Minimally Invasive Cardiac Surgery

James I. Fann MD¹

Clayton Kaiser MD¹

Lawrence C. Siegel MD²

¹SURGEONS

²ANESTHESIOLOGIST

OFF-PUMP AND MINIMALLY INVASIVE CORONARY ARTERY BYPASS GRAFTING

SURGICAL CONSIDERATIONS

Description: Although coronary artery bypass grafting (CABG) without cardiopulmonary bypass (CPB) was originally proposed more than 6 decades ago, development and advances in CPB resulted in the abandonment of off-pump cardiac surgery by most cardiac centers until the 1990s. The resurgence of off-pump coronary revascularization was due in part to reported adverse effects of CPB, increased comorbidities in an aging population, medical economics, and the development of reliable mechanical stabilization devices (Fig. 6.2-1). From the standpoint of terminology, offpump coronary artery bypass grafting (OPCAB) applies to all cases of coronary revascularization not using the CPB circuit and although it does not refer directly to the surgical approach, most are via conventional median sternotomy. Minimally invasive direct coronary artery bypass grafting (MIDCAB) refers to off-pump coronary revascularization via a small anterolateral thoracotomy incision. Challenges of off-pump coronary revascularization include accurate vascular anastomosis while minimizing hemodynamic perturbations during the procedure. Interrupting flow to the target artery can → regional ischemia, arrhythmias, and hemodynamic instability; displacing the heart to expose lateral or posterior arteries may → ventricular compression and profound hemodynamic compromise. Pharmacologic interventions to decrease HR and ischemic preconditioning may facilitate the anastomosis. Although not fully defined, ischemic preconditioning results from exposure to transient myocardial ischemia and is an endogenous adaptation that may mitigate the effects of subsequent prolonged myocardial ischemia. Thus, mechanically occluding the coronary artery for a brief period may confer some protection from ischemic injury associated with coronary occlusion during the anastomosis. Important preop considerations include the number and suitability of distal-target coronary arteries, cardiac and pulmonary status, and other medical comorbidities. The presence of cardiomegaly may limit the degree of intraop cardiac manipulation. The perfusionist is present during the procedure so that rapid conversion to conventional on-pump CABG can be achieved if there is hemodynamic compromise, unsuitable distal target, inability
to expose lateral or posterior target vessels, or regional myocardial ischemia. Occasionally, placement of intraaortic balloon pump intraop may facilitate the off-pump approach in a patient with ischemic cardiomyopathy.

Figure 6.2-1. Manipulation of the heart and placement of a pressure-plate mechanical stabilizer is performed in preparation for OPCAB. (Reproduced with permission from Estafanous FG, Barash PG, Reves JG: Cardiac Anesthesia: Principles and Clinical Practice, 2nd edition. Lippincott Williams & Wilkins, Philadelphia: 2001.)

Figure 6.2-2. Incision sites for access to various target coronary arteries in MICAB. (Reproduced with permission from Estafanous FG, Barash PG, Reves JG: Cardiac Anesthesia: Principles and Clinical Practice, 2nd edition. Lippincott Williams & Wilkins, Philadelphia: 2001.)

