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Eur J Cardiothorac Surg 2001;20:811-815
© 2001 Elsevier Science NL

Post-cardiotomy mechanical circulatory support using a conventional bypass circuit in children

Nirav C. Patel, M. Jothi, Dipesh B. Trivedi, Graham Sabino, Paul Daly, Peter D. Booker, Marco Pozzi

Department of Cardiac Surgery, Alder Hey Children's Hospital, Eaton Road, Liverpool L12 2AP, UK

Received 31 January 2001; received in revised form 25 June 2001; accepted 26 June 2001.

Corresponding author. Tel.: +44-151-228-4811, ext. 2715; fax: +44-151-252-5643
e-mail: mpozzi75{at}hotmail.com


   Abstract
Top
 Abstract
1. Introduction
 2. Materials and methods
 3. Results
 4. Comments
 5. Summary
 References
 
Objective: Mechanical circulatory support (MCS) is increasingly used after cardiotomy in children when conventional medical treatment fails. Poor overall survival and long-term outcome have been reported. We report our experience of post-cardiotomy MCS using a conventional bypass circuit. Methods: Over a 4 year and 6 month period 10 patients, with a median age of 16 days (range 5 days to 16 years) required MCS. Eight patients required support for failure to wean from cardiopulmonary bypass during primary correction. Two patients required support for cardiac arrest or poor cardiac output in the postoperative period. Results: The median duration of support was 43 h (range 26–146 h). Seven hospital survivors were alive and well at median follow-up of 18 months (range 4–36 months). One patient could not be weaned off support. Two more patients died after successful weaning from support. Complications in nine patients who could be weaned off support included renal failure (n=6), cerebrovascular events (n=3) and mediastinitis (n=2). Conclusions: Overall long-term survival (70%) and quality of recovery is usually good even though initial mortality and complication rates may be high. We think that post cardiotomy mechanical circulatory bypass using a conventional bypass circuit can offer a favourable outcome to selected patients.

Key Words: Post-cardiotomy mechanical circulatory support • Conventional bypass circuit • Children


   1. Introduction
Top
 Abstract
 1. Introduction
2. Materials and methods
 3. Results
 4. Comments
 5. Summary
 References
 
In 1973 Soeter et al. [1] first reported the use of mechanical circulatory support (MCS) after correction of tetralogy of Fallot. There has been a significant increase in the use of MCS for refractory cardiac failure since then. A number of post-cardiotomy MCS series [2–9] have been reported with varying results. MCS in paediatric patients has been described using an extracorporeal membrane oxygenation (ECMO) circuit [2–9], ventricular assist devices (VAD) [9–11] and intraaortic balloon counter pulsation (IABP) [12–14]. We describe our experience of MCS in ten post-cardiotomy paediatric patients using a conventional cardiopulmonary bypass circuit and roller pump.


   2. Materials and methods
Top
 Abstract
 1. Introduction
 2. Materials and methods
3. Results
 4. Comments
 5. Summary
 References
 
2.1. Patients
Between January 1995 and September 1999, 840 paediatric patients had open-heart surgery for congenital heart conditions at the Royal Liverpool Children's Hospital under the care of one surgeon (Dr M. Pozzi). The overall hospital mortality was 3.21% (n=27). Ten patients (1.19%) needed MCS for refractory cardiac failure. Their medical records were reviewed for age, weight, diagnosis, operation, timing and indication of support, completeness of repair, outcome and follow-up duration (Table 1). The age of the patients ranged from 5 days to 16 years (median age 16 days).


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  		Table 1. Patient characteristicsa

 
2.2. Timing and indication of support
Patients 1–8 required MCS for failure to wean from cardiopulmonary bypass after primary correction. All the patients had failed at least two attempts to wean with optimal blood gases, maximal inotropic support, an adequate period of rest on bypass (1–2 h), and adequate filling pressures. All the patients had intraoperative echocardiography to assess the repair. Repair was incomplete in two patients (patients 5 and 6). In patient 5 there was suprasystemic pulmonary artery (PA) pressure and the patient had a dysplastic mitral valve and left ventricular outflow tract (LVOT) obstruction, so an aortopulmonary window was created and the PA was banded. In patient 6, after an intracardiac repair of Taussig Bing anomaly, the initial echocardiogram showed a good repair and hence the patient was supported for 12 h initially. However, a subsequent echocardiogram showed a significant gradient across the LVOT so it was decided to take down the repair and band the PA. The other six patients had satisfactory surgical repair as demonstrated echocardiographically.

