LOS ANGELES—Just moments after successfully stopping his patient's heart at 10:30 p.m. Tuesday, bleary-eyed surgeon Dr. Dennis Kelly called it a night and decided to finish performing quadruple bypass surgery on Harold Cruz, 67, in the morning.

"Honestly, all these organs are looking the same to me right now," said Kelly, calling his mind "complete mush." "I need to take a nice long breather and come back to this with fresh eyes."

Kelly said that he knew it was time to put aside the surgery when he caught himself attempting to re-harvest the exact same femoral vein he had removed 20 minutes earlier.