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Ann Thorac Surg 1998;66:1861-1862
© 1998 The Society of Thoracic Surgeons
a Department of Thoracic and Cardiovascular Surgery, Niigata University School of Medicine, 1-757 Ashahimachi-dori, Niigata City 951-8510, Japan
To the Editor
We read with great interest the article by Rodriguez and associates [1]. We agree that brain monitoring may be of even greater use during cardiopulmonary bypass. We have had experience with a malpositioned superior vena cava (SVC), not only in pediatric patients but also in adult patients. In October 1992, we began using cerebral evoked potentials transcranial Doppler sonography, electroencephalography, and near-infrared spectrophotometry (NIRS) for brain monitoring in selected patients. Immediate repositioning of the SVC cannula led to the recovery of the physiologic indicators of brain dysfunction in 5 patients.
We present here a rare case of a patient who suffered from brain dysfunction not with SVC cannulation, but with dual-stage cannulation. A 71-year-old woman manifesting unstable angina underwent emergency coronary bypass grafting. The operation was scheduled to include grafting of the left thoracic artery to the left anterior descending artery, and saphenous vein grafts to both the first diagonal branch and obtuse marginal branch. Normothermic cardiopulmonary bypass was established after cannulation of the aorta with a 7.0 mm soft-flow cannula (Sarns 3M Health Care, Ann Arbor, MI) and of the right atrium with a 28–38F dual-stage cannula (Sarns 3M Health Care). The NIRS was intraoperatively used for brain monitoring because her brain had not been evaluated preoperatively. The NIRS system that we used was a NIRO-500 (Hamamatsu Photonics Inc, Hamamatsu, Japan), which measured not only cerebral oxygenation but also the relative redox state of cytochrome aa3. After cross-clamping of the aorta and infusion of cold blood cardioplegia, the heart was turned counter-clockwise so we could perform the anastomosis to the obtuse marginal branch. At the beginning of the anastomosis, oxyhemoglobin and deoxyhemoglobin were dissociated and reversed. Moreover, central venous pressure increased from 7 to 29 mm Hg. After the above abnormalities were identified, repositioning of the venous cannula was immediately performed, and the rotation of the heart was decreased because extreme rotation of the heart might cause insufficient venous drainage after twisting or compression of the SVC. However, the abnormalities in both NIRS and central venous pressure could not be completely eliminated. Then, core cooling was started for brain protection. Approximately 30 minutes were spent until the heart was put back in the normal position. The above abnormalities in NIRS continued for a while in spite of normalization of central venous pressure.
The patient lost consciousness after the operation. Watershed infarctions in bilateral occipital and frontal regions were revealed by brain computed tomography 2 days after the operation. She died of brain herniation 5 days after the operation. We emphasize that the SVC obstruction may occur in not only the SVC cannulation but also dual-stage cannulation, and brain monitoring during cardiopulmonary bypass is of greater use for the early detection of brain dysfunction when central venous pressure catheters may not be functional, or even when central venous pressure is normal.
References
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