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ORIGINAL ARTICLE  
Year : 2011  |  Volume : 14  |  Issue : 1  |  Page : 19-24
Extra corporeal membrane oxygenation after pediatric cardiac surgery: A 10 year experience


1 Department of Cardiac Anesthesia, All India Institute of Medical Sciences, New Delhi - 110 029, India
2 Department of Perfusion Technology, All India Institute of Medical Sciences, New Delhi - 110 029, India
3 Department of Cardiothoracic and vascular surgery, All India Institute of Medical Sciences, New Delhi - 110 029, India

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Date of Submission21-Sep-2010
Date of Acceptance25-Oct-2010
Date of Web Publication31-Dec-2010
 

   Abstract 

Indications for extra corporeal membrane oxygenation (ECMO) after pediatric cardiac surgery have been increasing despite the absence of encouraging survival statistics. Modification of ECMO circuit led to the development of integrated ECMO cardiopulmonary bypass (CPB) circuit at the author's institute, for children undergoing repair of transposition of great arteries among other congenital heart diseases (CHD). In this report, they analyzed the outcome of children with CHD, undergoing surgical repair and administered ECMO support in the last 10 years. The outcome was analyzed with reference to the timing of intervention, use of integrated ECMO-CPB circuit, indication for ECMO support, duration of ECMO run and the underlying CHD. The results reveal a significantly improved survival rate with the use of integrated ECMO-CPB circuit and early time of intervention rather than using ECMO as a last resort in the management. The patients with reactive pulmonary artery hypertension respond favorably to ECMO support. In all scenarios, early intervention is the key to survival.

Keywords: ECMO, pediatric cardiac surgery, TGA

How to cite this article:
Chauhan S, Malik M, Malik V, Chauhan Y, Kiran U, Bisoi A K. Extra corporeal membrane oxygenation after pediatric cardiac surgery: A 10 year experience. Ann Card Anaesth 2011;14:19-24

How to cite this URL:
Chauhan S, Malik M, Malik V, Chauhan Y, Kiran U, Bisoi A K. Extra corporeal membrane oxygenation after pediatric cardiac surgery: A 10 year experience. Ann Card Anaesth [serial online] 2011 [cited 2014 Aug 30];14:19-24. Available from: http://www.annals.in/text.asp?2011/14/1/19/74395



   Intoduction Top


The indications for perioperative use of extracorporeal membrane oxygenation (ECMO) in cardiac surgery have been increasing with the advancements in the understanding of pathophysiology of cardiac diseases and their treatment and in technology. The indications for ECMO support in children with congenital heart disease (CHD) are well defined and range from use of ECMO for preoperative cardiopulmonary support to its use for management of failure to wean from cardiopulmonary bypass (CPB) to resuscitation after cardiac arrest in the postoperative period. The survival statistics after ECMO support following cardiac surgery (around 50% for infants and 15% for adults) have not been very encouraging and have remained static since its inception in 1973. [1],[2],[3] There have been reports of better chances of survival of infants undergoing cardiac surgery when ECMO support was initiated in the operating room than when it was initiated in an emergency situation in the postoperative period. [4]

ECMO equipment may be modified as per the specific needs of the patient and the operating personnel. The integrated ECMO-CPB circuit devised at the author's institute [Figure 1] and [Figure 2] has been instrumental in the development and progress of the institute's ECMO program and has helped in improving the survival of patients. [5] The integrated ECMO-CPB circuit involves a slight modification of the CPB circuit by utilizing the ECMO oxygenator during the CPB. The oxygenator that is routinely a part of CPB circuit is not used because of its short life.
Figure 1 :Integrated ECMO-CPB circuit in operating room

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Figure 2 :Integrated ECMO-CPB circuit in ICU

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In this report, we analyze the survival after ECMO support in children undergoing repair of CHD over a 10-year period, with reference to the indication for ECMO support, time of initiation of ECMO support, underlying CHD and the effect of use of integrated ECMO-CPB circuit. Survival was considered if the child survived till discharge from the intensive care unit (ICU).