Two patients (9 and 10) required MCS in the postoperative period. Patients 9 and 10 required MCS following a cardiac arrest 7–8 h after surgery.

2.3. MCS technique and circuit
2.3.1. Cannulation
All the patients had veno-arterial cannulation through the operative median sternotomy. Venous drainage was achieved using single, right-angled venous cannula (Polystan, Denmark). Oxygenated blood was returned into the ascending aorta through a Stockert (Stockert, Germany) wire-reinforced aortic cannula.

2.3.2. Circuit and components (Fig. 1)
The bypass circuit consisted of a soft-shell venous reservoir and a cardiotomy reservoir (Dideco D762) with a Dideco D701 (Dideco, Mirandola, Italy) hollow fibre membrane oxygenator in seven patients. A D901 Lilliput hollow fibre membrane oxygenator was used in two patients and a Dideco D705 oxygenator with a hard shell venous reservoir was used in a further two patients. All these oxygenators had an integral heat exchanger, which was used to maintain a core temperature of 35°C. A Stockert–Shiley Roller pump was used in all cases. All patients had two cardiotomy suction catheters placed in the pericardial sac. Two patients had left ventricular venting through a right superior pulmonary vein to decompress the left ventricle (LV). A haemofiltration circuit was added when necessary (Hemocor HPH 1000 Minntech, USA).



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  		Fig. 1. Circuit diagram of the conventional bypass circuit used for mechanical circulatory support.

 
2.3.3. Maintenance
A continuous heparin infusion (10 000 IU/50 ml) was used to maintain the activated clotting time at 250–300 s. Blood transfusions averaging 2–3 units per day were given to the patient as and when necessary in order to maintain a haematocrit of 30–35%. A platelet transfusion averaging 1–2 units per day was given directly to the patient (never into the bypass circuit) if the platelet count fell below 50x109/l. One thousand units of heparin were given whenever a platelet transfusion was given. The blood flow was maintained at 100 ml/kg per min and left atrial pressure was maintained between 5 and 7 mmHg. Blood gas analysis was carried out hourly and gas flow rates were adjusted to maintain a PO2 between 100 and 150 mmHg. The oxygenator was changed only when a significant deterioration in performance was noted (range 37–60 h). All inotropic infusions were switched off during MCS and restarted when weaning was commenced.

2.3.4. Weaning strategies
The decision to wean the patient from MCS was made on the basis of two factors.

  1. Good ventricular function as evidenced by visual inspection of the heart.
  2. Epicardial echocardiography – weaning of patients was gradually carried out over 4–6 h by decreasing flow rates by 10–20% every hour and restarting inotropic drugs at the same time. (Ionotropes are totally discontinued during the period of MCS.) After 1–2 h of inotropic support, an epicardial echocardiogram was performed to assess ventricular function. If this was satisfactory, weaning was continued until the patient was completely off MCS.

After successful weaning, decannulation was performed but purse string sutures were not tied until the patient had remained stable and off support for a few hours.


   3. Results
Top
 Abstract
 1. Introduction
 2. Materials and methods
 3. Results
4. Comments
 5. Summary
 References
 
The median duration of MCS was 43 h (range 26–146 h).

3.1. Weaning from MCS
Nine patients were successfully weaned from MCS. Patient 7 could not be weaned off MCS. This patient, who had repair of anomalous origin of left and right coronaries to the aorta, showed progressive deterioration of LV function while on MCS, so support was discontinued.

