During the 1990s, cardiologists and surgeons began a quest to identify new, less invasive methods of treating heart disease. Angioplasty and stents were developed. Surgeons began to perform coronary artery bypass through keyhole-sized incisions assisted by thoracoscopic techniques.1,2 Subsequently, robotic surgery was introduced into the cardiac surgery operating room to further reduce surgical incision size. Some surgeons 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 operating off-pump on the beating heart.
All minimally invasive surgical approaches present different potential challenges for anesthesiologists. During cardiac 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 handled in the chest and potentially rendered ischemic during the sewing of vascular anastomoses. Consequently, the off-pump patient can deteriorate acutely requiring resuscitative measures and emergent institution of CPB. Anesthesiologists should never consider off-pump or minimally invasive procedures to be less demanding than those performed on-pump.
MINIMALLY INVASIVE SURGICAL APPROACHES
There are a variety of surgical approaches that are designated as being “minimally invasive.” Many off-pump procedures are done through a fully invasive median sternotomy. So, minimally invasive and off pump are not the same although minimally invasive procedures can be completed off pump. Likewise, minimally invasive procedures (e.g., mitral valve replacement) are performed on CPB with robotic assistance. Consequently, surgeons can perform minimally invasive procedures using CPB, or a procedure can be performed off pump but nonetheless require a full sternotomy incision.
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, and robotic and/or thoracoscopic assistance. Many of these minimally invasive approaches present different challenges to the anesthesiologist.
Off-pump revascularization of the coronary arteries can be completed using minimally invasive approaches or via a full sternotomy.
Off-Pump Coronary Artery Bypass Via Full Sternotomy
When a full sternotomy incision is used for off-pump coronary artery bypass surgery (OPCAB), the beating heart is stabilized using various support devices to permit the completion of multiple coronary bypass grafts. During off-pump bypass surgery, the surgeon occludes 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. Because the beating heart, when operated upon, presents the surgeon with a moving target, there are various stabilization devices (Figure 13–1) commercially available, which relatively immobilize that region ...