extracorporeal membrane oxygenation for circulatory support after repair of congenital heart defects

Extracorporeal Membrane Oxygenation for Circulatory Support After Repair of Congenital Heart Defects Larry Weinhaus, MD, Charles Canter, MD, Michael Noetzel, MD, William McAlister, MD, and Thomas L. Spray, MD Divisions of Pediatric Cardiology, Neurology, and Cardiothoracic Surgery, and the Mallinckrodt Institute of Radiology, St. Louis Children’s Hospital, Washington University Medical Center, St. Louis, Missouri

Extracorporeal membrane oxygenation was used for car- diovascular support in 13 infants and children with complex congenital heart disease and 1 premature neonate treated in preparation for pericardial patch tracheoplasty for long-segment tracheal stenosis. Nine patients were weaned from extracorporeal membrane oxygenation. There were five (36%) early deaths and four (29%) late deaths. Cannulation sites included right carotid/ jugular vessels, femoral artery and vein, and right atrium and aorta. In 4 patients, the neck vessels were repaired at decannulation. Five survivors had normal growth and neurodevelopmental evaluations at follow-up. Extracor-

entricular assist devices and balloon counterpulsation V have been successfully used in adult patients for treatment of cardiogenic shock after cardiac operations. Such devices have had only limited use in the pediatric population due to size and technical problems as well as device failures [14]. Although the total number of patients has been small, a few reports [5-12] have described pediatric patients who experienced life-threatening refractory cardiopulmonary failure after repair of congenital heart disease and who were treated with extracorporeal membrane oxygenation (ECMO) for biventricular support.

Since July 1985, we have treated more than 70 pediatric patients with ECMO. Fourteen of these patients were treated with extracorporeal oxygenation for cardiorespiratory support in the perioperative period. This article outlines our experience and includes follow-up of 6 survivors.

Material and Methods Patient Population Between July 1985 and November 1988, 14 patients were placed on ECMO for cardiopulmonary support in the perioperative period (Table 1). Eight were male and 6 were female; age ranged from two days to 7.4 years (mean age, 1.42 years). The patients had a variety of complex

Presented at the Thirty-fifth Annual Meeting of the Southern Thoracic Surgical Association, Marco Island, FL, Nov 1CL12, 1988.

Address reprint requests to Dr Spray, St. Louis Children’s Hospital, 400 S Kingshighway, 5 W 24, St. Louis, MO 63110.

poreal membrane oxygenation can be successfully used as biventricular support in patients with intractable low cardiac output syndrome after repair of congenital heart disease. Best results are obtained in patients who have several hours of stability after operation before initiation of support. Hemorrhagic complications are reduced and long-term neurodevelopmental outcomes appear promising with right neck vessel cannulation and repair. No bleeding complications were observed in patients cannulated through the neck vessels.

(Ann Thorac Surg 1989;48:206-12)

congenital cardiopulmonary defects. In 12 patients, the indications for initiation of ECMO support included progressive hypotension, increasing ventricular filling pres- sures, poor peripheral perfusion, decreased urinary output, and decreased mixed venous oxygen saturations despite maximal pharmacological support. Five patients experienced refractory junctional tachycardia as part of low cardiac output syndrome. An additional patient (patient 3), a 1.1-kg 30-week estimated gestational age premature neonate was placed on ECMO on day 17 of life in preparation for a pericardial patch tracheoplasty for congenital long-segment tracheal stenosis. This infant’s condition was severely unstable, with hypotension, aci- demia, hypoxemia, and hypercarbia (arterial carbon diox- ide tension > 260 mm Hg), and he was placed on ECMO support for resuscitation. After confirmation of adequate neurological function, repair of the trachea was performed using ECMO for ventilatory support. Extracorpo- real membrane oxygenation was continued for six days after surgical repair of the trachea. Patient 13 was placed on ECMO preoperatively for circulatory support of biventricular failure secondary to congenital mitral regurgitation.