For conventional OPCAB, a standard median sternotomy is made (Fig. 6.2-2). If the internal mammary artery (IMA) is to be used as a graft, it is harvested in the usual fashion. The patient is partially heparinized, and an intravenous bolus of lidocaine is given. A sternal retractor with attachments for coronary stabilization is placed (Fig. 6.2-1). If vein grafts are used, the proximal anastomoses may be performed at this point or later, after the completion of the distal anastomoses, using a partial side-biting aortic cross-clamp or automated anastomotic device. During the period of partial aortic clamping, BP typically is lowered to reduce potential complications associated with the use of the clamp. The goal of the operation is to establish adequate perfusion of the most critical vascular bed first. Provided it is a target vessel, the LAD artery is often approached first because an IMA graft (or vein graft) can provide immediate perfusion and requires minimal cardiac manipulation to construct the anastomosis. Mechanical coronary artery stabilizers, based on local myocardial compression (Fig. 6.2-1) or vacuum suction (Fig. 6.2-3) and attached to the retractor, provide stable local epicardial motion restraint, thereby facilitating the anastomosis. After stabilization, the artery is occluded (following a period of ischemic preconditioning), and an arteriotomy is made. Equipment that minimizes blood in the operative site includes standard suction attachments, temporary intracoronary shunts, vessel occluders, and “blower-misters” that displace blood by delivering a combination of gas (CO2) and heparinized saline. The distal anastomosis is then performed. The patient is monitored closely at this point for any signs of myocardial ischemia and/or hemodynamic instability. To expose the lateral and posterior target vessels, manipulation of the heart is necessary and may not be well tolerated. During lateral and posterior pericardial suture placement, the surgeon displaces and compresses the heart, resulting in temporary hemodynamic compromise. Ventilation may need to be decreased temporarily to facilitate this maneuver. Additional exposure techniques include the use of an apical suction device to facilitate cardiac manipulation with potentially less hemodynamic compromise, Trendelenburg position and tilting the operating table to the right, release of right pericardial stay sutures, opening of the right pleura, and incising the right pericardium, and placement of laparotomy sponges. The target vessel is stabilized again, ischemic preconditioning is carried out, and the artery is opened. After construction of the distal anastomosis, the graft is relieved of any residual air before securing the sutures and the proximal anastomosis performed if not already done so as noted earlier. Graft flow is assessed using a Doppler flow probe.

Figure 6.2-3. The Octopus stabilizer (Medtronic, Minneapolis MN) uses a series of suction cups on two fixed arms that adhere to the epicardial surface and reduce myocardial motion at the anastomotic site during OPCAB. (Reproduced with permission from Estafanous FG, Barash PG, Reves JG: Cardiac Anesthesia: Principles and Clinical Practice, 2nd edition. Lippincott Williams & Wilkins, Philadelphia: 2001.)

▪ SUMMARY OF PROCEDURE

Position	Supine (Fig. 6.2-4)
Incision	Median sternotomy (OPCAB); alternatively, limited left anterolateral thoracotomy (MIDCAB; Fig. 6.2-2)
Antibiotics	Cefazolin 1 g iv
Surgical time	3-4 h
Closing considerations	No special considerations. Patients often can be extubated in OR.
EBL	200-400 mL (consider using Cell-Saver)
Postop care	ICU for cardiac monitoring ± ventilator management; less volume required than with conventional CABG.
Mortality	0-5% (higher with increasing age)
Morbidity	AF: 10-30% Pulmonary insufficiency: 3-5% Reoperation for bleeding: 1-4% Cardiac (e.g., myocardial infarction): 0-4% Mediastinal infection: 1-2% Neurologic (cerebrovascular accident): 1-2% Renal dysfunction: 1-2% IABP use: 0-2%
Pain score	4-6

Figure 6.2-4. OR configuration for MICAB. (Reproduced with permission from Estafanous FG, Barash PG, Reves JG: Cardiac Anesthesia: Principles and Clinical Practice, 2nd edition. Lippincott Williams & Wilkins, Philadelphia: 2001.)

ANESTHETIC CONSIDERATIONS FOR MICAB/OPCAB

PREOPERATIVE

Preop assessment is similar to that used for standard CABG patients (see p. 356). Relative contraindications for MICAB include low EF, morbid obesity, previous cardiac surgery, AF, and COPD. It is important to know the coronary artery anatomy and the planned surgical procedure and sequence. For example, proximal surgical occlusion of a coronary artery with high-grade distal disease may be poorly tolerated as compared with severe proximal disease with collateralization.

Premedication

Adequate control of preop anxiety using midazolam (titrated to effect) may reduce periop tachycardia.

INTRAOPERATIVE

Anesthetic technique: GETA. For MICAB, selective lung ventilation with DLT, Univent ETT, or bronchial blocker. Unlike CABG on CPB, the anesthetic demands for OPCABG are somewhat different, as CPB will not be providing hemodynamic support. Positioning of the heart for access to the target vessel, as well as mechanical stabilization of the heart to immobilize the vessel for accurate anastomosis tend to produce hemodynamic compromise. In particular, elevation of the LV apex to allow access to lateral and posterior wall vessels can limit LV filling and obstruct RV outflow tract. In addition, ↓ TV may be necessary to prevent obstruction of visualization. Snares may be placed around the coronary target vessel to create a dry operative field; however, this may provoke regional ischemia. Many of these changes are assessed by intraop TEE, and they may require resuscitative measures with volume
loading, vasoconstriction, and inotropic support (e.g., dopamine). Interventions on the RCA are particularly prone to arrhythmias, and appropriate antiarrhythmics and pacing should be available. For further discussion, see Intraoperative considerations for CABG, p. 357.

