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Case Reports  |   May 2003
A Complication of Left Heart Bypass: A Transesophageal Echocardiographic Finding
Author Affiliations & Notes
  • Ken C. Lin, M.D., F.R.C.P.C.
    *
  • Feroze-Ud-Din Mahmood, M.D.
  • *Clinical Fellow in Anesthesia. †Associate Anesthetist.
  • From the Department of Anesthesia and Critical Care, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts.
Article Information
Case Reports
Case Reports   |   May 2003
A Complication of Left Heart Bypass: A Transesophageal Echocardiographic Finding
Anesthesiology 5 2003, Vol.98, 1283-1285. doi:
Anesthesiology 5 2003, Vol.98, 1283-1285. doi:
LEFT heart bypass (LHB) is a commonly used technique in descending thoracic aortic aneurysm surgery. It is used primarily to help reduce the incidence of postoperative paraplegia and paraparesis. Bypass is achieved by cannulation of a pulmonary vein, left atrium, or left ventricle and delivery of the blood via  a centrifugal pump to an aortic site distal to the aneurysm. We describe the intraoperative course and transesophageal findings of inadvertent cannulation of the left pulmonary artery instead of the pulmonary vein in LHB for descending aortic aneurysm surgery.
A 52-yr-old woman was scheduled for descending thoracic aortic aneurysm resection. The patient had been in good health before the aneurysm was discovered on a routine chest radiograph. Cardiac catheterization revealed a large calcified saccular aneurysm distal to the left subclavian artery extending to the proximal descending thoracic aneurysm. There was an anomalous origin of the left internal carotid artery from the right innominate artery. The left vertebral artery was also noted to have a moderate sized ostial lesion. The coronary arteries were normal. Left ventricular systolic function was normal with an ejection fraction of 62%. The left ventricular end-diastolic pressure was 12 mmHg. The aortic and mitral valves were normal.
The patient fasted for 8 h prior to surgery. The patient was admitted to the hospital on the day of surgery. Bilateral intravenous catheters were placed along with a 20-gauge radial arterial catheter in the right arm. An intrathecal catheter was placed in the L3–L4 interspace for cerebrospinal fluid (CSF) drainage and pressure monitoring. Standard American Society of Anesthesiology (ASA) monitors were also applied. Induction was accomplished with fentanyl, thiopental, and pancuronium. A left 35-French double-lumen endobronchial tube was inserted. Inhalational anesthesia was maintained with isoflurane. Central venous pressure monitoring was obtained with a right internal jugular 12-French catheter. A pulmonary artery catheter was not placed due to previously reported latex sensitivity in the patient. A right femoral 20-gauge arterial line was also placed and monitored. A transesophageal echocardiography (TEE) probe was inserted. TEE confirmed that the patient had normal left and right ventricular systolic function and no valvular dysfunction. An intracardiac shunt was ruled out by two-dimensional echo and color Doppler. Intrathecal pressure was measured throughout the procedure with occasional aspiration of CSF fluid from the intrathecal catheter to maintain a pressure less than 10 mmHg.
The patient was positioned in the right lateral position for a left thoracotomy incision, and one-lung ventilation was started after incision. After dissection of the aneurysm and preparation of the left femoral artery and left superior pulmonary vein for cannulation, the patient was anticoagulated. Cannulae were placed in the left femoral artery and the left superior pulmonary vein. Left heart bypass commenced. One minute later, the aorta was cross-clamped and aortotomy was performed. Several minutes later, the blood return to the left atrial cannula was noted to be dark. The perfusionist commented that the left heart bypass flows were exceedingly high. At this point, the patient was tolerating LHB well and was stable hemodynamically, and oxygen saturation measured by pulse oximetry (Spo2) was 100%. Concerns about the adequacy of LHB prompted arterial blood gases to be drawn and the heart to be reexamined with TEE. A right radial arterial blood gas test revealed a pH of 7.42 and partial pressure of oxygen (po2) of 268, and a simultaneous right femoral arterial blood gas was pH 7.35 and po222. TEE reconfirmed that there were no new findings, especially intracardiac shunt. However, the mid-esophageal pulmonary artery split view at 0° demonstrated a new echodense signal in the left pulmonary artery (fig. 1, 2).
Fig. 1. The transesophageal echocardiography (TEE) image of mid-esophageal pulmonary artery split view at 0°. Ao = aorta in cross-section; mPA = main pulmonary artery; rPA = right pulmonary artery. Arrow  indicates echodensity in left pulmonary artery.