3.2. Hospital survival
Of the nine patients who were weaned off MCS, seven were discharged from hospital. Patient 9 showed progressive deterioration in ventricular function 3 days after MCS was weaned off, and died of intractable low cardiac output. Patient 8 died of respiratory failure and pulmonary sepsis 75 days after MCS was weaned off.

3.3. Complications
3.3.1. Renal failure
Six of the nine patients who were weaned off MCS had renal failure (66.6%). All these patients were treated with haemofiltration during MCS when their urine output decreased to <1 ml/kg per h. In these patients peritoneal dialysis was commenced after the MCS was weaned off. Five patients demonstrated complete biochemical and clinical recovery and regained normal renal function. Patient 10, who did not recover renal function, died of progressive low cardiac output.

3.3.2. Neurological complications
Three patients had neurological events. Three of the nine patients who were weaned off MCS had neurological events. Two of them had one episode of seizures each; both the patients had a normal CT scan of the brain and did not have any residual deficit. Patient 8 had multiple haemorrhagic cerebral infarcts; this patient died of respiratory failure and sepsis.

3.3.3. Mediastinitis
Two patients had mediastinitis, which was diagnosed by a positive culture from a mediastinal swab taken during delayed sternal closure. Both patients were treated conservatively with appropriate antibiotics.

3.3.4. Bleeding
One patient required re-exploration for bleeding. In all the other patients bleeding could be easily managed using internal cardiotomy suckers. Blood or packed cell transfusions were given as necessary to maintain the haematocrit between 30 and 35%.

3.4. Follow-up
All the seven hospital survivors were alive at median follow-up of 18 months (range 4–36 months). Echocardiograms at the time of the most recent follow-up showed good ventricular function in all but one patient, who showed moderate ventricular function. Three patients had further operations. Patient 1 needed aortic valve replacement for endocarditis. Patient 5 had a Damus–Kaye–Stansel procedure and a bi-directional cavopulmonary shunt; this patient is now awaiting completion of Fontan. Patient 6, in whom an intracardiac repair of Tausig Bing anomaly was taken down, had an arterial switch procedure performed subsequently.


   4. Comments
Top
 Abstract
 1. Introduction
 2. Materials and methods
 3. Results
 4. Comments
5. Summary
 References
 
The options for the management of children with severe myocardial dysfunction following cardiac surgery who do not respond adequately to drug therapy include induced hypothermia [15], IABP [12–14], ECMO [2–9] and VAD [9–11]. Patients who cannot be weaned off bypass present a particularly difficult problem. We do not have facilities for performing ECMO or VAD in our unit, so our only options are IABP or MCS using a conventional bypass circuit.

Our overall hospital survival of 70% (n=7) for patients requiring MCS is better than that reported from the last Extracorporeal Life Support Organisation (ELSO) registry report [19] and other previously reported ECMO series: survival rates range from 35.4 to 57.5% [2–9]. However, the time of initiation of MCS is an important factor when comparing survival from different reports. Some of the previous series consider that there are two distinct groups of patients requiring post-cardiotomy MCS. The first group, who fail to wean off bypass after primary correction, can be distinguished from the second group, who require MCS later in the postoperative period [3,5–7]. In most series, survival and long-term outcome is very poor for the patients in the first group and ranges from 0 to 25% [3,6,7]. In our experience the survival and long-term outcome in the first group of patients is 75% (6/8). Survival of our second group of patients is 50% (1/2), whereas other series have reported survival rates ranging from 40 to 70% [3,5–7]. Duncan et al. [17] in their report recommended rapid-deployment ECMO as the key to improving results in patients with postoperative cardiac arrest.

Most of the previous reports define weaning from support as survival, whereas we considered hospital discharge as survival, making direct comparison between different reports problematic. The rate of usage of MCS is another important factor in comparing different series. Our MCS usage is 1.19% (10 out of 840), which is comparable to some of the previous reports [6,7] but is lower than others [3,5]. The low incidence of post-cardiotomy MCS usage in our experience can be explained on the basis of our policy of using IABP [14]. In our institution, IABP was used in patients who could sustain cardiac output, but had poor LV function and required very high ionotropic support. The indications for MCS are also important factors for comparing survival. Although Ziomek et al. [5] reported good survival, a high proportion of their patients had ECMO for pulmonary hypertension, whereas we did not have any patients with pulmonary hypertension as the main indication for support. We routinely use inhaled nitric oxide and hyperventilation to treat a pulmonary hypertensive crisis in common with other centres [18].

