Asian Cardiovasc Thorac Ann 2006;14:e50-e52
© 2006 Asia Publishing EXchange Ltd
Active Cerebral Perfusion During Carotid Endarterectomy
Kazuhito Imanaka, MD,
Masaaki Kato, MD,
Masanori Ogiwara, MD,
Shunei Kyo, MD
Department of Cardiovascular Surgery, Saitama Medical School, Saitama, Japan
For reprint information contact: Kazuhito Imanaka, MD Tel: 81 49 276 1562 Fax: 81 49 276 2062 Email: imanaka{at}saitama-med.ac.jp, Department of Cardiovascular Surgery, Saitama Medical School, 38 Morohongo, Moroyama-machi, Iruma-gun, Saitama 350-0495, Japan.
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ABSTRACT
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A patient with critical stenoses in the bilateral internal carotid arteries (ICA) required multivessel coronary revascularization. The diameter of the left ICA was far greater than the right, which strongly suggested that the cerebral circulation was highly dependent on the left. During left ICA endarterectomy, active cerebral perfusion of 300 mL·min–1 at 23°C using an extracorporeal circulation was employed through the ICA under repair. Subsequently, coronary bypass was performed on-pump with the heart beating. The postoperative course was very good.
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INTRODUCTION
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Carotid artery endarterectomy is a common practice. However, if bilateral carotid arteries are markedly different in diameter and critical stenoses exist bilaterally, cerebral protection during repair of the dominant side is a serious concern. Our contrivance during simultaneous repair of coronary and carotid artery disease in such a case is reported herein.
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CASE REPORT
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A 64-year-old woman suffered an acute myocardial infarction and lung edema. She had a history of syncope, and magnetic resonance angiography of the cervical vessels revealed more than 90% stenosis of the bilateral internal carotid arteries (ICA) and occlusion of the right vertebral artery (Figure 1
). There was also a 50% stenosis in the left posterior communicating artery. After a few days of intensive treatment, she underwent coronary angiography. Severe triple vessel disease, 50% stenosis in the left main trunk, and cardiac dysfunction was diagnosed. Ejection fraction of the left ventricle was 30%. Because of recurrent angina after these investigations, urgent coronary artery bypass grafting (CABG) and concomitant carotid surgery was indicated. However, the left ICA was far greater in diameter than the right, which strongly suggested that her cerebral circulation was highly dependent on the left ICA. During endarterectomy and patch augmentation of the left ICA, therefore, not passive cerebral perfusion using a shunt tube, but active cerebral perfusion through the left ICA using extracorporeal circulation (ECC) was employed. Following midline sternotomy and harvesting of the left internal thoracic artery, the left ICA was widely dissected 1 cm beyond the hypoglossal nerve. Cannulas were placed in the aorta and the right atrium, and ECC was started right after administration of barbiturate for brain protection. The carotid artery was longitudinally incised and a 14 Fr. cannula was inserted into the distal ICA, and, by a separate pump, arterial blood at 23°C was delivered at a flow rate of 300 mL·min–1. During carotid surgery, low flow normothermic systemic ECC was also maintained to prevent dysrhythmia due to cool venous return. After completion of the carotid procedure, 4 CABG anastomoses were performed under partial ECC and with the heart beating. The patient regained consciousness soon after transfer to the intensive care unit. Postoperative course thereafter was uneventful and she rapidly convalesced without neurological sequelae.
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Figure 1. Preoperative magnetic resonance angiography demonstrated critical stenoses in the bilateral internal carotid arteries (arrows). Note the marked difference in diameters.
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DISCUSSION
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The management of combined coronary and carotid artery disease remains controversial. Various strategies are employed in many centers. However, simultaneous repair may be a consensus recommendation if emergency cardiac surgery is indicated in patients with symptomatic carotid stenoses. During such operations, use of an intraluminal shunt tube, hypothermia under ECC, or its combination are popular methods for cerebral protection. To our knowledge, active cerebral perfusion through the ICA under repair has not been reported previously. We believe that this method is more advantageous.
