Ann Thorac Surg 2001;72:634-635
© 2001 The Society of Thoracic Surgeons
How to do it
Norwood-type operation with adjustable systemic–pulmonary shunt using hemostatic clip
Manoj Kuduvalli, MCha,
Kenneth E. McLaughlin, MDa,
Dipesh B. Trivedi, MCha,
Marco Pozzi, MDa
a Department of Cardiac Surgery, Royal Liverpool Childrens’ Hospital, Alder Hey, Liverpool, United Kingdom
Accepted for publication March 23, 2001.
Address reprint requests to Dr Pozzi, Department of Cardiac Surgery, Royal Liverpool Childrens’ Hospital, Alder Hey, Liverpool L12 2AP, United Kingdom
e-mail: mpozzi75{at}hotmail.com
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Abstract
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The postoperative course of a patient with hypoplastic left heart syndrome after a first-stage Norwood operation is governed to a large extent by the balance between the systemic and pulmonary circulations. Here we describe a simple and convenient technique for establishing an optimally sized systemic–pulmonary shunt by the application of a hemostatic clip. The method has been used in 6 patients.
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Introduction
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The immediate postoperative course of a neonate with hypoplastic left heart syndrome on whom a first-stage Norwood procedure has been performed depends to a large extent on well-balanced systemic and pulmonary flows. The factors governing this include the pulmonary and systemic vascular resistances and the size of the systemic–pulmonary shunt. Inadequate systemic perfusion leads to metabolic acidosis and end-organ dysfunction along with excessive perfusion of the lungs. On the other hand, inadequate pulmonary flow results in hypoxia and the metabolic and functional consequences thereof.
Methods of manipulating the balance between the systemic and pulmonary circulations have included ventilatory adjustment [1] and pharmacological adjustment of the peripheral and pulmonary vascular resistances [2]. The shunt size has been reduced when it was considered either too large or too small [3]. Here we describe a simple method of reducing the size of the systemic–pulmonary shunt by the application of a hemostatic clip. This technique has been used in 6 patients.
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Technique
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With a few variations, the technique used for the first-stage Norwood operation was as described by Pigott and associates [4] in 1988. It includes resection of the coarcted aortic segment if present, homograft augmentation of the aortic arch and ascending aorta, a pulmonary artery–ascending aorta anastomosis, an atrial septectomy, and a central systemic–pulmonary artery shunt between the neo-aorta and the pulmonary artery bifurcation or a modified right Blalock-Taussig shunt. The aims of the reconstruction are to have unobstructed systemic and coronary flows, an adequate interatrial communication, and an adequate but not excessive pulmonary blood flow.
The size of the systemic–pulmonary shunt is a critical factor in achieving a balanced circulation with optimal pulmonary flow. A 3.5-mm expanded polytetrafluoroethylene shunt was selected in each of the 6 patients in whom the shunt was reduced. Mean body weight of the patients was 3.25 kg (range, 2.67 to 3.8 kg).
Patients were weaned off cardiopulmonary bypass on an inspired oxygen concentration of 100% with inotropic support: dobutamine hydrochloride, 10 µg · kg-1 · min-1, and enoximone, 10 µg · kg-1 · min-1, with epinephrine, 0.1 to 0.5 µg · kg-1 · min-1 added on occasion. The hemodynamic status of the patient was allowed to stabilize for a period after weaning off bypass; and then the inspired oxygen concentration was gradually reduced to 40% to 50%, with the goal of maintaining systemic oxygen saturations of around 75% to 85%.