   Materials and Methods Top


The medical records of all patients requiring ECMO support perioperatively during cardiac surgery for repair of CHD, from January 2000 till July 2010, were analyzed. Each patient record was analyzed for indications for ECMO, time of initiating ECMO support, underlying diagnosis, use of integrated ECMO-CPB circuit, survival, complications if any and the cause of mortality.

ECMO technique

None of the children studied during the period required ECMO support before surgery. Venoarterial ECMO was used in all the patients. Most of the patients had an ascending aortic cannula and single venous cannula in the right atrium in situ for cardiac surgery which were connected to the ECMO circuit in the operating room. ECMO support when initiated in the postoperative period in the ICU required insertion of ascending aortic cannula and single venous right atrial cannula after removal of sternal sutures. Heparin infusion was started at 100 μg/Kg/min and titrated to maintain activated clotting time between 180-220 sec. Hematocrit and platelet counts were maintained at more than 40% and more than 1,20000/ μl respectively by packed red blood cell and platelet transfusions. Most patients received either Aprotinin in the dose of 2 ml/Kg before onset of CPB, 2 ml/Kg on CPB and 1 ml/Kg/hour infusion for 6 hours after CPB or Epsilonamino caproic acid in the dose of 100-125 mg/Kg before onset of CPB and on CPB and 10 mg/Kg/hour infusion for 4 hours. Patients put on ECMO in the postoperative period received only the infusion doses of antifibrinolytics as described above. Sternum was left open and the wound covered by PVC bag (blood collection bag) which was further covered by sterile plastic drape.

On ECMO support, inotropes were tapered to maintain mean arterial pressure of 40-50 mmHg with a central venous pressure (CVP)/left atrial pressure (LAP) of <6 mmHg. With maximal flow rates on ECMO (125-150 ml/kg), the patients were ventilated with fraction of inspired oxygen = 21%, with respiratory rate = 10/min, tidal volume = 6-8 ml/kg, and positive end expiratory pressure (PEEP) = 5-6 cm H 2 O to prevent atelectasis. Body temperature was maintained at 36-37ºC by the use of water mattress and convection body warmer. A hemofilter was incorporated in the circuit to enable fluid removal based upon input-output balance at 10-50 ml/kg/hour.

The patients were monitored clinically and biochemically. Clinically, ECMO flow rates, CVP/LAP, heart rate (HR), mean arterial blood pressure (ABP), oxygen saturation, urine output, and temperature were monitored and maintained by appropriate intervention. Biochemically, hemogram, liver function test, renal function test, mixed venous oxygen saturation, daily blood cultures (aerobic/anaerobic/fungal) were monitored and maintained. A transthoracic echocardiogram was done after every 24 hours to evaluate myocardial contractility. Cranial ultrasound through the anterior fontanel was done every 24 hours to rule out intraventricular bleeding.

Weaning was initiated when all clinical, biochemical, and echocardiographic parameters were satisfactory. Weaning involved gradual decrease in flow by 10% every 1-2 hours to a flow of 30-40 ml/kg/min, with maintenance of clinical parameters. A trial of 1 hour without ECMO support was given by clamping the arterial and venous cannulae and declamping the recirculation line. Once the patient was able to maintain hemodynamic parameters according to age, urine output (at least 1 ml/kg/hour), and arterial blood gases (minimal acidosis with satisfactory PaO 2 and PaCO 2 ), decannulation was done. Sternal closure was performed a day after decannulation.


   Results Top


A total of 94 patients received ECMO support following cardiac surgery for repair of CHD during the 10-year period of study with survival to discharge of 61 patients (64.8%). Patient's median age and weight were 53 days (range 29 days-4 years) and 3.41 kg (range 2.1-12.9 kg), respectively.

Seventy-nine patients received aprotinin at a dose of 2 ml/kg before the onset of CPB, 2 ml/kg on CPB and 1 ml/kg/hour infusion for 6 hours after CPB. Five patients received epsilon amino caproic acid at a dose of 100-125 mg/kg before the onset of CPB and on CPB and 10 mg/kg/hour infusion for 4 hours.