Some reports [4,7] identify incomplete repair as an important factor for very poor outcome (zero percent long-term survivors). We agree with them and think that optimal correction is fundamental for improving the survival prospects of the patient.

For those patients who could be weaned off MCS, the incidence of renal failure was 66.6% (n=6), a much higher incidence than identified in some other reports [5,9]. We believe that early institution of ultrafiltration before biochemical evidence of renal dysfunction is an important factor in determining the ultimate recovery of renal function.

The incidence of neurological complications (36.3%) in our patients was similar to that reported by Duncan et al. [9]. The last ELSO registry report [16] reported a 10% incidence of seizures but only a 33% survival for that group of patients. In our experience neurological complications were not a major source of morbidity. This was contrary to other reports [6,9], which suggested neurological complications as a major source of morbidity but not of mortality. The higher incidence of cerebral haemorrhage in our patients (18.8%) is probably related to the higher level of anticoagulation needed when using a conventional bypass circuit.

The higher incidence of mediastinitis (20%) in our patients compared to other reports [5,7] is probably due to the requirement for mediastinal cannulation, together with their compromised immunity due to prolonged extracorporeal circulation though all patients had their wound covered with a silastic membrane.

Haemorrhagic complications from surgical sites did not cause a significant problem in our experience. Only one patient required re-exploration for bleeding. Most of the previous studies have reported a very high incidence (20–50%) of bleeding from the mediastinum or cannulation site [7,9,16]. MCS using a conventional circuit enables us to use cardiotomy suction catheters, which makes it easier to cope with bleeding and in the event of suckers getting blocked it is very easy to replace or reposition them.

The potential disadvantage of MCS using a conventional circuit was seen in patients who needed support for a prolonged period. The longer the duration of MCS the higher could be the incidence of haemorrhage, neurological events and infection. Duncan et al. [9] in their report suggested that if the patient on MCS does not show improvement in ventricular function by 48–72 h of support then the likelihood of that patient surviving diminishes significantly. Hence, the benefits of continuing support beyond 72 h other than as a bridge to transplantation are questionable. One advantage of VAD and IABP is that they can be used for prolonged periods, though they are not useful in biventricular failure.

The main disadvantage of MCS using a conventional bypass circuit is that it requires monitoring by clinical perfusionists, rather than the trained nursing staff usually needed for patients requiring ECMO or VAD.


   5. Summary
Top
 Abstract
 1. Introduction
 2. Materials and methods
 3. Results
 4. Comments
 5. Summary
References
 
We believe that in centres where ECMO or LVAD are not available, MCS using a conventional bypass circuit may be a useful alternative. Overall long-term survival (70%) for our patients is higher than that reported in most previous series. Patients who could not be weaned from bypass after primary correction had a survival of 75%(n=6), which is higher than in previous reports [3–7,16].


   Footnotes
 
This study was performed in the Department of Cardiac Surgery at the Alder Hey Children's Hospital, Eaton Road, Liverpool L12 2A, UK.


   References
Top
 Abstract
 1. Introduction
 2. Materials and methods
 3. Results
 4. Comments
 5. Summary
 References
 

