Reply to the editor

Abstract

We thank Dr Maurizio Salati for his comments on cannulation of the distal axillary artery in descending thoracic aortic surgery using the open proximal aortic anastomosis technique under deep hypothermic circulatory arrest. Actually, since 2001, we also have used a similar technique for more than 100 patients having various types of descending thoracic and thoracoabdominal aortic lesions requiring an open proximal aortic anastomosis around the aortic arch. In our technique, a 10F to 16F thin-walled cannula is directly cannulated into the distal part of the left axillary artery with additional cannulation of the femoral artery. Venous drainage is performed through the right atrium via the femoral vein and main pulmonary artery. Cardiopulmonary bypass is initiated with core cooling to profound hypothermia at approximately 18°C. The flow rate of left axillary artery perfusion is maintained in the range of 1000 to 1500 mL/min to prevent a potential risk of retrograde cerebral emboli caused by the femoral artery perfusion. In patients with aortic valve regurgitation, this technique is not indicated for those with more than moderate aortic valve regurgitation. With mild aortic regurgitation, another venting tube is inserted into the left ventricle via the left upper pulmonary vein or the apex of the left ventricle to avoid overdistension of the left ventricle caused by ventricular fibrillation during core cooling. At 18°C of the nasopharyngeal temperature, the patient is placed in a head-down position and the central venous pressure is elevated to approximately 15 mm Hg. After cardiac arrest is obtained by administering potassium of 20 to 40 mEq in the pump circuit, profound hypothermic circulatory arrest is induced. Perfusion of the lower body via the femoral artery at a flow rate of 1 to 2 L/min is resumed with the midportion of the descending aorta clamped.1Takamoto S. Matsuda T. Harada M. Miyata S. Shimamura Y. Simple hypothermic retrograde cerebral perfusion during aortic arch replacement. A preliminary report on two successful cases.J Thorac Cardiovasc Surg. 1992; 104: 1106-1109PubMed Google Scholar Partial antegrade cerebral perfusion via the left axillary artery at a low flow rate of 100 to 200 mL/min is also commenced by clamping the proximal site of the left subclavian artery. Then, an open proximal aortic anastomosis is performed using a 1-branched woven Dacron graft. If necessary, the left subclavian artery is reconstructed. During the open proximal aortic anastomosis, debris and air are flushed out from the arch vessels, predominantly by the left axillary artery perfusion. After completion of the proximal anastomosis, perfusion of the heart and brain is resumed using a side-branch graft and the patient is rewarmed to approximately 25°C. The distal anastomosis is performed in the open aortic technique at approximately 25°C. After the anastomosis, full rewarming is started. The outcome has been favorable with low incidences of cerebral and spinal complications because of the beneficial effects of left axillary artery perfusion, as Dr Salati suggested. In addition, another potential benefit of this perfusion is that the downstream flow via the left axillary artery competes against the retrograde flow via the femoral artery perfusion, which can prevent retrograde cerebral emboli even after the heart falls into ventricular fibrillation because of core cooling. With the use of left axillary artery perfusion, however, we have to pay attention to the flow rate of the left axillary artery during the open proximal anastomosis. Too much flow may produce hyperperfusion of the part of the brain perfused via the left vertebral artery. Dr Salati also reduced the flow rate to 10 mL/kg after clamping the left subclavian artery. We concur with him. We use a relatively lower flow of 100 to 200 mL/min. Even with such a lower flow rate, sufficient back flow from the arch vessels is obtained. Further investigation of the appropriate flow rate of the left axillary artery perfusion is required. In the meantime, as Dr Salati pointed out at the beginning, the axillary artery is generally fragile, whether on the proximal or distal part. Then, careful cannulation using a soft cannula of adequate size is necessary. If not, artery injury, including dissection, may occur. From this point of view, the side-graft technique is preferred by the majority when using the axillary artery. However, this side-graft technique is more time-consuming and technically demanding. Bleeding from the anastomosis during the systemic perfusion at a higher flow rate can become a nuisance. Even with this side-graft technique, the word is that arterial dissection occurs from a practical standpoint. We therefore prefer simple and easy direct cannulation into the distal axillary artery. Finally, we also advocate that distal axillary artery perfusion is useful for brain protection in arch to descending thoracic aortic surgery in the lateral approach and the median approach.