The most efficient way to avoid brachial plexus injury appears to be the choice of sternal retractor using one that produces minimal chest wall asymmetry during internal mammary artery dissection, and to place the arms along the body, rotated inwards. I talked about this condition here some months ago. Thankfully, he eventually recovered fully. They didn't tell us anything about this type of problem, that is, until we pressed the cardiac doctors and cardiac nurses for information and pseudo-threatened to take legal action. It is usually unilateral, occurring mainly on the left side.
Axonal damage explains more prolonged phrenic nerve dysfunction after open-heart surgery.
Phrenic nerve injury after cardiac surgery is a serious complication that often leads to respiratory insufficiency and prolonged ventilator dependency. Thankfully, my father didn't require this type of intervention. He had enough absolutely horrible problems going on from adverse side effects from post-CABG drugs as it was. The time needed for the return of diaphragmatic function varies widely. Studies have shown variations of up to 27 months or longer.