The flow rate through an intraluminal shunt tube is dependent not on the cerebral oxygen demand but simply on the pressure. However, the relationship between the flow rate and the pressure is based on the assumed pressure difference at both ends of the tube.1 Unless the cerebral perfusion pressure is unacceptably low, the actual flow rate may be much smaller than expected. In addition, a shunt tube itself inevitably causes significant obstruction because its internal diameter is very small. In patients with severe bilateral carotid stenoses as in this case, therefore, even use of a shunt tube is unreliable as its flow rate is unknown and may be too small to perfuse the broad part of the brain. Active blood supply of known flow rate is much more reliable.
During simultaneous repair, some surgeons prefer ECC, hypothermia, and shunting or clamping the ICA.2 There is some concern about the maintenance of cerebral circulation prior to and during the carotid procedure, and strict manipulation of ECC or careful transcranial doppler monitoring appears to be mandatory. Although devastating stroke may not occur frequently, such strategies appear to be suboptimal if ECC is used and the ICA is opened at all. Active cerebral perfusion of known flow rate through the manipulated ICA from the beginning of ECC is a much securer method of cerebral protection. By using a separate roller pump for cerebral perfusion, moreover, cerebral hypothermia can be obtained without systemic cooling. Whilst the cardiopulmonary bypass time is prolonged by approximately 20 minutes, we do not believe that this is a major disadvantage.
Some surgeons prefer off-pump CABG. However, cardiac dysfunction or multivessel revascularization are possible hazards of hemodynamic compromise during off-pump CABG. Especially in patients with concomitant occlusive disease of the coronary and carotid arteries, hemodynamic compromise is undesirable. Even after a carotid procedure, multifocal atherosclerosis may be evident and intracranial lesions may co-exist. Off-pump CABG certainly has many advantages, but we believe that in patients with cardiac dysfunction and multivessel coronary artery disease, the off-pump strategy is not feasible during simultaneous carotid and coronary surgery.
The appropriate flow rate of the active cerebral perfusion is unclear. Cerebral hyperperfusion and the exigent complications of hyperperfusion syndrome and hemorrhage must also be avoided. Based on the classical finding that normal carotid artery flow rate is 133–200 mL·min–1,3 and taking into consideration that the contralateral artery was nearly totally occluded, we determined an appropriate flow rate of 300 mL·min–1 at 23°C. This flow rate is marginally greater than the lower margin of 266 mL·min–1 (133 mL·min–1 x 2) and was hypothesized to avoid either hyper or hypo cerebral perfusion. If necessary, monitoring the actual cerebral perfusion pressure utilizing transcranial doppler, and near-infrared spectroscopy can be useful.4
In conclusion, our strategy yielded a favorable result in a very complicated patient. This method can be a viable option especially when bilateral critical stenoses in markedly asymmetric ICAs are present, and use of extracorporeal circulation is feasible.
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REFERENCES
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- Furui T, Hasuo M. Indwelling double-balloon shunt for carotid endarterectomy. Technical note. J Neurosurg 1984;60:861–3.[Medline]
- Minami K, Fukahara K, Boethig D, Bairaktaris A, Fritzsche D, Koerfer R. Long-term results of simultaneous carotid endarterectomy and myocardial revascularization with cardiopulmonary bypass used for both procedures. J Thorac Cardiovasc Surg 2000;119:764–73.[Abstract/Free Full Text]
- Boysen G. Cerebral hemodynamics in carotid surgery: 10. The effect of endarterectomy on rCBF and internal carotid artery flow. Acta Neurol Scand 1973;49 Suppl:61–8.
- Vernieri F, Tibuzzi F, Pasqualetti P, Rosato N, Passarelli F, Rossini PM, et al. Transcranial Doppler and near-infrared spectroscopy can evaluate the hemodynamic effect of carotid artery occlusion. Stroke 2004;35:64–70.[Abstract/Free Full Text]
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ABSTRACT
INTRODUCTION
