New “First Assistant” Role for the Anesthesiologist

The anesthesiologist is integral to the success of beating heart CABG. In contrast to CABG procedures that use CPB, beating heart CABG requires the anesthesiologist to proactively maintain stable hemodynamics and rhythm in an environment that changes rapidly because of regional ischemia and cardiac manipulation. The anesthesiologist’s active role during beating heart CABG requires a new level of communication with the surgeon. The surgeon must communicate to the anesthesiologist when the heart is being displaced, when a coronary artery is occluded, and when a shunt has been inserted or removed. Likewise, the anesthesiologist must keep the surgeon informed about the use of inotropes or vasopressors, ST segment or rhythm disturbances, and the patient’s general condition. In no other cardiac procedure has it been more important for the anesthesiologist to continually observe and treat the hemodynamic and rhythm responses to cardiac manipulation and regional ischemia.

“Anesthesia is the critical part of the operation. When we occlude the vessel to perform the anastomosis is when hemodynamic instability occurs and not the moment when you go off pump. You have to cooperate very closely with the anesthesiologist in that respect.” (13)
—F.W. Mohr, M.D.
Surgeon

The use of short-acting anesthetic agents for induction and maintenance allows for earlier emergence from anesthesia and the possibility of earlier extubation. The possibility of earlier extubation is further increased by the reduction in pulmonary complications provided by beating heart CABG. In addition, utilizing IV nonsteroidals for pain management (to reduce the need for narcotics) also helps prevent respiratory depression and leads to a quicker return to normal levels of activity.

“Our protocol for managing these patients is not to use beta-blockers at all. I think that it is detrimental, particularly with elderly patients. Elderly patients have two problems. One is that they have stiff ventricles, and usually they are Type 2 diabetics. For that reason, we like to use milrinone and Levophed® . They are useful drugs because they change the compliance of the ventricle and allow the ventricle to beat when the heart is up. If you give neosynephrine in the elderly population, it is very detrimental.

The other thing we do is give large doses of magnesium preoperatively. Magnesium stimulates prostacyclin and vasodilates the ventricle. We also use insulin very aggressively to keep the sugars under 200 and control acidosis.” (13)

—David Perkowski, M.D.
Surgeon

Induction and Maintenance of Cardioprotective Anesthesia by Arne P. Nierich, M.D.

General Induction
The following is a suggested protocol for general induction: (14)
Propofol 1–2 mg/kg
Pancuronium 0.1 mg/kg
Sufentanil 0.25 mg/kg
Continuation with air/oxygen and propofol 2–3 mg/kg/hr

Heparinization
Maintain ACTs greater than 250 seconds. Less heparin (100–200 units/kg as opposed to the standard 300 units/kg) is required, and protamine reversal is thereby reduced to 2/3 dose (15)

Normothermia
Use the following techniques to keep the patient normothermic:
Warm IV fluids
A heating mattress or warm air under the drape
A humidified airway
A warm OR

Monitoring Hemodynamic Stability
Arterial line and/or CV line
SvO2 — When oxygenation and hemoglobin are constant, SvO2 is a good indicator of hemodynamic performance
EKG — Used to monitor rhythm and analyze ST segment trends
TEE — Used to monitor regional wall motion and status of ventricular volume

Maintaining Hemodynamic Stability
Hemodynamic stability is easily maintained with the use of the simple techniques described below:
Trendelenburg position — Increases preload and allows gravity to assist in supporting the heart in the vertically displaced position

“[T]he Trendelenburg position increases the filling pressure and helps maintain hemodynamic stability. I believe this is an important maneuver for every surgeon to remember who wishes to use [beating heart CABG].” (16)
—Kit V. Arom, M.D.
Surgeon

Table rotation — Minimizes the required cardiac manipulation and aids in exposing the lateral wall
Nitrates — Maximize coronary perfusion
Vasopressors and/or inotropes — Maintain mean arterial pressure