Fig. 1. The transesophageal echocardiography (TEE) image of mid-esophageal pulmonary artery split view at 0°. Ao = aorta in cross-section; mPA = main pulmonary artery; rPA = right pulmonary artery. Arrow 
	indicates echodensity in left pulmonary artery.
Fig. 1. The transesophageal echocardiography (TEE) image of mid-esophageal pulmonary artery split view at 0°. Ao = aorta in cross-section; mPA = main pulmonary artery; rPA = right pulmonary artery. Arrow  indicates echodensity in left pulmonary artery.
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Fig. 2. The transesophageal echocardiography (TEE) image of mid-esophageal pulmonary artery split view at 0°. Ao = aorta in cross-section; mPA = main pulmonary artery. Arrow  indicates echodensity in left pulmonary artery.
Fig. 2. The transesophageal echocardiography (TEE) image of mid-esophageal pulmonary artery split view at 0°. Ao = aorta in cross-section; mPA = main pulmonary artery. Arrow 
	indicates echodensity in left pulmonary artery.
Fig. 2. The transesophageal echocardiography (TEE) image of mid-esophageal pulmonary artery split view at 0°. Ao = aorta in cross-section; mPA = main pulmonary artery. Arrow  indicates echodensity in left pulmonary artery.
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Because the surgical repair was already underway, the decision was made to complete the surgery instead of attempting to rectify the problem. Repair was accomplished using a tube graft with closure of the aneurysm sac over the tube graft. Total aortic cross-clamp time was 25 min. After completion of the surgery, the double lumen endobronchial tube was changed to a single lumen endotracheal tube. The patient remained intubated and was transferred to the cardiothoracic intensive care unit in stable condition.
The patient was extubated on the same day of surgery in the intensive care unit. The intrathecal catheter was kept in place and monitored for 3 days. Neurologic exams were normal throughout the hospital course. The patient was discharged to go home on postoperative day 6 without any neurologic sequelae.
Discussion
TEE has been used to assist in the placement of left atrial cannula for LHB using the transseptal puncture method. 1 With the increased use of intraoperative TEE in cardiovascular surgery, considerations should be given for its use in confirming the correct location of the atrial or pulmonary venous cannula prior to commencement of the bypass. Left atrial cannulation could be assessed easily using the mid-esophageal four-chamber or two-chamber views. The left superior pulmonary vein is readily visible on TEE by first obtaining the mid-esophageal four-chamber view and then focusing on the left atrium. Slight withdrawal and turning of the TEE probe to the left should bring out the superior pulmonary vein located superiorly to the left atrial appendage. The left lower pulmonary vein can often be visualized in the same position or with rotation of the imaging plane to 90°.
Aortic cross-clamping results in two major insults to the patient: distal organ ischemia and proximal hypertension. During aortic occlusion, the spinal cord must rely on collateral circulation because the clamp usually compromises normal circulation. The area of the spinal cord at greatest risk is that supplied by the anterior spinal artery. The thoracolumbar region of the anterior spinal artery is supplied primarily by the highly variable arteria radicularis magna. This vessel, also known as the artery of Adamkiewicz, has a highly variable aortic origin from between T5 to L2.
Proximal hypertension is dependent on the location of the clamp with more proximal placement resulting in a more significant increase in systemic blood pressure. This can result in increased myocardial wall stress and possibly subsequent myocardial ischemia. CSF pressure may also increase with proximal hypertension, which could reduce spinal cord perfusion pressures. 2 
Spinal cord injury following aortic cross-clamping can occur as early as 20–25 min. 3 Controversy still exists as to the best approach to preserve spinal cord function in descending aortic aneurysm surgery. Some centers prefer to employ simple aortic cross-clamping with expeditious surgical repair, while others advocate the use of distal perfusion methods. The efficacy of LHB in reducing cord injury has been demonstrated when used as the sole neuroprotective intervention 4 or when used in conjunction with CSF drainage. 5,6 Supporters of left heart bypass suggest that other potential benefits are gained, such as reduction of both renal and cerebral complications. 7 
Complications of cannulation for LHB are relatively infrequent. Assurance of proper bypass and adequate perfusion and oxygenation should be sought prior to aortotomy. In our case, suspicion of a potential problem was raised only after subjective observation of the dark blood in the venous cannula. The determination of Pao2peripherally was helpful in detecting problems in LHB. The use of distal pulse oximetry is probably not useful due to the nonpulsatile nature of bypass in the distal circulation.