  1. Soeter J.R., Mamiya R.T., Sprague A.Y., McNamara J.J. Prolonged extracorporeal oxygenation for cardiorespiratory failure after tetralogy correction. J Thorac Cardiovasc Surg 1973;66:214-218.[Medline]
  2. Dalton H.J., Siewers R.D., Furham B.P. Extracorporeal membrane oxygenation for cardiac rescue in children with severe myocardial dysfunction. Crit Care Med 1993;21:1020-1028.[Medline]
  3. Raithel S.C., Pennington D.G., Boegner E., Fiore A., Weber T.R. Extracorporeal membrane oxygenation in children after cardiac surgery. Circulation 1992;86(Suppl 2):305-310.
  4. Black M.D., Coles J.G., Williams W.G. Determinants of success in pediatric cardiac patients undergoing extracorporeal membrane oxygenation. Ann Thorac Surg 1995;60:133-138.[Abstract/Free Full Text]
  5. Ziomek S., Harrell J.E., Jr, Fasules J.W. Extracorporeal membrane oxygenation for cardiac failure after congenital heart operation. Ann Thorac Surg 1992;54:861-868.[Abstract]
  6. Walters H.L., Hakimi M., Rice M.D., Lyons J.M., Whittlesey G.C., Klein M.D. Pediatric cardiac surgical ECMO: multivariate analysis of risk factors for hospital death. Ann Thorac Surg 1995;60:329-335.[Abstract/Free Full Text]
  7. Langley S.M., Sheppard S.V., Tsang V.T., Monro J.L., Lamb R.K. When is extracorporeal life support worthwhile following repair of congenital heart disease in children?. Eur J Cardiothorac Surg 1998;13:520-525.[Abstract/Free Full Text]
  8. Meliones J.N., Custer J.R., Snedecor S., Moler F.W., O'Rourke P.P., Delius R.E. Extracorporeal life support for cardiac assist in pediatric patients. Review of ELSO registry data. Circulation 1991;84(Suppl III):168-172.[Abstract/Free Full Text]
  9. Duncan B.W., Hraska V., Jonas R.A. Mechanical circulatory support in children with cardiac disease. J Thorac Cardiovasc Surg 1999;117:529-542.[Abstract/Free Full Text]
  10. Karl T.R., Horton S.B., Sano S., Mee R.B.B. Centrifugal pump left heart assist in pediatric cardiac surgery: indications, technique, and results. J Thorac Cardiovasc Surg 1991;102:624-630.[Abstract]
  11. Thuys C.A., Mullaly R.J., Horton S.B. Centrifugal ventricular assist in children under 6 kg. Eur J Cardiothorac Surg 1998;13:130-134.[Abstract/Free Full Text]
  12. Park J.K., Hsu D.T., Gersony W.M. Intraaortic balloon pump management of refractory congestive heart failure in children. Paediatr Cardiol 1993;14:19-22.[Medline]
  13. Christensen D.W., Veasy L.G., McGough E.C. Intra-aortic balloon counterpulsation in children: a review of 29 patients. Crit Care Med 1991;19(Suppl):75.[Medline]
  14. Agyin C.A., Kejriwal N.K., Franks R., Booker P.D., Pozzi M. Intraaortic balloon pumping in children. Ann Thorac Surg 1999;67:1415-1420.[Abstract/Free Full Text]
  15. Moat N.E., Lamb R.I.K., Edwards J.C., Manners J., Keeton B.R., Monro J.L. Induced hypothermia in the management of refractory low cardiac output states following cardiac surgery in infants and children. Eur J Cardiovasc Surg 1992;6:579-585.
  16. Conrad S.A., Rycus P.T. Extracorporeal life support 1997. ASAIO J 1998;44:848-852.[Medline]
  17. Duncan B.W., Ibrahim A.E., Hraska V. Use of rapid-deployment extracorporeal membrane oxygenation for the resuscitation of pediatric patients with heart disease after cardiac arrest. J Thorac Cardiovasc Surg 1998;116:305-311.[Abstract/Free Full Text]
  18. Journois D.J., Pouard P., Mauriat P., Malhere T., Vouhe P., Saffron D. Inhaled nitric oxide as therapy for pulmonary hypertension after operations for congenital defects. J Thorac Cardiovasc Surg 1994;107(4):1129-1135.[Abstract/Free Full Text]
  19. Roy B.J., Rycus P., Conrad S.A., Clark R.H. Changing demographics of neonatal extra-corporeal membrane oxygenation patients reported to the ELSO Registry. J Paediatr 2000;106(6):1334-1338.



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