Eighty-five children had an ascending aortic cannula and a single venous cannula in the right atrium in situ for cardiac surgery, which were connected to the ECMO circuit in the operating room. Nine patients required ECMO support in the postoperative period in the ICU, which was initiated by insertion of ascending aortic cannula and single venous right atrial cannula after removal of sternal sutures in the ICU.

[Table 1] depicts the outcome by timing of intervention and use of integrated ECMO-CPB circuit. None of the children required ECMO support before surgery. The integrated ECMO-CPB circuit was used in 63 children. All of them were diagnosed cases of transposition of great arteries (TGA) with intact ventricular septum (IVS) with regressed left ventricle and were at high risk for the requirement of postoperative ECMO support after Jatene's arterial switch operation. The survival in this group of patients was 76% (48 out of 63 patients) as against only 25% survival in patients with TGA with IVS who could not be weaned from CPB and in whom integrated ECMO-CPB circuit was not used. Overall, out of 94 children, failure to wean from CPB was seen in 22 patients of whom only 10 survived (45.4%). Postoperative ECMO support in the ICU was required in nine children out of whom only three survived (33%).
Table 1 :Outcome by time of initiation and use of integrated ECMO-CPB circuit

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[Table 2] depicts the outcome by diagnosis. Seventy-two of 94 patients had TGA with 69 having TGA with IVS. 70.8% (51 of 72) patients with TGA survived after ECMO support. One patient required emergency postoperative ECMO support as part of cardiopulmonary resuscitation in ICU. The patient was later diagnosed to have residual VSD and right ventricle outflow tract gradient which was surgically corrected leading to patient survival. Overall survival in children with TOF and ECMO support was 43% (three out of seven patients survived). Sixty-six percent (two out of three) patients operated for atrioventricular septal defect (AVSD) survived after ECMO support.
Table 2 :Outcome by diagnosis

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Outcome by indication for ECMO

The main reason for failure to wean from CPB were severe pulmonary artery hypertension (PAH) (10 patients) and myocardial dysfunction (12 patients). Severe PAH was defined as pulmonary artery systolic pressure >75% of systemic pressure.

In patients with PAH, 6 out of 10 survived with 66% survival in children with AVSD (2 out of 3) and 50% in children with VSD (3 out of 6). In patients with myocardial dysfunction, three were later diagnosed to have residual defects in ICU, none of whom survived. Survival in children with myocardial dysfunction was 33% (4 out of 12 patients).

Postoperative ECMO support which was initiated in the ICU was required in nine patients mainly for intractable ventricular fibrillation (VF) (seven patients), respiratory cause in one patient and residual defect in one patient. Overall survival was 33% with two out of seven children with VF surviving.

[Table 3] depicts the outcome by duration of ECMO run. The median duration of ECMO run was 42 hours; the shortest duration was 22 hours and the longest 11 days. The child with the longest duration of ECMO run died due to fungal septicemia. The chances of survival decrease with increasing duration of ECMO run with a drastic decrease in survival after 72 hours of ECMO support. Chi-square analysis for linear trend in proportion was applied for statistical analysis. Assuming an odd's ratio for survival with duration of ECMO run of 24-48 hours to be 1, children with ECMO run of more than 72 hours have only 10% chance of survival. P-value was calculated to be 0.000064 and is significant.
Table 3 :Outcome by duration of ECMO run

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Complications

The major complications noted were systemic infection in the form of sepsis (23 patients), renal failure (14 patients), and mechanical complications (14 episodes). Mechanical complications were mainly seen in the initial years of ECMO program, which included accidental disconnections, clotting in lines, stuck roller pump, tubing rupture, accidental air in lines with no mortality associated with them. Only 6 out of 23 patients with systemic infection survived. Twelve patients with renal failure did not survive despite the ongoing hemofiltration. None of the children with intracranial hemorrhage survived.