The ECMO circuit described by Bartlett and colleagues [13, 141 and used in our institution for neonatal pulmonary support was used for all postoperative patients. A SciMed (0.8 m’) membrane oxygenator and Omnitherm heat exchanger (SciMed Life Systems, Minneapolis, MN) were connected to a 4-inch (10.16 cm) Polystan Verticlude direct drive roller pump (Polystan Ah, Copenhagen, Denmark) by f-inch (6.35 mm) tubing. The pump was

0 1989 by The Society for Thoracic Surgeons 0003-4975/89/$3.50

Ann Thorac Surg 1989;48:206-12

WEINHAUS ET AL 207 ECMO FOR POSTOPERATIVE SUPPORT

Table 1. Patient Characteristics

Time to Time on Patient Age ECMO ECMO No. ( Y d Diagnosis (h) (h) Cannulation Weaned Outcome

1 4.8

2 3.3 3 17 days 4 7.4 5 0.5 6 1.2 7 8 days

8 0.4 9 0.2

10 13 days 11 1.3 12 0.6 13 10 days 14 2 days

Mean 1.42

AV canal, tetralogy

EFE, transplant Tracheal stenosis, PDA Single ventricle, Pul Atr AV canal, DORV Single ventricle, Pul St Hypoplastic left heart

AV canal, CoA, Pul HTN TGA, VSD Truncus arteriosus Tetralogy Tetralogy Congenital MR, Pul HTN

syndrome

IAA-B

72

4 Preoperative

1 8

12 OR

8 OR 7

25 OR

Preoperative OR

11.4

144

121 87 46

117 59 6

108 31 58 47 56

269 142

FemIFem

AoIRA CarIJug FemiFem CariJug CariJug AolRA

CariJug AoIRA CariJug AolRA AolRA CarIJug CarIJug

Hospital death (18

Hospital death (2 days) Hospital death (10 mo) Died Survived Survived Died

days)

Survived Died Survived Survived Died Died Hospital death (12

days)

Ao = aorta; AV = atrioventricular; Car = internal carotid; CoA = coarctation of the aorta; DORV = double outlet right ventricle; EFE = endocardia1 fibroelastosis; MR = mitral regurgitation; OR = operating room; Pul St = pulmonary stenosis;

Fem = femoral; IAA-B = interrupted aortic arch type B; Jug = internal jugular; PDA = patent ductus arteriosus; Pul Atr = pulmonary atresia; Pul HTN = pulmonary hypertension;

RA = right atrium; TGA = transposition of the great arteries; VSD = ventricular septa1 defect.

servo-controlled by a silicone venous reservoir in contact with a switch that automatically inactivates the roller pump if reservoir volumes fall below a preset level. A recirculating water heater was connected to the heat exchanger and temperatures were maintained at 38°C. Initial flow rates were set at 100 to 120 mL/kg/min. The patients' blood gases were monitored and adjusted by altering the sweep rate and composition of the gases passing across the membrane. After heparin anticoagula- tion (1.5 mgkg), the activated clotting times were monitored and heparin infusions were adjusted to maintain the activated clotting times at 200 to 220 seconds.

Three cannulation sites were used for the venoarterial bypass. In 5 patients a transthoracic approach was used. Cannulas were placed in the aorta and right atrium directly. In 3 of these patients who required ECMO support after they could not be weaned from cardiopulmonary bypass, the same bypass cannulas were left in place and connected to the ECMO circuit in the operating room. The cannulas were then brought through the sternotomy, and the sternum was loosely approximated. Femoral artery and vein cannulation was performed through a groin incision in 2 patients. The right common carotid artery and internal jugular vein were cannulated through a lateral neck dissection on the right in the remaining 7 patients; in 1 patient (patient 14) by extension of the median sternotomy incision. Four patients under- went vascular repair of the carotid artery and jugular vein at the time of decannulation.

