Ann Thorac Surg 2001;72:1770-1771
© 2001 The Society of Thoracic Surgeons
How to do it
Oxygenator support for partial left-heart bypass
William R. Leach, CCPa,
Thoralf M. Sundt, III, MD*b,
Marc R. Moon, MDb,
the Cardiopulmonary Perfusion Staff,a
a Department of Perfusion Services, Barnes-Jewish Hospital, Washington University School of Medicine, St. Louis, Missouri, USA
b Division of Cardiothoracic Surgery, Washington University School of Medicine, St. Louis, Missouri, USA
Accepted for publication June 26, 2001.
* Address reprint requests to Dr Sundt, Division of Cardiothoracic Surgery, Washington University School of Medicine, Suite 3106 Queeny Tower, One Barnes Hospital Plaza, St. Louis, MO 63110, USA
e-mail: sundtt{at}msnotes.wustl.edu
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Abstract
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Partial left-heart bypass provides circulatory support and distal perfusion for repair of thoracic and thoracoabdominal aortic disease without requiring full anticoagulation. Unfortunately some patients, such as those with significant lung contusion in the setting of trauma or those with severe chronic obstructive pulmonary disease and degenerative aneurysms, do not tolerate single-lung ventilation. We have recently modified our left-heart bypass circuit in selected cases to provide supplementary oxygenation, making this technique more broadly applicable.
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Introduction
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Partial left-heart bypass from the left atrium to the distal aorta or femoral artery has gained widespread popularity because of its simplicity and the option for carrying out the procedure with minimum anticoagulation. It is currently our method of choice for distal support in thoracic and thoracoabdominal aortic aneurysm resection and repair of traumatic pseudoaneurysms. Poor pulmonary function due to advanced parenchymal disease or, in the case of trauma, pulmonary contusion occasionally prohibits its use, however.
We recently modified the circuit for repair of a Crawford extent I thoracoabdominal aneurysm repair in a 55-year-old man with severe chronic obstructive pulmonary disease after a Yacoub root reconstruction and elephant trunk repair of the ascending aorta and arch.
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Technique
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When using partial left-heart bypass, we routinely access the left atrium through the left inferior pulmonary vein using a 32F short right-angled venous return cannula (Baxter Healthcare Corp, Irvine, CA). Arterial return is provided through a metal tip High Flow 6.5-mm Sarnes (Terumo Cardiovascular, Ann Arbor, MI) cannula in the descending thoracic aorta, or through a 24F Fem-Flex femoral cannula (Baxter Healthcare) inserted into an 8 mm Gelsoft Plus Dacron graft (Sulzer-Vascutek, Inchinnan, Renfrewshire, Scotland) sewn to the common femoral artery as a "chimney." Our customary partial left-heart bypass circuit includes a centrifugal pump (Medtronic Bio-Pump Model # BPx-80, Medtronic, Minneapolis, MN) and in-line heat exchanger (Medtronic Biotherm Heat Exchanger Model # A-19-38). A Cell 3000 cell-saver reservoir (Baxter Healthcare) is connected to the circuit with a separate roller pump head for rapid transfusion. When the distal anastomosis is below the renal arteries, we cannulate the visceral vessels with 6F Pruitt Irrigation Occlusion Catheters (Ideas for Medicine, St. Petersburg, FL) and perfuse them with blood through a DLP Multiple Perfusion Set (Medtronic DLP, Grand Rapids, MI) connected to a sidearm controlled with a separate roller pump. We permit passive cooling to a core temperature of 34°C during intercostal and visceral artery reimplantation and routinely insert a spinal drain as has been described previously by other authors [1, 2].
This standard circuit has been modified when indicated by the addition of an oxygenator with an integral heat exchanger in parallel with our usual heat exchanger, as shown in Figure 1. We originally used a Medtronic membrane oxygenator designed for extracorporeal membrane oxygenation (Medtronic Membrane oxygenator model 1-4500-2A), but have more recently used a Carmeda-coated Maxima Plus PRF Hollowfiber Oxygenator (Medtronic). Neither oxygenator requires full anticoagulation. We have routinely administered sufficient heparin to maintain an activated clotting time of 250 to 300 seconds.
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Fig 1. Our standard partial left-heart bypass circuit consists of a centrifugal pump and in-line heat exchanger with a reservoir for rapid transfusion and, when indicated, a sidearm for visceral artery perfusion. This circuit can be modified by the addition of an oxygenator with an intrinsic heat exchanger in parallel. The oxygenator can then be introduced into the circuit if needed.
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During the index case described above the patient’s PaO2 dropped to 49 Torr with single-lung ventilation. After institution of oxygenator support the PaO2 measured in the radial artery rose to 76 Torr. His operation proceeded uneventfully. He was extubated on the first postoperative day and was discharged home on postoperative day 10. As of 12 months postoperatively the patient has no complications. Since this case we have used oxygenator support selectively in the repair of Crawford extent I and II thoracoabdominal aneurysms as well as traumatic aortic transections with similar success. We are not reluctant to add an oxygenator when a patient’s pulmonary function is of particular concern.
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Comment
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The advantages of partial left-heart bypass over full cardiopulmonary bypass for protection of the spinal cord and viscera during repair of conditions of the thoracic and thoracoabdominal aorta have been well summarized by previous authors [1–4], although we recognize that this view is not universally held [5]. Left-heart bypass is a simple technique with which perfusionists and anesthesiologists become quickly familiar. As a consequence it can be instituted rapidly. Only moderate hypothermia is required, thus minimizing rewarming time and, therefore, pump time. We think that this advantage may be particularly important in patients with marginal lung function for whom pump-induced pulmonary injury may be particularly poorly tolerated. The advantages of minimal anticoagulation, a topic of debate in the literature [1, 2, 4], have been significant in our experience.
It is particularly in the case of patients with poor pulmonary function, in whom we think left-heart bypass may have the most to offer, that the procedure may be the most difficult to institute. Patients with degenerative thoracic and thoracoabdominal aneurysm frequently have significant chronic obstructive pulmonary disease and may not tolerate single-lung ventilation. Similarly, multiple trauma patients with aortic injury and severe pulmonary contusions have much to gain by avoiding full systemic anticoagulation, particularly in the presence of a closed-head injury. We believe that the modifications of the standard circuit described here will help make this technique possible in these particularly high-risk patients.
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References
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Coselli J.S., LeMaire S.A. Left heart bypass reduces paraplegia rates after thoracoabdominal aortic aneurysm repair. Ann Thorac Surg 1999;67:1931-1934.[Abstract/Free Full Text]
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Safi H.J., Miller C.C., 3rd Spinal cord protection in descending thoracic and thoracoabdominal aortic repair. Ann Thorac Surg 1999;67:1937-1939.[Abstract/Free Full Text]
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Lawrie G.M., Earle N., DeBakey M.E. Evolution of surgical techniques for aneurysms of the descending thoracic aorta: twenty nine years experience with 659 patients. J Card Surg 1994;9:648-661.[Medline]
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Borst H.G., Jurmann M., Buhner B., Laas J. Risk of replacement of descending aorta with a standardized left heart bypass technique. J Thorac Cardiovasc Surg 1994;107:126-133.[Abstract/Free Full Text]
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Kouchoukos N.T., Rokkas C.K. Hypothermic cardiopulmonary bypass for spinal cord protection: rationale and clinical results. Ann Thorac Surg 1999;67:1940-1942.[Abstract/Free Full Text]
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Abstract
Introduction