   Discussion Top


Use of ECMO support after pediatric cardiac surgery is even today a last option in the management of patients with CHD. There have been many reports that support the early initiation of ECMO as a predictor of survival following ECMO support. [4],[6] Ferrazi et al, [7] studied six patients undergoing repair of CHD. Two of their patients could not be weaned from CPB and were placed on ECMO in the operating room and survived. The remaining four patients required ECMO in the ICU and all of them expired. They concluded that early institution of mechanical support is the key to survival in children likely to be placed on ECMO. Contrastingly, Langley et al.[8] reported death in six out of seven patients who could not be weaned from CPB. They suggested the use of intraoperative transesophageal echocardiography to ascertain adequacy of surgical repair before instituting ECMO and recommended its use for not more than 5 days.

In our series, use of integrated ECMO-CPB circuit may have led to a higher survival rate. The decision to put a patient on integrated ECMO-CPB circuit was taken in patients with TGA with IVS with age more than 6 weeks based upon echocardiographic features suggestive of left ventricle regression, i.e., septal motion with right ventricle and crescent or D-shaped left ventricle. The advantages of integrated ECMO-CPB circuit are 1) no time lost from decision to initiation of ECMO; 2) early initiation may prevent end organ damage; and 3) surgical asepsis and cost effectiveness. The early and elective initiation of ECMO without any delay during episodes of low cardiac output may have reduced the end organ damage, probably leading to a better survival in these patients (76%) compared to those patients in whom ECMO was put either in operating room due to inability to wean from CPB or in the postoperative period (25%). Repeated attempts at weaning off conventional CPB using high inotropic support may result in progressive myocardial damage with poor outcome. Integrated ECMO-CPB circuit was not used in children with other correctable CHD, and therefore, our experience is limited for the use of integrated ECMO-CPB circuit in such patients.

A good survival rate was observed when ECMO support was initiated for severe PAH in the operating room (60%). Reactive PAH seen in children with VSD and AVSD requires aggressive intervention in terms of optimization of ventilatory parameters, use of inodilators, supportive pharmacological treatment, inhaled nitric oxide, etc. Decision to put these patients on ECMO support was taken only when all previously mentioned interventions failed. However, ECMO support and a gradual weaning with all other measures to control PAH probably led to a better survival overall. In all these patients, ECMO was initiated in the operating room without any delay. These findings are in tandem with previous reports of survival rates in children with PAH (50-100%) when ECMO support was instituted. [6],[9],[10]

When ECMO support is initiated in the postoperative period for supporting a failing heart due to either cardiac arrest or intractable VF or respiratory cause, survival of only 33% was observed. This decrease in survival is again because of the reason that ECMO is a last resort in the management of a patient in the ICU. By the time ECMO support is initiated, the patient may be in low cardiac output for a prolonged period, with higher chances of myocardial and other organ damage. The time required to assemble, prime and adequately deair the ECMO circuit is around 30-45 min even in the most experienced instititutes. This increases the chances of end organ damage, especially if CPR has been initiated. ECMO as a management strategy is used at some centers for patients undergoing cardiopulmonary resuscitation. [4]

For patients with residual defects after repair of a CHD, ECMO support led to survival in 25% patients. Patients with incomplete repair have a bad prognosis. Black et al.[11] report 100% mortality in this group, similar to Langley et al.[8] In our series, one patient with TOFwas instituted on ECMO in the postoperative period. The patient was diagnosed to have a residual VSD and a right ventricular outflow tract gradient. The patient survived after surgical correction. The other three children with TOF with residual VSD did not survive even after ECMO support. Completeness of surgical repair and reversibility of the heart failure and/ or hypoxemia are prerequisites to institution of ECMO, and adequacy of surgical repair should be documented by intraoperative transesophageal echocardiography.

Infections (sepsis), renal failure and intracranial hemorrhage were the leading causes of mortality, with a significant overlap between infections and renal failure. Mechanical complications were more often observed in the initial years of the ECMO program but were not fatal. With time and experience, there have not been any mechanical complication in the 54 ECMO cases undertaken in the past 5 years. Bleeding as a complication has not been observed in our case series probably because o f intensive hemostasis, a good platelet count control, strict ACT maintenance between 180 and 220 seconds, low threshold for packed red blood cell and platelet transfusion, routine use of aprotinin or epsilon amino caproic acid.