Left pulmonary artery cannulation for LHB has been described 8 as an alternative to atrial or pulmonary vein cannulation. The proposed benefits to pulmonary artery cannulation are that it is readily accessible and is a sturdy structure, which allows for stable cannula position to ensure steady flows. Flow rates greater than 3 l/min can typically be achieved. This likely explains the exceedingly good bypass flow rates demonstrated by the patient.
References
Kyo S, Motoyama T, Miyamoto N, Noda H, Dohi Y, Omoto R: Percutaneous introduction of left atrial cannula for left heart bypass: Utility of biplane transesophageal echocardiographic guidance for transseptal puncture. Artif Organs 1992; 16: 386–91Kyo, S Motoyama, T Miyamoto, N Noda, H Dohi, Y Omoto, R
Ergin MA, Galla JD, Lansman SL, Taylor M, Griepp RB: Distal perfusion methods for surgery of the descending aorta. Sem Thorac Cardiovasc Surg 1991; 3: 293–9Ergin, MA Galla, JD Lansman, SL Taylor, M Griepp, RB
Banoub M: Anesthesia for thoracic aortic surgery, Cardiac Anesthesia: Principles and Clinical Practice, 2nd edition. Edited by Estafanous FG, Barash PG, Reves JG: Philadelphia, Lippincott Williams & Wilkins, 2001, pp 823–4.
Coselli JS, LeMaire SA: Left heart bypass reduces paraplegia rates after thoracoabdominal aortic aneurysm repair. Ann Thorac Surg 1999; 67: 1931–4Coselli, JS LeMaire, SA
Safi HJ, Campbell MP, Miller CC III, Iliopoulos DC, Khoynezhad A, Letsou GV, Asimacopoulos PJ: Cerebral spinal fluid drainage and distal aortic perfusion decrease the incidence of neurological deficit: The results of 343 descending and thoracoabdominal aortic aneurysm repairs. Eur J Vasc Endovasc Surg 1997; 14: 1882–24Safi, HJ Campbell, MP Miller, CC Iliopoulos, DC Khoynezhad, A Letsou, GV Asimacopoulos, PJ
Bavaria JE, Woo YJ, Hall RA, Carpenter JP, Gardner TJ: Retrograde cerebral and distal aortic perfusion during ascending and thoracoabdominal aortic operation. Ann Thorac Surg 1995; 60: 345–53Bavaria, JE Woo, YJ Hall, RA Carpenter, JP Gardner, TJ
Borst HG, Jurmann M, Buhner B, Laas J: Risk of replacement of descending aorta with standardized left heart bypass technique. J Thorac Cardiovasc Surg 1994; 107: 126–33Borst, HG Jurmann, M Buhner, B Laas, J
Gianelli S Jr, Conklin EF, Potter RT: Cannulation of the left main pulmonary artery for partial left heart bypass. Ann Thorac Surg 1979; 27: 260–1Gianelli, S Conklin, EF Potter, RT
Fig. 1. The transesophageal echocardiography (TEE) image of mid-esophageal pulmonary artery split view at 0°. Ao = aorta in cross-section; mPA = main pulmonary artery; rPA = right pulmonary artery. Arrow  indicates echodensity in left pulmonary artery.
Fig. 1. The transesophageal echocardiography (TEE) image of mid-esophageal pulmonary artery split view at 0°. Ao = aorta in cross-section; mPA = main pulmonary artery; rPA = right pulmonary artery. Arrow 
	indicates echodensity in left pulmonary artery.
Fig. 1. The transesophageal echocardiography (TEE) image of mid-esophageal pulmonary artery split view at 0°. Ao = aorta in cross-section; mPA = main pulmonary artery; rPA = right pulmonary artery. Arrow  indicates echodensity in left pulmonary artery.
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Fig. 2. The transesophageal echocardiography (TEE) image of mid-esophageal pulmonary artery split view at 0°. Ao = aorta in cross-section; mPA = main pulmonary artery. Arrow  indicates echodensity in left pulmonary artery.
Fig. 2. The transesophageal echocardiography (TEE) image of mid-esophageal pulmonary artery split view at 0°. Ao = aorta in cross-section; mPA = main pulmonary artery. Arrow 
	indicates echodensity in left pulmonary artery.
Fig. 2. The transesophageal echocardiography (TEE) image of mid-esophageal pulmonary artery split view at 0°. Ao = aorta in cross-section; mPA = main pulmonary artery. Arrow  indicates echodensity in left pulmonary artery.
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