If the systemic oxygen saturation remained higher than 85% after the inspired oxygen concentration was reduced to 21% and the partial pressure of carbon dioxide (PaCO2) was maintained in the range of 45 to 55 mm Hg by hypoventilation, the shunt was reduced in size from 3.5 mm to approximately 3.0 mm by partially clamping the expanded polytetrafluoroethylene tube with a medium-sized Ligaclip (Ethicon Inc, Somerville, NJ) (Fig 1). This was performed in 2 patients and resulted in major stabilization of hemodynamic status, a drop in the systemic oxygen saturation to 75% to 85%, and improved systemic perfusion with a decrease in inotropic requirement. The favorable effects were confirmed by arterial blood gas analysis. In 4 patients, the shunt was downsized from 3.5 mm to 3.0 mm in the intensive care unit because of signs of excessive pulmonary circulation, systemic underperfusion, and persistent metabolic acidosis. This was done 6 to 72 hours postoperatively. All patients were treated with intravenous administration of heparin sodium postoperatively until they could be placed on a regimen of enteric aspirin. Delayed sternal closure was carried out in all patients after operation once hemodynamic status was stable and inotropic support had been reduced to moderate levels.
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Fig 1. A 3.5-mm expanded polytetrafluoroethylene tube graft partially clamped with a medium-sized Ligaclip (Ethicon Inc, Somerville, NJ).
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Comment
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Achieving satisfactory balance between the pulmonary and systemic circulations after first-stage Norwood procedures remains a difficult task. Schmid and coworkers [5] described a technique in which an adjustable tourniquet is applied around the shunt and later removed at delayed chest closure or during the second-stage procedure.
Our technique of downsizing the shunt by the application of a Ligaclip offers several advantages. Placement of the clip is very simple and quick. Surgical revision of the shunt with prolongation of cardiopulmonary bypass is avoided. Removal of the clip, if necessary, is also easily accomplished. One patient in whom a clip was applied immediately after weaning from cardiopulmonary bypass required removal just before transfer from the operating theater. The clip was taken off with ease, and there was nothing to suggest damage to the expanded polytetrafluoroethylene shunt on observation. (The clips are smooth rather than serrated.) Moreover, the clips can safely be left in place without concern regarding foreign material.
One of the possible disadvantages of this technique is the lack of accuracy in reducing the size of the shunt. However, when carefully placed, the tip of the Ligaclip takes in only a small part of the circumference of the shunt and does not result in overly downsizing it. Should this happen, the clip can be removed easily and another applied correctly. Another theoretical problem is the possibility of the clip slipping off the shunt. However, in our experience, when gently but firmly applied, the clip stays in place unless intentionally removed.
To date, we have seen no thrombogenic complications from clipping the shunts. All of the patients received heparin intravenously in the early postoperative period until they were converted to enteric aspirin. Angiography performed on a child prior to a hemi-Fontan procedure demonstrated clear patency of the clipped Blalock-Taussig shunt. In conclusion, the technique described for establishing an optimally sized systemic–pulmonary shunt to stabilize the immediate postoperative course of patients undergoing the first-stage Norwood procedure for hypoplastic left heart syndrome appears to be safe and convenient. Further evaluation with a larger number of patients is required.
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References
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Jobes D.R., Nicolson S.C., Steven J.M., Miller M., Jacobs M.L., Norwood W.I., Jr Carbon dioxide prevents pulmonary overcirculation in hypoplastic left heart syndrome. Ann Thorac Surg 1992;54:150-151.[Abstract]
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Bando K., Turrentine M.W., Sun K., et al. Surgical management of hypoplastic left heart syndrome. Ann Thorac Surg 1996;62:70-77.[Abstract/Free Full Text]
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Jonas R.A., Lang P., Hansen D., Hickey P., Castaneda A.R. First-stage palliation of hypoplastic left heart syndrome. J Thorac Cardiovasc Surg 1986;92:6-13.[Abstract]
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Pigott J.D., Murphy J.D., Barber G., Norwood W.I. Palliative reconstructive surgery for hypoplastic left heart syndrome. Ann Thorac Surg 1988;45:122-128.[Abstract]
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Schmid F.X., Kampmann C., Kuroczynski W., et al. Adjustable tourniquet to manipulate pulmonary blood flow after Norwood operations. Ann Thorac Surg 1999;68:2306-2309.[Abstract/Free Full Text]
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Abstract
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