Interact CardioVasc Thorac Surg 2005;4:170-172. doi:10.1510/icvts.2004.101980
© 2005 European Association of Cardio-Thoracic Surgery
New ideas - Cardiac general |
Pulmonary artery to distal bypass for surgery on the descending thoracic aorta
Dimitri Kalavrouziotis*,
Roger J.F. Baskett and
John A.P. Sullivan
The Maritime Heart Center, 1796 Summer Street, Room 2269, Halifax, Nova Scotia, Canada B3H 3A7
Received 3 November 2004;
received in revised form 23 February 2005;
accepted 24 February 2005
*Corresponding author: Tel.: +1-(902) 473-3808; fax: +1-(902) 473-4448.
E-mail address: dkalavro{at}dal.ca (D. Kalavrouziotis).
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Abstract
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A variety of extracorporeal techniques have been described in surgery of the descending thoracic and thoracoabdominal aorta. We describe an operative approach involving the cannulation of the pulmonary artery for venous drainage in 12 patients undergoing descending thoracic aortic surgery. In-hospital mortality was 17%; there were no in-hospital deaths for elective cases. There were no cases of post-operative paraplegia. Cannulation of the pulmonary artery is a safe and technically simple means of providing venous drainage during cardiopulmonary bypass in aortic surgery. This is an effective approach to distal perfusion in aortic surgery that is associated with excellent flows and avoids cannulating the left side of the heart.
Key Words: Aortic surgery; Cardiopulmonary bypass; Pulmonary arteries
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1. Introduction
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The optimal strategy for visceral, renal, and spinal cord perfusion in the setting of descending thoracic and thoracoabdominal aortic surgery has yet to be elucidated. Partial left heart bypass and partial cardiopulmonary bypass via the cannulation of the femoral artery and vein are extracorporeal techniques in widespread clinical use [1]. A number of limitations have been described for these approaches. Left heart bypass may be complicated by systemic air embolism; the disadvantages of using the femoral vein include retroperitoneal hemorrhage and suboptimal flows [2].
Although its role as an extracorporeal perfusion technique in cardiothoracic surgery has been previously described for arch reconstruction [3], cannulation of the pulmonary artery (PA) for venous drainage in the setting of surgery on the descending thoracic aorta has not been well described.
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2. Materials and methods
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Between November 1995 and July 1998, 12 consecutive patients underwent repair of the descending thoracic aorta at our institution using partial cardiopulmonary bypass via cannulation of the pulmonary artery for venous drainage. All patient data were collected prospectively using the Maritime Heart Center database [4]. The missing data points in the database are less than 5%. Values are reported as mean±S.D., unless otherwise indicated.
Venous drainage was established by opening the pericardium anterior to the phrenic nerve and placing a 28Fr right-angled cannula into the main pulmonary artery. The perfusion circuit included a Synthesis integrated oxygenator/heat exchanger (Sorin Biomedica, Modena, Italy) creating a partial cardiopulmonary bypass circuit requiring full systemic heparinization (Fig. 1). Arterial outflow was established via cannulation of either the femoral artery or descending thoracic aorta distal to the diseased segment. 6 of 12 patients underwent hypothermic circulatory arrest due to the proximal extent of their disease, with a mean core temperature of 16.3 °C. Emergent repairs were undertaken in 5 patients (42%), including 3 ruptures (Table 1). Eight patients (67%) had lumbar cerebrospinal fluid drainage according to a well-described protocol [5]. Lumbar catheter drainage is standard practice at our institution and is performed whenever technically possible and when patient acuity does not preclude its insertion.
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Fig. 1. Following posterolateral thoracotomy, the main pulmonary artery is exposed anterior to the left phrenic nerve and is cannulated for venous drainage (complete arrow). The left ventricle is shown by the dashed arrow. In this patient, arterial outflow is via the left femoral artery (not shown).
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3. Results
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Pulmonary artery cannulation was successful in all patients, and complications associated with the technique were not observed. Overall in-hospital mortality (including intra-operative mortality) was 17% (2 of 12 patients); there was no mortality for elective cases. Cause of death for one patient was ischemic encephalopathy secondary to protamine reaction requiring cardiopulmonary rescuscitation on the operating table after the repair was completed. For the other, cause of death was hypoxic respiratory failure secondary to the acute respiratory distress syndrome.
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4. Discussion
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Spinal cord, visceral, and renal ischemia remain a devastating complication of thoracic and thoracoabdominal aortic repair. No clear consensus regarding the optimal surgical approach to these patients exists, and no single operative technique has emerged as uniformly superior to others [6]. Mauney and colleagues report excellent results with a clamp-and-sew strategy without the use of any additional adjuncts for spinal cord protection [7]; others advocate some form of distal aortic perfusion during the period of aortic clamping, with many now using partial left-heart bypass or partial cardiopulmonary bypass via cannulation of the femoral vessels [8]. We report our experience with the pulmonary artery as an alternative cannulation site for venous drainage in patients undergoing repair of the descending thoracic aorta. The pulmonary artery provides ease of access, is less fragile than the left atrium and easier to cannulate; flows are less dependent on cannula position than the left atrium. Excellent flows were always established and the technique allows for optimal control of proximal aortic pressure. This is an excellent approach to distal perfusion in aortic surgery that avoids entering the left side of the heart and the need for de-airing which can be difficult due to the limited exposure afforded by a thoracotomy. Cannulation of the pulmonary artery is a safe, effective, and technically simple means of providing venous drainage during cardiopulmonary bypass in these patients.
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Fig. 2. The partial cardiopulmonary bypass circuit with roller pump and oxygenatorheat exchanger is depicted. Venous drainage is provided by a cannula in the main pulmonary artery and arterial outflow is via the femoral artery.
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References
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Abstract
1. Introduction