After initiation of ECMO support, inotropic agents were rapidly decreased to low levels or discontinued and ventilatory rate and oxygen settings were reduced. Vaso- dilator therapy could often be instituted or increased after biventricular support with ECMO was started.

Echocardiographic and hemodynamic measurements were observed during brief periods of decrease in ECMO flow for evaluation of recovery of cardiac function. When the patient exhibited stable hemodynamics during trials of low flow, gradual weaning of flow rates to less than 100 to 200 mL/min with adjustment of ventilation and inotropic support was performed. Decannulation and vascular repair were performed in the intensive care unit for all patients except patient 14, who was stable and trans- ported back to the operating room for decannulation of the neck vessels through median sternotomy incision and vascular repair.

Six patients were examined on follow-up 1 to 12 months after operation. Full neuromuscular examinations and the Denver Developmental Screening Tests were performed in 5. In 5 patients who had carotid-jugular cannulation, duplex Doppler examinations [15-171 of the neck vessels were performed with a range-gated pulse Doppler system (Acuson 128) with a 5-MHz linear phased-array transducer. Color-flow Doppler echocardiography was performed (Quad 1; Quantum Medical Systems) with a 7.5- MHz linear phased-array transducer. The circle of Willis was examined by color-flow Doppler echocardiography in

208 WEINHAUS ET AL ECMO FOR POSTOPERATIVE SUPPORT


patient 10 (neck vessels ligated) to evaluate the cerebral blood flow pattern.

Results In our series, 12 patients had a time interval from operation to initiation of ECMO support of 0 to 36 hours (mean, 11.1 hours). Two patients were placed on ECMO before operation (Table 1). Peak flow rates were 0.8 to 2.4 L/min/m2. The duration of ECMO support ranged from 6 to 269 hours (mean, 92.2 hours).

Nine of 14 (64%) patients were successfully weaned from ECMO. Five patients who could not be weaned from the device died (36%). Three patients who could not be weaned from cardiopulmonary bypass died in the operating room, 1 after a Norwood procedure for hypoplastic left heart, 1 after a Senning repair of transposition of the great vessels and closure of multiple ventricular septal defects, and 1 after reoperation for residual inlet-type ventricular septal defect and tetralogy of Fallot. Patient 4 was started on ECMO only one hour after completion of a central aortopulmonary shunt for palliation of univentricular heart with pulmonary atresia and severe cyanotic cardiomyopathy. She experienced intraoperative hypotension, bradycardia, and cardiac arrest. External chest massage was continued while the patient was placed on ECMO through the groin. Bleeding from the cannulation site, surgical lines, and endotracheal tube was excessive. The patient did not recover neurological function, and ECMO was discontinued. An additional patient was placed on ECMO for biventricular support for congenital mitral and tricuspid valve insufficiency and pulmonary hypertension in preparation for mitral valve replacement, which was successfully accomplished with carotid/jugular cannulas for perfusion during operation. Despite improvement in cardiac function, pulmonary hypertension did not resolve after valve replacement and the patient died shortly after being weaned from ECMO ten days later.

Four (29%) deaths occurred in the 9 patients successfully weaned from ECMO. The first patient experienced biventricular failure and progressive renal failure after repair of double-outlet right ventricle with pulmonary stenosis and inlet-type ventricular septal defect. He un- derwent dialysis while on ECMO; renal function returned while he was on ECMO therapy. Serious gastrointestinal bleeding and seizures complicated his course, and cannulation through the femoral vessels resulted in leg ischemia requiring fasciotomies. Although he was successfully weaned from ECMO and ventilatory support, an over- whelming fungal infection developed and he died 18 days later. Patient 2 died two days after ECMO decannulation after an acute elevation of pulmonary artery pressure with a resultant low output and hypoperfusion. Bleeding around the transthoracic cannulas also complicated her ECMO course. Patient 3 died 10 months after ECMO of bronchopulmonary dysplasia and chronic respiratory failure unrelated to ECMO. The fourth patient (patient 14) required support in the operating room after she could not be weaned from bypass after repair of interrupted aortic arch and ventricular septal defect. She died 12 days

Table 2. Cannulation Follow-up

Patient No. Site Repair Doppler

3 Neck + Not studied 5 Neck + Normal flow, 40% narrow 6 Neck + Normal 8 Neck + Normal flow, 40% narrow

10 Neck - Retrograde flow through

11 Transthoracic - Not studied 14 Neck + Normal

left vessels

after ECMO decannulation secondary to repeated pulmonary hypertensive crises.

