Interact CardioVasc Thorac Surg 2008;7:146-148. doi:10.1510/icvts.2007.163261
© 2008 European Association of Cardio-Thoracic Surgery
Negative results - Vascular thoracic |
Spinal cord malperfusion caused by using the segmental clamp technique during descending aortic repair for chronic type B aortic dissection
Masashi Kawamura,
Hitoshi Ogino*,
Hiroaki Sasaki,
Hitoshi Matsuda,
Kenji Minatoya,
Hiroshi Tanaka and
Soichiro Kitamura
Department of Cardiovascular Surgery, National Cardiovascular Center, 5-7-1 Fujishirodai, Suita, Osaka, 565-8565, Japan
Received 16 July 2007;
received in revised form 17 September 2007;
accepted 18 September 2007
*Corresponding author. Tel.: +81-6-6833-5012; fax: +81-6-6872-7486.
E-mail address: hogino{at}hsp.ncvc.go.jp (H. Ogino).
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Abstract
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Several effective strategies for spinal cord protection have been advocated in descending and thoracoabdominal aortic repairs. The segmental clamp technique has been known as a useful adjunct to shorten the duration of spinal cord ischemia. However, we experienced two cases of spinal cord malperfusion during segmental aortic clamping in descending aortic repair for chronic type B aortic dissection. In these patients, the intercostal arteries including the Adamkiewicz artery had originated from the false lumen. In one patient, spinal cord ischemia was initially detected as decreased motor-evoked potentials. Transesophageal echocardiography simultaneously revealed blood flow congestion in the false lumen during segmental aortic clamping and spinal cord ischemia had developed due to malperfusion of the intercostal arteries branching from the false lumen. Segmental clamping in patients with aortic dissection may not always be useful for shortening the duration of spinal cord ischemia. Transesophageal echocardiography as well as motor-evoked potentials is a useful modality for obtaining the details of intraoperative blood flow in dissecting lumens and malperfusion of the intercostal arteries related to spinal cord injury.
Key Words: Spinal cord malperfusion; Aortic dissection; Segmental clamp technique
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1. Introduction
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The segmental clamp technique has been reported as a useful adjunct to shorten the duration of spinal cord ischemia in descending and thoracoabdominal aortic repairs [1]. However, we experienced two cases of spinal cord malperfusion during segmental aortic clamping.
1.1. Case 1
An 82-year-old male was diagnosed with chronic type B aortic dissection. Its maximum size was 58 mm in diameter at the level of the proximal descending aorta. Enhanced computed tomography (CT) revealed that the false lumen was not thrombosed and that the primary tear was located at the proximal descending aorta. Magnetic resonance angiography (MRA) revealed that the Adamkiewicz artery had originated from the 11th intercostal artery and the patent intercostal arteries had almost branched from the false lumen. Graft replacement of the entire descending aorta was performed. After establishing a partial cardiopulmonary bypass with a femoro-femoral circuit, the core temperature of the patient was reduced to 32 °C. The proximal aortic clamp was applied immediately distal to the left subclavian artery, and the second aortic clamp was applied at the level of the 6th intercostal space for the proximal aortic anastomosis. During aortic clamping, distal aortic perfusion at a pressure above 60 mmHg was maintained by partial cardiopulmonary bypass. The dissecting aneurysm was incised, and the primary tear with a diameter of 20 mm was detected between the clamped sites. Five minutes after the commencement of the proximal anastomosis, the amplitude of motor-evoked potentials (MEPs) disappeared. The double-barreled distal anastomosis as well as the proximal anastomosis was rapidly completed with the preservation of the 8th intercostal artery. The 3rd and 7th intercostal arteries were additively reattached to the graft because the MEP amplitude was not restored. Further, steroid and naloxone were administrated along with cerebrospinal fluid drainage. During surgery and the three days postoperative period, cerebrospinal fluid pressure was maintained at 10 mmHg or less, while cerebrospinal fluid was drained. However, paraplegia was an eventual complication occurring during the postoperative course.
