- During the 1990s the increased use of angioplasty and the development of stents for the treatment of coronary artery disease started surgeons on a quest to identify new, less invasive methods of treating heart disease. Surgeons attempted to perform coronary artery bypass through keyhole-sized incisions assisted by thoracoscopic techniques.1,2 Other surgeons attempted to use robotic surgery to reduce surgical incision size. Many more surgeons simply attributed most of the difficulties associated with cardiac surgery to the use of cardiopulmonary bypass (CPB). As such, they continued to operate on patients using a full sternotomy but completed their bypass grafts without the use of CPB—in essence operating on the beating heart.
- All of these surgical innovations presented challenges for anesthesiologists at one time or another. During surgery with CPB the surgical manipulations of the heart do not generally affect the patient's hemodynamics—after all the patient is on bypass. In the course of off-pump procedures, the heart must continue to beat and to supply blood to the tissues even when lifted out of the chest and potentially rendered ischemic during the sewing of vascular anastomoses. Consequently, the off-pump patient can deteriorate acutely requiring resuscitative measures and institution of emergency CPB. Never should off-pump cases be considered easy.
There are numerous surgical approaches that are designated as being "minimally invasive." Many so called minimally invasive off-pump procedures are done through a fully invasive median sternotomy. So, minimally invasive and off pump are not necessarily the same thing. A surgeon can perform a minimally invasive procedure on bypass or a procedure can be performed without using bypass but through a full sternotomy.
For this discussion, minimally invasive implies that the surgeon is using something other than a full sternotomy to access the heart. The heart can be approached using various ministernotomies, thoracotomies, robotic ports, and/or thoracoscopic assistance. Many of these minimally access approaches will present different challenges to the anesthesiologist compared with the "routine" cardiac anesthesia described in Chapter 4.
Off-pump revascularization of the coronary arteries can be done through minimally invasive approaches or through a full sternotomy. When a full sternotomy is used as in off-pump coronary artery bypass surgery (OPCAB), the heart is lifted and manipulated using various support devices to permit the completion of multiple coronary bypass grafts. For the minimally invasive approach, a small thoracotomy is used and only the left internal mammary artery is generally grafted to the left anterior descending artery as in the minimally invasive direct coronary artery bypass (MIDCAB) technique. In either approach during "off-pump" bypass surgery the surgeon will occlude blood flow to the vessel being bypassed both proximally and distally using silastic snares and other occlusive devices. The surgical field is occasionally flooded with carbon dioxide to minimize entrainment of air into the coronary artery during surgical manipulation. Since the beating heart, when operated upon, presents the surgeon with a moving target there are various stabilization devices (Figure 13–1...