A SYMPHONY OF EFFORT
PAs have always espoused the team approach to medicine, and coronary artery bypass graft surgery (CABG) is more dependent on a team than almost any other specialty operation. How fitting for this Journal, which has represented our profession for 20 years, to look back at what has happened in this type of cardiac surgery over that same period of time.
The coordinated efforts of surgeons, anesthesiologists, PAs, nurses, perfusionists, and technicians in the performance of a cardiac operation has almost no equal.* One observer in our operating suite commented that watching the procedure was like listening to a symphony. I could not disagree.
The movements and interaction seem to occur guided by just a nod or a simple wave of the hand. Each section of this medical orchestra knows the part it plays. Each section is reliant on the others to make the operation flow. The crescendo and decrescendo are not unexpected but are woven into the procedure in a manner that may be appreciated by someone with the surgical disposition to recognize the nuances. Even the unexpected can be adapted into the performance, so that the finale produces rave reviews. Those involved make this happen day after day to the point where some feel that the performance is almost boring. And, indeed, during the critical time of the procedure, boredom is everyone's goal.
To reach that point of simplicity, there is the continued push for education, research, and experience. The rehearsals are done in the lab. The performance is evaluated on an ongoing basis. The outcomes can be appreciated only by a prospective or retrospective comparison to previous results. A look back at cardiac surgery over the past 20 years shows that the artists involved have only continued to improve the medium in which they work.
ANESTHESIA
Anesthesia care has really progressed during this time period. Certainly the introduction of continuous monitoring of arterial and pulmonary artery pressures and oxygen saturation was a great step toward better understanding of physiologic changes under anesthesia and warning signs of trouble. Now, continuous cardiac output monitoring and even continuous monitoring of cerebral function or “awareness levels” are available to allow the anesthesiologist and surgeon to make timely decisions. Probably the best advance in this realm, however, has been the ability to visualize cardiac function utilizing transesophageal echocardiography (TEE) during surgery. At times, the hemodynamic picture painted by the monitoring can be difficult to interpret. Now, cardiac function can be directly visualized and critical decisions made before, during, and after the operation based on what TEE actually sees in relation to the pressures on the monitor. All are now important functions of the anesthesiologist— but, as we know, anesthesia is all about going to sleep and waking up.
Gone are the days of patients waking up a day after surgery and spending the next few days coming out of a narcotic-induced fog. Narcotics are utilized in a conservative manner. The improvements in anesthetic agents now allow a patient to be extubated within 2 hours after surgery. This has shortened ICU stays and limited pulmonary complications. In some instances, patients are kept in post-op heart recovery units for a few hours and then moved right to the floor or to an ICU based on their recovery status. Patients are out of bed sooner and on their way to recovery. Many are home in 4 days! However, this does not happen as a result of anesthesia alone.
CARDIOPULMONARY BYPASS
Cardiac surgery was changed forever when Lillehei and Kirklin first placed patients on cardiopulmonary bypass in the 1950s.1 The bypass machine, referred to as the pump, has certainly evolved. The past 25 years have been devoted to minimizing the effect cardiopulmonary bypass has on patients.
Circuits for the flow of blood have become disposable, and heparin has been bonded with some circuits coated to simulate tissue, which has decreased coagulation risk while also reducing the amount of heparin administered. Filters have been proposed to assist in averting an inflammatory response produced by the bypass. “Mini” circuits decrease the amount of fluid needed to prime the bypass machine and thus avoid significant hemodilution. The idea of “bubbling” oxygen into the blood has been replaced with safer and more efficient membrane oxygenators. Rollerheads once utilized to pump the blood caused significant cellular damage and were a hazard if a clamp was inadvertently placed on the bypass tubing at an inappropriate time. Centrifugal flow now is the standard of care, resulting in less cellular trauma and safer flow. The cannula placed in the atrium and aorta to enable bypass flow has become smaller, has multiple configurations, and provides for more hemodynamic flow. The deep hypothermia (below 30°C) utilized during bypass to preserve organ function had negative as well as positive effects on physiology and has been replaced by more moderate cooling coupled with cold blood cardioplegic arrest of the heart. But while cardiopulmonary bypass remains the standard for safe and efficient cardiac surgery, it is far from perfect, and cardiac surgery continues to improve that technology and even to move away from bypass all together.