1.2. Case 2
A 75-year-old female was referred for the treatment of an aneurysm of the descending thoracic aorta. Her CT revealed chronic type B aortic dissection associated with a true aneurysm at the mid descending aorta (Fig. 1a). The false lumen was not completely thrombosed, the primary tear existed in the true aneurysm, and the maximum diameter of the descending aorta was 61 mm. Moreover, the small reentry and three lumens were detected around the phrenic level. MRA revealed that the Adamkiewicz artery had originated from the left 10th intercostal artery that had branched from the false lumen. Under partial cardiopulmonary bypass with a core temperature of 32 °C, she underwent replacement of the entire descending aorta. Segmental clamping was put on the proximal and distal sites to the true aneurysm and this clamped segment included the primary tear. During aortic clamping, distal aortic perfusion pressure was maintained at 60–70 mmHg by partial cardiopulmonary bypass. Thereafter, the amplitude of the MEPs diminished, and transesophageal echocardiography (TEE) revealed blood flow congestion in the false lumen in the part distal to the segmental clamp, from where the intercostal arteries had originated. After the segmental clamps were released, the blood flow in the false lumen and intercostal arteries recovered (Fig. 1b,c). The core temperature of the patient was reduced to 20 °C for spinal cord protection, and the entire descending aorta was replaced with the reconstruction of the 10th, 11th, and 12th intercostal arteries under hypothermia circulatory arrest. The postoperative recovery was uneventful, and paraplegia did not occur.
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Fig. 1. A three-dimensional computed tomography image (a). The aortic dissection extends from the distal arch to just proximal to the superior mesenteric artery. The primary tear is located at the mid descending aorta. The mid descending aorta exhibits an aneurysmal change, and its maximum diameter is 61 mm. The false lumen is not completely thrombosed. Arrows indicate the segmental aortic clamping and the entry sites. A transesophageal echocardiography image (b, c). It shows blood flow congestion in the false lumen and decreased flow in the intercostal arteries originating from the false lumen during segmental aortic clamping (b). After releasing the segmental clamps, the blood flow in the false lumen and intercostal arteries recovered (c). T; true lumen, F; false lumen, ICA; intercostal artery.
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2. Comment
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Spinal cord injury is of a major concern in descending or thoracoabdominal aortic repairs. Various strategies for spinal cord protection have been advocated, such as distal perfusion with left heart bypass [2] or partial cardiopulmonary bypasss [3], preoperative identification of the Adamkiewicz artery and intraoperative monitoring of spinal cord ischemia with MEPs [4], reattachment of the intercostal or lumbar arteries [1, 5], cerebrospinal fluid drainage [6], and epidural cooling [7]. The segmental clamp technique has also been reported as a useful method for preventing spinal cord injury [1]. In Case 2 described above, spinal cord ischemia was initially represented as decreased MEPs. Simultaneously, TEE confirmed the malperfusion of the intercostal arteries due to segmental clamping that was related to spinal ischemia. When aorta was unclamped, antegrade and adequate flow from the heart perfused into the false lumen via the large entry (Fig. 2a). However, in our consideration, with proximal aortic clamping, reversal of the aortic flow via the small reentry from the femoral artery during the partial cardiopulmonary bypass might not be adequate for the false lumen perfusion to prevent from spinal cord ischemia (Fig. 2b). In Case 1, malperfusion of the intercostal arteries arising from the false lumen probably occurred because the clamped segment contained the primary tear. In conclusion, the segmental clamp technique in the surgery for aortic dissection may not always be helpful to shorten the duration of spinal cord ischemia during descending and thoracoabdominal aortic repairs. In particular, we should consider cases in which the intercostal arteries, including the Adamkiewicz artery, branch from the false lumen. TEE as well as MEPs is useful for obtaining the details about the blood flow in both the lumens and malperfusion of the intercostal arteries that may cause spinal cord injury.
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Fig. 2. Flow directions are indicated (arrows), when aorta is unclamped (a). With aortic clamping, the flow directions change as indicated (arrows, b). Dashed lines show the clamping sites. T; true lumen, F; false lumen.
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References
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Abstract
1. Introduction