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Ann Thorac Surg 2000;70:1730-1733
© 2000 The Society of Thoracic Surgeons

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How to do it

Norwood operation without circulatory arrest: a new surgical technique

^a Division of Cardiovascular Surgery, The Montreal Children’s Hospital, McGill University Health Center, Montreal, Quebec, Canada
^b Division of Anesthesia, The Montreal Children’s Hospital, McGill University Health Center, Montreal, Quebec, Canada

Address reprint requests to Dr Tchervenkov, Division of Cardiovascular Surgery, The Montreal Children’s Hospital, Room C-829, 2300 Tupper St, Montreal, Quebec, Canada, H3H 1P3
e-mail: christo.tchervenkov{at}muhc.mcgill.ca

	Abstract

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Circulatory arrest (CA) is associated with potential neurologic injury. We have developed a new surgical technique to eliminate CA during the Norwood operation. A modified Blalock-Taussig shunt (BTS) was fully constructed before cannulation for cardiopulmonary bypass. The aortic cannula was inserted in the patent ductus arteriosus to allow systemic cold perfusion. When deep hypothermia was reached, the aortic cannula was redirected into the pulmonary artery (PA) confluence. Both cerebral and systemic perfusion were maintained through the right PA and BTS into the innominate artery.

	Introduction

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Deep hypothermic circulatory arrest (CA) has been the standard technique used during the Norwood operation in neonates with hypoplastic left heart syndrome and related lesions, with improving surgical outcomes [1]. However, there is increasing evidence suggesting that CA may be associated with increased incidence of adverse postoperative neurologic deficits [2]. This has stimulated tremendous interest in the area of cerebral protection during CA. Recent evidence suggests that systemic low-flow cardiopulmonary bypass during deep hypothermia may be superior to CA with respect to cerebral protection [3, 4]. We report the use of a new technique that allows the complete elimination of CA during the Norwood operation without compromising surgical exposure.

	Patients and methods

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This new technique was developed in stages in operations on 4 neonates (aged 1 to 11 days) who underwent the Norwood operation at our institution. All 4 children had preoperative echocardiographic diagnosis of hypoplastic left heart syndrome and weighed less than 3200 g. The first neonate had critical aortic stenosis and severely hypoplastic left ventricle, which necessitated a single ventricular repair. After full heparinization, a modified right Blalock-Taussig shunt (BTS) was constructed before cannulation for cardiopulmonary bypass (CPB). By constructing the BTS before cannulation, we were able to significantly reduce the time required for CPB, myocardial ischemia, and CA during the operation. Constructing the BTS before CPB was technically straightforward, and the patient remained hemodynamically stable throughout the case. Encouraged by these findings, we proceeded to use the new technique of retrograde low-flow perfusion (LFP) through the pulmonary artery (PA) confluence into the fully constructed BTS described in the following, and we thus completely avoided CA in the next 3 patients (Table 1).

	Technique

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View larger version (23K): [in this window] [in a new window]   Fig 1. (A) Construction of a modified Blalock-Taussig shunt (BTS) before cannulation for cardiopulmonary bypass. (B) Aortic cannulation of the patent ductus arteriosus (PDA) with proximal snaring to provide systemic perfusion. The BTS is clamped. (C) Aortic cannula redirected into the pulmonary artery (PA) confluence, with the distal PDA snared during deep hypothermia to provide retrograde perfusion through the open BTS to allow antegrade cerebral perfusion. The right and left PAs are clamped.

When deep hypothermia was reached, the RPA was once again controlled by vessel loops around its branches, and the left pulmonary artery was clamped distally. The PDA snare was moved distally, and the aortic cannula was redirected without taking it out into the PA confluence (Fig 1C). The BTS was opened to allow retrograde perfusion. To allow reconstruction of the aortic arch, the proximal innominate, left carotid, and left subclavian arteries were snared with vessel loops, and the upper descending thoracic aorta was clamped well beyond the PDA. Cardioplegic solution was administered to arrest the heart. Cerebral circulation was maintained in antegrade fashion by perfusing retrogradely the RPA and the BTS into the innominate artery. Flow was maintained at 0.3 to 0.4 L · min^-1 · m^-2 while the patient was kept at deep hypothermia. Removal of the clamp from the descending thoracic aorta or the snare from the left carotid artery during LFP resulted in brisk back-bleeding, suggesting significant cerebral and systemic perfusion.

The PDA was transected distally, and all ductal tissue was excised from the aortic arch and the descending thoracic aorta. A standard Norwood-type aortic arch augmentation was then carried out with a pulmonary homograft patch, as described previously [5], while maintaining LFP through the BTS. Atrial septectomy was performed through an incision in the right atrium, in the case of bicaval cannulation, or through the cannulation pursestring after temporarily removing the atrial cannula while maintaining systemic perfusion. Air was then removed from the ascending neoaorta, and the snares in the head vessels were removed. The aortic cannula was quickly transferred to the neoaorta, the shunt was clamped, and the branch PAs were released. The proximal PDA was securely suture ligated. The patient was rewarmed, and normal sinus rhythm quickly returned.

	Comment

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Recent evidence suggests that systemic low-flow CPB at deep hypothermia may provide better cerebral protection than CA [3, 4, 6]. This has resulted in a recent trend to move away from CA for many operations in the neonatal period and in infancy that were traditionally performed under CA. However, reconstruction of the aortic arch, such as during the Norwood operation, is still routinely performed under CA. Some surgeons have maintained regional perfusion to the brain, and to some degree the body, by cannulating the free end of the modified BTS after the construction of the anastomosis to the innominate artery [6, 7]. Their technique significantly reduced, but did not completely eliminate, the use of CA. More recently, Imoto and associates[8] have utilized two cannulas for arterial inflow, one into the open end of the partially constructed modified BTS and the other into the descending thoracic aorta just above the diaphragm, to completely avoid CA in a Norwood operation. This surgical technique is promising; however, cannulation of the descending thoracic aorta may prove to be cumbersome.