Of the 9 patients weaned from ECMO, 5 (36%) are late survivors. Two of these patients were placed on ECMO eight hours after atrioventricular canal defect repair (Table 1). Both had pulmonary hypertension preoperatively. Twelve hours after septation procedure and right ventricular outflow patch placement of univentricular heart and pulmonary stenosis, patient 6 required ECMO for low cardiac output syndrome. In patient 10, refractory supraventricular tachycardia and cardiac arrest developed seven hours after repair of truncus arteriosus type I. She was placed on the device while cardiopulmonary resuscitation was continued. Patient 11 had refractory right ventricular failure after repair of tetralogy of Fallot and required ECMO 25 hours after operation.

Six patients were evaluated 3 to 12 months after ECMO. Five had normal neurological and motor examinations. One had mild gross motor delay. Development was otherwise appropriate for age. None of the patients had residual seizure activity, and none were taking anticon- vulsive medications at follow-up.

The cerebral vessels of 5 patients were examined using Doppler ultrasonography (Table 2). Patients 6 and 14 were normal. Patients 5 and 8 had slight narrowing of the carotid artery at the surgical site just below the carotid bulb. The carotid artery was 4 mm in diameter below the surgical site and 3 mm in diameter at the surgical site (Fig 1). No turbulent flow was noted in either patient. Patient 5 had a small piece of tissue protruding into the carotid vessel lumen at the anastomosis site. The internal jugular veins had normal flow; diameters could not be assessed. Patient 10 (right carotid/jugular ligated at decannulation) had normal left common, internal carotid, external carotid, and vertebral arteries. The left jugular vein was also patent. The right vertebral artery was well imaged; on the right there was no evidence of common carotid artery or internal jugular vein. Intracranial color Doppler imaging demonstrated normal flow in both anterior and middle cerebral arteries with reverse flow in the A-1 segment of the right middle cerebral artery and in the proximal portion of the internal carotid artery.

Complications were common in our patients (Table 3). The most frequent problems were tachyarrhythmias, which were noted before ECMO and contributed to the



2 patients. Four patients had seizures, in 3 patients related to major neurological dysfunction and in 1 patient related to hypocalcemia. The premature infant (patient 3) had a subependymal hemorrhage before ECMO and mild and unchanging intracranial ventricular dilatation after ECMO.

Fig I . Two-dimensional ultrasonogram of the right carotid artery in longitudinal view. A narrowing is apparent (arrows) at the surgical site in the comnion carotid artery (CC) below the carotid bulb (CB).

indications for cannulation. Junctional tachycardia, associated with the low cardiac output syndrome, was noted in 5 (36%) patients and resolved soon after hemodynamic stabilization on ECMO and weaning of inotropic agents. Bradycardia, supraventricular tachycardia, and surgically induced heart block were each noted in 1 patient.

Infection occurred in 2 patients (14%). One patient (patient 1) died after Escherichia coli and Candida sepsis developed. Patient 5, a late survivor, was treated for Pseudomonas aeruginosa, which was cultured from his respiratory tree and central line catheter tip. An acute pulmonary hypertensive event, possibly from a reactive pulmonary vascular bed, led to the death of patient 2; chest roentgenogram suggested early pneumonia in the right upper lobe, although cultures were negative on antibiotics. Mediastinitis did not develop in any patient in this series, although patient 1 had signs of chest wound infection as a part of a disseminated Candida infection.