Induction	As for CABG surgery (see p. 357). For MICAB, these patients will undergo a small anterior thoracotomy, and the aim is to extubate them at the end of the procedure or shortly thereafter. Thus, the dose of narcotic should be moderate (e.g., fentanyl 5-15 mcg/kg). Longacting muscle relaxants should be avoided for the same reason. Consider spinal narcotics (e.g., morphine 0.3-0.5 mg).
Maintenance	Because early extubation is planned, volatile agents or propofol should be used and the overall dose of narcotic reduced. Remifentanil infusion may also be useful.
Emergence	For further discussion, see Postoperative Considerations for CABG, p. 359. If the patient is not suitable for extubation in the OR, a DLT may be exchanged for a conventional ETT (over a tube changer) before transport to ICU.
Blood and fluid requirements	See CABG surgery (p. 354).	Without the use of CPB, hemodilution from the pump prime is avoided.
Monitoring	See CABG surgery (p. 354). TEE	Central venous access. PA catheters are useful for detecting ischemia in patients with poor LV function. If a continuous CO thermodilution catheter is used, consideration must be given to the large delays in data display. ST segment analysis. Useful for detecting ischemia and LV dysfunction. Views may be limited by surgical positioning of the heart within the chest.
Special considerations	Anticoagulation Ischemic preconditioning Temporary occlusion → ischemia [check mark] ECG, TEE. Cardiac positioning →↓ CO Coronary artery shunt	Heparin should be administered before surgical coronary artery occlusion. Prior to occlusion, ischemic preconditioning may be accomplished with surgical manipulation and by pharmacologic means (e.g., isoflurane, sevoflurane). This is a great opportunity to consider how well transient ischemia is tolerated. During grafting, the vessel is temporarily occluded to avoid flooding the field with blood. The myocardium distal to this may become ischemic. TEE imaging will be affected by surgical mechanical manipulation of the heart, and ECG voltage may be decreased. Cardiac output may be markedly reduced by the combination of heart positioning and coronary artery occlusion. Vasoconstriction may be required to maintain adequate blood pressure. Patients poorly responsive to vasoconstrictors may have extremely depressed cardiac output and severe acidosis. Inotropic support or intraaortic balloon pumping may be necessary. Surgical placement of a coronary artery shunt may be necessary. Treatment of rhythm disorders with pharmacologic agents, pacing, or defibrillation may be required. The capability to institute CPB rapidly should exist. A rest period with the heart returned to the normal position within the chest should be considered following each anastomosis to restore cardiac output and permit resolution of acidosis.
Positioning	[check mark] and pad pressure points [check mark] eyes

POSTOPERATIVE

Complications

See CABG surgery (p. 359).

Premature extubation

Pain management

Same as CABG surgery (p. 359).

Intrathecal narcotics or intercostal blocks (MICAB) placed at the end of surgery may aid in early extubation.

Tests

See CABG surgery (p. 359).

Suggested Readings

1. Caputo M, Alwair H, Rogers CA, et al: Thoracic epidural anesthesia improves early outcomes in patients undergoing off-pump coronary artery bypass surgery: a prospective, randomized, controlled trial. Anesthesiology 2011; 114(2):380-90.

2. Dorsa AG, Rossi AI, Thierer J, et al: Immediate extubation after off-pump coronary artery bypass graft surgery in 1,196 consecutive patients: feasibility, safety and predictors of when not to attempt it. J Cardiothorac Vasc Anesth 2011; 25(3):431-6.

