operation has a long bypass run for a single vessel CABG. It maximizes the risk of stroke while eliminating the sternotomy. This operation was doomed to failure from the start.
CTS (Chuck Taylor Surgical or Cardio Thoracic Surgical) and US Surgical worked to improve the technique popularized by Bennetti. It was in essence a mini-thoracotomy with no bypass. The standard was a single IMA to the LAD. The heart was stabilized by placing latex sutures under the LAD proximal and distal to the site of the anastamosis. A small foot presses on the myocardium while the sutures pull the heart into the foot. Blood flow was stopped in the target vessel by the stabilizing sutures. The technique requires improved technical skill on the part of the surgeon because the heart is moving (contraction as well as respiratory movement). It also requires increased technical skill on the part of the anesthesiologist because an area of myocardium is ischemic, and non -functional, and prone to reperfusion arrythmias. The advantage of the operation is reduced cost (no extracorporeal circulation, reduced hospitalization time) and reduced risk of stroke (no extracorporeal circulation). If surgeons and anesthesiologists can surmount the technical challenges (motion, bleeding, arrythmias, hemodynamics, exposure) it offered great promise. On the down side, the operation was difficult and inferior wall vessels were hard to appoach.
Octopus and Starfish. These retractors use suction to stabilize the heart. Instead of squashing the heart with a foot like the CTS system, the Octopus system sucks up the myocardium with two little arms. The arms then separate slightly to tighten the area and reduce motion. The Starfish is retractor for lifting and moving the heart with a suction cup shaped like a Y. With these retractors hemodynamics are much improved during stabilization.
The equipment for MID-CABG is changing constantly. The fundamental problems have not. One of the first problems to address is what is the plan when the patient has ventricular fibrillation. If the surgical plan consists of a small thoracotomy what is going to happen when the ischemia caused by the stabilizing sutures or the reperfusion arrhythmias caused by releasing the sutures progresses to ventricular fibrillation? The second problem is maintaining venous return despite the efforts of the surgeon.
My favorite plan is this.
Choose an anesthetic that lowers the heart rate (fentanyl, sufentanyl, alfentanyl, remifentanyl).
Use a median sternotomy approach. The morbidity is small compared to the risk of prolonged ventricular fibrillation. Have the
perfusionist available. Don’t prime the pump but have it completely set up and ready to prime. Don't hand off the lines just be ready. If you can't convince the surgeon to do the case as a sternotomy from the start be ready for the emergency sternotomy when the patient fibrillates. The other advantage of the sternotomy from the start approach is multivessel CABG without extracorporeal circulation is possible. With the mini-thoracotomy multiple mini-thoracotomies are needed for the second and third distal anastamosis. If you end up doing a MID CABG with multiple mini-thoracotomies, consider using a double lumen tube for better exposure. They are not essential but frequently help.
3. Anti-coagulate the patient just as you would for a CABG with extracorporeal circulation (Heparin 300 U/kg). If there is a problem it is easy to cannulate and go on pump.
4. Prophylax for arrhythmias with you favorite drugs. Magnesium 2 gram IV plus Lidocaine 100 mg followed by an infusion at 2 mg/min. I am a strong proponent of amiodarone (IV). If you have arrythmias start amiodarone 150 MG over 10 minutes, then 1 mg/min IV for 6 hours, then 0.5 mg/min for 18 hours.
5. After the surgeon has retracted the heart, placed the stay sutures and the stabilizer, load the patient with volume (hespan / hextend) and maintain the pressure with vasoconstrictors. I try to avoid beta agonists because of the tachycardia and pro- arrythmic effects. Tachycardia makes the anastamosis more difficult. You will spend a lot of time adjusting hemodynamics only to have all your work reversed when the heart is let out of whatever position it is in. Steep trendellenburg is very useful for inferior wall distal anastamosis.
Adjust the ventilator to reduce motion (small tidal volumes with increased rate).
Have a plan to lower the heart rate even more if necessary (esmolol, adenosine). If the heart rate is irregular or too low use
atrial pacing. Do not use glycopyrolate or atropine when asked to increase the heart rate because they are hard to undo when the surgeon changes his mind.
8. Be ready for reperfusion arrythmias with release of the stay sutures.