In patient 8, increasing pericardial effusion and tamponade developed after decannulation, which was observed by echocardiography. At operation, clot was removed from the mediastinum.

Clinically significant bleeding occurred in 5 patients (36%). Three of these patients had transthoracic cannulation and 2 had femoral cannulation. One patient with carotid/jugular cannulation had substantial mediastinal drainage but did not require exploration or interruption of ECMO support. The cannulas in this infant were placed by extension of the median sternotomy incision, and ECMO was started intraoperatively. No clinically significant bleeding was encountered in patients with carotid/ jugular ECMO access through a separate neck incision.

Acute renal failure was noted in 4 patients (29%). No chronic renal failure has been observed; however, dialysis

Comment Use of ventricular assist and intraaortic balloon counterpulsation devices for support of the failing circulation in adult patients who experience postoperative cardiogenic shock has become widely accepted [14]. Similar devices have had restricted use for infants and children after repair of congenital cardiopulmonary defects primarily due to the size limitations of current devices over the wide age and weight ranges of pediatric patients. The recogni- tion that ECMO can provide univentricular or biventricular cardiac as well as respiratory support has extended application of ECMO to infants and children who develop refractory postoperative cardiogenic shock after repair of congenital heart defects.

Soeter and colleagues [5] first reported survival using ECMO in a young patient with acute cardiopulmonary insufficiency after correction of tetralogy of Fallot. Other reports suggested that ECMO might be a successful treatment for children with postoperative cardiac failure and potentially reversible pulmonary disease [6, 71. Post- operative paroxysmal pulmonary hypertension after ventricular septa1 defect repair in an infant was successfully treated with ECMO by Cullen and associates [8] . The first larger series of patients suffering from cardiogenic shock and treated with ECMO was reported by Pennington and co-workers [9] in 1984. Four of the 14 reported patients were of pediatric age and had developed cardiac failure after operation for congenital heart disease; 3 survived

Table 3 . Complications

Complication n

Bleeding” 5 Transthoracic cannulation 3 Femoral cannulation Neck cannulation

Seizures Oliguriaianuria Dialysis on ECMO Sepsis Tamponade (after decannulation) Mediastinitis Arrhythmias (before ECMO)

Junctional tachycardia Supraventricular tachycardia Heart block Bradycardia

2 0 4 4 2

2 1 0 8 5 1 1 1

Of sufficient severity to require reexploration or terminate ECMO. or hemofiltration was used in conjunction with ECMO in ECMO = extracorporeal membrane oxygenation


Ann Thorac Surg 1989;48:20&12

Table 4. Postoperative Extracorporeal Membrane Oxygenation

Reference

Intraoperative ECMO Overall

Year Patients Survival" Patients" Survival

Soeter et a1 [5] Bartlett et a1 [6] Cullen et a1 [8] Redrnond et a1 [lo] Kanter et a1 [ll] Bartlettb [ll] Trento et a1 [12] Weinhaus et a1 (present study)

Total

1973 1977 1986 1987 1987 1987 1988 1989

1 3 1 4

13 14 7

14

57

1 (100) . . . . . . 1 (33) . . . . . . 1 (100) . . . . . . 1 (25) 2 (50) 0 6 (46) 1 (8) 0 5 (36) . . . . . . 4 (57) 1 (14) 0 6 (36) 4 (29) 0

25 (44) 8 (14) 0

a Numbers in parentheses are percentages. Surgical Association, July 1986.

ECMO = extracorporeal membrane oxygenation.

Transcription of Dr Bartlett's discussion from the Twelfth Annual Meeting of the Western Thoracic

after being weaned from ECMO. Redmond and colleagues [lo] described use of ECMO in 5 infants with congenital heart disease and 4 pediatric patients after cardiac operation, with 60% and 50% success rates, re- spectively. In 1987, Kanter and associates [ll] reported experience with 13 patients (4 previously reported by Pennington and co-workers) who required circulatory support with ECMO for refractory cardiac failure after repair of congenital heart disease [7]; 46% of these children survived to leave the hospital.

