Aortic Root Aneurysms Cerebral Protection

The axillary cannula (shown above) helps to protect the brain during aortic surgery by providing a forward (antegrade) blood flow.

Because the aortic arch gives rise to the carotid arteries, surgery on the ascending aorta and arch requires meticulous attention to brain protection. Most institutions performing surgery on the thoracic aorta utilize deep hypothermic circulatory arrest (DHCA). This technique involves cooling the patient to temperatures between 14-18°C. The bypass machine is then turned off and blood is completely drained from the patient. DHCA affords the surgeon the ability to work in a bloodless field with adequate brain and body protection for 20-30 minutes.

At NYPH/Columbia, we augment brain protection during reconstruction of the aorta with antegrade cerebral perfusion (ACP). ACP involves sewing a small graft to an artery under the clavicle (axillary artery). This method of connection is significant, since blood flow takes the intended path through the body (antegrade flow) rather than backwards via cannulation of the femoral vessels (retrograde flow). Antegrade flow has been demonstrated to reduce the embolic damage from atherosclerotic debris seen in retrograde cannulation.

The axillary graft is then used to connect the patient to the heart-lung machine. Just before the aortic arch is opened, the innominate artery is clamped and blood flow is reduced through the pump to 10cc/kg/min. Cold blood continuously perfuses the brain during the reconstruction of the arch. The added level of protection enables the surgeon to perform complex reconstructions without the fear of stroke or neurologic damage. The visual protection is obvious. Blood literally pours out of the left carotid artery, confirming an intact communication between the left and right side of the brain. In the event that blood flow appears suboptimal, an additional cannula is placed in the left carotid artery.

In addition to continuous cooling of the brain with metabolically replete blood, this technique diminishes the requirement of profound hypothermia. We now perform most of our reconstructions with only moderate hypothermia (28°C), which greatly reduces the time spent on cardiopulmonary bypass.

To date, we have performed over 100 axillary cannulations for a myriad of indications in aortic reconstruction. We have had no injuries to the axillary vessels or nerves. Additionally, we have had no incidences of permanent stroke or permanent cognitive dysfunction.

We are actively engaged in clinical research to discern the most accurate method to confirm our protection. These methods include cerebral oximetry, transcranial Doppler, and jugular venous pH measurements.