Off-Pump Cardiac Surgery: What Do You Mean No Pump Break for the Anesthesiologist?
Biswajit Ghosh MD
Vipin Mehta MBBS, MD, DARCS, FFARCSI
A 68-year-old male is admitted for elective coronary revascularization. Coronary angiography reveals severe three-vessel coronary artery disease. Left ventricular ejection fraction (LVEF) is 45% by echocardiogram. Preoperative chest film reveals a heavily calcified ascending aorta. Past medical history is notable for hypertension (HTN), diabetes mellitus type 2 (DM-2), stroke 3 years prior (no residuum), and a 45 pack-year smoking history prior to quitting 3 years earlier. In addition, he underwent right carotid endarterectomy (CEA) 2 years ago, and his most recent blood tests reveal chronic, moderate renal insufficiency. During your preoperative anesthesia evaluation, he informs you that the surgeon has told him that he plans an off-pump coronary artery bypass (OPCAB) surgery for him. The patient recently read an article about “beating heart surgery” and is terrified about the prospect of undergoing this procedure! He wants to know what benefits he can expect from OPCAB versus standard coronary artery bypass grafting (CABG). He asks, “Doc, am I going to have another stroke while I am asleep?” What do you tell him?
OPCAB is a good option for this patient, especially because his surgeon performs this procedure frequently. The patient’s age, history of a stroke, prior CEA, DM-2, calcified ascending aorta, and history of both HTN and tobacco abuse suggest he is at great risk for perioperative stroke, especially if the diseased aorta is heavily manipulated. Avoiding aortic manipulation and cardiopulmonary bypass (CPB) may minimize the propensity for stroke in this case. The patient should be informed that OPCAB surgery could be associated with less neurologic complications than standard CABG in his case.
OPCAB surgery does not offer any additional protection to the kidneys over conventional bypass. The possibility of blood product transfusion may be less in OPCAB surgery. Time to extubation, intensive care unit (ICU) length of stay, and hospital length of stay may be reduced in OPCAB surgery.
BACKGROUND
The first CABG performed without CPB was reported by Kolessov in 1967.The advancement and standardization of CPB and myocardial
perfusion techniques resulted in a waning interest for this technique during the 1970s. Since the 1990s, there has been a notable resurgence of interest in the OPCAB technique at select centers. Of note, approximately 25% of all CABG in the United States in 2003 was done without CPB.
perfusion techniques resulted in a waning interest for this technique during the 1970s. Since the 1990s, there has been a notable resurgence of interest in the OPCAB technique at select centers. Of note, approximately 25% of all CABG in the United States in 2003 was done without CPB.
WHO QUALIFIES FOR OPCAB?
Selection of OPCAB patients depends on multiple factors: Institutional practice, expertise of the surgeon, number of vessels to be revascularized, site and degree of stenosis, and location of the vessel (i.e., intramyocardial vessels are technically more difficult to graft during OPCAB surgery). Patients who may not be good candidates for OPCAB include those with a cardiothoracic ratio >0.7, vessel diameter <1.5 mm, left main disease, LVEF <35%, acute myocardial infarction with hemodynamic instability, morbid obesity, and severe pulmonary disease. Although these are all relative contraindications, experienced OPCAB surgeons are often not deterred by such risk factor profiles from attempting OPCAB.
SURGICAL TECHNIQUE
The position of the patient varies from supine (standard midline sternotomy and reverse J inferior sternotomy) to supine with right lateral tilt for the left anterior minithoracotomy in the fourth or fifth intercostal space.
The sequence of graft placement is determined in order of increased cardiac displacement, and accordingly, the anterior wall vessels are grafted initially, followed by inferior wall vessels and then lateral wall vessels. The concept behind this is that the increasingly revascularized heart tolerates a greater degree of displacement and the hemodynamic insults associated with this repositioning. Exceptions to this approach exist according to individual anatomy.
Adequate exposure and stabilization of the operative vessel is critical for the success of anastomosis completion. This goal is achieved using retractors, stabilizing devices, stabilizing sutures, and possibly intracoronary shunts. OPCAB equipment varies and may function by compression and/or suction to achieve stabilization. Development of these devices has played a significant role in the progress and safety of OPCAB surgery.
Proximal and distal occlusion of the coronary artery is accomplished by encircling suture or soft, flexible, Silastic string around the vessel. Distal occlusion is not always necessary. Intracoronary shunts are often used to reduce ischemia during this time, and along with a carbon dioxide-containing saline mister-blower, provide better visualization of the anastomosis.
ANESTHETIC MANAGEMENT
Patients should be evaluated thoroughly regarding cardiac status (e.g., number of vessels to be revascularized, site and type of lesion, LVEF, presence
of any significant valvular abnormality). A careful history, physical examination, and review of the diagnostic studies, focusing on the pulmonary, renal, hepatic, and neurologic status, are of paramount importance.
of any significant valvular abnormality). A careful history, physical examination, and review of the diagnostic studies, focusing on the pulmonary, renal, hepatic, and neurologic status, are of paramount importance.
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