In our series of 14 infants and children, 64% of the patients were weaned from ECMO; these figures compare favorably with those published by Redmond and colleagues (50%) [lo] and Kanter and associates (54%) [ll]. In addition to the patients unable to be successfully weaned from ECMO support, there were 4 late deaths, for a 36% overall survival. A summary of the reported series of pediatric patients who required ECMO for postoperative support is presented in Table 4. Approximately 45% of reported patients survived to leave the hospital.

Whereas use of ECMO for neonates with respiratory insufficiency has been associated with a 10% to 35% incidence of neurological injury [18-211, none of our patients had intracranial hemorrhage or infarct related to ECMO, although in 1 patient cerebral infarctions secondary to disseminated Candida sepsis developed several weeks after the patient was weaned from ECMO support. None of the nonhemorrhagic neurosonographic findings described by Luisiri and associates [15] have been seen in our patients to date. In the neonate experience, normal intellectual outcome was noted in 64% to 71% of survivors [22, 231. Kotogul and associates [24], however, reported only 32% of their patients as normal. All 6 survivors in our series were examined 1 to 12 months after ECMO support. Five have normal neurological evaluations, although 1 has mild gross motor delay. Growth has also been appropriate. None of the patients have residual seizure activity. There are no fundamental differences in timing or technique to explain the differences in neurological se- quelae in the series of cardiac patients as compared with

the neonatal respiratory patients, although the age has generally been younger in the latter group.

Hemorrhage remains a serious complication with the use of ECMO after cardiac surgical procedures. In our patients, hemorrhagic complications were frequent when the patients were placed on ECMO in the operating room without time for hemostasis and correction of coagulation deficits after cardiopulmonary bypass. The majority of hemorrhagic complications occurred in patients who had transthoracic cannulation, which may reflect the need for ECMO intraoperatively or the constant cardiac motion at the venous and aortic cannulation sites. Bleeding around the cannulation sites was the most common cause of reexploration when the transthoracic approach was used. None of the patients in this series were prematurely removed from ECMO because of excessive hemorrhage, although the magnitude of transthoracic hemorrhage was a factor in the decision for weaning from the device in patient 7, who had improvement but not resolution of pulmonary hypertension and right heart failure after heart transplantation.

Transthoracic cannulation has been the approach of choice for Pennington and Kanter and their colleagues [9, 111 even when ECMO was started in the intensive care unit. Although a substantial number of hemorrhagic complications occurred, these investigators suggested that it was simpler to reopen the sternotomy site and place transthoracic cannulas than to make a fresh groin incision and place ileofemoral cannulas. Inadequate flows have also been a problem with the groin approach.

We prefer right carotid artery and jugular venous cannulation. Attaining adequate ECMO flows (0.8 to 2.5 L/min/m2) was not a major problem in any of the 7 patients in whom this approach was used, although venous drainage limited flow (0.85 L/min/m*) early after initiation of support in 1 patient who had Senning atrial repair of transposition of the great vessels. With volume infusion, flow could be increased to 1.1 L/min/m2 during the first 20 hours of support. Carotid/jugular cannulation has been used routinely for neonatal ECMO, and the

Ann Thorac Surg 1989;48:20&12


transition to use in the postoperative congenital heart patients was readily made. Access was easily achieved, and severe bleeding complications did not occur in any of the 7 patients, although 1 patient who was cannulated through the neck vessels through the median sternotomy incision had marked mediastinal drainage that did not require reexploration.

It has become our practice to repair the internal jugular vein and right common carotid artery at the time of decannulation from ECMO. No immediate effects have been noted to date with this approach. Doppler neck examinations have revealed patency of the vessels 1 to 12 months after repair in surviving patients, and although 2 of the 5 patients examined had minor structural abnor- malities (Fig l) , none had a flow disturbance related to the repair at the cannulation site. We hope that vessel repair will promote a more normal cerebral blood flow for the brain, which may still be recovering from postoperative insults, cardiac decompensation, or residual cardiac dysfunction, and will contribute to improved developmental outcomes. In addition, these vessels may remain patent in the event that access is needed at a later date.

