All patients getting cardiac surgery using extracorporeal circulatory support should get an anti-fibrinolytic drug. There are several choices. It may be that all should get aprotinin, unless given in previous surgeries, but this change has not been universally adopted. At the present time we use a two tier approach.
All patients going on extracorporeal circulatory support should have an anti-fibrinolytic. If they are a first time case without risk factors they get amikar. If they are a redo case, a case with renal failure, a case with a high risk of bleeding, or a Jehovah’s Witness where bleeding would be lethal, they get aprotinin.
Amikar: Epsilon amino caproic acid used as a antifibrinolytic. Some evidence that it reduces post bypass bleeding. Some clinical reports of problems (left ventricular thrombus, arterial thrombi, etc.) Commonly given as 5 g IV prior to bypass and 5 g IV after bypass. Can be given in higher doses 10 g prior and 10 g after in large patients. Much less expensive ($12/bottle) than aprotinin ($900/bottle) although the efficacy is not proven. No FDA indication for this use. No convincing safety data. We are using it on all cases. Give 5 g IV slowly after you give the Heparin prior to bypass. Give 5 G IV slowly after the protamine is in. You do not want to give it prior to heparin. There are adverse events associated with protamine administration and it is easier if only one drug can be blamed for each event.
Aprotinin: Antifibrinolytic and platelet preserver that reduces bleeding and transfusion associated with CABG surgery in redos and people on aspirin. Costs $900/case. The transfusions for a case average $1000 so the cost is revenue neutral. If one considers the risk of disease transmission from transfusions amprotinin is a benefit. There is an increased risk of graft closure from clotting. If one looks at the morbidity and mortality associated with take backs for bleeding, aprotinin reduces risk of death. It is allergenic so patients should probably only have one use in a lifetime. That use should probably be for a redo CABG.
Our present use is for REDO CABG, patients with renal failure, patients with risk of bleeding, or patients in which bleeding would be lethal (Jehovah’s Witness). Order 6 M units (3 200cc bottles at 10,000 units per cc). Give 1 cc test dose, then 20 cc over 20 minutes starting prior to skin incision. Then continue at 0.5 M U/hr. The perfusionist will prime with 2 M units so give one bottle to them. I have tried to avoid using a fourth bottle in long cases by slowing the infusion to 0.3 to 0.4 M U/hr so that the infusion bottle will last until the end of bypass. Lower doses of aprotinin work, so this slower infusion is probably reasonable. Remember celite ACT 800 seconds, kaolin ACT 450 with Aprotinin.
What operation are we doing today?: Cardiac surgery used to be done using extracorporeal support. A few surgeons did CABG without the pump but it was rare and usually done elsewhere. In the last few years the percentage of CABG surgeries done using off pump techniques has risen dramatically. The invention of the octopus and starfish have made it easier, safer, and practical for most CABG operations to be done off pump. At the present time we are randomizing patients to “on pump” versus “off pump” care. If the decision seems random, you are correct, it is. The anesthetic care is fundamentally different for these two approaches so we will separately discuss the “ON PUMP” anesthetic care and then the “OFF PUMP” approach. You need to be flexible because they can change their mind at a moments notice.
Placing the cannulas:
Either check a twitch or give more non depolarizing neuromuscular blocker prior to cannula placement. If the patient takes a breath with the atrium open, they can have gas embolization and have severe injury.
Do not allow the surgeons to go on bypass without heparinization. The arterial pressure at this point should be below 120 mmHg. The small cannula in the aorta (has a red tape on it) should not have any bubbles in it. If you see a bubble tell the surgeons immediately. When they put in the aortic cannula there is splash - have your glasses on.
The larger cannula with blue tape is the venous cannula and goes into the apex of the right atrium into the inferior vena cava. It is a drain line and may have bubbles. On mitral valve and ASD/VSD cases there will be two smaller drain lines into the superior and inferior vena cava.
The small cannula with a balloon at one end is placed into the coronary sinus through a purse string in the right atrium. If this is used they will ask you to measure the pressure in the cannula. Hook this to the CVP transducer. When the flow in the coronary sinus cardioplegia line is 200 ml/min the pressure should be about 40 mmHg. If the pressure is like CVP and does not go up with coronary sinus flow (retrograde cardioplegia), the cannula is not in the coronary sinus. If this happens during continuous warm cardioplegia, there is a period of warm ischemia which can result in severe ventricular dysfunction and death. If the pressure is very high (greater than 100 mmHg) with a flow of 200 ml/min the cannula is against the wall and you also may not be having good retrograde cardioplegia.