Encouraged by the significant cerebral and systemic perfusion in the technique described by Pigula and associates [6], we sought a better way to achieve the same cerebral perfusion without the need to transfer the aortic cannula directly into the BTS, minimizing the risk of air embolization and completely eliminating CA. By constructing the modified BTS before cannulation for CPB alone, we were able to eliminate the need for CA and significantly reduce myocardial ischemia and CPB. Furthermore, this proved to be a more reliable means of shunt construction, because the anastomoses could be probed and assessed, if there were technical concerns, through the open distal main pulmonary artery. Clamping of the RPA for the shunt anastomosis before CPB actually increased hemodynamic stability by reducing the pulmonary runoff. With the shunt fully constructed, we were able to maintain antegrade LFP to the brain through the BTS and innominate artery by placing the aortic cannula into the PA confluence. In doing so, we avoided direct cannulation and potential traumatic injury to the shunt, the innominate artery, or the descending aorta. This technique allowed us to completely eliminate the use of CA in the last 3 patients undergoing the Norwood operation. Not only was cerebral perfusion maintained, as demonstrated by the brisk back-bleeding through left common carotid artery, but there was also a significant amount of bloodflow reaching the lower body. In fact, it was necessary to clamp the upper descending thoracic aorta during the period of LFP to avoid it being flooded by blood returning retrogradely. Additional evidence of improved cerebral and systemic protection with LFP could be seen in the improved clinical outcome in these 4 patients. The postoperative course was remarkable for its lack of hemodynamic instability when compared with previous experience. Oxygen saturation ranged between 78% and 84% in all patients. All patients were weaned off CPB easily; 2 had chest closure in the operating room, and the other 2 were closed at postoperative day 3. Three patients had excellent and 1 had good cardiac contractility during postoperative echocardiography. There was no evidence of neurologic, myocardial, or renal deficiency in any of them postoperatively.

Nevertheless, this new surgical technique should be approached with caution at the present time. A potentially treacherous period is the anastomosis of the shunt to the RPA in a patient with an extremely diminutive ascending aorta. Its distortion or kinking will rapidly compromise coronary perfusion. The higher perfusion pressure associated with RPA clamping, together with the careful placement of the proximal clamp medial to the ascending aorta, as well as its gentle retraction to the left by two traction sutures in its adventitia, would help to prevent such compromise.

The current report demonstrated the ability to completely eliminate CA during the Norwood operation. Although our early observation and other reported literatures that minimized the duration of CA suggested that no compromised surgical outcome was associated with these techniques, their benefits remain to be better defined. Although maintaining cerebral perfusion represents the most important aspect of organ preservation during CA, the adequacy of lower-body perfusion using upper-body inflow remains unknown. In addition, the absolute safe duration of LFP at profound hypothermia and the adequacy of the shunt to maintain perfusion at warmer temperatures are other pertinent questions that need to be further evaluated through experimental and clinical studies. We hope that our technique will further refine the Norwood operation, particularly with regard to cerebral protection, which is crucial to the long-term outcome of patients with hypoplastic left heart syndrome, as well as other lesions requiring aortic arch reconstruction.

	References

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1. Bove E.L. Current status of staged reconstruction for hypoplastic left heart syndrome. Pediatr Cardiol 1998;19:308-315.[Medline]
2. Hickey P.R. Neurologic sequelae associated with deep hypothermic circulatory arrest. Ann Thorac Surg 1998;65:S65-S69.[Abstract/Free Full Text]
3. Bellinger D.C., Jonas R.A., Rappaport L.A., et al. Developmental and neurologic status of children after heart surgery with hypothermic circulatory arrest or low-flow cardiopulmonary bypass. N Engl J Med 1995;332:549-555.[Abstract/Free Full Text]
4. Newburger J.W., Jonas R.A., Wernovsky G., et al. A comparison of the perioperative neurologic effects of hypothermic circulatory arrest versus low flow cardiopulmonary bypass in infant heart surgery. N Engl J Med 1993;329:1057-1064.[Abstract/Free Full Text]
5. Norwood W.I., Kirklin J.K., Sanders S.P. Hypoplastic left heart syndrome. Am J Cardiol 1980;45:87-91.[Medline]
6. Pigula F.A., Siewers R.D., Nemoto E.M. Regional perfusion of the brain during neonatal aortic arch reconstruction. J Thorac Cardiovasc Surg 1999;117:1023-1024.[Free Full Text]
7. Asou T., Kado H., Imoto Y., et al. Selective cerebral perfusion technique during aortic arch repair in neonates. Ann Thorac Surg 1996;61:1546-1548.[Abstract/Free Full Text]
8. Imoto Y., Kado H., Shiokawa Y., et al. Norwood procedure without circulatory arrest. Ann Thorac Surg 1999;68:559-561.[Abstract/Free Full Text]

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Frank A. Pigula
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This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to Personal Folders Download to citation manager Author home page(s): Christo I. Tchervenkov Victor F. Chu Dominique Shum-Tim Permission Requests Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Tchervenkov, C. I. Articles by Reyes, T. U. Search for Related Content PubMed PubMed Citation Articles by Tchervenkov, C. I. Articles by Reyes, T. U. Related Collections Related Article