Because the aortic arch gives rise to the carotid arteries (the blood vessels supplying the brain), surgery on the aorta requires careful attention to brain protection. Many institutions still utilize deep hypothermic circulatory arrest (DHCA) when performing surgery on the thoracic aorta. This technique involves cooling the patient to temperatures between 14-18°C. At this low temperature, the bypass (heart-lung) machine can be safely turned off and the blood drained from the patient. DHCA thereby affords the surgeon the ability to work in a bloodless field with adequate brain and body protection for approximately 30 minutes.
NYP/Columbia is actively engaged in clinical research to discern the most accurate method to confirm adequate protection of the brain during surgery. Based on our research and experience to date, we augment brain protection during reconstruction of the aorta with antegrade cerebral perfusion (ACP). ACP involves sewing a small graft to an axillary artery under the collarbone (clavicle). This method of connection is significant, since it allows the blood flow to take the natural (forward) path through the body (antegrade flow). Traditionally, patients undergoing aortic surgery have received reverse or retrograde blood flow (via cannulation of the femoral vessels) while on bypass. Antegrade flow has been demonstrated to reduce the risk of an embolism (plaque or blood clot) blocking an artery.
The axillary graft is used to connect the patient to the heart-lung machine. Just before the aortic arch is opened, the innominate (brachiocephalic) artery is clamped and blood flow through the heart-lung machine is reduced. However, cold blood continuously perfuses the brain throughout the process of reconstructing of the arch. This added level of protection enables the surgeon to perform complex reconstructions without the fear of stroke or neurologic damage associated with an embolism.
By continuously cooling of the brain with metabolically replete (rich) blood, this technique also diminishes the requirement for profound hypothermia. We now perform most of our reconstructions with only moderate hypothermia (28°C), thereby greatly reducing the time spent on bypass.
To date, we have performed over 500 axillary cannulations for a range of aortic surgeries. We have had no injuries to the axillary vessels or nerves. Additionally, our stroke rate for all aortic surgery approaches one percent, dramatically lower than the 8-10% reported in the literature.