Patients who require circulatory support at the time of weaning from cardiopulmonary bypass in the operating room or shortly thereafter appear to be at greatest risk of not being weaned from ECMO support (Table 1). As shown in Table 4, 8 patients in the collective reported series of patients were placed on ECMO in the operating room immediately after repair of congenital cardiac defects; none survived. Several of these patients had progressive profound hypotension and bradycardia despite good ECMO flows. Perhaps the poor results in these patients reflect more profound cardiac dysfunction that cannot be adequately supported without ventricular ejec- tion sufficient to prevent distention. The best success in this series was obtained in cases of primarily right-sided cardiac dysfunction (Table 1). Extracorporeal membrane oxygenation is able to provide biventricular support; however, flow levels that provide full cardiopulmonary bypass may increase the afterload of the left ventricle, which is not vented during the procedure. Such preload and afterload increases may limit recovery of left ventricular function. One patient in this series (patient 14) had initiation of extracorporeal oxygenation support for biventricular failure in the operating room but had a small residual ventricular septa1 defect that may have decom- pressed the left ventricle and permitted recovery of the left side of the heart. The patient could be weaned from ECMO but subsequently died of persistent pulmonary hypertensive events. Therefore, we believe that extension of the ECMO technique with decompression of the left ventricle in cases of obvious biventricular failure is advis- able and have undertaken a modification of our technique to provide this type of decompression.

As demonstrated in this series and in other reported patients, ECMO can be an effective therapy for pediatric patients with intractable low cardiac output syndrome after repair of congenital heart defects. We recommend carotid artery and jugular venous cannulation in patients who develop low cardiac output syndrome outside of the operating room. Hemorrhagic complications are reduced

and long-term neurodevelopmental outcomes appear promising when right carotid artery and jugular venous cannulation and repair are performed.

This report describes an evolution of the use of ECMO for extracorporeal circulatory support. Our experience has led us to consider use of this technique in any patient who cannot be weaned from cardiopulmonary bypass in the operating room or in whom a severe refractory low cardiac output syndrome develops postoperatively. Al- though specific criteria for exclusion of ECMO support have not been established, procedures such as the pallia- tive operation for hypoplastic left heart syndrome do not appear to be good procedures in which to use extracorporeal support. In the condition of single ventricle with shunt-dependent pulmonary circulation, ECMO flow may not effectively unload the ventricle because the arterial return to the patient may contribute to pulmonary overcirculation and limit systemic flow. In the 1 patient in this series in whom ECMO was used after the first-stage Norwood procedure, arterial blood pressure was not effectively supported with the technique despite improvement in blood gases. Selective use of ECMO may be most effective in such patients when severe hypoxemia occurs in the early postoperative period without hypoperfusion and ventricular dysfunction, but when the pulmonary vascular resistance may be expected to decrease with time. The problems of cannula placement in patients with a Senning intraatrial baffle repair have limited venous return in 1 patient, but we do not consider this a contrain- dication to ECMO. Relative contraindications to use of ECMO include severe coagulopathies or known neurologic damage.

Clearly, ECMO has been most effective in conditions of right heart dysfunction such as progressive right heart failure after operations that relieve right ventricular outflow tract obstruction. We consider the technique very valuable in patients with progressive right heart failure or transient forms of cardiac failure such as junctional tachy- cardias or other refractory arrhythmias that may occur in association with a low cardiac output syndrome. It may also be used for temporary respiratory support for perioperative resuscitation or tracheal repair. As more experience with the use of ECMO in the postoperative period is gained, the relative indications and contraindications for the technique may be better defined.

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extracorporeal membrane oxygenation for circulatory support after repair of congenital heart defects

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