Being a retrospective analysis, the present study is not empowered to provide any randomized comparable groups for statistical analysis. Patients with TGA with IVS with regressed left ventricle were put on integrated ECMO-CPB circuit, whereas for all other CHD, there were no defined criteria for the use of integrated ECMOCPB circuit. However, statistical analysis does prove the inverse relation of duration of ECMO run and probability of survival [Table 3].

In conclusion, ECMO support, if used as integrated ECMO-CPB circuit or if initiated early in the operating room after ascertaining completeness of surgical repair, improves the survival rates. Criteria for use of integrated ECMO-CPB circuit in children with TGA as well as other correctable CHD should be developed to enhance the survival rates. ECMO should be used in the management of children with reactive PAH not responding to other measures. In all scenarios, early institution of ECMO remains a key to survival.

 
   References Top

1.Soeter JR, Mamiya RT, Sprague AY, McNamara JJ. Prolonged extracorporeal oxygenation for cardiorespiratory failure after tetralogy correction. J Thorac Cardiovasc Surg 1973;66:214-8.  Back to cited text no. 1
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2.Tracy TF Jr, Delosh T, Barlett RH. Extracorporeal life support organization 1994. : ASAIO Trans; 1994. p. 1017-9.  Back to cited text no. 2
    
3.Flick RP, Gleich SJ, Hanson AC, Schroeder DR, Sprung J. Pediatric surgical extracorporeal membrane oxygenation- a case series. Signa Vitae 2008;3:18-23.  Back to cited text no. 3
    
4.Kolovos NS, Bratton SL, Moler WF, Bove EL, Ohye RG, Bartlett RH, et al. Outcome of pediatric patients treated with extracorporeal life support after cardiac surgery. Ann Thorac Surg 2003;76:1435-42.  Back to cited text no. 4
    
5.Chauhan S, Pal N, Bisoi AK, Chauhan Y, Venugopal P. The Integrated ECMO-CPB circuit: 'Extending the boundaries of primary arterial switch operation'. Presented at ASA Abstracts, Anesthesiology 2007;107:A212 .  Back to cited text no. 5
    
6.Chaturvedi RR, Macrae D, Brown KL, Schindler M, Smith EC, Davis KB, et al. Cardiac ECMO for biventricular hearts after pediatric open heart surgery. Heart 2004;90:545-51.  Back to cited text no. 6
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7.Ferrazi P, Glauber M, Di Domencio A, Fiochhi R, Mamprim F, Gamba A, et al. Assisted circulation for myocardial recovery after repair of congenital heart disease. Eur J Cardiothorac Surg 1991;5:419-24.  Back to cited text no. 7
    
8.Langley SM, Shepherd SV, Tsang VT, Monro JL, lamb RK. When is extracorporeal support worthwhile following repair of congenital heart disease in children? Eur J Cardiothorac Surg 1998;13:520-5.  Back to cited text no. 8
    
9.Dhillon R, Pearson GA, Firmin PK, Chan KC, Leanage R. Extracorporeal membrane oxygenation and the treatment of critical pulmonary hypertension in congenital heart disease. Eur J Cardiothorac Surg 1995;9:553-6.  Back to cited text no. 9
    
10.Ziomek S, Harrell JE, Fasules JW, Faulkner SC, Chipman CW, Moss M, et al. Extracorporeal membrane oxygenation for for cardiac failure after congenital heart operation. Ann Thorac Surg 1992;54:861-8.  Back to cited text no. 10
    
11.Black MD, Coles JG, Williams WG, Rebeyka IM, Trusler GA, Bohn D, et al. Determinants of successes in pediatric cardiac patients undergoing extracorporeal membrane oxygenation. Ann Thorac Surg 1995;60:133-8.  Back to cited text no. 11
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Correspondence Address:
Madhur Malik
Department of Cardiac Anaesthesia, VII Floor, C N Centre, All India Institute of Medical Sciences, New Delhi - 110 029
India
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DOI: 10.4103/0971-9784.74395

PMID: 21196670

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    Tables

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