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J Thorac Cardiovasc Surg 1999;118:978-979
© 1999 Mosby, Inc.
LETTERS TO THE EDITOR |
Division of Cardiovascular Surgery
Children’s Hospital ofIowa
200 Hawkins Dr
Iowa City, IA 52242-1083
To the Editor:
We read with great interest the discussion of a modified perfusion techniqueduring Norwood reconstruction by Pigula, Siewers, and Nemoto
1 and can offer some modifications that will furtherimprove on this technique. In their report, the authors describe a techniqueto provide regional cerebral perfusion through the distal end of a partiallyconstructed 3.5-mm polytetrafluoroethylene shunt to provide cerebral flowthrough the innominate artery during the "circulatory arrest"period. The authors monitor regional cerebral oxyhemoglobin saturation andrelative cerebral blood volume index and demonstrate that the collateral networkprovides seemingly adequate cerebral blood flow while the arch is being reconstructed.Further supporting the presence of an extensive collateral network, the authorsnote the need for an aortic crossclamp on the distal aorta to prevent thecollateral flow from flooding the operative field.
We have used a similar technique for Norwood-type reconstruction inhypoplastic left heart syndrome and describe some differences in techniquethat offer further benefit. In contrast to Pigula, Siewers, and Nemoto, ourfirst maneuver after a short period of surface cooling (to 34°C), sternotomy,and heparinization is to create the proximal end of a 3.5-mm polytetrafluoroethyleneshunt at the base of the right subclavian artery. This shunt is left longand is cannulated with the arterial inflow cannula (8F, Research Medical,Inc, Salt Lake City, Utah). Cardiopulmonary bypass is then initiated withbicaval venous cannulation and the pulmonary arteries are controlled withsnares. The patient is cooled to 18°C over 20 minutes.
The advantage of this modification in technique is that a large portionof the procedure can then be performed during full cardiopulmonary bypasswhile cooling. Specifically, using the shunt as the arterial inflow leavesthe aortic arch and ductus arteriosus free of cannulas. Consequently, theductus can be ligated and divided, after which the main pulmonary artery canbe divided and the pulmonary artery defect closed with a small polytetrafluoroethylenepatch. Furthermore, the right atrium can then be opened and the atrial septectomyperformed. There is no possibility of ejecting air in cases of aortic atresiadue to the valve atresia and the fact that the main pulmonary artery is divided.By this time, the patient has been nearly completely cooled to 18°C. A"drop in" sucker can be left in the right atrium to keep the fieldclear.
Up to this point, the patient has been maintained on full cardiopulmonarybypass without any myocardial ischemia. Flow can be momentarily interruptedand cardioplegic solution infused through the arterial inflow cannula withthe descending aorta clamped and the subclavian and carotid arteries temporarilyoccluded. Cardiopulmonary bypass is then resumed at 30 to 60 mL/min with thebase of the innominate artery occluded and the distal subclavian and rightcarotid artery snares released. We monitor pressure in the right radial arteryand maintain it at 20 to 30 mm Hg. The arch reconstruction is then completedand, like Pigula, Siewers, and Nemoto, we use a crossclamp on the distal aortato avoid collateral flow from obscuring the operative field.
On completion of the arch reconstruction, the neo-aortic arch is cannulatedwith a second cannula and the arch deaired. Arterial inflow is then transferredto the new cannula and full cardiopulmonary bypass resumed. While the patientis being rewarmed, the distal end of the 3.5-mm shunt is trimmed and an anastomosiscompleted with the right pulmonary artery.
The chief advantage of these modifications is better time efficiencyduring the case. All the portions of the repair outside the aortic arch areperformed during the cooling period with full cardiopulmonary bypass and withoutcardioplegic arrest. Myocardial ischemia and regional cerebral perfusion arelimited to only the period during which the ascending aorta is open. Thisshortened period of systemic "circulatory arrest" augmented withregional cerebral perfusion may provide better cerebral protection than moreconventional techniques.
Although the data presented by Pigula, Siewers, and Nemoto are suggestiveof adequate cerebral protection, we still believe that core cooling to 18°Cis the principal component of our cerebral protection strategy. Further studyis warranted to ascertain the relative merits of regional cerebral perfusionversus hypothermia for cerebral protection during aortic arch reconstructionin the neonate.
12/8/101415
References
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