can improve the outcome of these critically ill patients who previously had no chance of survival. REFERENCES
1. Cochran JB, Habib DM, Webb S, et al. Pediatric extracorporeal membrane oxygenation (ECMO): a review of the first ten years of experience at the Medical University of South Carolina. J S C Med Assoc 2005;101(4):104–7. 2. Tamburro RF, Bugnitz MC, Stidham GL. Alveolar-arterial oxygen gradient as a predictor of outcome in patients with nonneonatal pediatric respiratory failure. J Pediatr 1991;119(6):935–8. 3. Green TP, Timmons OD, Fackler JC, et al. The impact of extracorporeal membrane oxygenation on survival in pediatric patients with acute respiratory failure. Pediatric Critical Care Study Group. Crit Care Med 1996;24(2):323–9. 4. MacLaren G, Butt W, Best D, et al. Extracorporeal membrane oxygenation for refractory septic shock in children: one institution’s experience. Pediatr Crit Care Med 2007;8(5):1–5. 5. Beca J, Butt W. Extracorporeal membrane oxygenation for refractory septic shock in children. Pediatrics 1994;93(5):726–9. 6. Goldman AP, Kerr SJ, Butt W, et al. Extracorporeal support for intractable cardiorespiratory failure due to meningococcal disease. Lancet 1997;349(9050):466–9. 7. Carcillo JA, Fields AI, American College of Critical Care Medicine Task Force Committee Members. Clinical practice parameters for hemodynamic support of pediatric and neonatal patients in septic shock. Crit Care Med 2002;30(6): 1365–78. 8. Young KD, Seidel JS. Pediatric cardiopulmonary resuscitation: a collective review. Ann Emerg Med 1999;33(2):195–205.
Extracorporeal Membrane Oxygenation
9. de Mos N, van Litsenburg RR, McCrindle B, et al. Pediatric in-intensive-care-unit cardiac arrest: incidence, survival, and predictive factors. Crit Care Med 2006; 34(4):1209–15. 10. Alsoufi B, Al-Radi OO, Nazer RI, et al. Survival outcomes after rescue extracorporeal cardiopulmonary resuscitation in pediatric patients with refractory cardiac arrest. J Thorac Cardiovasc Surg 2007;134(4):952–9. 11. Duncan BW. Mechanical circulatory support in children: extracorporeal membrane oxygenation and ventricular assist devices. Expert Rev Med Devices 2005;2(3):239–41. 12. Chen YS, Chao A, Yu HY, et al. Analysis and results of prolonged resuscitation in cardiac arrest patients rescued by extracorporeal membrane oxygenation. J Am Coll Cardiol 2003;41(2):197–203. 13. Hamrick SE, Gremmels DB, Keet CA, et al. Neurodevelopmental outcome of infants supported with extracorporeal membrane oxygenation after cardiac surgery. Pediatrics 2003;111(6 Pt 1):e671–5. 14. Morris MC, Wernovsky G, Nadkarni VM. Survival outcomes after extracorporeal cardiopulmonary resuscitation instituted during active chest compressions following refractory in-hospital pediatric cardiac arrest. Pediatr Crit Care Med 2004;5(5):440–6. 15. Doski JJ, Butler TJ, Louder DS, et al. Outcome of infants requiring cardiopulmonary resuscitation before extracorporeal membrane oxygenation. J Pediatr Surg 1997;32(9):1318–21. 16. Horisberger T, Fischer E, Fanconi S. One-year survival and neurological outcome after pediatric cardiopulmonary resuscitation. Intensive Care Med 2002;28(3): 365–8 [Epub 2002 Feb 13]. 17. Ghez O, Fouilloux V, Charpentier A, et al. Absence of rapid deployment extracorporeal membrane oxygenation (ECMO) team does not preclude resuscitation ECMO in pediatric cardiac patients with good results. ASAIO J 2007;53(6):692–5. 18. Ruttmann E, Weissenbacher A, Ulmer H, et al. Prolonged extracorporeal membrane oxygenation-assisted support provides improved survival in hypothermic patients with cardiocirculatory arrest. J Thorac Cardiovasc Surg 2007;134(3): 594–600. 19. Available at: http://www.elso.med.umich.edu/Registry.htm. Accessed April 15, 2008.
959