After years of successfully utilizing the bypass machine, surgeons continue to press the envelope to perform a procedure that does not require the bypass interface. All the new techniques revolve around two types of procedures. One does not utilize the pump, and bypass grafts are sewn on while the beating of the heart is checked by multiple types of stabilization devices and the anesthesiologist medically manages hemodynamic status. The other uses more minimally invasive techniques of going “on pump” and relies on smaller incisions to gain access to the heart. Whether the new techniques offer a clear benefit to the outcome continues to be debated in the literature. As with all procedures, different surgeons prefer different techniques based on their training, experience, and research. The same can be said of the conduit preference surgeons utilize for bypass grafting.
BYPASS SURGERY
CABG was first accomplished by the harvesting of the greater saphenous vein, reversing its orientation so that blood flow would not be impeded by the venous valves and connecting it to the aorta and the targeted coronary artery. While venous bypass remains part of the armamentarium, multiple arterial conduits are now utilized with the belief that the characteristics of arteries will make them last longer than veins against the dynamics of arterial flow. At the time of the first publication of this Journal, the internal mammary (thoracic) artery (IMA or ITA) was just beginning to be utilized for CABG. It is now the gold standard by which all other bypass conduits are measured. Its longevity has no equal. Sequencing the IMA to more than one coronary vessel is popular, and the utilization of both left and right IMAs is an option in some circumstances. Use of the gastroepiploic artery experienced a brief period of popularity, but the difficulty of harvest and poor early results have placed it in the category of conduit of last resort. Now, after initial less favorable results 30 years ago, the radial artery, under a new harvest protocol, is once again being utilized as a coronary artery bypass conduit. Of course, the harvesting of these conduits is one of many parts of the operation performed by PAs.
PAS IN CARDIAC SURGERY
The utilization of PAs in cardiac surgery has certainly been a standard over the past 20 years and since the profession began. PAs have been pioneers in the development of endoscopic harvesting of the saphenous vein, which is now the standard of care. PAs are leaders in the procurement of the radial artery via the endoscopic route as well. Other technical procedures of first assisting, harvesting the mammary artery, inserting pulmonary artery monitoring and other central lines, inserting arterial lines, inserting intra-aortic balloon pumps, and placing chest tubes are just a few of the expected capabilities of the PA in cardiac surgery. Management of the patient after surgery is also expected of the typical PA in cardiovascular surgery. Moving beyond their roots in primary care, PAs in cardiac surgery have developed significant skills, knowledge, and experience that have made them an intricate part of the cardiac surgery team. The symphony is playing, and PAs have the first chair. JAAPA
* This article is based on the experience of the author and interviews with the following people at Peninsula Regional Medical Center, Salisbury, Maryland: Dr. Michael Buchness, cardiothoracic surgeon, CV Surgical; Dr. Cornworth Dayton-Jones, anesthesiologist, Associated Anesthesiology Practice; Mr. Michael Holton, certified clinical perfusionist, Hospital Clinical Services Group.
Steve Wilson works in the Heart Center of Peninsula Regional Medical Center, Salisbury, Maryland, in cardiac, thoracic, and vascular surgery and is a member of the JAAPA editorial advisory board. He has indicated no relationships to disclose relating to the content of this article.
REFERENCE 1. Stephenson LW. History of cardiac surgery. In: Cohn LH, Edmunds LH Jr. Cardiac Surgery in the Adult. 2nd ed. New York, NY: McGraw-Hill; 2003:3-30.