3. Halkos ME, Puskas JD: Teaching off-pump coronary artery bypass surgery. Semin Thorac Cardiovasc Surg 2009; 21:224-8.

4. Hemmerling TM, Romano G, Terrasini N, Noiseux N: Anesthesia for off-pump coronary artery bypass surgery. Ann Card Anaesth 2013; 16(1):28-39.

5. Huffmyer J, Raphael J: The current status of off-pump coronary bypass surgery. Curr Opin Anaesthesiol 2011; 24(1):64-9.

6. Lamy A, Devereaux PJ, Prabhakaran D, et al: Effects of off-pump and on-pump coronary-artery bypass grafting at 1 year. N Engl J Med 2013; 368(13):1179-88.

7. Puskas JD, Kilgo PD, Kutner M, et al: Off-pump techniques disproportionately benefit women and narrow the gender disparity in outcomes after coronary artery bypass surgery. Circulation 2007; 116 (Suppl):I-192-9.

8. Raja SG, Berg GA: Impact of off-pump coronary artery bypass surgery on systemic inflammation: current best available evidence. J Card Surg 2007; 22:445-55.

9. Rajakaruna C, Rogers C, Pike K, et al: Superior haemodynamic stability during off-pump coronary surgery with thoracic epidural anaesthesia: results from a prospective randomized controlled trial. Interact Cardiovasc Thorac Surg 2013; 16(5):602-7.

10. Roosens C, Heerman J, De Somer F, et al: Effects of off-pump coronary surgery on the mechanics of the respiratory system, lung, and chest wall: comparison with extracorporeal circulation. Crit Care Med 2002; 30:2430-7.

11. Shroyer AL, Grover FL, Hattler B, et al: Veterans affairs randomized on/off bypass (ROOBY) study group. On-pump versus off-pump coronary-artery bypass surgery. N Engl J Med 2009; 361(19):1827-37.

12. Sisilio E, Marino MR, Juliano G, et al: Comparison of on pump and off pump coronary surgery: risk factors for neurological outcome. Eur J Cardiothorac Surg 2007; 31:1076-80.

13. Straka Z, Brucek P, Vanek T, et al: Routine immediate extubation for off-pump coronary artery bypass grafting without thoracic epidural analgesia. Ann Thorac Surg 2002; 74:1544-7.

14. Virmani S, Tempe DK: Anaesthesia for off-pump coronary artery surgery. Ann Card Anaesth 2007; 10(1):65-71.

PORT-ACCESS CORONARY REVASCULARIZATION

SURGICAL CONSIDERATIONS

Description: Advances in videoscopic technology have led to less-invasive approaches in the treatment of many general and thoracic surgical disorders. The development of less-invasive surgery has resulted in alternative and novel approaches to cardiac surgery, including port-access cardiac surgery and off-pump coronary revascularization. The port-access approach was developed in the mid-1990s and is used less frequently in the current setting because of its complexity. With the development of robotic (or total endoscopic) techniques, the port-access technology is being employed as a means to achieve cardiopulmonary bypass and cardioplegic arrest. Using a port-access approach, the surgeon can perform cardiac operations (e.g., CABG) and valve surgery in a motionless, bloodless field through smaller chest incisions. This approach typically relies on peripheral CPB (femoral artery and femoral vein cannulation, Fig. 6.2-6). The femoral artery is cannulated with a 19-23 Fr Y-shaped cannula, which permits arterial inflow and insertion of the endoaortic clamp. Venous drainage is provided by the 22-25 Fr cannula, introduced through a femoral vein. Drainage may be augmented by 20-40%, using vacuum-assisted venous drainage or a centrifugal venous drainage pump placed between the venous cannula and the reservoir. The port-access system includes a 10.5 Fr endoaortic “clamp” (EAC), a triple-lumen catheter with an inflatable balloon at its distal end. This clamp is positioned in the ascending aorta using fluoroscopy and TEE guidance. The lumen used for balloon inflation is connected to a manometer to monitor balloon pressure. Cardioplegic solution is delivered through a central lumen, which also acts as an aortic root vent after cardioplegia delivery. A third lumen serves as an aortic root pressure monitor.

In addition, a percutaneous PA venting catheter, placed via the jugular approach, helps in ventricular decompression. The left internal mammary artery (IMA) is harvested under direct vision (Fig. 6.2-7

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